JP7262054B2 - power converter - Google Patents

Description

The present invention relates to a power converter that converts DC power into DC power of another voltage.

With the spread and expansion of photovoltaic power generation systems and power storage systems, compact and highly efficient power conditioners are in demand. High-grade power conditioners and electric vehicles require DC/DC converters that are insulated, capable of bi-directional power transmission, and compatible with a wide range of voltages on both the primary and secondary sides. One DC/DC converter that meets these requirements is a DAB (Dual Active Bridge) converter (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2017-204998

In a conventional general DAB converter, when the reactor is charged from the DC power supply on the primary side, the reactor is also charged with energy from the DC load on the secondary side, generating a reactive current. Hard switching may also occur at light loads. A DAB converter that employs PFM (Pulse Frequency Modulation) control (see, for example, Patent Document 1) has also been proposed, but it sometimes generates loud noise when the frequency drops.

The present disclosure has been made in view of such circumstances, and an object thereof is to provide a low-noise, high-efficiency isolated DC/DC converter.

In order to solve the above problems, a power converter according to an aspect of the present disclosure includes a first leg in which a first switching element and a second switching element are connected in series, and a third switching element and a fourth switching element in series. a first bridge circuit in which the first leg and the second leg are connected in parallel to the first DC section; and a third bridge circuit in which a fifth switching element and a sixth switching element are connected in series. a second bridge circuit having a leg, a fourth leg in which a seventh switching element and an eighth switching element are connected in series, and in which the third leg and the fourth leg are connected in parallel to a second DC section; An isolation transformer connected between the first bridge circuit and the second bridge circuit, and a control circuit for controlling the first switching element to the eighth switching element. Diodes are connected or formed in anti-parallel to each of the first switching element and the eighth switching element, and when power is transmitted by stepping down from the first DC section to the second DC section, the first The one-bridge circuit includes a period during which the first DC section and the primary winding of the isolation transformer are electrically connected, and a period during which both ends of the primary winding of the isolation transformer are short-circuited within the first bridge circuit. The second bridge circuit includes a rectifying period. The control circuit variably controls the phase difference between the first leg and the second leg, variably controls simultaneous OFF periods of the fifth switching element and the sixth switching element, or variably controls the simultaneous OFF period of the fifth switching element and the sixth switching element. The simultaneous OFF period of the eighth switching element is variably controlled.

According to the present disclosure, it is possible to realize a low-noise, high-efficiency isolated DC/DC converter.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for demonstrating the structure of the power converter device which concerns on embodiment. FIGS. 2A to 2F are diagrams for explaining the operation of a comparative example (step-down mode) of the power converter. FIG. 10 is a diagram showing switching timings of a first switching element to a fourth switching element according to a comparative example (step-down mode); FIGS. 4A to 4F are diagrams for explaining the operation of a comparative example (boost mode) of the power converter. FIG. 10 is a diagram showing switching timings of a first switching element, a fourth switching element, a sixth switching element, and an eighth switching element according to a comparative example (boost mode); FIGS. 6A to 6F are diagrams for explaining the operation of the power converter according to the first embodiment (step-down mode). FIG. 10 is a diagram showing switching timing 1 of the first switching element to the eighth switching element according to Example 1 (step-down mode); FIG. 10 is a diagram showing switching timing 2 of the first switching element to the eighth switching element according to Example 1 (step-down mode); FIGS. 9A to 9D are diagrams for explaining operation 1 according to the second embodiment (step-down mode) of the power converter. FIGS. 10A to 10D are diagrams for explaining operation 2 according to the second embodiment (step-down mode) of the power converter. FIG. 10 is a diagram showing switching timings of a first switching element to an eighth switching element according to Example 2 (step-down mode); FIGS. 12(a) to 12(f) are diagrams for explaining the operation of the power converter according to the first embodiment (boost mode). FIG. 10 is a diagram showing switching timing 1 of the first switching element to the eighth switching element according to Example 1 (boost mode); FIG. 10 is a diagram showing switching timing 2 of the first switching element to the eighth switching element according to Example 1 (boost mode); 15(a) and 15(b) are diagrams showing specific examples of the current flowing through the reactor. FIGS. 16A to 16F are diagrams for explaining the operation of the second embodiment (boost mode) of the power converter. FIG. 10 is a diagram showing switching timings of a first switching element to an eighth switching element according to Example 2 (boost mode); FIG. 4 is a diagram for explaining switching between a step-down operation and a step-up operation according to the first and second embodiments of the power converter; FIG. 5 is a diagram for explaining the configuration of a power conversion device according to Modification 1; FIG. 10 is a diagram for explaining the configuration of a power conversion device according to Modification 2;

FIG. 1 is a diagram for explaining the configuration of a power conversion device 1 according to an embodiment. The power conversion device 1 is an insulated bidirectional DC/DC converter (DAB converter) that converts the DC power supplied from the first DC power supply E1 and transmits it to the second DC power supply E2, or the second DC power supply The DC power supplied from E2 is converted and transmitted to the first DC power source E1. The power converter 1 can step down the voltage for power transmission, or step up the voltage for power transmission.

The first DC power supply E1 corresponds to, for example, a storage battery, an electric double layer capacitor, or the like. A DC bus or the like to which a bidirectional inverter is connected corresponds to the second DC power supply E2. The AC side of the bi-directional inverter is connected to the commercial power grid and AC load for storage system applications. For electric vehicle applications, it is connected to a motor (with regenerative function). A DC/DC converter for solar cells and a DC/DC converter for other storage batteries may be further connected to the DC bus.

The power converter 1 includes a first capacitor C1, a first bridge circuit 11, an isolation transformer TR1, a first leakage inductance L1, a second leakage inductance L2, a second bridge circuit 12, a second capacitor C2, and a control circuit 13.

A first capacitor C1 is connected in parallel with the first DC power supply E1. A second capacitor C2 is connected in parallel with the second DC power supply E2. For example, electrolytic capacitors are used for the first capacitor C1 and the second capacitor C2. In this specification, the first DC power source E1 and the first capacitor C1 are collectively called a first DC section, and the second DC power source E2 and the second capacitor C2 are collectively called a second DC section.

In the first bridge circuit 11, a first leg in which a first switching element S1 and a second switching element S2 are connected in series and a second leg in which a third switching element S3 and a fourth switching element S4 are connected in series are connected in parallel. This is a full bridge circuit configured by The first bridge circuit 11 is connected in parallel with the first DC section, and the midpoint of the first leg and the midpoint of the second leg are respectively connected to both ends of the primary winding n1 of the isolation transformer TR1.

The second bridge circuit 12 has a third leg in which a fifth switching element S5 and a sixth switching element S6 are connected in series, and a fourth leg in which a seventh switching element S7 and an eighth switching element S8 are connected in series. This is a full bridge circuit configured by The second bridge circuit 12 is connected in parallel with the second DC section, and the middle point of the third leg and the middle point of the fourth leg are connected to both ends of the secondary winding n2 of the isolation transformer TR1.

A first diode D1 to an eighth diode D8 are connected or formed in anti-parallel to the first switching element S1 to the eighth switching element S8, respectively. For example, an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) can be used for the first switching element S1 to the eighth switching element S8. When IGBTs are used, external first diode D1-eighth diode D8 are connected to first switching element S1-eighth switching element S8, respectively. When MOSFETs are used, parasitic diodes formed from the source to the drain in each of the first switching element S1 to the eighth switching element S8 can be used as the first diode D1 to the eighth diode D8.

The isolation transformer TR1 converts the output voltage of the first bridge circuit 11 connected to the primary winding n1 according to the turns ratio between the primary winding n1 and the secondary winding n2, and is connected to the secondary winding n2. output to the second bridge circuit 12. Also, the isolation transformer TR1 converts the output voltage of the second bridge circuit 12 connected to the secondary winding n2 according to the turns ratio between the secondary winding n2 and the primary winding n1, and connects it to the primary winding n1. output to the first bridge circuit 11 where the

A first leakage inductance L1 is formed between the midpoint of the first leg of the first bridge circuit 11 and one end of the primary winding n1 of the isolation transformer TR1. A second leakage inductance L2 is formed between the third leg of the second bridge circuit 12 and one end of the secondary winding n2. Reactor elements having predetermined inductance values may be connected instead of the first leakage inductance L1 and the second leakage inductance L2.

Although not shown in FIG. 1, a first voltage sensor that detects the voltage across the first DC section, a first current sensor that detects the current flowing through the first DC section, and a second voltage sensor that detects the voltage across the second DC section. Two voltage sensors and a second current sensor that detects the current flowing through the second DC section are provided, and the respective measured values are output to the control circuit 13 .

The control circuit 13 supplies a driving signal (PWM (Pulse Width Modulation) signal) to the gate terminals of the first switching element S1 to the eighth switching element S8 to control the first switching element S1 to the eighth switching element S8. do. The configuration of the control circuit 13 can be realized by cooperation of hardware resources and software resources, or only by hardware resources. Analog devices, microcomputers, DSPs, ROMs, RAMs, FPGAs, and other LSIs can be used as hardware resources. Programs such as firmware can be used as software resources.

When power is transmitted from the first DC section to the second DC section, the control circuit 13 performs the first switching so that the output voltage to the second DC section maintains the voltage command value based on the measured value of the second voltage sensor. The element S1-controls the eighth switching element S8. Further, when power is transmitted from the first DC section to the second DC section, the control circuit 13 controls the output current to the second DC section to maintain the current command value based on the measured value of the second current sensor. 1 switching element S1 to control the eighth switching element S8. Further, when power is transmitted from the second DC section to the first DC section, the control circuit 13 controls the output voltage to the first DC section to maintain the voltage command value based on the measurement value of the first voltage sensor. 1 switching element S1 to control the eighth switching element S8. Further, when power is transmitted from the second DC section to the first DC section, the control circuit 13 controls the output current to the first DC section to maintain the current command value based on the measurement value of the first current sensor. 1 switching element S1 to control the eighth switching element S8.

Thus, the DAB converter has a symmetrical configuration on the primary side and the secondary side, and can transmit power in both directions. The operation of the power converter 1 will be described below.

(Comparative example (buck mode))
FIGS. 2(a) to 2(f) are diagrams for explaining the operation of a comparative example (step-down mode) of the power converter 1. FIG. In FIGS. 2(a) to 2(f), the insulating transformer TR1, the first leakage inductance L1, and the second leakage inductance L2 are collectively drawn as one reactor L for the sake of simplification of the drawing. Also, the first capacitor C1 and the second capacitor C2 are omitted from the drawing.

In the first state shown in FIG. 2A, the control circuit 13 turns on the first switching element S1 and the fourth switching element S4, and turns on the second switching element S2, the third switching element S3, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. Since the fifth switching element S5 to the eighth switching element S8 are all in the OFF state, the second bridge circuit 12 is a diode bridge circuit and functions as a rectifier circuit. In the first state, energy is discharged from the first DC power supply E1 to both the reactor L and the second DC power supply E2, and energy is charged to the reactor L and the second DC power supply E2.

In the second state shown in FIG. 2B and the third state shown in FIG. The third switching element S3, the fifth switching element S5 to the eighth switching element S8 are controlled to be turned off. In the second state and the third state, both ends of the primary winding n1 of the isolation transformer TR1 are short-circuited within the first bridge circuit 11, and the reactor L is electrically cut off from the first DC power supply E1. In the second state, energy is discharged from the reactor L to the second DC power supply E2, and energy is charged to the second DC power supply E2. Wait until the reactor current IL becomes 0 A in the second state. A third state shown in FIG. 2(c) indicates a state where the reactor current IL is 0A.

In the fourth state shown in FIG. 2(d), the control circuit 13 turns on the second switching element S2 and the third switching element S3, and turns on the first switching element S1, the fourth switching element S4, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. In the fourth state, energy is discharged from the first DC power supply E1 to both the reactor L and the second DC power supply E2, and energy is charged to the reactor L and the second DC power supply E2.

In the fifth state shown in FIG. 2E and the sixth state shown in FIG. The fourth switching element S4, the fifth switching element S5 to the eighth switching element S8 are controlled to be turned off. In the fifth and sixth states, both ends of the primary winding n1 of the isolation transformer TR1 are short-circuited within the first bridge circuit 11, and the reactor L is electrically cut off from the first DC power supply E1. In the fifth state, energy is discharged from the reactor L to the second DC power supply E2, and energy is charged to the second DC power supply E2. Wait until the reactor current IL becomes 0A in the fifth state. A sixth state shown in FIG. 2(f) indicates a state in which the reactor current IL is 0A.

In the comparative example (step-down mode), by repeating the above four switch patterns, the voltage is stepped down from the first DC power source E1 to the second DC power source E2 and power is transmitted. In the comparative example (step-down mode), the phase difference θ between the first leg (first switching element S1 and second switching element S2) and the second leg (third switching element S3 and fourth switching element S4) on the primary side is , to control the voltage or current of the power supplied from the first DC section to the second DC section. The duty ratio of the first switching element S1 to the fourth switching element S4 is fixed at 50%.

FIG. 3 is a diagram showing switching timings of the first switching element S1 to the fourth switching element S4 according to a comparative example (step-down mode). The first switching element S1 and the second switching element S2 operate complementarily. Similarly, the third switching element S3 and the fourth switching element S4 operate complementarily. A step-down rate is determined by a phase difference θ between the first switching element S1 and the second switching element S2 and the third switching element S3 and the fourth switching element S4.

(Comparative example (boost mode))
FIGS. 4A to 4F are diagrams for explaining the operation of a comparative example (boost mode) of the power converter 1. FIG.

In the first state shown in FIG. 4A, the control circuit 13 turns on the first switching element S1, the fourth switching element S4 and the sixth switching element S6, the second switching element S2, the third switching element S3, The fifth switching element S5, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the first state, both ends of the secondary winding n2 of the insulating transformer TR1 are short-circuited within the second bridge circuit 12, and the reactor L is electrically cut off from the second DC power supply E2. In the first state, energy is discharged from the first DC power supply E1 to the reactor L, and the reactor L is charged with energy.

In the second state shown in FIG. 4B, the control circuit 13 turns on the first switching element S1 and the fourth switching element S4, and turns on the second switching element S2, the third switching element S3, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. Since the fifth switching element S5 to the eighth switching element S8 are all in the OFF state, the second bridge circuit 12 is a diode bridge circuit and functions as a rectifier circuit. In the second state, energy is discharged from both the first DC power supply E1 and the reactor L to the second DC power supply E2, and the second DC power supply E2 is charged with energy. In the second state, wait until the reactor current IL reaches a set value near 0A.

In the third state shown in FIG. 4(c), the control circuit 13 turns on the fourth switching element S4, the first switching element S1, the second switching element S2, the third switching element S3, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. When the reactor current IL reaches the set value in the second state, a transition is made to the third state. In the third state, the direction of the reactor current IL is prevented from changing by turning on the fourth switching element S4.

In the fourth state shown in FIG. 4D, the control circuit 13 turns on the second switching element S2, the third switching element S3 and the eighth switching element S8, the first switching element S1, the fourth switching element S4, The fifth switching element S5, the sixth switching element S6 and the seventh switching element S7 are controlled to be turned off. In the fourth state, both ends of the secondary winding n2 of the isolation transformer TR1 are short-circuited within the second bridge circuit 12, and the reactor L is electrically cut off from the second DC power supply E2. In the fourth state, energy is discharged from the first DC power supply E1 to the reactor L, and the reactor L is charged with energy.

In the fifth state shown in FIG. 4(e), the control circuit 13 turns on the second switching element S2 and the third switching element S3, and turns on the first switching element S1, the fourth switching element 43, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. Since the fifth switching element S5 to the eighth switching element S8 are all in the OFF state, the second bridge circuit 12 is a diode bridge circuit and functions as a rectifier circuit. In the fifth state, energy is discharged from both the first DC power supply E1 and the reactor L to the second DC power supply E2, and the second DC power supply E2 is charged with energy. In the fifth state, wait until the reactor current IL reaches a set value set near 0A.

In the sixth state shown in FIG. 4(f), the control circuit 13 turns on the second switching element S2, the first switching element S1, the third switching element S3, the fourth switching element S4, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. When the reactor current IL reaches the set value in the fifth state, the state transitions to the sixth state. In the sixth state, the direction of the reactor current IL is prevented from changing by turning on the second switching element S2.

In the embodiment (boost mode), by repeating the above six switch patterns, the power is boosted from the first DC power source E1 to the second DC power source E2 and transmitted. In the comparative example (boost mode), the voltage or current of the power supplied from the first DC section to the second DC section is changed by the duty ratio (ON time) of the sixth switching element S6 and the eighth switching element S8 on the secondary side. Control. The duty ratio of the second switching element S2 and the fourth switching element S4 on the primary side is fixed at 50%.

FIG. 5 is a diagram showing switching timings of the first switching element S1 to the fourth switching element S4, the sixth switching element S6, and the eighth switching element S8 according to a comparative example (boost mode). The boost rate is determined by the ON time Ton of the sixth switching element S6 and the eighth switching element S8.

(Embodiment 1 (step-down mode))
FIGS. 6A to 6F are diagrams for explaining the operation of the power converter 1 according to the first embodiment (step-down mode).

In the first state shown in FIG. 6(a), the control circuit 13 turns on the first switching element S1 and the fourth switching element S4, and turns on the second switching element S2, the third switching element S3, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. Since the fifth switching element S5 to the eighth switching element S8 are all in the OFF state, the second bridge circuit 12 is a diode bridge circuit and functions as a rectifier circuit. In the first state, energy is discharged from the first DC power supply E1 to both the reactor L and the second DC power supply E2, and energy is charged to the reactor L and the second DC power supply E2.

In the second state shown in FIG. 6B, the control circuit 13 turns on the second switching element S2, the fourth switching element S4 and the eighth switching element S8, the first switching element S1, the third switching element S3, The fifth switching element S5, the sixth switching element S6 and the seventh switching element S7 are controlled to be turned off. In the second state, both ends of the primary winding n1 of the isolation transformer TR1 are short-circuited within the first bridge circuit 11, and the reactor L is electrically cut off from the first DC power supply E1. In the second state, energy is discharged from the reactor L to the second DC power supply E2, and energy is charged to the second DC power supply E2. The eighth switching element S8 is on for synchronous rectification. Synchronous rectification is effective when using MOSFETs as switching elements. Even if the eighth switching element S8 performs synchronous rectification, the direction of the reactor current IL is not reversed because the fifth switching element S5 is in the OFF state.

In the third state shown in FIG. 6C and the fourth state shown in FIG. The fourth switching element S4, the fifth switching element S5 to the eighth switching element S8 are controlled to be turned off. Since the fifth switching element S5 to the eighth switching element S8 are all in the OFF state, the second bridge circuit 12 is a diode bridge circuit and functions as a rectifier circuit. In the third state, energy is discharged from the reactor L to both the first DC power supply E1 and the second DC power supply E2, and energy is charged to the first DC power supply E1 and the second DC power supply E2. In the fourth state, energy is discharged from the first DC power supply E1 to both the reactor L and the second DC power supply E2, and energy is charged to the reactor L and the second DC power supply E2. Note that if the reactor current IL is 0 A before transitioning to the switch patterns shown in FIGS. Migrate directly.

In the fifth state shown in FIG. 6(e), the control circuit 13 turns on the first switching element S1, the third switching element S3, and the seventh switching element S7, the second switching element S2, the fourth switching element S4, The fifth switching element S5, the sixth switching element S6 and the eighth switching element S8 are controlled to be turned off. In the fifth state, both ends of the primary winding n1 of the isolation transformer TR1 are short-circuited within the first bridge circuit 11, and the reactor L is electrically cut off from the first DC power supply E1. In the fifth state, energy is discharged from the reactor L to the second DC power supply E2, and energy is charged to the second DC power supply E2. The seventh switching element S7 is on for synchronous rectification. Even if the seventh switching element S7 performs synchronous rectification, the direction of the reactor current IL is not reversed because the sixth switching element S6 is in the OFF state.

In the sixth state shown in FIG. 6(f) and the first state shown in FIG. 6(a), the control circuit 13 turns on the first switching element S1 and the fourth switching element S4, turns the second switching element S2 The third switching element S3, the fifth switching element S5 to the eighth switching element S8 are controlled to be turned off. Since the fifth switching element S5 to the eighth switching element S8 are all in the OFF state, the second bridge circuit 12 is a diode bridge circuit and functions as a rectifier circuit. In the sixth state, energy is discharged from the reactor L to both the first DC power supply E1 and the second DC power supply E2, and energy is charged to the first DC power supply E1 and the second DC power supply E2. Note that if the reactor current IL is 0 A before transitioning to the switch patterns shown in FIGS. Migrate directly.

In Example 1 (step-down mode), by repeating the above four switch patterns, the voltage is stepped down from the first DC power source E1 to the second DC power source E2 and power is transmitted. In the first embodiment (step-down mode), the phase difference θ between the first leg (first switching element S1 and second switching element S2) and the second leg (third switching element S3 and fourth switching element S4) on the primary side is controls the voltage or current of power supplied from the first DC section to the second DC section. The duty ratio of the first switching element S1 to the fourth switching element S4 is fixed at 50%.

FIG. 7 is a diagram showing switching timing 1 of the first switching element S1 to the eighth switching element S8 according to the first embodiment (step-down mode). Thin lines indicate the ON/OFF states of the first switching element S1, the fourth switching element S4, the fifth switching element S5 and the eighth switching element S8, and the thick lines indicate the second switching element S2, the third switching element S3 and the sixth switching element. The ON/OFF states of the element S6 and the seventh switching element S7 are shown.

The first switching element S1 and the second switching element S2 operate complementarily. A dead time is inserted at the timing when both are switched on/off. The dead time is the time inserted to prevent both ends of the first DC power source E1 from being short-circuited due to the first switching element S1 and the second switching element S2 being simultaneously turned on. Similarly, the third switching element S3 and the fourth switching element S4 operate complementarily. A dead time is inserted at the timing when both are switched on/off. A step-down rate is determined by a phase difference θ between the first switching element S1 and the second switching element S2 and the fourth switching element S4 and the third switching element S3.

In the examples shown in FIGS. 6(a) to (f) and FIG. 7, the eighth switching element S8 is controlled to be ON in state 2(b). In this regard, the fifth switching element S5 may be controlled to be ON in state 2(b). Similarly, in state 5(e), the seventh switching element S7 is controlled to be on. In this regard, the sixth switching element S6 may be controlled to be ON in state 5(e).

FIG. 8 is a diagram showing switching timings 2 of the first switching element S1 to the eighth switching element S8 according to the first embodiment (step-down mode). In the examples shown in FIGS. 6(a) to 6(f) and FIG. 7, an example of stepping down the voltage from the first DC section and supplying power to the second DC section has been described. In this regard, it is also possible to step down the voltage from the second DC section to the first DC section and supply power. In this case, as shown in FIG. 8, the control circuit 13 generates a drive signal to be supplied to the first switching element S1 to the fourth switching element S4 and a drive signal to be supplied to the fifth switching element S5 to the eighth switching element S8. should be replaced.

As described above, according to the first embodiment (step-down mode), a state in which power is transmitted from the second DC power supply E2 to the reactor L does not occur, so reactive power can be suppressed, and conversion efficiency can be improved. can be done. Also, synchronous rectification on the secondary side in states 2(b) and 5(e) can reduce diode conduction losses. By using one switching element for synchronous rectification in state 2(b) and state 5(e), loss can be reduced while preventing the direction of reactor current IL from reversing. As a result, the occurrence of hard switching can also be prevented. Also, by providing a short-circuit mode on the primary side, power regulation by phase shift is possible.

After the state 2(b), it is also possible to control the sixth switching element S6 to the ON state to short-circuit the secondary side in the second bridge circuit 12 with the sixth switching element S6 and the eighth switching element S8. be done. However, the moment the sixth switching element S6 is turned on, the voltage across the fifth diode D5 is reversed and a recovery current is generated. As a result, the fifth diode D5 and the sixth switching element S6 are electrically connected to momentarily short-circuit the second DC power source E2. On the other hand, in Example 1 (step-down mode), there is no mode in which a recovery current is generated, and the occurrence of recovery loss can be prevented.

(Embodiment 2 (step-down mode))
FIGS. 9A to 9D are diagrams for explaining the operation 1 according to the second embodiment (step-down mode) of the power converter 1. FIG. FIGS. 10A to 10D are diagrams for explaining operation 2 according to the second embodiment (step-down mode) of the power converter 1. FIG. Example 2 (step-down mode) is an example of finer state transitions based on Example 1 (step-down mode).

In the first state shown in FIG. 9A, the control circuit 13 turns on the first switching element S1 and the fourth switching element S4, switches the second switching element S2, the third switching element S3, the fifth switching element S5, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the first state, energy is discharged from the first DC power supply E1 to both the reactor L and the second DC power supply E2, and energy is charged to the reactor L and the second DC power supply E2. This state is the same as the first state of the first embodiment (step-down mode) shown in FIG.

In the second state shown in FIG. 9B, the control circuit 13 turns on the fourth switching element S4, the first switching element S1, the second switching element S2, the third switching element S3, the fifth switching element S5, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the second state, both ends of the primary winding n1 of the isolation transformer TR1 are short-circuited within the first bridge circuit 11, and the reactor L is electrically cut off from the first DC power supply E1. In the second state, energy is discharged from the reactor L to the second DC power supply E2, and energy is charged to the second DC power supply E2.

In the third state shown in FIG. 9C, the control circuit 13 turns on the second switching element S2, the fourth switching element S4 and the eighth switching element S8, the first switching element S1, the third switching element S3, The fifth switching element S5, the sixth switching element S6 and the seventh switching element S7 are controlled to be turned off. Also in the third state, both ends of the primary winding n1 of the isolation transformer TR1 are short-circuited within the first bridge circuit 11, and the reactor L is electrically cut off from the first DC power supply E1. Also in the third state, energy is discharged from the reactor L to the second DC power supply E2, and energy is charged in the second DC power supply E2. The eighth switching element S8 is on for synchronous rectification. This is the same state as the second state of the first embodiment (step-down mode) shown in FIG. 6(b).

In the fourth state shown in FIG. 9D, the control circuit 13 turns on the second switching element S2, the first switching element S1, the third switching element S3, the fourth switching element S4, the fifth switching element S5, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the fourth state, energy is discharged from the reactor L to both the first DC power supply E1 and the second DC power supply E2, and energy is charged to the first DC power supply E1 and the second DC power supply E2.

In the fifth state shown in FIG. 10A, the control circuit 13 turns on the second switching element S2 and the third switching element S3, turns on the first switching element S1, the fourth switching element S4, the fifth switching element S5, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the fifth state, energy is discharged from the first DC power supply E1 to both the reactor L and the second DC power supply E2, and energy is charged to the reactor L and the second DC power supply E2. This is the same state as the fourth state of the first embodiment (step-down mode) shown in FIG. 6(d).

In the sixth state shown in FIG. 10(b), the control circuit 13 turns on the third switching element S3, the first switching element S1, the second switching element S2, the fourth switching element S4, the fifth switching element S5, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the sixth state, both ends of the primary winding n1 of the isolation transformer TR1 are short-circuited within the first bridge circuit 11, and the reactor L is electrically cut off from the first DC power supply E1. In the sixth state, energy is discharged from the reactor L to the second DC power supply E2, and energy is charged to the second DC power supply E2.

In the seventh state shown in FIG. 10(c), the control circuit 13 turns on the first switching element S1, the third switching element S3, and the seventh switching element S7, the second switching element S2, the fourth switching element S4, The fifth switching element S5, the sixth switching element S6 and the eighth switching element S8 are controlled to be turned off. Also in the seventh state, both ends of the primary winding n1 of the isolation transformer TR1 are short-circuited within the first bridge circuit 11, and the reactor L is electrically cut off from the first DC power supply E1. Even in the seventh state, energy is discharged from the reactor L to the second DC power supply E2, and energy is charged in the second DC power supply E2. The seventh switching element S7 is on for synchronous rectification. This is the same state as the fifth state of the first embodiment (step-down mode) shown in FIG. 6(e).

In the eighth state shown in FIG. 10(d), the control circuit 13 turns the first switching element S1 on, the second switching element S2, the third switching element S3, the fourth switching element S4, the fifth switching element S5, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the eighth state, energy is discharged from the reactor L to both the first DC power supply E1 and the second DC power supply E2, and energy is charged to the first DC power supply E1 and the second DC power supply E2.

In the second embodiment (step-down mode), by repeating the above eight switch patterns, the voltage is stepped down from the first DC power source E1 to the second DC power source E2 and power is transmitted. In the second embodiment (step-down mode), the voltage or current of power supplied from the first DC section to the second DC section is controlled by the phase difference θ between the first leg and the second leg on the primary side. The duty ratio of the first switching element S1 to the fourth switching element S4 is fixed at 50%. Note that this 50% is a value that does not consider dead time.

FIG. 11 is a diagram showing switching timings of the first switching element S1 to the eighth switching element S8 according to the second embodiment (step-down mode). Thin lines indicate the ON/OFF states of the first switching element S1, the fourth switching element S4, the fifth switching element S5 and the eighth switching element S8, and the thick lines indicate the second switching element S2, the third switching element S3 and the sixth switching element. The ON/OFF states of the element S6 and the seventh switching element S7 are shown.

The first switching element S1 and the second switching element S2 operate complementarily. A dead time is inserted at the timing when both are switched on/off. Similarly, the third switching element S3 and the fourth switching element S4 operate complementarily. A dead time is inserted at the timing when both are switched on/off. A step-down rate is determined by a phase difference θ between the first switching element S1 and the second switching element S2 and the fourth switching element S4 and the third switching element S3.

The on-time of the eighth switching element S8 and the seventh switching element S7 is controlled to the same amount as the shift amount corresponding to the phase difference θ, or to the amount obtained by subtracting the shift amount corresponding to the dead time from the shift amount corresponding to the phase difference θ. be done. The rise phases of the eighth switching element S8 and the seventh switching element S7 are fixed, and the fall phases thereof are variable.

The rising phase of the eighth switching element S8 is controlled to synchronize with the rising phase of the second switching element S2 or the falling phase of the first switching element S1. That is, the eighth switching element S8 is turned on at the same time as the second switching element S2 is turned on or the first switching element S1 is turned off. The rising phase of the seventh switching element S7 is controlled to synchronize with the rising phase of the first switching element S1 or the falling phase of the second switching element S2. That is, the seventh switching element S7 is turned on at the same time as the first switching element S1 is turned on or the second switching element S2 is turned off.

The falling phase of the eighth switching element S8 is controlled to synchronize with the falling phase of the fourth switching element S4 or the rising phase of the third switching element S3. That is, the eighth switching element S8 is turned off at the same time as the fourth switching element S4 is turned off or the third switching element S3 is turned on. The falling phase of the seventh switching element S7 is controlled to synchronize with the falling phase of the third switching element S3 or the rising phase of the fourth switching element S4. That is, the seventh switching element S7 is turned off at the same time when the third switching element S3 is turned off or the fourth switching element S4 is turned on.

By controlling the eighth switching element S8 and the seventh switching element S7 to be ON only in the section corresponding to the phase difference θ between the first leg and the second leg on the primary side, synchronization is achieved while suppressing the occurrence of recovery loss. can be rectified.

The phase difference θ between the first leg and the second leg on the primary side is operated in the range of 0 to 180°. As the phase difference θ becomes smaller, the amount of power to be transmitted can be increased. When the dead time is fixed, the minimum value of the phase difference θ can be set to 0, thereby suppressing the loss when the frequency is increased.

In the second embodiment (step-down mode), similarly to the first embodiment (step-down mode), the control of the fifth switching element S5 and the control of the eighth switching element S8 are exchanged, and the control of the sixth switching element S6 and the control of the seventh switching element are switched. The control of S7 may be exchanged. Also in Example 2 (step-down mode), by exchanging the drive signal supplied to the first switching element S1 to the fourth switching element S4 and the drive signal supplied to the fifth switching element S5 to the eighth switching element S8, It is possible to step down and supply power from the second DC section to the first DC section.

As described above, according to the second embodiment (step-down mode), the same effects as those of the first embodiment (step-down mode) can be obtained. More efficient control can be achieved by controlling more finely than in the first embodiment (step-down mode).

(Embodiment 1 (boost mode))
FIGS. 12(a) to 12(f) are diagrams for explaining the operation of the power converter 1 according to the first embodiment (boost mode).

In the first state shown in FIG. 12(a), the control circuit 13 turns on the first switching element S1, the fourth switching element S4, and the sixth switching element S6, the second switching element S2, the third switching element S3, The fifth switching element S5, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the first state, both ends of the secondary winding n2 of the insulating transformer TR1 are short-circuited within the second bridge circuit 12, and the reactor L is electrically cut off from the second DC power supply E2. In the first state, energy is discharged from the first DC power supply E1 to the reactor L, and the reactor L is charged with energy.

In the second state shown in FIG. 12(b), the control circuit 13 turns on the first switching element S1 and the fourth switching element S4, and turns on the second switching element S2, the third switching element S3, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. Since the fifth switching element S5 to the eighth switching element S8 are all in the OFF state, the second bridge circuit 12 is a diode bridge circuit and functions as a rectifier circuit. In the second state, energy is discharged from both the first DC power supply E1 and the reactor L to the second DC power supply E2, and the second DC power supply E2 is charged with energy.

In the third state shown in FIG. 12(c) and the fourth state shown in FIG. 12(d), the control circuit 13 turns on the second switching element S2, the third switching element S3 and the fifth switching element S5. The first switching element S1, the fourth switching element S4, the sixth switching element S6, the seventh switching element S7, and the eighth switching element S8 are controlled to be turned off. In the third state, energy is discharged from the reactor L to both the first DC power supply E1 and the second DC power supply E2, and energy is charged to the first DC power supply E1 and the second DC power supply E2. In the fourth state, energy is discharged from the first DC power supply E1 to the reactor L, and the reactor L is charged with energy. In the fourth state, both ends of the secondary winding n2 of the isolation transformer TR1 are short-circuited within the second bridge circuit 12, and the reactor L is electrically cut off from the second DC power supply E2. Note that if the reactor current IL is 0 A before transitioning to the switch patterns shown in FIGS. Migrate directly.

In the fifth state shown in FIG. 12(e), the control circuit 13 turns on the second switching element S2 and the third switching element S3, and turns on the first switching element S1, the fourth switching element S4, and the fifth switching element S5-. The eighth switching element S8 is controlled to be turned off. Since the fifth switching element S5 to the eighth switching element S8 are all in the OFF state, the second bridge circuit 12 is a diode bridge circuit and functions as a rectifier circuit. In the fifth state, energy is discharged from both the first DC power supply E1 and the reactor L to the second DC power supply E2, and the second DC power supply E2 is charged with energy.

In the sixth state shown in FIG. 12(f) and the first state shown in FIG. 12(a), the control circuit 13 turns on the first switching element S1, the fourth switching element S4, and the sixth switching element S6. The second switching element S2, the third switching element S3, the fifth switching element S5, the seventh switching element S7, and the eighth switching element S8 are controlled to be turned off. In the sixth state, energy is discharged from the reactor L to both the first DC power supply E1 and the second DC power supply E2, and energy is charged to the first DC power supply E1 and the second DC power supply E2. Note that if the reactor current IL is 0 A before transitioning to the switch patterns shown in FIGS. Migrate directly.

In the first embodiment (boost mode), the four switch patterns described above are repeated to boost the voltage from the first DC power source E1 to the second DC power source E2 and transmit electric power. In Embodiment 1 (boost mode), the voltage or current of the power supplied from the first DC section to the second DC section is determined by the duty ratio (on time) of the fifth switching element S5 and the sixth switching element S6 on the secondary side. to control. The duty ratio of the first switching element S1 to the fourth switching element S4 on the primary side is fixed at 50%. The phase difference θ between the first leg (the first switching element S1 and the second switching element S2) and the second leg (the third switching element S3 and the fourth switching element S4) on the primary side is 0 or less than the dead time. It is fixed with a phase difference.

FIG. 13 is a diagram showing switching timing 1 of the first switching element S1 to the eighth switching element S8 according to the first embodiment (boost mode). The first switching element S1 and the second switching element S2 operate complementarily. A dead time is inserted at the timing when both are switched on/off. Similarly, the third switching element S3 and the fourth switching element S4 operate complementarily. A dead time is inserted at the timing when both are switched on/off. The boost rate is determined by the ON time Ton of the fifth switching element S5 and the sixth switching element S6. The seventh switching element S7 and the eighth switching element S8 are always controlled to be off.

In the examples shown in FIGS. 12(a)-(f) and FIG. 13, the sixth switching element S6 is controlled to be in the ON state in state 6(f) and state 1(a). In this regard, the seventh switching element S7 may be controlled to be turned on in state 6(f) and state 1(a). Similarly, the fifth switching element S5 is controlled to be in the ON state in states 3(c) and 4(d). In this regard, the eighth switching element S8 may be controlled to be turned on in states 3(c) and 4(d).

FIG. 14 is a diagram showing switching timing 2 of the first switching element S1 to the eighth switching element S8 according to the first embodiment (boost mode). In the examples shown in FIGS. 12(a) to 12(f) and FIG. 13, an example of supplying electric power after increasing the voltage from the first DC section to the second DC section has been described. In this respect, it is also possible to boost power from the second DC section to the first DC section and supply power. In this case, as shown in FIG. 14, the control circuit 13 generates a drive signal to be supplied to the first switching element S1 to the fourth switching element S4 and a drive signal to be supplied to the fifth switching element S5 to the eighth switching element S8. should be replaced.

As described above, according to the first embodiment (boost mode), a state in which power is transmitted from the second DC power supply E2 to the reactor L does not occur, so reactive power can be suppressed, and conversion efficiency can be improved. can be done. By providing a mode in which the secondary side is short-circuited when energy is charged to the reactor L, it is possible to prevent power from being transmitted from the second DC power supply E2 to the reactor L, thereby reducing conduction loss due to reactive current. can do.

When short-circuiting the second bridge circuit 12 on the secondary side, the upper side (fifth switching element S5 and seventh switching element S7) and the lower side (sixth switching element S6 and eighth switching element S8) are alternately used. As a result, heat can be prevented from concentrating on the upper side or the lower side, and the heat can be dispersed. Thereby, the heat resistance design of the upper side and the lower side can be made uniform. On the other hand, in the comparative example (boost mode) shown in FIGS. 4A to 4F, the lower side of the second bridge circuit 12 is It is short-circuited and heat is concentrated on the lower side.

15A and 15B are diagrams showing specific examples of the current IL flowing through the reactor L. FIG. FIG. 15(a) is an example when the reactor current IL is small. In this case, the switch pattern switching timing is the same between the comparative example and the first embodiment. In either case, the switch pattern switches when the reactor current IL is 0A.

FIG. 15(b) is an example when the reactor current IL is large. In this case, the switch pattern switching timing differs between the comparative example and the first embodiment. In the first embodiment, the times of the second switch pattern and the fourth switch pattern for discharging the reactor L are fixed, and the third switch pattern and the fourth switch pattern for charging the reactor L are set at the set fixed timing. 1 switch pattern. On the other hand, in the comparative example, before switching to the third switch pattern and the first switch pattern, it waits until the reactor current IL becomes 0 A as indicated by the dotted line. In the comparative example, basically, control is performed to switch between the third switch pattern and the first switch pattern when the reactor current IL is 0A. Thereby, the power transmission direction can be switched at high speed. In addition, generation of reactive current can be suppressed.

However, in the comparative example, since the control is to wait until the reactor current IL becomes 0A, the PFM control is performed. With PFM control, the frequency may drop into the audible range, in which case loud noise is generated.

Also, in PFM control, the frequency may increase when the reactor current IL is small. Switching losses increase as the frequency increases. As a countermeasure against this, in a comparative example (boost mode), the fourth switching element S4 is controlled to be turned on in the third state shown in FIG. By controlling the switching element S2 to the ON state, the direction of the reactor current IL is prevented from changing. This prevents the reactor current IL from chattering across 0 A and prevents the frequency from rising. However, chattering may occur depending on the measurement error of the current sensor.

On the other hand, in Embodiment 1, since the PWM control is performed, the frequency is fixed, and large noise is not generated. Also, in the first embodiment, the current sensor for measuring the reactor current IL is not essential and can be omitted.

(Embodiment 2 (boost mode))
FIGS. 16A to 16F are diagrams for explaining the operation of the second embodiment (boost mode) of the power converter 1. FIG. Example 2 (boost mode) is an example of finer state transition based on Example 1 (boost mode).

In the first state shown in FIG. 16(a), the control circuit 13 turns on the first switching element S1, the fourth switching element S4, and the sixth switching element S6, the second switching element S2, the third switching element S3, The fifth switching element S5, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the first state, both ends of the secondary winding n2 of the insulating transformer TR1 are short-circuited within the second bridge circuit 12, and the reactor L is electrically cut off from the second DC power supply E2. In the first state, energy is discharged from the first DC power supply E1 to the reactor L, and the reactor L is charged with energy. This is the same state as the first state of the first embodiment (booster mode) shown in FIG. 12(a).

In the second state shown in FIG. 16(b), the control circuit 13 turns on the first switching element S1 and the fourth switching element S4, switches the second switching element S2, the third switching element S3, the fifth switching element S5, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the second state, energy is discharged from both the first DC power supply E1 and the reactor L to the second DC power supply E2, and the second DC power supply E2 is charged with energy. This is the same state as the second state of the first embodiment (booster mode) shown in FIG. 12(b).

In the third state shown in FIG. 16(c), the control circuit 13 turns on the fifth switching element S5, the first switching element S1, the second switching element S2, the third switching element S3, the fourth switching element S4, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the third state, energy is discharged from the reactor L to both the first DC power supply E1 and the second DC power supply E2, and energy is charged to the first DC power supply E1 and the second DC power supply E2.

In the fourth state shown in FIG. 16(d), the control circuit 13 turns on the second switching element S2, the third switching element S3, and the fifth switching element S5, the first switching element S1, the fourth switching element S4, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the fourth state, both ends of the secondary winding n2 of the isolation transformer TR1 are short-circuited within the second bridge circuit 12, and the reactor L is electrically cut off from the second DC power supply E2. In the fourth state, energy is discharged from the first DC power supply E1 to the reactor L, and the reactor L is charged with energy. This is the same state as the fourth state of the first embodiment (booster mode) shown in FIG. 12(d).

In the fifth state shown in FIG. 16(e), the control circuit 13 turns on the second switching element S2 and the third switching element S3, turns on the first switching element S1, the fourth switching element S4, the fifth switching element S5, The sixth switching element S6, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the fifth state, energy is discharged from both the first DC power supply E1 and the reactor L to the second DC power supply E2, and the second DC power supply E2 is charged with energy. This is the same state as the fifth state of the first embodiment (booster mode) shown in FIG. 12(e).

In the sixth state shown in FIG. 16(f), the control circuit 13 turns on the sixth switching element S6, the first switching element S1, the second switching element S2, the third switching element S3, the fourth switching element S4, The fifth switching element S5, the seventh switching element S7 and the eighth switching element S8 are controlled to be turned off. In the sixth state, energy is discharged from the reactor L to both the first DC power supply E1 and the second DC power supply E2, and energy is charged to the first DC power supply E1 and the second DC power supply E2.

In the second embodiment (boost mode), the six switch patterns described above are repeated to boost the voltage from the first DC power source E1 to the second DC power source E2 and transmit electric power. In Example 2 (boost mode), the voltage or current of the power supplied from the first DC section to the second DC section is determined by the duty ratio (ON time) of the fifth switching element S5 and the sixth switching element S6 on the secondary side. to control. The duty ratio of the first switching element S1 to the fourth switching element S4 on the primary side is fixed at 50%. Note that this 50% is a value that does not consider dead time. A phase difference θ between the first leg and the second leg on the primary side is fixed at zero.

FIG. 17 is a diagram showing switching timings of the first switching element S1 to the eighth switching element S8 according to the second embodiment (boost mode). Thin lines indicate the ON/OFF states of the first switching element S1, the fourth switching element S4, the fifth switching element S5 and the eighth switching element S8, and the thick lines indicate the second switching element S2, the third switching element S3 and the sixth switching element. The ON/OFF states of the element S6 and the seventh switching element S7 are shown.

The first switching element S1 and the second switching element S2 operate complementarily. A dead time is inserted at the timing when both are switched on/off. Similarly, the third switching element S3 and the fourth switching element S4 operate complementarily. A dead time is inserted at the timing when both are switched on/off. The boost rate is determined by the ON time Ton of the fifth switching element S5 and the sixth switching element S6.

The on-time Ton of the fifth switching element S5 and the sixth switching element S6 is controlled by duty. The rise phases of the fifth switching element S5 and the sixth switching element S6 are fixed, and the fall phases thereof are variable.

The rising phase of the fifth switching element S5 is controlled so as to synchronize with the falling phase of the first switching element S1. That is, the fifth switching element S5 is turned on at the same time as the first switching element S1 is turned off. The rising phase of the sixth switching element S6 is controlled so as to synchronize with the falling phase of the second switching element S2. That is, the sixth switching element S6 is turned on at the same time as the second switching element S2 is turned off. This makes it easier for the fifth switching element S5 or the sixth switching element S6 to operate (Zero Voltage Switching).

The amount of power to be transmitted is controlled by the on-time Ton of the fifth switching element S5 and the sixth switching element S6. As the ON time Ton is lengthened, the amount of power to be transmitted can be increased. When the dead time is fixed, the loss when the frequency is increased can be suppressed by setting the phase difference θ between the first leg and the second leg on the primary side to 0.

In Example 2 (boost mode), as in Example 1 (boost mode), the control of the fifth switching element S5 and the control of the eighth switching element S8 are interchanged, and the control of the sixth switching element S6 and the control of the seventh switching element are switched. The control of S7 may be exchanged. Also in Example 2 (boost mode), by exchanging the drive signal supplied to the first switching element S1 to the fourth switching element S4 and the drive signal supplied to the fifth switching element S5 to the eighth switching element S8, It is possible to boost power from the second DC section to the first DC section.

As described above, according to the second embodiment (boost mode), the same effects as those of the first embodiment (boost mode) can be obtained. More efficient control can be achieved by controlling more finely than in the first embodiment (boost mode).

FIG. 18 is a diagram for explaining switching between the step-down operation and the step-up operation according to the first and second embodiments of the power conversion device 1. FIG. When power is transmitted from the first DC section to the second DC section, the control circuit 13 switches between a step-down mode and a step-up mode based on the voltage of the first DC section and the voltage of the second DC section. The control circuit 13 selects the step-down mode when the voltage of the second DC section is lower than the voltage of the first DC section, and selects the step-down mode when the voltage of the second DC section is higher than the voltage of the first DC section. select boost mode. Further, when power is transmitted from the second DC section to the first DC section, the control circuit 13 switches between the step-down mode and the step-up mode based on the voltage of the second DC section and the voltage of the first DC section. The control circuit 13 selects the step-down mode when the voltage of the first DC section is lower than the voltage of the second DC section, and selects the step-down mode when the voltage of the first DC section is higher than the voltage of the second DC section. select boost mode. Note that the control circuit 13 may switch between the step-down mode and the step-up mode based on the direction of the current flowing through the first DC section, the direction of the current flowing through the second DC section, or the direction of the reactor current IL.

As shown in FIG. 18, in the step-down operation, the ON time Ton of the fifth switching element S5 and the sixth switching element S6 on the secondary side is fixed to be equal to or less than the dead time Td (may be 0). Manipulate the phase difference θ between the second legs. In the boosting operation, the phase difference θ between the first leg and the second leg on the primary side is fixed to be equal to or less than the dead time Td (may be 0), and the fifth switching element S5 and the sixth switching element S6 on the secondary side are turned on. Manipulate time Ton.

Both the maximum value of the phase difference θ and the maximum value of the on-time Ton are half the period (Ts/2). Since the phase difference θ and on-time Ton at maximum power output in step-down operation and the phase difference θ and on-time Ton at minimum power output in step-up operation are the same, seamless switching between step-down operation and step-up operation is possible. becomes.

As described above, according to the first and second embodiments, by combining the above-described step-down mode and step-up mode, a single DC/DC converter can perform step-down operation and step-up operation, and bi-directional power transmission is also possible. be. Therefore, both the primary side and the secondary side can support a wide voltage range.

The present disclosure has been described above based on the embodiments. It is to be understood by those skilled in the art that the embodiment is an example, and that various modifications are possible in the combination of each component and each treatment process, and such modifications are also within the scope of the present disclosure. .

In the first embodiment (step-down mode) described above, as shown in FIGS. , synchronous rectification was performed by controlling the seventh switching element S7 to be in the ON state. In this regard, synchronous rectification in states 2(b) and 5(e) may be omitted. That is, in states 2(b) and 5(e), the fifth to eighth switching elements S5 to S8 on the secondary side may all be turned off.

In the first embodiment (boost mode) described above, in states 2(b) and 5(e) as shown in FIGS. All the elements S8 were controlled to be in the OFF state. In this regard, synchronous rectification may be performed by controlling the eighth switching element S8 or the fifth switching element S5 to the ON state in state 2(b). Also, in state 5(e), synchronous rectification may be performed by controlling the seventh switching element S7 or the sixth switching element S6 to the ON state. Synchronous rectification can reduce diode conduction losses.

FIG. 19 is a diagram for explaining the configuration of the power converter 1 according to Modification 1. As shown in FIG. A power conversion device 1 according to Modification 1 is an insulated unidirectional DC/DC converter. It can be used in applications where the secondary side load R2 does not charge the primary side first DC power supply E1. In the power conversion device 1 according to Modification 1, the second bridge circuit 12 includes four bridge-connected diode elements (fifth diode D5-eighth diode D8 ).

In the step-down mode shown in FIGS. 6(a)-(f) and FIG. A step-down operation is possible only by controlling the element S4. According to Modification 1, the cost of the second bridge circuit 12 can be reduced.

FIG. 20 is a diagram for explaining the configuration of the power converter 1 according to Modification 2. As shown in FIG. The power converter 1 according to Modification 2 is an insulated unidirectional DC/DC converter. It can be used in applications where the secondary side load R2 does not charge the primary side first DC power source E1. In the power converter 1 according to Modification 2, the second bridge circuit 12 uses two diode elements (seventh diode D7 and eighth diode D8) instead of the seventh switching element S7 and the eighth switching element S8. be.

Since the seventh switching element S7 and the eighth switching element S8 are always off in the boost mode shown in FIGS. Boosting operation is possible with the same control as In the step-down mode shown in FIGS. 6(a)-(f) and FIG. By using and synchronously rectifying, even the power conversion device 1 according to the second modification can perform the step-down operation with the same control as the first embodiment. According to Modification 2, the cost of the second bridge circuit 12 can be reduced. In addition, both step-up operation and step-down operation are possible.

Note that the embodiment may be specified by the following items.

[Item 1]
It has a first leg in which a first switching element (S1) and a second switching element (S2) are connected in series, and a second leg in which a third switching element (S3) and a fourth switching element (S4) are connected in series. and a first bridge circuit (11) in which the first leg and the second leg are connected in parallel to a first DC section (E1, C1);
It has a third leg in which a fifth switching element (S5) and a sixth switching element (S6) are connected in series, and a fourth leg in which a seventh switching element (S7) and an eighth switching element (S8) are connected in series. and a second bridge circuit (12) in which the third leg and the fourth leg are connected in parallel to a second DC section (C2, E2);
an isolation transformer (TR1) connected between the first bridge circuit (11) and the second bridge circuit (12);
A control circuit (13) that controls the first switching element (S1)-the eighth switching element (S8),
Diodes (D1-D8) are connected or formed in antiparallel to each of the first switching element (S1) to the eighth switching element (S8),
When stepping down the voltage from the first DC section (E1, C1) to the second DC section (C2, E2) to transmit power,
The first bridge circuit (11) includes a period in which the first DC section (E1, C1) and the primary winding (n1) of the insulating transformer (TR1) are electrically connected, and a period in which the primary winding of the insulating transformer (TR1) (n1) includes a period in which both ends are short-circuited in the first bridge circuit (11),
the second bridge circuit (12) includes a rectifying period;
The control circuit (13)
variably controlling the phase difference between the first leg and the second leg;
Variable control of the simultaneous OFF period of the fifth switching element (S5) and the sixth switching element (S6), or variable control of the simultaneous OFF period of the seventh switching element (S7) and the eighth switching element (S8) A power converter (1) characterized by:
According to this, a step-down DC/DC converter with low noise and high efficiency can be realized.
[Item 2]
The control circuit (13)
When stepping down the voltage from the first DC section (E1, C1) to the second DC section (C2, E2) to transmit power,
The second bridge circuit ( 12) is the first pattern in the rectified state;
a second pattern in which both ends of the primary winding (n1) of the isolation transformer (TR1) are short-circuited in the first bridge circuit (11) and the second bridge circuit (12) is in a rectifying state;
The second bridge circuit ( 12) is the third pattern in the rectified state;
Both ends of the primary winding (n1) of the isolation transformer (TR1) are short-circuited in the first bridge circuit (11), and the second bridge circuit (12) controls including a fourth pattern of rectification state. A power converter (1) according to item 1, characterized by:
According to this, a step-down DC/DC converter with low noise and high efficiency can be realized.
[Item 3]
3. A power converter (1) according to item 2, characterized in that each period of the second pattern and the fourth pattern is fixed.
According to this, a step-down DC/DC converter with low noise and high efficiency can be realized.
[Item 4]
The control circuit (13) controls the voltage of the power supplied from the first DC section (E1, C1) to the second DC section (C2, E2) at the phase difference between the first leg and the second leg. 4. A power conversion device (1) according to any one of items 1 to 3, characterized in that it controls current.
According to this, by controlling the voltage or current by manipulating the phase difference on the primary side, the voltage or current can be controlled by soft switching.
[Item 5]
5. A power converter (1) according to item 4, characterized in that said control circuit (13) operates said phase difference in a range of 0 to 180 degrees.
According to this, it is possible to suppress the loss when the frequency is increased.
[Item 6]
The control circuit (13)
controlling the eighth switching element (S8) or the fifth switching element (S5) to an ON state in the second pattern;
A power conversion device (1) according to item 2 or 3, characterized in that in the fourth pattern, the seventh switching element (S7) or the sixth switching element (S6) is controlled to be in an ON state.
According to this, conduction loss of the diode can be reduced by performing synchronous rectification.
[Item 7]
The control circuit (13)
turning on the eighth switching element (S8) or the fifth switching element (S5) in synchronization with turning on the second switching element (S2) or turning off the first switching element (S1);
turning on the seventh switching element (S7) or the sixth switching element (S6) in synchronization with turning on the first switching element (S1) or turning off the second switching element (S2);
turning off the eighth switching element (S8) or the fifth switching element (S5) in synchronization with turning off the fourth switching element (S4) or turning on the third switching element (S3);
The seventh switching element (S7) or the sixth switching element (S6) is turned off in synchronization with the turn-off of the third switching element (S3) or the turn-on of the fourth switching element (S4). The power conversion device (1) according to item 6.
According to this, it is possible to perform synchronous rectification while suppressing the occurrence of recovery loss.
[Item 8]
The control circuit (13) reduces the voltage from the second DC section (C2, E2) to the first DC section (E1, C1) to transmit power, the first switching element (S1) - the first switching element (S1). 8. Any one of items 1 to 7, wherein the drive signal supplied to the 4 switching element (S4) and the drive signal supplied to the fifth switching element (S5) to the eighth switching element (S8) are exchanged. A power conversion device (1) according to any one of the preceding claims.
According to this, a step-down bidirectional DC/DC converter with low noise and high efficiency can be realized.
[Item 9]
The control circuit (13)
When stepping up and transmitting power from the first DC section (E1, C1) to the second DC section (C2, E2),
The first switching element (S1), the fourth switching element (S4), and the sixth switching element (S6) or the seventh switching element (S7) are in an ON state, and the remaining switching elements are in an OFF state. 5 patterns,
The second bridge circuit ( 12) is the sixth pattern in the rectified state,
The second switching element (S2), the third switching element (S3), and the fifth switching element (S5) or the eighth switching element (S8) are in the ON state, and the remaining switching elements are in the OFF state. 7 patterns,
The second bridge circuit ( 9. The power converter (1) according to any one of items 1 to 8, wherein 12) includes and controls an eighth pattern of rectification states.
According to this, a low-noise, high-efficiency buck-boost DC/DC converter can be realized.
[Item 10]
10. A power converter (1) according to item 9, characterized in that the period of each of the sixth pattern and the eighth pattern is fixed.
According to this, it is possible to prevent noise from being generated during the boosting operation.
[Item 11]
The control circuit (13) fixes the phase difference between the first leg and the second leg, and the ON time of the sixth switching element (S6) or the seventh switching element (S7) in the fifth pattern. , and at least one of the ON time of the fifth switching element (S5) or the eighth switching element (S8) in the seventh pattern, the first DC section (E1, C1) to the second DC section (C2 11. A power conversion device (1) according to item 9 or 10, characterized in that it controls the voltage or current of the power supplied to , E2).
According to this, the voltage or current can be controlled by operating the secondary side without operating the primary side.
[Item 12]
The control circuit (13) controls the first switching element (S1)-the first switching element (S1)-the 12. Any one of items 9 to 11, wherein the drive signal supplied to the 4 switching element (S4) and the drive signal supplied to the fifth switching element (S5) to the eighth switching element (S8) are exchanged. A power conversion device (1) according to any one of the preceding claims.
According to this, a low-noise, high-efficiency buck-boost bidirectional DC/DC converter can be realized.
[Item 13]
A first leg in which a first switching element (S1) and a second switching element (S2) are connected in series, and a second leg in which a third switching element (S3) and a fourth switching element (S4) are connected in series, a first bridge circuit (11) connected in parallel to the first DC section (E1, C1);
A third leg in which a fifth diode (D5) and a sixth diode (D6) are connected in series, and a fourth leg in which a seventh diode (D7) and an eighth diode (D8) are connected in series are the second DC section. a second bridge circuit (12) connected in parallel to (C2, R2);
an isolation transformer (TR1) connected between the first bridge circuit (11) and the second bridge circuit (12);
A control circuit (13) that controls the first switching element (S1)-the fourth switching element (S4),
Diodes (D1-D4) are connected or formed in antiparallel to each of the first switching element (S1) to the fourth switching element (S4),
The fifth diode (D5) to the eighth diode (D8) are connected in the opposite direction to the second DC section (C2, R2),
The control circuit (13)
When power is stepped down from the first DC section (E1, C1) to the second DC section (C2, R2) and transmitted,
a first pattern in which the first switching element (S1) and the fourth switching element (S4) are in an ON state, and the second switching element (S2) and the third switching element (S3) are in an OFF state;
a second pattern in which both ends of the primary winding (n1) of the isolation transformer (TR1) are short-circuited within the first bridge circuit (11);
a third pattern in which the second switching element (S2) and the third switching element (S3) are in an ON state, and the first switching element (S1) and the fourth switching element (S4) are in an OFF state;
including and controlling a fourth pattern in which both ends of the primary winding (n1) of the isolation transformer (TR1) are short-circuited in the first bridge circuit (11);
A power conversion device (1), wherein each period of the second pattern and the fourth pattern is fixed.
According to this, it is possible to realize a step-down unidirectional DC/DC converter with low cost, low noise and high efficiency.
[Item 14]
It has a first leg in which a first switching element (S1) and a second switching element (S2) are connected in series, and a second leg in which a third switching element (S3) and a fourth switching element (S4) are connected in series. and a first bridge circuit (11) in which the first leg and the second leg are connected in parallel to a first DC section (E1, C1);
A third leg in which a fifth switching element (S5) and a sixth switching element (S6) are connected in series, and a fourth leg in which a seventh diode (D7) and an eighth diode (D8) are connected in series, a second bridge circuit (12) in which the third leg and the fourth leg are connected in parallel to a second DC section (C2, R2);
an isolation transformer (TR1) connected between the first bridge circuit (11) and the second bridge circuit (12);
A control circuit (13) that controls the first switching element (S1)-the sixth switching element (S6),
Diodes (D1-D6) are connected or formed in antiparallel to each of the first switching element (S1) to the sixth switching element (S6),
The seventh diode (D7) and the eighth diode (D8) are connected in opposite directions to the second DC section (C2, R2),
The control circuit (13)
a first pattern in which the first switching element (S1) and the fourth switching element (S4) are in an ON state and the remaining switching elements are in an OFF state;
a second pattern in which both ends of the primary winding (n1) of the isolation transformer (TR1) are short-circuited in the first bridge circuit (11) and the second bridge circuit (12) is in a rectifying state;
a third pattern in which the second switching element (S2) and the third switching element (S3) are in an ON state and the remaining switching elements are in an OFF state;
Both ends of the primary winding (n1) of the isolation transformer (TR1) are short-circuited in the first bridge circuit (11), and the second bridge circuit (12) is controlled including a fourth pattern in a rectified state. ,
A power conversion device (1), wherein each period of the second pattern and the fourth pattern is fixed.
According to this, it is possible to realize a step-down unidirectional DC/DC converter with low cost, low noise and high efficiency.
[Item 15]
The control circuit (13)
When stepping up and transmitting power from the first DC section (E1, C1) to the second DC section (C2, R2),
a fifth pattern in which the first switching element (S1), the fourth switching element (S4), and the sixth switching element (S6) are in an ON state, and the remaining switching elements are in an OFF state;
The second bridge circuit ( 12) is the sixth pattern in the rectified state,
a seventh pattern in which the second switching element (S2), the third switching element (S3), and the fifth switching element (S5) are in an ON state, and the remaining switching elements are in an OFF state;
The second bridge circuit ( A power converter (1) according to item 14, characterized in that 12) includes and controls an eighth pattern of commutation states.
According to this, it is possible to realize a step-up/step-down unidirectional DC/DC converter with low cost, low noise, and high efficiency.
[Item 16]
16. A power converter (1) according to item 15, characterized in that the period of each of the sixth pattern and the eighth pattern is fixed.
According to this, it is possible to prevent noise from being generated during the boosting operation.

E1 first DC power supply E2 second DC power supply 1 power converter 11 first bridge circuit 12 second bridge circuit 13 control circuit S1-S8 switching element D1-D8 diode L reactor TR1 isolation transformer , n1 primary winding, n2 secondary winding, L1 first leakage inductance, L2 second leakage inductance, C1 first capacitor, C2 second capacitor, R2 load.

Claims (16)

A first leg in which a first switching element and a second switching element are connected in series, and a second leg in which a third switching element and a fourth switching element are connected in series, wherein the first leg and the second leg are connected in series. a first bridge circuit connected in parallel to the first DC section;
A third leg in which a fifth switching element and a sixth switching element are connected in series, and a fourth leg in which a seventh switching element and an eighth switching element are connected in series, wherein the third leg and the fourth leg are connected in series. a second bridge circuit connected in parallel to the second DC section;
an isolation transformer connected between the first bridge circuit and the second bridge circuit;
A control circuit that controls the first switching element-the eighth switching element,
A diode is connected or formed in anti-parallel to each of the first switching element and the eighth switching element,
When stepping down the voltage from the first DC section to the second DC section to transmit power,
The control circuit is
When stepping down the voltage from the first DC section to the second DC section to transmit power,
a first pattern in which the first switching element and the fourth switching element are in an ON state, the second switching element and the third switching element are in an OFF state, and the second bridge circuit is in a rectifying state;
a second pattern in which both ends of the primary winding of the isolation transformer are short-circuited in the first bridge circuit and the second bridge circuit is in a rectifying state;
a third pattern in which the second bridge circuit is in a rectifying state with the second switching element and the third switching element in an ON state, the first switching element and the fourth switching element in an OFF state;
a fourth pattern in which both ends of the primary winding of the isolation transformer are short-circuited in the first bridge circuit and the second bridge circuit is in a rectified state;
At least one of the first pattern and the third pattern includes a state in which both the first DC section and the second DC section are charged with energy from the insulating transformer side. . 2. The power converter according to claim 1 , wherein each period of said second pattern and said fourth pattern is fixed. 2. The control circuit controls the voltage or current of the electric power supplied from the first DC section to the second DC section based on the phase difference between the first leg and the second leg. Or the power conversion device according to 2 . 4. The power converter according to claim 3 , wherein said control circuit operates said phase difference within a range of 0 to 180 degrees. The control circuit is
controlling the eighth switching element or the fifth switching element to an ON state in the second pattern;
3. The power converter according to claim 1, wherein the seventh switching element or the sixth switching element is controlled to be in an ON state in the fourth pattern. The control circuit is
turning on the eighth switching element or the fifth switching element in synchronization with turning on the second switching element or turning off the first switching element;
turning on the seventh switching element or the sixth switching element in synchronization with turning on the first switching element or turning off the second switching element;
turning off the eighth switching element or the fifth switching element in synchronization with turning off the fourth switching element or turning on the third switching element;
6. The power converter according to claim 5 , wherein the seventh switching element or the sixth switching element is turned off in synchronization with turning off the third switching element or turning on the fourth switching element. When stepping down power from the second DC section to the first DC section and transmitting power, the control circuit supplies a drive signal to the first switching element--the fourth switching element, and the fifth switching element-- 7. The power converter according to any one of claims 1 to 6 , wherein the drive signal supplied to said eighth switching element is switched. The control circuit is
When boosting power from the first DC section to the second DC section and transmitting power,
a fifth pattern in which the first switching element, the fourth switching element, and the sixth switching element or the seventh switching element are in an ON state, and the remaining switching elements are in an OFF state;
a sixth pattern in which the first switching element and the fourth switching element are in an ON state, the second switching element and the third switching element are in an OFF state, and the second bridge circuit is in a rectifying state;
a seventh pattern in which the second switching element, the third switching element, and the fifth switching element or the eighth switching element are in an ON state, and the remaining switching elements are in an OFF state;
Control including an eighth pattern in which the second bridge circuit is in a rectifying state with the second switching element and the third switching element in an ON state, and the first switching element and the fourth switching element in an OFF state. The power converter according to any one of claims 1 to 7 , characterized in that: 9. The power converter according to claim 8 , wherein each period of said sixth pattern and said eighth pattern is fixed. The control circuit fixes the phase difference between the first leg and the second leg, the on-time of the sixth switching element or the seventh switching element in the fifth pattern, and the on-time of the seventh switching element in the seventh pattern. 10. The method according to claim 8, wherein the voltage or current of the power supplied from the first DC section to the second DC section is controlled during at least one of the ON time of the fifth switching element or the eighth switching element. A power converter as described. When stepping up and transmitting power from the second DC section to the first DC section, the control circuit supplies a drive signal to the first switching element--the fourth switching element; and the fifth switching element-- 11. The power converter according to any one of claims 8 to 10 , wherein the drive signal supplied to said eighth switching element is switched. A first bridge in which a first leg in which a first switching element and a second switching element are connected in series and a second leg in which a third switching element and a fourth switching element are connected in series are connected in parallel to a first DC section a circuit;
a second bridge circuit in which a third leg in which a fifth diode and a sixth diode are connected in series and a fourth leg in which a seventh diode and an eighth diode are connected in series are connected in parallel to a second DC section;
an isolation transformer connected between the first bridge circuit and the second bridge circuit;
A control circuit that controls the first switching element-the fourth switching element,
a diode is connected or formed in antiparallel to each of the first switching element and the fourth switching element,
The fifth diode - the eighth diode are connected in reverse to the second DC section,
The control circuit is
When stepping down the voltage from the first DC section to the second DC section to transmit power,
a first pattern in which the first switching element and the fourth switching element are in an ON state, and the second switching element and the third switching element are in an OFF state;
a second pattern in which both ends of the primary winding of the isolation transformer are short-circuited within the first bridge circuit;
a third pattern in which the second switching element and the third switching element are in an ON state, and the first switching element and the fourth switching element are in an OFF state;
including and controlling a fourth pattern in which both ends of the primary winding of the isolation transformer are short-circuited in the first bridge circuit;
At least one of the first pattern and the third pattern includes a state in which both the first DC section and the second DC section are charged with energy from the insulating transformer side. . A first leg in which a first switching element and a second switching element are connected in series, and a second leg in which a third switching element and a fourth switching element are connected in series, wherein the first leg and the second leg are connected in series. a first bridge circuit connected in parallel to the first DC section;
It has a third leg in which a fifth switching element and a sixth switching element are connected in series and a fourth leg in which a seventh diode and an eighth diode are connected in series, and the third leg and the fourth leg are the second leg. a second bridge circuit connected in parallel to the DC section;
an isolation transformer connected between the first bridge circuit and the second bridge circuit;
A control circuit that controls the first switching element-the sixth switching element,
a diode is connected or formed in antiparallel to each of the first switching element and the sixth switching element,
The seventh diode and the eighth diode are connected in opposite directions to the second DC section,
The control circuit is
a first pattern in which the first switching element and the fourth switching element are in an ON state, and the remaining switching elements are in an OFF state;
a second pattern in which both ends of the primary winding of the isolation transformer are short-circuited in the first bridge circuit and the second bridge circuit is in a rectifying state;
a third pattern in which the second switching element and the third switching element are in an ON state, and the remaining switching elements are in an OFF state;
a fourth pattern in which both ends of the primary winding of the isolation transformer are short-circuited in the first bridge circuit and the second bridge circuit is in a rectified state;
At least one of the first pattern and the third pattern includes a state in which both the first DC section and the second DC section are charged with energy from the insulating transformer side. . 14. The power converter according to claim 12, wherein each period of said second pattern and said fourth pattern is fixed. The control circuit is
When boosting power from the first DC section to the second DC section and transmitting power,
a fifth pattern in which the first switching element, the fourth switching element, and the sixth switching element are in an ON state, and the remaining switching elements are in an OFF state;
a sixth pattern in which the first switching element and the fourth switching element are in an ON state, the second switching element and the third switching element are in an OFF state, and the second bridge circuit is in a rectifying state;
a seventh pattern in which the second switching element, the third switching element, and the fifth switching element are in an ON state, and the remaining switching elements are in an OFF state;
Control including an eighth pattern in which the second bridge circuit is in a rectifying state with the second switching element and the third switching element in an ON state, and the first switching element and the fourth switching element in an OFF state. 14. The power converter according to claim 13 , characterized by: 16. The power converter according to claim 15, wherein each period of said sixth pattern and said eighth pattern is fixed.

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