JP6183517B1 - Buck-boost converter, computer program, and control method for buck-boost converter - Google Patents

Abstract

A buck-boost converter, a computer program, and a control method for the buck-boost converter that can reduce switching loss even in boost conversion. A control unit turns on a first low-voltage side switching device during a boost conversion to operate in a first mode in which a current flows through a second inductor, and turns off the first low-voltage side switching device after the first mode. When the first inductor, the second inductor, and the capacitor are operated in the second mode in which the resonance current flows, and the voltage of the first low-voltage side switching device becomes a predetermined voltage threshold value or less in the second mode, the first low-voltage side switching The device is turned on to shift to the first mode. [Selection] Figure 1

Description

  The present invention relates to a step-up / down converter, a computer program for controlling the step-up / down converter, and a method for controlling the step-up / down converter.

  In recent years, mounting on a 48V system in an automobile has been studied. The 48V system consists of a small-capacity battery, DC / DC converter, motor / alternator, etc., and generates electricity with the alternator using deceleration energy. The motor assists the engine with the battery power during acceleration, which can improve fuel efficiency. is there.

  For this reason, the vehicle is equipped with a DC / DC converter that converts a DC voltage between 48V and the conventional 12V. In recent years, there is a high demand for miniaturization of devices, and the driving frequency of DC / DC converters is increasing due to miniaturization of passive elements. However, when the drive frequency is increased, the switching loss of a switching device such as an IGBT (Insulated Gate Bipolar Transistor) or FET increases. Therefore, a step-down converter that performs switching at zero voltage to reduce switching loss is disclosed (see Patent Document 1).

JP 2002-262552 A

  However, in the conventional DC / DC converter as in Patent Document 1, when performing step-down conversion, switching at zero voltage can be performed to reduce switching loss, but the case of performing step-up conversion is considered. Not.

  The present invention has been made in view of such circumstances, and a step-up / down conversion device that can reduce switching loss even in the case of step-up conversion, a computer program for controlling the step-up / down conversion device, and the step-up / down conversion device. It aims at providing the control method of a pressure converter.

  A step-up / down converter according to an embodiment of the present invention includes a high-voltage side switching device and a first low-voltage side switching device connected in series via a first inductor, the first inductor and the first low-voltage side switching device. A second inductor having one end connected to the connection point; a capacitor connected in parallel to the first low-voltage side switching device; and a predetermined operation mode by turning on / off the high-voltage side switching device and the first low-voltage side switching device. A step-up / down converter including a control unit that is operated at a step of outputting a current through the second inductor at the time of step-down conversion, and the control unit turns on the first low-voltage side switching device at the time of step-up conversion. The first inductor is operated in a first mode in which a current is passed through the second inductor, and the first low voltage is applied after the operation in the first mode The second switching device is turned off to operate in a second mode in which a resonance current is flown by the first inductor, the second inductor, and the capacitor, and the voltage of the first low-voltage switching device is a predetermined voltage threshold value in the second mode. When it becomes below, this 1st low voltage | pressure side switching device is turned ON, and it transfers to the said 1st mode.

  A computer program according to an embodiment of the present invention includes a high-voltage side switching device and a first low-voltage side switching device connected in series via a first inductor to the computer, the first inductor and the first low-voltage side switching. A computer program for controlling a step-up / down converter comprising a second inductor having one end connected to a connection point of a device and a capacitor connected in parallel to the first low-voltage side switching device. Sometimes outputting a current through the second inductor, causing the computer to function as a controller that turns on and off the high-voltage side switching device and the first low-voltage side switching device to operate in a predetermined operation mode, During the boost conversion, the first low pressure side switch The device is turned on to operate in a first mode in which current flows through the second inductor, and after the operation in the first mode, the first low-voltage side switching device is turned off to turn the first inductor, the second inductor, and the When operating in a second mode in which a resonant current is passed by a capacitor, and the voltage of the first low-voltage side switching device becomes 0 in the second mode, the first low-voltage side switching device is turned on to enter the first mode. Execute the migration process.

  A method for controlling a step-up / down converter according to an embodiment of the present invention includes a high-voltage side switching device and a first low-voltage side switching device connected in series via a first inductor, the first inductor, and the first low-voltage converter. A step-up / down converter apparatus control method comprising: a second inductor having one end connected to a connection point of a side switching device; and a capacitor connected in parallel to the first low-voltage side switching device. Through which the control unit operates in a predetermined operation mode by turning on / off the high-voltage side switching device and the first low-voltage side switching device, and the control unit performs the first low-voltage side switching during boost conversion. The device is turned on to operate in a first mode in which current flows through the second inductor, and the operation in the first mode is performed. Later, the first low-voltage switching device is turned off to operate in a second mode in which a resonance current is flown by the first inductor, the second inductor, and the capacitor. In the second mode, the voltage of the first low-voltage switching device is When becomes 0, the first low-voltage side switching device is turned on to shift to the first mode.

  According to the present invention, switching loss can be reduced even in the case of step-up conversion.

It is explanatory drawing which shows an example of the circuit structure of the buck-boost converter of this Embodiment. It is explanatory drawing which shows an example of state U1 of the pressure | voltage rise operation | movement of the step-up / step-down converter of this Embodiment. It is explanatory drawing which shows an example of state U2 of the pressure | voltage rise operation | movement of the step-up / step-down converter of this Embodiment. It is explanatory drawing which shows an example of the state U3 of the pressure | voltage rise operation | movement of the buck-boost converter of this Embodiment. It is explanatory drawing which shows an example of state U4 of the pressure | voltage rise operation | movement of the step-up / step-down converter of this Embodiment. It is explanatory drawing which shows an example of the state U5 of the pressure | voltage rise operation of the step-up / step-down converter of this Embodiment. It is explanatory drawing which shows an example of the state U6 of the pressure | voltage rise operation of the step-up / step-down converter of this Embodiment. It is explanatory drawing which shows an example of the waveform of each part at the time of the pressure | voltage rise operation of the buck-boost converter of this Embodiment. It is explanatory drawing which shows the other example of the circuit structure of the step-up / step-down converter of this Embodiment. It is explanatory drawing which shows an example of the pressure | voltage rise operation | movement at the time of the light load of the step-up / step-down converter of this Embodiment. It is explanatory drawing which shows an example of state D1 of the pressure | voltage fall operation | movement of the buck-boost converter of this Embodiment. It is explanatory drawing which shows an example of state D2 of the pressure | voltage fall operation | movement of the buck-boost converter of this Embodiment. It is explanatory drawing which shows an example of the state D3 of the pressure | voltage fall operation | movement of the buck-boost converter of this Embodiment. It is explanatory drawing which shows an example of state D4 of the pressure | voltage fall operation | movement of the step-up / step-down converter of this Embodiment. It is a flowchart which shows the 1st example of the process sequence of the pressure | voltage rise operation | movement of the step-up / step-down converter of this Embodiment. It is a flowchart which shows the 2nd example of the process sequence of the pressure | voltage rise operation of the buck-boost converter of this Embodiment.

[Description of Embodiment of Present Invention]
A step-up / down converter according to an embodiment of the present invention includes a high-voltage side switching device and a first low-voltage side switching device connected in series via a first inductor, the first inductor and the first low-voltage side switching device. A second inductor having one end connected to the connection point; a capacitor connected in parallel to the first low-voltage side switching device; and a predetermined operation mode by turning on / off the high-voltage side switching device and the first low-voltage side switching device. A step-up / down converter including a control unit that is operated at a step of outputting a current through the second inductor at the time of step-down conversion, and the control unit turns on the first low-voltage side switching device at the time of step-up conversion. The first inductor is operated in a first mode in which a current is passed through the second inductor, and the first low voltage is applied after the operation in the first mode. The second switching device is turned off to operate in a second mode in which a resonance current is flown by the first inductor, the second inductor, and the capacitor, and the voltage of the first low-voltage switching device is a predetermined voltage threshold value in the second mode. When it becomes below, this 1st low voltage | pressure side switching device is turned ON, and it transfers to the said 1st mode.

  A computer program according to an embodiment of the present invention includes a high-voltage side switching device and a first low-voltage side switching device connected in series via a first inductor to the computer, the first inductor and the first low-voltage side switching. A computer program for controlling a step-up / down converter comprising a second inductor having one end connected to a connection point of a device and a capacitor connected in parallel to the first low-voltage side switching device. Sometimes outputting a current through the second inductor, causing the computer to function as a controller that turns on and off the high-voltage side switching device and the first low-voltage side switching device to operate in a predetermined operation mode, During the boost conversion, the first low pressure side switch The device is turned on to operate in a first mode in which current flows through the second inductor, and after the operation in the first mode, the first low-voltage side switching device is turned off to turn the first inductor, the second inductor, and the When operating in a second mode in which a resonant current is passed by a capacitor, and the voltage of the first low-voltage side switching device becomes 0 in the second mode, the first low-voltage side switching device is turned on to enter the first mode. Execute the migration process.

  A method for controlling a step-up / down converter according to an embodiment of the present invention includes a high-voltage side switching device and a first low-voltage side switching device connected in series via a first inductor, the first inductor, and the first low-voltage converter. A step-up / down converter apparatus control method comprising: a second inductor having one end connected to a connection point of a side switching device; and a capacitor connected in parallel to the first low-voltage side switching device. Through which the control unit operates in a predetermined operation mode by turning on / off the high-voltage side switching device and the first low-voltage side switching device, and the control unit performs the first low-voltage side switching during boost conversion. The device is turned on to operate in a first mode in which current flows through the second inductor, and the operation in the first mode is performed. Later, the first low-voltage switching device is turned off to operate in a second mode in which a resonance current is flown by the first inductor, the second inductor, and the capacitor. In the second mode, the voltage of the first low-voltage switching device is When becomes 0, the first low-voltage side switching device is turned on to shift to the first mode.

  The control unit turns on the first low-voltage side switching device and operates in the first mode in which current flows through the second inductor during boost conversion. By turning on the first low-voltage side switching device, energy is stored in the second inductor.

  The control unit turns off the first low-voltage side switching device after the operation in the first mode, and operates in the second mode in which the resonance current from the first inductor, the second inductor, and the capacitor flows. By turning off the first low-voltage side switching device, the current flowing through the first low-voltage side switching device flows through a capacitor connected in parallel to the first low-voltage side switching device. 2 Resonant current with the inductor flows. And when the voltage of a capacitor rises, the resonant current by a 1st inductor, a 2nd inductor, and a capacitor flows.

  When the voltage of the first low-voltage side switching device becomes equal to or lower than a predetermined voltage threshold in the second mode, the control unit turns on the first low-voltage side switching device and shifts to the first mode. During operation in the aforementioned second mode, the voltage of the capacitor, that is, the voltage of the first low-voltage side switching device rises due to resonance and then drops. The voltage threshold can be set to, for example, 0V or a voltage near 0V. For example, since the first low voltage side switching device is turned on when the voltage of the first low voltage side switching device becomes 0 V, the switching loss represented by the voltage x current when the first low voltage side switching device is turned on is Can be reduced.

  In the step-up / down converter according to the embodiment of the present invention, the control unit causes a resonance current to flow through the second inductor and the capacitor in the second mode in a state where the high-voltage side switching device is off.

  In the step-up / down converter according to the embodiment of the present invention, the control unit is connected in parallel to the first low-voltage side switching device in the second mode when the first low-voltage side switching device is off. The resonance current is passed through the diode.

  The step-up / down converter according to the embodiment of the present invention includes a voltage detection unit that detects a voltage of the first low-voltage side switching device, and the control unit detects that the voltage detected by the voltage detection unit is equal to or lower than the voltage threshold value. If so, the first low-voltage side switching device is turned on to shift to the first mode.

  A voltage detection part detects the voltage of a 1st low voltage | pressure side switching device. When the voltage detected by the voltage detection unit is equal to or lower than the voltage threshold, the control unit turns on the first low-voltage side switching device to shift to the first mode.

  Since the first low voltage side switching device is turned on when the voltage of the first low voltage side switching device is equal to or lower than the voltage threshold, the switching loss represented by the voltage x current when the first low voltage side switching device is turned on is Can be reduced.

[Details of the embodiment of the present invention]
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments. FIG. 1 is an explanatory diagram showing an example of the circuit configuration of the buck-boost converter according to the present embodiment. The step-up / down converter according to the present embodiment includes terminals H and G on the high voltage side and terminals L and G on the low voltage side. The terminals H and G are connected to a battery having a relatively high voltage such as a lithium ion battery (for example, a voltage higher than that of a 12V battery), and the terminals L and G are, for example, a lead storage battery. A battery having a relatively low voltage (for example, 12V) can be connected. In the following description, the switching device is described as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), but the switching device is not limited to a MOSFET, and may be a device such as an IGBT (Insulated Gate Bipolar Transistor).

  The drain of the high-voltage side switching device 10 is connected to the terminal H of the step-up / down converter, and one end of the first inductor 1 is connected to the source of the high-voltage side switching device 10. The other end of the first inductor 1 is connected to the drain of the low-voltage side switching device 20, and the source of the low-voltage side switching device 20 is connected to the terminal G. A capacitor 3 is connected in parallel between the drain and source of the low-voltage side switching device 20. One end of the second inductor 2 is connected to the connection point between the first inductor 1 and the low voltage side switching device 20, and the other end of the second inductor 2 is connected to the terminal L. A capacitor 4 is connected between the terminals H and G, and a capacitor 5 is connected between the terminals L and G.

  The control unit 50 controls on / off of the high-voltage side switching device 10 and the low-voltage side switching device 20. Further, the control unit 50 operates the step-up / down converter in each operation mode described later. Further, the control unit 50 functions as a voltage detection unit that detects the voltage between the drain and the source of the low-voltage side switching device 20, that is, the voltage across the capacitor 3.

  In other words, the step-up / down converter includes a connection point between the high-voltage side switching device 10 and the first low-voltage side switching device 20 connected in series via the first inductor 1, and the first inductor 1 and the first low-voltage side switching device 20. The second inductor 2 having one end connected to the capacitor, the capacitor 3 connected in parallel to the first low-voltage side switching device 20, the high-voltage side switching device 10 and the first low-voltage side switching device 20 are turned on / off, and a predetermined operation mode is established. And a control unit 50 to be operated.

  Next, the boosting operation (boost conversion) of the buck-boost converter according to the present embodiment will be described. FIG. 2 is an explanatory diagram showing an example of the state U1 of the step-up operation of the step-up / step-down converter according to the present embodiment. The state U1 corresponds to the first mode. As shown in FIG. 2, the control unit 50 operates in the first mode in which the high-voltage side switching device 10 is turned off and the first low-voltage side switching device 20 is turned on to allow current to flow through the second inductor 2. By turning on the first low-voltage switching device 20, current flows from the terminals L and G via the second inductor 2 and the first low-voltage switching device 20, and energy is stored in the second inductor 2.

  FIG. 3 is an explanatory diagram illustrating an example of the state U2 of the boosting operation of the step-up / down converter according to the present embodiment. State U2 corresponds to the second mode. As shown in FIG. 3, after the operation in the first mode shown in FIG. 2, the control unit 50 turns off the first low-voltage side switching device 20. As a result, a current due to resonance between the second inductor 2 and the capacitor 3 flows. When the voltage of the capacitor 3 exceeds the voltage between the terminals L and G, the current flowing through the second inductor 2 starts to decrease.

  FIG. 4 is an explanatory diagram showing an example of the state U3 of the step-up operation of the step-up / step-down converter according to the present embodiment. State U3 also corresponds to the second mode. In the state shown in FIG. 3, when the voltage of the capacitor 3 rises due to resonance and the voltage of the capacitor 3 exceeds the voltage between the terminals H and G, the terminals H and G are passed through the high-voltage side switching device 10 as shown in FIG. A current flows through (load side) and shifts to resonance by the first inductor 1, the second inductor 2 and the capacitor 3. At this time, the control unit 50 turns on the high-voltage side switching device 10.

  FIG. 5 is an explanatory diagram showing an example of the state U4 of the step-up operation of the step-up / down converter according to the present embodiment. State U4 also corresponds to the second mode. The resonance of the first inductor 1, the second inductor 2, and the capacitor 3 reverses the direction of the current flowing through the capacitor 3, discharges the electric charge stored in the capacitor 3, and lowers the voltage of the capacitor 3. In this state, current flows to the terminals H and G (load side) through the high-voltage side switching device 10.

  FIG. 6 is an explanatory diagram showing an example of the state U5 of the step-up operation of the step-up / step-down converter according to the present embodiment. State U5 also corresponds to the second mode. When the voltage of the capacitor 3 decreases and reaches a predetermined voltage threshold value (for example, a value near 0 V), the diode of the first low-voltage side switching device 20 changes from the reverse bias state to the forward bias state, and the terminals H and G pass through the diode. Current flows through (load side). In the state shown in FIG. 6, the voltage between the drain and the source of the first low-voltage side switching device 20 is not more than a predetermined voltage threshold.

  FIG. 7 is an explanatory diagram showing an example of the state U6 of the step-up operation of the step-up / step-down converter according to the present embodiment. In the state U6, the first low-voltage side switching device 20 is turned on. Since the voltage between the drain and the source of the first low voltage side switching device 20 is equal to or lower than a predetermined voltage threshold, even when the first low voltage side switching device 20 is turned on, the first low voltage side switching device 20 is turned on. Switching loss expressed by voltage × current can be reduced. Further, by turning on the first low-voltage side switching device 20, current flows from the terminals L and G to the second inductor 2, and the current flowing to the terminals H and G disappears, and the first mode (see FIG. 2). Transition to state U1) shown.

  FIG. 8 is an explanatory diagram showing an example of the waveform of each part during the boosting operation of the buck-boost converter according to the present embodiment. In FIG. 8, the horizontal axis indicates time. The voltage waveform and current waveform of the second inductor 2, the voltage waveform and current waveform of the first low voltage side switching device 20, the voltage waveform and current waveform of the capacitor 3, the voltage waveform of the high voltage side switching device 10 and The current waveform, the voltage waveform of the first inductor 1 and the current waveform are shown.

  As shown in FIG. 8, it can be seen that in the state U <b> 1, a current flows through the second inductor 2 and energy is stored in the second inductor 2.

  In the state U <b> 2, the first low-voltage side switching device 20 is turned off from on, the current of the capacitor 3 increases, and the voltage of the capacitor 3 increases in a sinusoidal shape due to resonance with the second inductor 2.

  In the state U3, the high-voltage side switching device 10 is turned on from off, the voltage of the capacitor 3 exceeds the voltage between the terminals H and G, and the first inductor 1, the second inductor 2, and the capacitor 3 are passed through the high-voltage side switching device 10. A sinusoidal current due to resonance flows between the terminals H and G.

  In state U4, the voltage of capacitor 3 turns from increasing to decreasing and the voltage approaches zero.

  In the state U5, the voltage of the capacitor 3 becomes 0, and the voltage between the drain and source of the first low-voltage side switching device 20 also becomes 0.

  In the state U6, the first low-voltage switching device 20 is turned on from off. At this time, since the voltage between the drain and the source of the first low-voltage side switching device 20 is 0 V, the switching loss can be reduced even if the current of the first low-voltage side switching device 20 suddenly increases (see FIG. 8 and a portion indicated by a symbol A) After state U6, the state shifts to state U1.

  As described above, the control unit 50 operates in the second mode in which the first low voltage side switching device 20 is turned off after the first mode and the resonance current is generated by the first inductor 1, the second inductor 2, and the capacitor 3. By turning off the first low voltage side switching device 20, the current flowing through the first low voltage side switching device 20 flows through the capacitor 3 connected in parallel to the first low voltage side switching device 20. A resonance current flows between the capacitor 3 and the second inductor 2. And when the voltage of the capacitor 3 rises, the resonance current by the 1st inductor 1, the 2nd inductor 2, and the capacitor 3 flows.

  When the voltage of the first low-voltage side switching device 20 becomes equal to or lower than a predetermined voltage threshold in the second mode, the control unit 50 turns on the first low-voltage side switching device 20 and shifts to the first mode. During operation in the second mode described above, the voltage of the capacitor 3, that is, the voltage of the first low-voltage side switching device 20 rises due to resonance and then drops. For example, the voltage threshold value may be a voltage in the vicinity of 0V. For example, since the first low voltage side switching device 20 is turned on when the voltage of the first low voltage side switching device 20 is close to 0V, it is expressed as voltage × current when the first low voltage side switching device 20 is turned on. Switching loss can be reduced.

  In addition, the control unit 50 functions as a voltage detection unit, and detects the voltage between the drain and the source of the first low-voltage side switching device 20. When the detected voltage is equal to or lower than the voltage threshold, the control unit 50 turns on the first low-voltage side switching device 20 to shift to the first mode. Since the first low voltage side switching device 20 is turned on when the voltage of the first low voltage side switching device 20 is equal to or lower than the voltage threshold value, it is expressed as voltage × current when the first low voltage side switching device 20 is turned on. Switching loss can be reduced.

  FIG. 9 is an explanatory diagram showing another example of the circuit configuration of the step-up / down converter according to the present embodiment. The difference from the example shown in FIG. 1 is that in FIG. 9, a second low-voltage side switching device 30 connected in series to the high-voltage side switching device 10 is connected to the connection point between the high-voltage side switching device 10 and the first inductor 1. Prepare. FIG. 9 shows a state U7 of the boosting operation as the third mode.

  The controller 50 operates in the third mode in which the second low-voltage side switching device 30 is turned on in the state U4 (second mode) illustrated in FIG. When operating in the second mode in which the resonance current from the first inductor 1, the second inductor 2 and the capacitor 3 flows, the voltage of the capacitor 3 decreases after increasing, but when the voltage of the capacitor 3 does not decrease sufficiently By turning on the second low voltage side switching device 30, the charge of the capacitor 3 flows to the second low voltage side switching device 30 via the first inductor 1, and the voltage of the capacitor 3 is lowered to a predetermined voltage threshold value. Below.

  The controller 50 turns on the first low-voltage switching device 20 after the state U7 (third mode), and shifts to the state U5 illustrated in FIG. In the state U7 (third mode), since the voltage of the capacitor 3, that is, the voltage of the first low-voltage side switching device 20 has dropped below the voltage threshold, the voltage when the first low-voltage side switching device 20 is turned on × Switching loss expressed by current can be reduced.

  FIG. 10 is an explanatory diagram showing an example of a boosting operation at a light load of the step-up / down converter according to the present embodiment. The configuration of the step-up / down converter is the same as the configuration illustrated in FIG. When the load between the terminals H and G is a light load (for example, when the current value is small), the first low-voltage side switching device 20 is always turned off, and the second low-voltage side switching device 30 is connected to the second inductor 2 and the capacitor. ON / OFF is repeated at a frequency higher than the resonance frequency of 3.

  When the second low-voltage switching device 30 is on, current flows in the direction indicated by the solid line in FIG. 10, and energy is stored in the first inductor 1 and the second inductor 2. When the second low-voltage side switching device 30 is off, a current flows in a direction indicated by a broken line in FIG. 10 and a current is supplied to the load through the terminals H and G. When the load is light, the switching loss of the switching device can be suppressed.

  Next, the step-down operation of the buck-boost converter according to the present embodiment will be described. FIG. 11 is an explanatory diagram illustrating an example of a state D1 of the step-down operation of the step-up / down converter according to the present embodiment. In the state D1, the high voltage side switching device 10 is turned on, and the first low voltage side switching device 20 is turned off. The resonance current of the first inductor 1 and the capacitor 3 flows from the terminals H and G through the high voltage side switching device 10. Further, a current flows through the second inductor 2 to the terminals L and G (load side) according to the difference between the voltage between the terminals H and G and the voltage between the terminals L and G.

  FIG. 12 is an explanatory diagram showing an example of a state D2 of the step-down operation of the step-up / down converter according to the present embodiment. In the state D2, the high-voltage side switching device 10 remains on and the first low-voltage side switching device 20 remains off. In the state D2, the directions of the resonance currents of the first inductor 1 and the capacitor 3 are reversed, and the current flowing through the high-voltage side switching device 10 is reduced.

  FIG. 13 is an explanatory diagram illustrating an example of a state D3 of the step-down operation of the step-up / down converter according to the present embodiment. In the aforementioned state D2, when the current flowing through the high-voltage side switching device 10 becomes 0 or a small value close to 0, the high-voltage side switching device 10 is turned off to enter the state D3. In the state D3, the residual charge of the capacitor 3 is released to the terminals L and G side (load side), and the voltage of the capacitor 3 decreases.

  FIG. 14 is an explanatory diagram showing an example of a state D4 of the step-down operation of the step-up / down converter according to the present embodiment. In the state D4, the high voltage side switching device 10 remains off, and the first low voltage side switching device 20 is turned on. When the voltage of the capacitor 3 approaches 0 V, the diode of the first low-voltage side switching device 20 changes from reverse bias to forward bias, and current flows through the diode. Since the first low voltage side switching device 20 is turned on when the voltage between the drain and source of the first low voltage side switching device 20 becomes a low voltage of about 0V or 0V, the switching loss of the first low voltage side switching device 20 Can be reduced. Further, after the state D4, the state shifts to the state D1.

  Next, the processing procedure of the boosting operation of the step-up / down converter according to the present embodiment will be described. FIG. 15 is a flowchart showing a first example of the processing procedure of the boosting operation of the buck-boost converter according to the present embodiment. The control unit 50 turns off the high-voltage side switching device 10 (S11), turns on the low-voltage side switching device 20 (S12), and passes a current through the second inductor 2. The control unit 50 turns off the low-voltage side switching device 20 to resonate with the second inductor 2 and the capacitor 3 (S13), turns on the high-voltage side switching device 10 (S14), and the first inductor 1 and the second inductor. 2 and the capacitor 3 are resonated (S15).

  The control unit 50 determines whether or not the voltage of the low-voltage side switching device 20 is equal to or lower than a predetermined voltage threshold (S16), and when the voltage of the low-voltage side switching device 20 is not equal to or lower than the predetermined voltage threshold (NO in S16). The process of step S16 is continued.

  When the voltage of the low-voltage side switching device 20 is equal to or lower than the predetermined voltage threshold (YES in S16), the control unit 50 turns on the low-voltage side switching device 20 (S17). When the current flowing through the first inductor 1 decreases (S18), the control unit 50 turns off the high-voltage side switching device 10 (S19), and determines whether or not to finish the boost conversion (boost operation) (S20). When the boost conversion is not finished (NO in S20), the control unit 50 continues the process after step S13, and when the boost conversion is finished (YES in S20), the process is finished.

  FIG. 16 is a flowchart showing a second example of the processing procedure of the boosting operation of the step-up / down converter of the present embodiment. The control unit 50 turns off the high-voltage side switching device 10 (S31), turns on the first low-voltage side switching device 20 (S32), and passes a current through the second inductor 2. The control unit 50 turns off the first low-voltage side switching device 20 to resonate with the second inductor 2 and the capacitor 3 (S33), turns on the high-voltage side switching device 10 (S34), the first inductor 1, (2) The inductor 2 and the capacitor 3 are resonated (S35).

  The control unit 50 turns on the second low voltage side switching device 30 (S36), and discharges the electric charge of the capacitor 3 through the second low voltage side switching device 30, thereby bringing the voltage of the capacitor 3 close to 0V.

  The control unit 50 turns on the first low-voltage side switching device 20 (S37) and turns off the second low-voltage side switching device 30 (S38). When the current flowing through the first inductor 1 decreases (S39), the control unit 50 turns off the high-voltage side switching device 10 (S40), and determines whether or not to finish the boost conversion (boost operation) (S41). When the boost conversion is not finished (NO in S41), the control unit 50 continues the process after step S33, and when the boost conversion is finished (YES in S41), the process is finished.

  In the control method of the step-up / down converter according to the present embodiment, the control unit 50 is constituted by, for example, a CPU (processor), a RAM (memory), etc., and the procedure of each process as shown in FIGS. 15 and 16 is performed. By loading a predetermined computer program into a RAM (memory) and executing the computer program by a CPU (processor), a method for controlling the step-up / down converter can be realized on the computer.

  As described above, in the step-up / step-down converter according to the present embodiment, for example, the switching loss of the switching device in the boosting operation can be reduced without adding components such as a switching device, an inductor, and a diode.

  The embodiments and examples disclosed above should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

DESCRIPTION OF SYMBOLS 1 1st inductor 2 2nd inductor 3 Capacitor 10 High voltage side switching device 20 1st low voltage side switching device 30 2nd low voltage side switching device 50 Control part

Claims (6)

A high-voltage side switching device and a first low-voltage side switching device connected in series via a first inductor, a second inductor having one end connected to a connection point of the first inductor and the first low-voltage side switching device, A step-up / down converter comprising: a capacitor connected in parallel to a first low-voltage side switching device; and a controller that turns on and off the high-voltage side switching device and the first low-voltage side switching device to operate in a predetermined operation mode. And
Outputs current through the second inductor during step-down conversion,
The control unit at the time of boost conversion,
Turning on the first low-voltage switching device and operating in a first mode in which current flows through the second inductor;
After the operation in the first mode, the first low-voltage side switching device is turned off, and the operation is performed in the second mode in which a resonance current from the first inductor, the second inductor, and the capacitor flows.
A step-up / down converter for turning on the first low-voltage side switching device and shifting to the first mode when the voltage of the first low-voltage side switching device becomes a predetermined voltage threshold value or less in the second mode. The controller is
2. The step-up / down converter according to claim 1, wherein in the second mode, a resonance current is caused to flow by the second inductor and the capacitor while the high-voltage side switching device is turned off. The controller is
In the second mode, the resonance current is allowed to flow through a diode connected in parallel to the first low-voltage switching device when the first low-voltage switching device is off. The described buck-boost converter. A voltage detection unit for detecting a voltage of the first low-voltage side switching device;
The controller is
4. The device according to claim 1, wherein when the voltage detected by the voltage detection unit is equal to or lower than the voltage threshold, the first low-voltage side switching device is turned on to shift to the first mode. 5. Buck-boost converter. A high-voltage side switching device and a first low-voltage side switching device connected in series to a computer via a first inductor, and a second inductor having one end connected to a connection point of the first inductor and the first low-voltage side switching device And a computer program for controlling a step-up / down converter comprising a capacitor connected in parallel to the first low-voltage side switching device,
On the computer,
Output current through the second inductor during step-down conversion,
Computer
Enabling the high-voltage side switching device and the first low-voltage side switching device to be turned on / off to function in a predetermined operation mode;
The control unit at the time of boost conversion,
Turning on the first low-voltage switching device and operating in a first mode in which current flows through the second inductor;
After the operation in the first mode, the first low-voltage side switching device is turned off, and the operation is performed in the second mode in which a resonance current from the first inductor, the second inductor, and the capacitor flows.
A computer program for executing processing for turning on the first low-voltage side switching device and shifting to the first mode when the voltage of the first low-voltage side switching device becomes 0 in the second mode. A high-voltage side switching device and a first low-voltage side switching device connected in series via a first inductor, a second inductor having one end connected to a connection point of the first inductor and the first low-voltage side switching device, A control method of a step-up / down converter comprising a capacitor connected in parallel to a first low-voltage side switching device,
Outputs current through the second inductor during step-down conversion,
The control unit operates in a predetermined operation mode by turning on / off the high-voltage side switching device and the first low-voltage side switching device,
The control unit at the time of boost conversion,
Turning on the first low-voltage switching device and operating in a first mode in which current flows through the second inductor;
After the operation in the first mode, the first low-voltage side switching device is turned off, and the operation is performed in the second mode in which a resonance current from the first inductor, the second inductor, and the capacitor flows.
A control method of a step-up / down converter according to which, when the voltage of the first low-voltage side switching device becomes 0 in the second mode, the first low-voltage side switching device is turned on to shift to the first mode.

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