Power conversion device and power conversion system

Abstract

To provide a power conversion device capable of effectively diagnosing a voltage detection circuit.SOLUTION: A power conversion device according to an embodiment of the present disclosure includes a first power terminal, a first switching circuit, a first transformer, a first rectifier circuit, a smoothing circuit, a second power terminal, a voltage detection circuit capable of applying a predetermined voltage to a second node in a signal path connecting an input node connected to a first node in the power conversion device and an output node from which a voltage corresponding to a voltage at the first node is output, and a control circuit. The control circuit is capable of controlling the switching operation so as to supply power from the second power terminal toward the first power terminal in a second period before the first period, is capable of controlling an operation of the voltage detection circuit so as to apply a predetermined voltage to the second node in a third period before the second period, and is capable of diagnosing the voltage detection circuit based on a voltage of the output node of the voltage detection circuit in the third period.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Some power conversion devices perform a precharge operation when the system is started. For example, Patent Document 1 discloses a power conversion device that performs a precharge operation to charge a smoothing capacitor. After starting the precharge operation, this power conversion device diagnoses a voltage sensor that detects the voltage of the smoothing capacitor based on the voltage of the smoothing capacitor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-157662 Summary of the Invention [Problem to be solved by the invention]

[0004] In a power conversion device, it is desirable to be able to effectively diagnose a voltage detection circuit, and more effective diagnosis of the voltage detection circuit is expected.

[0005] It is desirable to provide a power conversion device and a power conversion system that can effectively diagnose a voltage detection circuit. [Means for solving the problem]

[0006] A power conversion device according to one embodiment of the present invention includes a first power terminal, a first switching circuit, a first transformer, a first rectifier circuit, a smoothing circuit, a second power terminal, a voltage detection circuit, and a control circuit. The first switching circuit is connected to the first power terminal and is capable of performing a switching operation. The first transformer has a first winding connected to the first switching circuit and a second winding. The first rectifier circuit is capable of rectifying a voltage supplied from the second winding of the first transformer by performing a switching operation. The smoothing circuit is connected to the first rectifier circuit. The second power terminal is connected to the smoothing circuit. The voltage detection circuit has an input node connected to a first node in the power conversion device itself and an output node that outputs a voltage corresponding to the voltage at the first node, and is capable of applying a predetermined voltage to a second node in a signal path connecting the input node and the output node. The control circuit is capable of controlling the operation of the voltage detection circuit, the first switching circuit, and the first rectifier circuit. The control circuit is capable of controlling the switching operation of the first switching circuit and the switching operation of the first rectifier circuit so as to supply power from the second power terminal to the first power terminal during a second period before a first period in which power is supplied from the first power terminal to the second power terminal, and is capable of controlling the operation of the voltage detection circuit so as to apply a predetermined voltage to the second node during a third period before the second period, and is capable of diagnosing the voltage detection circuit based on the voltage of the output node of the voltage detection circuit during the third period.

[0007] A power conversion system according to one embodiment of the present invention includes a first battery, a capacitor, a first switch, a second switch, a power conversion device, and a second battery. The first battery has a first terminal and a second terminal. The capacitor has a first terminal and a second terminal. The first switch is provided in a path connecting the first terminal of the first battery and the first terminal of the capacitor. The second switch is provided in a path connecting the second terminal of the first battery and the second terminal of the capacitor. The power conversion device includes a first power terminal, a first switching circuit, a first transformer, a first rectifier circuit, a smoothing circuit, a second power terminal, a voltage detection circuit, and a control circuit. The first power terminal has a first connection terminal connected to the first terminal of the capacitor and a second connection terminal connected to the second terminal of the capacitor. The first switching circuit is connected to the first power terminal and is capable of performing a switching operation. The first transformer has a first winding connected to a first switching circuit and a second winding. The first rectifier circuit is capable of rectifying a voltage supplied from the second winding of the first transformer by performing a switching operation. The smoothing circuit is connected to the first rectifier circuit. The second power terminal is connected to the smoothing circuit and to a second battery. The voltage detection circuit has an input node connected to a first node in the power conversion device and an output node from which a voltage corresponding to the voltage at the first node is output, and is capable of detecting the voltage at the first node and applying a predetermined voltage to a second node in a signal path connecting the input node and the output node. The control circuit is capable of controlling the operations of the voltage detection circuit, the first switching circuit, and the first rectifier circuit.The control circuit is capable of controlling the switching operation of the first switching circuit and the switching operation of the first rectifier circuit so as to supply power from the second power terminal to the first power terminal during a second period before a first period in which power is supplied from the first power terminal to the second power terminal, and is capable of controlling the operation of the voltage detection circuit so as to apply a predetermined voltage to the second node during a third period before the second period, and is capable of diagnosing the voltage detection circuit based on the voltage of the output node of the voltage detection circuit during the third period. [Effects of the Invention]

[0008] According to the power conversion device and power conversion system according to an embodiment of the present invention, the voltage detection circuit can be diagnosed effectively. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a circuit diagram showing an example of the configuration of a power conversion system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing an example of the configuration of the auxiliary power supply circuit shown in FIG. [Figure 3] FIG. 3 is an explanatory diagram illustrating an example of a precharge operation in the power conversion system shown in FIG. [Figure 4] FIG. 4 is a timing waveform diagram showing an example of an operation for diagnosing the power detection circuit shown in FIG. [Figure 5] FIG. 5 is a circuit diagram illustrating an example of the configuration of a power conversion system according to a modified example. [Figure 6] FIG. 6 is a block diagram showing an example of the configuration of the auxiliary power supply circuit shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] <Embodiment> [Configuration example] 1 shows an example of the configuration of a power conversion system 1 including a power conversion device according to an embodiment of the present invention. The power conversion system 1 includes a high-voltage battery BH, switches SW1 and SW2, a capacitor 9, a power conversion device 10, and a low-voltage battery BL. The power conversion system 1 is configured to convert power supplied from the high-voltage battery BH and supply the converted power to the low-voltage battery BL.

[0012] The high-voltage battery BH is configured to store electric power and supplies the electric power to the power conversion device 10 via the switches SW1 and SW2.

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

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

[0015] The power conversion device 10 is configured to convert power by stepping down the voltage supplied from the high-voltage battery BH and supply the converted power to the low-voltage battery BL. The power conversion device 10 has terminals T11 and T12, a switching circuit 12, a transformer 13, a rectifier circuit 14, a smoothing circuit 15, a voltage sensor 18, an auxiliary power supply circuit 20, drive circuits 32 and 34, a control circuit 40, and terminals T21 and T22. The high-voltage battery BH, switches SW1 and SW2, capacitor 9, switching circuit 12, and drive circuit 32 constitute a primary circuit of the power conversion system 1, and the rectifier circuit 14, smoothing circuit 15, voltage sensor 18, drive circuit 34, and low-voltage battery BL constitute a secondary circuit of the power conversion system 1.

[0016] Terminals T11 and T12 are configured to receive a voltage from a high-voltage battery BH when switches SW1 and SW2 are turned on. Within the power conversion device 10, terminal T11 is connected to a voltage line L11, and terminal T12 is connected to a reference voltage line L12. The voltage on voltage line L11 relative to the voltage on reference voltage line L12 is voltage VH.

[0017] The switching circuit 12 is configured to convert a DC voltage supplied from the high-voltage battery BH into an AC voltage. The switching circuit 12 is a full-bridge circuit and includes transistors S1 to S4. The transistors S1 to S4 are switching elements that perform switching operations based on gate signals GA to GD, respectively. The transistors S1 to S4 are configured using, for example, N-type field effect transistors (FETs). Each of the transistors S1 to S4 has a body diode. For example, the anode of the body diode of the transistor S1 is connected to the source of the body of the transistor S1, and the cathode is connected to the drain of the body of the transistor S1. The same applies to the transistors S2 to S4. Note that this configuration is not limited to this, and for example, a diode element may be externally connected between the drain and source of each of the transistors S1 to S4. Furthermore, although N-type field effect transistors are used in this example, any switching element may be used.

[0018] The transistor S1 is provided in a path connecting the voltage line L11 and the node N1, and is configured to connect the node N1 to the voltage line L11 when it is turned on. The drain of the transistor S1 is connected to the voltage line L11, the gate is supplied with a gate signal GA, and the source is connected to the node N1. The transistor S2 is provided in a path connecting the node N1 and the reference voltage line L12, and is configured to connect the node N1 to the reference voltage line L12 when it is turned on. The drain of the transistor S2 is connected to the node N1, the gate is supplied with a gate signal GB, and the source is connected to the reference voltage line L12.

[0019] The transistor S3 is provided in a path connecting the voltage line L11 and the node N2, and is configured to connect the node N2 to the voltage line L11 when turned on. The drain of the transistor S3 is connected to the voltage line L11, the gate is supplied with a gate signal GC, and the source is connected to the node N2. The transistor S4 is provided in a path connecting the node N2 and the reference voltage line L12, and is configured to connect the node N2 to the reference voltage line L12 when turned on. The drain of the transistor S4 is connected to the node N2, the gate is supplied with a gate signal GD, and the source is connected to the reference voltage line L12.

[0020] Transformer 13 is configured to insulate the primary side circuit from the secondary side circuit in terms of DC current and connect them in terms of AC current, convert the AC voltage supplied from the primary side circuit at a transformation ratio N of transformer 13, and supply the converted AC voltage to the secondary side circuit. Transformer 13 has windings 13A and 13B. Winding 13A is a primary winding, and one end is connected to a node N1 in switching circuit 12, and the other end is connected to a node N2 in switching circuit 12. Winding 13B is a secondary winding, and one end is connected to a node N4 (described later) in rectifier circuit 14, and the other end is connected to a node N5 (described later) in rectifier circuit 14.

[0021] The rectifier circuit 14 is configured to rectify the AC voltage supplied from the winding 13B of the transformer 13. The rectifier circuit 14 is a full-bridge circuit and includes transistors S5 to S8. The transistors S5 to S8 are configured to perform switching operations based on gate signals GE and GF. Like the transistors S1 to S4 of the switching circuit 12, the transistors S5 to S8 are configured using, for example, N-type field effect transistors. Like the transistors S1 to S4, each of the transistors S5 to S8 has a body diode.

[0022] Transistor S5 is provided in a path connecting voltage line L21A and node N4, and is configured to connect node N4 to voltage line L21A when turned on. The drain of transistor S5 is connected to voltage line L21A, a gate signal GF is supplied to its gate, and a source is connected to node N4. Transistor S6 is provided in a path connecting node N4 and reference voltage line L22, and is configured to connect node N4 to reference voltage line L22 when turned on. The drain of transistor S6 is connected to node N4, a gate signal GE is supplied to its gate, and a source is connected to reference voltage line L22.

[0023] Transistor S7 is provided in a path connecting voltage line L21A and node N5, and is configured to connect node N5 to voltage line L21A when turned on. The drain of transistor S7 is connected to voltage line L21A, a gate signal GE is supplied to its gate, and a source is connected to node N5. Transistor S8 is provided in a path connecting node N5 and reference voltage line L22, and is configured to connect node N5 to reference voltage line L22 when turned on. The drain of transistor S8 is connected to node N5, a gate signal GF is supplied to its gate, and a source is connected to reference voltage line L22.

[0024] The smoothing circuit 15 is configured to smooth the voltage rectified by the rectifier circuit 14. The smoothing circuit 15 has a choke inductor 16 and a capacitor 17. One end of the choke inductor 16 is connected to the voltage line L21A, and the other end is connected to the voltage line L21B. One end of the capacitor 17 is connected to the voltage line L21B, and the other end is connected to the reference voltage line L22. Note that in this example, the choke inductor 16 is provided on the voltage lines L21A and L21B, but this is not limiting and instead, the choke inductor 16 may be provided on the reference voltage line L22, for example.

[0025] The voltage sensor 18 is configured to detect the voltage on the voltage line L21B. One end of the voltage sensor 18 is connected to the voltage line L21B, and the other end is connected to the reference voltage line L22. The voltage on the voltage line L21B relative to the voltage on the reference voltage line L22 is a voltage VL. The voltage sensor 18 detects this voltage VL and supplies a detected voltage VL2 corresponding to this voltage VL to the control circuit 40.

[0026] The auxiliary power supply circuit 20 is configured to generate various power supply voltages used within the power conversion device 10 based on the voltages VH and VL, and also to generate a detection voltage VH2 proportional to the voltage VH.

[0027] 2 shows an example configuration of the auxiliary power supply circuit 20. The auxiliary power supply circuit 20 has a switching element 21, a switching control circuit 22, a transformer 23, a rectifier circuit 24, a smoothing circuit 25, a rectifier circuit 26, a smoothing circuit 27, a regulator 28, a rectifier circuit 61, a diode 62, a peak hold circuit 63, and a voltage divider circuit 64. The switching element 21, the switching control circuit 22, the transformer 23, the rectifier circuit 61, the diode 62, the peak hold circuit 63, and the voltage divider circuit 64 constitute a voltage detection circuit 60.

[0028] One end of the switching element 21 is connected to a winding 23A (described later) of the transformer 23, and the other end is connected to a terminal T12. The switching control circuit 22 is configured to control the operation of the switching element 21. The switching element 21 and the switching control circuit 22 form a switching circuit 29.

[0029] The transformer 23 has windings 23A, 23B, 23C, and 23D. The windings 23A and 23B are primary windings, and the windings 23C and 23D are secondary windings. One end of the winding 23A is connected to a terminal T11, and the other end is connected to one end of the switching element 21. Both ends of the winding 23B are connected to a rectifier circuit 24. One end of the winding 23B is connected to a terminal T12. Both ends of the winding 23C are connected to a rectifier circuit 26. Both ends of the winding 23D are connected to a rectifier circuit 61. One end of the winding 23C and one end of the winding 23D are connected to a terminal T22.

[0030] Rectifier circuit 24 is configured to rectify the AC voltage output from winding 23B of transformer 23. Auxiliary power supply circuit 20 transmits a pulse voltage generated by switching element 21 performing a switching operation from winding 23A to winding 23B. Winding 23B and rectifier circuit 24 transmit power using a flyback method. Smoothing circuit 25 is configured to smooth the voltage rectified by rectifier circuit 24 and output the smoothed DC voltage as power supply voltage VP. As shown in FIG. 1, auxiliary power supply circuit 20 supplies this power supply voltage VP to drive circuit 32.

[0031] Rectifier circuit 26 is configured to rectify the AC voltage output from winding 23C of transformer 23. Auxiliary power supply circuit 20 transmits a pulse voltage generated by switching element 21 performing a switching operation from winding 23A to winding 23C. Winding 23C and rectifier circuit 26 transmit power using a flyback method. Smoothing circuit 27 is configured to smooth the voltage rectified by rectifier circuit 26 and output the smoothed DC voltage as voltage V1.

[0032] The regulator 28 is configured to generate a power supply voltage VDD based on one of the voltages V1 and VL. Specifically, when the voltage V1 is lower than a desired voltage, the regulator 28 generates the power supply voltage VDD based on the voltage VL. When the voltage V1 is equal to the desired voltage, the regulator 28 generates the power supply voltage VDD based on the voltage V1. The auxiliary power supply circuit 20 then supplies the power supply voltage VDD to the control circuit 40, as shown in FIG. 1.

[0033] The rectifier circuit 61 is configured to rectify the AC voltage output from the winding 23D of the transformer 23. The auxiliary power supply circuit 20 transmits a pulse voltage generated by the switching operation of the switching element 21 from the winding 23A to the winding 23D. The winding 23D and the rectifier circuit 61 transmit power in a forward manner. A control signal TE generated by the control circuit 40 is supplied to the anode of the diode 62, and the cathode is connected to a node NA, which is the output node of the rectifier circuit 61. The control signal TE is, for example, a signal that transitions between a power supply voltage VDD and a ground voltage VGND of the control circuit 40. The peak hold circuit 63 is configured to perform a peak hold operation based on the voltage at the node NA, thereby generating a voltage corresponding to the peak value of the output voltage of the rectifier circuit 61. The voltage divider circuit 64 is configured to divide the output voltage of the peak hold circuit 63 to generate a detection voltage VH2. This detection voltage VH2 is a voltage proportional to the voltage VH. As shown in FIG. 1, the auxiliary power supply circuit 20 supplies the detected voltage VH2 to the control circuit 40.

[0034] The drive circuit 32 (FIG. 1) operates based on the power supply voltage VP supplied from the auxiliary power supply circuit 20, and is configured to generate the gate signals GA to GD based on the gate signals GA1 to GD1 supplied from the control circuit 40, respectively.

[0035] The drive circuit 34 is configured to operate using the voltage VL as a power supply voltage and to generate the gate signals GE and GF based on the gate signals GE1 and GF1 supplied from the control circuit 40. In this example, the drive circuit 34 is configured to operate using the voltage VL as a power supply voltage, but this is not limited thereto, and the drive circuit 34 may operate based on the power supply voltage VDD generated by the auxiliary power supply circuit 20.

[0036] The control circuit 40 is configured to control the operation of the power conversion device 10 by controlling the operation of the switching circuit 12 and the rectifier circuit 14 based on the detection voltage VH2 supplied from the auxiliary power supply circuit 20, the detection voltage VL2 supplied from the voltage sensor 18, and control data CTL supplied from a system control unit (not shown). Specifically, the control circuit 40 generates gate signals GA1 to GF1 based on the detection voltages VH2 and VL2, and controls the operation of the power conversion device 10 by performing PWM (Pulse Width Modulation) control using these gate signals GA1 to GF1. As will be described later, the control circuit 40 is also configured to diagnose the voltage detection circuit 60 based on the detection voltage VH2 using a control signal TE. The control circuit 40 operates based on the power supply voltage VDD supplied from the auxiliary power supply circuit 20. The control circuit 40 is configured using, for example, a microcontroller.

[0037] The terminals T21 and T22 are configured to supply the voltage generated by the power conversion device 10 to the low-voltage battery BL. Within the power conversion device 10, the terminal T21 is connected to the voltage line L21B, and the terminal T22 is connected to the reference voltage line L22. Furthermore, the terminal T21 is connected to the positive terminal of the low-voltage battery BL, and the terminal T22 is connected to the negative terminal of the low-voltage battery BL.

[0038] The low-voltage battery BL is configured to store the power supplied from the power conversion device 10.

[0039] With this configuration, the power conversion system 1 performs a power conversion operation of converting the power supplied from the high-voltage battery BH and supplying the converted power to the low-voltage battery BL.

[0040] The power conversion system 1 also has a function of performing a so-called precharge operation, which charges the capacitor 9 before starting such a power conversion operation. In this precharge operation, the switches SW1 and SW2 are in the off state, and the control circuit 40 controls the operation of the switching circuit 12 and the rectifier circuit 14, so that the power conversion system 1 supplies power from the low-voltage battery BL to the capacitor 9. This makes it possible for the power conversion device 10 to suppress inrush current flowing from the high-voltage battery BH to the capacitor 9 when the switches SW1 and SW2 are turned on to perform the power conversion operation.

[0041] Here, terminals T11 and T12 correspond to a specific example of a "first power terminal" in an embodiment of the present disclosure. Switching circuit 12 corresponds to a specific example of a "first switching circuit" in an embodiment of the present disclosure. Transformer 13 corresponds to a specific example of a "first transformer" in an embodiment of the present disclosure. Winding 13A corresponds to a specific example of a "first winding" of the "first transformer" in an embodiment of the present disclosure. Winding 13B corresponds to a specific example of a "second winding" of the "first transformer" in an embodiment of the present disclosure. Rectifier circuit 14 corresponds to a specific example of a "first rectifier circuit" in an embodiment of the present disclosure. Smoothing circuit 15 corresponds to a specific example of a "smoothing circuit" in an embodiment of the present disclosure. Terminals T21 and T22 correspond to a specific example of a "second power terminal" in an embodiment of the present disclosure. Voltage detection circuit 60 corresponds to a specific example of a "voltage detection circuit" in an embodiment of the present disclosure. The node of the terminal T11 corresponds to a specific example of a "first node" in an embodiment of the present disclosure. The node NA corresponds to a specific example of a "second node" in an embodiment of the present disclosure. The control circuit 40 corresponds to a specific example of a "control circuit" in an embodiment of the present disclosure.

[0042] The switching circuit 29 corresponds to a specific example of a "second switching circuit" in an embodiment of the present disclosure. The transformer 23 corresponds to a specific example of a "second transformer" in an embodiment of the present disclosure. The winding 23A corresponds to a specific example of a "first winding" of the "second transformer" in an embodiment of the present disclosure. The winding 23D corresponds to a specific example of a "second winding" of the "second transformer" in an embodiment of the present disclosure. The rectifier circuit 61 corresponds to a specific example of a "second rectifier circuit" in an embodiment of the present disclosure. The peak hold circuit 63 corresponds to a specific example of a "peak hold circuit" in an embodiment of the present disclosure. The diode 62 corresponds to a specific example of a "diode" in an embodiment of the present disclosure.

[0043] The high-voltage battery BH corresponds to a specific example of a "first battery" in an embodiment of the present disclosure. The capacitor 9 corresponds to a specific example of a "capacitor" in an embodiment of the present disclosure. The switch SW1 corresponds to a specific example of a "first switch" in an embodiment of the present disclosure. The switch SW2 corresponds to a specific example of a "second switch" in an embodiment of the present disclosure. The terminal T11 corresponds to a specific example of a "first connection terminal" in an embodiment of the present disclosure. The terminal T12 corresponds to a specific example of a "second connection terminal" in an embodiment of the present disclosure. The low-voltage battery BL corresponds to a specific example of a "second battery" in an embodiment of the present disclosure.

[0044] [Actions and Actions] Next, the operation and function of the power conversion system 1 of this embodiment will be described.

[0045] (Overview of overall operation) First, referring to FIG. 1, an overview of the overall operation of the power conversion system 1 will be described. When the power conversion system 1 starts, the switches SW1 and SW2 are in the off state. When the power conversion system 1 starts, the switching circuit 29 of the auxiliary power supply circuit 20 begins switching operation to generate power supply voltages VP and VDD, as well as a detection voltage VH2 proportional to the voltage VH. During the precharge period, the control circuit 40 generates gate signals GA1 to GF1 based on the detection voltage VH2, a detection voltage VL2 corresponding to the voltage VL, and control data CTL. The power conversion device 10 performs switching operation based on gate signals GA to GF corresponding to the gate signals GA1 to GF1, and supplies power from the low-voltage battery BL to the capacitor 9. As a result, the capacitor 9 is charged, and the voltage VH increases and is maintained near the voltage indicated by the target voltage command value VHtarget. Then, during the power conversion period, the switches SW1 and SW2 are turned on, and the control circuit 40 generates the gate signals GA1 to GF1 based on the detection voltages VH2 and VL2. The power conversion device 10 performs switching operations based on gate signals GA to GF corresponding to gate signals GA1 to GF1, converts the power supplied from the high-voltage battery BH, and supplies the converted power to the low-voltage battery BL.

[0046] (Detailed operation) FIG. 3 shows an example of a precharge operation in the power conversion system 1. As shown in FIG.

[0047] The control circuit 40 generates the thresholds THtop and THbot so that they gradually increase during the precharge period P2 during which the precharge operation is performed. In this example, the control circuit 40 linearly increases the threshold THtop over time from timing t1 when the precharge period P2 starts, and stops changing the threshold THtop from timing t6 onward. The value of the threshold THtop from timing t6 onward is the target voltage command value VHtarget. In this example, the value of the threshold THtop is set to the same value as the target voltage command value VHtarget from timing t5 onward. However, this is not limited to this. For example, the value may be a value obtained by adding a value ΔV to the target voltage command value VHtarget (VHtarget+ΔV). Here, ΔV is an arbitrary value corresponding to the target voltage command value VHtarget. Furthermore, the control circuit 40 linearly increases the threshold THbot over time from timing t2 onward, which is after timing t1, and stops changing the threshold THbot from timing t7 onward, which is after timing t6.

[0048] During the precharge period P2, the control circuit 40 controls the operation of the power conversion device 10 so that the voltage VH is within a voltage range between the thresholds THbot and THtop. Specifically, the control circuit 40 sets the duty ratios of the switching circuit 12 and the rectifier circuit 14 so as to increase the voltage VH during the period from timing t1 to t3. When the voltage VH reaches the threshold THtop at timing t3, the control circuit 40 sets the duty ratios of the switching circuit 12 and the rectifier circuit 14 so as to decrease the voltage VH during the period from timing t3 to t4. When the voltage VH reaches the threshold THbot at timing t4, the control circuit 40 sets the duty ratios of the switching circuit 12 and the rectifier circuit 14 so as to increase the voltage VH during the period from timing t4 to t5. The control circuit 40 repeats this operation from timing t5 onwards. In this way, during the precharge period P2, the voltage VH increases toward the target voltage command value VHtarget, and in this example, at timing t8, the voltage VH reaches the target voltage command value VHtarget. Then, during the period after the precharge period P2, the voltage VH is maintained near the target voltage command value VHtarget.

[0049] Then, the switches SW1 and SW2 are turned on, connecting the high-voltage battery BH to the capacitor 9. This starts a period during which the power conversion operation is performed (power conversion period) in the power conversion system 1. During this power conversion period, the power conversion system 1 converts the power supplied from the high-voltage battery BH and supplies the converted power to the low-voltage battery BL.

[0050] (Regarding diagnosis of the voltage detection circuit 60) During the period before the precharge period P2, the control circuit 40 diagnoses the voltage detection circuit 60. This operation will be described below.

[0051] FIG. 4 shows an example of the operation of diagnosing the voltage detection circuit 60, where (A) shows the waveform of the voltage VH, (B) shows the waveform of the control signal TE, and (C) shows the waveform of the detection voltage VH2.

[0052] Before the precharge period P2, the voltage VH is 0V (FIG. 4A). As a result, the voltage of the node NA, which is the output node of the rectifier circuit 61 in the auxiliary power supply circuit 20, is the ground voltage VGND. The regulator 28 of the auxiliary power supply circuit 20 generates the power supply voltage VDD based on the voltage VL. The control circuit 40 operates based on this power supply voltage VDD.

[0053] At timing t11, which is before the precharge period P2, the control circuit 40 changes the voltage of the control signal TE from the ground voltage VGND to the power supply voltage VDD (FIG. 4(B)). As a result, in the auxiliary power supply circuit 20, during the period from timing t11 to t12 (period P3), the diode 62 is turned on, and the voltage of the node NA becomes a voltage corresponding to the power supply voltage VDD. Specifically, the voltage of the node NA is lower than the power supply voltage VDD by the forward effect voltage of the diode 62. As a result, the detection voltage VH2 becomes a voltage corresponding to the voltage of the node NA (FIG. 4(C)).

[0054] Based on this detected voltage VH2, the control circuit 40 diagnoses whether the voltage detection circuit 60 is operating normally. That is, since the voltage of the node NA is known, the detected voltage VH2 is also known. The control circuit 40 diagnoses whether the voltage detection circuit 60 is operating normally by checking whether the detected voltage VH2 is approximately the same as the known voltage.

[0055] Then, at timing t12, the control circuit 40 changes the voltage of the control signal TE from the power supply voltage VDD to the ground voltage VGND (FIG. 4(B)). This turns off the diode 62, and the detection voltage VH2 returns to the same voltage as before timing t11 (FIG. 4(C)).

[0056] Then, in a precharge period P2 after timing t13, the power conversion system 1 performs a precharge operation. This precharge operation increases the voltage VH (FIG. 4(A)), and in response to this increase in voltage VH, the detection voltage VH2 increases (FIG. 4(C)).

[0057] Here, the power conversion period corresponds to a specific example of a "first period" in an embodiment of the present disclosure. The precharge period P2 corresponds to a specific example of a "second period" in an embodiment of the present disclosure. The period P3 corresponds to a specific example of a "third period" in an embodiment of the present disclosure.

[0058] In this way, in the power conversion system 1, a predetermined voltage is applied to the node NA during the period P3 before the precharge period P2, and the voltage detection circuit 60 is diagnosed as to whether it is operating normally based on the detected voltage VH2 at that time. This allows the power conversion system 1 to effectively diagnose the voltage detection circuit 60.

[0059] That is, in the period P3 before the precharge period P2, the voltage VH is 0V, so that, for example, when a predetermined voltage is not applied to the node NA, the detection voltage VH2 is a voltage corresponding to this voltage VH (0V). This detection voltage VH2 is the same as the detection voltage VH2 when the voltage detection circuit 60 is malfunctioning. Therefore, in this case, the voltage detection circuit 60 cannot be diagnosed based on the detection voltage VH2.

[0060] Furthermore, during the precharge period P2, the detection voltage VH2 also rises as the voltage VH rises, so it is possible for the control circuit 40 to diagnose the voltage detection circuit 60 based on this detection voltage VH2. However, in this case, if the voltage detection circuit 60 fails, for example, the timing at which the control circuit 40 detects an abnormality in the voltage detection circuit 60 will be delayed. In other words, there is a possibility that the voltage VH will be at a high voltage by the time the control circuit 40 detects an abnormality in the voltage detection circuit 60.

[0061] In the power conversion system 1 according to the present embodiment, a predetermined voltage is applied to the node NA during a period P3 before the precharge period P2, and the normal operation of the voltage detection circuit 60 is diagnosed based on the detected voltage VH2 at that time. Therefore, the control circuit 40 can detect, for example, an abnormality in the voltage detection circuit 60 before the voltage VH starts to rise. As a result, the power conversion system 1 can effectively diagnose the voltage detection circuit 60.

[0062] As described above, the power conversion system 1 includes first power terminals (terminals T11, T12), a first switching circuit (switching circuit 12) connected to the first power terminals (terminals T11, T12) and capable of performing a switching operation, a first transformer (transformer 13) having a first winding (winding 13A) and a second winding (winding 13B) connected to the first switching circuit, a first rectifier circuit (rectifier circuit 14) capable of rectifying a voltage supplied from the second winding (winding 13B) of the first transformer (transformer 13) by performing a switching operation, and a first rectifier circuit (rectifier circuit 14) capable of rectifying a voltage supplied from the second winding (winding 13B) of the first transformer (transformer 13). the first power terminal (terminals T21, T22) connected to the smoothing circuit 15, an input node connected to a first node (terminal T11 in this example) in the device itself, and an output node from which a voltage corresponding to the voltage at the first node is output, the voltage detection circuit 60 being capable of applying a predetermined voltage to a second node (node ​​NA) in a signal path connecting the input node and the output node, and a control circuit 40 being capable of controlling the operation of the voltage detection circuit 60, a first switching circuit (switching circuit 12), and a first rectifier circuit (rectifier circuit 14). The control circuit 40 is capable of controlling the switching operation of the first switching circuit (switching circuit 12) and the switching operation of the first rectifier circuit (rectifier circuit 14) so ​​that power is supplied from the second power terminal to the first power terminal during a second period (pre-charge period P2) prior to a first period (power conversion period) in which power is supplied from the first power terminal (terminals T11, T12) to the second power terminal (terminals T21, T22). The control circuit 40 is capable of controlling the operation of the voltage detection circuit 60 so that a predetermined voltage is applied to the second node (node ​​NA) during a third period (period P3) prior to the second period (pre-charge period P2). The control circuit 40 is capable of diagnosing the voltage detection circuit 60 based on the voltage (detected voltage VH2) at the output node of the voltage detection circuit 60 during the third period. This allows the control circuit 40 to detect, for example, an abnormality in the voltage detection circuit 60 before the voltage VH begins to rise in the power conversion system 1. Therefore, in the power conversion system 1, the voltage detection circuit 60 can be diagnosed effectively.

[0063] Furthermore, in the power conversion system 1, the first node is the first power terminal (terminals T11, T12), and the control circuit 40 is capable of controlling the switching operation of the first switching circuit (switching circuit 12) and the switching operation of the first rectifier circuit (rectifier circuit 14) based on the voltage at the first power terminal (terminals T11, T12) during the second period (pre-charge period P2). As a result, in the power conversion system 1, after confirming that the voltage detection circuit 60 that detects the voltage VH is normal during the period P3, the pre-charge operation can be performed during the pre-charge period P2 based on the detected voltage VH2 output from this voltage detection circuit 60. Therefore, in the power conversion system 1, the reliability of the pre-charge operation can be improved.

[0064] [effect] As described above, this embodiment includes a first power terminal, a first switching circuit connected to the first power terminal and capable of performing a switching operation, a first transformer having a first winding connected to the first switching circuit and a second winding, a first rectifier circuit capable of rectifying a voltage supplied from the second winding of the first transformer by performing a switching operation, a smoothing circuit connected to the first rectifier circuit, a second power terminal connected to the smoothing circuit, an input node connected to a first node in the device itself, and an output node from which a voltage corresponding to the voltage at the first node is output, a voltage detection circuit capable of applying a predetermined voltage to a second node in a signal path connecting the input node and the output node, and a control circuit capable of controlling the operation of the voltage detection circuit, the first switching circuit, and the first rectifier circuit. The control circuit is capable of controlling the switching operation of the first switching circuit and the switching operation of the first rectifier circuit so that power is supplied from the second power terminal to the first power terminal during a second period prior to a first period in which power is supplied from the first power terminal to the second power terminal. The control circuit is capable of controlling the operation of the voltage detection circuit so that a predetermined voltage is applied to the second node during a third period prior to the second period, and is capable of diagnosing the voltage detection circuit based on the voltage at the output node of the voltage detection circuit during the third period. This allows for effective diagnosis of the voltage detection circuit.

[0065] In this embodiment, the first node is a first power terminal, and the control circuit is capable of controlling the switching operation of the first switching circuit and the switching operation of the first rectifier circuit based on the voltage at the first power terminal during the second period, thereby improving the reliability of the precharge operation.

[0066] [Variation 1] In the above embodiment, as shown in Fig. 2, the voltage detection circuit 60 is provided with the diode 62, but this is not limiting and instead, for example, a switch may be provided. This modification will be described in detail below.

[0067] 5 shows an example of the configuration of a power conversion system 1B according to this modification. The power conversion system 1B includes a power conversion device 10B. The power conversion device 10B includes an auxiliary power supply circuit 20B and a control circuit 40B.

[0068] 6 shows an example of the configuration of an auxiliary power supply circuit 20B. The auxiliary power supply circuit 20B has a switch 65B. That is, while the auxiliary power supply circuit 20 (FIG. 2) according to the above embodiment is provided with a diode 62, the auxiliary power supply circuit 20B according to this modification is provided with a switch 65B instead of the diode 62. The switch 65B is configured to be able to apply a power supply voltage VDD to the node NA based on a control signal TEB generated by the control circuit 40B. The switch 65B is configured using, for example, a transistor.

[0069] The control circuit 40B is configured to control the operation of the power conversion device 10 by controlling the operation of the switching circuit 12 and the rectifier circuit 14 based on the detected voltage VH2 supplied from the auxiliary power supply circuit 20B, the detected voltage VL2 supplied from the voltage sensor 18, and control data CTL supplied from a system control unit (not shown). The control circuit 40B can also diagnose the voltage detection circuit 60B based on the detected voltage VH2 using a control signal TEB.

[0070] Specifically, the control circuit 40B sets the voltage of the control signal TEB to a high level during the period before the precharge period P2. As a result, in the auxiliary power supply circuit 20B, the switch 65B is turned on during this period, and the voltage of the node NA becomes the power supply voltage VDD. As a result, the detection voltage VH2 becomes a voltage corresponding to the voltage of the node NA. Based on this detection voltage VH2, the control circuit 40B can diagnose whether the voltage detection circuit 60B is operating normally.

[0071] [Variation 2] In the above embodiment, the control circuit 40 diagnoses the voltage detection circuit 60 that detects the voltage VH. However, this is not limited to this, and the control circuit 40 may diagnose another voltage detection circuit that detects the voltage of another node in the power conversion device 10. In particular, the present technology can diagnose a voltage detection circuit when the voltage input to the voltage detection circuit is 0 V. For example, before a precharge operation is performed, no power is supplied to the primary side circuit of the power conversion system 1. Therefore, by using the present technology, it is possible to diagnose a voltage detection circuit that detects the voltage of a node in the primary side circuit.

[0072] [Other variations] Two or more of these variations may also be combined.

[0073] Although the present invention has been described above by way of embodiments and modifications, the present invention is not limited to these embodiments and can be modified in various ways.

[0074] For example, in the above embodiment, the voltage detection circuit 60 is diagnosed before the precharge operation begins when the power conversion system 1 is started, but this is not limited to this. The power conversion system 1 may often perform a precharge operation even after starting up. In such a case, the power conversion system 1 may also diagnose the voltage detection circuit 60 before the precharge operation begins.

[0075] For example, in the above embodiment, the voltage step-down operation is performed in the power conversion operation, but this is not limitative, and the voltage step-up operation may also be performed.

[0076] The effects described in this specification are merely examples, and the effects of the present disclosure are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present disclosure.

[0077] Furthermore, the present disclosure may take the following aspects.

[0078] (1) a first power terminal; a first switching circuit connected to the first power terminal and capable of performing a switching operation; a first transformer having a first winding connected to the first switching circuit and a second winding; a first rectifier circuit that performs a switching operation to rectify a voltage supplied from the second winding of the first transformer; a smoothing circuit connected to the first rectifier circuit; a second power terminal connected to the smoothing circuit; a voltage detection circuit having an input node connected to a first node in the device itself and an output node from which a voltage corresponding to the voltage at the first node is output, the voltage detection circuit being capable of applying a predetermined voltage to a second node in a signal path connecting the input node and the output node; a control circuit capable of controlling operations of the voltage detection circuit, the first switching circuit, and the first rectifier circuit; Equipped with The control circuit a switching operation of the first switching circuit and a switching operation of the first rectifier circuit can be controlled so that power is supplied from the second power terminal to the first power terminal during a second period that is before a first period in which power is supplied from the first power terminal to the second power terminal; During a third period before the second period, the operation of the voltage detection circuit can be controlled so as to apply the predetermined voltage to the second node, and the voltage detection circuit can be diagnosed based on the voltage of the output node of the voltage detection circuit during the third period. Power conversion device. (2) the first node is the first power terminal; The control circuit is capable of controlling a switching operation of the first switching circuit and a switching operation of the first rectifier circuit based on a voltage at the first power terminal during the second period. The power conversion device according to (1) above. (3) The voltage detection circuit a second switching circuit connected to the input node and having a switching element capable of performing a switching operation; a second transformer having a first winding connected to the second switching circuit and a second winding; a second rectifier circuit capable of rectifying a voltage supplied from the second winding of the second transformer and outputting the rectified voltage to the second node; a sample-and-hold circuit capable of performing a sample-and-hold operation based on the voltage at the second node; and A voltage corresponding to the output voltage of the sample-and-hold circuit can be output from the output node. The power conversion device according to (1) or (2). (4) the voltage detection circuit includes a diode having an anode and a cathode connected to the second node; The control circuit is capable of controlling the operation of the voltage detection circuit by applying a voltage corresponding to the predetermined voltage to the anode of the diode during the third period. The power conversion device according to any one of (1) to (3). (5) the voltage detection circuit has a switch that, when turned on, can connect a third node to which the predetermined voltage is applied to the second node; The control circuit can control the operation of the voltage detection circuit by turning on the switch during the third period. The power conversion device according to any one of (1) to (4). (6) a first battery having a first terminal and a second terminal; a capacitor having a first terminal and a second terminal; a first switch provided in a path connecting the first terminal of the first battery and the first terminal of the capacitor; a second switch provided in a path connecting the second terminal of the first battery and the second terminal of the capacitor; a power conversion device; Second battery and Equipped with The power conversion device is a first power terminal having a first connection terminal connected to the first terminal of the capacitor and a second connection terminal connected to the second terminal of the capacitor; a first switching circuit connected to the first power terminal and capable of performing a switching operation; a first transformer having a first winding connected to the first switching circuit and a second winding; a first rectifier circuit that performs a switching operation to rectify a voltage supplied from the second winding of the first transformer; a smoothing circuit connected to the first rectifier circuit; a second power terminal connected to the smoothing circuit and to the second battery; a voltage detection circuit having an input node connected to a first node in the power conversion device and an output node from which a voltage corresponding to a voltage at the first node is output, the voltage detection circuit being capable of detecting the voltage at the first node and applying a predetermined voltage to a second node in a signal path connecting the input node and the output node; a control circuit capable of controlling operations of the voltage detection circuit, the first switching circuit, and the first rectifier circuit; and The control circuit a switching operation of the first switching circuit and a switching operation of the first rectifier circuit can be controlled so that power is supplied from the second power terminal to the first power terminal during a second period that is before a first period in which power is supplied from the first power terminal to the second power terminal; During a third period before the second period, the operation of the voltage detection circuit can be controlled so as to apply the predetermined voltage to the second node, and the voltage detection circuit can be diagnosed based on the voltage of the output node of the voltage detection circuit during the third period. Power conversion systems. [Explanation of symbols]

[0079] 1,1B...power conversion system, 9...capacitor, 10,10B...power conversion device, 12...switching circuit, 13...transformer, 13A,13B...winding, 14...rectifier circuit, 15...smoothing circuit, 16...choke inductor, 17...capacitor, 18...voltage sensor, 20,20B...auxiliary power supply circuit, 21...switching element, 22...switching control circuit, 23...transformer, 23A,23B,23C,23D...winding, 24...rectifier circuit, 25...smoothing circuit, 26...rectifier circuit, 27...smoothing circuit, 28...regulator, 29...switching circuit, 32,34...drive circuit, 40,40B...control circuit, 60,60B...voltage detection circuit, 61...rectifier circuit, 62...die ode, 63...peak hold circuit, 64...voltage divider circuit, 65B...switch, BH...high voltage battery, BL...low voltage battery, CTL...control data, GA~GF,GA1~GF1...gate signal, L11...voltage line, L12...reference voltage line, L21A,L21B...voltage line, L22...reference voltage line, NA...node, P2...precharge period, P3...period, S1~S8...transistors, SW1,SW2...switches, T11,T12...terminals, T21,T22...terminals, TE,TEB...control signal, THbot...threshold, THtop...threshold, VDD,VP...power supply voltage, VGND...ground voltage, VH...voltage, VH2...detection voltage, VL...voltage, VL2...detection voltage.

Claims

1. a first power terminal; a first switching circuit connected to the first power terminal and capable of performing a switching operation; a first transformer having a first winding connected to the first switching circuit and a second winding; a first rectifier circuit that performs a switching operation to rectify a voltage supplied from the second winding of the first transformer; a smoothing circuit connected to the first rectifier circuit; a second power terminal connected to the smoothing circuit; a voltage detection circuit having an input node connected to a first node in the device itself and an output node from which a voltage corresponding to the voltage at the first node is output, the voltage detection circuit being capable of applying a predetermined voltage to a second node in a signal path connecting the input node and the output node; a control circuit capable of controlling operations of the voltage detection circuit, the first switching circuit, and the first rectifier circuit; Equipped with The control circuit a switching operation of the first switching circuit and a switching operation of the first rectifier circuit can be controlled so that power is supplied from the second power terminal to the first power terminal during a second period that is before a first period in which power is supplied from the first power terminal to the second power terminal; During a third period before the second period, the operation of the voltage detection circuit can be controlled so as to apply the predetermined voltage to the second node, and the voltage detection circuit can be diagnosed based on the voltage of the output node of the voltage detection circuit during the third period. Power conversion device.

2. the first node is the first power terminal; The control circuit is capable of controlling the switching operation of the first switching circuit and the switching operation of the first rectifier circuit based on the voltage at the first power terminal during the second period. The power conversion device according to claim 1 .

3. The voltage detection circuit a second switching circuit connected to the input node and having a switching element capable of performing a switching operation; a second transformer having a first winding connected to the second switching circuit and a second winding; a second rectifier circuit capable of rectifying a voltage supplied from the second winding of the second transformer and outputting the rectified voltage to the second node; a peak hold circuit capable of performing a peak hold operation based on the voltage at the second node; and A voltage corresponding to the output voltage of the sample-and-hold circuit can be output from the output node. The power conversion device according to claim 1 .

4. the voltage detection circuit includes a diode having an anode and a cathode connected to the second node; The control circuit is capable of controlling the operation of the voltage detection circuit by applying a voltage corresponding to the predetermined voltage to the anode of the diode during the third period. The power conversion device according to claim 1 .

5. the voltage detection circuit has a switch that, when turned on, can connect a third node to which the predetermined voltage is applied to the second node; The control circuit can control the operation of the voltage detection circuit by turning on the switch during the third period. The power conversion device according to claim 1 .

6. a first battery having a first terminal and a second terminal; a capacitor having a first terminal and a second terminal; a first switch provided in a path connecting the first terminal of the first battery and the first terminal of the capacitor; a second switch provided in a path connecting the second terminal of the first battery and the second terminal of the capacitor; a power conversion device; a second battery; Equipped with The power conversion device is a first power terminal having a first connection terminal connected to the first terminal of the capacitor and a second connection terminal connected to the second terminal of the capacitor; a first switching circuit connected to the first power terminal and capable of performing a switching operation; a first transformer having a first winding connected to the first switching circuit and a second winding; a first rectifier circuit that performs a switching operation to rectify a voltage supplied from the second winding of the first transformer; a smoothing circuit connected to the first rectifier circuit; a second power terminal connected to the smoothing circuit and to the second battery; a voltage detection circuit having an input node connected to a first node in the power conversion device and an output node from which a voltage corresponding to a voltage at the first node is output, the voltage detection circuit being capable of detecting the voltage at the first node and applying a predetermined voltage to a second node in a signal path connecting the input node and the output node; a control circuit capable of controlling operations of the voltage detection circuit, the first switching circuit, and the first rectifier circuit; and The control circuit a switching operation of the first switching circuit and a switching operation of the first rectifier circuit can be controlled so that power is supplied from the second power terminal to the first power terminal during a second period that is before a first period in which power is supplied from the first power terminal to the second power terminal; During a third period before the second period, the operation of the voltage detection circuit can be controlled so as to apply the predetermined voltage to the second node, and the voltage detection circuit can be diagnosed based on the voltage of the output node of the voltage detection circuit during the third period. Power conversion systems.

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