Power conversion device and power conversion system

Abstract

To obtain a power conversion device capable of protecting a circuit in the event of a short circuit.SOLUTION: A power conversion device according to one embodiment of the present disclosure comprises a first power terminal having a first connection terminal and a second connection terminal, a switching circuit, a transformer, a rectifier circuit having one or a plurality of rectifier switching elements, a smoothing circuit including a first inductor and a first capacitor, a power regeneration circuit connected to the rectifier circuit, capable of regenerating power to the first capacitor, a control circuit capable of controlling the operation of the switching circuit, rectifier circuit, and power regeneration circuit, and a second power terminal. The control circuit is capable of detecting a short circuit between the first connection terminal and the second connection terminal at the first power terminal based on one or both of the voltage and current in the power regeneration circuit during a predetermined period before the period of supplying power from the first power terminal to the second power terminal.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Some power conversion devices prevent damage to circuits caused by large currents resulting from short circuits. For example, Patent Document 1 discloses a power conversion device that reduces load current when a load is short-circuited.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As described above, in a power conversion device, it is desired to protect the circuit when a short circuit occurs.

[0005] It is desirable to provide a power conversion device and a power conversion system that can protect the circuit when a short circuit occurs.

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 power 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 control circuit can detect a short circuit between the first connection terminal and the second connection terminal at the first power terminal based on one or both of the voltage and current in the power regeneration circuit during a predetermined period before a period of supplying power from the first power terminal to the second power terminal.

[0007] A power conversion system according to an embodiment of the present invention includes a first battery, a capacitor, a first switch, a second switch, a power conversion device, and a second battery. The first battery has a first terminal and a second terminal. The capacitor has a first terminal and a second terminal. The first switch is provided in a path connecting the first terminal of the first battery and the first terminal of the capacitor. The second switch is provided in a path connecting the second terminal of the first battery and the second terminal of the capacitor. The power conversion device 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 first power terminal is connected to a capacitor. The switching circuit is connected to the first power terminal. The transformer has a first winding led to the switching circuit and a second winding. The rectifying circuit is connected to the second winding and has one or more rectifying 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 rectifying circuit and can regenerate power to the first capacitor. The control circuit can control the operations of the switching circuit, the rectifying 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, and is connected to a second battery. The control circuit can detect a short circuit between the first connection terminal and the second connection terminal at the first power terminal based on one or both of the voltage and current in the power regeneration circuit during a predetermined period before the period of supplying power from the first power terminal to the second power terminal.

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 when a short circuit occurs.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6A

Figure 6B

Figure 6C

Figure 6D

Figure 6E

Figure 6F

Figure 6G

Figure 7

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Figure 9

Figure 10

Figure 11

Figure 12

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Figure 14

Figure 15

Figure 16

Figure 17

Figure 18

DETAILED DESCRIPTION OF THE INVENTION

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

[0011] <Embodiment> [Configuration Example] FIG. 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, switches SW1 and SW2, a capacitor 9, a power conversion device 10, and a low-voltage battery BL. The 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 via the switches SW1 and SW2.

[0013] Switches SW1 and SW2 are configured to supply the power stored in the high-voltage battery BH to the power conversion device 10 when turned on. Switches SW1 and SW2 are configured using, for example, relays. Switch SW1 connects the positive terminal of the high-voltage battery BH and the terminal T11 of the power conversion device 10 when turned on. Switch SW2 connects the negative terminal of the high-voltage battery BH and the terminal T12 of the power conversion device 10 when turned on. Switches SW1 and SW2 are turned on and off based on an instruction from a system control unit (not shown).

[0014] One end of the capacitor 9 is connected to the terminal T11 of the power conversion device 10 and switch SW1, and the other end is connected to the terminal T12 of the power conversion device 10 and switch SW2.

[0015] 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 voltage sensor 11, a capacitor 12, a resistance element 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 22, and terminals T21, T22. The high-voltage battery BH, switches SW1 and SW2, voltage sensor 11, capacitor 12, resistance element 13, switching circuit 14, and inductor 15 constitute the primary-side circuit of the power conversion system 1, and the rectifier circuit 17, smoothing circuit 18, power regeneration circuit 30, voltage sensor 21, and low-voltage battery BL constitute the secondary-side circuit of the power conversion system 1.

[0016] Terminals T11 and T12 are configured to be supplied with voltage from the high-voltage battery BH when switches SW1 and SW2 are turned on. Inside the power conversion device 10, terminal T11 is connected to the voltage line L11, and terminal T12 is connected to the reference voltage line L12.

[0017] One end of the voltage sensor 11 is connected to the voltage line L11, and the other end is connected to the reference voltage line L12. The voltage sensor 11 is configured to detect the voltage VH on the voltage line L11 with reference to the voltage on the reference voltage line L12.

[0018] One end of the capacitor 12 is connected to the voltage line L11, and the other end is connected to the node N11. One end of the resistive element 13 is connected to the voltage line L11, and the other end is connected to the node N11.

[0019] The switching circuit 14 is configured to perform a switching operation based on the control signals G1 and G2. The switching circuit 14 includes 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). The transistors Q1 and Q2 each have body diodes D1 and D2. For example, the anode of the body diode D1 is connected to the source of the body of the transistor Q1, and the cathode is connected to the drain of the body of the transistor Q1. The same applies to the body diode D2. In this example, N-type field effect transistors are used, but any switching element may be used. The drain of the transistor Q1 is connected to the node N11, the source is connected to the node N12, and the control signal G1 is supplied to the gate. The drain of the transistor Q2 is connected to the node N12, the source is connected to the reference voltage line L12, and the control signal G2 is supplied to the gate.

[0020] One end of the inductor 15 is connected to a winding 16A (described later) in the transformer 16, and the other end is connected to the node N12.

[0021] Transformer 16 is configured to insulate the primary side circuit and the secondary side circuit from each other in a DC manner and connect them in an AC manner, convert the AC voltage supplied from the primary side circuit at the transformation ratio of transformer 16, and supply the converted AC voltage to the secondary side circuit. Transformer 16 has windings 16A and 16B. Winding 16A is the primary winding of transformer 16, one end of which is connected to voltage line L11, and the other end is connected to one end of inductor 15. Winding 16B is the secondary winding of transformer 16, one end of which is connected to voltage line L21A (described later), and the other end is connected to node N13.

[0022] Rectifier circuit 17 is configured to rectify the AC voltage output from winding 16B of transformer 16. Rectifier circuit 17 has transistors Q3 and Q4. Transistors Q3 and Q4 are switching elements that perform switching operations based on control signals G3 and G4 respectively. Transistors Q3 and Q4 are configured using, for example, N-type field effect transistors, similar to transistors Q1 and Q2. Transistors Q3 and Q4 each have body diodes D3 and D4, similar to transistors Q1 and Q2. The drain of transistor Q3 is connected to node N13, the source is connected to reference voltage line L22, and control signal G3 is supplied to the gate. The drain of transistor Q4 is connected to voltage line L21A, the source is connected to reference voltage line L22, and control signal G4 is supplied to the gate.

[0023] Smoothing circuit 18 is configured to smooth the voltage rectified by rectifier circuit 17. Smoothing circuit 18 has inductor 19 and capacitor 20. One end of inductor 19 is connected to voltage line L21A, and the other end is connected to voltage line L21B. One end of capacitor 20 is connected to voltage line L21B, and the other end is connected to reference voltage line L22.

[0024] Power regeneration circuit 30 is configured to regenerate the power of the surge generated in transistors Q3 and Q4 of rectifier circuit 17 to capacitor 20.

[0025] 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, 32, a capacitor 33, a voltage sensor 34, transistors Q5, Q6, a current sensor 37, an inductor 35, and a diode 36.

[0026] 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 VCreg at node N1 with reference to the voltage on the reference voltage line L22.

[0027] Transistors Q5, Q6 are switching elements that perform switching operations based on control signals G5, G6 respectively. Transistors Q5, Q6 are configured using, for example, N-type field-effect transistors in the same manner as transistors Q1 - Q4. Transistors Q5, Q6 each have body diodes D5, D6 in the same manner as transistors Q1 - 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.

[0028] One end of current sensor 37 is connected to node N2 and the other end is connected to one end of inductor 35. The current sensor 37 is configured to detect the current ILreg flowing from node N2 towards capacitor 20. One end of inductor 35 is connected to the other end of current sensor 37 and the other end is connected to the anode of diode 36. 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 power of the surge 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 22 is configured to control the operation of the power conversion device 10 based on the voltage VH detected by the voltage sensor 11, the voltage VL detected by the voltage sensor 21, the voltage VCreg detected by the voltage sensor 34 of the power regeneration circuit 30, and the current ILreg detected by the current sensor 37 of the power regeneration circuit 30. The control circuit 22 is configured using, for example, a microcontroller or the like.

[0032] The terminals T21 and T22 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.

[0033] The low-voltage battery BL is configured to store the power supplied from the power conversion device 10.

[0034] With this configuration, the power conversion system 1 is configured to perform 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.

[0035] Also, this power conversion system 1 has a function of performing a so-called pre-charge operation of charging the capacitor 9 during a period before starting such a power conversion operation. In this pre-charge operation, the switches SW1 and SW2 are in the off state, and the control circuit 22 controls the operations of the switching circuit 14, the rectifier circuit 17, and the power regeneration circuit 30, so that the power conversion system 1 supplies the power of the low-voltage battery BL to the capacitor 9 via the transformer 16. Thereby, in the power conversion device 10, it is possible to suppress the inrush current flowing from the high-voltage battery BH to the capacitor 9 when the switches SW1 and SW2 are turned on to perform the power conversion operation.

[0036] Here, the terminals T11 and T12 correspond to a specific example of the "first power terminal" in an embodiment of the present disclosure. The switching circuit 14 corresponds to a specific example of the "switching circuit" in an embodiment of the present disclosure. The transformer 16 corresponds to a specific example of the "transformer" in an embodiment of the present disclosure. The winding 16A corresponds to a specific example of the "first winding" in an embodiment of the present disclosure. The winding 16B corresponds to a specific example of the "second winding" in an embodiment of the present disclosure. The rectifier circuit 17 corresponds to a specific example of the "rectifier circuit" in an embodiment of the present disclosure. The smoothing circuit 18 corresponds to a specific example of the "smoothing circuit" in an embodiment of the present disclosure. The inductor 19 corresponds to a specific example of the "first inductor" in an embodiment of the present disclosure. The capacitor 20 corresponds to a specific example of the "first capacitor" in an embodiment of the present disclosure. The reference node corresponds to a specific example of the "reference voltage line L22" in an embodiment of the present disclosure. The power regeneration circuit 30 corresponds to a specific example of the "power regeneration circuit" in an embodiment of the present disclosure. The terminals T21 and T22 correspond to a specific example of the "second power terminal" in an embodiment of the present disclosure. The control circuit 22 corresponds to a specific example of the "control circuit" in an embodiment of the present disclosure.

[0037] The diode 31 corresponds to a specific example of the "first diode" in one embodiment of the present disclosure. The capacitor 33 corresponds to a specific example of the "second capacitor" in one embodiment of the present disclosure. The transistor Q5 corresponds to a specific example of the "first regenerative switching element" in one embodiment of the present disclosure. The transistor Q6 corresponds to a specific example of the "second regenerative switching element" in one embodiment of the present disclosure. The inductor 35 corresponds to a specific example of the "second inductor" in one embodiment of the present disclosure. The diode 36 corresponds to a specific example of the "third diode" in one embodiment of the present disclosure. The node N1 corresponds to a specific example of the "first node" in one embodiment of the present disclosure. The node N2 corresponds to a specific example of the "second node" in one embodiment of the present disclosure. The transistor Q3 corresponds to a specific example of the "first rectifying switching element" in one embodiment of the present disclosure. The transistor Q4 corresponds to a specific example of the "second rectifying switching element" in one embodiment of the present disclosure.

[0038] [Operation and Function] Subsequently, the operation and function of the power conversion system 1 of the present embodiment will be described.

[0039] (Overall Operation Outline) First, with reference to FIG. 1, the overall operation outline of the power conversion system 1 will be described. When the power conversion system 1 starts, the switches SW1 and SW2 are in the off state. First, during the pre-charge period, the control circuit 22 generates control signals G1 to G6. The power conversion device 10 performs a switching operation based on the control signals G1 to G6, and charges the capacitor 9 by supplying the power of the low-voltage battery BL from the secondary side circuit to the primary side circuit via the transformer 16. As a result, the voltage VH rises and is maintained near the target voltage. Then, in the power conversion period after the pre-charge period, the switches SW1 and SW2 are turned on, and the control circuit 22 generates control signals G1 to G6. The power conversion device 10 performs a switching operation based on the control signals G1 to G6, converts the power supplied from the high-voltage battery BH, and supplies the converted power to the low-voltage battery BL.

[0040] (Detailed operation) The following describes in detail an operation example of the power conversion system 1. First, the power conversion operation will be described, and then the pre-charge operation will be described.

[0041] (Regarding the power conversion operation) FIG. 3 shows an operation example of the power conversion system 1 during the power conversion period. (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 VCreg across the capacitor 33 of the power regeneration circuit 30, (H) and (I) respectively show the waveforms of the control signals G5 and G6, and (J) shows the waveform of the current ILreg flowing through the inductor 35 of the power regeneration circuit 30. In FIGS. 3(A) to (D), (H), and (I), the control signals G1 to G6 are illustrated using the gate-source voltage Vgs of the transistors Q1 to Q6. Note that the waveform of the voltage VCreg is also illustrated in FIGS. 3(E) and (F). The waveform of this voltage VCreg is as shown in FIG. 3(G), but in FIGS. 3(E) and (F), it is drawn so as to hardly change due to the difference in voltage scale.

[0042] When performing a power conversion operation, the control circuit 22 generates control signals G1 to G4 based on the voltage VL (Figs. 3(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 22 changes the control signal G2 from high level to low level at timing t4, changes the control signal G1 from low level to high level at timing t7, changes the control signal G1 from high level to low level at timing t8, and changes the control signal G2 from low level to high level at timing t9 (Figs. 3(A), (B)). Similarly, the control circuit 22 changes the control signal G3 from high level to low level at timing t4, changes the control signal G4 from low level to high level at timing t7, changes the control signal G4 from high level to low level at timing t8, and changes the control signal G3 from low level to high level at timing t9 (Figs. 3(C), (D)). The control circuit 22 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 ratio of the control signals G1 to G4 so that the voltage VL maintains a predetermined voltage.

[0043] In this power conversion operation, the power regeneration circuit 30 operates to regenerate the power of the surge generated in the transistor Q3. The power of the surge 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 22 generates control signals G5 and G6 based on the voltage VCreg of the capacitor 33. Thereby, the power regeneration circuit 30 regenerates the power of the surge generated in the transistor Q3.

[0044] For example, in this example, at timing t1, when the control circuit 22 changes the control signal G3 from a high level to a low level (Fig. 3(C)), the transistor Q3 changes from an on state to an off state. As a result, the drain-source voltage VdsQ3 of this transistor Q3 rises from 0V (Fig. 3(E)). The drain-source voltage VdsQ3 transiently exceeds the voltage VCreg at timing t2. During the period when the drain-source voltage VdsQ3 exceeds the voltage VCreg, the diode 31 turns on, and current flows into the capacitor 33 through this diode 31. In this way, the capacitor 33 is transiently charged, and the voltage VCreg of the capacitor 33 rises (Fig. 3(G)). The voltage VCreg after the rise is lower than the threshold voltage VthH. Thereafter, at timing t3, when the control circuit 22 changes the control signal G3 from a low level to a high level (Fig. 3(C)), the transistor Q3 changes from an off state to an on state. As a result, the drain-source voltage VdsQ3 of this transistor Q3 becomes 0V (Fig. 3(E)).

[0045] Similarly, when the control circuit 22 changes the control signal G3 from a high level to a low level at timing t4 (Fig. 3(C)), the transistor Q3 changes from an on state to an off state. As a result, the drain-source voltage VdsQ3 of this transistor Q3 rises from 0V (Fig. 3(E)). The drain-source voltage VdsQ3 becomes transiently high at timing t5, and the diode 31 turns on. As a result, the capacitor 33 is transiently charged, and the voltage VCreg of the capacitor 33 rises (Fig. 3(G)). In this example, at timing t6, this voltage VCreg reaches the threshold voltage VthH. The control circuit 22 generates the control signals G5 and G6 based on this voltage VCreg.

[0046] Fig. 4 shows an example of the operation of the control circuit 22. The control circuit 22 generates the control signals G5 and G6 by comparing the voltage VCreg with the threshold voltages VthL and VthH. The threshold voltage VthH is higher than the threshold voltage VthL. When the control signal G5 is at a low level and the control signal G6 is at a high level, and the voltage VCreg rises and reaches the threshold voltage VthH, the control circuit 22 changes the control signal G6 from a high level to a low level, and at the timing when a dead time Td has elapsed from that timing, changes the control signal G5 from a low level to a high level. Also, when the control signal G5 is at a high level and the control signal G6 is at a low level, and the voltage VCreg drops and reaches the threshold voltage VthL, the control circuit 22 changes the control signal G5 from a high level to a low level, and at the timing when a dead time Td has elapsed from that timing, changes the control signal G6 from a low level to a high level. In this way, the control circuit 22 generates the control signals G5 and G6 using hysteresis characteristics based on the voltage VCreg.

[0047] As shown in FIG. 3, when the voltage VCreg reaches the threshold voltage VthH at timing t6, the control circuit 22 changes the control signal G6 from a high level to a low level at this timing t6 (FIG. 3(I)). As a result, the transistor Q6 changes from an on state to an off state. Then, at timing t8 when a dead time Td has elapsed from this timing t6, the control circuit 22 changes the control signal G5 from a low level to a high level. As a result, the transistor Q5 changes from an off state to an on state, and a current ILreg flows from the capacitor 33 through the transistor Q5, the inductor 35, and the diode 36 toward the capacitor 20 (FIG. 3(J)). That is, the power of the surge 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 t8 to t10, the current ILreg increases. Since the capacitor 33 is discharged, the voltage VCreg of the capacitor 33 decreases toward the threshold voltage VthL (FIG. 3(G)).

[0048] When the voltage VCreg reaches the threshold voltage VthL at timing t10, the control circuit 22 changes the control signal G5 from a high level to a low level at this timing t10 (FIG. 3(H)). As a result, the transistor Q5 changes from an on state to an off state. As a result, the discharge of the capacitor 33 stops, so the voltage VCreg maintains the same voltage as the threshold voltage VthL (FIG. 3(G)). Then, at timing t11 when a dead time Td has elapsed from this timing t10, the control circuit 22 changes the control signal G6 from a low level to a high level. As a result, the transistor Q6 changes from an off state to an on state. During the period from timing t10 to t12, the current ILreg decreases.

[0049] In this way, the power regeneration circuit 30 regenerates the power of the surge generated in the transistor Q3.

[0050] Note that in this example, an example in which a surge occurs in the transistor Q3 is described, but the same applies to the transistor Q4.

[0051] (Regarding the pre-charge operation) FIG. 5 shows an example of the operation of the power conversion system 1 during the pre-charge period. (A) to (D) respectively show the waveforms of the control signals G1 to G4, (E) shows the waveform of the current ILch flowing through the inductor 19 of the smoothing circuit 18, (F) shows the waveform of the charging current Ichg to the capacitor 9, (G) shows the waveform of the voltage VH, (H) shows the waveform of the voltage VCreg in the capacitor 33 of the power regeneration circuit 30, (I) and (J) respectively show the waveforms of the control signals G5 and G6, and (K) shows the waveform of the current ILreg flowing through the inductor 35 of the power regeneration circuit 30. FIGS. 6A to 6G show an example of the operating state of the power conversion system 1. FIGS. 6A to 6G depict the transistors Q3 to Q6 using the symbols of switches indicating the states of the transistors. Also, in FIGS. 6A to 6G, the power regeneration circuit 30 is depicted in a simplified manner.

[0052] When performing the pre-charge operation, the control circuit 22 generates control signals G1 to G4 (Figs. 5(A) to (D)). The control signal G2 is maintained at a low level (Fig. 5(B)). The control signals G1 and G3 are controlled such that either one of them becomes high level. At this time, a dead time Td is provided for the control signals G1 and G3. The control signals G3 and G4 are controlled such that the periods during which they become high level overlap each other. The period during which both control signals G3 and G4 are high level is the overlap time To. In this example, the control circuit 22 changes the control signal G4 from low level to high level at timing t21 (Fig. 5(D)). The control circuit 22 changes the control signal G1 from high level to low level at timing t22, and changes the control signal G3 from low level to high level at timing t23 (Figs. 5(A) and (C)). The control circuit 22 changes the control signal G4 from high level to low level at timing t24 (Fig. 5(D)). The control circuit 22 changes the control signal G3 from high level to low level at timing t25, and changes the control signal G1 from low level to high level at timing t27 (Figs. 5(A) and (C)). The control circuit 22 repeats such an operation in a switching period T. The power conversion device 10 performs a switching operation based on such control signals G1 to G4, and charges the capacitor 9 by supplying the power of the low-voltage battery BL from the secondary-side circuit to the primary-side circuit via the transformer 16. Specifically, the power conversion device 10 converts the power supplied from the low-voltage battery BL during the period when the control signal G3 is high level, and supplies the converted power to the capacitor 9. As a result, the voltage VH of the capacitor 9 gradually increases (Fig. 5(G)). The power conversion device 10 controls the duty ratios of the control signals G1, G3, and G4 such that this voltage VH gradually increases toward the target voltage. In this way, the power conversion device 10 performs the pre-charge operation.

[0053] In this pre-charge operation, the power regeneration circuit 30 operates to regenerate power while avoiding avalanche breakdown that may occur in transistors Q3 and Q4. The power is supplied to the capacitor 33 of the power regeneration circuit 30 via diodes 31 and 32 and is temporarily stored in this capacitor 33. The control circuit 22 generates control signals G5 and G6 based on the voltage VCreg of the capacitor 33. Thereby, the power regeneration circuit 30 regenerates power.

[0054] For example, the control circuit 22 changes the control signal G3 from a low level to a high level at timing t23 and changes the control signal G4 from a high level to a low level at timing t24 (Figs. 5(C) and (D)). Thereby, the transistor Q3 is turned on and the transistor Q4 is turned off (Fig. 6A). During the period from timing t24 to t25, as shown in Fig. 6A, in the secondary circuit, the power stored in the inductor 19 is released, and the current I1 flows in the order of the inductor 19, the winding 16B of the transformer 16, the transistor Q3, the capacitor 20, and the low-voltage battery BL. Thereby, power is supplied from the secondary circuit to the primary circuit via the transformer 16. In the primary circuit, during this period from timing t24 to t25, a charging current Ichg flows into the capacitor 9 (Fig. 5(F)), and the voltage VH rises (Fig. 5(G)).

[0055] Next, the control circuit 22 changes the control signal G3 from a high level to a low level at timing t25 (Fig. 5(C)). Thereby, the transistor Q3 is turned off (Fig. 6B). During the period from timing t25 to t26, as shown in Fig. 6B, in the secondary circuit, the residual power stored in the inductor 19 is released, and the current I1 flows in the order of the inductor 19, the winding 16B of the transformer 16, the diode 31, the capacitor 33, and the low-voltage battery BL, and in the order of the inductor 19, the diode 32, the capacitor 33, and the low-voltage battery BL. By this current I1, the capacitor 33 is charged and the voltage VCreg rises (Fig. 5(H)).

[0056] When the voltage VCreg of the capacitor 33 rises and reaches the threshold voltage VthH at timing t26 (Fig. 5(H)), the control circuit 22 changes the control signal G6 from high level to low level at this timing t26 (Fig. 5(J)). As a result, the transistor Q6 turns off (Fig. 6C). During the period from timing t26 to t28, the voltage VCreg continues to rise (Fig. 5(H)).

[0057] Next, at timing t28 when a dead time Td has elapsed from this timing t26, the control circuit 22 changes the control signal G5 from low level to high level (Fig. 5(I)). As a result, the transistor Q5 turns on (Fig. 6D). Consequently, during the period from timing t28 to t29, as shown in Fig. 6D, the regenerative current I2 flows in the order of the capacitor 33, the transistor Q5, the inductor 35, the diode 36, and the capacitor 20. That is, in the secondary side circuit, the current I1 based on the power stored in the inductor 19 and this regenerative current I2 flow. The current I1 is the current that charges the capacitor 33, and the regenerative current I2 is the current that discharges the capacitor 33. Due to this regenerative current I2, the current ILreg of the inductor 35 starts to increase at timing t28 (Fig. 5(K)).

[0058] At timing t29, when the power stored in the inductor 19 runs out, the current I1 stops flowing and the current ILch of the inductor 19 becomes zero (Fig. 5(E)). Therefore, during the period from timing t29 to t30, as shown in Fig. 6E, the regenerative current I2 continues to flow in the secondary side circuit. Since this regenerative current I2 is the current that discharges the capacitor 33, after timing t29, the voltage VCreg of the capacitor 33 decreases (Fig. 5(H)).

[0059] When the voltage VCreg of the capacitor 33 drops and reaches the threshold voltage VthL at timing t30 (Fig. 5(H)), the control circuit 22 changes the control signal G5 from high level to low level at this timing t30 (Fig. 5(I)). As a result, the transistor Q5 turns off (Fig. 6F). During the period from timing t30 to t31, the transistor Q6 is off, but the body diode D6 of the transistor Q6 turns on. Therefore, as shown in Fig. 6F, the regenerative current I2 flows in the order of the inductor 35, the diode 36, and the body diode D6 of the transistor Q6. Since the transistor Q5 turns off and no current is supplied from the capacitor 33, the current ILreg (regenerative current I2) of the inductor 35 starts to decrease (Fig. 5(K)).

[0060] Next, at timing t31 when a dead time Td has elapsed from this timing t30, the control circuit 22 changes the control signal G6 from low level to high level (Fig. 5(J)), and at timing t32, changes the control signal G4 from low level to high level (Fig. 5(D)). As a result, the transistors Q4 and Q6 turn on (Fig. 6G). Consequently, during the period from timing t32 to t33, as shown in Fig. 6G, the current I1 flows in the order of the inductor 19, the transistor Q4, the capacitor 20, and the low-voltage battery BL. That is, in the secondary circuit, the regenerative current I2 and this current I1 flow. Due to this current I1, the current ILch of the inductor 19 starts to increase at timing t32 (Fig. 5(E)), and power is stored in the inductor 19.

[0061] The power regeneration circuit 30 repeats such an operation.

[0062] As shown in FIG. 5(H), the voltage VCreg of the capacitor 33 is about the same as the threshold voltages VthL and VthH, and even when it is the highest, it is slightly higher than the threshold voltage VthH. The drain voltage of the transistor Q3 does not become higher than the voltage obtained by adding the forward voltage of the diode 31 to this voltage VCreg. Similarly, the drain voltage of the transistor Q4 does not become higher than the voltage obtained by adding the forward voltage of the diode 32 to this voltage VCreg. Therefore, in the power conversion system 1, avalanche breakdown in the transistors Q3 and Q4 can be avoided.

[0063] FIG. 7 shows an operation example of the power conversion system 1 during the pre-charge period. (A) shows the duty ratio DQ3 of the transistor Q3, (B) shows the duty ratio DQ4 of the transistor Q4, (C) shows the waveform of the voltage VH of the capacitor 9, (D) shows the waveform of the voltage VCreg of the capacitor 33 in the power regeneration circuit 30, and (E) shows the waveform of the current ILreg in the power regeneration circuit 30. In FIG. 7(D), the shaded portion indicates that the voltage VCreg changes in this portion. That is, as shown in FIG. 5(H), the voltage VCreg changes in the vicinity of the threshold voltages VthL and VthH in response to the switching operation. Similarly, in FIG. 7(E), the shaded portion indicates that the current ILreg changes in this portion.

[0064] At timing t101, the power conversion system 1 starts up, and the control circuit 22 begins to generate control signals G1 to G4 as shown in FIGS. 5(A) to (D). During the period from timing t101 to t102, the control circuit 22 gradually increases the duty ratio DQ3 of the transistor Q3 and gradually increases the duty ratio DQ4 of the transistor Q4 (FIGS. 7(A) and (B)). As a result, the power conversion system 1 starts the pre-charge operation, and the voltage VH of the capacitor 9 gradually starts to rise from 0 V (FIG. 7(C)). The voltage VCreg in the capacitor 33 is maintained near the threshold voltages VthL and VthH (FIG. 7(D)). In this example, the amplitude of the current ILreg gradually increases (FIG. 7(E)).

[0065] During the period from timing t102 to t103, the control circuit 22 maintains the duty ratios DQ3 and DQ4 (FIGS. 7(A) and (B)). The control circuit 22 checks whether the voltage VH has reached a predetermined threshold voltage Vth1.

[0066] Then, at timing t103 when the voltage VH reaches the predetermined threshold voltage Vth1, the control circuit 22 starts to gradually increase the duty ratio DQ3 again (FIG. 7(A)). On the other hand, the control circuit 22 maintains the duty ratio DQ4 (FIG. 7(B)).

[0067] Then, at timing t104 when a predetermined time has elapsed from the timing t101 when the power conversion system 1 starts up, the control circuit 22 starts to decrease the duty ratio DQ3 (FIG. 7(A)) and starts to increase the duty ratio DQ4 (FIG. 7(B)). The voltage VH of the capacitor 9 continues to rise. In this example, after timing t105, the amplitude of the current ILreg becomes almost constant (FIG. 7(E)).

[0068] Then, at timing t106, the control circuit 22 maintains the duty ratio DQ3 at a predetermined value. The voltage VH of the capacitor 9 continues to rise.

[0069] In this way, the voltage VH of the capacitor 9 rises to the target voltage. Then, thereafter, the control circuit 22 controls the operations of the transistors Q1 to Q4 so that the voltage VH of the capacitor 9 maintains its target voltage.

[0070] (Regarding short - circuit detection) Incidentally, generally in an electronic circuit, a short - circuit between terminals or between wirings can occur due to various factors. In the power conversion system 1, for example, the terminals T11 and T12 can be short - circuited. When the terminals T11 and T12 are short - circuited and the power conversion system 1 performs a pre - charge operation, power cannot be supplied from the secondary - side circuit to the primary - side circuit. In this case, for example, the power regeneration circuit 30 tries to regenerate this power, and there is a possibility that excessive power is supplied to the power regeneration circuit 30.

[0071] Therefore, in the power conversion system 1, in this example, three methods can be used to detect a short - circuit between the terminals T11 and T12. Specifically, the power conversion system 1 can detect a short - circuit between the terminals T11 and T12 by using one or more of the voltage VH of the capacitor 9, the voltage VCreg of the capacitor 33 in the power regeneration circuit 30, and the current ILreg in the power regeneration circuit 30.

[0072] For example, when the voltage VH of the capacitor 9 does not reach the threshold voltage Vth1 within a predetermined time from the timing t101 when the power conversion system 1 is activated, the control circuit 22 can determine that the terminals T11 and T12 are short - circuited.

[0073] Further, for example, when the voltage VCreg of the capacitor 33 in the power regeneration circuit 30 becomes higher than a predetermined threshold voltage Vth2 (Fig. 7(D)), the control circuit 22 can determine that the terminals T11 and T12 are short-circuited. That is, when the terminals T11 and T12 are short-circuited, excessive power is supplied to the power regeneration circuit 30, and the voltage VCreg of the capacitor 33 increases. Therefore, the control circuit 22 can determine that the terminals T11 and T12 are short-circuited based on the voltage VCreg of this capacitor 33.

[0074] Further, for example, when the current ILreg in the power regeneration circuit 30 becomes larger than a predetermined threshold current Ith (Fig. 7(E)), the control circuit 22 can determine that the terminals T11 and T12 are short-circuited. That is, when the terminals T11 and T12 are short-circuited, excessive power is supplied to the power regeneration circuit 30, and the current ILreg in the power regeneration circuit 30 increases. Therefore, the control circuit 22 can determine that the terminals T11 and T12 are short-circuited based on the current ILreg in the power regeneration circuit 30.

[0075] When the power conversion system 1 detects a short circuit between the terminals T11 and T12 by any of these three methods, for example, it protects the power regeneration circuit 30 by setting the duty ratio DQ3 of the transistor Q3 and the duty ratio DQ4 of the transistor Q4 to small values.

[0076] Hereinafter, the three methods for detecting a short circuit between the terminals T11 and T12 will be described in detail. Hereinafter, the method using the voltage VH, the method using the voltage VCreg, and the method using the current ILreg will be described in this order.

[0077] (Method using the voltage VH) FIG. 8 shows an example of a method for detecting a short circuit between terminal T11 and terminal T12 using voltage VH. (A) shows the duty ratio DQ3 of transistor Q3, (B) shows the duty ratio DQ4 of transistor Q4, and (C) shows the waveform of voltage VH of capacitor 9. In FIG. 8, the dashed line indicates the case where no short circuit occurs, and the solid line indicates the case where a short circuit occurs. That is, the operation indicated by the dashed line in FIG. 8 is the same as the operation shown in FIG. 7. In this example, the short circuit between terminal T11 and terminal T12 occurs before the start of the precharge operation.

[0078] When the power conversion system 1 starts at timing t111, during the period from timing t111 to t112, the control circuit 22 gradually increases the duty ratio DQ3 of transistor Q3 and gradually increases the duty ratio DQ4 of transistor Q4 (FIGS. 8(A) and (B)). Then, at timing t112, the control circuit 22 maintains the duty ratios DQ3 and DQ4.

[0079] When terminals T11 and T12 are short-circuited, voltage VH is maintained at 0V without rising (FIG. 8(C)). In this case, within a predetermined time from the timing t111 when the power conversion system 1 starts, voltage VH does not reach the threshold voltage Vth1. Therefore, at timing t113, which is the end timing of this predetermined time, the control circuit 22 sets the duty ratio DQ3 to a low duty ratio D11 (FIG. 8(A)). This duty ratio D11 is set to a value small enough that the power regeneration circuit 30 is hardly damaged. That is, by reducing the duty ratio DQ3, the power conversion system 1 limits the power supplied from the secondary side circuit to the primary side circuit. Since terminals T11 and T12 are short-circuited, the power conversion system 1 cannot supply power from the secondary side circuit to the primary side circuit, and this limited power is supplied to the power regeneration circuit 30. Since the power regeneration circuit 30 is supplied with power limited in this way, the possibility of the power regeneration circuit 30 being damaged can be reduced.

[0080] Note that in this example, at timing t113, control circuit 22 sets duty ratio DQ3 to a low duty ratio D11 and maintains duty ratio DQ4, but it is not limited thereto. For example, control circuit 22 may set duty ratio DQ3 to a low duty ratio D11 and, similarly, set duty ratio DQ4 to a low duty ratio.

[0081] Then, for example, at timing t114 when a predetermined time has elapsed since the start timing t111 of power conversion system 1, control circuit 22 sets duty ratios DQ3 and DQ4 to zero (Figs. 8(A) and (B)).

[0082] Fig. 9 shows an example of a method for detecting a short circuit between terminals T11 and T12 using voltage VH, where (A) shows the duty ratio DQ3 of transistor Q3, (B) shows the duty ratio DQ4 of transistor Q4, and (C) shows the waveform of voltage VH of capacitor 9. In this example, the short circuit between terminals T11 and T12 occurs after the start of the precharge operation.

[0083] When power conversion system 1 starts at timing t121, during the period from timing t121 to t122, control circuit 22 gradually increases the duty ratio DQ3 of transistor Q3 and gradually increases the duty ratio DQ4 of transistor Q4 (Figs. 9(A) and (B)). As a result, the voltage VH of capacitor 9 gradually starts to rise from 0V (Fig. 9(C)). Then, at timing t122, control circuit 22 maintains duty ratios DQ3 and DQ4 (Figs. 9(A) and (B)). Then, at timing t123 when voltage VH reaches a predetermined threshold voltage Vth1, control circuit 22 starts to gradually increase duty ratio DQ3 again (Fig. 9(A)). Then, at timing t124 when a predetermined time has elapsed since the start timing t121 of power conversion system 1, control circuit 22 starts to decrease duty ratio DQ3 (Fig. 9(A)) and starts to increase duty ratio DQ4 (Fig. 9(B)).

[0084] And in this example, at timing t125, a short circuit occurs between terminal T11 and terminal T12. As a result, the voltage VH of capacitor 9 becomes 0V, falling below the threshold voltage Vth1 (Fig. 9(C)). The control circuit 22 detects that the voltage VH has fallen below the threshold voltage Vth1, and based on this detection result, sets the duty ratio DQ3 to a low duty ratio D12 and sets the duty ratio DQ4 to a low duty ratio D13 (Fig. 9(A), (B)). These duty ratios D12 and D13 are set to small values such that the power regeneration circuit 30 is hardly damaged, respectively.

[0085] Note that in this example, when the control circuit 22 detects a short circuit, it decreases the duty ratio DQ3 to the duty ratio D12 and decreases the duty ratio DQ4 to the duty ratio D13, but it is not limited to this. For example, the control circuit 22 may decrease only one of the duty ratios DQ3 and DQ4. Specifically, for example, when a short circuit occurs at timing t124, the control circuit 22 can decrease the duty ratio DQ3 to the duty ratio D12 and maintain the duty ratio DQ4.

[0086] (Method using voltage VCreg) Fig. 10 shows an example of a method for detecting a short circuit between terminal T11 and terminal T12 using the voltage VCreg of capacitor 33 in the power regeneration circuit 30. (A) shows the duty ratio DQ3 of transistor Q3, (B) shows the duty ratio DQ4 of transistor Q4, (C) shows the waveform of the voltage VH of capacitor 9, and (D) shows the waveform of the voltage VCreg of capacitor 33 in the power regeneration circuit 30. In this example, the short circuit between terminal T11 and terminal T12 occurs after the start of the precharge operation. Note that it is not limited to this, and the short circuit may occur before the start of the precharge operation.

[0087] At timing t131, when the power conversion system 1 starts up, during the period from timing t131 to t132, the control circuit 22 gradually increases the duty ratio DQ3 of the transistor Q3 and gradually increases the duty ratio DQ4 of the transistor Q4 (Figs. 10(A), (B)). As a result, the voltage VH of the capacitor 9 starts to gradually increase from 0V (Fig. 10(C)). Then, at timing t132, the control circuit 22 maintains the duty ratios DQ3 and DQ4 (Figs. 10(A), (B)). And at timing t133 when the voltage VH reaches a predetermined threshold voltage Vth1, the control circuit 22 starts to gradually increase the duty ratio DQ3 again (Fig. 10(A)). Then, at timing t134 when a predetermined time has elapsed since the power conversion system 1 started up at timing t131, the control circuit 22 starts to decrease the duty ratio DQ3 (Fig. 10(A)) and starts to increase the duty ratio DQ4 (Fig. 10(B)).

[0088] And in this example, at timing t135, a short circuit occurs between the terminal T11 and the terminal T12. As a result, the voltage VH of the capacitor 9 becomes 0V (Fig. 10(C)). Since the power conversion system 1 cannot supply power from the secondary side circuit to the primary side circuit, the power is supplied to the power regeneration circuit 30. As a result, the voltage VCreg transiently exceeds the threshold voltage Vth2 (Fig. 10(D)). The control circuit 22 detects that the voltage VCreg has exceeded the threshold voltage Vth2, and based on this detection result, sets the duty ratio DQ3 to a low duty ratio D12 and sets the duty ratio DQ4 to a low duty ratio D13 (Figs. 10(A), (B)). These duty ratios D12 and D13 are set to small values such that the power regeneration circuit 30 is hardly damaged, respectively.

[0089] In this example, when the control circuit 22 detects a short circuit, it decreases the duty ratio DQ3 to the duty ratio D12 and decreases the duty ratio DQ4 to the duty ratio D13. However, it is not limited to this. For example, the control circuit 22 may decrease only one of the duty ratios DQ3 and DQ4. Specifically, for example, when a short circuit occurs at the timing t134, the control circuit 22 can decrease the duty ratio DQ3 to the duty ratio D12 and maintain the duty ratio DQ4.

[0090] (Method using the current ILreg) FIG. 11 shows an example of a method for detecting a short circuit between the terminals T11 and T12 using the current ILreg in the power regeneration circuit 30. (A) shows the duty ratio DQ3 of the transistor Q3, (B) shows the duty ratio DQ4 of the transistor Q4, (C) shows the waveform of the voltage VH of the capacitor 9, and (D) shows the waveform of the current ILreg in the power regeneration circuit 30. In this example, the short circuit between the terminals T11 and T12 occurs after the start of the precharge operation. Note that it is not limited to this, and the short circuit may occur before the start of the precharge operation.

[0091] At timing t141, when the power conversion system 1 starts up, during the period from timing t141 to t142, the control circuit 22 gradually increases the duty ratio DQ3 of the transistor Q3 and gradually increases the duty ratio DQ4 of the transistor Q4 (Figs. 11(A) and (B)). As a result, the voltage VH of the capacitor 9 starts to gradually increase from 0V (Fig. 11(C)). Then, at timing t142, the control circuit 22 maintains the duty ratios DQ3 and DQ4 (Figs. 11(A) and (B)). And at timing t143 when the voltage VH reaches a predetermined threshold voltage Vth1, the control circuit 22 starts to gradually increase the duty ratio DQ3 again (Fig. 11(A)). Then, at timing t144 when a predetermined time has elapsed since the power conversion system 1 started up at timing t141, the control circuit 22 starts to decrease the duty ratio DQ3 (Fig. 11(A)) and starts to increase the duty ratio DQ4 (Fig. 11(B)).

[0092] And in this example, at timing t145, a short circuit occurs between the terminal T11 and the terminal T12. As a result, the voltage VH of the capacitor 9 becomes 0V (Fig. 11(C)). Since the power conversion system 1 cannot supply power from the secondary-side circuit to the primary-side circuit, the power is supplied to the power regeneration circuit 30. As a result, the current ILreg transiently exceeds the threshold current Ith (Fig. 11(D)). The control circuit 22 detects that the current ILreg has exceeded the threshold current Ith, and based on this detection result, sets the duty ratio DQ3 to a low duty ratio D12 and sets the duty ratio DQ4 to a low duty ratio D13 (Figs. 11(A) and (B)). These duty ratios D12 and D13 are set to small values such that the power regeneration circuit 30 is hardly damaged, respectively.

[0093] Note that in this example, when the control circuit 22 detects a short circuit, it decreases the duty ratio DQ3 to the duty ratio D12 and decreases the duty ratio DQ4 to the duty ratio D13, but it is not limited thereto. For example, the control circuit 22 may decrease only one of the duty ratios DQ3 and DQ4. Specifically, for example, when a short circuit occurs at the timing t144, the control circuit 22 can decrease the duty ratio DQ3 to the duty ratio D12 and maintain the duty ratio DQ4.

[0094] Thus, in the power conversion system 1, a first power terminal (terminals T11, T12) having a first connection terminal (terminal T11) and a second connection terminal (terminal T12), a switching circuit 14 connected to the first power terminal (terminal T11), 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 (transistors Q3, Q4), a first inductor (inductor 19) having one end and the other end, and a smoothing circuit 18 including a first capacitor (capacitor 20) having one end connected to the other end of the first inductor (inductor 19) and the other end connected to a reference node (reference voltage line L22); a power regeneration circuit 30 connected to the rectifier circuit 17 and capable of regenerating power to the first capacitor (capacitor 20); a control circuit 22 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 (capacitor 20) and a second connection terminal (terminal T22) connected to the reference node are provided. The control circuit 22 is configured to detect a short circuit between the first connection terminal (terminal T11) and the second connection terminal (terminal T12) at the first power terminal (terminals T11, T12) based on one or both of the voltage and current in the power regeneration circuit 30 during a predetermined period (precharge period) before a period (power conversion period) in which power is supplied from the first power terminal (terminals T11, T12) to the second power terminal (terminals T21, T22). For example, when a short circuit occurs between terminals T11 and T12, the power conversion system 1 cannot supply power from the secondary side circuit to the primary side circuit, so this power is supplied to the power regeneration circuit 30. Therefore, the control circuit 22 can detect this short circuit based on one or both of the voltage and current in the power regeneration circuit 30. And the control circuit 22 can limit the power supplied to the power regeneration circuit 30, for example, by restricting the precharge operation based on this detection result.As a result, in the power conversion system 1, the power regeneration circuit 30 can be protected.

[0095] 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 the 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 the reference node (reference voltage line L22). The power regeneration circuit 30 includes a first 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), a second diode (diode 32) having an anode connected to one end of the second rectifying switching element (transistor Q4) and a cathode connected to the first node (node N1), and a second capacitor (capacitor 33) having one end connected to the first node (node N1) and the other end connected to the reference node (reference voltage line L22). The control circuit 22 is configured to be able to detect a short circuit based on the voltage across the second capacitor (capacitor 33) during a predetermined period (precharge period). For example, when a short circuit occurs between terminals T11 and T12, the power conversion system 1 cannot supply power from the secondary side circuit to the primary side circuit, so this power is supplied to the power regeneration circuit 30. Therefore, the control circuit 22 can detect this short circuit based on the voltage VCreg of the capacitor 33 in the power regeneration circuit 30. Then, the control circuit 22 can limit the power supplied to the power regeneration circuit 30, for example, by restricting the precharge operation based on this detection result. As a result, in the power conversion system 1, the power regeneration circuit 30 can be protected.

[0096] In the power conversion system 1, the second winding (winding 16B) has 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 the reference node (reference voltage line L22), and a second rectifying switching element (transistor Q4) having one end connected to one end of the second winding (winding 16B) and the other end connected to the reference node (reference voltage line L22). The power regeneration circuit 30 includes a first 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), a second diode (diode 32) having an anode connected to one end of the second rectifying switching element (transistor Q4) and a cathode connected to the first node (node N1), a second capacitor (capacitor 33) having one end connected to the first node (node N1) and the other end connected to the reference node (reference voltage line L22), a first regenerative switching element (transistor Q5) having one end connected to the first node (node N1) and the other end connected to the second node (node N2), a second regenerative 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 third diode (diode 36) provided in a path connecting the second node (node N2) and one end of the first capacitor. The control circuit 22 is configured to be able to detect a short circuit based on the current flowing from the second node (node N2) toward one end of the first capacitor (capacitor 20) during a predetermined period (precharge period). For example, when a short circuit occurs between terminals T11 and T12, the power conversion system 1 cannot supply power from the secondary side circuit to the primary side circuit, so this power is supplied to the power regeneration circuit 30. Therefore, the control circuit 22 can detect this short circuit based on the current ILreg flowing from node N2 toward one end of capacitor 20 in the power regeneration circuit 30.Then, based on this detection result, for example, the control circuit 22 can limit the power supplied to the power regeneration circuit 30 by restricting the precharge operation. As a result, in the power conversion system 1, the power regeneration circuit 30 can be protected.

[0097] Also, in the power conversion system 1, the control circuit 22 can change the duty ratio of one or more rectifying switching elements (transistors Q3, Q4) in a predetermined sequence during a predetermined period (precharge period), and when a short circuit is detected, the duty ratio of at least one of the one or more rectifying switching elements can be reduced to a predetermined duty ratio. Thereby, for example, when the control circuit 22 detects a short circuit between the terminals T11 and T12, in the examples of FIGS. 10 and 11, for example, the duty ratio DQ3 of the transistor Q3 can be reduced to the duty ratio D12, and the duty ratio DQ4 of the transistor Q4 can be reduced to the duty ratio D13. Thereby, in the power conversion system 1, the precharge operation can be restricted, and the power supplied to the power regeneration circuit 30 can be restricted. As a result, in the power conversion system 1, the power regeneration circuit 30 can be protected.

[0098] [Effect] As described above, in the present embodiment, a first power terminal having a first connection terminal and a second connection 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 connected to the second winding and having one or more rectifying switching elements, 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 are included in a smoothing circuit. A power regeneration circuit is connected to the rectifier circuit and can regenerate power to the first capacitor. A control circuit can control 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 is provided. The control circuit can detect a short circuit between the first connection terminal and the second connection terminal at the first power terminal based on one or both of the voltage and the current in the power regeneration circuit during a predetermined period before a period in which power is supplied from the first power terminal toward the second power terminal. As a result, the power regeneration circuit can be protected.

[0099] In the present embodiment, the second winding has one end connected to 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 one end of the second winding and the other end connected to the reference node. The power regeneration circuit has a first diode having an anode connected to one end of the first rectifying switching element and a cathode connected to the first node, a second diode having an anode connected to one end of the second rectifying switching element and a cathode connected to the first node, and a second capacitor having one end connected to the first node and the other end connected to the reference node. The control circuit can detect a short circuit based on the voltage in the second capacitor during a predetermined period. As a result, the power regeneration circuit can be protected.

[0100] 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 power regeneration circuit includes a first diode having an anode connected to one end of the first rectifying switching element and a cathode connected to the first node, a second diode having an anode connected to one end of the second rectifying switching element and a cathode connected to 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, and a second inductor and a third diode provided in a path connecting the second node and one end of the first capacitor. The control circuit is configured to be able to detect a short circuit based on the current flowing from the second node toward one end of the first capacitor during a predetermined period. As a result, the power regeneration circuit can be protected.

[0101] In this embodiment, the control circuit can change the duty ratio of one or more rectifying switching elements in a predetermined sequence during a predetermined period, and when a short circuit is detected, the duty ratio of at least one of the one or more rectifying switching elements can be reduced to a predetermined duty ratio. As a result, the power regeneration circuit can be protected.

[0102] [Modification Example 1] In the above embodiment, immediately after detecting the short circuit of terminals T11 and T12, the duty ratios DQ3 and DQ4 were set to low duty ratios and the precharge operation was continued while being restricted, but the present invention is not limited to this. Instead, for example, as shown in FIG. 12, immediately after detecting the short circuit, the precharge operation may be stopped, and after a predetermined time has elapsed, the precharge operation may be restarted while being restricted. In this example, the power conversion system 1 detects the short circuit of terminals T11 and T12 using both the voltage VCreg and the current ILreg in the power regeneration circuit 30.

[0103] In this example, at timing t155, a short circuit occurs between terminals T11 and T12. As a result, the voltage VH of the capacitor 9 becomes 0V (FIG. 12(C)). Since the power conversion system 1 cannot supply power from the secondary side circuit to the primary side circuit, power is supplied to the power regeneration circuit 30. As a result, the voltage VCreg transiently exceeds the threshold voltage Vth2 (FIG. 12(D)), and the current ILreg transiently exceeds the threshold current Ith (FIG. 12(E)). The control circuit 22 detects that the voltage VCreg has exceeded the threshold voltage Vth2 and that the current ILreg has exceeded the threshold current Ith, and based on these detection results, sets the duty ratio DQ3 to zero and sets the duty ratio DQ4 to zero (FIGS. 12(A) and (B)). That is, the control circuit 22 stops the precharge operation. Then, at timing t156 when a predetermined time has elapsed from this timing t155, the control circuit 22 restarts the precharge operation, sets the duty ratio DQ3 to the duty ratio D12, and sets the duty ratio DQ4 to the duty ratio D13 (FIGS. 12(A) and (B)). These duty ratios D12 and D13 are set to small values such that the power regeneration circuit 30 is hardly damaged.

[0104] [Modification Example 2] In the above-described embodiment, for example, as shown in FIGS. 10 and 11, immediately after detecting a short circuit between terminals T11 and T12, the duty ratios DQ3 and DQ4 were set to low duty ratios, and the precharge operation was continued while being restricted. During the period in which the precharge operation is restricted, the power conversion system 1 may continuously check whether the short circuit between terminals T11 and T12 has been eliminated. Then, if the short circuit is not eliminated, the power conversion system 1 can stop the precharge operation as shown in FIG. 13. Also, if the short circuit is eliminated, the power conversion system 1 may remove the restriction on the precharge operation and resume the precharge operation as shown in FIG. 14.

[0105] In the example of FIG. 13, at timing t165, a short circuit occurs between terminals T11 and T12. As a result, the voltage VH of capacitor 9 becomes 0 V (FIG. 13(C)). Since the power conversion system 1 cannot supply power from the secondary-side circuit to the primary-side circuit, power is supplied to the power regeneration circuit 30. As a result, the voltage VCreg transiently exceeds the threshold voltage Vth2 (FIG. 13(D)), and the current ILreg transiently exceeds the threshold current Ith (FIG. 13(E)). The control circuit 22 detects that the voltage VCreg has exceeded the threshold voltage Vth2 and that the current ILreg has exceeded the threshold current Ith, and based on these detection results, sets the duty ratio DQ3 to a low duty ratio D12 and sets the duty ratio DQ4 to a low duty ratio D13 (FIGS. 13(A) and (B)). The control circuit 22 continuously checks whether the short circuit between terminals T11 and T12 has been eliminated, for example, based on the voltage VH of capacitor 9, during a period of a predetermined length starting from timing t165 (the period from timing t165 to t166). Specifically, the control circuit 22 continuously checks whether the short circuit has been eliminated by checking whether the voltage VH is higher than the threshold voltage Vth1. In this example, the short circuit is not eliminated, and the voltage VH remains at 0 V. Therefore, at timing t166, the control circuit 22 sets the duty ratio DQ3 to zero and sets the duty ratio DQ4 to zero (FIGS. 13(A) and (B)). That is, the control circuit 22 stops the precharge operation.

[0106] In the example of FIG. 14, at timing t175, a short circuit occurs between terminals T11 and T12. As a result, the voltage VH of capacitor 9 becomes 0 V (FIG. 14(C)). Since the power conversion system 1 cannot supply power from the secondary-side circuit to the primary-side circuit, power is supplied to the power regeneration circuit 30. As a result, the voltage VCreg transiently exceeds the threshold voltage Vth2 (FIG. 14(D)), and the current ILreg transiently exceeds the threshold current Ith (FIG. 14(E)). The control circuit 22 detects that the voltage VCreg has exceeded the threshold voltage Vth2 and that the current ILreg has exceeded the threshold current Ith, and based on these detection results, sets the duty ratio DQ3 to a low duty ratio D12 and sets the duty ratio DQ4 to a low duty ratio D13 (FIGS. 14(A), (B)). The control circuit 22 continuously checks whether the short circuit between terminals T11 and T12 has been eliminated based on, for example, the voltage VH of capacitor 9 during a period of a predetermined length starting from timing t175. In this example, at timing t176 within this period of the predetermined length, the short circuit is eliminated and the voltage VH starts to rise (FIG. 14(C)). Then, at timing t177, the voltage VH exceeds the threshold voltage Vth1. Based on this detection result of the voltage VH, the control circuit 22 starts to increase the duty ratios DQ3 and DQ4 (FIGS. 14(A), 14(B)). In this way, the control circuit 22 resumes the precharge operation.

[0107] In the above description, this modification is applied to the above-described embodiments (FIGS. 10, 11, etc.), but the present invention is not limited thereto. Instead, for example, this modification may be applied to Modification 1 (FIG. 12). That is, in the power conversion system 1 according to Modification 1, as shown in FIG. 12, the control circuit 22 stops the precharge operation immediately after detecting a short circuit, and after a predetermined time has elapsed, resumes the precharge operation while restricting it. During the period in which the precharge operation is restricted, the power conversion system 1 may continuously check whether the short circuit between terminals T11 and T12 has been eliminated.

[0108] [Modification Example 3] 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. Hereinafter, several examples will be given to explain this modification example.

[0109] FIG. 15 shows a configuration example of a power conversion system 2 according to this modification example. The power conversion system 2 includes a power conversion device 40. The power conversion device 40 has terminals T11, T12, a voltage sensor 11, a switching circuit 44, an inductor 45, a transformer 46, a rectifier circuit 47, a smoothing circuit 18, a power regeneration circuit 30, a voltage sensor 21, a control circuit 52, and terminals T21, T22. The high-voltage battery BH, switches SW1, SW2, the voltage sensor 11, the switching circuit 44, and the inductor 45 constitute the primary-side circuit of the power conversion system 2, and the rectifier circuit 47, 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.

[0110] The switching circuit 44 has transistors Q11 to Q14. The drain of transistor Q11 is connected to voltage line L11, the source is connected to node N21, and control signal G11 is supplied to the gate. The drain of transistor Q12 is connected to node N21, the source is connected to reference voltage line L12, and control signal G12 is supplied to the gate. The drain of transistor Q13 is connected to voltage line L11, the source is connected to node N22, and control signal G13 is supplied to the gate. The drain of transistor Q14 is connected to node N22, the source is connected to reference voltage line L12, and control signal G14 is supplied to the gate.

[0111] One end of the inductor 45 is connected to node N21, and the other end is connected to a winding 46A (described later) in the transformer 46.

[0112] Transformer 46 has windings 46A, 46B, and 46C. Winding 46A is the primary winding of transformer 46, one end of which is connected to the other end of inductor 45, and the other end is connected to node N22. Windings 46B and 46C are the secondary windings of transformer 46. One end of winding 46B is connected to node N23, and the other end is connected to voltage line L21A. One end of winding 46C is connected to voltage line L21A, and the other end is connected to node N24.

[0113] Rectifier circuit 47 has transistors Q15 and Q16. The drain of transistor Q15 is connected to node N24, the source is connected to reference voltage line L22, and control signal G15 is supplied to the gate. The drain of transistor Q16 is connected to node N23, the source is connected to reference voltage line L22, and control signal G16 is supplied to the gate.

[0114] Figure 16 shows a configuration example of 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.

[0115] Control circuit 52 (Figure 15) is configured to control the operation of power conversion device 40 based on the voltage VH detected by voltage sensor 11, the voltage VL detected by voltage sensor 21, the voltage VCreg detected by voltage sensor 34 of power regeneration circuit 30, and the current ILreg detected by current sensor 37 of power regeneration circuit 30.

[0116] FIG. 17 shows a configuration example of another power conversion system 3 according to this modified example. The power conversion system 3 includes a power conversion device 60. The power conversion device 60 has terminals T11, T12, a voltage sensor 11, a switching circuit 44, an inductor 45, a transformer 16, a rectifier circuit 67, a smoothing circuit 18, a power regeneration circuit 80, a voltage sensor 21, a control circuit 72, and terminals T21, T22. The high-voltage battery BH, switches SW1, SW2, the voltage sensor 11, the switching circuit 44, and the inductor 45 constitute the primary-side circuit of the power conversion system 3, and the rectifier circuit 67, the smoothing circuit 18, the power regeneration circuit 80, the voltage sensor 21, and the low-voltage battery BL constitute the secondary-side circuit of the power conversion system 3.

[0117] One end of the winding 16B of the transformer 16 is connected to the node N31, and the other end is connected to the node N32.

[0118] The rectifier circuit 67 has transistors Q21 to Q24. The drain of the transistor Q21 is connected to the voltage line L21A, the source is connected to the node N31, and the control signal G21 is supplied to the gate. The drain of the transistor Q22 is connected to the node N31, the source is connected to the reference voltage line L22, and the control signal G22 is supplied to the gate. The drain of the transistor Q23 is connected to the voltage line L21A, the source is connected to the node N32, and the control signal G23 is supplied to the gate. The drain of the transistor Q24 is connected to the node N32, the source is connected to the reference voltage line L22, and the control signal G24 is supplied to the gate.

[0119] FIG. 18 shows a configuration example of the power regeneration circuit 80. The power regeneration circuit 80 has a diode 31, a capacitor 33, a voltage sensor 34, transistors Q5, Q6, an inductor 35, and a diode 36. That is, the power regeneration circuit 80 is obtained by removing the diode 32 from the power regeneration circuit 30 (FIG. 2). The anode of the diode 31 is connected to the voltage line L21A.

[0120] The control circuit 72 is configured to control the operation of the power conversion device 60 based on the voltage VH detected by the voltage sensor 11, the voltage VL detected by the voltage sensor 21, and the voltage VCreg detected by the voltage sensor 34 of the power regeneration circuit 80.

[0121] [Other Modification Examples] Also, two or more of these modification examples may be combined.

[0122] The present invention has been described with reference to the embodiments and modification examples, but the present invention is not limited to these embodiments and the like, and various modifications are possible.

[0123] For example, in the above embodiment, the power conversion system 1 is configured to perform a step-down operation in the power conversion operation, but the present invention is not limited thereto, and a step-up operation may be performed.

[0124] 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.

[0125] Furthermore, the present disclosure may take the following aspects.

[0126] (1) A first power terminal having a first connection terminal and a second connection 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 power to the first capacitor, A control circuit capable of controlling the operations of the switching circuit, the rectifying 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 During a predetermined period prior to a period in which power is supplied from the first power terminal toward the second power terminal, the control circuit can detect a short circuit between the first connection terminal and the second connection terminal at the first power terminal based on one or both of the voltage and current in the power regeneration circuit 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 power regeneration circuit A first diode having an anode connected to the one end of the first rectifying switching element and a cathode connected to a first node, A second diode having an anode connected to the one end of the second rectifying switching element and a cathode connected to the first node, A second capacitor having one end connected to the first node and the other end connected to the reference node and having During the predetermined period, the control circuit can detect the short circuit based on the voltage across the second capacitor. The power conversion device according to (1) above. (3) 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 power regeneration circuit a first diode having an anode connected to the one end of the first rectifying switching element and a cathode connected to a first node; a second diode having an anode connected to the one end of the second rectifying switching element and a cathode connected to 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 third diode provided in a path connecting the second node and the one end of the first capacitor and has The control circuit can detect the short circuit based on the current flowing from the second node toward the one end of the first capacitor during the predetermined period. The power conversion device according to (1) or (2) above. (4) The control circuit can change the duty ratio of the one or more rectifying switching elements in a predetermined sequence during the predetermined period, and can reduce the duty ratio of at least one of the one or more rectifying switching elements to a predetermined duty ratio when the short circuit is detected. The power conversion device according to any one of (1) to (3) above. (5) When the control circuit detects the short circuit, During the predetermined period, it is possible to change the duty ratio of the one or more rectifying switching elements in a predetermined sequence, when the short circuit is detected, it is possible to stop the operations of the switching circuit, the rectifying circuit, and the power regeneration circuit, and then, during a subsequent predetermined period, set the duty ratio of at least one of the one or more rectifying switching elements to a predetermined duty ratio and operate the switching circuit, the rectifying circuit, and the power regeneration circuit. The power conversion device according to any one of (1) to (3). (6) After setting the duty ratio of at least one of the one or more rectifying switching elements to the predetermined duty ratio during the predetermined period, if the short circuit does not disappear within a predetermined time, the control circuit can stop the operations of the switching circuit, the rectifying circuit, and the power regeneration circuit. The power conversion device according to (4) or (5). (7) After setting the duty ratio of at least one of the one or more rectifying switching elements to the predetermined duty ratio during the predetermined period, if the short circuit disappears within a predetermined time, the control circuit can change the duty ratio of the one or more rectifying switching elements in a predetermined sequence. The power conversion device according to (4) or (5). (8) A first battery having a first terminal and a second terminal, A capacitor having a first terminal and a second terminal, A first switch provided in a path connecting the first terminal of the first battery and the first terminal of the capacitor, A second switch provided in a path connecting the second terminal of the first battery and the second terminal of the capacitor, A power conversion device, a second battery and comprises the power conversion device includes a first power terminal connected to the capacitor, 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 power to the first capacitor, a control circuit capable of controlling operations of the switching circuit, the rectifier circuit, and the power regeneration circuit, 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 a second power terminal connected to the second battery comprises the control circuit is capable of detecting a short circuit between the first connection terminal and the second connection terminal at the first power terminal based on one or both of a voltage and a current in the power regeneration circuit during a predetermined period before a period of supplying power from the first power terminal to the second power terminal a power conversion system

Description of Reference Numerals

[0127] 1 to 3... power conversion system, 9... capacitor, 10, 40, 60... power conversion device, 11... voltage sensor, 12... capacitor, 13... resistive element, 14, 44... switching circuit, 15, 45... inductor, 16, 46... transformer, 16A, 16B, 46A, 46B, 46C... winding, 17, 47, 57... rectifier circuit, 18... smoothing circuit, 19... inductor, 20... capacitor, 21... voltage sensor, 22, 52, 72... control circuit, 30, 80... power regeneration circuit, 31, 32... diode, 33... capacitor, 34... voltage sensor, 35... inductor, 36... diode, 37... current sensor, BH... high-voltage battery, BL... low-voltage battery, D1 to D6... body diode, G1 to G6, G11 to G16, G21 to G24... control signal, L11, L21A, L21B... voltage line, L12, L22... reference voltage line, N1, N2, N11 to N13, N21 to N24, N31, N32... node, Q1 to Q6, Q11 to Q16, Q21 to Q24... transistor, SW1, SW2... switch, T11, T12, T21, T22... terminal.

Claims

1. A first power terminal having a first connection terminal and a second connection 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 power 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 control circuit is capable of detecting a short circuit between the first connection terminal and the second connection terminal at the first power terminal based on one or both of the voltage and current in the power regeneration circuit during a predetermined period before a period of supplying power from the first power terminal to the second power terminal. 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 power regeneration circuit has a first diode having an anode connected to the one end of the first rectifying switching element and a cathode connected to a first node; a second diode having an anode connected to the one end of the second rectifying switching element and a cathode connected to the first node; and a second capacitor having one end connected to the first node and the other end connected to the reference node and has; The control circuit is capable of detecting the short circuit based on the voltage in the second capacitor during the predetermined period. The power conversion device according to Claim 1.

3. 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 power regeneration circuit includes a first diode having an anode connected to the one end of the first rectifying switching element and a cathode connected to a first node, a second diode having an anode connected to the one end of the second rectifying switching element and a cathode connected to 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, and a second inductor and a third diode provided in a path connecting the second node and the one end of the first capacitor. It has The control circuit can detect the short circuit based on the current flowing from the second node toward the one end of the first capacitor during the predetermined period. The power conversion device according to claim 1.

4. The control circuit can change the duty ratio of the one or more rectifying switching elements in a predetermined sequence during the predetermined period, and when the short circuit is detected, can reduce the duty ratio of at least one of the one or more rectifying switching elements to a predetermined duty ratio. The power conversion device according to claim 1.

5. When the control circuit detects the short circuit, it can change the duty ratio of the one or more rectifying switching elements in a predetermined sequence during the predetermined period, and when the short circuit is detected, it can stop the operations of the switching circuit, the rectifying circuit, and the power regeneration circuit. In a subsequent predetermined period, the duty ratio of at least one of the one or more rectifying switching elements is set to a predetermined duty ratio, and it is possible to operate the switching circuit, the rectifying circuit, and the power regeneration circuit The power conversion device according to claim 1

6. In the predetermined period, after setting the duty ratio of at least one of the one or more rectifying switching elements to the predetermined duty ratio, if the short circuit does not disappear within a predetermined time, the control circuit can stop the operations of the switching circuit, the rectifying circuit, and the power regeneration circuit The power conversion device according to claim 4

7. In the predetermined period, after setting the duty ratio of at least one of the one or more rectifying switching elements to the predetermined duty ratio, if the short circuit disappears within a predetermined time, the control circuit can change the duty ratio of the one or more rectifying switching elements in a predetermined sequence The power conversion device according to claim 4

8. A first battery having a first terminal and a second terminal A capacitor having a first terminal and a second terminal A first switch provided in a path connecting the first terminal of the first battery and the first terminal of the capacitor A second switch provided in a path connecting the second terminal of the first battery and the second terminal of the capacitor A power conversion device A second battery Comprising The power conversion device A first power terminal connected to the capacitor 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 rectifying 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 rectifying circuit and capable of regenerating power to the first capacitor A control circuit capable of controlling the operations of the switching circuit, the rectifying circuit, and the power regeneration circuit 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 a second power terminal connected to the second battery comprising During a predetermined period before a period in which power is supplied from the first power terminal toward the second power terminal, the control circuit can detect a short circuit between the first connection terminal and the second connection terminal at the first power terminal based on one or both of the voltage and current in the power regeneration circuit Power conversion system

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