Power conversion device and power conversion system

Abstract

The power conversion device of the present application includes a first power terminal, a conversion section, a transformer, a rectification section, a second power terminal, and a control section. The conversion section includes a first switching element, a second switching element, a third switching element, and a fourth switching element. The first switching element is provided on a path connecting a first power node and a first node, the second switching element is provided on a path connecting the first node and a second power node, the third switching element is provided on a path connecting the first power node and a second node, and the fourth switching element is provided on a path connecting the second node and the second power node. The transformer includes a first winding and a second winding, and the first winding is connected to the conversion section. The control section controls the operation of the conversion section and the rectification section during a predetermined period to supply power from the second power terminal to the first power terminal, and the predetermined period is different from a period during which power is supplied from the first power terminal to the second power terminal.

Description

Technical Field

[0001] This invention relates to a power conversion device and a power conversion system for converting electricity. Background Technology

[0002] For a power conversion device that supplies power from a primary battery to a secondary battery, a so-called pre-charging operation is performed before the power conversion operation. This involves supplying power from the secondary battery to the primary capacitor via the power conversion device. For example, Patent Document 1 discloses a technique in which the current value of the secondary choke coil is detected during the pre-charging operation, and the operation of the secondary switching element is controlled based on the detection result.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2017-034862 Summary of the Invention

[0006] In power conversion devices, a simple structure is generally desired. In power conversion devices that perform pre-charging operations, a simple structure with fewer additional parts is also desired.

[0007] The aim is to provide a power conversion device and power conversion system that can perform pre-charging operation with a simple structure and few additional parts.

[0008] An embodiment of the power conversion device of the present invention includes a first power terminal, a conversion section, a transformer, a rectifier section, a second power terminal, and a control section. The first power terminal has a first terminal and a second terminal. The conversion section has a first switching element, a second switching element, a third switching element, and a fourth switching element. The first switching element is disposed on a path connecting a first power node to a first node, and the first power node is led to the first terminal. The second switching element is disposed on a path connecting a first node to a second power node, and the second power node is led to the second terminal. The third switching element is disposed on a path connecting a first power node to a second node, and the fourth switching element is disposed on a path connecting two second nodes to two power nodes. The transformer has a first winding and a second winding. The first winding has a first terminal connected to a first node and a second terminal connected to a second node. The rectifier section is connected to the second winding and has multiple switching elements. The second power terminal is led to the rectifier section. The control section controls the operation of the first switching element, the second switching element, the third switching element, the fourth switching element, and the multiple switching elements. The aforementioned control unit controls the operation of the switching unit and the rectifier unit during a predetermined period to supply power from the second power terminal to the first power terminal. This predetermined period differs from the period during which power is supplied from the first power terminal to the second power terminal. During the predetermined period, the control unit operates the switching unit with a first duty cycle and the rectifier unit with a second duty cycle. The first duty cycle is greater than 0 and less than or equal to the second duty cycle.

[0009] An embodiment of the power conversion system 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 disposed on a path connecting the first terminal of the first battery and the first terminal of the capacitor. The second switch is disposed on 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 conversion section, a transformer, a rectifier section, a second power terminal, and a control section. The first power terminal has a first terminal connected to the first terminal of the capacitor and a second terminal connected to the second terminal of the capacitor. The conversion section includes a first switch element, a second switch element, a third switch element, and a fourth switch element. The first switch element is disposed on a path connecting a first power node to a first node, with the first power node leading to the first terminal; the second switch element is disposed on a path connecting the first node to a second power node, with the second power node leading to the second terminal; the third switch element is disposed on a path connecting the first power node to the second node; and the fourth switch element is disposed on a path connecting the second node to the second power node. The transformer has a first winding and a second winding. The first winding has a first terminal connected to a first node and a second terminal connected to a second node. A rectifier section is connected to the second winding and has multiple switching elements. A second power terminal is led to the rectifier section and connected to a second battery. A control unit controls the operation of the first, second, third, and fourth switching elements and the multiple switching elements. The control unit controls the operation of the switching section and the rectifier section during a predetermined period to supply power from the second power terminal to the first power terminal. The predetermined period is different from the period during which power is supplied from the first power terminal to the second power terminal. During the predetermined period, the control unit operates the switching section with a first duty cycle and the rectifier section with a second duty cycle. The first duty cycle is greater than 0 and less than or equal to the second duty cycle.

[0010] According to one embodiment of the present invention, a power conversion device and a power conversion system can perform a pre-charging operation with a simple structure requiring few additional parts. Furthermore, the effects of the present invention are not limited to this, and may also include any of the effects described below. Attached Figure Description

[0011] Figure 1 This is a circuit diagram illustrating a structural example of a power conversion system according to one embodiment of the present invention.

[0012] Figure 2 It means Figure 1 A block diagram of a structural example of the control unit shown.

[0013] Figure 3 It means Figure 1 The timing diagram shows an example of an operation of a power conversion system.

[0014] Figure 4 It means Figure 1 The timing waveform diagram shows an example of an operation of the power conversion system.

[0015] Figure 5 It means Figure 1 Other timing waveforms of an example operation of the power conversion system shown.

[0016] Figure 6 It means Figure 1 Other timing waveforms of an example operation of the power conversion system shown.

[0017] Figure 7A It means Figure 1 The diagram illustrates one operating state of the power conversion system.

[0018] Figure 7B It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0019] Figure 7C It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0020] Figure 7D It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0021] Figure 7E It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0022] Figure 7F It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0023] Figure 7G It means Figure 1 The diagram illustrates other operating states of the power conversion system.

[0024] Figure 8 It means Figure 1 The flowchart shows an example of an operation of a power conversion system.

[0025] Figure 9 This is a flowchart illustrating an example of the operation of a modified power conversion system.

[0026] Figure 10 This is a timing diagram representing an example of the operation of a power conversion system with other variations.

[0027] Figure 11 This is a timing waveform diagram representing an example of an operation of a power conversion system with other variations.

[0028] Figure 12 This is a flowchart illustrating an example of an operation of a power conversion system with other variations.

[0029] Figure 13 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0030] Figure 14 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0031] Figure 15 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0032] Figure 16 It means Figure 15 A block diagram of a structural example of the control unit shown.

[0033] Figure 17 This is a block diagram representing a structural example of the control unit in other variations.

[0034] Figure 18 This is a block diagram representing a structural example of the control unit in other variations.

[0035] Figure 19 This is a block diagram representing a structural example of the control unit in other variations.

[0036] Figure 20 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0037] Figure 21 This is a circuit diagram illustrating a structural example of an active clamping circuit with other variations.

[0038] Figure 22 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0039] Figure 23 It means Figure 22 The timing waveform diagram shows an example of an operation of the power conversion system.

[0040] Figure 24 It means Figure 22 Other timing waveforms of an example operation of the power conversion system shown.

[0041] Figure 25 It means Figure 22 Other timing waveforms of an example operation of the power conversion system shown.

[0042] Figure 26A It means Figure 22 The diagram illustrates one operating state of the power conversion system.

[0043] Figure 26B It means Figure 22 The diagram illustrates other operating states of the power conversion system.

[0044] Figure 26C It means Figure 22 The diagram illustrates other operating states of the power conversion system.

[0045] Figure 26D It means Figure 22 The diagram illustrates other operating states of the power conversion system.

[0046] Figure 26E It means Figure 22 The diagram illustrates other operating states of the power conversion system.

[0047] Figure 26F It means Figure 22 The diagram illustrates other operating states of the power conversion system.

[0048] Figure 26G It means Figure 22 The diagram illustrates other operating states of the power conversion system.

[0049] Figure 26H It means Figure 22 The diagram illustrates other operating states of the power conversion system.

[0050] Figure 27 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0051] Figure 28 It means Figure 27 The flowchart shows an example of an operation of a power conversion system.

[0052] Figure 29 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0053] Figure 30 It means Figure 29 The timing waveform diagram shows an example of an operation of the power conversion system.

[0054] Figure 31A It means Figure 29 The diagram illustrates one operating state of the power conversion system.

[0055] Figure 31B It means Figure 29 The diagram illustrates one operating state of the power conversion system.

[0056] Figure 31C It means Figure 29 The diagram illustrates one operating state of the power conversion system.

[0057] Figure 31D It means Figure 29 The diagram illustrates one operating state of the power conversion system.

[0058] Figure 31E It means Figure 29 The diagram illustrates one operating state of the power conversion system.

[0059] Figure 32 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0060] Figure 33 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0061] Figure 34 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0062] Figure 35 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0063] Figure 36 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0064] Figure 37 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0065] Figure 38 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0066] Figure 39 This is a circuit diagram representing a structural example of a power conversion system with other variations.

[0067] Symbol Explanation

[0068] 1. 1A, 1B, 1C, 1G, 1H, 1I, 1J, 1K, 2. 2A, 2B, 2C, 2G, 2H, 2J Power Conversion System

[0069] 9. Capacitors

[0070] 10, 10A, 10B, 10C, 10G, 10H, 10I, 10J, 10K, 30, 30A, 30B, 30C, 30G, 30H, 30J Power Conversion Devices

[0071] 11C Current Sensor

[0072] 12 Voltage Sensors

[0073] 13. Conversion Section

[0074] Transformers 14 and 34

[0075] 14A, 14B, 34A~34C windings

[0076] 15, 15G, 35, 35G Rectifier Section

[0077] 16 Choke Inductor

[0078] 17 Capacitors

[0079] 18 Voltage Sensor

[0080] Control Units 19, 19C, 19D, 19E, 19F, 19I, 19K, 39, 39C

[0081] 21, 21C, 21D, 21E, 21F Pre-charge Control Unit

[0082] 22 Target Value Determination Department

[0083] Duty cycle generation section 23, 23D, 23F, 24, 24C, 24E

[0084] 25 Power Conversion Control Department

[0085] 25C Average Current Calculation Section

[0086] 26, 27 Gate signal generation section

[0087] 26C, 26E Reference Level Generation Unit

[0088] 27C, 27E Error Signal Amplifier

[0089] 31 Choke Transformer

[0090] 31A and 31B windings

[0091] Smooth sections 41, 41H, 41J

[0092] 90 Active clamping circuit

[0093] AVA Avalanche Breakdown Status

[0094] BH High Voltage Battery

[0095] BL low-voltage battery

[0096] DP and DS duty cycles

[0097] DZ, DZ1, DZ2 Zener diodes

[0098] D1~D10 Body Diodes

[0099] Diodes D11, D12, and D13

[0100] GA~GF gate signals

[0101] IH current

[0102] L11, L21A, L21B voltage lines

[0103] L12, L22 reference voltage lines

[0104] Lr resonant inductor

[0105] N1 to N7 nodes

[0106] P1 precharge period

[0107] P2 Power Conversion Period

[0108] R1 resistor element

[0109] SW switch

[0110] SW1 and SW2 switches

[0111] S1~S10 transistors

[0112] TR transistor

[0113] T11, T12, T21, T22 terminals

[0114] VH, VL voltages

[0115] VH_target target voltage

[0116] Vth threshold Detailed Implementation

[0117] The embodiments for carrying out the present invention will now be described in detail with reference to the accompanying drawings. All embodiments described below represent preferred examples of the present invention. Therefore, the numerical values, shapes, materials, constituent elements, arrangement positions of constituent elements, and connection methods shown in the following embodiments are merely examples and are not intended to limit the present invention. Therefore, constituent elements in the following embodiments that are not described in the independent claims representing the superior concept of the present invention are described as arbitrary constituent elements. Furthermore, the accompanying drawings are merely schematic diagrams and are not necessarily precise. Additionally, in the various drawings, substantially identical structures are given the same reference numerals, and repeated descriptions are omitted or simplified.

[0118] <Implementation Method>

[0119] [Structure Example]

[0120] Figure 1 This is a structural example of a power conversion system 1 incorporating a power conversion device according to one 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 by the high-voltage battery BH and provide the converted power to the low-voltage battery BL.

[0121] The high-voltage battery BH stores electricity. The high-voltage battery BH supplies electricity to the power conversion device 10 through switches SW1 and SW2.

[0122] Switches SW1 and SW2, when in the ON state, supply power stored in the high-voltage battery BH to the power conversion device 10. Switches SW1 and SW2 are constructed, for example, using relays. Switch SW1, when in the ON state, connects the positive terminal of the high-voltage battery BH to terminal T11 of the power conversion device 10. Switch SW2, when in the ON state, connects the negative terminal of the high-voltage battery BH to terminal T12 of the power conversion device 10. Switches SW1 and SW2 are turned on or off according to instructions from a system control unit (not shown).

[0123] One end of capacitor 9 is connected to terminal T11 of power conversion device 10 and switch SW1, and the other end is connected to terminal T12 of power conversion device 10 and switch SW2.

[0124] The power conversion device 10 is configured to convert the voltage supplied by the high-voltage battery BH into electrical power, and then supply the converted power to the low-voltage battery BL. The power conversion device 10 includes terminals T11, T12, a voltage sensor 12, a conversion unit 13, a transformer 14, a rectifier 15, a smoothing unit 41, a voltage sensor 18, a control unit 19, and terminals T21, T22. The high-voltage battery BH, switches SW1, SW2, capacitor 9, voltage sensor 12, and conversion unit 13 constitute the primary circuit of the power conversion system 1, while the rectifier 15, smoothing unit 41, voltage sensor 18, and low-voltage battery BL constitute the secondary circuit of the power conversion system 1.

[0125] Terminals T11 and T12 are switched on via switches SW1 and SW2, supplying voltage from the high-voltage battery BH. Within the power conversion device 10, terminal T11 is connected to voltage line L11, and terminal T12 is connected to reference voltage line L12.

[0126] Voltage sensor 12 detects the voltage on voltage line L11. One end of voltage sensor 12 is connected to voltage line L11, and the other end is connected to reference voltage line L12. Voltage sensor 12 detects the voltage on voltage line L11, which is referenced to the voltage on reference voltage line L12, and takes this as voltage VH. Furthermore, voltage sensor 12 provides the detection result of voltage VH to control unit 19.

[0127] The conversion unit 13 converts the DC voltage supplied by the high-voltage battery BH into AC voltage. The conversion unit 13 is a full-bridge circuit and includes transistors S1 to S4. Transistors S1 to S4 are switching elements that switch according to gate signals GA to GD, respectively. Transistors S1 to S4 are, for example, constructed using N-type field-effect transistors (FETs). Transistors S1 to S4 each have body diodes D1 to D4. For example, the anode of body diode D1 is connected to the source of transistor S1, and the cathode is connected to the drain of transistor S1. The same applies to body diodes D2 to D4. Furthermore, although N-type field-effect transistors are used in this example, any switching element can be used.

[0128] Transistor S1 is positioned on the path connecting voltage line L11 and node N1, and is turned on, connecting node N1 to voltage line L11. The drain of transistor S1 is connected to voltage line L11, its gate is supplied with a gate signal GA, and its source is connected to node N1. Transistor S2 is positioned on the path connecting node N1 and reference voltage line L12, and is turned on, connecting node N1 to reference voltage line L12. The drain of transistor S2 is connected to node N1, its gate is supplied with a gate signal GB, and its source is connected to reference voltage line L12. Node N1 is the connection point between the source of transistor S1 and the drain of transistor S2.

[0129] Transistor S3 is positioned on the path connecting voltage line L11 and node N2, and is turned on, connecting node N2 to voltage line L11. The drain of transistor S3 is connected to voltage line L11, its gate is supplied with a gate signal GC, and its source is connected to node N2. Transistor S4 is positioned on the path connecting node N2 and reference voltage line L12, and is turned on, connecting node N2 to reference voltage line L12. The drain of transistor S4 is connected to node N2, its gate is supplied with a gate signal GD, and its source is connected to reference voltage line L12. Node N2 is the connection point between the source of transistor S3 and the drain of transistor S4.

[0130] Transformer 14 DC-isolates and AC-couples the primary and secondary circuits, and converts the AC voltage supplied from the primary circuit using its transformation ratio N, then provides the converted AC voltage to the secondary circuit. Transformer 14 has windings 14A and 14B. One end of winding 14A is connected to node N1 of the conversion section 13, and the other end is connected to node N2 of the conversion section 13. One end of winding 14B is connected to node N4 (described later) of the rectifier section 15, and the other end is connected to node N5 (described later) of the rectifier section 15.

[0131] The rectifier section 15 generates an output voltage by rectifying the AC voltage output from the winding 14B of the transformer 14. The rectifier section 15 is a full-bridge circuit and includes transistors S5 to S8. Transistors S5 to S8 switch according to gate signals GE and GF. Transistors S5 to S8 are similar to transistors S1 to S4 in the switching section 13, for example, constructed using N-type field-effect transistors. Like transistors S1 to S4, transistors S5 to S8 each have body diodes D5 to D8.

[0132] Transistor S5 is positioned on the path connecting voltage line L21A and node N4, and node N4 is connected to voltage line L21A by being turned on. The drain of transistor S5 is connected to voltage line L21A, its gate is supplied with a gate signal GF, and its source is connected to node N4. Transistor S6 is positioned on the path connecting node N4 and reference voltage line L22, and node N4 is connected to reference voltage line L22 by being turned on. The drain of transistor S6 is connected to node N4, its gate is supplied with a gate signal GE, and its source is connected to reference voltage line L22. Node N4 is the connection point between the source of transistor S5 and the drain of transistor S6.

[0133] Transistor S7 is positioned on the path connecting voltage line L21A and node N5, and node N5 is connected to voltage line L21A by being turned on. The drain of transistor S7 is connected to voltage line L21A, its gate is supplied with a gate signal GE, and its source is connected to node N5. Transistor S8 is positioned on the path connecting node N5 and reference voltage line L22, and node N5 is connected to reference voltage line L22 by being turned on. The drain of transistor S8 is connected to node N5, its gate is supplied with a gate signal GF, and its source is connected to reference voltage line L22. Node N5 is the connection point between the source of transistor S7 and the drain of transistor S8.

[0134] The smoothing section 41 smooths the output voltage of the rectifier section 15. The smoothing section 41 includes a choke inductor 16 and a capacitor 17. One end of the choke inductor 16 is connected to voltage line L21A, and the other end is connected to voltage line L21B. One end of the capacitor 17 is connected to voltage line L21B, and the other end is connected to the reference voltage line L22. Furthermore, although the choke inductor 16 is provided on voltage lines L21A and L21B in this example, it is not a limitation; alternatively, the choke inductor 16 may be provided on the reference voltage line L22.

[0135] Voltage sensor 18 detects the voltage on voltage line L21B. One end of voltage sensor 18 is connected to voltage line L21B, and the other end is connected to reference voltage line L22. Voltage sensor 18 detects the voltage on voltage line L21B, which is referenced to the voltage on reference voltage line L22, and takes this as voltage VL. Furthermore, voltage sensor 18 provides the detection result of voltage VL to control unit 19.

[0136] The control unit 19 is configured to control the operation of the conversion unit 13 and the rectifier unit 15 based on the voltage VH detected by the voltage sensor 12 and the voltage VL detected by the voltage sensor 18, thereby controlling the operation of the power conversion device 10. Specifically, the control unit 19 generates gate signals GA to GF based on the voltages VH and VL, and performs PWM (Pulse Width Modulation) control through these gate signals GA to GF, thereby controlling the operation of the power conversion device 10.

[0137] Terminals T21 and T22 supply the voltage generated by the power conversion device 10 to the low-voltage battery BL. Within the power conversion device 10, terminal T21 is connected to voltage line L21B, and terminal T22 is connected to reference voltage line L22. Additionally, terminal T21 is connected to the positive terminal of the low-voltage battery BL, and terminal T22 is connected to the negative terminal of the low-voltage battery BL.

[0138] The low-voltage battery BL stores the power supplied from the power conversion device 10.

[0139] In the power conversion system 1, the structure performs the following power conversion operation: converting the power supplied by the high-voltage battery BH and providing the converted power to the low-voltage battery BL.

[0140] Furthermore, the power conversion system 1 also has the following function: during the preparation period (pre-charging period P1) before starting such a power conversion operation, the capacitor 9 is charged, performing a so-called pre-charging operation. During this pre-charging operation, switches SW1 and SW2 are turned off, and the control unit 19 controls the operation of the conversion unit 13 and the rectifier unit 15, thereby the power conversion system 1 supplies power from the low-voltage battery BL to the capacitor 9. Therefore, in the power conversion device 10, when switches SW1 and SW2 are turned on to perform the power conversion operation, the surge current flowing from the high-voltage battery BH into the capacitor 9 can be suppressed.

[0141] Figure 2 This illustrates a structural example of the control unit 19. The control unit 19 includes a pre-charge control unit 21, a power conversion control unit 25, and gate signal generation units 26 and 27.

[0142] During the pre-charging period P1, the pre-charge control unit 21 generates the duty cycle DP of the conversion operation of the conversion unit 13 and the duty cycle DS of the conversion operation of the rectifier unit 15 based on the voltages VH and VL. The pre-charge control unit 21 includes a target value determination unit 22 and duty cycle generation units 23 and 24.

[0143] During the pre-charging period P1, the target value determination unit 22 determines whether the voltage VH exceeds the target voltage VH_target. Furthermore, the target value determination unit 22 provides the determination result to the duty cycle generation units 23 and 24.

[0144] During the pre-charge period P1, the duty cycle generation unit 23 generates the duty cycle DP of the conversion unit 13 based on the voltage VL. Specifically, the duty cycle generation unit 23 generates the duty cycle DP in such a way that the higher the voltage VL, the lower the duty cycle DP. The duty cycle generation unit 23 can generate the duty cycle DP based on the voltage VL using, for example, the formula "DP = X1 / VL". Here, "X1" is an arbitrary constant. Alternatively, the duty cycle generation unit 23 can also generate the duty cycle DP based on the voltage VL using, for example, a list of data showing the relationship between the duty cycle DP and the voltage VL. During the pre-charge period P1, the duty cycle generation unit 23 generates the duty cycle DP in a way that gradually increases. As a result, the current stress in the circuit can be reduced in the power conversion system 1. Furthermore, if the target value determination unit 22 determines that the voltage VH exceeds the target voltage VH_target, then the duty cycle generation unit 23 determines that the pre-charge period P1 has ended, thereby ending the generation of the duty cycle DP.

[0145] During the pre-charge period P1, the duty cycle generation unit 24 generates the duty cycle DS of the rectifier unit 15 based on the voltage VL. Specifically, the duty cycle generation unit 24 generates the duty cycle DS in such a way that the higher the voltage VL, the lower the duty cycle DS. The duty cycle generation unit 24 can use, for example, the formula "DS = X2 / VL" to generate the duty cycle DS based on the voltage VL. Here, "X2" is an arbitrary constant. Alternatively, the duty cycle generation unit 24 can also use, for example, a list of data showing the relationship between the duty cycle DS and the voltage VL to generate the duty cycle DS based on the voltage VL. During the pre-charge period P1, the duty cycle generation unit 24 generates the duty cycle DS in a way that gradually increases the duty cycle DS. As a result, the current stress in the circuit can be reduced in the power conversion system 1. Furthermore, if the target value determination unit 22 determines that the voltage VH exceeds the target voltage VH_target, then the duty cycle generation unit 24 determines that the pre-charge period P1 has ended, thereby ending the generation of the duty cycle DS.

[0146] When generating duty cycles DP and DS, the duty cycle generation units 23 and 24 generate the duty cycles DP and DS in a manner that satisfies the following formulas EQ1 and EQ2.

[0147] 0 < DS ≤ 0.5……(EQ1)

[0148] 0 < DP ≤ DS……(EQ2)

[0149] In other words, the duty cycle DS of the rectifier 15 is controlled to be greater than 0 and less than or equal to 0.5. Furthermore, the duty cycle DP of the converter 13 is controlled to be greater than 0 and less than or equal to the duty cycle DS of the rectifier 15. Duty cycle generating units 23 and 24 generate such duty cycles DP and DS.

[0150] During the power conversion operation (power conversion period P2), the power conversion control unit 25 generates the duty cycle DP of the conversion operation of the conversion unit 13 and the duty cycle DS of the conversion operation of the rectifier unit 15 based on the voltages VH and VL.

[0151] The gate signal generation unit 26 generates gate signals GA to GD based on the duty cycle DP generated by the duty cycle generation unit 23 and the power conversion control unit 25. Specifically, during the pre-charge period P1, in this example, the gate signal generation unit 26 generates gate signals GC and GD based on the duty cycle DP generated by the duty cycle generation unit 23, and maintains the gate signals GA and GB at a low level. Furthermore, during the power conversion period P2, the gate signal generation unit 26 generates gate signals GA to GD based on the duty cycle DP generated by the power conversion control unit 25.

[0152] The gate signal generation unit 27 generates gate signals GE,GF based on the duty cycle DS data supplied from the duty cycle generation unit 24 and the power conversion control unit 25. Specifically, during the pre-charge period P1, in this example, the gate signal generation unit 27 generates the gate signals GE,GF based on the duty cycle DS generated by the duty cycle generation unit 23. Furthermore, during the power conversion period P2, the gate signal generation unit 27 generates the gate signals GE,GF based on the duty cycle DS generated by the power conversion control unit 25.

[0153] Here, terminals T11 and T12 correspond to a specific example of the "first power terminal" of this disclosure. Terminal T11 corresponds to a specific example of the "first wiring terminal" of this disclosure. Terminal T12 corresponds to a specific example of the "second wiring terminal" of this disclosure. Switching unit 13 corresponds to a specific example of the "switching unit" of this disclosure. Voltage line L11 corresponds to a specific example of the "first power node" of this disclosure. Reference voltage line L12 corresponds to a specific example of the "second power node" of this disclosure. Node N1 corresponds to a specific example of the "first node" of this disclosure. Node N2 corresponds to a specific example of the "second node" of this disclosure. Transistor S1 corresponds to a specific example of the "first switching element" of this disclosure. Transistor S2 corresponds to a specific example of the "second switching element" of this disclosure. Transistor S3 corresponds to a specific example of the "third switching element" of this disclosure. Transistor S4 corresponds to a specific example of the "fourth switching element" of this disclosure. Transformer 14 corresponds to a specific example of the "transformer" of this disclosure. Winding 14A corresponds to a specific example of the "first winding" of this disclosure. Winding 14B corresponds to a specific example of the "second winding" of this disclosure. Rectifier 15 corresponds to a specific example of the "rectifier section" of this disclosure. Voltage line L21A corresponds to a specific example of the "third power node" of this disclosure. Reference voltage line L22 corresponds to a specific example of the "fourth power node" of this disclosure. Node N4 corresponds to a specific example of the "fourth node" of this disclosure. Node N5 corresponds to a specific example of the "fifth node" of this disclosure. Transistor S5 corresponds to a specific example of the "fifth switching element" of this disclosure. Transistor S6 corresponds to a specific example of the "sixth switching element" of this disclosure. Transistor S7 corresponds to a specific example of the "seventh switching element" of this disclosure. Transistor S8 corresponds to a specific example of the "eighth switching element" of this disclosure. Terminals T21 and T22 correspond to a specific example of the "second power terminal" of this disclosure. Terminal T21 corresponds to a specific example of the "third terminal" of this disclosure. Terminal T22 corresponds to a specific example of the "fourth terminal" of this disclosure. Control unit 19 corresponds to a specific example of the "control unit" of this disclosure. Duty cycle DP corresponds to a specific example of the "first duty cycle" of this disclosure. Duty cycle DS corresponds to a specific example of the "second duty cycle" of this disclosure. Precharge period P1 corresponds to a specific example of the "determined period" of this disclosure.

[0154] [Actions and Functions]

[0155] Next, the operation and function of the power conversion system 1 in this embodiment will be explained.

[0156] (Overall Action Summary)

[0157] First, refer to Figure 1 2. A general overview of the operation of the power conversion system 1 is provided. During pre-charging (P1), switches SW1 and SW2 are turned off. The control unit 19 generates gate signals GC to GF based on voltages VH and VL and maintains gate signals GA and GB at a low level. Consequently, the conversion unit 13 and the rectifier unit 15 operate, and the power conversion device 10 supplies power from the low-voltage battery BL to the capacitor 9. As a result, the capacitor 9 is charged, and the voltage VH rises. If the voltage VH exceeds the target voltage VH_target, the pre-charging operation ends, switches SW1 and SW2 are turned on, and the control unit 19 generates gate signals GA to GF based on voltages VH and VL. Thus, the power conversion device 10 converts the power supplied by the high-voltage battery BH and supplies the converted power to the low-voltage battery BL.

[0158] (Detailed actions)

[0159] Figure 3 This is an example of a pre-charge operation. In this example, the pre-charge control unit 21 generates a duty cycle DP,DS that gradually increases during the period from time t1 to t2 (pre-charge period P1). The pre-charge control unit 21 generates the duty cycle DP,DS as shown in equations EQ1 and EQ2, such that the duty cycle DS is greater than 0 and less than or equal to 0.5, and the duty cycle DP is greater than 0 and less than or equal to the duty cycle DS. Then, the gate signal generation unit 26 generates gate signals GC,GD based on the duty cycle DP, and maintains the gate signals GA,GB at a low level. The conversion unit 13 performs a conversion operation based on the gate signals GA to GD. The gate signal generation unit 27 generates gate signals GE,GF based on the duty cycle DS. The rectifier unit 15 performs a conversion operation based on the gate signals GE,GF. Therefore, after time t1, at the beginning of the pre-charge period P1, the voltage VH of capacitor 9 gradually increases.

[0160] Figure 4 Examples of simulated waveforms representing the pre-charge operation: (A) represents the waveforms of gate signals GE and GF; (B) represents the waveforms of gate signals GC and GD; (C) represents the waveform of the current flowing into capacitor 9 (charging current ICHG); (D) represents the waveform of the magnetizing current IM of transformer 14; (E) represents the waveform of the current flowing from voltage line L21B to voltage line L21A in choke inductor 16 (inductor current IL); (F) represents the waveform of the voltage at node N4 of winding 14B of transformer 14, with node N5 as the reference (transformer voltage VTR2); and (G) represents the waveform of voltage VH. Figure 4 In this context, T represents the cycle of the switching action.

[0161] During the pre-charge operation, the control unit 19 generates gate signals GC and GD based on the duty cycle DP, and gate signals GE and GF based on the duty cycle DS. The duty cycle DP represents the pulse width of each of the gate signals GC and GD when the period T (time points t11 to t13) is taken as "1", and the duty cycle DS represents the pulse width of each of the gate signals GE and GF when the period T is taken as "1". The control unit 19... Figure 4 As shown in (A) and (B), at time t11, the gate signals GC and GF are changed from low to high. Furthermore, the control unit 19 changes the gate signal GC from high to low at a time corresponding to the duty cycle DP (duty cycle DP × period T) after time t11, and changes the gate signal GF from high to low at a time corresponding to the duty cycle DS (duty cycle DS × period T) after time t11. Next, at time t12, the control unit 19 changes the gate signals GD and GE from low to high. Furthermore, the control unit 19 changes the gate signal GD from high to low at a time corresponding to the duty cycle DP (duty cycle DP × period T) after time t12, and changes the gate signal GE from high to low at a time corresponding to the duty cycle DS (duty cycle DS × period T) after time t12. The control unit 19 maintains the gate signals GA and GB at low levels, which are not shown in the figure. Furthermore, in power conversion system 1, the operation at time points t11 to t13 is repeatedly performed while changing the duty cycle DP,DS, thereby charging capacitor 9. Thus, as... Figure 4 As shown in (G), the voltage VH gradually increases.

[0162] The following section details the operations based on gate signals GC and GF during the period from time t11 to t12. Similarly, the operations based on gate signals GD and GE during the period from time t12 to t13 are also described in detail.

[0163] Figure 5 6. More detailed representation of the operation during the period from time t11 to t12: (A) represents the waveforms of gate signals GE and GF; (B) represents the waveforms of gate signals GC and GD; (C) represents the waveform of the current flowing into capacitor 9 (charging current ICHG); (D) represents the waveform of the excitation current IM of transformer 14; (E) represents the waveform of the current flowing from voltage line L21B to voltage line L21A in choke inductor 16 (inductor current IL); (F) represents the waveform of the voltage at node N1 of winding 14A of transformer 14, with node N2 as the reference (transformer voltage VTR1); (G) represents the waveform of the voltage at node N4 of winding 14B of transformer 14, with node N5 as the reference (transformer voltage VTR2); (H) represents the waveform of voltage VH. For example... Figure 5As shown, power conversion system 1 can have seven operating states ST1 to ST7 during the period from time t11 to t12. The operating states ST of power conversion system 1 change in the order of operating state ST1, operating state ST2, operating state ST3...operating state ST7. Operating states ST3 and ST4 are operating states during minute periods. Figure 6 In the diagram, magnification represents the actions corresponding to the periods of ST3 and ST4 and the periods surrounding them.

[0164] Figures 7A-7G This indicates the operation of power conversion system 1 in seven operating states, ST1 to ST7. Figures 7A-7G For ease of explanation, the power conversion system 1 is described more simply.

[0165] In operating state ST1, control unit 19 sets gate signals GC and GF to high level and gate signals GA, GB, GD, and GE to low level. Figure 5 (A), (B)). Therefore, transistors S3, S5, and S8 are in the ON state, and transistors S1, S2, S4, S6, and S7 are in the OFF state. Figure 7A In the secondary circuit, current I2 flows sequentially through the positive terminal of the low-voltage battery BL, choke inductor 16, transistor S5 (on), winding 14B, transistor S8 (on), and the negative terminal of the low-voltage battery BL, accumulating energy in choke inductor 16. In the primary circuit, the body diode D1 of transistor S1 is on, and current I1 flows sequentially through one end of winding 14A (node ​​N1), the body diode D1 of transistor S1, transistor S3 (on), and the other end of winding 14A (node ​​N2), accumulating energy in the leakage inductor LLK of transformer 14. At this time, from the secondary circuit perspective, the primary circuit is approximately short-circuited. Therefore, the transformer voltages VTR1 and VTR2 are approximately 0V. Figure 5 (F),(G)).

[0166] In the next operating state ST2, the control unit 19 changes the gate signal GC from high level to low level. Figure 5 (B)). Therefore, transistor S3 changes from the on state to the off state. Figure 7B In the primary circuit, the body diode D4 of transistor S4 is turned on, and the current I1 flows sequentially through one end of winding 14A (node ​​N1), the body diode D1 of transistor S1, capacitor 9, the body diode D4 of transistor S4, and the other end of winding 14A (node ​​N2). The charging current ICHG flows ( Figure 5 (C)). That is to say, the energy stored in the leakage inductor LLK of transformer 14 is released and stored in capacitor 9. Thus, the voltage VH rises ( Figure 5 (H)). In the secondary circuit, the transformer voltage VTR2 becomes a positive voltage ( Figure 5 (G)), the excitation current IM begins to flow in transformer 14. Figure 5 (D)). When the voltage VH has not risen sufficiently and satisfies the following equation EQ3, the power conversion system 1 performs a voltage reduction operation. When the voltage VH has risen sufficiently and satisfies the following equation EQ4, the power conversion system 1 performs a voltage boost operation.

[0167] VH<N×VL……(EQ3)

[0168] VH≥N×VL……(EQ4)

[0169] Here, N is the transformation ratio of transformer 14, which can be expressed by the following formula EQ5 using the number of turns Np of the primary winding (winding 14A) and the number of turns Ns of the secondary winding (winding 14B) of transformer 14.

[0170] N = Np / Ns……(EQ5)

[0171] In this operating state ST2, when the power conversion system 1 is performing a step-down operation, the inductor current IL increases with a positive slope over time; when the power conversion system 1 is performing a step-up operation, the inductor current IL decreases with a negative slope over time. In this example, because the power conversion system 1 is performing a step-up operation, the inductor current IL decreases ( Figure 5 (E)).

[0172] In the next minute period of operation, ST3, the control unit 19 changes the gate signal GF from high level to low level. Figure 5 (A), 6(A)). Therefore, transistors S5 and S8 change from the on state to the off state. Figure 7C In the secondary circuit, a reverse voltage is generated in the choke inductor 16, increasing the drain-source voltage of each of transistors S5-S8 and reaching the breakdown voltage of avalanche breakdown. As a result, avalanche current flows in each of transistors S5-S8, and each of transistors S5-S8 enters the avalanche breakdown state AVA. Furthermore, the energy stored in the choke inductor 16 is released, and the inductor current IL decreases. Figure 5 (E),6(E)). In this way, transistors S5 to S8 each become avalanche breakdown state AVA, and the transformer voltage VTR2 is approximately 0V. Figure 5(G),6(G)). In the primary circuit, continuing from the previous operating state ST2, the current I1 flows sequentially through one end of winding 14A (node ​​N1), the body diode D1 of transistor S1, capacitor 9, the body diode D4 of transistor S4, and the other end of winding 14A (node ​​N2). In the transformer voltage VTR1, the reverse voltage of the leakage inductor LLK of transformer 14 is presented.

[0173] In the next minute period of operation, state ST4, the energy stored in the leakage inductor LLK of transformer 14 in the primary circuit is released, and the body diodes D1 and D4 of transistor S1 and S4 become off. Figure 7D In this way, no current flows through the converter 13 in the primary circuit, and the charging current ICHG becomes 0A. Figure 5 (C), 6(C)). In the secondary side circuit, transistors S5 to S8 each maintain an avalanche breakdown state of AVA. The avalanche current flowing through transistor S5 is greater than the magnetizing current IM by the same amount as the avalanche current flowing through transistor S6. Similarly, the avalanche current flowing through transistor S8 is greater than the magnetizing current IM by the same amount as the avalanche current flowing through transistor S7. Therefore, the avalanche currents flowing through transistors S6 and S7 approach 0A faster than the avalanche currents flowing through transistors S5 and S8.

[0174] In the next operating state ST5, the avalanche current flowing through transistors S6 and S7 reaches 0A, and the avalanche breakdown state AVA of transistors S6 and S7 is released. Figure 7E Transistors S5 and S8 remain in avalanche breakdown state AVA. Therefore, transformer voltages VTR1 and VTR2 become negative voltages. Figure 5 (F), (G)). The result is that in the primary circuit, the body diodes D2 and D3 of transistor S2 and S3 are turned on, and the current I1 flows sequentially through the other end of winding 14A (node ​​N2), the body diode D3 of transistor S3, capacitor 9, the body diode D2 of transistor S2, and one end of winding 14A (node ​​N1), while the charging current ICHG flows ( Figure 5 (C)). That is to say, the energy stored in the magnetizing inductor LM of transformer 14 is released and stored in capacitor 9. Thus, the voltage VH rises ( Figure 5 (H)).

[0175] In the next operating state ST6, the energy stored in the choke inductor 16 in the secondary side circuit is released, and the avalanche breakdown state AVA of transistors S5 and S8 is released. Figure 7FTherefore, no current flows through the rectifier section 15 in the secondary circuit. In the primary circuit, the previous operating state ST5 continues, and the current I1 flows sequentially through the other end of winding 14A (node ​​N2), the body diode D3 of transistor S3, capacitor 9, the body diode D2 of transistor S2, and one end of winding 14A (node ​​N1). That is, the energy stored in the magnetizing inductor LM of transformer 14 is released and stored in capacitor 9. Thus, the voltage VH rises ( Figure 5 (H)).

[0176] In the next operating state ST7, the energy stored in the magnetizing inductor LM of transformer 14 in the primary circuit is released, and the body diodes D2 and D3 of transistor S2 and S3 become off. Figure 7G Therefore, no current flows through the switching unit 13 in the primary circuit. In other words, in this operating state ST7, no current flows through either the primary or secondary circuits.

[0177] Thus, during the period from time t11 to t12, capacitor 9 is charged, and voltage VH rises. The same applies to the period from time t12 to t13. Furthermore, the above operation is just one example. If, for example, the duty cycle DS rises close to "0.5", then, for example, operating state ST7 out of operating states ST1 to ST7 may disappear. In power conversion system 1, as... Figure 4 As shown, by repeatedly performing this action at time points t11 to t13, capacitor 9 is gradually charged, and voltage VH gradually increases.

[0178] And, as Figure 3 As shown, if the voltage VH exceeds the target voltage VH_target at time t2, the pre-charge control unit 21 ends the generation of the duty cycle DP,DS. Thus, the pre-charge operation ends. Furthermore, after switches SW1 and SW2 are turned on, the power conversion operation begins. However, while the power conversion system 1 starts the power conversion operation immediately after the pre-charge operation ends at time t2, it is not limited to this. For example, the power conversion system 1 could also perform a voltage maintenance operation after the pre-charge operation ends, maintaining the voltage VH near the target voltage VH_target by generating the duty cycle DP,DS, and then perform the power conversion operation.

[0179] The pre-charging operation described above is controlled by the pre-charging control unit 21 of the control unit 19. Next, an example of the operation of the pre-charging control unit 21 will be described.

[0180] Figure 8This describes an example of an operation of the pre-charge control unit 21. When switches SW1 and SW2 are set to the off state, the pre-charge control unit 21 performs the following operations.

[0181] First, the duty cycle generation units 23 and 24 of the pre-charge control unit 21 set the sequence of duty cycles DP and DS of P1 during the pre-charge period based on the voltage VL (step S101). Specifically, the duty cycle generation unit 23, as shown in the figure... Figure 3 As shown, during the pre-charge period P1, the duty cycle DP is generated by gradually increasing the duty cycle DP. The duty cycle generation unit 24 is as follows... Figure 3 As shown, during the pre-charge period P1, the duty cycle DS is generated by gradually increasing the duty cycle DS. The duty cycle generation units 23 and 24 generate the duty cycles DP and DS as shown in equations EQ1 and EQ2, so that the duty cycle DS is greater than 0 and less than or equal to 0.5, and the duty cycle DP is greater than 0 and less than or equal to the duty cycle DS.

[0182] Next, the control unit 19 starts PWM control according to the sequence set in step S101 (step S102). Specifically, the control unit 19 generates gate signals GC to GF according to the sequence set in step S101, and maintains gate signals GA and GB at a low level. Thus, in the power conversion system 1, as... Figures 4-6 As shown, PWM control is applied, capacitor 9 is gradually charged, and voltage VH gradually increases.

[0183] Next, the target value determination unit 22 determines whether the voltage VH exceeds the target voltage VH_target (step S103). If the voltage VH does not exceed the target voltage VH_target (N in step S103), then the process of step S103 is repeated until the voltage VH exceeds the target voltage VH_target.

[0184] If the voltage VH exceeds the target voltage VH_target (Y in step S103), then the control unit 19 ends the PWM control (step S104).

[0185] Thus, the pre-charging operation ends. Afterwards, switches SW1 and SW2 are turned on, and the power conversion device 10 begins the following power conversion operation: converting the power supplied by the high-voltage battery BH and providing the converted power to the low-voltage battery BL.

[0186] In this way, in the power conversion system 1, because the operation of the conversion unit 13 and the rectifier unit 15 is controlled during the pre-charging period P1, before power is supplied from the first power terminal (terminal T11, T12) to the second power terminal (terminal T21, T22), so that power is supplied from the second power terminal (terminal T21, T22) to the first power terminal (terminal T11, T12), the pre-charging operation can be performed with a simple structure. That is, for example, in the technology described in Patent Document 1, the conversion operation of the secondary circuit is controlled according to the current value of the choke coil during the pre-charging operation. In this case, a current sensor that detects the current flowing through the choke coil is required. On the other hand, in the power conversion system 1 of this embodiment, the operation of the conversion unit 13 and the rectifier unit 15 is controlled during the pre-charging period P1. For example, the operation of the conversion unit 13 and the rectifier unit 15 can be controlled so that the duty cycle DS is greater than 0 and less than or equal to 0.5, and the duty cycle DP is greater than 0 and less than or equal to the duty cycle DS. Therefore, in the power conversion system 1, since the current sensor can be omitted, the pre-charging operation can be performed with a simple structure.

[0187] [Effect]

[0188] As described above in this embodiment, since the operation of the conversion unit and the rectifier unit is controlled during the preparation period before power is supplied from the first power terminal to the second power terminal, i.e., the pre-charging period, so as to supply power from the second power terminal to the first power terminal, the pre-charging operation can be performed with a simple structure.

[0189] [Variation Example 1]

[0190] In the above embodiment, during the pre-charging period P1, although the operation of transistors S3 and S4 among the four transistors S1 to S4 of the switching unit 13 is controlled, it is not limited to this. As an alternative, for example, the operation of transistors S1 and S2 can be controlled, or the operation of transistors S1 and S3 can be controlled, or the operation of transistors S2 and S4 can be controlled.

[0191] [Variation Example 2]

[0192] In the above embodiments, such as Figure 8 As shown, although the sequence of duty cycles DP and DS of P1 during the pre-charging period is preset when the pre-charging operation begins, it is not limited to this. The power conversion system 1 of this modified example will be described in detail below.

[0193] Figure 9 This represents an example of an operation of the pre-charge control unit 21 in this modified example.

[0194] First, the duty cycle generation units 23 and 24 of the pre-charge control unit 21 set the sequence of duty cycles DP and DS of P1 during the pre-charge period according to the voltage VL (step S101).

[0195] Next, the control unit 19 starts PWM control according to the sequence set in step S101 (step S102). As a result, PWM control is performed in the power conversion system 1, the capacitor 9 is gradually charged, and the voltage VH gradually increases.

[0196] Next, the target value determination unit 22 determines whether the voltage VH exceeds the target voltage VH_target (step S103).

[0197] If the voltage VH does not exceed the target voltage VH_target ("N" in step S103), then the duty cycle generation units 23 and 24 confirm whether the voltage VL has changed by a predetermined amount or more from the initial voltage VL in step S101 (step S113). If the voltage VL has not changed by a predetermined amount or more ("N" in step S113), then the process returns to step S103.

[0198] In step S113, if the voltage VL changes by a predetermined amount or more (represented by "Y" in step S113), the duty cycle generation units 23 and 24 re-set the sequence of duty cycles DP and DS based on the voltage VL (step S114). Furthermore, the control unit 19 performs PWM control based on the sequence re-set in step S114 (step S115). In other words, if the voltage VL changes significantly from its initial value, the sequence of duty cycles DP and DS set in step S101 based on the initial voltage VL may be inappropriate. Therefore, if the voltage VL changes by a predetermined amount or more, the duty cycle generation units 23 and 24 re-set the sequence of duty cycles DP and DS based on the latest voltage VL. Then, the process returns to step S103.

[0199] In step S103, if the voltage VH exceeds the target voltage VH_target (Y in step S103), then the control unit 19 ends the PWM control (step S104). Thus, the pre-charging operation ends.

[0200] [Variation Example 3]

[0201] In the above embodiments, such as Figure 3 As shown, during the pre-charging period P1, although the switching unit 13 operates according to the duty cycle DP from the start time t1 of the pre-charging operation, it is not limited to this. Alternatively, as... Figure 10As shown, the switching unit 13 can also be operated slightly after the pre-charging operation begins, based on the duty cycle DP. In this example, the pre-charging control unit 21 generates the duty cycle DS by gradually increasing the duty cycle DS during the period from time t21 to t22. Furthermore, if the voltage VH exceeds the threshold Vth, the pre-charging control unit 21 generates the duty cycle DP,DS by gradually increasing the duty cycle DP,DS during the period from time t22 to t23. Thus, during the period from time t21 to t22, the rectifier unit 15 performs a switching operation, and during the period from time t22 to t23, the operation is similar to that in the above embodiment (…). Figure 4 Similarly, the conversion unit 13 and the rectifier unit 15 perform conversion operations. The threshold Vth is set, for example, to satisfy the following equation EQ6.

[0202] Vth<N×VL……(EQ6)

[0203] In other words, the threshold Vth, as shown in Equation EQ3, is set to a voltage within the range of voltage VH, such as when the power conversion system 1 performs a step-down operation during the pre-charging operation.

[0204] Figure 11 Examples of simulated waveforms representing the operation during the period from time t21 to t22: (A) Waveforms of gate signals GE and GF; (B) Waveforms of gate signals GC and GD; (C) Waveforms of the current flowing into capacitor 9 (charging current ICHG); (D) Waveforms of the excitation current IM of transformer 14; (E) Waveforms of the current flowing from voltage line L21B to voltage line L21A in choke inductor 16 (inductor current IL); (F) Waveforms of the voltage at node N4 of winding 14B of transformer 14 with reference to node N5 (transformer voltage VTR2); (G) Waveforms of voltage VH.

[0205] Control Unit 19 Figure 11 As shown in (A), at time t31, the gate signal GF is changed from low to high. Furthermore, the control unit 19 changes the gate signal GF from high to low at a point corresponding to the duty cycle DS after time t31. Next, at time t32, the control unit 19 changes the gate signal GE from low to high. Furthermore, the control unit 19 changes the gate signal GE from high to low at a point corresponding to the duty cycle DS after time t32. The control unit 19 maintains the gate signals GA to GD at low levels. In the power conversion system 1, during the period from time t21 to t22, the operation from time t31 to t33 is repeated while changing the duty cycle DS, thereby charging the capacitor 9. Thus, as... Figure 11 As shown in (G), the voltage VH gradually increases.

[0206] In this example, the power conversion system 1 can have four operating states ST11 to ST14 during the period from time t31 to t32. The operating state ST of the power conversion system 1 changes in the order of operating state ST11, operating state ST12, operating state ST13, and operating state ST14.

[0207] In operating state ST11, the control unit 19 sets the gate signal GF to a high level and the gate signals GA to GE to a low level. Figure 11 (A), (B)). Therefore, transistors S5 and S8 are in the ON state, while transistors S1-S4, S6, and S7 are in the OFF state. In the secondary circuit, current I2 flows sequentially through the positive terminal of the low-voltage battery BL, the choke inductor 16, the ON transistor S5, the winding 14B, the ON transistor S8, and the negative terminal of the low-voltage battery BL, accumulating energy in the choke inductor 16. In the primary circuit, the magnetizing current IM flows through transformer 14 (… Figure 11 (D)).

[0208] In the next operating state ST12, the control unit 19 changes the gate signal GF from high level to low level. Figure 11 (A)). Consequently, transistors S5 and S8 change from the on state to the off state. In the secondary side circuit, a reverse voltage is generated in the choke inductor 16, and the drain-source voltage of each transistor S5 and S8 increases, reaching the breakdown voltage of avalanche breakdown. As a result, avalanche current flows in each transistor S5 and S8, and each transistor S5 and S8 becomes in the avalanche breakdown state AVA. Therefore, the transformer voltages VTR1 and VTR2 become negative voltages (A). Figure 11 (F)). In the primary circuit, the body diodes D2 and D3 of transistor S2 and S3 are in the on state, and the current I1 flows sequentially through the other end of winding 14A (node ​​N2), the body diode D3 of transistor S3, capacitor 9, the body diode D2 of transistor S2, and one end of winding 14A (node ​​N1), while the charging current ICHG flows ( Figure 11 (C)). Thus, the voltage VH rises ( Figure 11 (G)).

[0209] In the next operating state ST13, the release of energy stored in the choke inductor 16 ends, and the avalanche breakdown state AVA of transistors S5 and S8 is released. In the primary side circuit, the previous operating state ST12 continues, and the current I1 flows sequentially through the other end of winding 14A (node ​​N2), the body diode D3 of transistor S3, capacitor 9, the body diode D2 of transistor S2, and one end of winding 14A (node ​​N1). That is, the energy stored in the magnetizing inductor LM of transformer 14 is released and stored in capacitor 9. Thus, the voltage VH rises ( Figure 11 (G)).

[0210] In the next operating state ST14, the energy stored in the magnetizing inductor LM of transformer 14 in the primary circuit is released, and the body diodes D2 and D3 of transistor S2 and S3 are turned off. Therefore, no current flows through the converter 13 in the primary circuit.

[0211] Thus, during the period from time t31 to t32, capacitor 9 is charged, and voltage VH rises. The same applies to the period from time t32 to t33. Furthermore, the above operation is just one example. If, for example, the duty cycle DS rises close to "0.5", then, for example, operating state ST14 out of operating states ST11-ST14 may disappear. In power conversion system 1, as... Figure 11 As shown, by repeatedly performing this action at time points t31 to t33, capacitor 9 is gradually charged, and voltage VH gradually increases.

[0212] In addition, such as Figure 10 As shown, during the period from time t22 to t23 after the voltage VH exceeds the threshold Vth, the power conversion system 1... Figures 4-6 Perform the action as shown. Therefore, as... Figure 4 As shown in (G), the voltage VH gradually increases.

[0213] In addition, such as Figure 10 As shown, if the voltage VH exceeds the target voltage VH_target at time t23, the pre-charge control unit 21 terminates the generation of duty cycles DP and DS. Thus, the pre-charge operation ends. Furthermore, after switches SW1 and SW2 are turned on, the power conversion operation begins.

[0214] Figure 12 This represents an example of an operation of the pre-charge control unit 21 in this modified example.

[0215] First, the duty cycle generation units 23 and 24 of the pre-charge control unit 21 set the sequence of duty cycles DP and DS during the pre-charge period P1 based on the voltage VL (step S121). Specifically, the duty cycle generation unit 23 generates the duty cycle DP during the pre-charge period P1 by gradually increasing the duty cycle DP. The duty cycle generation unit 24 generates the duty cycle DS during the pre-charge period P1 by gradually increasing the duty cycle DS. The duty cycle generation units 23 and 24 generate the duty cycles DP and DS as shown in equations EQ1 and EQ2, such that the duty cycle DS is greater than 0 and less than or equal to 0.5, and the duty cycle DP is greater than 0 and less than or equal to the duty cycle DS.

[0216] Next, the control unit 19 starts PWM control according to the duty cycle DS sequence set in step S121 (step S122). Specifically, the control unit 19 generates gate signals GE and GF according to the duty cycle DS sequence set in step S121, and maintains the gate signals GA to GD at a low level. Thus, in the power conversion system 1, as... Figure 10 As shown, PWM control is applied, capacitor 9 is gradually charged, and voltage VH gradually increases.

[0217] Next, the target value determination unit 22 determines whether the voltage VH exceeds the threshold Vth (step S123). If the voltage VH does not exceed the threshold Vth (N in step S123), then the process of step S123 is repeated until the voltage VH exceeds the threshold Vth.

[0218] If the voltage VH exceeds the threshold Vth (Y in step S123), then the control unit 19 performs PWM control according to the duty cycle sequence DP,DS set in step S121 (step S124). Specifically, the control unit 19 generates gate signals GC~GF according to the duty cycle sequence DP,DS set in step S121, and maintains the gate signals GA,GB at a low level. Thus, in the power conversion system 1, as... Figures 4-6 As shown, PWM control is applied, capacitor 9 is gradually charged, and voltage VH gradually increases.

[0219] Next, the target value determination unit 22 determines whether the voltage VH exceeds the target voltage VH_target (step S125). If the voltage VH does not exceed the target voltage VH_target (N in step S125), then the process of step S125 is repeated until the voltage VH exceeds the target voltage VH_target.

[0220] If the voltage VH exceeds the target voltage VH_target (Y in step S125), then the control unit 19 ends the PWM control (step S126).

[0221] Thus, the pre-charging process ends.

[0222] Furthermore, in this example, as shown in steps S123 and S124, although the control unit 19 performs PWM control according to the set duty cycle DP if the voltage VH exceeds the threshold Vth, it is not limited to this. For example, the control unit 19 may perform PWM control according to the set duty cycle DP after the pre-charging operation has started and a predetermined time has elapsed.

[0223] [Variation Example 4]

[0224] In the above embodiments, although as Figure 1 As shown, the conversion unit 13 is directly connected to the transformer 14, but it is not limited to this. As an alternative, such as Figure 13 As shown in the power conversion system 1A, a resonant inductor Lr can also be provided between the conversion unit 13 and the transformer 14. The power conversion system 1A includes a power conversion device 10A. The power conversion device 10A has a resonant inductor Lr. One end of the resonant inductor Lr is connected to node N2, and the other end is connected to node N3. The other end of the winding 14A of the transformer 14 is connected to node N3. Here, the resonant inductor Lr corresponds to a specific example of the "inductor" of this disclosure. Furthermore, although in this example, one end of the resonant inductor Lr is connected to node N2 and the other end is connected to the other end of the winding 14A, it is not limited to this. As an alternative, for example, one end of the resonant inductor Lr can be connected to node N1 and the other end can be connected to one end of the winding 14A.

[0225] [Variation Example 5]

[0226] In the above embodiments, although as Figure 1 As shown, a conversion unit 13 is provided on the primary side, but it can also be configured as follows: Figure 14As shown in the power conversion system 1B, a resonant inductor Lr and diodes D11 and D12 are further provided. This power conversion system 1B includes a power conversion device 10B. The power conversion device 10B has a resonant inductor Lr and diodes D11 and D12. One end of the resonant inductor Lr is connected to node N2, and the other end is connected to node N3. The other end of the winding 14A of the transformer 14 is connected to node N3. The anode of diode D11 is connected to node N3, and the cathode is connected to voltage line L11. The anode of diode D12 is connected to reference voltage line L12, and the cathode is connected to node N3. Here, the resonant inductor Lr corresponds to a specific example of the "inductor" of this disclosure. Diode D11 corresponds to a specific example of the "first diode" of this disclosure. Diode D12 corresponds to a specific example of the "second diode" of this disclosure. Due to this structure, in the power conversion system 1B, during the power conversion operation of converting the power supplied by the high-voltage battery BH and providing the converted power to the low-voltage battery BL, diodes D11 and D12 function as so-called clamping diodes, suppressing surge voltage generation in the secondary side circuit. During the pre-charging operation, the power conversion system 1B, as... Figures 4-6 As shown, transistors S3 and S4 of the four transistors S1 to S4 in the conversion unit 13 are activated. Therefore, in the power conversion system 1B, during the pre-charging operation, for example, when transistor S3 is on, current flows through transistor S3 instead of diode D11; and for example, when transistor S4 is on, current flows through transistor S4 instead of diode D12. Thus, because the current flowing through diodes D11 and D12 can be reduced during the pre-charging operation, it is not necessary to increase the size of diodes D11 and D12.

[0227] [Variation Example 6]

[0228] In the above embodiment, although the control unit 19 generates a sequence of duty cycles DP,DS during the pre-charging period P1 based on the voltage VL, and controls the operation of the conversion unit 13 and the rectifier unit 15 based on the generated sequence, it is not limited to this. Alternatively, for example, the operation of the conversion unit 13 and the rectifier unit 15 can be controlled by feedback control based on the current flowing through the capacitor 9. Several examples will be given below to illustrate this variation in detail.

[0229] Figure 15This section illustrates a structural example of the power conversion system 1C according to this modified example. The power conversion system 1C includes a power conversion device 10C. The power conversion device 10C includes a current sensor 11C and a control unit 19C. The current sensor 11C detects the current flowing through terminal T11. One end of the current sensor 11C is connected to terminal T11, and the other end is connected to voltage line L11. The current sensor 11C detects the current flowing from voltage line L11 to terminal T11 and takes it as current IH. Furthermore, the current sensor 11C provides the detection result of current IH to the control unit 19C. The control unit 19C controls the operation of the conversion unit 13 and the rectifier unit 15 based on the current IH detected by the current sensor 11C, the voltage VH detected by the voltage sensor 12, and the voltage VL detected by the voltage sensor 18.

[0230] Figure 16 This illustrates a structural example of the control unit 19C. The control unit 19C includes a pre-charge control unit 21C. The pre-charge control unit 21C includes an average current calculation unit 25C, a reference level generation unit 26C, an error signal amplifier 27C, and a duty cycle generation unit 24C.

[0231] The average current calculation unit 25C calculates the average value of the current IH detected by the current sensor 11C. The reference level generation unit 26C generates a reference level REF for the average value of the current IH. The error signal amplifier 27C generates an error signal Serr by amplifying the difference between the reference level REF and the average value of the current IH. The duty cycle generation unit 24C generates a duty cycle DS based on the error signal Serr.

[0232] Therefore, in the power conversion system 1C, during the pre-charging operation, the operation of the rectifier section 15 can be controlled by feedback control based on the current flowing through the capacitor 9.

[0233] Next, the other power conversion system 1D in this variation will be described. This power conversion system 1D is different from power conversion system 1C. Figure 15 Similarly, it has a current sensor 11C and a control unit 19D.

[0234] Figure 17 This illustrates a structural example of the control unit 19D. The control unit 19D includes a pre-charge control unit 21D. The pre-charge control unit 21D includes an average current calculation unit 25C, a reference level generation unit 26C, an error signal amplifier 27C, and a duty cycle generation unit 23D. The duty cycle generation unit 23D generates a duty cycle DP based on the error signal Serr.

[0235] Therefore, in the power conversion system 1D, during the pre-charging operation, the operation of the conversion unit 13 can be controlled by feedback control based on the current flowing through the capacitor 9.

[0236] Furthermore, it is not limited to this. For example, they can be combined to perform feedback control based on the current flowing through the capacitor 9 during the pre-charging operation, thereby controlling the operation of both the converter 13 and the rectifier 15.

[0237] In addition, in the power conversion system 1C, although as Figure 15 As shown, the current sensor 11C is positioned between terminal T11 and voltage line L11, but this is not a limitation. Alternatively, the current sensor 11C could be positioned between terminal T12 and reference voltage line L12, between node N1 and one end of winding 14A, or between node N2 and the other end of winding 14A. Furthermore, although the current sensor 11C is positioned in the primary circuit in this example, this is not a limitation; alternatively, the current sensor 11C could be positioned in the secondary circuit.

[0238] [Variation Example 7]

[0239] In the above embodiment, although the control unit 19 generates a sequence of duty cycles DP,DS for P1 during the pre-charge period based on the voltage VL, and controls the operation of the converter 13 and the rectifier 15 based on the generated duty cycles DP,DS, it is not limited to this. Alternatively, for example, the operation of the converter 13 and the rectifier 15 can be controlled by feedback control based on the voltage VH. Several examples will be given below to illustrate this variation in detail.

[0240] The power conversion system 1E of this modified example has a control unit 19E.

[0241] Figure 18 This illustrates a structural example of the control unit 19E. The control unit 19E includes a pre-charge control unit 21E. The pre-charge control unit 21E includes a reference level generation unit 26E, an error signal amplifier 27E, and a duty cycle generation unit 24E.

[0242] The reference level generation unit 26E generates a reference level REF for voltage VH. The error signal amplifier 27E generates an error signal Serr by amplifying the difference between the reference level REF and voltage VH. The duty cycle generation unit 24E generates a duty cycle DS based on the error signal Serr.

[0243] Therefore, in the power conversion system 1E, during the pre-charging operation, the operation of the rectifier section 15 can be controlled by feedback control based on the voltage VH.

[0244] Next, another power conversion system 1F of this modification will be described. Like power conversion system 1E, power conversion system 1F has a control unit 19F.

[0245] Figure 19 This illustrates a structural example of the control unit 19F. The control unit 19F includes a pre-charge control unit 21F. The pre-charge control unit 21F includes a reference level generation unit 26E, an error signal amplifier 27E, and a duty cycle generation unit 23F. The duty cycle generation unit 23F generates a duty cycle DP based on the error signal Serr.

[0246] Therefore, in the power conversion system 1F, during the pre-charging operation, the operation of the conversion unit 13 can be controlled by feedback control based on the voltage VH.

[0247] Furthermore, it is not limited to this. For example, they can be combined and feedback control can be performed based on the voltage VH during the pre-charging operation, thereby controlling the operation of both the converter 13 and the rectifier 15.

[0248] [Variation Example 8]

[0249] In the above embodiments, although as Figure 1 As shown, four transistors S5 to S8 are placed between voltage line L21A and reference voltage line L22, but it can also be done as follows: Figure 20 As shown in the power conversion system 1G, a Zener diode DZ is further provided between the voltage line L21A and the reference voltage line L22. This power conversion system 1G includes a power conversion device 10G. The power conversion device 10G has a rectifier section 15G. The rectifier section 15G has a Zener diode DZ. The anode of the Zener diode DZ is connected to the reference voltage line L22, and the cathode is connected to the voltage line L21A. The Zener voltage of the Zener diode DZ is lower than the avalanche breakdown voltage of transistors S5 to S8. Therefore, when a reverse voltage is generated in the choke inductor 16, in operating states ST3 to ST5 ( Figures 7C-7E In this configuration, transistors S5 to S8 can be prevented from entering an avalanche breakdown state (AVA). Here, the Zener diode DZ corresponds to a specific example of the "Zener diode" of this disclosure. Furthermore, although the Zener diode DZ is positioned between voltage line L21A and reference voltage line L22 in this example, it is not a limitation. Alternatively, a Zener diode may be positioned between the drain and source of each of transistors S5 to S8.

[0250] In this example, although the Zener diode DZ is positioned between voltage line L21A and reference voltage line L22, it is not a limitation. Alternatively, it could be as follows: Figure 21As shown, an active clamping circuit 90, including a Zener diode DZ, is positioned between voltage line L21A and reference voltage line L22. The active clamping circuit 90 includes a Zener diode DZ, a resistor R1, and a transistor TR. The anode of the Zener diode DZ is connected to one end of the resistor R1 and the gate of the transistor TR, while its cathode is connected to voltage line L21A. One end of the resistor R1 is connected to the anode of the Zener diode DZ, and the other end is connected to the reference voltage line L22. The transistor TR is an N-type field-effect transistor, with its drain connected to voltage line L21A, its gate connected to the anode of the Zener diode DZ and one end of the resistor R1, and its source connected to the reference voltage line L22. Therefore, because the degree of freedom in setting the clamping voltage of the active clamping circuit 90 can be increased, it is possible to prevent transistors S5 to S8 from entering an avalanche breakdown state (AVA) when a reverse voltage is generated in the choke inductor 16.

[0251] [Variation Example 9]

[0252] In the above embodiment, although a choke inductor 16 is provided, it is not limited to this. As an alternative, it can be as follows: Figure 22 As shown in the power conversion system 1H, a choke transformer 31 is provided. This power conversion system 1H includes a power conversion device 10H. The power conversion device 10H has a smoothing section 41H and a diode D13. The smoothing section 41H includes the choke transformer 31. The choke transformer 31 has windings 31A and 31B. One end of winding 31A is connected to voltage line L11, and the other end is connected to the cathode of diode D13. One end of winding 31B is connected to voltage line L21A, and the other end is connected to voltage line L21B. The anode of diode D13 is connected to reference voltage line L12, and the cathode is connected to the other end of winding 31A. Here, the choke transformer 31 corresponds to a specific example of the "choke transformer" of this disclosure. The diode D13 corresponds to a specific example of the "third diode" of this disclosure.

[0253] Figure 23 Examples of simulated waveforms representing the pre-charging operation of power conversion system 1H: (A) represents the waveforms of gate signals GE and GF; (B) represents the waveforms of gate signals GC and GD; (C) represents the waveform of the current flowing into capacitor 9 (charging current ICHG); (D) represents the waveform of the current flowing into diode D13 (diode current ID); (E) represents the waveform of the excitation current IM of transformer 14; (F) represents the waveform of the excitation current ILCH of choke transformer 31; (G) represents the waveform of the voltage at node N4 of winding 14B of transformer 14 with reference to node N5 (transformer voltage VTR2); and (H) represents the waveform of voltage VH.

[0254] Control Unit 19 Figure 23As shown in (A) and (B), at time t41, the gate signals GC and GF are changed from low to high. Furthermore, the control unit 19 changes the gate signal GC from high to low at a time corresponding to the duty cycle DP after time t41, and changes the gate signal GF from high to low at a time corresponding to the duty cycle DS after time t41. Next, at time t42, the control unit 19 changes the gate signals GD and GE from low to high. Furthermore, the control unit 19 changes the gate signal GD from high to low at a time corresponding to the duty cycle DP after time t42, and changes the gate signal GE from high to low at a time corresponding to the duty cycle DS after time t42. The control unit 19 maintains the gate signals GA and GB at low levels. In the power conversion system 1H, the operation at times t41 to t43 is repeated while changing the duty cycles DP and DS, thereby charging the capacitor 9. Thus, as... Figure 23 As shown in (H), the voltage VH gradually increases.

[0255] The following details the operation based on gate signals GC and GF during the period from time t41 to t42. Similarly, the operation based on gate signals GD and GE during the period from time t42 to t43 is also described in detail.

[0256] Figure 24 25. To illustrate the operation during the period from t41 to t42 in more detail, (A) represents the waveform of the gate signals GC to GF, (B) represents the waveform of the current flowing into capacitor 9 (charging current ICHG), (C) represents the waveform of the excitation current IM of transformer 14, (D) represents the waveform of the voltage at node N1 of winding 14A of transformer 14 with reference to node N2 (transformer voltage VTR1), (E) represents the waveform of the voltage at node N4 of winding 14B of transformer 14 with reference to node N5 (transformer voltage VTR2), and (F) represents the waveform of the throttle... The waveforms of the excitation current ILCH of the current transformer 31 are as follows: (G) represents the waveform of the current ILLK flowing into the low-voltage battery BL; (H) represents the waveform of the current flowing into diode D13 (diode current ID); (I) represents the waveform of the voltage (voltage VLCH2) of winding 31A of the current transformer 31 with reference to the cathode of diode D13 on voltage line L11; (J) represents the waveform of the voltage (voltage VLCH1) of winding 31B of the current transformer 31 with reference to voltage line L21B on voltage line L21A; and (K) represents the waveform of voltage VH. Figure 24As shown, the power conversion system 1H can have eight operating states ST21 to ST28 during the period from time t41 to t42. The operating states ST of the power conversion system 1H change in the order of operating state ST21, operating state ST22, operating state ST23...operating state ST28. Operating states ST23 to ST25 are operating states during minute periods. Figure 25 In the image, magnification represents the actions corresponding to the periods ST23 to ST25 and the periods around them in the operating state.

[0257] Figures 26A-26H This indicates the operation of the power conversion system 1H, which has 8 operating states ST21 to ST28.

[0258] In operating state ST21, control unit 19 sets gate signals GC and GF to high level and gate signals GA, GB, GD, and GE to low level. Figure 24 (A)). Therefore, transistors S3, S5, and S8 are in the ON state, and transistors S1, S2, S4, S6, and S7 are in the OFF state. Figure 26A In the secondary circuit, current I2 flows sequentially through the positive terminal of the low-voltage battery BL, winding 31B of the choke transformer 31, transistor S5 (on), winding 14B, transistor S8 (on), and the negative terminal of the low-voltage battery BL, accumulating energy in the magnetizing inductor LCH of the choke transformer 31. In the primary circuit, the body diode D1 of transistor S1 is on, and current I1 flows sequentially through one end of winding 14A (node ​​N1), body diode D1 of transistor S1, transistor S3 (on), and the other end of winding 14A (node ​​N2), accumulating energy in the leakage inductor LLK of transformer 14. At this time, from the secondary circuit perspective, the primary circuit is approximately short-circuited. Therefore, the transformer voltages VTR1 and VTR2 are approximately 0V. Figure 24 (D),(E)).

[0259] In the next operating state ST22, the control unit 19 changes the gate signal GC from high level to low level. Figure 24 (A)). Therefore, transistor S3 changes from the on state to the off state. Figure 26B In the primary circuit, the body diode D4 of transistor S4 is turned on, and the current I1 flows sequentially through one end of winding 14A (node ​​N1), the body diode D1 of transistor S1, capacitor 9, the body diode D4 of transistor S4, and the other end of winding 14A (node ​​N2). The charging current ICHG flows ( Figure 24 (B)). That is to say, the energy stored in the leakage inductor LLK of transformer 14 is released and stored in capacitor 9. Thus, the voltage VH rises ( Figure 24(K)). In the secondary circuit, the transformer voltage VTR2 becomes a positive voltage ( Figure 24 (E)), the excitation current IM begins to flow in transformer 14. Figure 24 (C)). When the power conversion system 1H performs a step-down operation, the inductor current IL increases; when the power conversion system 1H performs a step-up operation, the inductor current IL decreases. Figure 24 (F)).

[0260] In the next minute period of operation, ST23, the control unit 19 changes the gate signal GF from high level to low level. Figure 24 (A), 25(A)). Therefore, transistors S5 and S8 change from the on state to the off state. Figure 26C In the secondary circuit, a reverse voltage is generated in the choke transformer 31, increasing the drain-source voltage of each of transistors S5-S8 and reaching the breakdown voltage of avalanche breakdown. As a result, avalanche current flows in each of transistors S5-S8, and each of transistors S5-S8 enters the avalanche breakdown state AVA. Thus, with each of transistors S5-S8 in the avalanche breakdown state AVA, the transformer voltage VTR2 is approximately 0V. Figure 24 (E), 25(E)). In the primary circuit, continuing from the previous operating state ST22, the current I1 flows sequentially through one end of winding 14A (node ​​N1), the body diode D1 of transistor S1, capacitor 9, the body diode D4 of transistor S4, and the other end of winding 14A (node ​​N2). In the transformer voltage VTR1, the reverse voltage of the leakage inductor LLK of transformer 14 is present. In addition, due to the reverse voltage of choke transformer 31, a voltage is generated in winding 31A of choke transformer 31 ( Figure 24 (I),25(I)). Therefore, diode D13 becomes active, and diode current ID begins to flow. Figure 24 (H),25(H)).

[0261] In the next minute period of operation, ST24, the energy stored in the leakage inductor LLK of transformer 14 in the primary circuit is released, and the body diodes D1 and D4 of transistor S1 and S4 become off. Figure 26DIn this way, no current flows through the converter 13 in the primary side circuit. In the secondary side circuit, transistors S5 to S8 each maintain an avalanche breakdown state AVA. The avalanche current flowing through transistor S5 is greater than the magnetizing current IM by the amount of the avalanche current flowing through transistor S6. Similarly, the avalanche current flowing through transistor S8 is greater than the magnetizing current IM by the amount of the avalanche current flowing through transistor S7. Therefore, the avalanche currents flowing through transistors S6 and S7 approach 0A faster than the avalanche currents flowing through transistors S5 and S8. In addition, diode D13 continues to be in the on state from the previous operating state ST23, and diode current ID flows ( Figure 24 (H), 25(H)). That is to say, the energy stored in the magnetizing inductor LCH of the choke transformer 31 is released and stored in the capacitor 9. Thus, the charging current ICHG flows ( Figure 24 (B),25(B)), voltage VH rises ( Figure 24 (K)).

[0262] In the next tiny period of operation, in state ST25, the avalanche current flowing through transistors S6 and S7 reaches 0A, such as... Figure 26E As shown, the avalanche breakdown state AVA of transistors S6 and S7 is released. Transistors S5 and S8 maintain the avalanche breakdown state AVA. Consequently, transformer voltages VTR1 and VTR2 become negative voltages. As a result, in the primary circuit, the body diodes D2 and D3 of transistors S2 and S3 are turned on, and current I1 flows sequentially through the other end of winding 14A (node ​​N2), the body diode D3 of transistor S3, capacitor 9, the body diode D2 of transistor S2, and one end of winding 14A (node ​​N1). That is, the energy stored in the magnetizing inductor LM of transformer 14 is released and stored in capacitor 9. Furthermore, diode D13 remains on, and diode current ID flows (…). Figure 24 (H), 25(H)). That is to say, the energy stored in the magnetizing inductor LCH of the choke transformer 31 is released and stored in the capacitor 9. Thus, the charging current ICHG flows ( Figure 24 (B),25(B)), voltage VH rises ( Figure 24 (K)).

[0263] In the next operating state ST26, the energy stored in the leakage inductor LLKCH of the choke transformer 31 in the secondary circuit is released, and the avalanche breakdown state AVA of transistors S5 and S8 is released. Figure 26FTherefore, no current flows through the rectifier section 15 in the secondary side circuit. In the primary side circuit, the previous operating state ST25 continues, and the current I1 flows sequentially through the other end of winding 14A (node ​​N2), the body diode D3 of transistor S3, capacitor 9, the body diode D2 of transistor S2, and one end of winding 14A (node ​​N1). That is, the energy stored in the magnetizing inductor LM of transformer 14 is released and stored in capacitor 9. In addition, diode D13 remains in the on state, and diode current ID flows ( Figure 24 (H)). That is to say, the energy stored in the magnetizing inductor LCH of the choke transformer 31 is released and stored in the capacitor 9. Thus, the charging current ICHG flows ( Figure 24 (B)), voltage VH rises ( Figure 24 (K)).

[0264] In the next operating state ST27, the energy stored in the magnetizing inductor LM of transformer 14 in the primary circuit is released, and the body diodes D2 and D3 of transistor S2 and S3 become off. Figure 26G Therefore, no current flows through the converter 13 in the primary circuit. Furthermore, diode D13 remains on, and diode current ID flows ( Figure 24 (H)). That is to say, the energy stored in the magnetizing inductor LCH of the choke transformer 31 is released and stored in the capacitor 9. Thus, the charging current ICHG flows ( Figure 24 (B)), voltage VH rises ( Figure 24 (K)).

[0265] In the next operating state ST28, the energy stored in the magnetizing inductor LCH of the choke transformer 31 in the primary circuit is released, and diode D13 becomes off. Figure 26H Therefore, no current flows through the primary circuit. In other words, in this operating state ST28, no current flows through either the primary or secondary circuits.

[0266] Thus, during the period from time t41 to t42, capacitor 9 is charged, and voltage VH rises. The same applies to the period from time t42 to t43. Furthermore, the above operation is an example. If, for example, the duty cycle DS rises close to "0.5", then, for example, operating state ST28 out of operating states ST21 to ST28 may disappear. In the power conversion system 1H, as... Figure 23 As shown, by repeatedly performing this action at time points t41 to t43, capacitor 9 is gradually charged, and voltage VH gradually increases.

[0267] In the power conversion system 1H of this modified example, a choke transformer 31 is provided instead of the choke inductor 16 in the above embodiment. Figure 1 Therefore, in the power conversion system 1H, for example, when transistors S5 to S8 are in the avalanche breakdown state AVA, the consumed energy can be efficiently transferred to the primary circuit and regenerated. Furthermore, in the power conversion system 1H, for example, the length of the period during which transistors S5 to S8 are in the avalanche breakdown state AVA can be shortened.

[0268] exist Figure 22 In the example, although diode D13 and winding 31A of choke transformer 31 are provided on the path connecting reference voltage line L12 and voltage line L11, it is not limited to this; it can also be as follows: Figure 27 As shown in the power conversion system 1I, a switch SW is further provided along this path. This power conversion system 1I includes a power conversion device 10I. The power conversion device 10I has a switch SW and a control unit 19I. One end of the switch SW is connected to the reference voltage line L12, and the other end is connected to the anode of the diode D13. The switch SW operates according to the instruction from the control unit 19I, becoming in the on state, thereby connecting the anode of the diode D13 to the reference voltage line L12. The control unit 19I, similar to the control unit 19 in the above embodiment, controls the operation of the conversion unit 13 and the rectifier unit 15 based on the voltage VH detected by the voltage sensor 12 and the voltage VL detected by the voltage sensor 18, thereby controlling the operation of the power conversion device 10I. The control unit 19I turns the switch SW on during pre-charging operation and turns the switch SW off during power conversion operation. Specifically, as... Figure 28 As shown, when the voltage VH exceeds the target voltage VH_target ("Y" in step S103), the control unit 19I terminates the PWM control (step S104) and turns the switch SW off (step S135). Here, the switch SW corresponds to a specific example of the "switch" of this disclosure.

[0269] Figure 29 This illustrates a structural example of another power conversion system 1J in this modification. The power conversion system 1J connects the two ends of the winding 31A of the choke transformer 31 to the secondary circuit. That is, although in Figure 22In the power conversion system 1H shown, the two ends of the winding 31A of the choke transformer 31 are connected to the primary circuit on the high-voltage battery BH side relative to the transformer 14. However, in the power conversion system 1J of this modified example, the two ends of the winding 31A of the choke transformer 31 are connected to the secondary circuit on the low-voltage battery BL side relative to the transformer 14. This power conversion system 1J includes a power conversion device 10J. The power conversion device 10J has a smoothing section 41J and a diode D13. The smoothing section 41J has a choke transformer 31. The choke transformer 31 has windings 31A and 31B. One end of winding 31A is connected to voltage line L21B, and the other end is connected to the cathode of diode D13. One end of winding 31B is connected to voltage line L21A, and the other end is connected to voltage line L21B. The anode of diode D13 is connected to the reference voltage line L22, and the cathode is connected to the other end of winding 31A. Here, choke transformer 31 corresponds to a specific example of the "choke transformer" of this disclosure. Diode D13 corresponds to a specific example of the "third diode" of this disclosure.

[0270] Figure 30 An example of the pre-charge operation of the power conversion system 1J is shown below: (A) shows the waveforms of the gate signals GE and GF; (B) shows the waveforms of the gate signals GC and GD; (C) shows the waveform of the current flowing into capacitor 9 (charging current ICHG); (D) shows the waveform of the current flowing into winding 14A of transformer 14 (transformer current IP); (E) shows the waveform of the current flowing into winding 31B of choke transformer 31 (coil current ILCH1); (F) shows the waveform of the current flowing into winding 31A of choke transformer 31 (coil current ILCH2); (G) shows the waveform of the voltage at node N4 of winding 14B of transformer 14 with reference to node N5 (transformer voltage VTR2); and (H) shows the waveform of voltage VH.

[0271] Control Unit 19 Figure 30As shown in (A) and (B), at time t51, the gate signals GC and GF are changed from low to high. Furthermore, the control unit 19 changes the gate signal GC from high to low at a time corresponding to the duty cycle DP after passing from time t51, and changes the gate signal GF from high to low at a time corresponding to the duty cycle DS after passing from time t51. Next, at time t52, the control unit 19 changes the gate signals GD and GE from low to high. Furthermore, the control unit 19 changes the gate signal GD from high to low at a time corresponding to the duty cycle DP after passing from time t52, and changes the gate signal GE from high to low at a time corresponding to the duty cycle DS after passing from time t52. The control unit 19 maintains the gate signals GA and GB at low levels. In the power conversion system 1J, the operation at times t51 to t53 is repeated while changing the duty cycles DP and DS, thereby charging the capacitor 9. Thus, as... Figure 30 As shown in (H), the voltage VH gradually increases.

[0272] The following details the operation based on gate signals GC and GF during time points t51 to t52. Similarly, the operation based on gate signals GD and GE during time points t52 to t53 is also described in detail. The power conversion system 1J can have five operating states ST31 to ST35 during time points t51 to t52. Furthermore, in this description, details such as... Figure 24 The description of the operating states during minute periods, such as operating states ST23 to ST25. The operating states ST of the power conversion system 1J change in the order of operating state ST31, operating state ST32... operating state ST35.

[0273] Figures 31A-31E This indicates the operation of the power conversion system 1J with 5 operating states ST31 to ST35.

[0274] In operating state ST31, control unit 19 sets gate signals GC and GF to high level and gate signals GA, GB, GD, and GE to low level. Figure 31A Therefore, transistors S3, S5, and S8 become ON, and transistors S1, S2, S4, S6, and S7 become OFF. Figure 31AIn the secondary circuit, current I2 flows sequentially through the positive terminal of the low-voltage battery BL, winding 31B of the choke transformer 31, transistor S5 (on), winding 14B, transistor S8 (on), and the negative terminal of the low-voltage battery BL, accumulating energy in the magnetizing inductor LCH of the choke transformer 31. In the primary circuit, the body diode D1 of transistor S1 is on, and current I1 flows sequentially through one end of winding 14A (node ​​N1), body diode D1 of transistor S1, transistor S3 (on), and the other end of winding 14A (node ​​N2), accumulating energy in the leakage inductor LLK of transformer 14. At this time, from the secondary circuit perspective, the primary circuit is approximately short-circuited. Therefore, the transformer voltage VTR2 is approximately 0V. Figure 30 (G)).

[0275] In the next operating state ST32, the control unit 19 changes the gate signal GC from high level to low level. Figure 30 (B)). Therefore, transistor S3 changes from the on state to the off state. Figure 31B In the primary circuit, the body diode D4 of transistor S4 is turned on, and the current I1 flows sequentially through one end of winding 14A (node ​​N1), the body diode D1 of transistor S1, capacitor 9, the body diode D4 of transistor S4, and the other end of winding 14A (node ​​N2). The charging current ICHG flows ( Figure 30 (C)). That is to say, the energy stored in the leakage inductor LLK of transformer 14 is released and stored in capacitor 9. Thus, the voltage VH rises ( Figure 30 (H)). In the secondary circuit, the transformer voltage VTR2 becomes a positive voltage ( Figure 30 (G)). When the power conversion system 1J is performing a step-down operation, the choke coil current ILCH1 increases; when the power conversion system 1J is performing a step-up operation, the choke coil current ILCH1 decreases. Figure 30 (E)).

[0276] In the next operating state ST33, the control unit 19 changes the gate signal GF from high level to low level. Figure 30 (A)). Therefore, transistors S5 and S8 change from the on state to the off state. Figure 31C In the primary circuit, the previous operating state of ST32 continues, and the current I1 flows sequentially through one end of winding 14A (node ​​N1), the body diode D1 of transistor S1, capacitor 9, the body diode D4 of transistor S4, and the other end of winding 14A (node ​​N2). As a result, the voltage VH continues to rise. Figure 30(H)). In the secondary circuit, a reverse voltage is generated in the choke transformer 31. Due to this reverse voltage, a voltage is generated in the winding 31A of the choke transformer 31. As a result, diode D13 becomes active, and current I2 flows sequentially through winding 31A, low-voltage battery BL, diode D13, and winding 31A. The choke coil current ILCH2 flows ( Figure 30 (F)).

[0277] In the next operating state ST34, in the primary circuit, the excitation energy of transformer 14 ends, and the body diode D1 of transistor S1 and the body diode D4 of transistor S4 become off. Figure 31D In this way, no current flows through the converter 13 in the primary side circuit. In the secondary side circuit, diode D13 continues to be in the on state from the previous operating state ST33, and the choke coil current ILCH2 flows ( Figure 30 (F)).

[0278] In the next operating state ST35, the energy stored in the magnetizing inductor LCH of the choke transformer 31 in the secondary circuit is released, and diode D13 becomes off. Figure 31E Therefore, no current flows through the secondary circuit. In other words, in this operating state ST35, no current flows through either the primary or secondary circuits.

[0279] Thus, during the period from time t51 to t52, capacitor 9 is charged, and voltage VH rises. The same applies to the period from time t52 to t53.

[0280] exist Figure 29 In the example, although diode D13 and winding 31A of choke transformer 31 are provided on the path connecting reference voltage line L22 and voltage line L21B, it is not limited to this; it can also be as follows: Figure 32 As shown in the power conversion system 1K, a switch SW is further provided along this path. The power conversion system 1K includes a power conversion device 10K. The power conversion device 10K has a switch SW and a control unit 19K. One end of the switch SW is connected to the reference voltage line L22, and the other end is connected to the anode of the diode D13. The switch SW operates according to the instruction from the control unit 19K, becoming in the on state, thereby connecting the anode of the diode D13 to the reference voltage line L22. Similar to the control unit 19 in the above embodiment, the control unit 19K controls the operation of the conversion unit 13 and the rectifier unit 15 based on the voltage VH detected by the voltage sensor 12 and the voltage VL detected by the voltage sensor 18, thereby controlling the operation of the power conversion device 10K. The control unit 19K keeps the switch SW in the on state during pre-charging operation and in the off state during power conversion operation.

[0281] [Variation Example 10]

[0282] In the above embodiments, such as Figure 1 As shown, although the rectifier section 15 is constructed using a full-bridge circuit, it is not limited to this. Alternatively, a so-called center-tapped power conversion system could also be used. This modified example will be described in detail below.

[0283] Figure 33 This illustrates a structural example of the power conversion system 2 in this modified example. The power conversion system 2 includes a power conversion device 30. The power conversion device 30 includes a transformer 34, a rectifier 35, and a control unit 39.

[0284] Transformer 34 has windings 34A, 34B, and 34C. One end of winding 34A is connected to node N1 of transition section 13, and the other end is connected to node N2 of transition section 13. One end of winding 34B is connected to node N6, and the other end is connected to one end of winding 34C and voltage line L21A. One end of winding 34C is connected to the other end of winding 34B and voltage line L21A, and the other end is connected to node N7.

[0285] The rectifier section 35 includes transistors S9 and S10. Transistors S9 and S10 are constructed using, for example, N-type field-effect transistors. Transistors S9 and S10 each have body diodes D9 and D10, respectively. Transistor S9 is positioned on the path connecting node N6 and reference voltage line L22, and node N6 is connected to reference voltage line L22 by being in the ON state. The drain of transistor S9 is connected to node N6, its gate is supplied with a gate signal GF, and its source is connected to reference voltage line L22. Transistor S10 is positioned on the path connecting node N7 and reference voltage line L22, and node N7 is connected to reference voltage line L22 by being in the ON state. The drain of transistor S10 is connected to node N7, its gate is supplied with a gate signal GE, and its source is connected to reference voltage line L22.

[0286] The control unit 39 is configured to control the operation of the conversion unit 13 and the rectifier unit 35 based on the voltage VH detected by the voltage sensor 12 and the voltage VL detected by the voltage sensor 18, thereby controlling the operation of the power conversion device 30. Specifically, the control unit 39 generates gate signals GA to GF based on the voltages VH and VL, and performs PWM (Pulse Width Modulation) control through these gate signals GA to GF, thereby controlling the operation of the power conversion device 30.

[0287] Here, transformer 34 corresponds to a specific example of a "transformer" of this disclosure. Winding 34A corresponds to a specific example of a "first winding" of this disclosure. Winding 34B corresponds to a specific example of a "second winding" of this disclosure. Winding 34C corresponds to a specific example of a "third winding" of this disclosure. Rectifier 35 corresponds to a specific example of a "rectifier section" of this disclosure. Node N6 corresponds to a specific example of a "sixth node" of this disclosure. Node N7 corresponds to a specific example of a "seventh node" of this disclosure. Transistor S9 corresponds to a specific example of a "ninth switching element" of this disclosure. Transistor S10 corresponds to a specific example of a "tenth switching element" of this disclosure.

[0288] The above-described modifications can also be applied to power conversion system 2. Several examples of power conversion systems with modifications will be provided below for illustration.

[0289] Figure 34 This illustrates a structural example of a power conversion system 2A with modifications to Example 4. The power conversion system 2A includes a power conversion device 30A. The power conversion device 30A has a resonant inductor Lr. One end of the resonant inductor Lr is connected to node N2, and the other end is connected to the other end of the winding 34A of the transformer 34.

[0290] Figure 35 This illustrates a structural example of a power conversion system 2B adapted from Modified Example 5. The power conversion system 2B includes a power conversion device 30B. The power conversion device 30B has a resonant inductor Lr and diodes D11 and D12. One end of the resonant inductor Lr is connected to node N2, and the other end is connected to node N3. The other end of the winding 34A of the transformer 34 is connected to node N3. The anode of diode D11 is connected to node N3, and the cathode is connected to voltage line L11. The anode of diode D12 is connected to reference voltage line L12, and the cathode is connected to node N3.

[0291] Figure 36 This illustrates a structural example of a power conversion system 2C adapted to Modified Example 6. The power conversion system 2C includes a power conversion device 30C. The power conversion device 30C has a current sensor 11C and a control unit 39C. The current sensor 11C detects the current flowing through terminal T11. One end of the current sensor 11C is connected to terminal T11, and the other end is connected to voltage line L11. The current sensor 11C detects the current flowing from voltage line L11 to terminal T11 and takes it as current IH. The control unit 39C controls the operation of the conversion unit 13 and the rectifier unit 35 based on the current IH detected by the current sensor 11C, the voltage VH detected by the voltage sensor 12, and the voltage VL detected by the voltage sensor 18. The control unit 39C may, for example, have... Figure 16The pre-charge control unit 21C shown may also have Figure 17 The pre-charge control unit 21D shown is shown.

[0292] Figure 37 This illustrates a structural example of a power conversion system 2G adapted to Modified Example 8. The power conversion system 2G includes a power conversion device 30G. The power conversion device 30G has a rectifier section 35G. The rectifier section 35G includes Zener diodes DZ1 and DZ2. The anode of Zener diode DZ1 is connected to the reference voltage line L22, and the cathode is connected to node N6. The anode of Zener diode DZ2 is connected to the reference voltage line L22, and the cathode is connected to node N7. Furthermore, this is not limited to this example; other examples may also be used. Figure 21 The active clamping circuit 90 is shown. Specifically, the active clamping circuit 90 (active clamping circuit 90A) can also be set between node N6 and reference voltage line L22, and another active clamping circuit 90 (active clamping circuit 90B) can be set between node N7 and reference voltage line L22.

[0293] Figure 38 This illustrates a structural example of a power conversion system 2H ​​with modifications to Example 9. The power conversion system 2H ​​includes a power conversion device 30H. The power conversion device 30H has a choke transformer 31 and a diode D13. The choke transformer 31 has windings 31A and 31B. One end of winding 31A is connected to voltage line L11, and the other end is connected to the cathode of diode D13. One end of winding 31B is connected to voltage line L21A, and the other end is connected to voltage line L21B. The anode of diode D13 is connected to a reference voltage line L12, and the cathode is connected to the other end of winding 31A. Furthermore, it can also be combined with… Figure 27 Similarly, the switch SW is further configured.

[0294] Figure 39 This illustrates a structural example of another power conversion system 2J applicable to variation 9. This power conversion system 2J includes a power conversion device 30J. The power conversion device 30J has a choke transformer 31 and a diode D13. The choke transformer 31 has windings 31A and 31B. One end of winding 31A is connected to voltage line L21B, and the other end is connected to the cathode of diode D13. One end of winding 31B is connected to voltage line L21A, and the other end is connected to voltage line L21B. The anode of diode D13 is connected to reference voltage line L22, and the cathode is connected to the other end of winding 31A. Furthermore, it can also be combined with… Figure 32 Similarly, the switch SW is further configured.

[0295] [Other variations]

[0296] Alternatively, two or more of these variations can be used in combination.

[0297] The present invention has been described above with examples of embodiments and variations, but the present invention is not limited to these embodiments and various changes can be made.

[0298] For example, in the above embodiment, although a step-down operation is performed in the power conversion operation, it is not limited to this and a step-up operation can also be performed.

[0299] For example, in the above embodiment, although a unidirectional power conversion operation is performed from the high-voltage battery BH to the low-voltage battery BL, it is not limited to this. For example, in the power conversion operation, a bidirectional conversion operation can be performed by setting a mode that supplies power from the high-voltage battery BH to the low-voltage battery BL and a mode that supplies power from the low-voltage battery BL to the high-voltage battery BH. In this case, during the preparation period before performing the power conversion operation in the mode that supplies power from the high-voltage battery BH to the low-voltage battery BL, the capacitor 9 can be charged using the power supplied by the low-voltage battery BL.

[0300] For example, in the above embodiment, although the control unit 19 generates the duty cycle DP,DS in a manner that satisfies equations EQ1 and EQ2 during the pre-charging operation, it is not limited to this. As an alternative, for example, in a power conversion system, when performing a power conversion operation in a mode that supplies power from the low-voltage battery BL to the high-voltage battery BH, the control unit 19 generates the duty cycle DP,DS in a manner that satisfies equations EQ1 and EQ2. This power conversion system performs a bidirectional conversion operation in the power conversion operation, having a mode that supplies power from the high-voltage battery BH to the low-voltage battery BL and a mode that supplies power from the low-voltage battery BL to the high-voltage battery BH.

[0301] For example, when the body diode of a transistor is in the ON state, the following synchronization action can be performed: at that point, the gate signal of the transistor is set to a high level and the transistor is turned on. This can improve the conversion efficiency of the power conversion system.

[0302] Furthermore, the present invention can also adopt the following structure. (1)

[0304] A power conversion device comprising:

[0305] The first power terminal has a first wiring terminal and a second wiring terminal;

[0306] The switching unit includes a first switching element, a second switching element, a third switching element, and a fourth switching element. The first switching element is disposed on the path connecting the first power node and the first terminal, and the first power node is led to the first terminal. The second switching element is disposed on the path connecting the first node and the second power node, and the second power node is led to the second terminal. The third switching element is disposed on the path connecting the first power node and the second node. The fourth switching element is disposed on the path connecting the second node and the second power node.

[0307] A transformer has a first winding and a second winding, the first winding having a first terminal and a second terminal, the first terminal being connected to a first node and the second terminal being connected to a second node;

[0308] The rectifier section is connected to the second winding and has multiple switching elements;

[0309] The second power terminal is led to the rectifier section; and

[0310] The control unit controls the operation of the first switching element, the second switching element, the third switching element, the fourth switching element, and the plurality of switching elements.

[0311] The control unit controls the operation of the conversion unit and the rectifier unit during a predetermined period to supply power from the second power terminal to the first power terminal. This predetermined period differs from the period during which power is supplied from the first power terminal to the second power terminal.

[0312] The control unit operates the converter with a first duty cycle and the rectifier with a second duty cycle during the predetermined period.

[0313] The first duty cycle is greater than 0 and less than or equal to the second duty cycle. (2)

[0315] The power conversion device described in (1), wherein,

[0316] The defined period is the period preceding the period during which power is supplied from the first power terminal to the second power terminal. (3)

[0318] The power conversion device of (1) or (2), wherein,

[0319] The second duty cycle is greater than 0 and less than or equal to 0.5. (4)

[0321] The power conversion device according to any one of (1) to (3), wherein,

[0322] The defined period includes a first period and a second period following the first period.

[0323] The control unit controls the operation of the rectifier unit during the first period and controls the operation of the converter unit and the rectifier unit during the second period. (5)

[0325] The power conversion device according to any one of (1) to (4), wherein,

[0326] During the predetermined period, the control unit controls the operation of two of the first, second, third, and fourth switching elements of the switching unit. (6)

[0328] The power conversion device according to any one of (1) to (5), wherein,

[0329] The control unit determines the sequence of the first duty cycle of the converter and the sequence of the second duty cycle of the rectifier for the specified time period based on the voltage of the second power terminal, and controls the operation of the converter and the rectifier based on the determination result. (7)

[0331] The power conversion device according to any one of (1) to (6), wherein,

[0332] The control unit controls the operation of one or both of the conversion unit and the rectifier unit by performing feedback control based on a first current corresponding to the current flowing through the first power terminal. (8)

[0334] The power conversion device described in (7), wherein,

[0335] The first current includes any one of the current flowing through the first power terminal, the current flowing through the conversion section, and the current flowing through the first winding. (9)

[0337] The power conversion device according to any one of (1) to (8), wherein,

[0338] The control unit controls the operation of one or both of the conversion unit and the rectifier unit by performing feedback control based on the voltage of the first power terminal. (10)

[0340] The power conversion device according to any one of (1) to (9), wherein,

[0341] The control unit terminates control for the predetermined period when the voltage at the first power terminal exceeds a predetermined voltage. (11)

[0343] The power conversion device according to any one of (1) to (10), wherein,

[0344] Further equipped with inductors,

[0345] The inductor has a first terminal connected to the second node and a second terminal connected to the third node.

[0346] The second terminal of the first winding is connected to the third node and is also connected to the second node via the inductor. (12)

[0348] The power conversion device described in (11), wherein,

[0349] It further includes a first diode and a second diode.

[0350] The first diode has a cathode connected to the first power node and an anode connected to the third node.

[0351] The second diode has a cathode connected to the third node and an anode connected to the second power node.

[0352] The control unit controls the operation of the third and fourth switching elements among the first, second, third, and fourth switching elements of the switching unit during the predetermined period. (13)

[0354] The power conversion device according to any one of (1) to (12), wherein,

[0355] The second power terminal has a third terminal and a fourth terminal.

[0356] The plurality of switching elements in the rectifier section include a fifth switching element, a sixth switching element, a seventh switching element, and an eighth switching element. The fifth switching element is disposed on the path connecting the third power node and the fourth node, and the third power node is led to the third terminal. The sixth switching element is disposed on the path connecting the fourth node and the fourth power node, and the fourth power node is led to the fourth terminal. The seventh switching element is disposed on the path connecting the third power node and the fifth node. The eighth switching element is disposed on the path connecting the fifth node and the fourth power node. (14)

[0358] The power conversion device described in (13), wherein,

[0359] The rectifier section further includes a Zener diode.

[0360] The Zener diode is positioned on the path connecting the third power node and the fourth power node. (15)

[0362] The power conversion device according to any one of (1) to (12), wherein,

[0363] The second power terminal has a third terminal and a fourth terminal.

[0364] The transformer further has a third winding.

[0365] The second winding has a first terminal connected to a third power node and a second terminal connected to a sixth node, the third power node being led to the third terminal.

[0366] The third winding has a first terminal connected to the third power node and a second terminal connected to the seventh node.

[0367] The plurality of switching elements of the rectifier section include a ninth switching element and a tenth switching element. The ninth switching element is disposed on the path connecting the sixth node and the fourth power node, the fourth power node being led to the fourth terminal block, and the tenth switching element is disposed on the path connecting the seventh node and the fourth power node. (16)

[0369] The power conversion device described in (15), wherein,

[0370] The rectifier section further includes a first Zener diode and a second Zener diode.

[0371] The first Zener diode is positioned on the path connecting the sixth node and the fourth power node.

[0372] The second Zener diode is disposed on the path connecting the seventh node and the fourth power node. (17)

[0374] The power conversion device according to any one of (1) to (12), wherein,

[0375] It further includes a choke transformer and a third diode.

[0376] The choke transformer has a first winding and a second winding.

[0377] The second power terminal has a third terminal and a fourth terminal.

[0378] The first winding of the choke transformer and the third diode are arranged on the path connecting the first power node and the second power node.

[0379] The second winding of the choke transformer is disposed on the path connecting the rectifier section and the third terminal. (18)

[0381] The power conversion device described in (17), wherein,

[0382] Further, it has a switch.

[0383] The first winding of the choke transformer, the third diode, and the switch are arranged on the path connecting the first power node and the second power node.

[0384] The switch is in the on state during the specified period. (19)

[0386] The power conversion device according to any one of (1) to (12), wherein,

[0387] It further includes a choke transformer and a third diode.

[0388] The choke transformer has a first winding and a second winding.

[0389] The second power terminal has a third terminal and a fourth terminal.

[0390] The first winding of the choke transformer and the third diode are arranged on the path connecting the third terminal and the fourth terminal.

[0391] The second winding of the choke transformer is disposed on the path connecting the rectifier section and the third terminal. (20)

[0393] The power conversion device described in (19), wherein,

[0394] Further, it has a switch.

[0395] The first winding of the choke transformer, the third diode, and the switch are arranged on the path connecting the third terminal and the fourth terminal.

[0396] The switch is in the on state during the specified period. (twenty one)

[0398] The power conversion device according to any one of (1) to (20), wherein,

[0399] The first terminal and the second terminal are connected to a capacitor. (twenty two)

[0401] A power conversion system, comprising:

[0402] The first battery has a first terminal and a second terminal;

[0403] A capacitor has a first terminal and a second terminal;

[0404] A first switch is disposed on the path connecting the first terminal of the first battery and the first terminal of the capacitor;

[0405] The second switch is disposed on the path connecting the second terminal of the first battery and the second terminal of the capacitor;

[0406] Power conversion devices; and

[0407] Second battery,

[0408] The power conversion device has:

[0409] A first power terminal has a first wiring terminal and a second wiring terminal, wherein the first wiring terminal is connected to the first terminal of the capacitor, and the second wiring terminal is connected to the second terminal of the capacitor;

[0410] The switching unit includes a first switching element, a second switching element, a third switching element, and a fourth switching element. The first switching element is disposed on the path connecting the first power node and the first terminal, and the first power node is led to the first terminal. The second switching element is disposed on the path connecting the first node and the second power node, and the second power node is led to the second terminal. The third switching element is disposed on the path connecting the first power node and the second node. The fourth switching element is disposed on the path connecting the second node and the second power node.

[0411] A transformer has a first winding and a second winding, the first winding having a first terminal and a second terminal, the first terminal being connected to a first node and the second terminal being connected to a second node;

[0412] The rectifier section is connected to the second winding and has multiple switching elements;

[0413] A second power terminal is led to the rectifier and connected to the second battery; and

[0414] The control unit controls the operation of the first switching element, the second switching element, the third switching element, the fourth switching element, and the plurality of switching elements.

[0415] The control unit controls the operation of the conversion unit and the rectifier unit during a predetermined period to supply power from the second power terminal to the first power terminal. This predetermined period differs from the period during which power is supplied from the first power terminal to the second power terminal.

[0416] The control unit operates the converter with a first duty cycle and the rectifier with a second duty cycle during the predetermined period.

[0417] The first duty cycle is greater than 0 and less than or equal to the second duty cycle.

[0418] This disclosure contains the subject matter disclosed in Japanese priority patent applications JP2021-056534 and JP2021-198515, filed with the Japan Patent Office on March 30, 2021 and December 7, 2021, respectively, the entire contents of which are incorporated herein by reference.

[0419] Those skilled in the art should understand that while various modifications, combinations, sub-combinations, and alternatives may arise depending on design requirements and other factors, they are all included within the scope of the appended claims or their equivalents.

Claims

1. A power conversion device, comprising: The first power terminal has a first wiring terminal and a second wiring terminal; The switching unit includes a first switching element, a second switching element, a third switching element, and a fourth switching element. The first switching element is disposed on the path connecting the first power node and the first terminal, and the first power node is led to the first terminal. The second switching element is disposed on the path connecting the first node and the second power node, and the second power node is led to the second terminal. The third switching element is disposed on the path connecting the first power node and the second node. The fourth switching element is disposed on the path connecting the second node and the second power node. A transformer has a first winding and a second winding, the first winding having a first terminal and a second terminal, the first terminal being connected to a first node and the second terminal being connected to a second node; The rectifier section is connected to the second winding and has multiple switching elements; A smooth section with a choke ring connected to the rectifier section; A second power terminal, guided to the smooth portion, has a third terminal and a fourth terminal; and The control unit controls the operation of the first switching element, the second switching element, the third switching element, the fourth switching element, and the plurality of switching elements. The control unit controls the operation of the conversion unit and the rectifier unit during a predetermined period to supply power from the second power terminal to the first power terminal, wherein the predetermined period is the period preceding the period during which power is supplied from the first power terminal to the second power terminal. The control unit operates the converter with a first duty cycle and the rectifier with a second duty cycle during the predetermined period. The first duty cycle is greater than 0 and less than or equal to the second duty cycle. The second winding has a first terminal and a second terminal, the first terminal being connected to a fourth node and the second terminal being connected to a fifth node. The plurality of switching elements in the rectifier section includes a fifth switching element, a sixth switching element, a seventh switching element, and an eighth switching element. The fifth switching element is disposed on the path connecting the third power node and the fourth power node, with the third power node leading to the third terminal. The sixth switching element is disposed on the path connecting the fourth power node and the fourth terminal. The seventh switching element is disposed on the path connecting the third power node and the fifth node. The eighth switching element is disposed on the path connecting the fifth node and the fourth power node. The control unit sequentially performs the first control, the second control, the third control, the fourth control, the fifth control, and the sixth control during the predetermined period. In the first control, the control unit sets the third, fifth, and eighth switching elements to the on state, and sets the first, second, fourth, sixth, and seventh switching elements to the off state. In the second control, the control unit sets the fifth and eighth switching elements to the ON state, and sets the first, second, third, fourth, sixth, and seventh switching elements to the OFF state. In the third control, the control unit sets the first switching element, the second switching element, the third switching element, the fourth switching element, the fifth switching element, the sixth switching element, the seventh switching element, and the eighth switching element to the off state. In the fourth control, the control unit sets the fourth, sixth, and seventh switching elements to the on state, and sets the first, second, third, fifth, and eighth switching elements to the off state. In the fifth control, the control unit sets the sixth and seventh switching elements to the ON state, and sets the first, second, third, fourth, fifth, and eighth switching elements to the OFF state. In the sixth control, the control unit sets the first switching element, the second switching element, the third switching element, the fourth switching element, the fifth switching element, the sixth switching element, the seventh switching element, and the eighth switching element to the off state.

2. A power conversion device, comprising: The first power terminal has a first wiring terminal and a second wiring terminal; The switching unit includes a first switching element, a second switching element, a third switching element, and a fourth switching element. The first switching element is disposed on the path connecting the first power node and the first terminal, and the first power node is led to the first terminal. The second switching element is disposed on the path connecting the first node and the second power node, and the second power node is led to the second terminal. The third switching element is disposed on the path connecting the first power node and the second node. The fourth switching element is disposed on the path connecting the second node and the second power node. A transformer has a first winding, a second winding and a third winding. The first winding has a first terminal and a second terminal. The first terminal is connected to a first node and the second terminal is connected to a second node. The rectifier section is connected to the second winding and the third winding, and has multiple switching elements; A smooth section with a choke ring connected to the rectifier section; A second power terminal, guided to the smooth portion, has a third terminal and a fourth terminal; and The control unit controls the operation of the first switching element, the second switching element, the third switching element, the fourth switching element, and the plurality of switching elements. The control unit controls the operation of the conversion unit and the rectifier unit during a predetermined period to supply power from the second power terminal to the first power terminal, wherein the predetermined period is the period preceding the period during which power is supplied from the first power terminal to the second power terminal. The control unit operates the converter with a first duty cycle and the rectifier with a second duty cycle during the predetermined period. The first duty cycle is greater than 0 and less than or equal to the second duty cycle. The second winding has a first terminal connected to a third power node and a second terminal connected to a sixth node, the third power node being led to the third terminal. The third winding has a first terminal connected to the third power node and a second terminal connected to the seventh node. The plurality of switching elements in the rectifier section includes a ninth switching element and a tenth switching element. The ninth switching element is disposed on the path connecting the sixth node and the fourth power node, the fourth power node being led to the fourth terminal. The tenth switching element is disposed on the path connecting the seventh node and the fourth power node. The control unit sequentially performs the first control, the second control, the third control, the fourth control, the fifth control, and the sixth control during the predetermined period. In the first control, the control unit sets the third and ninth switching elements to the on state, and sets the first, second, fourth, and tenth switching elements to the off state. In the second control, the control unit sets the ninth switching element to the ON state and sets the first switching element, the second switching element, the third switching element, the fourth switching element, and the tenth switching element to the OFF state. In the third control, the control unit sets the first switching element, the second switching element, the third switching element, the fourth switching element, the ninth switching element, and the tenth switching element to the off state. In the fourth control, the control unit sets the fourth and tenth switching elements to the ON state, and sets the first, second, third, and ninth switching elements to the OFF state. In the fifth control, the control unit sets the tenth switching element to the on state and sets the first switching element, the second switching element, the third switching element, the fourth switching element, and the ninth switching element to the off state. In the sixth control, the control unit sets the first switching element, the second switching element, the third switching element, the fourth switching element, the ninth switching element, and the tenth switching element to the off state.

3. The power conversion device according to claim 1 or claim 2, wherein, The second duty cycle is greater than 0 and less than or equal to 0.

5.

4. The power conversion device according to any one of claims 1 to 3, wherein, The defined period includes a first period and a second period following the first period. The control unit controls the operation of the rectifier unit during the first period and controls the operation of the converter unit and the rectifier unit during the second period.

5. The power conversion device according to any one of claims 1 to 4, wherein, The control unit determines the sequence of the first duty cycle of the converter and the sequence of the second duty cycle of the rectifier for the specified time period based on the voltage of the second power terminal, and controls the operation of the converter and the rectifier based on the determination result.

6. The power conversion device according to any one of claims 1 to 5, wherein, The control unit controls the operation of one or both of the conversion unit and the rectifier unit by performing feedback control based on a first current corresponding to the current flowing through the first power terminal.

7. The power conversion device according to claim 6, wherein, The first current includes any one of the current flowing through the first power terminal, the current flowing through the conversion section, and the current flowing through the first winding.

8. The power conversion device according to any one of claims 1 to 7, wherein, The control unit controls the operation of one or both of the conversion unit and the rectifier unit by performing feedback control based on the voltage of the first power terminal.

9. The power conversion device according to any one of claims 1 to 8, wherein, The control unit terminates control for the predetermined period when the voltage at the first power terminal exceeds a predetermined voltage.

10. The power conversion device according to any one of claims 1 to 9, wherein, Further equipped with inductors, The inductor has a first terminal connected to the second node and a second terminal connected to the third node. The second terminal of the first winding is connected to the third node and is also connected to the second node via the inductor.

11. The power conversion device according to claim 10, wherein, It further includes a first diode and a second diode. The first diode has a cathode connected to the first power node and an anode connected to the third node. The second diode has a cathode connected to the third node and an anode connected to the second power node. The control unit controls the operation of the third and fourth switching elements among the first, second, third, and fourth switching elements of the switching unit during the predetermined period.

12. The power conversion device according to claim 1, wherein, The rectifier section further includes a Zener diode. The Zener diode is positioned on the path connecting the third power node and the fourth power node.

13. The power conversion device according to claim 2, wherein, The rectifier section further includes a first Zener diode and a second Zener diode. The first Zener diode is disposed on the path connecting the sixth node and the fourth power node. The second Zener diode is disposed on the path connecting the seventh node and the fourth power node.

14. The power conversion device according to any one of claims 1 to 11, wherein, Equipped with a choke transformer and a third diode, The choke transformer has a first winding and a second winding. The second winding of the choke transformer constitutes the choke coil. The first winding of the choke transformer and the third diode are arranged on the path connecting the first power node and the second power node. The second winding of the choke transformer is disposed on the path connecting the rectifier section and the third terminal.

15. The power conversion device according to claim 14, wherein, Further, it has a switch. The first winding of the choke transformer, the third diode, and the switch are arranged on the path connecting the first power node and the second power node. The switch is in the on state during the specified period.

16. The power conversion device according to any one of claims 1 to 11, wherein, It further includes a choke transformer and a third diode. The choke transformer has a first winding and a second winding. The second winding of the choke transformer constitutes the choke coil. The first winding of the choke transformer and the third diode are arranged on the path connecting the third terminal and the fourth terminal. The second winding of the choke transformer is disposed on the path connecting the rectifier section and the third terminal.

17. The power conversion device according to claim 16, wherein, Further, it has a switch. The first winding of the choke transformer, the third diode, and the switch are arranged on the path connecting the third terminal and the fourth terminal. The switch is in the on state during the specified period.

18. The power conversion device according to any one of claims 1 to 17, wherein, The first terminal and the second terminal are connected to a capacitor.

19. A power conversion system, comprising: The first battery has a first terminal and a second terminal; A capacitor has a first terminal and a second terminal; A first switch is disposed on the path connecting the first terminal of the first battery and the first terminal of the capacitor; The second switch is disposed on the path connecting the second terminal of the first battery and the second terminal of the capacitor; Power conversion device; as well as Second battery, The power conversion device has: A first power terminal has a first wiring terminal and a second wiring terminal, wherein the first wiring terminal is connected to the first terminal of the capacitor, and the second wiring terminal is connected to the second terminal of the capacitor; The switching unit includes a first switching element, a second switching element, a third switching element, and a fourth switching element. The first switching element is disposed on the path connecting the first power node and the first terminal, and the first power node is led to the first terminal. The second switching element is disposed on the path connecting the first node and the second power node, and the second power node is led to the second terminal. The third switching element is disposed on the path connecting the first power node and the second node. The fourth switching element is disposed on the path connecting the second node and the second power node. A transformer has a first winding and a second winding, the first winding having a first terminal and a second terminal, the first terminal being connected to a first node and the second terminal being connected to a second node; The rectifier section is connected to the second winding and has multiple switching elements; A smooth section with a choke ring connected to the rectifier section; A second power terminal, guided to the smooth portion and connected to the second battery, has a third terminal and a fourth terminal; and The control unit controls the operation of the first switching element, the second switching element, the third switching element, the fourth switching element, and the plurality of switching elements. The control unit controls the operation of the conversion unit and the rectifier unit during a predetermined period to supply power from the second power terminal to the first power terminal, wherein the predetermined period is the period preceding the period during which power is supplied from the first power terminal to the second power terminal. The control unit operates the converter with a first duty cycle and the rectifier with a second duty cycle during the predetermined period. The first duty cycle is greater than 0 and less than or equal to the second duty cycle. The second winding has a first terminal and a second terminal, the first terminal being connected to a fourth node and the second terminal being connected to a fifth node. The plurality of switching elements in the rectifier section includes a fifth switching element, a sixth switching element, a seventh switching element, and an eighth switching element. The fifth switching element is disposed on the path connecting the third power node and the fourth power node, with the third power node leading to the third terminal. The sixth switching element is disposed on the path connecting the fourth power node and the fourth terminal. The seventh switching element is disposed on the path connecting the third power node and the fifth node. The eighth switching element is disposed on the path connecting the fifth node and the fourth power node. The control unit sequentially performs the first control, the second control, the third control, the fourth control, the fifth control, and the sixth control during the predetermined period. In the first control, the control unit sets the third, fifth, and eighth switching elements to the on state, and sets the first, second, fourth, sixth, and seventh switching elements to the off state. In the second control, the control unit sets the fifth and eighth switching elements to the ON state, and sets the first, second, third, fourth, sixth, and seventh switching elements to the OFF state. In the third control, the control unit sets the first switching element, the second switching element, the third switching element, the fourth switching element, the fifth switching element, the sixth switching element, the seventh switching element, and the eighth switching element to the off state. In the fourth control, the control unit sets the fourth, sixth, and seventh switching elements to the on state, and sets the first, second, third, fifth, and eighth switching elements to the off state. In the fifth control, the control unit sets the sixth and seventh switching elements to the ON state, and sets the first, second, third, fourth, fifth, and eighth switching elements to the OFF state. In the sixth control, the control unit sets the first switching element, the second switching element, the third switching element, the fourth switching element, the fifth switching element, the sixth switching element, the seventh switching element, and the eighth switching element to the off state.

20. A power conversion system, comprising: The first battery has a first terminal and a second terminal; A capacitor has a first terminal and a second terminal; A first switch is disposed on the path connecting the first terminal of the first battery and the first terminal of the capacitor; The second switch is disposed on the path connecting the second terminal of the first battery and the second terminal of the capacitor; Power conversion device; as well as Second battery, The power conversion device has: A first power terminal has a first wiring terminal and a second wiring terminal, wherein the first wiring terminal is connected to the first terminal of the capacitor, and the second wiring terminal is connected to the second terminal of the capacitor; The switching unit includes a first switching element, a second switching element, a third switching element, and a fourth switching element. The first switching element is disposed on the path connecting the first power node and the first terminal, and the first power node is led to the first terminal. The second switching element is disposed on the path connecting the first node and the second power node, and the second power node is led to the second terminal. The third switching element is disposed on the path connecting the first power node and the second node. The fourth switching element is disposed on the path connecting the second node and the second power node. A transformer has a first winding, a second winding and a third winding. The first winding has a first terminal and a second terminal. The first terminal is connected to a first node and the second terminal is connected to a second node. The rectifier section is connected to the second winding and the third winding, and has multiple switching elements; A smooth section with a choke ring connected to the rectifier section; A second power terminal, guided to the smooth portion and connected to the second battery, has a third terminal and a fourth terminal; and The control unit controls the operation of the first switching element, the second switching element, the third switching element, the fourth switching element, and the plurality of switching elements. The control unit controls the operation of the conversion unit and the rectifier unit during a predetermined period to supply power from the second power terminal to the first power terminal, wherein the predetermined period is the period preceding the period during which power is supplied from the first power terminal to the second power terminal. The control unit operates the converter with a first duty cycle and the rectifier with a second duty cycle during the predetermined period. The first duty cycle is greater than 0 and less than or equal to the second duty cycle. The second winding has a first terminal connected to a third power node and a second terminal connected to a sixth node, the third power node being led to the third terminal. The third winding has a first terminal connected to the third power node and a second terminal connected to the seventh node. The plurality of switching elements in the rectifier section includes a ninth switching element and a tenth switching element. The ninth switching element is disposed on the path connecting the sixth node and the fourth power node, the fourth power node being led to the fourth terminal. The tenth switching element is disposed on the path connecting the seventh node and the fourth power node. The control unit sequentially performs the first control, the second control, the third control, the fourth control, the fifth control, and the sixth control during the predetermined period. In the first control, the control unit sets the third and ninth switching elements to the on state, and sets the first, second, fourth, and tenth switching elements to the off state. In the second control, the control unit sets the ninth switching element to the ON state and sets the first switching element, the second switching element, the third switching element, the fourth switching element, and the tenth switching element to the OFF state. In the third control, the control unit sets the first switching element, the second switching element, the third switching element, the fourth switching element, the ninth switching element, and the tenth switching element to the off state. In the fourth control, the control unit sets the fourth and tenth switching elements to the ON state, and sets the first, second, third, and ninth switching elements to the OFF state. In the fifth control, the control unit sets the tenth switching element to the on state and sets the first switching element, the second switching element, the third switching element, the fourth switching element, and the ninth switching element to the off state. In the sixth control, the control unit sets the first switching element, the second switching element, the third switching element, the fourth switching element, the ninth switching element, and the tenth switching element to the off state.

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