JP2014171313A - Dc/dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC/DC converter capable of obtaining double voltage with a simple configuration.SOLUTION: When outputting a double voltage from a first input/output terminal 13 to a second input/output terminal 33, a control circuit 49 of a DC/DC converter 11 controls any one of a fifth switching element 35, a sixth switching element 37, a seventh switching element 41 and an eighth switching element 43 to maintain ON state. When outputting a double voltage from the second input/output terminal 33 to the first input/output terminal 13, the control circuit 49 controls any one of a first switching element 15, a second switching element 17, a third switching element 21 and a fourth switching element 23 to maintain ON state.

Description

  The present invention relates to a DC / DC converter that performs voltage conversion.

  Conventionally, for example, Patent Document 1 proposes a DC / DC converter for exchanging power between DC power supplies having different voltages.

  A circuit diagram of this DC / DC converter is shown in FIG. FIG. 5 shows a bidirectional DC / DC converter. In FIG. 5, a DC power source (not shown, for example, a car battery) is connected to the low-voltage side terminals 101 and 103. Further, another DC power source (not shown, for example, a DC power source including an automobile generator) is also connected to the high-voltage side terminals 105 and 107. A transformer 109 is connected between the low voltage side terminals 101 and 103 and the high voltage side terminals 105 and 107.

  Further, a low voltage side switching unit 111 is inserted between the low voltage side terminals 101 and 103 and the transformer 109, and a high voltage side switching unit 113 is inserted between the high voltage side terminals 105 and 107 and the transformer 109. The low-voltage side switching unit 111 and the high-voltage side switching unit 113 are each configured by bridge-connecting four switching elements (hereinafter referred to as FETs) such as field effect transistors (FETs).

  An LC resonance circuit 115 is inserted between the high-voltage side terminals 105 and 107 and the high-voltage side winding of the transformer 109.

  Output smoothing capacitors 117 and 119 are connected between the low voltage side terminals 101 and 103 and between the high voltage side terminals 105 and 107.

  Next, the operation of the conventional bidirectional DC / DC converter will be described in the case where power is supplied from the low voltage side terminals 101 and 103 to the high voltage side terminals 105 and 107. Note that power supply in the reverse direction is the same operation as described below.

  In FIG. 5, the upper left and lower right pairs and the upper right and lower left pairs of the four FETs in the low voltage side switching unit 111 are alternately turned on and off, whereby the voltage of the low voltage side winding of the transformer 109 becomes positive and negative. When applied alternately, a positive and negative rectangular wave voltage is generated in the high-voltage side winding of the transformer 109. The current induced in the high-voltage side winding is input to the high-voltage side switching unit 113 through the LC resonance circuit 115, rectified by the rectifying element in the FET of the high-voltage side switching unit 113, smoothed by the smoothing capacitor 119, and output. At this time, the current flowing through the primary side and the secondary side becomes sinusoidal due to the presence of the LC resonance circuit 115. As a result, the timing at which the FET is turned off can be set in the vicinity of the zero cross point where the current value is almost zero, so that the FET can be switched near the zero cross point of the current value, and the switching loss. It is possible to greatly reduce the power consumption and exchange power.

  In such a bidirectional DC / DC converter, the voltage output to the high-voltage side terminals 105 and 107 may need to be doubled depending on the situation. At this time, for example, Patent Document 2 proposes a configuration in which an external circuit is provided in the rectifier circuit and the output is doubled.

  FIG. 6 is a circuit diagram showing a configuration example of a switching power supply circuit having a voltage doubler configuration. In FIG. 6, the rectifier circuit system that generates the rectified and smoothed voltage Ei from the commercial AC power supply 121 includes a bridge rectifier circuit 123 and two smoothing capacitors 125 and 127. The smoothing capacitors 125 and 127 have the same capacitance. The rectified and smoothed voltage Ei is obtained as a voltage across the series connection circuit of the smoothing capacitors 125 and 127. A relay switch 129 is inserted between the negative output terminal of the bridge rectifier circuit 123 and the connection point of the smoothing capacitors 125 and 127. The relay switch 129 is turned on / off according to the driving state of the relay 133 connected to the rectifier circuit switching module 131.

  The switching operation of such a rectifier circuit is as follows. When the relay switch 129 is OFF, the AC input voltage VAC is rectified by the bridge rectifier circuit 123 and charged to the series connection circuit of the smoothing capacitors 125 and 127. As a result, a rectified and smoothed voltage Ei corresponding to the AC input voltage VAC is obtained as the voltage across the series connection circuit of the smoothing capacitors 125 and 127.

  When the relay 133 is turned on, the relay switch 129 is turned on, and the rectified output by the bridge rectifier circuit 123 is charged only to the smoothing capacitor 125 during the period when the AC input voltage VAC is positive. On the other hand, when the AC input voltage VAC is negative, the rectified output from the bridge rectifier circuit 123 is charged only to the smoothing capacitor 127. Accordingly, the rectified and smoothed voltage Ei, which is the voltage across the series connection circuit of the smoothing capacitors 125 and 127, has a level corresponding to twice the AC input voltage VAC, thereby forming a voltage doubler rectifier circuit.

JP 2004-282828 A JP 2004-166462 A

  When the voltage doubler rectifier circuit of FIG. 6 is provided in the bidirectional DC / DC converter of FIG. 5 described above, the voltage doubler is output from the bidirectional DC / DC converter according to the situation by controlling the relay 133. However, two smoothing capacitors 125, 127, a relay switch 129, and a relay 133 are required for this purpose. Therefore, there is a problem that the circuit configuration becomes complicated in order to obtain a double voltage.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a DC / DC converter capable of obtaining a double voltage with a simple configuration.

  In order to solve the conventional problem, a DC / DC converter according to the present invention includes a first switching element and a second switching element, one end of which is electrically connected to the first input / output terminal. The DC / DC converter according to the present invention further includes a third switching element electrically connected between the other end of the first switching element and a first ground terminal. The DC / DC converter according to the present invention further includes a fourth switching element electrically connected between the other end of the second switching element and the first ground terminal. The DC / DC converter according to the present invention includes a first capacitor between a connection point of the first switching element and the third switching element and a connection point of the second switching element and the fourth switching element. Including a primary winding of a transformer electrically connected via The DC / DC converter of the present invention includes a fifth switching element and a sixth switching element, one end of which is electrically connected to the second input / output terminal. The DC / DC converter according to the present invention further includes a seventh switching element electrically connected between the other end of the fifth switching element and the second ground terminal. The DC / DC converter of the present invention further includes an eighth switching element electrically connected between the other end of the sixth switching element and the second ground terminal. The DC / DC converter of the present invention includes a second capacitor between a connection point of the fifth switching element and the seventh switching element and a connection point of the sixth switching element and the eighth switching element. A secondary winding of the transformer that is electrically connected via The DC / DC converter of the present invention includes the first switching element, the second switching element, the third switching element, the fourth switching element, the fifth switching element, the sixth switching element, and the seventh switching element. A switching element and a control circuit connected to the eighth switching element are provided. The control circuit outputs the fifth switching element, the sixth switching element, the seventh switching element, or the eighth switching element when outputting a voltage from the first input / output terminal to the second input / output terminal. There is a control state in which any one of the switching elements is controlled to maintain the on state. The control circuit outputs the first switching element, the second switching element, the third switching element, or the fourth switching element when outputting a voltage from the second input / output terminal to the first input / output terminal. It has a control state in which any one of the switching elements is controlled to maintain the on state.

  The DC / DC converter of the present invention includes a first switching element and a second switching element, one end of which is electrically connected to the input terminal. The DC / DC converter according to the present invention further includes a third switching element electrically connected between the other end of the first switching element and a first ground terminal. The DC / DC converter according to the present invention further includes a fourth switching element electrically connected between the other end of the second switching element and the first ground terminal. The DC / DC converter according to the present invention includes a first capacitor between a connection point of the first switching element and the third switching element and a connection point of the second switching element and the fourth switching element. Including a primary winding of a transformer electrically connected via The DC / DC converter of the present invention includes a first diode and a second diode whose cathode is electrically connected to the output terminal. In the DC / DC converter of the present invention, a cathode is electrically connected to either the anode of the first diode or the anode of the second diode, and the anode is electrically connected to the second ground terminal. A third diode connected is provided. The DC / DC converter according to the present invention further includes a fourth diode electrically connected between the anode of the first diode or the anode of the second diode and the second ground terminal. . The DC / DC converter according to the present invention further includes a switch electrically connected in parallel to any one of the first diode, the second diode, the third diode, and the fourth diode. The DC / DC converter according to the present invention further includes a secondary winding of the transformer electrically connected via a second capacitor between the anode of the first diode and the anode of the second diode. . The DC / DC converter of the present invention includes a control circuit connected to the first switching element, the second switching element, the third switching element, the fourth switching element, and the switch. The control circuit has a control state in which the switch is controlled to maintain an ON state when a voltage is output from the input terminal to the output terminal.

  According to the DC / DC converter of the present invention, when the control circuit outputs a voltage from the first input / output terminal to the second input / output terminal, the fifth switching element, the sixth switching element, the seventh switching element, or There is a control state in which any one of the eighth switching elements is controlled to maintain the on state. Therefore, in this state, when the charged second capacitor is discharged, the series circuit including the second capacitor and the secondary winding outputs a double voltage. Therefore, there is an effect that a DC / DC converter capable of obtaining a double voltage with a simple configuration is obtained without requiring a circuit configuration for obtaining a double voltage. Similarly, according to the DC / DC converter of the present invention, when the control circuit outputs a voltage from the second input / output terminal to the first input / output terminal, the first switching element, the second switching element, and the third switching element. By having a control state in which any one of the element and the fourth switching element is controlled to maintain the ON state, when the charged first capacitor is discharged, from the first capacitor and the primary winding This series circuit outputs a double voltage. Therefore, there is an effect that a DC / DC converter capable of obtaining a double voltage with a simple configuration is obtained without requiring a circuit configuration for obtaining a double voltage.

  Further, according to the DC / DC converter of the present invention, the control circuit is charged by having a control state in which the switch is controlled to maintain the on state when the voltage is output from the input terminal to the output terminal. When the capacitor is discharged, the series circuit composed of the capacitor and the secondary winding outputs a double voltage. Therefore, it is possible to obtain a DC / DC converter capable of obtaining a double voltage with a simple configuration in which a switch for obtaining a double voltage is provided.

1 is a block circuit diagram of a DC / DC converter according to Embodiment 1 of the present invention. It is a figure which shows the electric current direction which flows into the 2nd capacitor | condenser of the DC / DC converter in Embodiment 1 of this invention, (a) is a figure which shows the electric current direction when a 2nd capacitor is charged, (b) is a 1st figure. Diagram showing the current direction when two capacitors are discharged It is a figure which shows the other electric current direction which flows into the 2nd capacitor | condenser of the DC / DC converter in Embodiment 1 of this invention, (a) is a figure which shows the electric current direction at the time of charging a 2nd capacitor | condenser, (b) Is a diagram showing the current direction when the second capacitor is discharged Block circuit diagram of a DC / DC converter according to Embodiment 3 of the present invention Circuit diagram of conventional bidirectional DC / DC converter Circuit diagram showing a configuration example of a conventional switching power supply circuit

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a block circuit diagram of a DC / DC converter according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing the direction of current flowing through the second capacitor of the DC / DC converter according to Embodiment 1 of the present invention. FIG. 2A is a diagram showing the direction of current when the second capacitor is charged. b) is a diagram showing a current direction when the second capacitor is discharged. FIG. 3 is a diagram showing another direction of current flowing through the second capacitor of the DC / DC converter according to Embodiment 1 of the present invention, and (a) is a diagram showing the direction of current when the second capacitor is charged. (B) is a figure which shows the electric current direction when a 2nd capacitor | condenser is discharged.

  In FIG. 1, the DC / DC converter 11 includes a first switching element 15 and a second switching element 17, one end of which is electrically connected to the first input / output terminal 13. The DC / DC converter 11 includes a third switching element 21 that is electrically connected between the other end of the first switching element 15 and the first ground terminal 19. Further, the DC / DC converter 11 includes a fourth switching element 23 that is electrically connected between the other end of the second switching element 17 and the first ground terminal 19. The DC / DC converter 11 includes a first capacitor 25 between the connection point of the first switching element 15 and the third switching element 21 and the connection point of the second switching element 17 and the fourth switching element 23. A primary winding 31 of a transformer 29 that is electrically connected via the wiring. In addition, the DC / DC converter 11 includes a fifth switching element 35 and a sixth switching element 37, one end of which is electrically connected to the second input / output terminal 33. Further, the DC / DC converter 11 includes a seventh switching element 41 that is electrically connected between the other end of the fifth switching element 35 and the second ground terminal 39. In addition, the DC / DC converter 11 includes an eighth switching element 43 that is electrically connected between the other end of the sixth switching element 37 and the second ground terminal 39. Further, the DC / DC converter 11 includes a second capacitor 45 between the connection point of the fifth switching element 35 and the seventh switching element 41 and the connection point of the sixth switching element 37 and the eighth switching element 43. The secondary winding 47 of the transformer 29 is electrically connected via this. The DC / DC converter 11 includes a first switching element 15, a second switching element 17, a third switching element 21, a fourth switching element 23, a fifth switching element 35, a sixth switching element 37, and a seventh switching element 41. The control circuit 49 connected to the eighth switching element 43 is provided. When the control circuit 49 outputs a voltage from the first input / output terminal 13 to the second input / output terminal 33, the fifth switching element 35, the sixth switching element 37, the seventh switching element 41, or the eighth switching element. There is a control state in which any one of the elements 43 is controlled to maintain the on state. When the control circuit 49 outputs a voltage from the second input / output terminal 33 to the first input / output terminal 13, the first switching element 15, the second switching element 17, the third switching element 21, or the fourth switching element. There is a control state in which any one of the elements 23 is controlled to maintain the on state.

  Thus, when the control circuit 49 outputs a voltage from the first input / output terminal 13 to the second input / output terminal 33, the fifth switching element 35, the sixth switching element 37, the seventh switching element 41, or the eighth switching element By having a control state in which any one of the switching elements 43 is controlled to maintain the on state, the second capacitor 45 and the secondary winding 47 are formed when the charged second capacitor 45 is discharged. A series circuit outputs a double voltage. Therefore, it is possible to obtain the DC / DC converter 11 that does not require a circuit configuration for obtaining a double voltage and can obtain a double voltage with a simple configuration. Similarly, the control circuit 49 outputs the first switching element 15, the second switching element 17, the third switching element 21, or the fourth switching element when outputting a voltage from the second input / output terminal 33 to the first input / output terminal 13. By having a control state in which any one of the switching elements 23 is controlled to maintain the ON state, the first capacitor 25 and the primary winding 31 are formed when the charged first capacitor 25 is discharged. A series circuit outputs a double voltage. Therefore, it is possible to obtain the DC / DC converter 11 that does not require a circuit configuration for obtaining a double voltage and can obtain a double voltage with a simple configuration.

  Hereinafter, the configuration and operation of the first embodiment will be described more specifically.

  As an example of voltage conversion from the first input / output terminal 13 to the second input / output terminal 33 in Embodiment 1, the DC / DC converter 11 as a battery charger for an electric vehicle is described. The voltage conditions at this time are determined as follows. First, AC 100V or AC 200V (effective value) system power is converted into DC / DC by DC / DC converter (not shown) DC 190V (hereinafter referred to simply as 190V) or 380V. It is assumed that the signal is input to the converter 11. Then, the DC / DC converter 11 charges the electric vehicle battery having a full charge voltage of 200 V with the input power.

  The reason why the voltage of the system power supply is of two types, AC 100V or AC 200V (effective value), is that the voltage standard varies depending on the region and corresponds to it.

  The voltage output from the AC / DC converter is determined as follows. When the voltage of the system power supply is, for example, AC 100V (effective value), the peak value is about 141V. When voltage conversion is performed by the DC / DC converter 11 with this peak voltage, ripples are superimposed, so that a higher voltage is output from the AC / DC converter. Here, the AC / DC converter is designed to output 190V in the case of an input voltage of AC 100V (effective value) so that ripples are not superimposed and a margin is taken into consideration. From this, in the case of an input voltage of AC 200V (effective value), the AC / DC converter outputs 380V. Therefore, as described above, a voltage of 190 V or 380 V is input to the DC / DC converter 11.

  In FIG. 1, a DC power supply 51 including the AC / DC converter is connected to the first input / output terminal 13 and the first ground terminal 19 of the DC / DC converter 11. The output voltage of the DC power supply 51 is 190V or 380V. The DC power supply 51 also includes a load (not shown) connected to the system power supply.

  A first smoothing capacitor 53 is electrically connected between the first input / output terminal 13 and the first ground terminal 19. The first input / output terminal 13 is electrically connected to the control circuit 49 in order to detect the first input / output terminal voltage V1. The control circuit 49 includes a voltage detection circuit for obtaining the first input / output terminal voltage V1 and outputting it to a microcomputer (not shown) built in the control circuit 49.

  Here, since the high voltage (190 V or 380 V) is applied to the voltage detection circuit as described above, a circuit that drops the voltage to a level that can be output to the microcomputer that operates at 5 V, for example, is also included. This voltage drop circuit is magnetically insulated by a transformer and optically insulated by a photocoupler. Therefore, in the following description, it is assumed that the circuit configuration in which the above-described insulation is taken is used in a portion where the high voltage system and the low voltage system are connected. A circuit connection portion through such insulation is simply referred to as “connection”, and a portion connected without insulation is referred to as “electrically connected”. However, when the voltage detected by the voltage detection circuit is at the same level as the operating voltage of the microcomputer, a circuit configuration that does not require insulation may be employed.

  A series circuit of the first switching element 15 and the third switching element 21 is electrically connected between the first input / output terminal 13 and the first ground terminal 19. The first switching element 15 and the third switching element 21 are composed of FETs. Accordingly, the first switching element 15 and the third switching element 21 include parasitic diodes as shown in FIG.

  Similarly, a series circuit of the second switching element 17 and the fourth switching element 23 is electrically connected between the first input / output terminal 13 and the first ground terminal 19. The second switching element 17 and the fourth switching element 23 are also composed of FETs. Accordingly, the second switching element 17 and the fourth switching element 23 include parasitic diodes.

  Between the connection point of the first switching element 15 and the third switching element 21 and the connection point of the second switching element 17 and the fourth switching element 23, a series circuit of the first capacitor 25 and the inductor 55 is interposed. The primary winding 31 of the transformer 29 is electrically connected. The inductor 55 may be used as a leakage inductor for the primary winding 31. In this case, the inductor 55 may not be provided.

  Next, the second input / output terminal 33 and the second ground terminal 39 of the DC / DC converter 11 are connected to an electric vehicle battery (hereinafter referred to as the battery 57) having a full charge voltage of 200V as another DC power source. The A second smoothing capacitor 59 is electrically connected between the second input / output terminal 33 and the second ground terminal 39. The second input / output terminal 33 is connected to the control circuit 49 in order to detect the second input / output terminal voltage V2. The control circuit 49 includes a voltage detection circuit for obtaining the second input / output terminal voltage V2 and outputting it to the microcomputer incorporated in the control circuit 49.

  The second ground terminal 39 is connected to a current sensor 61 that detects a current I flowing through the second ground terminal. Since the current sensor 61 is electrically connected to the control circuit 49, the value of the current I output from the current sensor 61 is taken into the control circuit 49. The value of the current I output from the current sensor 61 corresponds to the charging current of the battery 57.

  Between the second input / output terminal 33 and the second ground terminal 39, a series circuit of the fifth switching element 35 and the seventh switching element 41 and a series circuit of the sixth switching element 37 and the eighth switching element 43 are electrically connected. Connected. The fifth switching element 35 to the eighth switching element 43 are also composed of FETs. Accordingly, the fifth switching element 35 to the eighth switching element 43 also include parasitic diodes.

  Between the connection point of the fifth switching element 35 and the seventh switching element 41 and between the connection point of the sixth switching element 37 and the eighth switching element 43, the secondary of the transformer 29 is interposed via the second capacitor 45. Winding 47 is electrically connected.

  The first switching element 15, the second switching element 17, the third switching element 21, the fourth switching element 23, the fifth switching element 35, the sixth switching element 37, the seventh switching element 41, and the eighth switching element 43 are controlled. The circuit 49 is connected.

  The control circuit 49 includes the microcomputer and peripheral circuits (the voltage detection circuit, the drive circuit for the first switching element 15 to the eighth switching element 43, a memory, etc.), and the first switching element 15 to the eighth switching circuit. The switching of the element 43 is controlled to switch the direction in which the current I flows and to control the voltage of the first input / output terminal voltage V1 and the second input / output terminal voltage V2.

  Next, the operation of such a DC / DC converter 11 will be described.

  First, a case where power is supplied from the first input / output terminal 13 and the first ground terminal 19 to the second input / output terminal 33 and the second ground terminal 39 will be described. This corresponds to an operation of stepping down the voltage of 190V or 380V of the DC power supply 51 by the DC / DC converter 11 and outputting 200V which is the fully charged voltage of the battery 57. Here, the case where the voltage of the DC power supply 51 is 380 V (ie, the system power supply corresponds to an AC 200 V region) will be described first.

  First, the control circuit 49 detects the first input / output terminal voltage V1. Then, it is determined whether the first input / output terminal voltage V1 is 190V or 380V. Here, since it is 380 V, the following operation is performed.

  The control circuit 49 turns off the fifth switching element 35, the sixth switching element 37, the seventh switching element 41, and the eighth switching element 43. Accordingly, the parasitic diode from the fifth switching element 35 to the eighth switching element 43 forms a bridge circuit, and functions as a rectifier circuit.

  Next, the control circuit 49 turns on and off the first switching element 15, the second switching element 17, the third switching element 21, and the fourth switching element 23, thereby controlling the first input / output terminal voltage V <b> 1 ( 380 V) and output power from the second input / output terminal 33. Here, since the step-down ratio is 200 V / 380 V = about 0.53, the winding ratio of the primary winding 31 and the secondary winding 47 of the transformer 29 is determined so as to be this ratio. Further, in the configuration of FIG. 1, a resonance circuit including the first capacitor 25, the inductor 55, and the primary winding 31 is configured, so that the frequency is controlled in the switching control. Therefore, the on / off ratio of the switching control is 1: 1.

  In this frequency control, the step-up ratio increases as the frequency decreases. Therefore, the control circuit 49 controls the charging of the battery 57 by changing the frequency according to the voltage level of the battery 57. Further, the control circuit 49 monitors the value of the current I detected by the current sensor 61, and if the value reaches the predetermined current Ik which is lower than the preset overcurrent by a predetermined margin, the control circuit 49 sets the value of the current I. Control to maintain.

  Here, a case where the voltage of the battery 57 is close to the full charge voltage will be described.

  The control circuit 49 detects the second input / output terminal voltage V2 and performs frequency control so that the target value is 200V. As a result, the voltage of 380V input from the DC power supply 51 is converted to 200V by the step-down ratio and output. At this time, since the fifth switching element 35 to the eighth switching element 43 are all turned off, a general bridge rectifier circuit is formed by these parasitic diodes. Therefore, the step-down operation is the same as in the conventional FIG.

  Next, the case where the voltage of the DC power supply 51 is 190V (the system power supply corresponds to an area of AC 100V), which is the characteristic operation of the first embodiment, will be described. In this case, it is assumed that the battery 57 is almost fully charged.

  First, the control circuit 49 detects the first input / output terminal voltage V1 and determines that the value is 190V. As a result, the control circuit 49 performs an operation of outputting a double voltage. Specifically, when the control circuit 49 outputs a voltage from the first input / output terminal 13 to the second input / output terminal 33, the control circuit 49 includes four switches from the fifth switching element 35 to the eighth switching element 43 constituting the rectifier circuit. It has a control state in which any one of the elements is controlled to maintain the on state and the other switching elements are controlled to be turned off.

  Here, more specifically, the operation will be described with reference to FIG. 2 in the case where the control circuit 49 performs control so as to maintain the ON state of the eighth switching element 43.

  As shown in FIG. 2A, the fifth switching element 35, the sixth switching element 37, and the seventh switching element 41 are in the off state. Accordingly, parasitic diodes in these switching elements are effective. On the other hand, since the eighth switching element 43 is in the on state, a current can flow in any direction.

  In this state, although not shown in FIG. 2A, when the first switching element 15 to the fourth switching element 23 perform the on / off operation, both ends of the secondary winding 47 correspond to the on / off operation. Voltage is generated. Here, in the state of FIG. 2A, it is assumed that a positive voltage is generated on the lower side of the secondary winding 47, that is, on the connection point side between the sixth switching element 37 and the eighth switching element 43. In this case, a current flows from the positive voltage side of the secondary winding 47 as shown by a thick arrow in FIG. Specifically, from the positive voltage side of the secondary winding 47, via the connection point of the sixth switching element 37 and the eighth switching element 43, from the eighth switching element 43 in the on state via the ground, A current flows through a parasitic diode of the seventh switching element 41 and a path reaching the second capacitor 45. As a result, the second capacitor 45 is charged. Then, a positive voltage is generated on the second capacitor 45 on the connection point side between the fifth switching element 35 and the seventh switching element 41. Further, the absolute value of the voltage across the second capacitor 45 at this time is substantially equal to the absolute value of the voltage across the secondary winding 47.

  In this state, when the on / off state of the first switching element 15 to the fourth switching element 23 is reversed, the sign of the voltage generated in the secondary winding 47 is reversed as shown in FIG. Therefore, in the series circuit of the secondary winding 47 and the second capacitor 45, a sum of voltages at both ends of the secondary winding 47 and the second capacitor 45 is generated. Therefore, current flows from the positive electrode of the second capacitor 45 to the second input / output terminal 33 via the parasitic diode of the fifth switching element 35 as indicated by the thick arrow in FIG. Although this current is not shown in FIG. 2B, the current flows to the battery 57 to charge the battery, and passes from the ground to the secondary winding 47 through the second ground terminal 39 and the eighth switching element 43. Pass through. For these reasons, between the second input / output terminal 33 and the second ground terminal 39, the sum of the voltages across the secondary winding 47 and the second capacitor 45, that is, the second capacitor 45 is 2 Since the voltage is substantially equal to that of the secondary winding 47, a voltage approximately twice as large as that generated in the secondary winding 47 is generated. Therefore, it is possible to output a double voltage with a simple circuit configuration that only maintains the eighth switching element 43 in the on state.

  In this case, since the voltage input to the DC / DC converter 11 is 190 V and the step-down ratio is about 0.53 as described above, all of the fifth switching element 35 to the eighth switching element 43 are turned off. With the normal rectifier circuit configuration, the output voltage of the DC / DC converter 11 is 190 V × 0.53 = 100.7 V. By obtaining the double voltage by the above control, the output voltage is calculated to be 100. 7V × 2 = 201.4V. Here, in the current path indicated by the thick arrow in FIG. 2B, since the parasitic diode of the fifth switching element 35 is passed, the voltage drop (about 1 V) occurs, and the final DC / DC converter 11 The output voltage is approximately 200V.

  With such an operation, the output voltage can be 200 V regardless of whether the input voltage to the DC / DC converter 11 is 190 V or 380 V. Therefore, even if the DC / DC converter 11 is used in an area where the system power supply standards are different, a voltage (200 V in this case) necessary for charging the battery 57 can be obtained with a simple circuit configuration.

  In FIG. 2, the case where the control circuit 49 maintains the ON state of the low-side eighth switching element 43 has been described. This is because the control circuit 49 is not the eighth switching element 43 but the fifth switching element 35, You may control so that any one state of the 6th switching element 37 or the 7th switching element 41 may be maintained.

  Here, as an example, the case where the high-side sixth switching element 37 is kept on will be described with reference to FIG.

  As shown in FIG. 3A, the fifth switching element 35, the seventh switching element 41, and the eighth switching element 43 are in the off state. Accordingly, parasitic diodes in these switching elements are effective. In this state, when the first switching element 15 to the fourth switching element 23 perform an on / off operation, a voltage is generated across the secondary winding 47 in response to the on / off operation. Here, in the state of FIG. 3A, it is assumed that a positive voltage is generated on the upper side of the secondary winding 47, that is, on the second capacitor 45 side. In this case, a current flows from the positive voltage side of the secondary winding 47 as shown by a thick arrow in FIG. Specifically, a current flows from the positive voltage side of the secondary winding 47 to the sixth switching element 37 via the second capacitor 45 and the parasitic diode of the fifth switching element 35. Here, since the sixth switching element 37 is kept on, the current reaches the secondary winding 47 via the connection point between the sixth switching element 37 and the eighth switching element 43. The second capacitor 45 is charged through such a current path. Then, a positive voltage is generated on the secondary winding 47 side of the second capacitor 45. Further, the absolute value of the voltage across the second capacitor 45 at this time is substantially equal to the absolute value of the voltage across the secondary winding 47 as in the case of FIG.

  In this state, when the on / off state of the first switching element 15 to the fourth switching element 23 is reversed, the sign of the voltage generated in the secondary winding 47 is reversed as shown in FIG. Therefore, in the series circuit of the secondary winding 47 and the second capacitor 45, a sum of voltages at both ends of the secondary winding 47 and the second capacitor 45 is generated. Accordingly, current flows from the secondary winding 47 to the second input / output terminal 33 through the sixth switching element 37 as indicated by the thick arrows in FIG. Although not shown in FIG. 3B, this current flows to the battery 57 to charge the battery, and from the ground to the second capacitor 45 through the second ground terminal 39 and the parasitic diode of the seventh switching element 41. Take the route to reach. From these things, as in the case of FIG. 2, between the second input / output terminal 33 and the second ground terminal 39, the sum of the voltages across the secondary winding 47 and the second capacitor 45, That is, since the second capacitor 45 has a voltage that is substantially equal to that of the secondary winding 47, a voltage that is approximately twice the voltage generated in the secondary winding 47 is generated. Therefore, it is possible to output a double voltage with a simple circuit configuration that only maintains the high-side sixth switching element 37 in the ON state.

  Similarly, even if only the fifth switching element 35 or the seventh switching element 41 is maintained in an ON state, the voltage doubled voltage can be increased with a simple circuit configuration only in the current flow path different from those in FIGS. Can be obtained. Therefore, the control circuit 49 performs control so that any one of the fifth switching element 35, the sixth switching element 37, the seventh switching element 41, and the eighth switching element 43 is maintained in the on state when obtaining the double voltage. do it.

  Next, a case where power is supplied from the second input / output terminal 33 and the second ground terminal 39 to the first input / output terminal 13 and the first ground terminal 19 in the configuration of FIG. 1 will be described. This corresponds to, for example, the case where the DC / DC converter 11 is applied to a backup power source or the like that can switch and output the electric power stored in the battery 57 to a voltage corresponding to the standard of the system power source. Here, specifically, an example will be described in which the power of the battery 57 charged to 200V is output to an AC 100V system or an AC 200V system power supply. At this time, the output of the DC / DC converter 11 is input to a DC / AC inverter (not shown) for AC conversion. The input voltage to this DC / AC inverter is assumed to be 190 V DC for the AC 100 V system and 380 V DC for the AC 200 V system. Therefore, the DC / DC converter 11 is configured to convert the voltage (200V) of the battery 57 into 190V or 380V and output the voltage.

  In the case of the above operating conditions, when the voltage doubler control is not performed, the DC / DC converter 11 performs an operation of stepping down 200V to 190V. Therefore, the step-down ratio of the transformer 29 is 190V / 200V = 0.95. Therefore, the turns ratio of the primary winding 31 and the secondary winding 47 of the transformer 29 is set to 0.95. With this configuration, when voltage doubler control is performed, the DC / DC converter 11 can output 200 V × 0.95 × 2 = 380 V.

  Next, a specific operation will be described. The selection of whether the first input / output terminal voltage V1 output from the first input / output terminal 13 of the DC / DC converter 11 is set to 190V or 380V is manually issued to the control circuit 49 by the user. The voltage of the system power supply on the first input / output terminal 13 side before the control circuit 49 operates the DC / DC converter 11 is detected, and the DC / DC converter can be switched to any standard system power supply. 11 may be determined and switched automatically.

  First, the case where the second input / output terminal voltage V2 (200V), which is the voltage of the battery 57, is stepped down to 190V and output from the first input / output terminal 13 will be described.

  Since this operation is a step-down operation from the second input / output terminal 33 to the first input / output terminal 13, the DC / DC converter 11 performs a normal operation. Specifically, the control circuit 49 first turns off all of the first switching element 15 to the fourth switching element 23 to configure a bridge rectifier circuit using each parasitic diode. In this state, the control circuit 49 adjusts the time ratio of the fifth switching element 35 to the eighth switching element 43 so that the first input / output terminal voltage V1 becomes a desired voltage (190 V in this case), and performs on / off control. To do. As a result, since the step-down ratio of the transformer 29 is 0.95 as described above, if the battery 57 is fully charged (200V), the duty ratio is about 50%, and the voltage of 190V is the first input / output. Output from terminal 13.

  The above operation is the same as the step-down operation in a normal bidirectional DC / DC converter.

  Next, a case where the second input / output terminal voltage V2 (200V) is doubled and output from the first input / output terminal 13 as 380V will be described. First, the control circuit 49 performs control so that any one of the first switching element 15 to the fourth switching element 23 is turned on and the others are turned off. Then, the control circuit 49 performs on / off control of the fifth switching element 35 to the eighth switching element 43. At this time, since any one of the first switching element 15 to the fourth switching element 23 is on, the first capacitor 25 is charged in the same manner as in FIG. 2A or FIG. The electric power is discharged from the series circuit of the first capacitor 25 and the primary winding 31 in the same manner as in b) or FIG. Therefore, as described in FIGS. 2 and 3, the voltage output from the first input / output terminal 13 is a double voltage, specifically, 380V, which is twice the normal output (190V) described above. Is output.

  With such an operation, even when power is supplied from the second input / output terminal 33 and the second ground terminal 39 to the first input / output terminal 13 and the first ground terminal 19, the first switching element 15 performs the fourth switching. By simply turning on one of the elements 23, a double voltage can be easily obtained with a simple configuration. Therefore, the DC / DC converter 11 can be applied to a backup power source that can be switched to a voltage corresponding to the standard of the system power source and output with a simple circuit configuration even in a region where the standard of the system power source is different.

  2 and 3, when the control circuit 49 obtains a double voltage from the first input / output terminal 13 to the second input / output terminal 33, any one of the fifth switching element 35 to the eighth switching element 43 is It has been described that the control should be performed so as to maintain the on state. For the same reason, when the control circuit 49 obtains a voltage doubler from the second input / output terminal 33 to the first input / output terminal 13, any one of the first switching element 15 to the fourth switching element 23 is turned on. What is necessary is just to make it have the control state controlled so that it may maintain.

  With the above configuration and operation, when the control circuit 49 outputs a voltage from the first input / output terminal 13 to the second input / output terminal 33, any one of the fifth switching element 35 to the eighth switching element 43 is turned on. By having a control state in which control is performed to maintain the state, when the charged second capacitor 45 is discharged, the series circuit including the second capacitor 45 and the secondary winding 47 outputs a double voltage. Therefore, it is possible to obtain the DC / DC converter 11 that does not require a circuit configuration for obtaining a double voltage and can obtain a double voltage with a simple configuration. Similarly, when the control circuit 49 outputs a voltage from the second input / output terminal 33 to the first input / output terminal 13, any one of the first switching element 15 to the fourth switching element 23 maintains the ON state. By having the control state to be controlled as described above, when the charged first capacitor 25 is discharged, the series circuit including the first capacitor 25 and the primary winding 31 outputs a double voltage. Therefore, it is possible to obtain the DC / DC converter 11 that does not require a circuit configuration for obtaining a double voltage and can obtain a double voltage with a simple configuration.

(Embodiment 2)
Since the configuration of DC / DC converter 11 in the second embodiment is the same as that of FIG. 1 of the first embodiment, detailed description thereof is omitted. That is, since the feature of the second embodiment is the operation, the feature operation will be described below.

  In FIG. 1, when the control circuit 49 outputs a voltage from the first input / output terminal 13 to the second input / output terminal 33, the fifth switching element 35, the sixth switching element 37, the seventh switching element 41, or the Among the eight switching elements 43, the one that has not been maintained in the on state last time is selected, and has a control state in which control is performed to maintain the on state. When the voltage is output to the terminal 13, the first switching element 15, the second switching element 17, the third switching element 21, or the fourth switching element 23 is selected that has not maintained the on state last time. Thus, the control state is maintained so as to maintain the ON state.

  As a result, when the voltage doubler is output, the switching elements that maintain the ON state are not concentrated on a specific element, and the life of the switching elements can be made uniform. As a result, a double voltage can be obtained with a simple configuration, and the DC / DC converter 11 having high reliability can be realized.

  Hereinafter, the characteristic operation in the second embodiment will be described in detail with reference to FIG.

  First, regarding the operation when the double voltage is not output, even when outputting from the first input / output terminal 13 to the second input / output terminal 33, Even at the time of output, since it is the same as in the first embodiment, detailed description thereof is omitted.

  Next, a case where the voltage doubler operation is performed will be described.

  First, when the battery 57 is charged by outputting a double voltage from the first input / output terminal 13 to the second input / output terminal 33, the control circuit 49 turns on the eighth switching element 43, for example, as shown in FIG. maintain. Thereafter, when the battery 57 reaches the full charge voltage (200 V), the control circuit 49 determines that the full charge is reached from the detected value of the second input / output terminal voltage V2. Then, the DC / DC converter 11 is stopped.

  Next, the power of the battery 57 is consumed by a load (not shown). The load is electrically connected to the battery 57 on the assumption that it is driven by a DC power source. Alternatively, since the DC / DC converter 11 in FIG. 1 can exchange power in both directions, the load is electrically connected to the DC power supply 51 side via the DC / DC converter 11 or is electrically connected to the end thereof. It may be a load driven by AC power through the DC / AC inverter.

  After the power of the battery 57 is consumed, the DC / DC converter 11 operates to charge the battery 57 again. In this case, in order to obtain a voltage doubler, the control circuit 49 replaces the eighth switching element 43 previously maintained in an on state in order to obtain a voltage doubler, with the three switching elements (first The seventh switching element 41 which is one of the five switching elements 35 to the seventh switching element 41) is selected. And it controls so that the ON state of the 7th switching element 41 may be maintained.

  Then, when the next double voltage is obtained, the sixth switching element 37 is selected, and when the next double voltage is obtained, the fifth switching element 35 is selected. To select a switching element.

  As described above, at the start of the voltage doubler operation, the control circuit 49 performs control to select one of the switching elements that have not maintained the on state last time and maintain the on state. As a result, the current flowing from the fifth switching element 35 to the eighth switching element 43 can be equalized. That is, for example, as indicated by a thick arrow in FIG. 2A, current always flows through both the seventh switching element 41 and the eighth switching element 43 when the second capacitor 45 is charged. There is almost no. However, as indicated by the thick arrow in FIG. 2B, when the series circuit of the second capacitor 45 and the secondary winding 47 is discharged, current flows only through the eighth switching element 43 in the on state, Since the cathode side voltage of the parasitic diode is high, the switching element 41 is turned off and no current flows. Therefore, if the control is performed so that only the eighth switching element 43 is always in the ON state during the voltage doubler operation, the deterioration is faster than the seventh switching element 41 depending on the magnitude of the current and the electrical specifications of the eighth switching element 43. May lead to end of life. Therefore, in this case, in the second embodiment, any one of the fifth switching element 35 to the eighth switching element 43 to be turned on is selected during the voltage doubler operation. As a result, the lifetime of any switching element can be equalized, so that high reliability can be obtained.

  In the above description, the control circuit 49 circulates in this order from the eighth switching element 43 to the fifth switching element 35 and selects the one that maintains the ON state. It is not limited. In other words, the circulation may be selected in the reverse order or may be selected in the order in which the circulation is not performed. However, the opportunity to maintain the ON state is selected to be as uniform as possible in each switching element.

  In addition, when the period during which each switching element is maintained in an on-state is different, that is, when the on-period of a certain switching element is longer than the on-period of another switching element, the other switching element is turned on accordingly. May be increased. Thus, the control circuit 49 can obtain higher reliability of each switching element by controlling the total period of the ON state to be as uniform as possible in each switching element.

  In the above description, the example in which the operation of the DC / DC converter 11 is stopped when the battery 57 reaches full charge is described. However, this is limited to the operation of stopping the DC / DC converter 11 after full charge. is not. That is, depending on the type and state of the battery 57, the voltage of the battery 57 may decrease due to natural discharge. Therefore, even if the battery 57 reaches full charge, the control circuit 49 maintains the DC / DC voltage so as to maintain the voltage. The DC converter 11 may continue to operate. Also in this case, since a double voltage is necessary, the control circuit 49 continues to maintain the ON state of any one of the fifth switching element 35 to the eighth switching element 43. When the battery 57 consumes power by the load, the control circuit 49 stops the operation for maintaining the full charge voltage of the battery 57. Therefore, regardless of the operation of the DC / DC converter 11 after full charge, when the battery 57 is discharged and then recharged, the control circuit 49 includes the fifth switching element 35 to the eighth switching element 43. What is necessary is just to control to select the thing which has not maintained the ON state last time and to turn it on.

  Next, a case where a double voltage is output from the second input / output terminal 33 to the first input / output terminal 13 will be described. In this case, instead of the fifth switching element 35 to the eighth switching element 43 described above, the first switching element 15 to the fourth switching element 23 that are not in the previous ON state are selected and turned on. Therefore, in the above description, the fifth switching element 35 to the eighth switching element 43 may be replaced with the first switching element 15 to the fourth switching element 23, respectively. That is, at the start of the voltage doubler operation, the control circuit 49 selects one of the first switching element 15 to the fourth switching element 23 that has not been in the on state last time, and this time is in the on state. I do. The control circuit 49 sequentially performs such operations at the start of the voltage doubler operation.

  The details of such an operation and the specific effect of the obtained second embodiment (high reliability due to equalization of the lifetime of the first switching element 15 to the fourth switching element 23) are described above. To the operation of the eighth switching element 43.

  With the above-described configuration and operation, when the voltage doubler is output, the switching elements that maintain the on-state are not concentrated on a specific element, and the life of the switching elements can be made uniform. As a result, a double voltage can be obtained with a simple configuration, and the DC / DC converter 11 having high reliability can be realized.

(Embodiment 3)
FIG. 4 is a block circuit diagram of the DC / DC converter according to Embodiment 3 of the present invention. 4, the same components as those in FIG. 1 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In FIG. 4, the DC / DC converter 11 includes a first switching element 15 and a second switching element 17 whose one ends are electrically connected to the input terminal 62. The DC / DC converter 11 includes a third switching element 21 that is electrically connected between the other end of the first switching element 15 and the first ground terminal 19. Further, the DC / DC converter 11 includes a fourth switching element 23 that is electrically connected between the other end of the second switching element 17 and the first ground terminal 19. The DC / DC converter 11 includes a first capacitor 25 between the connection point of the first switching element 15 and the third switching element 21 and the connection point of the second switching element 17 and the fourth switching element 23. A primary winding 31 of a transformer 29 that is electrically connected via the wiring. The DC / DC converter 11 further includes a first diode 65 and a second diode 67 whose cathodes are electrically connected to the output terminal 63. In the DC / DC converter 11, the cathode is electrically connected to either the anode of the first diode 65 or the anode of the second diode 67, and the anode is electrically connected to the second ground terminal 39. The third diode 69 is provided. The DC / DC converter 11 includes a fourth diode 71 electrically connected between the anode of the first diode 65 or the anode of the second diode 67 and the second ground terminal 39. The DC / DC converter 11 includes a switch 73 that is electrically connected in parallel to any one of the first diode 65, the second diode 67, the third diode 69, and the fourth diode 71. In addition, the DC / DC converter 11 includes a secondary winding 47 of the transformer 29 that is electrically connected via the second capacitor 45 between the anode of the first diode 65 and the anode of the second diode 67. . The DC / DC converter 11 includes a first switching element 15, a second switching element 17, a third switching element 21, a fourth switching element 23, and a control circuit 49 connected to the switch 73. The control circuit 49 has a control state in which the switch 73 is controlled to maintain the on state when the voltage is output from the input terminal 62 to the output terminal 63.

  As a result, the control circuit 49 controls the switch 73 to maintain the ON state when outputting the double voltage from the input terminal 62 to the output terminal 63. As a result, when the charged second capacitor 45 is discharged, the series circuit including the second capacitor 45 and the secondary winding 47 outputs a double voltage. Therefore, the DC / DC converter 11 capable of obtaining a double voltage with a simple circuit configuration in which only the switch 73 is provided can be obtained.

  Hereinafter, the detailed configuration of the DC / DC converter 11 according to the third embodiment will be described with reference to FIG.

  First, the DC / DC converter 11 of FIG. 4 replaces the fifth switching element 35 to the eighth switching element 43 in the configuration of FIG. 1 with the first diode 65 to the fourth diode 71, respectively, and is in parallel with the fourth diode 71. The switch 73 is provided. Therefore, in the DC / DC converter 11 according to the third embodiment, the configuration in which the switch 73 is provided in parallel with the fourth diode 71 corresponds to the eighth switching element 43, but the fifth switching element 35 to the seventh switching element 41. Therefore, power conversion from the battery 57 side to the DC power source 51 side cannot be performed. Therefore, in the third embodiment, the unidirectional DC / DC converter 11 performs voltage conversion from the input terminal 62 to the output terminal 63.

  First, in FIG. 4, the input terminal 62 is electrically connected to the DC power source 51. Therefore, the control circuit 49 has a function of detecting and taking in the input terminal voltage V3. Similarly, the output terminal 63 in FIG. 4 is electrically connected to the battery 57. Therefore, the control circuit 49 has a function of detecting and taking in the output terminal voltage V4.

  Next, a series circuit of a first diode 65 and a third diode 69 is electrically connected between the output terminal 63 and the second ground terminal 39. At this time, the cathode of the first diode 65 is connected to the output terminal 63, the cathode of the third diode 69 is connected to the anode of the first diode 65, and the second ground terminal 39 is connected to the anode of the third diode 69. The One end of the second capacitor 45 is electrically connected to a connection point in the series circuit of the first diode 65 and the third diode 69.

  A series circuit of the second diode 67 and the fourth diode 71 is electrically connected between the output terminal 63 and the second ground terminal 39. At this time, the cathode of the second diode 67 is electrically connected to the output terminal 63, the cathode of the fourth diode 71 is electrically connected to the anode of the second diode 67, and the second ground terminal 39 is electrically connected to the anode of the fourth diode 71, respectively. Connected to. One end of the secondary winding 47 is electrically connected to a connection point in the series circuit of the second diode 67 and the fourth diode 71. Further, a switch 73 is electrically connected to both ends of the fourth diode 71. Here, the switch 73 may be any switch that can be turned on and off in accordance with an external signal. For example, a semiconductor switch or a relay can be applied. In the third embodiment, a semiconductor switch element (for example, FET) including the fourth diode 71 as a parasitic diode is used as the switch 73. As a result, it is not necessary to provide the fourth diode 71 separately, so that the circuit configuration can be further simplified.

  The configuration other than the above is the same as in FIG. 1 of the first embodiment.

  Next, the operation of such a DC / DC converter 11 will be described.

  First, regarding switching to the double voltage of the DC / DC converter 11, as described in the first and second embodiments, the control circuit 49 automatically detects the voltage of the DC power supply 51 (here, the input terminal voltage V3). The user manually instructs the control circuit 49 from the outside.

  Next, when the voltage doubler is not output, the control circuit 49 maintains the switch 73 in the OFF state. Thereby, a bridge rectifier circuit is formed by the first diode 65 to the fourth diode 71. Therefore, the DC voltage rectified by the first diode 65 to the fourth diode 71 is output from the output terminal 63. Since the operation when this voltage doubler is not output is substantially the same as in the first embodiment, detailed description thereof is omitted.

  Next, a case where the voltage doubler operation is performed will be described.

  First, the control circuit 49 maintains the switch 73 in the on state. This state is equivalent to FIG. Therefore, when the control circuit 49 performs on / off control of the first switching element 15 to the fourth switching element 23, the charge / discharge operation of the second capacitor 45 described with reference to FIG. 2 occurs, and a double voltage is output from the output terminal 63. The Therefore, even in the unidirectional DC / DC converter 11, a switch 73 is added or a semiconductor switch element including the fourth diode 71 as a parasitic diode is used as the switch 73, and the above operation is performed. A double voltage can be output.

  In FIG. 4, the switch 73 is a semiconductor switch element including the fourth diode 71 as a parasitic diode. However, the switch 73 includes the first diode 65, the second diode 67, or the third diode 69. One of the above may be a semiconductor switch element including a parasitic diode, and the fourth diode 71 may not include the switch 73. In this case, the same effect as described above can be obtained. However, the switch 73 that is electrically connected in parallel to one of the first diode 65 to the third diode 69 is not limited to the semiconductor switch. It may be one that can be turned on / off in response (for example, a relay).

  As in the second embodiment, the operation of the DC / DC converter 11 after the battery 57 is fully charged may be stopped by the control circuit 49 or the full charge voltage of the battery 57 may be set. The on / off control from the first switching element 15 to the fourth switching element 23 may be continued with the switch 73 being turned on so as to be maintained.

  With the above configuration and operation, the control circuit 49 performs control so that the switch 73 is kept on when the double voltage is output from the input terminal 62 to the output terminal 63. As a result, when the charged second capacitor 45 is discharged, the series circuit including the second capacitor 45 and the secondary winding 47 outputs a double voltage. Therefore, the DC / DC converter 11 capable of obtaining a double voltage with a simple circuit configuration in which only the switch 73 is provided can be obtained.

  In the first to third embodiments, the case where the DC / DC converter 11 is used as a battery charger for an electric vehicle and a backup power source has been described. However, the present invention is not limited thereto, and the electric vehicle or plug-in is not limited thereto. Other applications that need to comply with system power supply standards, such as for vehicle chargers / dischargers such as hybrid vehicles, uninterruptible power supplies, peak shift power supplies, etc., and general DC / DC converters that require double voltage switching Also, the configurations of the first to third embodiments can be applied.

  The DC / DC converter according to the present invention is capable of switching voltage doubles with a simple configuration. Therefore, the DC / DC converter is particularly useful as a DC / DC converter for a charger connected to a system power source that requires voltage doubler switching.

11 DC / DC converter 13 First input / output terminal 15 First switching element 17 Second switching element 19 First ground terminal 21 Third switching element 23 Fourth switching element 25 First capacitor 29 Transformer 31 Primary winding 33 Second Input / output terminal 35 Fifth switching element 37 Sixth switching element 39 Second ground terminal 41 Seventh switching element 43 Eighth switching element 45 Second capacitor 47 Secondary winding 49 Control circuit 62 Input terminal 63 Output terminal 65 First diode 67 Second diode 69 Third diode 71 Fourth diode 73 Switch

Claims (4)

A first switching element having one end electrically connected to the first input / output terminal, and a second switching element;
A third switching element electrically connected between the other end of the first switching element and a first ground terminal;
A fourth switching element electrically connected between the other end of the second switching element and the first ground terminal;
A transformer electrically connected via a first capacitor between a connection point of the first switching element and the third switching element and a connection point of the second switching element and the fourth switching element. A primary winding;
A fifth switching element having one end electrically connected to the second input / output terminal, and a sixth switching element;
A seventh switching element electrically connected between the other end of the fifth switching element and the second ground terminal;
An eighth switching element electrically connected between the other end of the sixth switching element and the second ground terminal;
The transformer electrically connected via a second capacitor between a connection point of the fifth switching element and the seventh switching element and a connection point of the sixth switching element and the eighth switching element. Secondary winding of
Connected to the first switching element, the second switching element, the third switching element, the fourth switching element, the fifth switching element, the sixth switching element, the seventh switching element, and the eighth switching element. A control circuit,
When the control circuit outputs a voltage from the first input / output terminal to the second input / output terminal, the fifth switching element, the sixth switching element, the seventh switching element, or the eighth switching element A control state in which any one of is controlled to maintain the ON state,
When outputting a voltage from the second input / output terminal to the first input / output terminal, any one of the first switching element, the second switching element, the third switching element, or the fourth switching element is A DC / DC converter having a control state for controlling to maintain an ON state. When the control circuit outputs a voltage from the first input / output terminal to the second input / output terminal, the fifth switching element, the sixth switching element, the seventh switching element, or the eighth switching element Among them, the last time the one that has not maintained the on-state is selected, and the control state is controlled to maintain the on-state,
When outputting a voltage from the second input / output terminal to the first input / output terminal, the previous one of the first switching element, the second switching element, the third switching element, or the fourth switching element, 2. The DC / DC converter according to claim 1, wherein the DC / DC converter according to claim 1 has a control state in which the one that does not maintain the on state is selected and control is performed so as to maintain the on state. A first switching element having one end electrically connected to the input terminal, and a second switching element;
A third switching element electrically connected between the other end of the first switching element and a first ground terminal;
A fourth switching element electrically connected between the other end of the second switching element and the first ground terminal;
A transformer electrically connected via a first capacitor between a connection point of the first switching element and the third switching element and a connection point of the second switching element and the fourth switching element. A primary winding;
A first diode having a cathode electrically connected to the output terminal, and a second diode;
A third diode in which a cathode is electrically connected to either the anode of the first diode or the anode of the second diode, and the anode is electrically connected to a second ground terminal;
A fourth diode electrically connected between the anode of the first diode or the anode of the second diode and the second ground terminal;
A switch electrically connected in parallel to any one of the first diode, the second diode, the third diode, or the fourth diode;
A secondary winding of the transformer electrically connected via a second capacitor between the anode of the first diode and the anode of the second diode;
A control circuit connected to the first switching element, the second switching element, the third switching element, the fourth switching element, and the switch;
The DC / DC converter having a control state in which the control circuit controls the switch to maintain an ON state when a voltage is output from the input terminal to the output terminal. 4. The DC / DC converter according to claim 3, wherein the switch is a semiconductor switch element including any one of the first diode, the second diode, the third diode, and the fourth diode as a parasitic diode.

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