JP2016105666A - Power conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably reduce a loss of a switching power supply device that implements soft switching by using an auxiliary inductor on the primary side.SOLUTION: A power conversion device according to an embodiment comprises: a bridge circuit including a first switching element and second switching element; a first auxiliary switch; a first auxiliary inductor; a controller; a transformer; a secondary side inductor; a switching circuit unit; a smoothing circuit; and an output detection circuit. The controller controls amplitude of at least either of output voltage and output current from the smoothing circuit, by controlling ON/OFF of a secondary side switching element of the switching circuit unit. The controller makes the first auxiliary switch perform ON/OFF operation when a detection value of the output detection circuit is equal to or lower than a setting value, and makes the first auxiliary switch be kept in an OFF state when the detection value is higher than the setting value.SELECTED DRAWING: Figure 14

Description

  The present disclosure relates to a power conversion device.

  In recent years, an insulation type DC-DC converter circuit including a soft switching circuit has been proposed. In the soft switching circuit, for example, the switching element is turned on and / or turned off so that the rate of change of the voltage applied to the switching element becomes small. Thereby, switching loss can be reduced.

  Patent Document 1 discloses a technique for supplying an auxiliary current necessary for soft switching to each switching element of an inverter. In this technique, the supply amount of the auxiliary current is controlled by the length of the ON period of the sub switch.

JP 2004-159419 A

  Provided is a power conversion device capable of stably reducing power loss.

  A first switching element; a second switching element connected in series to the first switching element; a first capacitor connected in parallel to the first switching element; and a second connected in parallel to the second switching element. A bridge circuit including a capacitor and converting an input DC voltage into a first AC voltage; a first auxiliary switch having one end connected to a first node between the first switching element and the second switching element; A first auxiliary inductor connected to the other end of the first auxiliary switch, a control device for controlling on / off of the first switching element, the second switching element, and the first auxiliary switch, and connected to the bridge circuit And a secondary winding electromagnetically coupled to the primary winding, the first AC voltage being changed to a second AC voltage. A transformer, a secondary inductor having one end connected to the secondary winding, a switching circuit unit including a secondary switching element connected to the other end of the secondary inductor, and the switching circuit unit A smoothing circuit for smoothing a voltage output from the switching circuit unit, and an output detection circuit for obtaining a detection value based on at least one of an output voltage and an output current from the smoothing circuit, and the control The apparatus controls the amplitude of at least one of the output voltage and the output current from the smoothing circuit by controlling on / off of the secondary side switching element of the switching circuit unit, and the control apparatus includes the output detection circuit When the detected value is equal to or lower than a predetermined set value, the second switching element is turned on after the first switching element is turned off. Until the first auxiliary switch is turned on, the first auxiliary switch is turned off while the first switching element or the second switching element is turned on, and the output detection is performed. The power conversion device that maintains the first auxiliary switch in an off state when the detected value of the circuit exceeds the set value.

  According to the power converter concerning one mode of this indication, power loss can be reduced stably.

FIG. 1 is a diagram schematically illustrating a configuration example of the power conversion device according to the first embodiment. FIG. 2 is a diagram schematically illustrating a configuration example of the control device in FIG. 1. FIG. 3 is a timing chart schematically showing an operation example of the switching power supply device of FIG. FIG. 4 is a diagram for explaining zero voltage switching (ZVS). FIG. 5 is a diagram schematically illustrating a configuration example of the power conversion device according to the second embodiment. FIG. 6 is a diagram schematically illustrating a configuration example of the control device in FIG. 5. FIG. 7 is a timing chart schematically showing an operation example of the switching power supply device of FIG. FIG. 8 is a diagram schematically illustrating a configuration example of the power conversion device according to the third embodiment. FIG. 9 is a diagram schematically illustrating a configuration example of the power storage system according to the fifth embodiment. FIG. 10 is a diagram schematically illustrating a configuration example of a vehicle according to the fifth embodiment. FIG. 11 is a diagram schematically illustrating a configuration example of a charger according to the fifth embodiment. FIG. 12 is a diagram schematically illustrating a modification of the auxiliary switch according to the first to fifth embodiments. FIG. 13 is a diagram schematically illustrating a waveform of a resonance current in the power conversion device of the study example. FIG. 14 is a circuit diagram illustrating a configuration example of the power conversion device 100z according to the fourth embodiment. FIG. 15 is a waveform diagram showing waveforms of output voltage and output current. FIG. 16 is a time chart of the power supply mode in the period T10 shown in FIG. FIG. 17 is a time chart of the power regeneration mode in the period T12 shown in FIG. FIG. 18 is a timing chart schematically showing an operation example of the switching power supply device according to the fourth embodiment. FIG. 19 is a diagram illustrating three operation modes that occur according to the current phase of the secondary circuit. FIG. 20 is a flowchart illustrating a method for generating a control signal for the auxiliary switch. FIG. 21 is a diagram schematically illustrating a configuration example of the control device 20z in FIG.

(Knowledge that became the basis of this disclosure)
The knowledge on which the present disclosure was based will be described. The following description is intended to help understand the present disclosure, and does not limit the present disclosure.

  The present inventors have studied a power conversion device that can reduce power loss by changing a period during which an auxiliary resonance current is supplied. The power converter of the study example includes a full bridge circuit, an auxiliary switch, an auxiliary inductor, and a control device. The auxiliary switch switches conduction between the full bridge circuit and the auxiliary inductor in response to an input from the control device. For example, the control device turns on the auxiliary switch at a timing when both of the two switches constituting the arm of the full bridge circuit are turned off. As a result, the auxiliary inductor generates a resonance current and supplies the resonance current to the full bridge circuit. The full bridge circuit realizes soft switching control using a resonance current. The control device optimizes the amount of resonance current by controlling the period Δt during which the auxiliary switch is in the ON state. Thereby, the loss due to the resonance current flowing through the auxiliary inductor is reduced.

  The power conversion device of the study example has the following problems.

  FIG. 13A illustrates a waveform when the ON period Δt of the auxiliary switch is set short in a resonance circuit designed with a long resonance period Tr, and FIG. 13B illustrates the waveform in the resonance circuit. The waveform when the ON period Δt is set long is illustrated. FIG. 13C illustrates a waveform when the auxiliary switch ON period Δt is set short in a resonance circuit designed with a short resonance period Tr, and FIG. 13D illustrates the waveform in the resonance circuit. The waveform when the ON period Δt is set long is illustrated. In FIG. 13, the broken line indicates the waveform of the resonance current that can flow through the resonance circuit, and the solid line indicates the waveform of the resonance current that actually flows through the resonance circuit during the ON period Δt of the auxiliary switch.

  The peak value of the resonance current may vary due to variations in characteristics of elements such as the auxiliary inductor. When the auxiliary switch is turned off in the middle of the rise of the resonance current (see FIG. 13A), the supply amount of the resonance current is greatly affected by variations in element characteristics. As a result, soft switching is not performed due to a shortage of resonance current, and a large loss may occur.

  On the other hand, in a resonance circuit designed with a short resonance period Tr, the resonance current rises in a short time, so that the influence due to variations in element characteristics can be reduced (see FIG. 13C). However, in a resonance circuit designed with a short resonance period Tr, the resonance current falls quickly. Therefore, even if the auxiliary switch ON period Δt is lengthened, the resonance current cannot be increased (see FIG. 13D). As a result, soft switching is not performed due to a shortage of resonance current, and a large loss may occur.

  In short, even if the resonance period of the resonance circuit is designed to be long or short, the loss reduction effect may not be obtained.

  On the other hand, it can be considered that the resonance period Tr is also changed according to the ON period Δt of the auxiliary switch. For example, a circuit in which the characteristics of the auxiliary inductor and the capacitor are variable can be considered. Alternatively, a circuit that makes the voltage supplied to the resonance circuit variable is conceivable. However, these methods cause a complicated circuit configuration and an increase in cost.

  Based on the above knowledge, the present inventors have studied a power conversion device capable of stably reducing power loss with a simple circuit configuration, and have reached the present disclosure.

(Outline of the embodiment)
A power conversion device according to an aspect of the present disclosure includes, for example, a first switching element, a second switching element connected in series to the first switching element, a first capacitor connected in parallel to the first switching element, And a second capacitor connected in parallel to the second switching element, and a bridge circuit for converting an input DC voltage into a first AC voltage, and a first circuit between the first switching element and the second switching element. A first auxiliary switch having one end connected to one node, a first auxiliary inductor connected to the other end of the first auxiliary switch, the first switching element, the second switching element, and the first auxiliary switch A control device for controlling on / off of the power source, a primary winding connected to the bridge circuit, and a secondary winding electromagnetically coupled to the primary winding A transformer for converting the first AC voltage into a second AC voltage, a secondary inductor having one end connected to the secondary winding, and a secondary connected to the other end of the secondary inductor A switching circuit unit including a side switching element, a smoothing circuit connected to the switching circuit unit for smoothing a voltage output from the switching circuit unit, and at least one of an output voltage and an output current from the smoothing circuit An output detection circuit for acquiring a detection value. The control device controls the amplitude of at least one of the output voltage and the output current from the smoothing circuit by controlling on / off of the secondary side switching element of the switching circuit unit. For example, when the detected value of the output detection circuit is equal to or less than a predetermined set value, the control device may perform the first auxiliary operation from when the first switching element is turned off to when the second switching element is turned on. While the switch is turned on and the first switching element or the second switching element is turned on, the first auxiliary switch is turned off. For example, when the detection value of the output detection circuit exceeds the set value, the control device maintains the first auxiliary switch in an off state.

  According to this configuration, the resonance current from the first auxiliary inductor is stably supplied to each capacitor according to the detected value. Thereby, switching loss can be reduced and loss due to excessive resonance current can be reduced.

  The first switching element may be any one of a plurality of switching elements constituting the bridge circuit, and is not limited to a specific switching element described in detail below. The first switching element may be any switching element indicated by S1 to S4 below, for example. The same applies to the second switching element.

  In the power conversion device according to an aspect of the present disclosure, for example, the bridge circuit includes a first arm including the first switching element, the second switching element, the first capacitor, and the second capacitor; A switching element; a fourth switching element connected in series to the third switching element; a third capacitor connected in parallel to the third switching element; and a fourth capacitor connected in parallel to the fourth switching element. A second arm that includes the second arm. The power converter includes, for example, a second auxiliary switch having one end connected to a second node between the third switching element and the fourth switching element, and a second auxiliary switch connected to the other end of the second auxiliary switch. And two auxiliary inductors. For example, the control device may further control ON / OFF of the third switching element, the fourth switching element, and the second auxiliary switch. For example, when the detected value of the output detection circuit is equal to or less than the set value, the control device may switch the second auxiliary switch between turning off the third switching element and turning on the fourth switching element. While the third switching element or the fourth switching element is turned on, the second auxiliary switch may be turned off. For example, when the detection value of the output detection circuit exceeds the set value, the control device may maintain the second auxiliary switch in an off state.

  According to this configuration, the resonance current from the first auxiliary inductor and the second auxiliary inductor is stably supplied to each capacitor according to the detected value. Thereby, switching loss can be reduced and loss due to excessive resonance current can be reduced.

  The power conversion device according to an aspect of the present disclosure includes, for example, a voltage source that supplies the DC voltage to the bridge circuit, a third auxiliary switch connected between the voltage source and the first auxiliary inductor, A fourth auxiliary switch connected between the voltage source and the second auxiliary inductor may be further included. For example, the control device may further control ON / OFF of the third auxiliary switch and the fourth auxiliary switch. For example, when the detection value of the output detection circuit is equal to or less than the set value, the control device may include the third auxiliary switch between the time when the second switching element is turned off and the time when the first switching element is turned on. The third auxiliary switch is turned off and the fourth switching element is turned off while the first switching element or the second switching element is turned on, and then the fourth switching element is turned off. The fourth auxiliary switch may be turned on while the fourth auxiliary switch is turned on, and the fourth auxiliary switch may be turned off while the third switching element or the fourth switching element is turned on. For example, when the detection value of the output detection circuit exceeds the set value, the control device may maintain the third auxiliary switch and the fourth auxiliary switch in an off state.

  According to this configuration, the resonance current from the first auxiliary inductor and the second auxiliary inductor is stably supplied to each capacitor according to the detected value. Thereby, switching loss can be reduced and loss due to excessive resonance current can be reduced.

  The voltage source may individually include a first voltage source that supplies a DC voltage to the first auxiliary inductor and a second voltage source that supplies a DC voltage to the second auxiliary inductor.

  A power conversion device according to an aspect of the present disclosure includes, for example, a voltage source that supplies the DC voltage to the bridge circuit, and a third auxiliary switch that is connected between the voltage source and the first auxiliary inductor. Further, it may be provided. For example, the second auxiliary inductor may be connected between the second auxiliary switch and the third auxiliary switch. For example, the control device may further control on / off of the third auxiliary switch. For example, when the detection value of the output detection circuit is equal to or less than the set value, the control device may turn on the first switching element after turning off the second switching element, and the fourth The third auxiliary switch is turned on until the third switching element is turned on after the switching element is turned off, the first switching element or the second switching element is turned on, and While the third switching element or the fourth switching element is turned on, the third auxiliary switch may be turned off. For example, when the detected value of the output detection circuit exceeds the set value, the control device may maintain the third auxiliary switch in an off state.

  According to this configuration, the resonance current from the first auxiliary inductor and the second auxiliary inductor is stably supplied to each capacitor according to the detected value. Thereby, switching loss can be reduced and loss due to excessive resonance current can be reduced. Further, a switch for supplying a DC voltage to the first auxiliary inductor and a switch for supplying a DC voltage to the second auxiliary inductor are shared by the third auxiliary switch. Thereby, the number of switches can be reduced and the circuit scale can be reduced. Furthermore, for example, the circuit scale of the control device can be reduced with the reduction of switches.

  In the power conversion device according to an aspect of the present disclosure, for example, the voltage source may include a first voltage source capacitor and a second voltage source capacitor connected in series to the first voltage source capacitor. For example, the third auxiliary switch may be connected to an intermediate node between the first voltage source capacitor and the second voltage source capacitor. Alternatively, the third auxiliary switch and the fourth auxiliary switch may be connected to an intermediate node between the first voltage source capacitor and the second voltage source capacitor, for example.

  Thereby, a DC voltage is supplied from the intermediate node via the third auxiliary switch and / or the fourth auxiliary switch. Due to this DC voltage, a resonance current can be generated in the first auxiliary inductor and the second auxiliary inductor. As a result, the loss of the power conversion device can be stably reduced.

  In the power conversion device according to an aspect of the present disclosure, for example, the first auxiliary switch is a first bidirectional switching element. For example, when the detection value of the output detection circuit is equal to or lower than a predetermined set value, the control device may perform the first both steps from turning off the first switching element to turning on the second switching element. One of the two gates of the directional switching element is turned on, and the other of the two gates of the first bidirectional switching element between the time when the second switching element is turned off and the time when the first switching element is turned on. May be turned on, and the two gates of the first bidirectional switching element may be turned off while the first switching element or the second switching element is turned on.

  In the power conversion device according to an aspect of the present disclosure, for example, the bridge circuit includes a first arm including the first switching element, the second switching element, the first capacitor, and the second capacitor; A switching element; a fourth switching element connected in series to the third switching element; a third capacitor connected in parallel to the third switching element; and a fourth capacitor connected in parallel to the fourth switching element. Including a second arm. The power converter is connected to, for example, a second bidirectional switching element having one end connected to a second node between the third switching element and the fourth switching element, and the other end of the second auxiliary switch. A second auxiliary inductor, and the control device further controls on / off of the third switching element, the fourth switching element, and the second bidirectional switching element, for example. For example, when the detection value of the output detection circuit is equal to or less than the set value, the control device may perform the second bidirectional switching from when the third switching element is turned off to when the fourth switching element is turned on. One of the two gates of the device is turned on, and the other of the two gates of the second bidirectional switching device is turned on after the fourth switching device is turned off until the third switching device is turned on. You may make it a state.

  In the power conversion device according to an aspect of the present disclosure, for example, the control device causes the first auxiliary switch, the resonance to flow through the first capacitor, and the second capacitor by turning on the first auxiliary switch. The resonance current may not be generated by generating a current and turning off the auxiliary switch. For example, during a period in which the first switching element and the second switching element are in an OFF state, a current flowing through the secondary inductor causes energy to be accumulated in the secondary inductor, and another resonance current generated by the energy is generated. The first capacitor and the second capacitor may be charged and discharged.

  Thereby, a resonance current is supplied from the secondary inductor during a period in which the first switching element and the second switching element are in the OFF state. In addition, the resonance current can be selectively supplied also from the first auxiliary inductor according to the magnitude of the detected value. As a result, switching loss can be stably reduced, and loss due to excessive resonance current can be reduced.

  In the power conversion device according to an aspect of the present disclosure, for example, the reference terminal of the first switching element and the reference terminal of the first auxiliary switch may be equipotential. For example, the reference terminal of the third switching element and the reference terminal of the second auxiliary switch may be equipotential. For example, the reference terminal of the second switching element and the reference terminal of the fourth switching element may be equipotential. For example, the reference terminal of the third auxiliary switch and the reference terminal of the fourth auxiliary switch may be equipotential.

  Since the reference terminals of the plurality of switches are equipotential, the DC voltage in the control device can be shared, and the circuit scale of the control device can be reduced.

  In the power conversion device according to an aspect of the present disclosure, for example, the first switching element, the second switching element, the third switching element, the fourth switching element, the first auxiliary switch, the second auxiliary switch, The third auxiliary switch and the fourth auxiliary switch may be IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

  When each switch is an IGBT, the reference terminal is an emitter terminal. Alternatively, when each switch is a MOSFET, the reference terminal is a source terminal.

  In the power conversion device according to an aspect of the present disclosure, for example, the first switching element, the second switching element, the third switching element, and the fourth switching element may be phase-shift controlled.

  In the present disclosure, “the control device makes the state B during the period A” means that the control device makes the state B in at least part of the period A, and the control device makes the period A Also included are those to be in state B during the included period.

  Hereinafter, embodiments will be specifically described with reference to the drawings.

  It should be noted that each of the embodiments described below shows a comprehensive or specific example. Numerical values, shapes, waveforms, materials, components, component arrangement positions and connection forms, steps, order of steps, and the like shown in the following embodiments are merely examples, and are not intended to limit the present disclosure. In addition, among the constituent elements in the following embodiments, constituent elements that are not described in the independent claims indicating the highest concept are described as optional constituent elements.

  The terms representing directions such as “up”, “down”, “left” and “right” are merely for the purpose of clarifying the explanation. Accordingly, these terms should not be construed as limiting. Note that, in all the following drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description may be omitted.

(Embodiment 1)
[Configuration of Power Conversion Device 100]
FIG. 1 is a diagram illustrating an example of a configuration of the power conversion device 100 according to the first embodiment. The power conversion device 100 includes a switching power supply device 10, an output voltage detection circuit 11, an output current detection circuit 12, and a control device 20. The switching power supply device 10 is a phase shift type isolated DC-DC converter. The switching power supply 10 includes a full bridge circuit, a first auxiliary inductor L1, a second auxiliary inductor L2, a third inductor L3, a fourth inductor L4, a sixth capacitor C6, a seventh capacitor C7, a fifth auxiliary switch S5, a sixth It includes an auxiliary switch S6, a seventh auxiliary switch S7, an eighth auxiliary switch S8, a transformer T, a rectifier circuit, a smoothing circuit, and an output resistor R1.

  The full bridge circuit is an inverter that converts a DC voltage supplied from the DC power source E into an AC voltage. The full bridge circuit includes a first switching element S1, a second switching element S2, a third switching element S3, and a fourth switching element S4, which are full bridge connected. Specifically, the full bridge circuit includes a first arm including a first switching element S1 on the upper side and a second switching element S2 on the lower side, a third switching element S3 on the upper side, and a fourth switching element S4 on the lower side. It is comprised with the 2nd arm containing. The first arm and the second arm are connected in parallel.

  In the example shown in FIG. 1, the full bridge circuit includes a first capacitor C1 connected in parallel to the first switching element S1, a second capacitor C2 connected in parallel to the second switching element S2, and a third switching circuit. A third capacitor C3 connected in parallel to the element S3 and a fourth capacitor C4 connected in parallel to the fourth switching element S4 are included. In the example shown in FIG. 1, the full bridge circuit includes a first diode D1 connected in parallel to the first switching element S1, a second diode D2 connected in parallel to the second switching element S2, and a third switching circuit. A third diode D3 connected in parallel to the element S3 and a fourth diode D4 connected in parallel to the fourth switching element S4 are included.

  The first diode D1 to the fourth diode D4 are connected in reverse bias to the first switching element S1 to the fourth switching element S4, respectively. The first capacitor C1 to the fourth capacitor C4 are, for example, lossless snubber capacitors. The first switching element S1 to the fourth switching element S4 are semiconductor switching elements such as MOSFETs and IGBTs, for example.

  In the example shown in FIG. 1, the first switching element S1 to the fourth switching element S4 are n-channel IGBTs. In this case, the collector terminal of the first switching element S1 is connected to the high potential side reference line of the DC power supply E. The emitter terminal of the first switching element S1 is connected to the collector terminal of the second switching element S2. The emitter terminal of the second switching element S2 is connected to the low potential side reference line of the DC power supply E. The collector terminal of the third switching element S3 is connected to the high potential side reference line of the DC power supply E. The emitter terminal of the third switching element S3 is connected to the collector terminal of the fourth switching element S4. The emitter terminal of the fourth switching element S4 is connected to the low potential side reference line of the DC power supply E. When the first switching element S1 to the fourth switching element S4 are MOSFETs, the emitter may be read as the source, and the collector may be read as the drain.

  The primary circuit shown in FIG. 1 is a partial resonance type full bridge circuit. The partial resonance type full bridge circuit performs commutation using the resonance operation only during the dead time of the first arm and the dead time of the second arm, and operates in a non-resonance manner during other periods. The “dead time of the first arm” means a period in which both the first switching element S1 and the second switching element S2 are in the off state. The “dead time of the first arm” means a period in which both the third switching element S3 and the fourth switching element S4 are in the off state. The primary circuit shown in FIG. 1 has a resonant pole type configuration. The sixth capacitor C6 and the seventh capacitor C7 connected in series are connected in parallel to the DC power source E and divide the DC power source E. In the example of FIG. 1, the voltage divided by the sixth capacitor C <b> 6 and the voltage divided by the seventh capacitor C <b> 7 correspond to the intermediate voltage of the DC power supply E, respectively. The sixth capacitor C6 and the seventh capacitor C7 smooth the potentials of the high potential side reference line of the DC power source E, the low potential side reference line of the DC power source E, and the intermediate potential line of the DC power source E.

  The sixth capacitor C6 is an example of the “first voltage source capacitor” in the present disclosure. The seventh capacitor C7 is an example of the “second voltage source capacitor” in the present disclosure. The characteristics of the sixth capacitor C6 and the seventh capacitor C7 may be the same or different. That is, the voltage supplied by the intermediate node may be half that of the DC power supply E or may be other than that.

  A node between the first switching element S1 and the second switching element S2 is called a first node Na. A node between the third switching element S3 and the fourth switching element S4 is referred to as a second node Nb. A node between the sixth capacitor C6 and the seventh capacitor C7 is called an intermediate node Nc.

  A first auxiliary inductor L1 is connected between the intermediate node Nc and the first node Na. The first auxiliary inductor L1 is connected between the intermediate node Nc and the second node Nb.

  A fifth auxiliary switch S5 is connected between the intermediate node Nc and one end of the first auxiliary inductor L1. Specifically, the emitter terminal of the fifth auxiliary switch S5 is connected to the intermediate node Nc, and the collector terminal of the fifth auxiliary switch S5 is connected to one end of the first auxiliary inductor L1. A sixth auxiliary switch S6 is connected between the other end of the first auxiliary inductor L1 and the first node Na. Specifically, the emitter terminal of the sixth auxiliary switch S6 is connected to the first node Na, and the collector terminal of the sixth auxiliary switch S6 is connected to the other end of the first auxiliary inductor L1. The fifth auxiliary switch S5 and the sixth auxiliary switch S6 connected in series via the first auxiliary inductor L1 function as a bidirectional switch.

  A seventh auxiliary switch S7 is connected between the intermediate node Nc and one end of the second auxiliary inductor L2. Specifically, the emitter terminal of the seventh auxiliary switch S7 is connected to the intermediate node Nc, and the collector terminal of the seventh auxiliary switch S7 is connected to one end of the second auxiliary inductor L2. A seventh auxiliary switch S7 is connected between the other end of the second auxiliary inductor L2 and the second node Nb. Specifically, the emitter terminal of the seventh auxiliary switch S7 is connected to the second node Nb, and the collector terminal of the seventh auxiliary switch S7 is connected to the other end of the second auxiliary inductor L2. The seventh auxiliary switch S7 and the eighth auxiliary switch S8 connected in series via the second auxiliary inductor L2 function as a bidirectional switch.

  The fifth diode D5 is connected to the fifth auxiliary switch S5 with a reverse bias. The sixth diode D6 is connected to the sixth auxiliary switch S6 with a reverse bias. The seventh diode D7 is connected to the seventh auxiliary switch S7 with a reverse bias. The eighth diode D8 is connected to the eighth auxiliary switch S8 with a reverse bias.

  Each of the auxiliary switches S5 to S8 may be a semiconductor switching element such as a MOSFET or an IGBT. In the example shown in FIG. 1, each of the auxiliary switches S5 to S8 is an n-channel type IGBT.

  The sixth auxiliary switch S6 is an example of the “first auxiliary switch” in the present disclosure. The eighth auxiliary switch S8 is an example of the “second auxiliary switch” in the present disclosure. The fifth auxiliary switch S5 is an example of a “third auxiliary switch” in the present disclosure. The seventh auxiliary switch S7 is an example of the “fourth auxiliary switch” in the present disclosure.

  The transformer T is a high-frequency transformer including a primary winding N1 and a secondary winding N2. The primary winding N1 and the secondary winding N2 are coupled by electromagnetic induction. The transformer T insulates the primary side from the secondary side. The transformer T converts the first AC voltage input from the primary winding N1 into the second AC voltage output to the secondary winding N2 according to the turns ratio of the primary winding N1 and the secondary winding N2. Transform. Both ends of the primary winding N1 are connected to both output ends of the full bridge circuit. Specifically, both ends of the primary winding N1 are connected between the first node Na and the second node Nb.

  The third inductor L3 and the fourth inductor L4 are connected to a current path between the secondary winding N2 of the transformer T and the rectifier circuit. The third inductor L3 and the fourth inductor L4 may be the third coil L3 and the fourth coil L4. The third inductor L3 and the fourth inductor L4 may be a leakage inductance of the secondary winding N2.

  The rectifier circuit rectifies the second AC voltage input from the secondary winding N2, and generates a rectified voltage. The rectifier circuit includes a ninth diode D9, a tenth diode D10, an eleventh diode D11, and a twelfth diode D12, which are connected in a full bridge.

  The smoothing circuit smoothes the rectified voltage and generates an output voltage. The smoothing circuit in FIG. 1 includes an LC filter including a fifth inductor L5 and a fifth capacitor C5. The fifth inductor L5 is, for example, a fifth coil L5. The smoothing circuit shown in FIG. 1 is an example, and the present invention is not limited to this. For example, the smoothing circuit may not have the fifth inductor L5.

  The output resistor R1 is a current detection element for detecting the value of the current supplied from the smoothing circuit to the load 30. A Hall element may be used instead of the output resistor R1.

  The output voltage detection circuit 11 detects the output voltage output from the switching power supply device 10 to the load 30. The output voltage detection circuit 11 may be an error amplification circuit, for example. The error amplifier circuit may include an operational amplifier and a passive element. The output voltage detection circuit 11 outputs the detection result to the control device 20.

  The output voltage detection circuit 11 is an example of the “output detection circuit” in the present disclosure.

  The output current detection circuit 12 detects the output current output from the switching power supply device 10 to the load 30. The output current detection circuit 12 may be, for example, an error amplification circuit that receives the voltage across the output resistor R1. The output current detection circuit 12 outputs the detection result to the control device 20.

  The output current detection circuit 12 is an example of the “output detection circuit” in the present disclosure.

  The control device 20 controls on / off of the first switching element S1 to the fourth switching element S4 and the fifth auxiliary switch S5 to the eighth auxiliary switch S8. In other words, the switching power supply device 10 is driven by the control device 20. For example, the control device 20 switches the phase of the switching operation of the first arm and the switching of the second arm according to the output voltage supplied from the output voltage detection circuit 11 and / or the output current supplied from the output current detection circuit 12. Controls the phase difference from the phase of operation. The control device 20 executes this control by a phase shift PWM (Pulse Width Modulation) method. For example, the control device 20 compares the output voltage fed back from the output voltage detection circuit 11 with a preset target voltage. The control device 20 reduces the phase difference when the output voltage is smaller than the target voltage, and increases the phase difference when the output voltage is larger than the target voltage. According to this control, the power supplied from the primary side to the secondary side decreases as the phase difference increases. The control device may drive the switching power supply device 10 with constant current drive or constant power drive.

  FIG. 2 shows a configuration example of the control device 20. The control device 20 includes a CPU 21 and a drive circuit 22. In the switching power supply device 10 of FIG. 1, the emitter terminal of the first switching element S1 and the emitter terminal of the sixth auxiliary switch S6 are equipotential. The emitter terminal of the third switching element S3 and the emitter terminal of the eighth auxiliary switch S8 are equipotential. The emitter terminal of the fifth auxiliary switch S5 and the emitter terminal of the seventh auxiliary switch S7 are equipotential. The emitter terminals of the second switching element S2 and the fourth switching element S4 are equipotential. At this time, it is sufficient for the drive circuit to generate, for example, four pairs of drive voltages composed of a high level voltage and a low level voltage. In other words, a circuit for generating a power supply voltage can be shared by sharing the emitter potential between a plurality of switches. Thereby, reduction in circuit scale and cost reduction can be realized.

  Power from an external power source is supplied to the CPU 21 and the drive circuit 22. The external power source may be, for example, a commercial power source or a storage battery. In accordance with the output voltage supplied from the output voltage detection circuit 11 and / or the output current supplied from the output current detection circuit 12, the CPU 21 performs the first switching element S1 to the fourth switching element S4 and the fifth auxiliary switch S5. The control signals for the eighth auxiliary switch S8 are generated and output to the drive circuit 22. Each control signal is, for example, a digital signal.

  Hereinafter, a specific example of the drive circuit will be described. The drive circuit 22 includes a first drive unit, a second drive unit, a third drive unit, and a fourth drive unit. However, each drive part does not need to be formed collectively on the circuit.

  The first driver includes a first high-side DC-DC converter 241, a first low-side DC-DC converter 251, a first gate buffer 231, a second gate buffer 236, a first control logic circuit 261, and a second control logic circuit 266. , A first photocoupler 271 and a second photocoupler 276 are provided. The first drive unit drives the first switching element S1 and the sixth auxiliary switch S6.

  The first control logic circuit 261 generates a drive signal in accordance with the input control signal. The first photocoupler 271 transmits a drive signal from the first control logic circuit 261 to the first gate buffer 231 in a state where the first control logic circuit 261 and the first gate buffer 231 are insulated. The first gate buffer 231 drives the first switching element S1 according to the input drive signal. The output terminal of the first gate buffer 231 is connected to the gate terminal of the first switching element S1 via a current limiting element (not shown). The current control element is, for example, a gate resistance. For example, the first gate buffer 231 is an inverter in which a p-channel MOSFET and an n-channel MOSFET are connected in series.

  The second control logic circuit 266 generates a drive signal in accordance with the input control signal. The second photocoupler 276 transmits a drive signal from the second control logic circuit 266 to the second gate buffer 236 in a state where the second control logic circuit 266 and the second gate buffer 236 are insulated. The second gate buffer 236 drives the sixth auxiliary switch S6 according to the input drive signal. The output terminal of the second gate buffer 236 is connected to the gate terminal of the sixth auxiliary switch S6 via a current limiting element (not shown). The current control element is, for example, a gate resistance. The second gate buffer 236 is, for example, an inverter in which a p-channel MOSFET and an n-channel MOSFET are connected in series.

  The first high side DC-DC converter 241 generates a high side power supply potential from an external power supply. The first low side DC-DC converter 251 generates a low side power supply potential from an external power supply. The first high-side DC-DC converter 241 and the first low-side DC-DC converter 251 may be a step-down chopper, for example. For example, when the first gate buffer 231 is an inverter, the high-side power supply potential is applied to the source terminal of the p-channel MOSFET, and the low-side power supply potential is applied to the source terminal of the n-channel MOSFET.

  The first high side DC-DC converter 241 generates a potential of +15 V with respect to the reference potential, and supplies this to the first gate buffer 231 and the second gate buffer 236. The first low-side DC-DC converter 251 generates a potential of −5 V with respect to the reference potential, and supplies this to the first gate buffer 231 and the second gate buffer 236. That is, the first gate buffer 231 and the second gate buffer 236 are controlled by a power supply voltage of 20V. The first gate buffer 231 applies a gate potential of + 15V with respect to the emitter potential to the first switching element S1. The second gate buffer 236 applies a gate potential of −5 V with respect to the emitter potential to the sixth auxiliary switch S6. However, the values of the power supply voltage and the gate potential are not limited to this.

  The second driving unit includes a second high-side DC-DC converter 242, a second low-side DC-DC converter 252, a third gate buffer 233, a fourth gate buffer 238, a third control logic circuit 263, and a fourth control logic circuit 268. , A third photocoupler 273 and a fourth photocoupler 278 are provided. The second drive unit drives the third switching element S3 and the eighth auxiliary switch S8. Each configuration of the second drive unit can be described in the same manner as the first drive unit, for example.

  The third driving unit includes a third high-side DC-DC converter 243, a third low-side DC-DC converter 253, a fifth gate buffer 235, a sixth gate buffer 237, a fifth control logic circuit 265, and a sixth control logic circuit 267. The fifth photocoupler 275 and the sixth photocoupler 277 are provided. The third drive unit drives the fifth auxiliary switch S5 and the seventh auxiliary switch S7. Each configuration of the third drive unit can be described, for example, similarly to the first drive unit.

  The fourth driving unit includes a fourth high-side DC-DC converter 244, a fourth low-side DC-DC converter 254, a seventh gate buffer 232, an eighth gate buffer 234, a seventh control logic circuit 262, and an eighth control logic circuit 264. The seventh photocoupler 272 and the eighth photocoupler 274 are provided. The fourth driving unit drives the second switching element S2 and the fourth switching element S4. Each configuration of the fourth drive unit can be described in the same manner as the first drive unit, for example.

  Since each switching element constituting the switching power supply device 10 has the connection relationship shown in FIG. 1, the configuration of the drive circuit 22 can be simplified. By connecting the emitter terminals of a plurality of switching elements, for example, the number of high-side DC-DC converters and low-side DC-DC converters can be reduced. In the example shown in FIG. 2, the drive circuit is composed of four high-side DC-DC converters, four low-side DC-DC converters, eight gate buffers, eight control logic circuits, and eight photocouplers. Composed.

[Driving Method of Switching Power Supply Device 10]
A driving method of the switching power supply device 10, that is, an operation method of the control device 20 will be described as an example.

  Since the switching power supply device 10 has a partial resonance type full bridge circuit, the control device 20 allows the resonance operation only during the dead time of the first arm and the second arm of the full bridge circuit.

  The control device 20 turns off both the fifth auxiliary switch S5 and the sixth auxiliary switch S6 during a period in which the first switching element S1 or the second switching element S2 is in the on state. The control device 20 turns off both the seventh auxiliary switch S7 and the eighth auxiliary switch S8 during a period in which the third switching element S3 or the fourth switching element S4 is on. Thereby, an unnecessary current does not flow through the first auxiliary inductor L1 or the second auxiliary inductor L2, and the loss can be reduced.

  For example, the control device 20 acquires a detection value based on at least one of the output voltage and the output current of the switching power supply device 10 and compares it with a set value. The control device 20 determines whether or not to turn on / off the fifth auxiliary switch S5 to the eighth auxiliary switch S8 according to the result.

  When the detected value exceeds the set value, the control device 20 maintains the fifth auxiliary switch S5 to the eighth auxiliary switch S8 in the off state. That is, the on / off operations of the fifth auxiliary switch S5 to the eighth auxiliary switch S8 are invalidated, and the generation of the resonance current by the first auxiliary inductor L1 and the second auxiliary inductor L2 is prevented.

  When the detected value is equal to or smaller than the set value, the control device 20 turns on the fifth auxiliary switch S5 or the sixth auxiliary switch S6 during the dead time of the first arm. Specifically, the control device 20 alternately turns on the fifth auxiliary switch S5 or the sixth auxiliary switch S6 every time the first arm dead time comes. When the fifth auxiliary switch S5 is on and the sixth auxiliary switch S6 is off, the second capacitor C2 is discharged and the first capacitor C1 is charged. That is, the electric charge accumulated in the second capacitor C2 is commutated to the first capacitor C1. When the sixth auxiliary switch S6 is on and the fifth auxiliary switch S5 is off, the first capacitor C1 is discharged and the second capacitor C2 is charged. That is, the electric charge accumulated in the first capacitor C1 is commutated to the second capacitor C2. By these charge / discharge operations, the switching elements connected in parallel to the discharged capacitors can be zero-voltage switched.

  When the detected value is equal to or smaller than the set value, the control device 20 turns on the seventh auxiliary switch S7 or the eighth auxiliary switch S8 during the dead time of the second arm. Specifically, the control device 20 alternately turns on the seventh auxiliary switch S7 or the eighth auxiliary switch S8 every time the second arm dead time comes. When the seventh auxiliary switch S7 is on and the eighth auxiliary switch S8 is off, the fourth capacitor C4 is discharged and the third capacitor C3 is charged. That is, the electric charge accumulated in the fourth capacitor C4 is commutated to the third capacitor C3. When the eighth auxiliary switch S8 is on and the seventh auxiliary switch S7 is off, the third capacitor C3 is discharged and the fourth capacitor C4 is charged. That is, the electric charge accumulated in the third capacitor C3 is commutated to the fourth capacitor C4. By these charge / discharge operations, the switching elements connected in parallel to the discharged capacitors can be zero-voltage switched.

  The amount of current generated by charging / discharging the first capacitor C1 to the fourth capacitor C4 includes the LC resonance frequency, the DC voltage applied to the first auxiliary inductor L1 or the second auxiliary inductor L2, and the fifth auxiliary switch S5 to eighth auxiliary. It is determined by the ON time Δt of the switch S8. In the first embodiment, the LC constant, the DC voltage, and the on-time Δ are all fixed values. Therefore, the amount of current that can be supplied from the first auxiliary inductor L1 or the second auxiliary inductor L2 to the first capacitor C1 to the fourth capacitor C4 is constant regardless of the state of the output voltage and output current of the switching power supply device 10. In addition, since the LC constant, the DC voltage, and the on-time Δt are fixed, the waveform of the resonance current is stabilized, and the influence of component variations can be reduced.

  In the example shown in FIG. 1, the third inductor L3 and the fourth inductor L4 also generate a resonance current during the dead time of the first arm or the second arm. The charging / discharging operation of the first capacitor C1 to the fourth capacitor C4 is also performed by this resonance current. The amount of current supplied from the third inductor L3 or the fourth inductor L4 to the first capacitor C1 to the fourth capacitor C4 varies depending on the output current (that is, the load state) of the switching power supply device 10.

  The control device 20 selects whether to generate a resonance current using the first auxiliary inductor L1 and the second auxiliary inductor L2 according to at least one of the output voltage and the output current from the switching power supply device 10. . For example, when the output current is larger than the set value, the control device 20 maintains the fifth auxiliary switch S5 to the eighth auxiliary switch S8 in the off state, and when the output current of the switching power supply device 10 is less than the set value, The on / off operation of the fifth auxiliary switch S5 to the eighth auxiliary switch S8 is validated. The former corresponds to a heavy load, and the latter corresponds to a light load.

  When the fifth auxiliary switch S5 to the eighth auxiliary switch S8 are maintained in the OFF state, the resonance current is supplied to the first capacitor C1 to the fourth capacitor C4 only from the third inductor L3 and the fourth inductor L4. At this time, the switching power supply device 10 can realize soft switching using the current generated by the third inductor L3 and the fourth inductor L4. Alternatively, even if soft switching is not completely realized, switching loss can be effectively reduced.

  For example, when the output current of the switching power supply device 10 is small, soft switching may not be realized only by supplying current from the third inductor L3 and the fourth inductor L4. In such a case, the control device 20 enables the on / off operation of the fifth auxiliary switch S5 to the eighth auxiliary switch S8. Thereby, the resonance current is supplied to the first capacitor C1 to the fourth capacitor C4 not only from the third inductor L3 and the fourth inductor L4 but also from the first auxiliary inductor L1 or the second auxiliary inductor L2. That is, the amount of current supplied to the first capacitor C1 to the fourth capacitor C4 increases due to the resonance current from the first auxiliary inductor L1 or the second auxiliary inductor L2. Thereby, for example, even when the output current of the switching power supply device 10 is large, soft switching can be realized. Alternatively, even if soft switching is not completely realized, switching loss can be effectively reduced.

  The set value for determining the magnitude relationship between the output voltage, output current, or output power of the switching power supply device 10 may be a value derived in advance based on an experiment or simulation by a designer.

  FIG. 3 is a timing chart showing an operation example of the switching power supply device 10 of FIG. FIG. 3A shows a timing chart at a light load, and FIG. 3B shows a timing chart at a heavy load. The weight of the load 30 can be determined by at least one of the output voltage and the output current. For example, a state where the detected value based on at least one of the output voltage and output current of the switching power supply device 10 is equal to or lower than a predetermined set value is classified as a light load, and a state where the detected value exceeds the set value is classified as a heavy load. The

  In the example shown in FIG. 3A, the on / off operation of the fifth auxiliary switch S5 to the eighth auxiliary switch S8 is effective at light load. Specifically, the sixth auxiliary switch S6 is turned on after the first switching element S1 is turned off until the second switching element S2 is turned on. The fifth auxiliary switch S5 is turned on after the second switching element S2 is turned off until the first switching element S1 is turned on. The seventh auxiliary switch S7 is turned on after the fourth switching element S4 is turned off until the third switching element S3 is turned on. The eighth auxiliary switch S8 is turned on after the third switching element S3 is turned off until the fourth switching element S4 is turned on. In this operation example, the ON periods Δt of the fifth auxiliary switch S5 to the eighth auxiliary switch S8 are fixed.

  In the example shown in FIG. 3B, the ON / OFF operation of the fifth auxiliary switch S5 and the sixth auxiliary switch S6 during the first arm dead time is invalid during heavy load, and the second arm dead time during the second arm dead time is invalid. The on / off operation of the seventh auxiliary switch S7 and the eighth auxiliary switch S8 is effective. Alternatively, the on / off operation of the seventh auxiliary switch S7 and the eighth auxiliary switch S8 may be invalid even in the dead time of the second arm. Alternatively, the on / off operation of the fifth auxiliary switch S5 and the sixth auxiliary switch S6 in the dead time of the first arm is effective, and the on / off operation of the seventh auxiliary switch S7 and the eighth auxiliary switch S8 in the dead time of the second arm is effective. It may be invalid. Which of these is selected may be determined based on at least one of the output voltage and the output current.

  FIG. 4 is a diagram for explaining zero voltage switching (ZVS). FIG. 4A shows an example of a timing chart when ZVS is established. 4B and 4C show an example of a timing chart when ZVS is not established.

  A case where ZVS is established in the first switching element S1 will be described. Before the ON signal is applied to the gate terminal of the first switching element S1, all charges of the first capacitor C1 are discharged by the resonance current flowing through the auxiliary inductor and the first capacitor C1. As a result, the voltage between the collector and the emitter of the first switching element S1 becomes zero. In this state, when the first switching element S1 is turned on, ZVS is realized. In this case, as shown in FIG. 4A, neither switching loss nor surge voltage is generated.

  A case where ZVS is not established in the third switching element S3 will be described. Before the ON signal is applied to the gate terminal of the third switching element S3, a part of the charge of the third capacitor C3 may not be discharged. When the third switching element S3 is turned on in this state, ZVS is not realized, and switching loss and surge voltage are generated. As the voltage between the collector and the emitter of the third switching element S3 immediately before the third switching element S3 is turned on is closer to 0, the switching loss and the surge voltage are reduced. FIG. 4B shows an example in which the switching loss and the surge voltage are effectively reduced by using the auxiliary inductor.

  According to the power conversion device of the first embodiment, when the resonance current is insufficient, the resonance current by the auxiliary inductor is stably supplied to each capacitor. Thereby, the switching loss and the surge voltage can be reduced to zero or can be effectively reduced. On the other hand, when the resonance current is excessive, the supply of unnecessary resonance current is stopped by turning off the auxiliary switch between the auxiliary inductor and each capacitor. Thereby, the loss generated by the resonance current flowing through the auxiliary inductor can be stably reduced.

(Embodiment 2)
[Configuration of Power Conversion Device 100x]
FIG. 5 shows an example of the configuration of the power conversion device 100x according to the second embodiment. Hereinafter, differences between the power conversion device 100x according to the second embodiment and the power conversion device 100 according to the first embodiment will be described. A duplicate description between the two is omitted as appropriate.

  The fifth auxiliary switch S5 shown in FIG. 5 shares the functions of the fifth auxiliary switch S5 and the seventh auxiliary switch S7 shown in FIG. In the example shown in FIG. 5, the fifth auxiliary switch S5 is connected between the intermediate node Nc and a common terminal to which the first auxiliary inductor L1 and the second auxiliary inductor L2 are connected. Specifically, the emitter terminal of the fifth auxiliary switch S5 is connected to the intermediate node Nc, and the collector terminal of the fifth auxiliary switch S5 is commonly connected to one end of the first auxiliary inductor L1 and one end of the second auxiliary inductor L2.

  FIG. 6 shows a configuration example of the control device 20x. The control device 20x shown in FIG. 6 is different from the control device 20 shown in FIG. 2 in that the sixth gate buffer 237, the sixth control logic circuit 267, and the sixth photocoupler 277 are not provided. Since the auxiliary switch connected to the intermediate node Nc is shared by the fifth auxiliary switch S5, the circuit scale can be further reduced as compared with the control device 20 shown in FIG.

[Driving Method of Switching Power Supply Device 10x]
A driving method of the switching power supply device 10x, that is, an operation method of the control device 20x will be exemplarily described.

  The control device 20x turns off both the fifth auxiliary switch S5 and the sixth auxiliary switch S6 during a period in which the first switching element S1 or the second switching element S2 is in the on state. The control device 20x turns off both the fifth auxiliary switch S5 and the eighth auxiliary switch S8 during a period in which the third switching element S3 or the fourth switching element S4 is in the on state. Thereby, an unnecessary current does not flow through the first auxiliary inductor L1 or the second auxiliary inductor L2, and the loss can be reduced.

  For example, the control device 20x acquires a detection value based on at least one of the output voltage and the output current of the switching power supply device 10x, and compares this with a set value. The control device 20x determines whether to turn on / off the fifth auxiliary switch S5, the sixth auxiliary switch S6, and the eighth auxiliary switch S8 according to the result.

  When the detected value exceeds the set value, the control device 20 maintains the fifth auxiliary switch S5, the sixth auxiliary switch S6, and the eighth auxiliary switch S8 in the off state. That is, the on / off operation of the fifth auxiliary switch S5, the sixth auxiliary switch S6, and the eighth auxiliary switch S8 is invalidated, and the generation of the resonance current by the first auxiliary inductor L1 and the second auxiliary inductor L2 is prevented. .

  When the detected value is equal to or smaller than the set value, the control device 20x turns on the fifth auxiliary switch S5 or the sixth auxiliary switch S6 during the dead time of the first arm. Specifically, the control device 20x alternately turns on the fifth auxiliary switch S5 or the sixth auxiliary switch S6 every time the first arm dead time comes.

  When the detected value is equal to or smaller than the set value, the control device 20x turns on the fifth auxiliary switch S5 or the eighth auxiliary switch S8 during the dead time of the second arm. Specifically, the control device 20x alternately turns on the fifth auxiliary switch S5 or the eighth auxiliary switch S8 every time the second arm dead time comes.

  FIG. 7 is a timing chart showing an operation example of the switching power supply device 10x of FIG. FIG. 7A shows a timing chart at a light load, and FIG. 5B shows a timing chart at a heavy load.

  In the example shown in FIG. 7A, the ON / OFF operation of the fifth auxiliary switch S5, the sixth auxiliary switch S6, and the eighth auxiliary switch S8 is effective at light load. Specifically, the sixth auxiliary switch S6 is turned on after the first switching element S1 is turned off until the second switching element S2 is turned on. The fifth auxiliary switch S5 is turned on after the second switching element S2 is turned off until the first switching element S1 is turned on. The fifth auxiliary switch S5 is turned on after the fourth switching element S4 is turned off until the third switching element S3 is turned on. The eighth auxiliary switch S8 is turned on after the third switching element S3 is turned off until the fourth switching element S4 is turned on. The on periods Δt of the fifth auxiliary switch S5 to the seventh auxiliary switch S7 are fixed.

  In the example shown in FIG. 7B, the ON / OFF operation of the fifth auxiliary switch S5 and the sixth auxiliary switch S6 in the dead time of the first arm is invalid during heavy load, and the second time in the dead time of the second arm is invalid. The on / off operation of the five auxiliary switches S5 and the eighth auxiliary switch S8 is effective. Alternatively, the on / off operation of the fifth auxiliary switch S5 and the eighth auxiliary switch S8 may be invalid even in the dead time of the second arm. Alternatively, the on / off operation of the fifth auxiliary switch S5 and the sixth auxiliary switch S6 during the dead time of the first arm is effective, and the on / off operation of the fifth auxiliary switch S5 and the eighth auxiliary switch S8 during the dead time of the second arm is effective. It may be invalid. Which of these is selected may be determined based on at least one of the output voltage and the output current.

  According to the power conversion device of the second embodiment, when the resonance current is insufficient, the resonance current from the auxiliary inductor can be stably supplied to each capacitor. Thereby, the switching loss and the surge voltage can be reduced to zero or can be effectively reduced. On the other hand, when the resonance current is excessive, unnecessary resonance current can be stopped by turning off the auxiliary switch between the auxiliary inductor and each capacitor. Thereby, the loss due to the resonance current flowing through the auxiliary inductor can be stably reduced.

(Embodiment 3)
FIG. 8 shows an example of the configuration of the power conversion device 100y according to the third embodiment. The switching power supply device 10y of the power conversion device 100y is driven by the secondary side phase shift method. Hereinafter, differences between the power conversion device 100y according to the third embodiment and the power conversion device 100x according to the second embodiment will be described. A duplicate description between the two is omitted as appropriate.

  The rectifier circuit of the switching power supply 10y conducts or interrupts the ninth switching element S9 for conducting or interrupting the forward current from the secondary winding N2 of the transformer T and the reverse current from the secondary winding N2. A tenth switching element S10 is further provided. The control device 20y fixes the phase of the primary side switching elements S1 to S4 and makes the phase of the secondary side switching elements S9 and S10 variable. The control device 20y switches the secondary side to the phase of the primary side switching elements S1 to S4 according to the output voltage supplied from the output voltage detection circuit 11 and / or the output current supplied from the output current detection circuit 12. The phase difference between the phases of the elements S9 and S10 is controlled.

  By fixing the phases of the switching elements S1 to S4 on the primary side, the phases of the auxiliary switches S5, S6, and S8 are also fixed. Thereby, the drive of the primary side circuit can be stabilized.

  1 may be combined with the secondary circuit of the switching power supply 10y shown in FIG. 8, and this may be driven by the secondary phase shift method.

(Embodiment 4)
Hereinafter, the fourth embodiment will be described. The description which overlaps between Embodiment 1-3 and Embodiment 4 is abbreviate | omitted suitably.

  FIG. 14 is a circuit diagram illustrating a configuration example of the power conversion device 100z according to the fourth embodiment.

  The power conversion device 100z in the fourth embodiment includes a switching circuit unit 1000.

  The switching circuit unit 1000 is connected to the other end of the secondary inductor.

  The switching circuit unit 1000 includes a secondary side switching element.

  In power conversion device 100z in the fourth embodiment, the smoothing circuit is connected to switching circuit unit 1000. The smoothing circuit smoothes the voltage output from the switching circuit unit 1000.

  In power conversion device 100z according to the fourth embodiment, control device 20z controls the on / off state of the secondary-side switching element of switching circuit unit 1000, thereby increasing the amplitude of at least one of the output voltage and output current from the smoothing circuit. Control.

  In the fourth embodiment, the load 30z may be a commercial power system.

  With the configuration of the fourth embodiment, a bidirectional DCAC converter capable of supplying power from the primary side to the secondary side and supplying power from the secondary side to the primary side can be realized.

  The secondary side switching element of the switching circuit unit 1000 includes a first bidirectional switching unit, a second bidirectional switching unit, a third bidirectional switching unit, and a fourth bidirectional switching unit.

  The first bidirectional switching unit is inserted between the first end of the smoothing circuit and the first end of the secondary winding. The first bidirectional switching unit includes a switching element S21.

  The second bidirectional switching unit is inserted between the second end of the smoothing circuit and the first end of the secondary winding. The second bidirectional switching unit includes a switching element S22.

  The third bidirectional switching unit is inserted between the first end of the smoothing circuit and the second end of the secondary winding. The third bidirectional switching unit includes a switching element S23.

  The fourth bidirectional switching unit is inserted between the second end of the smoothing circuit and the second end of the secondary winding. The fourth bidirectional switching unit includes a switching element S24.

  Each of the switching elements S21 to S24 may be configured by a bidirectional switch.

  Alternatively, each of the switching elements S21 to S24 may have a configuration in which two switching elements having opposite directions of flowing current are provided in parallel.

  FIG. 15A is a waveform diagram showing waveforms of an output voltage and an output current having a phase difference of 0 °.

  When the polarities of the output voltage Vo and the output current io are the same, the power supply mode is set. The power supply mode includes a mode in which the output voltage Vo and the output current io shown in (1) are positive, and a mode in which the output voltage Vo and the output current io shown in (3) are negative.

  FIG. 15B is a waveform diagram showing waveforms of an output voltage and an output current having a phase difference of 180 °.

  When the polarities of the output voltage Vo and the output current io are different, the power regeneration mode is set. In the power regeneration mode, the output voltage Vo shown in (2) is negative and the output current io is positive, and the output voltage Vo shown in (4) is positive and the output current io is negative. There is.

  FIG. 16 is a time chart of the power supply mode in the period T10 shown in FIG.

  FIG. 17 is a time chart of the power regeneration mode in the period T12 shown in FIG.

  In power conversion device 100z in the fourth embodiment, control device 20z selects at least one of switching element S21 and switching element S24 as the first ON time point in the first period in which the voltage of the secondary winding is positive. In (Ton1 or Ton4), switching from off to on.

  Further, the control device 20z sets at least one of the switching element S22 and the switching element S23 to the second on time point (Ton2 or Ton2) in the second period in which the voltage of the secondary winding following the first period is negative. In Ton6), switching from off to on.

  At this time, the amplitude of at least one of the output voltage or the output current from the smoothing circuit is controlled by shifting at least one of the first on time and the second on time.

  According to the above configuration, the amplitude of at least one of the output voltage and the output current can be controlled by controlling the switching elements S21 to S24 arranged on the secondary side of the power conversion device 100z. For this reason, in the bridge circuit on the primary side, processing for controlling the amplitude of at least one of the output voltage and the output current is not necessary. That is, the phase of the signal that drives the switching elements that constitute the bridge circuit can be fixed. For this reason, it is possible to prevent the circulating current from being generated in the bridge circuit on the primary side.

  By stopping the auxiliary switches S5, S6, and S8 according to the output voltage current condition, the current supply from the auxiliary inductor is stopped. Thereby, a current is supplied from the secondary inductor.

  FIG. 18 is a timing chart schematically showing an operation example of the switching power supply device according to the fourth embodiment.

  As shown in FIG. 18A, when the output current is small (light load), the operations of the auxiliary switches S5, S6, and S8 are validated.

  As shown in FIG. 18B, when the output current is large (when the load is heavy), the operations of the auxiliary switches S5, S6, and S8 are invalidated. As a result, the soft switching operation is realized only by the current supply from the secondary inductor.

  In addition, even when the output current is large (during heavy load), when the soft switching operation cannot be realized only by the current supply from the secondary inductor, the operation of the auxiliary switches S5, S6, and S8 is made effective. The amount of current may be increased. Thereby, the change rate of the voltage applied to switching element S1-S4 can be made smaller.

  FIG. 19 is a diagram illustrating three operation modes that occur according to the current phase of the secondary circuit.

  FIG. 19A shows an inverter mode (power supply mode) in which the current is in phase with the commercial voltage.

  FIG. 19B shows a converter mode (power regeneration mode) in which the current has a phase opposite to that of the commercial voltage.

  In FIG. 19, Ra and Rb indicate the effective range of control of the auxiliary switch.

  The setting conditions for the on / off operation of the auxiliary switch in the inverter mode and the converter mode may be uniquely determined by the absolute value of the current.

  Note that the same value may be set as the setting condition of the inverter mode and the converter mode. Alternatively, different values may be set for the setting conditions of the inverter mode and the converter mode, respectively.

  FIG. 19C shows a mixed mode in which the inverter mode and the converter mode are mixed. In the mixed mode, the setting condition of the on / off operation of the auxiliary switch is switched together with the switching between the inverter mode and the converter mode.

  FIG. 20 is a flowchart illustrating a method for generating a control signal for the auxiliary switch.

  In the inverter mode or the converter mode, as shown in FIG. 20A, the control signal for the auxiliary switch may be generated without considering the operation mode.

  In the mixed mode, as shown in FIG. 20B, the control signal for the auxiliary switch may be generated based on the step of determining the operation mode.

  FIG. 21 is a diagram schematically illustrating a configuration example of the control device 20z in FIG.

  The configuration of the fourth embodiment may be appropriately combined with the configuration described as the first to third embodiments.

  In the first to fourth embodiments, the setting conditions for the on / off operation of the auxiliary switch may be determined in advance by experiments or the like.

  Moreover, in Embodiment 1-4, you may comprise the secondary side inductor connected in series with the high frequency transformer with the coil which is a single component. Alternatively, the secondary inductor may be realized by a leakage inductance of a high frequency transformer.

  In the first to fourth embodiments, the voltage detection unit and the current detection unit may be provided on the primary side. Alternatively, the voltage detection unit and the current detection unit may be provided on both the primary side and the secondary side.

(Embodiment 5)
The power converters according to Embodiments 1 to 4 described above can be used for various purposes. Hereinafter, examples in which the power conversion devices according to Embodiments 1 to 4 are used in a power storage system, a vehicle, and a charger will be given. In addition, the power conversion device of the present disclosure can also be used in applications that require high-efficiency power conversion and insulation, for example, a data center power supply device.

  FIG. 9 shows a configuration example of a power storage system 400 having the power conversion device according to the first to fourth embodiments. A power storage system 400 illustrated in FIG. 9 includes a solar battery 200a, a storage battery 200b, a DC-DC converter 100a, a DC-DC converter 100b, and an inverter 300a. The storage battery 200b may be a stationary storage battery or a portable storage battery such as an in-vehicle battery. Solar cell 200a generates first DC power. The DC-DC converter 100a converts the first DC power into second DC power. Inverter 300a converts the second DC power into AC power. Alternatively, the DC-DC converter 100b converts the second direct-current power into direct-current power for storage and stores it in the storage battery 200b. At least one of DC-DC converter 100a and DC-DC converter 100b includes the power conversion device according to Embodiments 1 to 4.

  The storage battery 200b and the DC-DC converter 100b may be omitted. In this case, a solar power generation system without a power storage function is realized. Solar cell 200a and DC-DC converter 100a may be omitted. In this case, a power storage system without a power generation function is realized.

  FIG. 10 shows a configuration example of a vehicle 700 having the power conversion device according to the first to fourth embodiments. A vehicle 700 shown in FIG. 10 is, for example, a hybrid car (HV), a plug-in hybrid car (PHV), or an electric car (EV) on which a traveling motor 600 is mounted. Motor 600 may be a high-output motor capable of self-running or a travel assist motor mounted on a mild hybrid car. The motor 600 is, for example, an AC synchronous motor.

  A vehicle 700 shown in FIG. 10 includes a traveling battery 200c, an auxiliary battery 200d, a DC-DC converter 100c, a bidirectional DC-DC converter 150, an inverter 300b, and a motor 600. The traveling battery 200c is, for example, a storage battery such as a lithium ion battery or a nickel metal hydride battery. During power running, bidirectional DC-DC converter 150 converts the first DC power supplied from traveling battery 200c into second DC power. The inverter 300 b converts the second DC power into AC power and supplies the AC power to the motor 600. During regeneration, inverter 300b converts AC power generated based on deceleration energy into third DC power. Bidirectional DC-DC converter 150 converts the third DC power into battery DC power and charges battery for traveling 200c.

  The auxiliary battery 200d is, for example, a 12V output lead battery. In the mild hybrid car, the traveling battery 200c is designed to output 48V, for example. The 12V system to which the auxiliary battery 200d is connected and the 48V system to which the traveling battery 200c is connected are connected via the DC-DC converter 100c. The DC-DC converter 100c boosts the voltage of the auxiliary battery 200d to the voltage of the traveling battery 200c. Thus, when the capacity of the traveling battery 200c is insufficient, power can be supplied to the motor 600 from the auxiliary battery 200d. The DC-DC converter 100c steps down the voltage of the traveling battery 200c to the voltage of the auxiliary battery 200d. DC-DC converter 100c includes the power converters according to the first to fourth embodiments.

  FIG. 11 is a diagram showing a configuration of a charger 800 in which the power conversion device according to Embodiments 1 to 4 is used. A vehicle 700 shown in FIG. 11 has a plug-in charging function added to the vehicle shown in FIG. The charger 800 includes a rectifier circuit 810, a PFC circuit 820, and a DC-DC converter 100d. The rectifier circuit 810 rectifies the AC voltage supplied from the system 500. The PFC circuit 820 improves the power factor of the rectified power. The DC-DC converter 100d converts the input voltage from the PFC circuit 820 into a charging voltage. DC-DC converter 100d includes the power converters according to Embodiments 1 to 4. The charger 800 may be a charger installed outside the vehicle as shown in FIG. 11 or an in-vehicle charger mounted in the vehicle 700.

  As described above, the DC-DC converter used in power storage system 400, vehicle 700, or charger 800 includes the power conversion device according to the first to fourth embodiments. As a result, a simple, low-cost, low-loss power supply system can be constructed.

  The present disclosure has been described based on the embodiments. It will be understood by those skilled in the art that various modifications can be made to combinations of components and processing processes in the present disclosure, and such modifications are within the scope of the present disclosure.

  For example, the inverter on the primary side of the switching power supply device may be a half bridge type instead of a full bridge type. The rectifier circuit on the secondary side of the switching power supply device 10 may be a center tap type instead of a bridge type.

  The first capacitor C1 to the fourth capacitor C4 may not be lossless snubber capacitors, but may be the respective parasitic capacitances of the first switching element S1 to the fourth switching element S4. The first diode D1 to the fourth diode D4 may be parasitic diodes of the first switching element S1 to the fourth switching element S4.

  The fifth auxiliary switch S5 and the sixth auxiliary switch S6 may have other connection arrangements as long as they are arranged in the current path extending between the intermediate node Nc and the first node Na. FIG. 12 shows a connection example of the fifth auxiliary switch S5, the sixth auxiliary switch S6, and the first auxiliary inductor L1 between the intermediate node Nc and the first node Na. At this time, although the number of common reference potentials is reduced as compared with the switching power supply device 10 described in the first embodiment, the switching loss is stable as in the power conversion devices described in the first to fourth embodiments. Can be reduced. Further, the fifth auxiliary switch S5 and the sixth auxiliary switch S6 shown in FIG. 12 may be one bidirectional switching element. In other words, one of the fifth auxiliary switch S5 and the sixth auxiliary switch S6 in the switching power supply device described in the first to fourth embodiments may be omitted, and the other may be a bidirectional switching element. In this case, in the above description, ON / OFF of the fifth auxiliary switch S5 is read as ON / OFF of the first gate of the bidirectional switching element, and ON / OFF of the sixth auxiliary switch S6 is ON / OFF of the second gate of the bidirectional switching element. It can be read. Similarly, the seventh auxiliary switch S7 and the eighth auxiliary switch S8 can be replaced with bidirectional switching elements.

  In the present disclosure, the “bidirectional switch” may be a single bidirectional switching element or a circuit element configured by a plurality of switching elements. In the present disclosure, the “on state of the bidirectional switch” means a state in which a current flows in either direction of the bidirectional switch, and the “off state of the bidirectional switch” means any direction of the bidirectional switch. This means that no current flows.

  The present disclosure also includes a circuit capable of realizing the characteristic function of the present disclosure, similarly to the circuit configuration described above. For example, the present disclosure also includes an element such as a switching element (transistor), a resistor element, or a capacitor element connected in series or in parallel to a certain element within a range in which the same function as the above circuit configuration can be realized. It is. In other words, “connected” in the present disclosure is not limited to the case where two terminals (nodes) are directly connected, and the two terminals (nodes) are within a range in which a similar function can be realized. The case of being connected via an element is included.

  The power conversion device according to the present disclosure can be used for a DC-DC converter used in a power storage system, a vehicle, and the like.

  The power conversion device of the present disclosure is useful for, for example, a power conditioner of a stationary storage battery.

  100, 100x, 100y, 100z Power converter

Claims (16)

A first switching element; a second switching element connected in series to the first switching element; a first capacitor connected in parallel to the first switching element; and a second connected in parallel to the second switching element. A bridge circuit including a capacitor and converting an input DC voltage to a first AC voltage;
A first auxiliary switch having one end connected to a first node between the first switching element and the second switching element;
A first auxiliary inductor connected to the other end of the first auxiliary switch;
A control device for controlling on / off of the first switching element, the second switching element, and the first auxiliary switch;
A transformer including a primary winding connected to the bridge circuit, and a secondary winding electromagnetically coupled to the primary winding, the first AC voltage being converted to a second AC voltage;
A secondary inductor having one end connected to the secondary winding;
A switching circuit unit including a secondary side switching element connected to the other end of the secondary side inductor;
A smoothing circuit connected to the switching circuit unit and smoothing a voltage output from the switching circuit unit;
An output detection circuit for obtaining a detection value based on at least one of an output voltage and an output current from the smoothing circuit;
With
The control device controls the amplitude of at least one of the output voltage and the output current from the smoothing circuit by controlling on / off of the secondary side switching element of the switching circuit unit,
The controller is
When the detection value of the output detection circuit is equal to or lower than a predetermined set value, the first auxiliary switch is turned on until the second switching element is turned on after the first switching element is turned off. While the first switching element or the second switching element is turned on, the first auxiliary switch is turned off,
When the detection value of the output detection circuit exceeds the set value, the first auxiliary switch is maintained in an off state;
Power conversion device. The bridge circuit is
A first arm including the first switching element, the second switching element, the first capacitor, and the second capacitor;
A third switching element; a fourth switching element connected in series to the third switching element; a third capacitor connected in parallel to the third switching element; and a fourth connected in parallel to the fourth switching element. A second arm including a capacitor;
With
The power converter is
A second auxiliary switch having one end connected to a second node between the third switching element and the fourth switching element;
A second auxiliary inductor connected to the other end of the second auxiliary switch;
Further comprising
The control device further controls on / off of the third switching element, the fourth switching element, and the second auxiliary switch,
The control device
When the detection value of the output detection circuit is less than or equal to the set value, the second auxiliary switch is turned on between the time when the third switching element is turned off and the time when the fourth switching element is turned on. While the third switching element or the fourth switching element is turned on, the second auxiliary switch is turned off,
When the detection value of the output detection circuit exceeds the set value, the second auxiliary switch is maintained in an OFF state;
The power conversion device according to claim 1. A voltage source for supplying the DC voltage to the bridge circuit;
A third auxiliary switch connected between the voltage source and the first auxiliary inductor;
A fourth auxiliary switch connected between the voltage source and the second auxiliary inductor;
Further comprising
The control device further controls on / off of the third auxiliary switch and the fourth auxiliary switch,
The controller is
When the detection value of the output detection circuit is less than or equal to the set value, the third auxiliary switch is turned on between the time when the second switching element is turned off and the time when the first switching element is turned on. While the first switching element or the second switching element is turned on, the third auxiliary switch is turned off, and the fourth switching element is turned off until the third switching element is turned on. While the fourth auxiliary switch is turned on and the third switching element or the fourth switching element is turned on, the fourth auxiliary switch is turned off,
When the detection value of the output detection circuit exceeds the set value, the third auxiliary switch and the fourth auxiliary switch are maintained in an off state;
The power conversion device according to claim 2. A voltage source for supplying the DC voltage to the bridge circuit;
A third auxiliary switch connected between the voltage source and the first auxiliary inductor;
Further comprising
The second auxiliary inductor is connected between the second auxiliary switch and the third auxiliary switch;
The control device further controls on / off of the third auxiliary switch;
The controller is
When the detection value of the output detection circuit is less than or equal to the set value, the time between turning off the second switching element and turning on the first switching element, and after turning off the fourth switching element. Until the third switching element is turned on, the third auxiliary switch is turned on, the first switching element or the second switching element is turned on, and the third switching element or the second switching element is turned on. While the 4 switching elements are turned on, the third auxiliary switch is turned off,
If the detection value of the output detection circuit exceeds the set value, the third auxiliary switch is maintained in an off state;
The power conversion device according to claim 2. The voltage source includes a first voltage source capacitor and a second voltage source capacitor connected in series to the first voltage source capacitor;
The third auxiliary switch is connected to an intermediate node between the first voltage source capacitor and the second voltage source capacitor.
The power conversion device according to claim 3. The voltage source includes a first voltage source capacitor and a second voltage source capacitor connected in series to the first voltage source capacitor;
The third auxiliary switch and the fourth auxiliary switch are connected to an intermediate node between the first voltage source capacitor and the second voltage source capacitor.
The power conversion device according to claim 4. The first auxiliary switch is a first bidirectional switching element;
The controller is
When the detection value of the output detection circuit is equal to or less than a predetermined set value, the two gates of the first bidirectional switching element are between the time when the first switching element is turned off and the time when the second switching element is turned on. One of the two switching elements is turned on, and the other one of the two gates of the first bidirectional switching element is turned on between the time when the second switching element is turned off and the time when the first switching element is turned on. While the first switching element or the second switching element is turned on, the two gates of the first bidirectional switching element are turned off.
The power conversion device according to claim 1. The bridge circuit is
A first arm including the first switching element, the second switching element, the first capacitor, and the second capacitor;
A third switching element; a fourth switching element connected in series to the third switching element; a third capacitor connected in parallel to the third switching element; and a fourth connected in parallel to the fourth switching element. A second arm including a capacitor;
With
The power converter is
A second bidirectional switching element having one end connected to a second node between the third switching element and the fourth switching element;
A second auxiliary inductor connected to the other end of the second auxiliary switch;
Further comprising
The control device further controls on / off of the third switching element, the fourth switching element, and the second bidirectional switching element,
The control device
When the detection value of the output detection circuit is less than or equal to the set value, the time period between the two gates of the second bidirectional switching element between the time when the third switching element is turned off and the time when the fourth switching element is turned on. One is turned on, and the other one of the two gates of the second bidirectional switching element is turned on after the fourth switching element is turned off until the third switching element is turned on.
The power conversion device according to claim 7. The controller is
By turning on the first auxiliary switch, a resonance current flowing through the first auxiliary inductor, the first capacitor, and the second capacitor is generated,
The resonance current is not generated by turning off the first auxiliary switch.
The power conversion device according to claim 1. During the period in which the first switching element and the second switching element are in the off state, the current flowing through the secondary inductor causes the secondary inductor to store energy, and the other resonance current generated by the energy is Charging and discharging the first capacitor and the second capacitor;
The power conversion device according to claim 9. The reference terminal of the first switching element and the reference terminal of the first auxiliary switch are equipotential.
The power conversion device according to claim 1. The reference terminal of the first switching element and the reference terminal of the first auxiliary switch are equipotential;
The reference terminal of the third switching element and the reference terminal of the second auxiliary switch are equipotential;
The reference terminal of the second switching element and the reference terminal of the fourth switching element are equipotential.
The power conversion device according to claim 2. The reference terminal of the first switching element and the reference terminal of the first auxiliary switch are equipotential;
The reference terminal of the third switching element and the reference terminal of the second auxiliary switch are equipotential;
The reference terminal of the second switching element and the reference terminal of the fourth switching element are equipotential;
The reference terminal of the third auxiliary switch and the reference terminal of the fourth auxiliary switch are equipotential;
The power conversion device according to claim 3. The first switching element, the second switching element, the third switching element, the fourth switching element, the first auxiliary switch, the second auxiliary switch, the third auxiliary switch, and the fourth auxiliary switch are: Insulated Gate Bipolar Transistor, or Metal Oxide Semiconductor Field Effect Transistor,
The power conversion device according to claim 3. The smoothing circuit includes a first end and a second end,
The secondary side switching element of the switching circuit unit is:
A first bidirectional switching unit including a switching element S21 inserted between a first end of the smoothing circuit and a first end of the secondary winding;
A second bidirectional switching unit including a switching element S22 inserted between the second end of the smoothing circuit and the first end of the secondary winding;
A third bidirectional switching unit including a switching element S23 inserted between the first end of the smoothing circuit and the second end of the secondary winding;
A fourth bidirectional switching unit including a switching element S24 inserted between the second end of the smoothing circuit and the second end of the secondary winding;
including,
The power converter device in any one of Claims 1-14. At least one of the switching element S21 and the switching element S24 is switched from OFF to ON at a first ON time point in a first period in which the voltage of the secondary winding is positive,
At least one of the switching element S22 and the switching element S23 is switched from OFF to ON at a second ON time point in a second period in which the voltage of the secondary winding following the first period is negative,
Controlling the amplitude of at least one of the output voltage or the output current by shifting at least one of the first on time and the second on time;
The power conversion device according to claim 15.