Power conversion device and power conversion system

Abstract

To obtain a power conversion device capable of protecting a circuit in the event of sudden changes in an input voltage.SOLUTION: A power conversion device according to one embodiment of the present disclosure comprises a first power terminal, a switching circuit, a transformer, a rectifier circuit, a smoothing circuit, a power regeneration circuit, a control circuit, and a second power terminal. The power regeneration circuit comprises a diode circuit, a second capacitor, first and second regeneration switching elements, a second inductor, and a first diode. The control circuit is capable of turning on the first regenerative switching element and turning off the second regenerative switching element when the voltage at the first node rises and exceeds the threshold voltage. Between the two ends of the second winding, the first positive voltage and the first negative voltage occur alternately, and the threshold voltage is higher than the voltage corresponding to the average value of the first positive voltage and the voltage corresponding to the average value of the first negative voltage.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a power conversion device and a power conversion system for converting power.

Background Art

[0002] Some power conversion devices suppress the surge voltage generated in the rectifier circuit. For example, Patent Document 1 discloses a power conversion device that suppresses the surge voltage at various input voltages by changing a reference voltage based on the input voltage supplied to the switching circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a power conversion device, it is desired that the circuit can be protected even when the input voltage changes suddenly, and it is expected that a circuit for suppressing such a surge voltage can be protected.

[0005] It is desirable to provide a power conversion device and a power conversion system that can protect the circuit even when the input voltage changes suddenly.

Means for Solving the Problems

[0006] A power conversion device according to an embodiment of the present invention includes a first power terminal, a switching circuit, a transformer, a rectifier circuit, a smoothing circuit, a power regeneration circuit, a control circuit, and a second power terminal. The switching circuit is connected to the first power terminal. The transformer has a first winding and a second winding led from the switching circuit. The rectifier circuit is connected to the second winding and has one or more rectifier switching elements. The smoothing circuit includes a first inductor having one end and the other end, and a first capacitor having one end connected to the other end of the first inductor and the other end connected to a reference node. The power regeneration circuit is connected to the rectifier circuit and can regenerate the energy of the surge voltage generated in the rectifier circuit to the first capacitor. The control circuit can control the operations of the switching circuit, the rectifier circuit, and the power regeneration circuit. The second power terminal has a first connection terminal connected to the other end of the first inductor and one end of the first capacitor, and a second connection terminal connected to the reference node. The power regeneration circuit includes a diode circuit, a second capacitor, a first regeneration switching element, a second regeneration switching element, a second inductor, and a first diode. The diode circuit is provided in a path connecting the rectifier circuit and the first node and can allow current to flow toward the first node. The second capacitor has one end connected to the first node and the other end connected to the reference node. The first regeneration switching element has one end connected to the first node and the other end connected to the second node. The second regeneration switching element has one end connected to the second node and the other end connected to the reference node. The second inductor and the first diode are provided in a path connecting the second node and one end of the first capacitor. The control circuit can turn on the first regeneration switching element from the off state and turn off the second regeneration switching element from the on state when the voltage of the first node rises and the voltage of the first node exceeds a threshold voltage.When the input voltage input to the first power terminal is a voltage within the normal operating voltage range, a first positive voltage and a first negative voltage alternately occur across both ends of the second winding. The threshold voltage is higher than the voltage corresponding to the average value of the first positive voltage and the voltage corresponding to the average value of the first negative voltage in the rectifier circuit.

[0007] A power conversion system according to an embodiment of the present invention includes the above power conversion device.

Advantages of the Invention

[0008] According to the power conversion device and the power conversion system according to an embodiment of the present invention, the circuit can be protected even when the input voltage changes suddenly.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0011] <Embodiment> [Configuration Example] Figure 1 shows a configuration example of a power conversion system 1 including a power conversion device according to an embodiment of the present invention. The power conversion system 1 includes a high-voltage battery BH, a power conversion device 10, and a low-voltage battery BL. This power conversion system 1 is configured to convert the power supplied from the high-voltage battery BH and supply the converted power to the low-voltage battery BL.

[0012] The high-voltage battery BH is configured to store power. The high-voltage battery BH supplies power to the power conversion device 10.

[0013] The power conversion device 10 is configured to convert power by stepping down the voltage supplied from the high-voltage battery BH and supply the converted power to the low-voltage battery BL. The power conversion device 10 includes terminals T11, T12, a capacitor 11, a voltage sensor 12, a capacitor 13, a switching circuit 14, an inductor 15, a transformer 16, a rectifier circuit 17, a smoothing circuit 18, a power regeneration circuit 30, a voltage sensor 21, a control circuit 40, and terminals T21, T22. The high-voltage battery BH, the capacitor 11, the voltage sensor 12, the capacitor 13, the switching circuit 14, and the inductor 15 constitute the primary-side circuit of the power conversion system 1, and the rectifier circuit 17, the smoothing circuit 18, the power regeneration circuit 30, the voltage sensor 21, and the low-voltage battery BL constitute the secondary-side circuit of the power conversion system 1.

[0014] The terminals T11, T12 are configured to be supplied with voltage from the high-voltage battery BH. Inside the power conversion device 10, the terminal T11 is connected to the voltage line L11, and the terminal T12 is connected to the reference voltage line L12.

[0015] One end of the capacitor 11 is connected to the voltage line L11, and the other end is connected to the reference voltage line L12.

[0016] One end of the voltage sensor 12 is connected to the voltage line L11, and the other end is connected to the reference voltage line L12. The voltage sensor 12 is configured to detect the voltage VH on the voltage line L11 with reference to the voltage on the reference voltage line L12.

[0017] One end of the capacitor 13 is connected to the voltage line L11, and the other end is connected to the node N11.

[0018] The switching circuit 14 is configured to perform a switching operation based on the control signals G1 and G2. The switching circuit 14 has transistors Q1 and Q2. The transistors Q1 and Q2 are switching elements that perform switching operations based on the control signals G1 and G2 respectively. The transistors Q1 and Q2 are configured using, for example, N-type field effect transistors (FETs: Field Effect Transistors). Each of the transistors Q1 and Q2 has a body diode and a parasitic capacitor. For example, the anode of the body diode of transistor Q1 is connected to the source of the body of transistor Q1, and the cathode is connected to the drain of the body of transistor Q1. One end of the parasitic capacitor of transistor Q1 is connected to the source of the body of transistor Q1, and the cathode is connected to the drain of the body of transistor Q1. The same applies to transistor Q2. In this example, N-type field effect transistors are used, but any switching element may be used. The drain of transistor Q1 is connected to node N11, the source is connected to node N12, and the control signal G1 is supplied to the gate. The drain of transistor Q2 is connected to node N12, the source is connected to the reference voltage line L12, and the control signal G2 is supplied to the gate.

[0019] One end of the inductor 15 is connected to the voltage line L11, and the other end is connected to the winding 16A (described later) in the transformer 16.

[0020] The transformer 16 is configured to insulate the primary side circuit and the secondary side circuit, convert the AC voltage supplied from the primary side circuit by the turns ratio of the transformer 16, and supply the converted AC voltage to the secondary side circuit. The transformer 16 has windings 16A and 16B. The winding 16A is the primary winding of the transformer 16, one end is connected to the other end of the inductor 15, and the other end is connected to node N12. The winding 16B is the secondary winding of the transformer 16, one end is connected to the voltage line L21A (described later), and the other end is connected to node N13.

[0021] The rectifier circuit 17 is configured to rectify the AC voltage output from the winding 16B of the transformer 16. The rectifier circuit 17 includes transistors Q3, Q4 and snubber circuits SN13, SN14. The transistors Q3, Q4 are switching elements that perform switching operations based on control signals G3, G4 respectively. Similar to the transistors Q1, Q2, the transistors Q3, Q4 are configured using, for example, N-type field effect transistors. Each of the transistors Q3, Q4 has a body diode and a parasitic capacitor, similar to the transistors Q1, Q2. The drain of the transistor Q3 is connected to the node N13, the source is connected to the reference voltage line L22, and the control signal G3 is supplied to the gate. The drain of the transistor Q4 is connected to the voltage line L21A, the source is connected to the reference voltage line L22, and the control signal G4 is supplied to the gate. The snubber circuit SN3 is configured to suppress the voltage change across the drain-source voltage of the transistor Q3. The snubber circuit SN4 is configured to suppress the voltage change across the drain-source voltage of the transistor Q4. Each of the snubber circuits SN3, SN4 has a resistor element and a capacitor connected in series. One end of the snubber circuit SN3 is connected to the drain of the transistor Q3, and the other end is connected to the source of the transistor Q3. One end of the snubber circuit SN4 is connected to the drain of the transistor Q4, and the other end is connected to the source of the transistor Q4.

[0022] The smoothing circuit 18 is configured to smooth the voltage rectified by the rectifier circuit 17. The smoothing circuit 18 includes an inductor 19 and a capacitor 20. One end of the inductor 19 is connected to the voltage line L21A, and the other end is connected to the voltage line L21B. One end of the capacitor 20 is connected to the voltage line L21B, and the other end is connected to the reference voltage line L22.

[0023] The power regeneration circuit 30 is configured to regenerate the energy of the surge voltage generated in the transistors Q3, Q4 of the rectifier circuit 17 to the capacitor 20.

[0024] Figure 2 shows a configuration example of the power regeneration circuit 30. Figure 2 depicts the secondary-side circuit of the power conversion system 1 including the power regeneration circuit 30. The power regeneration circuit 30 includes diodes 31 and 32, a capacitor 33, a voltage sensor 34, transistors Q5 and Q6, an inductor 35, and a diode 36.

[0025] The anode of diode 31 is connected to node N13, and the cathode is connected to node N1. One end of diode 32 is connected to voltage line L21A, and the cathode is connected to node N1. One end of capacitor 33 is connected to node N1, and the other end is connected to the reference voltage line L22. One end of voltage sensor 34 is connected to node N1, and the other end is connected to the reference voltage line L22. The voltage sensor 34 is configured to detect the voltage VSNB at node N1 with reference to the voltage on the reference voltage line L22.

[0026] Transistors Q5 and Q6 are switching elements that perform switching operations based on control signals G5 and G6 respectively. Transistors Q5 and Q6 are configured using, for example, N-type field-effect transistors in the same manner as transistors Q1 to Q4. Each of transistors Q5 and Q6 has a body diode and a parasitic capacitor in the same manner as transistors Q1 to Q4. The drain of transistor Q5 is connected to node N1, the source is connected to node N2, and the control signal G5 is supplied to the gate. The drain of transistor Q6 is connected to node N2, the source is connected to the reference voltage line L22, and the control signal G6 is supplied to the gate.

[0027] One end of inductor 35 is connected to node N2, and the other end is connected to the anode of diode 36. The inductor 35 can use, for example, a metal integral molding type. Thereby, in the power conversion system 1, it is possible to reduce the noise called so-called coil buzzing.

[0028] The anode of diode 36 is connected to the other end of inductor 35, and the cathode is connected to one end of capacitor 20.

[0029] With this configuration, the power regeneration circuit 30 can regenerate the energy of the surge voltage generated in the transistors Q3 and Q4 of the rectifier circuit 17 to the capacitor 20.

[0030] One end of the voltage sensor 21 (FIG. 1) is connected to the voltage line L21B, and the other end is connected to the reference voltage line L22. The voltage sensor 21 is configured to detect the voltage VL on the voltage line L21B with reference to the voltage on the reference voltage line L22.

[0031] The control circuit 40 is configured to control the operation of the power conversion device 10 based on the voltage VH detected by the voltage sensor 12, the voltage VL detected by the voltage sensor 21, and the voltage VSNB detected by the voltage sensor 34 of the power regeneration circuit 30. The control circuit 40 is configured using, for example, a microcontroller or the like.

[0032] The control circuit 40 controls the operations of the transistors Q1 to Q4 using the control signals G1 to G4 so that the voltage VL maintains a predetermined voltage based on, for example, the voltage VL detected by the voltage sensor 21. Further, the control circuit 40 controls the operations of the transistors Q5 and Q6 using the control signals G5 and G6 so that the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the rectifier circuit 17 to the capacitor 20 based on, for example, the voltage VSNB detected by the voltage sensor 34 of the power regeneration circuit 30. Further, the control circuit 40 controls the operation of the power conversion device 10 so as to stop the operation of the power conversion device 10 when the voltage VH exceeds the maximum voltage Vovp that exceeds the normal operating voltage range based on, for example, the voltage VH detected by the voltage sensor 12. In this example, the normal operating voltage range is in the range of 150 V or more and 300 V or less. And the maximum voltage Vovp is 400 V in this example.

[0033] As shown in FIG. 2, the control circuit 40 includes a voltage dividing circuit 41, a threshold voltage generating circuit 42, a comparator 43, a pulse signal generating circuit 44, a logical product circuit 45, and a control signal generating circuit 46.

[0034] In this example, the voltage dividing circuit 41 is configured to divide the voltage VSNB using a plurality of resistive elements. The threshold voltage generation circuit 42 is configured to generate a threshold voltage Vth.

[0035] The comparator 43 is configured to generate a signal CMP by comparing the voltage divided by the voltage dividing circuit 41 with the threshold voltage Vth. The comparator 43 is a hysteresis comparator, the positive input terminal is connected to the voltage dividing circuit 41, the negative input terminal is connected to the threshold voltage generation circuit 42, and the output terminal is connected to the logical product circuit 45.

[0036] FIG. 3 shows an operation example of the voltage dividing circuit 41, the threshold voltage generation circuit 42, and the comparator 43. The horizontal axis represents the voltage VSNB, and the vertical axis represents the signal CMP. When the signal CMP is at a low level, if the voltage VSNB rises and the voltage VSNB exceeds the threshold voltage VthH, the comparator 43 changes the signal CMP from a low level to a high level. When the signal CMP is at a high level, if the voltage VSNB drops and the voltage VSNB falls below the threshold voltage VthL, the comparator 43 changes the signal CMP from a high level to a low level. The threshold voltage VthL and the threshold voltage VthH are determined by the threshold voltage Vth generated by the threshold voltage generation circuit, the hysteresis amount (VthH - VthL), and the voltage division ratio of the voltage dividing circuit 41. Specifically, the threshold voltage VthL and the threshold voltage VthH are expressed using the following equations. VthH = 1 / voltage division ratio × Vth VthL = 1 / voltage division ratio × {Vth - (VthH - VthL)} In this way, the comparator 43 is configured to generate the signal CMP using the hysteresis characteristic.

[0037] The pulse signal generation circuit 44 is configured to generate a pulse signal PLS synchronized with the control signals G1 and G2. The AND circuit 45 is configured to obtain the logical product of the signal CMP and the pulse signal PLS. The control signal generation circuit 46 is configured to generate the control signals G5 and G6 based on the output signal of the AND circuit 45.

[0038] With this configuration, in the power regeneration circuit 30, the capacitor 33 is charged when the energy of the surge voltage generated in the rectifier circuit 17 flows in, and the voltage VSNB at the node N1 increases. Then, in the power regeneration circuit 30, when this voltage VSNB exceeds the threshold voltage VthH, the transistor Q5 turns on and the transistor Q6 turns off, so that the energy of the incoming surge voltage is regenerated to the capacitor 20. The voltage across both ends of the winding 16B of the transformer 16 is an alternating voltage that transitions between the voltage VP and the voltage VM as shown in FIG. 4. This alternating voltage is the voltage at the node N13 with reference to the potential of the voltage line L21A. The voltage VP is the average voltage during the period when the alternating voltage is a positive voltage, and the voltage VM is the average voltage during the period when the alternating voltage is a negative voltage. The voltages VP and VM can change according to the voltage VH. Specifically, when the voltage VH is small, as shown in FIG. 4(A), the absolute value of the voltage VP becomes large and the absolute value of the voltage VM becomes small. When the voltage VH is large, as shown in FIG. 4(B), the absolute value of the voltage VP becomes small and the absolute value of the voltage VM becomes large. The higher the absolute value of the voltage VP, the higher the voltage at the drain of the transistor Q3, and the higher the absolute value of the voltage VM, the higher the voltage at the drain of the transistor Q4. The threshold voltages VthH and VthL are set to voltages higher than the voltages corresponding to the voltage VP at the drain of the transistor Q3 and the voltage corresponding to the voltage VM at the drain of the transistor Q4 when the voltage VH is within the normal operating voltage range. Thereby, in the power regeneration circuit 30, when the voltage VH is within the normal operating voltage range, the diodes 31 and 32 do not turn on due to this voltage VP. Therefore, in the power regeneration circuit 30, when the voltage VH exceeds the normal operating voltage range, it is possible to suppress a sudden increase in the regenerated power.

[0039] Also, the threshold voltages VthH and VthL are set to a voltage lower than the larger voltage among the voltage corresponding to the voltage VP at the drain of the transistor Q3 and the voltage corresponding to the voltage VM at the drain of the transistor Q4 when the voltage VH is the maximum voltage Vovp (e.g., 400V) exceeding the normal operating voltage range. Thereby, in the power regeneration circuit 30, when the voltage VH is close to the maximum voltage Vovp, the diodes 31 and 32 are turned on.

[0040] The terminals T21 and T22 (FIG. 1) are configured to supply the voltage generated by the power conversion device 10 to the low-voltage battery BL. Inside the power conversion device 10, the terminal T21 is connected to the voltage line L21B, and the terminal T22 is connected to the reference voltage line L22. Also, the terminal T21 is connected to the positive terminal of the low-voltage battery BL, and the terminal T22 is connected to the negative terminal of the low-voltage battery BL.

[0041] The low-voltage battery BL is configured to store the power supplied from the power conversion device 10.

[0042] With this configuration, in the power conversion system 1, the power supplied from the high-voltage battery BH is converted, and a power conversion operation of supplying the converted power to the low-voltage battery BL is performed.

[0043] Here, terminals T11 and T12 correspond to a specific example of the "first power terminal" in one embodiment of the present disclosure. The switching circuit 14 corresponds to a specific example of the "switching circuit" in one embodiment of the present disclosure. The transformer 16 corresponds to a specific example of the "transformer" in one embodiment of the present disclosure. The winding 16A corresponds to a specific example of the "first winding" in one embodiment of the present disclosure. The winding 16B corresponds to a specific example of the "second winding" in one embodiment of the present disclosure. The rectifier circuit 17 corresponds to a specific example of the "rectifier circuit" in one embodiment of the present disclosure. The smoothing circuit 18 corresponds to a specific example of the "smoothing circuit" in one embodiment of the present disclosure. The inductor 19 corresponds to a specific example of the "first inductor" in one embodiment of the present disclosure. The capacitor 20 corresponds to a specific example of the "first capacitor" in one embodiment of the present disclosure. The reference node corresponds to a specific example of the "reference voltage line L22" in one embodiment of the present disclosure. The power regeneration circuit 30 corresponds to a specific example of the "power regeneration circuit" in one embodiment of the present disclosure. Terminals T21 and T22 correspond to a specific example of the "second power terminals" in one embodiment of the present disclosure. The control circuit 40 corresponds to a specific example of the "control circuit" in one embodiment of the present disclosure.

[0044] Diodes 31 and 32 correspond to a specific example of the "diode circuit" in one embodiment of the present disclosure. Capacitor 33 corresponds to a specific example of the "second capacitor" in one embodiment of the present disclosure. Transistor Q5 corresponds to a specific example of the "first regenerative switching element" in one embodiment of the present disclosure. Transistor Q6 corresponds to a specific example of the "second regenerative switching element" in one embodiment of the present disclosure. Inductor 35 corresponds to a specific example of the "second inductor" in one embodiment of the present disclosure. Diode 36 corresponds to a specific example of the "first diode" in one embodiment of the present disclosure. Node N1 corresponds to a specific example of the "first node" in one embodiment of the present disclosure. Node N2 corresponds to a specific example of the "second node" in one embodiment of the present disclosure. Transistor Q3 corresponds to a specific example of the "first rectifying switching element" in one embodiment of the present disclosure. Transistor Q4 corresponds to a specific example of the "second rectifying switching element" in one embodiment of the present disclosure. Diode 31 corresponds to a specific example of the "second diode" in one embodiment of the present disclosure. Diode 32 corresponds to a specific example of the "third diode" in one embodiment of the present disclosure.

[0045] [Operation and Action] Subsequently, the operation and action of the power conversion system 1 of this embodiment will be described.

[0046] (Overall Operation Outline) First, referring to FIG. 1, the overall operation outline of the power conversion system 1 will be described. The control circuit 40 generates control signals G1 to G4 based on the voltage VL. The switching circuit 14 performs a switching operation based on the control signals G1 and G2, and the rectifier circuit 17 performs a switching operation based on the control signals G3 and G4. Thereby, the power conversion device 10 converts the power supplied from the high-voltage battery BH and supplies the converted power to the low-voltage battery BL. The control circuit 40 generates control signals G5 and G6 based on the voltage VSNB. In the power regeneration circuit 30, the transistor Q5 performs a switching operation based on the control signal G5, and the transistor Q6 performs a switching operation based on the control signal G6. Thereby, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the rectifier circuit 17 to the capacitor 20.

[0047] (Detailed operation) Hereinafter, an operation example of the power conversion system 1 will be described in detail. First, the operation when the voltage VH is the lower limit voltage (for example, 150V) of the normal operation voltage range will be described, and then the operation when the voltage VH is the upper limit voltage (for example, 300V) of the normal operation voltage range will be described.

[0048] FIG. 5 shows an operation example of the power conversion system 1 when the voltage VH is the lower limit voltage (e.g., 150V) of the normal operating voltage range. (A) to (D) respectively show the waveforms of the control signals G1 to G4, (E) shows the waveform of the drain-source voltage VdsQ3 of the transistor Q3, (F) shows the waveform of the drain-source voltage VdsQ4 of the transistor Q4, (G) shows the waveform of the voltage VSNB across the capacitor 33 of the power regeneration circuit 30, (H) shows the waveform of the signal CMP, (I) shows the waveform of the pulse signal PLS, (J) and (K) respectively show the waveforms of the control signals G5 and G6, and (L) shows the waveform of the regeneration current IL flowing through the inductor 35 of the power regeneration circuit 30. In FIGS. 5(A) to (D), (J), and (K), the control signals G1 to G6 are illustrated using the gate-source voltages Vgs of the transistors Q1 to Q6. Note that the voltage VSNB shown in FIGS. 5(E) and (F) actually has a waveform as shown in FIG. 5(G), but in FIGS. 5(E) and (F), it is drawn as a straight line for the convenience of the voltage scale.

[0049] Based on the voltage VL, the control circuit 40 generates control signals G1 to G4 (Figs. 5(A) to (D)). The control signal G1 and the control signal G2 are controlled such that either one of them becomes high level. At this time, a dead time Td is provided for the control signal G1 and the control signal G2. During this dead time Td, both the control signals G1 and G2 become low level. Similarly, the control signal G3 and the control signal G4 are controlled such that either one of them becomes high level. At this time, a dead time Td is provided for the control signal G3 and the control signal G4. In this example, the control circuit 40 changes the control signal G2 from low level to high level at timing t13, changes the control signal G2 from high level to low level at timing t14, changes the control signal G1 from low level to high level at timing t15, and changes the control signal G1 from high level to low level at timing t18 (Figs. 5(A) and (B)). Similarly, the control circuit 40 changes the control signal G3 from low level to high level at timing t13, changes the control signal G3 from high level to low level at timing t14, changes the control signal G4 from low level to high level at timing t15, and changes the control signal G4 from high level to low level at timing t18 (Figs. 5(C) and (D)). The control circuit 40 repeats such an operation in a switching period T. The power conversion device 10 performs a power conversion operation of converting the power supplied from the high-voltage battery BH and supplying the converted power to the low-voltage battery BL by performing a switching operation based on such control signals G1 to G4. Then, the power conversion device 10 controls the duty ratios of the control signals G1 to G4 so that the voltage VL maintains a predetermined voltage.

[0050] The power regeneration circuit 30 operates to regenerate the energy of the surge voltage generated in the transistor Q3. The energy of the surge voltage generated in the transistor Q3 is supplied to the capacitor 33 of the power regeneration circuit 30 via the diode 31 and is temporarily stored in this capacitor 33. The control circuit 40 generates control signals G5 and G6 based on the voltage VSNB of the capacitor 33. Thereby, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the transistor Q3.

[0051] For example, in this example, at timing t11, when the control circuit 40 changes the control signal G3 from a high level to a low level (Fig. 5(C)), in the transistor Q3, current flows through the body diode. Thereafter, due to the reverse recovery operation of the body diode, the body diode of the transistor Q3 changes from the on state to the off state. As a result, the drain-source voltage VdsQ3 of this transistor Q3 rises from 0V (Fig. 5(E)). The drain-source voltage VdsQ3 transiently exceeds the voltage VSNB of the capacitor 33 at timing t12. During the period when the drain-source voltage VdsQ3 exceeds the voltage VSNB, the diode 31 becomes conductive, and current flows into the capacitor 33 through this diode 31. In this way, the capacitor 33 is transiently charged, and the voltage VSNB of the capacitor 33 rises (Fig. 5(G)). The voltage VSNB after the rise is lower than the threshold voltage VthH in this example. Thereafter, during the period from when the control signal G1 changes from a high level to a low level until the control signal G3 changes from a low level to a high level, the drain-source voltage VdsQ3 of this transistor Q3 becomes 0V (Fig. 5(E)). Thereafter, at timing t13, when the control circuit 40 changes the control signal G3 from a low level to a high level (Fig. 5(C)), the transistor Q3 changes from the off state to the on state.

[0052] Similarly, when the control circuit 40 changes the control signal G3 from a high level to a low level at timing t14 (Fig. 5(C)), in the transistor Q3, current flows through the body diode. Thereafter, due to the reverse recovery operation of the body diode, the body diode of the transistor Q3 changes from the on state to the off state. As a result, the drain-source voltage VdsQ3 of this transistor Q3 rises from 0V (Fig. 5(E)). The drain-source voltage VdsQ3 becomes transiently high at timing t16, and the diode 31 turns on. Thereby, the capacitor 33 is transiently charged, and the voltage VSNB of the capacitor 33 rises (Fig. 5(G)). In this example, at timing t17, this voltage VSNB exceeds the threshold voltage VthH. The control circuit 40 generates the control signals G5 and G6 based on this voltage VSNB.

[0053] At timing t17 when the voltage VSNB exceeds the threshold voltage VthH, the comparator 43 changes the signal CMP from a low level to a high level (Fig. 5(H)). The pulse signal generation circuit 44 generates a pulse signal PLS synchronized with the control signals G1 and G2 (Fig. 5(I)). In this example, the rising timing of the pulse signal PLS is the same as the rising timing of the control signal G2. The logical product circuit 45 calculates the logical product of the signal CMP and the pulse signal PLS (Fig. 5(H), (I)). In Fig. 5(H) and (I), the shaded period is the period during which both the signal CMP and the pulse signal PLS are at a high level. The control signal generation circuit 46 generates the control signals G5 and G6 based on the output signal of this logical product circuit 45 (Fig. 5(J), (K)). The control signals G5 and G6 are controlled such that either one of them becomes a high level. At that time, a dead time Td is provided for the control signals G5 and G6.

[0054] At timing t19, the control signal generation circuit 46 changes the control signal G6 from a high level to a low level (Fig. 5(K)). As a result, the transistor Q6 changes from the on state to the off state. Then, at timing t20 when a dead time Td has elapsed from this timing t19, the control signal generation circuit 46 changes the control signal G5 from a low level to a high level (Fig. 5(J)). Thereby, the transistor Q5 changes from the off state to the on state, and a regenerative current IL flows from the capacitor 33, through the transistor Q5, the inductor 35, and the diode 36, toward the capacitor 20 (Fig. 5(L)). That is, the energy of the surge voltage generated in the transistor Q3 is once stored in the capacitor 33 of the power regeneration circuit 30 and then regenerated to the capacitor 20. During the period from timing t20 to t21, the regenerative current IL increases. Since the capacitor 33 is discharged, the voltage VSNB of the capacitor 33 decreases toward the threshold voltage VthL (Fig. 5(G)).

[0055] At timing t21, when the voltage VSNB reaches the threshold voltage VthL, the comparator 43 changes the signal CMP from a high level to a low level (Fig. 5(H)). Thereby, the control signal generation circuit 46 changes the control signal G5 from a high level to a low level (Fig. 5(J)). As a result, the transistor Q5 changes from the on state to the off state. Since the discharge of the capacitor 33 stops, the voltage VSNB maintains the same voltage as the threshold voltage VthL (Fig. 5(G)). Then, at timing t22 when a dead time Td has elapsed from this timing t21, the control signal generation circuit 46 changes the control signal G6 from a low level to a high level (Fig. 5(K)). Thereby, the transistor Q6 changes from the off state to the on state. During the period from timing t21 to t23, the regenerative current IL decreases (Fig. 5(L)).

[0056] In this way, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the transistor Q3.

[0057] FIG. 6 shows an operation example of the power conversion system 1 when the voltage VH is the upper limit voltage (e.g., 300 V) of the normal operating voltage range.

[0058] Similar to the case of FIG. 5, the control circuit 40 generates control signals G1 to G4 based on the voltage VL (FIGS. 6(A) to (D)). In this example, the control circuit 40 changes the control signal G2 from a low level to a high level at timing t32, changes the control signal G2 from a high level to a low level at timing t34, changes the control signal G1 from a low level to a high level at timing t35, and changes the control signal G1 from a high level to a low level at timing t36 (FIGS. 6(A) and (B)). Similarly, the control circuit 40 changes the control signal G3 from a low level to a high level at timing t32, changes the control signal G3 from a high level to a low level at timing t34, changes the control signal G4 from a low level to a high level at timing t35, and changes the control signal G4 from a high level to a low level at timing t36 (FIGS. 6(C) and (D)). The control circuit 40 repeats such an operation at the switching period T. The power conversion device 10 performs a power conversion operation of converting the power supplied from the high-voltage battery BH and supplying the converted power to the low-voltage battery BL by performing a switching operation based on such control signals G1 to G4. Then, the power conversion device 10 controls the duty ratios of the control signals G1 to G4 so that the voltage VL maintains a predetermined voltage.

[0059] The power regeneration circuit 30 operates to regenerate the energy of the surge voltage generated in the transistor Q4. The energy of the surge voltage generated in the transistor Q4 is supplied to the capacitor 33 of the power regeneration circuit 30 via the diode 32 and is temporarily stored in this capacitor 33. The control circuit 40 generates control signals G5 and G6 based on the voltage VSNB of the capacitor 33. Thereby, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the transistor Q4.

[0060] For example, in this example, at timing t31, when the control circuit 40 changes the control signal G4 from a high level to a low level (Fig. 6(D)), in the transistor Q4, current flows through the body diode. Thereafter, due to the reverse recovery operation of the body diode, the body diode of the transistor Q4 changes from the on state to the off state. As a result, the drain-source voltage VdsQ4 of this transistor Q4 rises from 0V (Fig. 6(F)). The drain-source voltage VdsQ4 transiently exceeds the voltage VSNB of the capacitor 33 at timing t33. During the period when the drain-source voltage VdsQ4 exceeds the voltage VSNB, the diode 32 becomes on, and current flows into the capacitor 33 through this diode 32. In this way, the capacitor 33 is transiently charged, and the voltage VSNB of the capacitor 33 rises (Fig. 6(G)). The voltage VSNB after the rise is lower than the threshold voltage VthH in this example. Thereafter, during the period from when the control signal G2 changes from a high level to a low level until the control signal G4 changes from a low level to a high level, the drain-source voltage VdsQ4 of this transistor Q4 becomes 0V (Fig. 6(F)). Thereafter, at timing t35, when the control circuit 40 changes the control signal G4 from a low level to a high level (Fig. 6(D)), the transistor Q4 changes from the off state to the on state.

[0061] Similarly, at timing t36, when the control circuit 40 changes the control signal G4 from a high level to a low level (Fig. 6(D)), in the transistor Q4, current flows through the body diode. Thereafter, due to the reverse recovery operation of the body diode, the body diode of the transistor Q4 changes from the on state to the off state. As a result, the drain-source voltage VdsQ4 of this transistor Q4 rises from 0V (Fig. 6(F)). The drain-source voltage VdsQ4 becomes transiently high at timing t38, and the diode 32 becomes on. As a result, the capacitor 33 is transiently charged, and the voltage VSNB of the capacitor 33 rises (Fig. 6(G)). In this example, at timing t39, this voltage VSNB exceeds the threshold voltage VthH.

[0062] At timing t39 when the voltage VSNB exceeds the threshold voltage VthH, the comparator 43 changes the signal CMP from low level to high level (Fig. 6(H)). The AND circuit 45 calculates the logical product of the signal CMP and the pulse signal PLS (Fig. 6(H), (I)). In Fig. 6(H), (I), the shaded period is the period when both the signal CMP and the pulse signal PLS are at high level. The control signal generation circuit 46 generates control signals G5, G6 based on the output signal of this AND circuit 45 (Fig. 6(J), (K)).

[0063] At timing t37, the control signal generation circuit 46 changes the control signal G6 from high level to low level (Fig. 6(K)). As a result, the transistor Q6 changes from the on state to the off state. Then, at timing t40 when a dead time Td has elapsed from this timing t37, the control signal generation circuit 46 changes the control signal G5 from low level to high level (Fig. 6(J)). As a result, the transistor Q5 changes from the off state to the on state, and a regenerative current IL flows from the capacitor 33 through the transistor Q5, the inductor 35, and the diode 36 toward the capacitor 20 (Fig. 6(L)). That is, the energy of the surge voltage generated in the transistor Q3 is once stored in the capacitor 33 of the power regeneration circuit 30 and then regenerated to the capacitor 20. During the period from timing t40 to t41, the regenerative current IL rises. Since the capacitor 33 is discharged, the voltage VSNB of the capacitor 33 decreases toward the threshold voltage VthL (Fig. 6(G)).

[0064] At timing t41, when the voltage VSNB reaches the threshold voltage VthL, the comparator 43 changes the signal CMP from high level to low level (Fig. 6(H)). As a result, the control signal generation circuit 46 changes the control signal G5 from high level to low level (Fig. 6(J)). Consequently, the transistor Q5 changes from the on state to the off state. Since the discharge of the capacitor 33 stops, the voltage VSNB maintains the same voltage as the threshold voltage VthL (Fig. 6(G)). Then, at timing t42 when a dead time Td has elapsed from this timing t41, the control signal generation circuit 46 changes the control signal G6 from low level to high level (Fig. 6(K)). As a result, the transistor Q6 changes from the off state to the on state. During the period of timings t41 to t43, the regenerative current IL decreases (Fig. 6(L)).

[0065] In this way, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the transistor Q4.

[0066] In this manner, when the voltage VH is a low voltage within the normal operating voltage range, as shown in Fig. 5, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the transistor Q3. Also, when the voltage VH is a high voltage within the normal operating voltage range, as shown in Fig. 6, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the transistor Q4.

[0067] Next, the operation of the power conversion system 1 when the voltage VH is higher than the normal operating voltage range will be described.

[0068] FIG. 7 shows an operation example of the power conversion system 1 when the voltage VH is higher than the normal operating voltage range and lower than the maximum voltage Vovp. (A) shows the waveform of the voltage VH, (B) to (E) show the waveforms of the control signals G1 to G4 respectively, (F) shows the waveform of the drain-source voltage VdsQ3 of the transistor Q3, (G) shows the waveform of the drain-source voltage VdsQ4 of the transistor Q4, (H) shows the waveform of the voltage VSNB across the capacitor 33 of the power regeneration circuit 30, (I) shows the waveform of the signal CMP, (J) shows the waveform of the pulse signal PLS, (K) and (L) show the waveforms of the control signals G5 and G6 respectively, and (M) shows the waveform of the regeneration current IL flowing through the inductor 35 of the power regeneration circuit 30.

[0069] In this example, the voltage VH is a voltage expressed by the following equation. VthH×Np / Ns < VH ≦ Vovp Here, Np is the number of turns of the winding 16A, and Ns is the number of turns of the winding 16B. That is, "VthH×Np / Ns" is the voltage obtained by converting the threshold voltage VthH to the voltage at the terminals T11 and T12.

[0070] As shown in FIG. 7(A), in this example, the voltage VH is rising toward the maximum voltage Vovp. Similar to the cases of FIGS. 5 and 6, the control circuit 40 generates the control signals G1 to G4 based on the voltage VL (FIGS. 7(B) to (E)).

[0071] In this example, since the voltage VH is gradually increasing, the voltage across both ends of the winding 16B of the transformer 16 also gradually increases. Therefore, the drain-source voltage VdsQ4 of the transistor Q4 gradually increases during the period when the transistor Q4 is in the off state and exceeds the voltage VSNB of the capacitor 33 (Fig. 7(G)). When the drain-source voltage VdsQ4 exceeds the voltage VSNB, the diode 32 becomes conductive, the capacitor 33 is charged, and the voltage VSNB increases (Fig. 7(H)). In this example, except for the first period in Fig. 7, since the voltage VSNB is higher than the threshold voltage VthH, the comparator 43 maintains the signal CMP at a high level (Fig. 7(I)). The logic AND circuit 45 calculates the logical AND of this signal CMP and the pulse signal PLS (Fig. 7(I), (J)). Since the signal CMP is maintained at a high level, the output signal of the logic AND circuit 45 has the same waveform as the pulse signal PLS. The control signal generation circuit 46 generates control signals G5 and G6 based on the output signal of this logic AND circuit 45 (Fig. 7(K), (L)). For example, at the timing t51, the control signal generation circuit 46 changes the control signal G6 from a high level to a low level, and at the timing t52 after the dead time Td has elapsed from the timing t51, the control signal G5 is changed from a low level to a high level. Then, at the timing t53, the control signal generation circuit 46 changes the control signal G5 from a high level to a low level, and at the timing t54 after the dead time Td has elapsed from the timing t53, the control signal G6 is changed from a low level to a high level. The transistors Q5 and Q6 operate according to these control signals G5 and G6. During the period when the control signal G5 is at a high level, the regeneration current IL increases and then decreases (Fig. 7(M)).

[0072] In the power conversion system 1, a pulse signal generation circuit 44 and a logical product circuit 45 are provided to calculate the logical product of the signal CMP and the pulse signal PLS, and control signals G5 and G6 are generated based on the output signal of this logical product circuit 45. As a result, as in the example of FIG. 7, even when the signal CMP maintains a high level, the power regeneration circuit 30 limits the maximum on-time according to the pulse signal PLS and regenerates power as shown in FIGS. 7(I) to (M). Thereby, in the power conversion system 1, the regenerative power can be limited, and an increase in the regenerative power can be suppressed. As a result, in the power conversion system 1, the power regeneration circuit 30 can be protected.

[0073] That is, for example, if the pulse signal generation circuit 44 and the logical product circuit 45 are not provided, the control signal G5 may maintain a high level, so there is a possibility that the regenerative power becomes too large. In this case, the power regeneration circuit 30 may be damaged. In the power conversion system 1, since the pulse signal generation circuit 44 and the logical product circuit 45 are provided, an increase in the regenerative power can be suppressed. As a result, in the power conversion system 1, the power regeneration circuit 30 can be protected.

[0074] To protect the power regeneration circuit 30, for example, there may be a method of configuring the power regeneration circuit 30 using components that can withstand large power. However, in this case, the component size becomes large and the cost increases. On the other hand, in the power conversion system 1, since the pulse signal PLS is used, it is not necessary to increase the component size, and the cost does not increase. Therefore, in the power conversion system 1, the power regeneration circuit 30 can be effectively protected.

[0075] Thus, in the power conversion system 1, the threshold voltages VthH and VthL are set to voltages higher than the voltage corresponding to the drain voltage VP of the transistor Q3 and the voltage corresponding to the drain voltage VM of the transistor Q4 when the voltage VH is within the normal operating voltage range. Also, in the power conversion system 1, the logical product of the signal CMP and the pulse signal PLS is calculated, and the control signals G5 and G6 are generated based on the output signal of this logical product circuit 45. Thereby, in the power conversion system 1, when the voltage VH suddenly changes to a voltage higher than the normal operating voltage range (for example, 300 to 400 V), the power regeneration circuit 30 can be protected.

[0076] FIG. 8 shows an example of the simulation results of the power conversion system 1 when the voltage VH is suddenly changed. (A) shows the waveform of the voltage VH across the capacitor 11, (B) shows the waveform of the regeneration current IL of the inductor 35 in the power regeneration circuit 30, (C) shows the waveform of the drain-source voltage VdsQ5 of the transistor Q5, and (D) shows the waveform of the drain-source voltage VdsQ6 of the transistor Q6. FIG. 9 shows an example of the simulation results of the power conversion system according to the reference example. In the power conversion system according to the reference example, the above two techniques are not introduced.

[0077] In this example, the voltage VH is gradually changed from 200 V to 600 V at a time of 0.4 msec. Also, in this example, even when the maximum voltage Vovp (400 V) is exceeded, the operation of the power conversion device 10 is not stopped.

[0078] When the voltage VH rises, the voltage generated across the winding 16B of the transformer 16 increases, and more power is regenerated. Therefore, as shown in FIG. 8, when the voltage VH rises, the regeneration current IL increases, and the drain-source voltage VdsQ5 of the transistor Q5 and the drain-source voltage VdsQ6 of the transistor Q6 increase.

[0079] In the power conversion system according to the reference example (Fig. 9), the regenerative current IL starts to increase at the timing when the voltage VH reaches about 250V. On the other hand, in the power conversion system 1 according to the present embodiment (Fig. 8), the regenerative current IL starts to increase at the timing when the voltage VH reaches about 500V. In the power conversion system 1, the threshold voltages VthH and VthL are set to voltages higher than the voltages corresponding to the voltage VP at the drain of the transistor Q3 and the voltage VM at the drain of the transistor Q4 when the voltage VH is within the normal operating voltage range. Thereby, in the power conversion system 1, when the voltage VH changes suddenly, the timing at which the regenerative current IL starts to increase can be delayed.

[0080] Also, in the power conversion system according to the reference example (Fig. 9), the regenerative current IL is about 60A when the voltage VH is 600V. On the other hand, in the power conversion system 1 according to the present embodiment (Fig. 8), the regenerative current IL is about 20A when the voltage VH is 600V. In the power conversion system 1, the logical product of the signal CMP and the pulse signal PLS is calculated, and the control signals G5 and G6 are generated based on the output signal of this logical product circuit 45. Thereby, in the power conversion system 1, power is regenerated intermittently according to the pulse signal PLS, so that the regenerative current IL can be suppressed.

[0081] In the power conversion system 1, since the regenerative power is suppressed when the voltage VH changes suddenly in this way, the drain-source voltage VdsQ5 of the transistor Q5 and the drain-source voltage VdsQ6 of the transistor Q6 can also be reduced. In this way, in the power conversion system 1, the power regeneration circuit 30 can be protected when the voltage VH changes suddenly.

[0082] (Regarding coil buzzing) When the inductor operates in the audible frequency range of humans, noise due to so-called coil buzzing may occur. The inductor 35 of the power regeneration circuit 30 can operate in the audible frequency region.

[0083] FIG. 10 shows an example operation of the power regeneration circuit 30. (A) shows the waveform of the drain-source voltage VdsQ3 of the transistor Q3 in the rectifier circuit 17, (B) shows the waveform of the voltage VSNB of the capacitor 33 in the power regeneration circuit 30, and (C) shows the waveform of the regeneration current IL flowing through the inductor 35.

[0084] As shown in FIG. 10(A), every time a surge voltage is generated due to the switching operation of the transistor Q3, the diode 31 becomes transiently on, and the capacitor 33 is charged. As a result, the voltage VSNB of the capacitor 33 increases stepwise. Then, when the voltage VSNB reaches the threshold voltage VthH, the transistor Q5 turns on and the transistor Q6 turns off, the capacitor 33 is discharged, and the regeneration current IL flows. Then, when the voltage VSNB reaches the threshold voltage VthL, the transistor Q5 turns off and the transistor Q6 turns on. The power regeneration circuit 30 repeats such an operation. In this example, the switching frequency is 150 kHz. Therefore, the frequency of the regeneration current IL is about 16.6 kHz. This frequency is within the audible frequency range of humans.

[0085] In the power conversion system 1, for example, an inductor 35 of a metal integral molding type is used. Thereby, in the power conversion system 1, noise due to coil buzzing can be suppressed. That is, for example, when an inductor of a type in which a winding wound around a bobbin is fitted into a ferrite core is used, noise due to coil buzzing may be generated due to mechanical vibration. On the other hand, in the power conversion system 1, an inductor 35 of a metal integral molding type is used. In this metal integral molding type inductor, since the winding and the ferrite core are integrally formed, mechanical vibration is less likely to occur. Therefore, in the power conversion system 1, noise due to coil buzzing can be suppressed.

[0086] As described above, in the power conversion system 1, a first power terminal (terminals T11, T12), a switching circuit 14 connected to the first power terminal (terminals T11, T12), a first winding (winding 16A) led to the switching circuit 14, a transformer 16 having a second winding (winding 16B), a rectifier circuit 17 connected to the second winding (winding 16B) and having one or more rectifying switching elements, a first inductor (inductor 19) having one end and the other end, and a smoothing circuit 18 including a first capacitor (capacitor 20) having the other end connected to the other end of the first inductor (inductor 19) and a reference node (reference voltage line L22); a power regeneration circuit 30 connected to the rectifier circuit 17 and capable of regenerating the energy of the surge voltage generated in the rectifier circuit into the first capacitor (capacitor 20); a control circuit 40 capable of controlling the operations of the switching circuit 14, the rectifier circuit 17, and the power regeneration circuit 30; and a second power terminal (terminals T21, T22) having a first connection terminal (terminal T21) connected to the other end of the first inductor (inductor 19) and one end of the first capacitor and a second connection terminal (terminal T22) connected to the reference node (reference voltage line L22) are provided. The power regeneration circuit 30 has one end connected to the rectifier circuit 17 and the other end connected to a first node (node N1), and includes a diode circuit (diodes 31, 32) capable of flowing a current from the one end to the other end, a second capacitor (capacitor 33) having one end connected to the first node (node N1) and the other end connected to the reference node, a first regeneration switching element (transistor Q5) having one end connected to the first node (node N1) and the other end connected to a second node (node N2), a second regeneration switching element (transistor Q6) having one end connected to the second node (node N2) and the other end connected to the reference node (reference voltage line L22), and a second inductor (inductor 35) and a first diode (diode 36) provided in a path connecting the second node (node N2) and one end of the first capacitor (capacitor 20).When the voltage of the first node (node N1) rises and exceeds the threshold voltage VthH, the control circuit 40 can turn on the first regenerative switching element (transistor Q5) from the off state and turn off the second regenerative switching element (transistor Q6) from the on state. When the input voltage input to the first power terminals (terminals T11, T12) is a voltage within the normal operating voltage range, a first positive voltage (voltage VP) and a first negative voltage (voltage VM) alternately occur across both ends of the second winding, and the threshold voltage VthH is set to be higher than the voltage corresponding to the average value of the first positive voltage (voltage VP) and the voltage corresponding to the average value of the first negative voltage (voltage VM) in the rectifier circuit 17. Thereby, in the power conversion system 1, as shown in FIG. 8, the timing at which the regenerative current IL starts to increase when the voltage VH is rapidly changed can be delayed. As a result, in the power conversion system 1, the power regeneration circuit 30 can be protected.

[0087] Also, in the power conversion system 1, the second winding (winding 16B) is configured to have one end connected to one end of the first inductor (inductor 19) and the other end. One or more rectifying switching elements include a first rectifying switching element (transistor Q3) having one end connected to one end of the second winding (winding 16B) and the other end connected to a reference node (reference voltage line L22), and a second rectifying switching element having one end connected to one end of the second winding (winding 16B) and the other end connected to a reference node (reference voltage line L22). (transistor Q4). The diode circuit includes a second diode (diode 31) having an anode connected to one end of the first rectifying switching element (transistor Q3) and a cathode connected to the first node (node N1), and a second rectifying switching element (transistor Q4). ) and a third diode (diode 32) having an anode connected to one end and a cathode connected to the first node (node N1). Thereby, in the power conversion system 1, the power regeneration circuit 30 can regenerate the energy of the surge voltage generated in the transistors Q3 and Q4. And in the power conversion system 1, the timing at which the regenerative current IL starts to increase when the voltage VH is rapidly changed can be delayed. As a result, in the power conversion system 1, the power regeneration circuit 30 can be effectively protected.

[0088] Also, in the power conversion system 1, the control circuit 40 can generate a comparison result signal (signal CMP) by comparing the voltage of the first node (node N1) with a threshold voltage VthH, can generate a pulse signal PLS, can calculate the logical product of the comparison result signal (signal CMP) and the pulse signal PLS, and can control the operations of the first regenerative switching element (transistor Q5) and the second regenerative switching element (transistor Q6) based on the signal indicating the logical product. Also, the length of the period during which the first regenerative switching element (transistor Q5) is in the on state is made shorter than the pulse width of the pulse signal PLS. The pulse signal PLS is made synchronous with the switching operation in the switching circuit. For example, the pulse width of the pulse signal PLS can be made shorter than the maximum pulse width of the control signal G2 supplied to the transistor Q2. Thereby, in the power conversion system 1, as shown in FIGS. 5 to 7, the length of the period during which the transistor Q5 is in the on state can be limited using the pulse signal PLS. In particular, in the power conversion system 1, as shown in FIG. 8, when the voltage VH is rapidly changed, an increase in the regenerative current IL can be suppressed. As a result, in the power conversion system 1, the power regeneration circuit 30 can be protected.

[0089] Also, in the power conversion system 1, the threshold voltage is configured to include a first threshold voltage (threshold voltage VthH) and a second threshold voltage (threshold voltage VthL) lower than the first threshold voltage. When the control circuit 40 compares the voltage of the first node (node N1) with the threshold voltage, when the voltage of the first node (node N1) rises and the voltage of the first node exceeds the first threshold voltage (threshold voltage VthH), the first regenerative switching element (transistor Q5) can be changed from the off state to the on state and the second regenerative switching element (transistor Q6) can be changed from the on state to the off state. When the voltage of the first node (node N1) drops and the voltage of the first node falls below the second threshold voltage (threshold voltage VthL), the first regenerative switching element (transistor Q5) can be changed from the on state to the off state and the second regenerative switching element (transistor Q6) can be changed from the off state to the on state. Thereby, the control circuit 40 can control the operations of the transistors Q5 and Q6 to regenerate power based on the voltage VSNB.

[0090] Also, in the power conversion system 1, the second inductor is of the metal integrated molding type. Thereby, in the power conversion system 1, noise caused by coil buzzing can be suppressed.

[0091] [Effect] As described above, in the present embodiment, there are provided a first power terminal, a switching circuit connected to the first power terminal, a first winding led to the switching circuit, a transformer having a second winding, a rectifier circuit 17 connected to the second winding and having one or more rectifying switching elements, a first inductor having one end and the other end, a smoothing circuit including a first capacitor having one end connected to the other end of the first inductor and the other end connected to a reference node, a power regeneration circuit connected to the rectifier circuit and capable of regenerating the energy of the surge voltage generated in the rectifier circuit to the first capacitor, a control circuit capable of controlling the operations of the switching circuit, the rectifier circuit, and the power regeneration circuit, a second power terminal having a first connection terminal connected to the other end of the first inductor and one end of the first capacitor and a second connection terminal connected to the reference node. The power regeneration circuit has one end connected to the rectifier circuit and the other end connected to a first node, a diode circuit capable of flowing a current from the one end toward the other end, a second capacitor having one end connected to the first node and the other end connected to the reference node, a first regeneration switching element having one end connected to the first node and the other end connected to a second node, a second regeneration switching element having one end connected to the second node and the other end connected to the reference node, and a second inductor and a first diode provided in a path connecting the second node and one end of the first capacitor. The control circuit is capable of turning on the first regeneration switching element from an off state and turning off the second regeneration switching element from an on state when the voltage of the first node rises and the voltage of the first node exceeds a threshold voltage. When the input voltage input to the first power terminal is a voltage within the normal operating voltage range, a first positive voltage and a first negative voltage alternately occur between both ends of the second winding, and the threshold voltage is set to be higher than the voltage corresponding to the average value of the first positive voltage and the voltage corresponding to the average value of the first negative voltage in the rectifier circuit. Thereby, the power regeneration circuit can be protected.

[0092] In this embodiment, the second winding is configured to have one end connected to one end of the first inductor and the other end. One or more rectifying switching elements include a first rectifying switching element having one end connected to the other end of the second winding and the other end connected to the reference node, and a second rectifying switching element having one end connected to one end of the second winding and the other end connected to the reference node. The diode circuit is configured to have a second diode having an anode connected to one end of the first rectifying switching element and a cathode connected to the first node, and a third diode having an anode connected to one end of the second rectifying switching element and a cathode connected to the first node. Thereby, in the power conversion system 1, the power regeneration circuit can be effectively protected.

[0093] In this embodiment, the control circuit is capable of generating a comparison result signal by comparing the voltage of the first node with a threshold voltage, capable of generating a pulse signal, capable of calculating the logical product of the comparison result signal and the pulse signal, and capable of controlling the operations of the first regeneration switching element and the second regeneration switching element based on the signal indicating the logical product. Also, the length of the period during which the first regeneration switching element is in the on state is made shorter than the pulse width of the pulse signal. The pulse signal is made synchronous with the switching operation in the switching circuit. Thereby, the power regeneration circuit can be protected.

[0094] [Modification Example] In the above embodiment, the present technology is applied to the power conversion system 1 having the circuit configuration shown in FIG. 1, but it is not limited thereto. The present technology can be applied to power conversion systems having various circuit configurations.

[0095] Figure 11 shows a configuration example of the power conversion system 2 according to this modified example. The power conversion system 2 includes a power conversion device 50. The power conversion device 50 has terminals T11, T12, a capacitor 11, a voltage sensor 12, a switching circuit 54, an inductor 55, a transformer 56, a rectifier circuit 57, a smoothing circuit 18, a power regeneration circuit 30, a voltage sensor 21, a control circuit 60, and terminals T21, T22. The high-voltage battery BH, the capacitor 11, the voltage sensor 12, the switching circuit 54, and the inductor 55 constitute the primary-side circuit of the power conversion system 2, and the rectifier circuit 57, the smoothing circuit 18, the power regeneration circuit 30, the voltage sensor 21, and the low-voltage battery BL constitute the secondary-side circuit of the power conversion system 2.

[0096] The switching circuit 54 has transistors Q11 to Q14. The drain of transistor Q11 is connected to the voltage line L11, the source is connected to the node N21, and the control signal G11 is supplied to the gate. The drain of transistor Q12 is connected to the node N21, the source is connected to the reference voltage line L12, and the control signal G12 is supplied to the gate. The drain of transistor Q13 is connected to the voltage line L11, the source is connected to the node N22, and the control signal G13 is supplied to the gate. The drain of transistor Q14 is connected to the node N22, the source is connected to the reference voltage line L12, and the control signal G14 is supplied to the gate.

[0097] One end of the inductor 55 is connected to the node N21, and the other end is connected to a winding 56A (described later) in the transformer 56.

[0098] The transformer 56 has windings 56A, 56B, and 56C. The winding 56A is the primary winding of the transformer 56, one end is connected to the other end of the inductor 55, and the other end is connected to the node N22. The windings 56B and 56C are the secondary windings of the transformer 56. One end of the winding 56B is connected to the node N23, and the other end is connected to the voltage line L21A. One end of the winding 56C is connected to the voltage line L21A, and the other end is connected to the node N24.

[0099] The rectifier circuit 57 has transistors Q15, Q16 and snubber circuits SN15, SN16. The drain of transistor Q15 is connected to node N24, the source is connected to the reference voltage line L22, and the control signal G15 is supplied to the gate. The drain of transistor Q16 is connected to node N23, the source is connected to the reference voltage line L22, and the control signal G16 is supplied to the gate. One end of the snubber circuit SN15 is connected to the drain of transistor Q15, and the other end is connected to the source of transistor Q15. One end of the snubber circuit SN16 is connected to the drain of transistor Q16, and the other end is connected to the source of transistor Q16.

[0100] Figure 12 shows a configuration example of the power regeneration circuit 30. The anode of diode 31 is connected to node N24, and the anode of diode 32 is connected to node N23.

[0101] The control circuit 60 (Fig. 11) is configured to control the operation of the power conversion device 50 based on the voltage VH detected by the voltage sensor 12, the voltage VL detected by the voltage sensor 21, and the voltage VSNB detected by the voltage sensor 34 of the power regeneration circuit 30.

[0102] Figure 13 shows an operation example of the power conversion system 2 when the voltage VH is the upper limit voltage (e.g., 300V) of the normal operation voltage range. (A) to (F) respectively show the waveforms of the control signals G11 to G16, (G) shows the waveform of the drain-source voltage VdsQ15 of transistor Q15, (H) shows the waveform of the drain-source voltage VdsQ16 of transistor Q16, (I) shows the waveform of the voltage VSNB across the capacitor 33 of the power regeneration circuit 30, (J) shows the waveform of the signal CMP, (K) shows the waveform of the pulse signal PLS, (L) and (M) respectively show the waveforms of the control signals G5 and G6, and (N) shows the waveform of the regeneration current IL flowing through the inductor 35 of the power regeneration circuit 30. This Figure 13 corresponds to Figure 6 in the above embodiment.

[0103] The control circuit 60 generates control signals G11 to G16 based on the voltage VL (Figs. 13(A) to (F)). The power conversion device 50 performs a switching operation based on such control signals G11 to G16, thereby converting the power supplied from the high-voltage battery BH and performing a power conversion operation of supplying the converted power to the low-voltage battery BL. Then, the power conversion device 50 controls the duty ratios of the control signals G11 to G16 so that the voltage VL maintains a predetermined voltage.

[0104] The power regeneration circuit 30 operates to regenerate the energy of the surge voltage generated in the transistors Q15 and Q16. The energy of the surge voltage generated in the transistor Q15 is supplied to the capacitor 33 of the power regeneration circuit 30 via the diode 31 and is temporarily stored in this capacitor 33. The energy of the surge voltage generated in the transistor Q16 is supplied to the capacitor 33 of the power regeneration circuit 30 via the diode 32 and is temporarily stored in this capacitor 33. The control circuit 60 generates control signals G15 and G16 based on the voltage VSNB of the capacitor 33. Thereby, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the transistors Q15 and Q16.

[0105] For example, in this example, at timing t61, when the control circuit 60 changes the control signal G16 from a high level to a low level (Fig. 13(F)), in transistor Q16, current flows through the body diode. Thereafter, due to the reverse recovery operation of the body diode, the body diode of transistor Q16 changes from the on state to the off state. As a result, the drain-source voltage VdsQ16 of this transistor Q16 rises from 0V (Fig. 13(H)). The drain-source voltage VdsQ16 transiently exceeds the voltage VSNB of capacitor 33 at timing t62. During the period when the drain-source voltage VdsQ16 exceeds the voltage VSNB, diode 32 turns on, and current flows into capacitor 33 through this diode 32. In this way, capacitor 33 is transiently charged, and the voltage VSNB of capacitor 33 rises (Fig. 13(I)). The voltage VSNB after the rise is lower than the threshold voltage VthH in this example. Thereafter, during the period from when the control signal G14 changes from a high level to a low level until the control signal G16 changes from a low level to a high level, the drain-source voltage VdsQ16 of this transistor Q16 becomes 0V (Fig. 13(H)). Thereafter, at timing t63, when the control circuit 60 changes the control signal G16 from a low level to a high level (Fig. 13(F)), transistor Q16 changes from the off state to the on state.

[0106] Similarly, when the control circuit 60 changes the control signal G15 from a high level to a low level at timing t64 (Fig. 13(E)), in transistor Q15, current flows through the body diode. Then, due to the reverse recovery operation of the body diode, the body diode of transistor Q15 changes from the on state to the off state. As a result, the drain-source voltage VdsQ15 of this transistor Q15 rises from 0V (Fig. 13(G)). The drain-source voltage VdsQ15 becomes transiently higher than the voltage VSNB of capacitor 33 at timing t65, and diode 31 turns on. Thereby, capacitor 33 is transiently charged, and the voltage VSNB of capacitor 33 rises (Fig. 13(I)). In this example, at timing t66, this voltage VSNB exceeds the threshold voltage VthH. The control circuit 60 generates control signals G5 and G6 based on this voltage VSNB.

[0107] At timing t66 when the voltage VSNB exceeds the threshold voltage VthH, comparator 43 changes the signal CMP from a low level to a high level (Fig. 13(J)). AND circuit 45 calculates the logical product of signal CMP and pulse signal PLS (Fig. 13(J), (K)). Control signal generation circuit 46 generates control signals G5 and G6 based on the output signal of this AND circuit 45 (Fig. 13(L), (M)).

[0108] At timing t67, the control signal generation circuit 46 changes the control signal G6 from a high level to a low level (Fig. 13(M)). As a result, the transistor Q6 changes from the on state to the off state. Then, at timing t68 when a dead time Td has elapsed from this timing t67, the control signal generation circuit 46 changes the control signal G5 from a low level to a high level (Fig. 13(L)). As a result, the transistor Q5 changes from the off state to the on state, and a regenerative current IL flows from the capacitor 33 through the transistor Q5, the inductor 35, and the diode 36 toward the capacitor 20 (Fig. 13(N)). That is, the energy of the surge voltage generated in the transistors Q15 and Q16 is once stored in the capacitor 33 of the power regeneration circuit 30 and then regenerated to the capacitor 20. During the period from timing t68 to t69, the regenerative current IL increases. Since the capacitor 33 is discharged, the voltage VSNB of the capacitor 33 decreases toward the threshold voltage VthL (Fig. 13(I)).

[0109] At timing t69, when the voltage VSNB reaches the threshold voltage VthL, the comparator 43 changes the signal CMP from a high level to a low level (Fig. 13(J)). As a result, the control signal generation circuit 46 changes the control signal G5 from a high level to a low level (Fig. 13(L)). As a result, the transistor Q5 changes from the on state to the off state. Since the discharge of the capacitor 33 stops, the voltage VSNB maintains the same voltage as the threshold voltage VthL (Fig. 13(I)). Then, at timing t70 when a dead time Td has elapsed from this timing t69, the control signal generation circuit 46 changes the control signal G6 from a low level to a high level (Fig. 13(M)). As a result, the transistor Q6 changes from the off state to the on state. During the period from timing t69 to t71, the regenerative current IL decreases (Fig. 13(N)).

[0110] In this way, the power regeneration circuit 30 regenerates the energy of the surge voltage generated in the transistors Q15 and Q16.

[0111] Next, the operation of the power conversion system 2 when the voltage VH is higher than the normal operating voltage range will be described.

[0112] FIG. 14 shows an operation example of the power conversion system 1 when the voltage VH is higher than the normal operating voltage range and lower than the maximum voltage Vovp. (A) shows the waveform of the voltage VH, (B) to (G) show the waveforms of the control signals G11 to G16 respectively, (H) shows the waveform of the drain-source voltage VdsQ15 of the transistor Q15, (I) shows the waveform of the drain-source voltage VdsQ16 of the transistor Q16, (J) shows the waveform of the voltage VSNB across the capacitor 33 of the power regeneration circuit 30, (K) shows the waveform of the signal CMP, (L) shows the waveform of the pulse signal PLS, (M) and (N) show the waveforms of the control signals G5 and G6 respectively, and (O) shows the waveform of the regeneration current IL flowing through the inductor 35 of the power regeneration circuit 30. This FIG. 14 corresponds to FIG. 7 in the above embodiment.

[0113] As shown in FIG. 14(A), in this example, the voltage VH is rising toward the maximum voltage Vovp. The control circuit 60 generates the control signals G11 to G16 based on the voltage VL (FIGS. 14(B) to (G)).

[0114] In this example, since the voltage VH is gradually increasing, the voltage across both ends of winding 16B of transformer 16 also gradually increases. Therefore, the drain-source voltage VdsQ15 of transistor Q15 gradually increases during the period when transistor Q4 is in the off state, and the drain-source voltage VdsQ16 of transistor Q16 gradually increases during the period when transistor Q4 is in the off state (Figs. 14(F), (G)). Then, the drain-source voltage VdsQ15 and the drain-source voltage VdsQ16 exceed the voltage VSNB of capacitor 33. When the drain-source voltage VdsQ15 exceeds the voltage VSNB, diode 31 turns on, and when the drain-source voltage VdsQ16 exceeds the voltage VSNB, diode 32 turns on. As a result, capacitor 33 is charged and the voltage VSNB increases (Fig. 14(J)). In this example, except for the first period in Fig. 14, since the voltage VSNB is higher than the threshold voltage VthL, comparator 43 maintains signal CMP at a high level (Fig. 14(K)). AND circuit 45 calculates the logical product of this signal CMP and pulse signal PLS (Figs. 14(K), (L)). Since signal CMP is maintained at a high level, the output signal of AND circuit 45 has the same waveform as pulse signal PLS. Control signal generation circuit 46 generates control signals G5, G6 based on the output signal of this AND circuit 45 (Figs. 14(M), (N)). For example, control signal generation circuit 46 changes control signal G6 from a high level to a low level at timing t81, and changes control signal G5 from a low level to a high level at timing t82 after a dead time Td has elapsed from timing t81. Then, control signal generation circuit 46 changes control signal G5 from a high level to a low level at timing t83, and changes control signal G6 from a low level to a high level at timing t84 after a dead time Td has elapsed from timing t83. Transistors Q5, Q6 operate according to these control signals G5, G6. During the period when control signal G5 is at a high level, the regeneration current IL increases and then the regeneration current IL decreases (Fig. 14(M)).

[0115] The present invention has been described with reference to the embodiments and modifications. However, the present invention is not limited to these embodiments, and various modifications are possible.

[0116] For example, in the above embodiment, the power conversion system 1 is configured to perform a step-down operation in the power conversion operation. However, the present invention is not limited to this, and a step-up operation may be performed.

[0117] The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

[0118] Furthermore, the present disclosure may take the following aspects.

[0119] (1) A first power terminal, A switching circuit connected to the first power terminal, A transformer having a first winding and a second winding led to the switching circuit, A rectifier circuit connected to the second winding and having one or more rectifier switching elements, A smoothing circuit including a first inductor having one end and the other end, and a first capacitor having one end connected to the other end of the first inductor and the other end connected to a reference node, A power regeneration circuit connected to the rectifier circuit and capable of regenerating the energy of the surge voltage generated in the rectifier circuit to the first capacitor, A control circuit capable of controlling the operations of the switching circuit, the rectifier circuit, and the power regeneration circuit, A second power terminal having a first connection terminal connected to the other end of the first inductor and one end of the first capacitor and a second connection terminal connected to the reference node, Comprising, The power regeneration circuit is, A diode circuit provided in a path connecting the rectifier circuit and a first node and capable of flowing a current toward the first node, A second capacitor having one end connected to the first node and the other end connected to the reference node, A first regenerative switching element having one end connected to the first node and the other end connected to the second node, A second regenerative switching element having one end connected to the second node and the other end connected to the reference node, A second inductor and a first diode provided in a path connecting the second node and the one end of the first capacitor, and having, The control circuit can turn on the first regenerative switching element from the off state and turn off the second regenerative switching element when the voltage of the first node rises and the voltage of the first node exceeds the threshold voltage, When the input voltage input to the first power terminal is a voltage within the normal operating voltage range, a first positive voltage and a first negative voltage alternately occur between both ends of the second winding, The threshold voltage is higher than the voltage corresponding to the average value of the first positive voltage and the voltage corresponding to the average value of the first negative voltage in the rectifier circuit, A power conversion device. (2) The second winding has one end connected to the one end of the first inductor and the other end, The one or more rectifier switching elements include a first rectifier switching element having one end connected to the other end of the second winding and the other end connected to the reference node, and a second rectifier switching element having one end connected to the one end of the second winding and the other end connected to the reference node, The diode circuit, A second diode having an anode connected to the one end of the first rectifier switching element and a cathode connected to the first node, A third diode having an anode connected to the one end of the second rectifier switching element and a cathode connected to the first node having the power conversion device according to (1) above. (3) The transformer further has a third winding, The second winding has one end connected to the one end of the first inductor and the other end, The third winding has one end and the other end connected to the one end of the first inductor, The one or more rectifying switching elements include a first rectifying switching element having one end connected to the other end of the second winding and the other end connected to the reference node, and a second rectifying switching element having one end connected to the one end of the third winding and the other end connected to the reference node, The diode circuit a second diode having an anode connected to the one end of the first rectifying switching element and a cathode connected to the first node, a third diode having an anode connected to the one end of the second rectifying switching element and a cathode connected to the first node having the power conversion device according to (1) above. (4) The control circuit can generate a comparison result signal by comparing the voltage of the first node with the threshold voltage, can generate a pulse signal, can calculate the logical product of the comparison result signal and the pulse signal, and can control the operations of the first regenerative switching element and the second regenerative switching element based on the signal indicating the logical product the power conversion device according to (2) or (3) above. (5) The length of the period during which the first regenerative switching element is in the on state is shorter than the pulse width of the pulse signal the power conversion device according to (4) above. (6) The pulse signal can be synchronized with the switching operation in the switching circuit The power conversion device according to the above (4) or (5). (7) The threshold voltage includes a first threshold voltage and a second threshold voltage lower than the first threshold voltage, When the control circuit compares the voltage of the first node with the threshold voltage, when the voltage of the first node rises and the voltage of the first node exceeds the first threshold voltage, the first regenerative switching element can be changed from the off state to the on state and the second regenerative switching element can be changed from the on state to the off state, when the voltage of the first node drops and the voltage of the first node falls below the second threshold voltage, the first regenerative switching element can be changed from the on state to the off state and the second regenerative switching element can be changed from the off state to the on state The power conversion device according to any one of the above (1) to (6). (8) When the input voltage exceeds a predetermined voltage higher than the operating voltage range, the control circuit can stop the operations of the switching circuit, the rectifying circuit, and the power regeneration circuit, When the input voltage is the predetermined voltage, a second positive voltage and a second negative voltage are alternately generated between both ends of the second winding, The threshold voltage is lower than the larger voltage of the voltage corresponding to the average value of the second positive voltage and the voltage corresponding to the average value of the second negative voltage in the rectifying circuit The power conversion device according to any one of the above (1) to (7). (9) The second inductor is an inductor of a metal integral molding type The power conversion device according to any one of the above (1) to (8). (10) Equipped with the power conversion device according to the above (1) Power conversion system.

Explanation of symbols

[0120] 1, 2... power conversion system, 10, 50... power conversion device, 11... capacitor, 12... voltage sensor, 13... capacitor, 14, 54... switching circuit, 15, 55... inductor, 16, 56... transformer, 16A, 16B, 56A, 56B, 56C... winding, 17, 57... rectifier circuit, 18... smoothing circuit, 19... inductor, 20... capacitor, 21... voltage sensor, 30... power regeneration circuit, 31, 32... diode, 33... capacitor, 34... voltage sensor, 35... inductor, 36... diode, 40, 60... control circuit, 41... voltage dividing circuit, 42... threshold voltage generation circuit, 43... comparator, 44... pulse signal generation circuit, 45... logical product circuit, 46... control signal generation circuit, BH... high voltage battery, BL... low voltage battery, CMP... signal, G1~G6, G11~G16, L11, L21A, L21B... voltage line, L12, L22... reference voltage line, PLS... pulse signal, Q1~Q6, Q11~Q16... transistor, SN3, SN4, SN15, SN16... snubber circuit, T11, T12, T21, T22... terminal, VH... voltage, VL... voltage, VM, VP, VSNB... voltage, Vovp... maximum voltage, Vth, VthH, VthL... threshold voltage.

Claims

1. a first power terminal; a switching circuit connected to the first power terminal; a transformer having a first winding and a second winding led to the switching circuit; a rectifier circuit connected to the second winding and having one or more rectifying switching elements; a smoothing circuit including a first inductor having one end and the other end, and a first capacitor having one end connected to the other end of the first inductor and the other end connected to a reference node; a power regeneration circuit connected to the rectifier circuit and capable of regenerating the energy of a surge voltage generated in the rectifier circuit to the first capacitor; a control circuit capable of controlling the operations of the switching circuit, the rectifier circuit, and the power regeneration circuit; a second power terminal having a first connection terminal connected to the other end of the first inductor and one end of the first capacitor and a second connection terminal connected to the reference node and comprising; the power regeneration circuit includes a diode circuit provided in a path connecting the rectifier circuit and a first node and capable of flowing a current toward the first node; a second capacitor having one end connected to the first node and the other end connected to the reference node; a first regeneration switching element having one end connected to the first node and the other end connected to a second node; a second regeneration switching element having one end connected to the second node and the other end connected to the reference node; a second inductor and a first diode provided in a path connecting the second node and one end of the first capacitor and having; when the voltage of the first node rises and the voltage of the first node exceeds a threshold voltage, the control circuit can turn on the first regeneration switching element from an off state and turn off the second regeneration switching element from an on state; when the input voltage input to the first power terminal is a voltage within a normal operating voltage range, a first positive voltage and a first negative voltage alternately occur between both ends of the second winding; the threshold voltage is higher than a voltage corresponding to an average value of the first positive voltage and a voltage corresponding to an average value of the first negative voltage in the rectifier circuit a power conversion device.

2. the second winding has one end connected to the one end of the first inductor and the other end; The one or more rectifying switching elements include a first rectifying switching element having one end connected to the other end of the second winding and the other end connected to the reference node, and a second rectifying switching element having one end connected to the one end of the second winding and the other end connected to the reference node. The diode circuit includes a second diode having an anode connected to the one end of the first rectifying switching element and a cathode connected to the first node, and a third diode having an anode connected to the one end of the second rectifying switching element and a cathode connected to the first node. It has The power conversion device according to claim 1.

3. The transformer further has a third winding, The second winding has one end connected to the one end of the first inductor and the other end, The third winding has one end and the other end connected to the one end of the first inductor, The one or more rectifying switching elements include a first rectifying switching element having one end connected to the other end of the second winding and the other end connected to the reference node, and a second rectifying switching element having one end connected to the one end of the third winding and the other end connected to the reference node. The diode circuit includes a second diode having an anode connected to the one end of the first rectifying switching element and a cathode connected to the first node, and a third diode having an anode connected to the one end of the second rectifying switching element and a cathode connected to the first node. It has The power conversion device according to claim 1.

4. The control circuit can generate a comparison result signal by comparing the voltage of the first node with the threshold voltage, can generate a pulse signal, can calculate the logical product of the comparison result signal and the pulse signal, and can control the operations of the first regenerative switching element and the second regenerative switching element based on the signal indicating the logical product. The power conversion device according to claim 2.

5. The length of the period during which the first regenerative switching element is in the on state is shorter than the pulse width of the pulse signal. The power conversion device according to claim 4.

6. The pulse signal can be synchronized with the switching operation in the switching circuit. The power conversion device according to claim 4.

7. The threshold voltage includes a first threshold voltage and a second threshold voltage lower than the first threshold voltage, when the control circuit compares the voltage of the first node with the threshold voltage, when the voltage of the first node rises and the voltage of the first node exceeds the first threshold voltage, it is possible to turn on the first regenerative switching element from the off state and turn off the second regenerative switching element from the on state, when the voltage of the first node drops and the voltage of the first node falls below the second threshold voltage, it is possible to turn off the first regenerative switching element from the on state and turn on the second regenerative switching element from the off state The power conversion device according to claim 1.

8. when the input voltage exceeds a predetermined voltage higher than the operating voltage range, the control circuit can stop the operations of the switching circuit, the rectifying circuit, and the power regeneration circuit, when the input voltage is the predetermined voltage, a second positive voltage and a second negative voltage alternately occur between both ends of the second winding, the threshold voltage is lower than the larger voltage among the voltage corresponding to the average value of the second positive voltage and the voltage corresponding to the average value of the second negative voltage in the rectifying circuit The power conversion device according to claim 1.

9. The second inductor is an inductor of a metal integral molding type The power conversion device according to claim 1.

10. A power conversion system including the power conversion device according to claim 1.

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