Power supply device and method for diagnosing power supply device

Abstract

The power supply device includes a first switch having one end connected to a first DC power supply, a first capacitance connected between the other end of the first switch and a reference potential, a second switch having one end connected to a second DC power supply, and a second capacitance connected between the other end of the second switch and the reference potential. First and second DC / DC converters connected in parallel between the other end of the first switch and the other end of the second switch; and a control unit. The control unit has a step-down operation mode, a step-up operation mode, and a step-up / step-down operation mode. In the buck-boost operation mode, in a state in which the first switch and the second switch are turned off, the first DC / DC converter is caused to step down the voltage of the first capacitance and output the voltage to the second capacitance, and the second DC / DC converter is caused to step up the voltage of the second capacitance and output the voltage to the first capacitance in parallel.

Description

Technical Field

[0001] The present disclosure relates to a power supply device and a method for diagnosing the power supply device, and more particularly to a power supply device that is connected between two DC power supplies and converts voltage. Background Art

[0002] In the past, a power supply device having a DC / DC converter connected between two DC power supplies and converting a voltage has been disclosed (for example, see Patent Document 1). In such a power supply device, a switch is inserted between each of the two DC power supplies and the power supply device for protection. In addition, in order to diagnose the disconnection capability of the switch, the potential difference between the two ends of the switch is measured after the switch is turned into a disconnection state. If the potential difference is greater than a specified value, it is determined that the disconnection capability of the switch is normal, otherwise it is determined that the disconnection capability of the switch is abnormal.

[0003] Prior Art Literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2019 / 077958 Summary of the invention

[0006] In the previous diagnostic method, when charge is accumulated inside the DC / DC converter (hereinafter referred to as "internal charge"), due to the influence of the internal charge, it is necessary to wait for the internal charge to discharge after the switch is turned off, which requires a long waiting time.

[0007] A power supply device according to one embodiment of the present disclosure is configured to be connected to a first DC power supply that supplies and maintains a first voltage and a second DC power supply that supplies and maintains a second voltage lower than the first voltage. The power supply device includes: a first switch configured to be connected to the first DC power supply at one end, a first electrostatic capacitor connected between the other end of the first switch and a reference potential, a second switch configured to be connected to the second DC power supply at one end, a second electrostatic capacitor connected between the other end of the second switch and the reference potential, a first DC / DC converter connected between the other end of the first switch and the other end of the second switch, a second DC / DC converter connected in parallel with the first DC / DC converter between the other end of the first switch and the other end of the second switch, and a control unit configured to control the first switch and the second switch and the first DC / DC converter and the second DC / DC converter. The control unit has a step-down operation mode, a step-up operation mode, and a step-up / step-down operation mode. In the step-down operation mode, step-down control is performed, in which the first DC / DC converter and the second DC / DC converter step down the first voltage supplied from the first DC power supply to the second voltage in parallel and output it to the second DC power supply while the first switch and the second switch are turned on. In the step-up operation mode, step-up control is performed, in which the first DC / DC converter and the second DC / DC converter step up the second voltage supplied from the second DC power supply to the first voltage in parallel and output it to the first DC power supply while the first switch and the second switch are turned on. In the step-up / step-down operation mode, step-up / step-down control is performed, in which the first DC / DC converter step down the voltage of the first electrostatic capacitor and output it to the second electrostatic capacitor while the second DC / DC converter step up the voltage of the second electrostatic capacitor and output it to the first electrostatic capacitor while the first switch and the second switch are turned off.

[0008] In the above-mentioned power supply device diagnosis method involved in one embodiment of the present disclosure, a power supply device is prepared, which includes: a first switch having one end connected to the first DC power supply, a first electrostatic capacitor connected between the other end of the first switch and a reference potential, a second switch having one end connected to the second DC power supply, a second electrostatic capacitor connected between the other end of the second switch and the reference potential, a first DC / DC converter connected between the other end of the first switch and the other end of the second switch, and a second DC / DC converter connected between the other end of the first switch and the other end of the second switch. A step-up / step-down control is performed, in which the first DC / DC converter steps down the voltage of the first electrostatic capacitor and outputs it to the second electrostatic capacitor, and the second DC / DC converter steps up the voltage of the second electrostatic capacitor and outputs it to the first electrostatic capacitor in parallel with the first switch and the second switch being disconnected.

[0009] According to the present disclosure, a power supply device and a power supply device diagnosis method are provided, which are capable of diagnosing the interruption capabilities of switches connected between two DC power supplies and the power supply device in a shorter time than before. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a block diagram showing the configuration of a power supply device according to the embodiment.

[0011] Figure 2 Yes means Figure 1 FIG. 2 is a diagram showing a specific circuit example of a DC / DC converter included in the power supply device shown in FIG.

[0012] Figure 3A Yes means Figure 2 FIG. 2 is a diagram showing the flow of current in the step-down operation mode of the power supply device shown.

[0013] Figure 3B Yes Description Figure 3A FIG. 1 is a diagram showing a failure of a switching element in a step-down operation mode of a power supply device.

[0014] Figure 3C FIG. 1 is a timing chart showing the operation of the first DC / DC converter for explaining an open-circuit failure of the second switching element.

[0015] Figure 4A Yes means Figure 2 FIG. 2 is a diagram showing the flow of current in the voltage step-up operation mode of the power supply device shown.

[0016] Figure 4B Yes Description Figure 4A FIG. 1 is a diagram showing a failure of a switching element in a boost operation mode of a power supply device.

[0017] Figure 4C FIG. 1 is a timing chart showing the operation of the first DC / DC converter for explaining an open-circuit failure of the first switching element.

[0018] Figure 5A Yes means Figure 2 Flowchart of a method for diagnosing a switch in a power supply device shown in FIG.

[0019] Figure 5B Yes means Figure 5A A diagram of a flow chart of the flow of electric current.

[0020] Figure 5C Yes means Figure 2 FIG. 2 is a diagram showing a modified example of the flow of current in diagnosis of a switch in a power supply device shown.

[0021] Fig. 6A Yes means Figure 2 FIG. 1 is a flowchart of a method for detecting a failure of a switching element in a buck-boost operation mode of a power supply device shown in FIG.

[0022] Figure 6B Yes Description Fig. 6A A diagram showing the basis for the determination in the flowchart.

[0023] Figure 6C It means that Fig. 6A In the buck-boost operation mode shown in FIG. 1 , the buck operation and the boost operation of the first DC / DC converter and the second DC / DC converter are switched. Figure 2 FIG. 1 is a flowchart of a method for detecting a failure of a switching element in a buck-boost operation mode of a power supply device shown in FIG.

[0024] Fig.6D Yes Description Figure 6C A diagram showing the basis for the determination in the flowchart.

[0025] Figure 7 It is a block diagram showing the configuration of a power supply device according to Modification 1 of the embodiment.

[0026] Figure 8 It is a block diagram showing the configuration of a power supply device according to Modification 2 of the embodiment.

[0027] Fig. 9 This is a block diagram showing the configuration of a power supply device according to Modification 3 of the embodiment. DETAILED DESCRIPTION

[0028] Hereinafter, the embodiments of the present disclosure are described in detail using the accompanying drawings. In addition, the embodiments described below all represent a specific example of the present disclosure. The numerical values, shapes, materials, constituent elements, configuration positions and connection methods of constituent elements, steps, order of steps, etc. shown in the following embodiments are examples, and are not intended to limit the present disclosure. In addition, each figure is not necessarily a strict illustration. In each figure, the same mark is attached to substantially the same structure, and repeated descriptions are omitted or simplified. In addition, "A and B are connected" means that A and B are electrically connected, including not only the case where A and B are directly connected, but also the case where A and B are indirectly connected in a state where other circuit elements are interposed between A and B.

[0029] Figure 1 It is a block diagram showing the configuration of a power supply device 1 according to the embodiment.

[0030] The power supply device 1 is a power supply device mounted on a vehicle 100 and connected to a first DC power supply 2 for supplying and maintaining a first voltage and a second DC power supply 3 for supplying and maintaining a second voltage lower than the first voltage, and includes: a first switch 5 having one end connected to the first DC power supply 2, a first electrostatic capacitor 91 connected between the other end of the first switch 5 and a reference potential GND (ground), a second switch 6 having one end connected to the second DC power supply 3, a second electrostatic capacitor 92 connected between the other end of the second switch 6 and the reference potential GND, a DC / DC converter unit 4 having a first DC / DC converter 41 and a second DC / DC converter 42 connected in parallel between the other end of the first switch 5 and the other end of the second switch 6, and a control unit 7 having a diagnostic unit 8 for controlling the first switch 5, the second switch 6, and the DC / DC converter unit 4.

[0031] The power supply device 1 also includes: a first potential detection unit 51 for detecting a voltage at one end of the first switch 5, a second potential detection unit 52 for detecting a voltage at the other end of the first switch 5, a third potential detection unit 61 for detecting a voltage at one end of the second switch 6, and a fourth potential detection unit 62 for detecting a voltage at the other end of the second switch 6.

[0032] The first DC power source 2 is, for example, a chargeable and dischargeable battery. The second DC power source 3 is, for example, a chargeable and dischargeable electric double layer capacitor or a battery.

[0033] The first switch 5 and the second switch 6 are switches that selectively enter an on state and an off state, and are, for example, semiconductor switches such as MOSFET (metal oxide field effect transistor) or contactors such as electromagnetic relays.

[0034] The first DC / DC converter 41 performs a step-down operation to step down the first voltage supplied from the first DC power supply 2 side to a second voltage and outputs it to the second DC power supply 3 side, and a step-up operation to step up the second voltage supplied from the second DC power supply 3 side to the first voltage and outputs it to the first DC power supply 2 side, in accordance with instructions from the control unit 7.

[0035] The second DC / DC converter 42 performs a step-down operation to step down the first voltage supplied from the first DC power supply 2 side to a second voltage and outputs it to the second DC power supply 3 side, and a step-up operation to step up the second voltage supplied from the second DC power supply 3 side to the first voltage and outputs it to the first DC power supply 2 side, in accordance with instructions from the control unit 7.

[0036] The first potential detection unit 51, the second potential detection unit 52, the third potential detection unit 61, and the fourth potential detection unit 62 are, for example, A / D converters. The first potential detection unit 51 and the second potential detection unit 52 constitute a first potential difference detection unit that detects a potential difference V5 between both ends of the first switch 5. The third potential detection unit 61 and the fourth potential detection unit 62 constitute a second potential difference detection unit that detects a potential difference V6 between both ends of the second switch 6.

[0037] The control unit 7 has the following three operation modes by controlling the first switch 5, the second switch 6, and the DC / DC converter unit 4. The first operation mode is a step-down operation mode in which step-down control is performed. In this step-down control, the first DC / DC converter 41 and the second DC / DC converter 42 are made to step down the first voltage supplied from the first DC power supply 2 to the second voltage in parallel, that is, simultaneously, and output it to the second DC power supply 3 while the first switch 5 and the second switch 6 are turned on. The second operation mode is a step-up operation mode in which step-up control is performed. In this step-up control, the first DC / DC converter 41 and the second DC / DC converter 42 are made to step up the second voltage supplied from the second DC power supply 3 to the first voltage in parallel, and output it to the first DC power supply 2 while the first switch 5 and the second switch 6 are turned on. The third action mode is a step-up / step-down action mode for performing step-up / step-down control. In this step-up / step-down control, with the first switch 5 and the second switch 6 being disconnected, the first DC / DC converter 41 steps down the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92, and in parallel, the second DC / DC converter 42 steps up the voltage of the second electrostatic capacitor 92 and outputs it to the first electrostatic capacitor 91.

[0038] Furthermore, in the step-up / down operation mode, the step-down operation and the step-up operation of the first DC / DC converter 41 and the second DC / DC converter 42 may be switched. That is, step-up / down control may be performed in which the first DC / DC converter 41 steps up the voltage of the second electrostatic capacitor 92 and outputs it to the first electrostatic capacitor 91 while the first switch 5 and the second switch 6 are turned off, and in parallel, the second DC / DC converter 42 steps down the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92.

[0039] Here, the step-down operation mode is one of the voltage conversion operations for stepping down the first voltage supplied from the first DC power source 2 and converting it into the second voltage to charge the first DC power source 2. The step-up operation mode is one of the voltage conversion operations for stepping up the second voltage supplied from the second DC power source 3 and converting it into the first voltage to charge the first DC power source 2. The step-up and step-down operation mode is an operation mode for diagnosing the disconnection capabilities of the first switch 5 and the second switch 6 and diagnosing a failure of the switching element provided in the DC / DC converter unit 4, and is also called a diagnosis mode.

[0040] In the step-up / down voltage action mode, after the step-up / down voltage control, the diagnosis unit 8 calculates the difference between the voltage detected by the first potential detection unit 51 and the voltage detected by the second potential detection unit 52, i.e., the first potential difference V5, as the potential difference between the two ends of the first switch 5 in order to detect the potential difference V5 between the two ends of the first switch 5, and determines whether the calculated first potential difference V5 is larger than a specified first reference potential difference. If the first potential difference V5 is larger than the first reference potential difference, it is determined that the cutting capacity of the first switch 5 is normal; otherwise, it is determined that the cutting capacity of the first switch 5 is abnormal.

[0041] Similarly, in the step-up / down voltage action mode, after the step-up / down voltage control, the diagnosis unit 8 calculates the difference between the voltage detected by the third potential detection unit 61 and the voltage detected by the fourth potential detection unit 62, i.e., the second potential difference V6, as the potential difference V6 between the two ends of the second switch 6 in order to detect the potential difference V6 between the two ends of the second switch 6, and determines whether the calculated second potential difference V6 is larger than a specified second reference potential difference. If the second potential difference V6 is larger than the second reference potential difference, it is determined that the cutting capacity of the second switch 6 is normal; otherwise, it is determined that the cutting capacity of the second switch 6 is abnormal.

[0042] The control unit 7 and the diagnosis unit 8 are implemented by a memory storing a program, a processor executing the program, an A / D converter, a timer, and the like.

[0043] Furthermore, a first potential difference detection unit for detecting the potential difference V5 between the two ends of the first switch 5 may be directly provided instead of the first potential detection unit 51 and the second potential detection unit 52. Similarly, a second potential difference detection unit for detecting the potential difference V6 between the two ends of the second switch 6 may be directly provided instead of the third potential detection unit 61 and the fourth potential detection unit 62.

[0044] Figure 2 Yes means Figure 1 FIG. 1 is a diagram showing a specific circuit example of the DC / DC converter unit 4 included in the power supply device 1 shown in FIG.

[0045] The first DC / DC converter 41 includes: a first current sensor 414 connected in series between the first switch 5 and the second switch 6, a first switching element 411 and a first inductor 413, and a second switching element 412 connected between a connection point J41 where the first switching element 411 and the first inductor 413 are connected in series and a reference potential GND.

[0046] The second DC / DC converter 42 includes: a second current sensor 424, a third switching element 421 and a second inductor 423 connected in series between the first switch 5 and the second switch 6, and a fourth switching element 422 connected between a connection point J42 where the third switching element 421 and the second inductor 423 are connected in series and a reference potential GND.

[0047] First current sensor 414 and second current sensor 424 are sensors for detecting current flowing through first DC / DC converter 41 and second DC / DC converter 42 , respectively, and are composed of, for example, a resistor element and an A / D converter for converting a voltage across the resistor element into a digital value.

[0048] The first switching element 411, the second switching element 412, the third switching element 421 and the fourth switching element 422 are, for example, N-channel MOSFETs and have body diodes. The body diodes have anodes on the source electrode side of the switching element and cathodes on the drain electrode side.

[0049] Next, the operation of the power supply device 1 according to the present embodiment configured as above will be described.

[0050] Figure 3A Yes means Figure 2 FIG. 2 is a diagram showing the flow of current in the voltage step-down operation mode of the power supply device 1 shown.

[0051] In the step-down operation mode, under the control of the control unit 7 , the first switch 5 and the second switch 6 are kept in the on state, and the first DC / DC converter 41 and the second DC / DC converter 42 perform the following operations in parallel.

[0052] In the first DC / DC converter 41, the first switching element 411 is turned on and the second switching element 412 is turned off, whereby, as shown by the current path 21a, the current supplied from the first DC power source 2 flows to the second DC power source 3 via the first switch 5, the first current sensor 414, the first switching element 411, the first reactor 413, and the second switch 6, and as a result, energy is stored in the first reactor 413. In addition, the first switching element 411 is turned off and the second switching element 412 is turned on, whereby, as shown by the current path 21b, the energy stored in the first reactor 413 is released, and the current flows from the reference potential GND via the second switching element 412, the first reactor 413, and the second switch 6 to the second DC power source 3, and further, according to the output mode (high output / low output), the current flows in the opposite path. In the first DC / DC converter 41 , the state in which energy is stored in the first reactor 413 and the state in which the energy stored in the first reactor 413 is released are switched alternately and repeatedly.

[0053] At this time, the control unit 7 monitors the current value detected by the first current sensor 414, and controls the duty cycle of the PWM (pulse width modulation) control signal output to the first switching element 411 and the second switching element 412 so that the current value is below a specified upper limit value or within a specified range, thereby controlling the switching action of the first switching element 411 and the second switching element 412.

[0054] In the second DC / DC converter 42, the third switching element 421 is turned on and the fourth switching element 422 is turned off, whereby, as shown by the current path 22a, the current supplied from the first DC power source 2 flows to the second DC power source 3 via the first switch 5, the second current sensor 424, the third switching element 421, the second reactor 423, and the second switch 6, and as a result, energy is stored in the second reactor 423. In addition, the third switching element 421 is turned off and the fourth switching element 422 is turned on, whereby, as shown by the current path 22b, the energy stored in the second reactor 423 is released, and the current flows from the reference potential GND via the fourth switching element 422, the second reactor 423, and the second switch 6 to the second DC power source 3, and further, according to the output mode (high output / low output), the current flows in the opposite path. In the second DC / DC converter 42 , the state in which energy is stored in the second reactor 423 and the state in which the energy stored in the second reactor 423 is released are switched alternately and repeatedly.

[0055] At this time, the control unit 7 monitors the current value detected by the second current sensor 424, and controls the duty cycle of the PWM control signal output to the third switching element 421 and the fourth switching element 422 so that the current value is below a specified upper limit value or within a specified range, thereby controlling the switching action of the third switching element 421 and the fourth switching element 422.

[0056] As described above, in the step-down operation mode, first DC / DC converter 41 and second DC / DC converter 42 perform a step-down operation in parallel to step down the first voltage supplied from first DC power source 2 to a second voltage and output the voltage to second DC power source 3 .

[0057] Figure 3B Yes Description Figure 3A FIG. 1 is a diagram showing a failure of a switching element in a step-down operation mode of the power supply device 1 shown in FIG. In this figure, the flow of current when the second switching element 412 is in an open circuit failure is shown. An open circuit failure of a switching element refers to a failure in which the switching element remains disconnected and is not connected. As shown in this figure, when the second switching element 412 is in an open circuit failure, as shown in the current path 21b, the current flowing from the reference potential GND via the second switching element 412 toward the first inductor 413 becomes a current flowing in the forward direction of the body diode via the body diode of the second switching element 412, and no current flows in the reverse direction thereof, resulting in asynchronous rectification.

[0058] Figure 3C 4 is a timing chart showing the operation of the first DC / DC converter 41 for explaining the open-circuit failure of the second switching element 412. Figure 3C In the figure, "high-side (Hi-Side) switch (411)" indicates the on-off of the first switch element 411, "low-side (Lo-Side) switch (412)" indicates the on-off of the second switch element 412, "inductor (413) current: high output" indicates the current flowing in the first inductor 413 at high output, "inductor (413) current: low output (synchronous rectification: continuous mode)" indicates the current flowing in the first inductor 413 when the second switch element 412 is normal at low output, and "inductor (413) current: low output (non-synchronous rectification: discontinuous mode)" indicates the current flowing in the first inductor 413 when the second switch element 412 is in an open-circuit fault at low output.

[0059] according to Figure 3C From the current waveform of "Inductor (413) current: low output (asynchronous rectification: discontinuous mode)", it can be seen that even when the second switch element 412 is in an open circuit fault, at low output, the operation mode is only changed from synchronous rectification (continuous mode) to asynchronous rectification (discontinuous mode) to perform a voltage reduction operation.

[0060] This phenomenon also occurs when the fourth switching element 422 in the second DC / DC converter 42 is in an open-circuit failure.

[0061] Therefore, in the step-down operation mode, even if the switching elements on the low (Lo) side of each DC / DC converter, that is, the second switching element 412 and the fourth switching element 422, are in an open circuit fault, the step-down operation is performed, so it is difficult to detect the fault. In contrast, as described later, in the diagnosis mode, the open circuit fault of the switching element can be detected.

[0062] Figure 4A Yes means Figure 2 FIG. 2 is a diagram showing the flow of current in the voltage step-up operation mode of the power supply device 1 .

[0063] In the voltage step-up operation mode, under the control of the control unit 7 , the first switch 5 and the second switch 6 are kept in the on state, and the first DC / DC converter 41 and the second DC / DC converter 42 operate in parallel, that is, simultaneously as follows.

[0064] In the first DC / DC converter 41, the first switching element 411 is turned off and the second switching element 412 is turned on, whereby, as shown by the current path 31a, the current supplied from the second DC power source 3 flows to the reference potential GND via the first reactor 413 and the second switching element 412, and as a result, energy is stored in the first reactor 413. In addition, the first switching element 411 is turned on and the second switching element 412 is turned off, whereby, as shown by the current path 31b, the energy stored in the first reactor 413 is released, and the current flows from the second DC power source 3 to the first DC power source 2 via the first reactor 413, the first switching element 411, the first current sensor 414, and the first switch 5. In the first DC / DC converter 41, the above-mentioned state in which energy is stored in the first reactor 413 and the above-mentioned state in which the energy stored in the first reactor 413 is released are alternately and repeatedly switched.

[0065] At this time, the control unit 7 monitors the current value detected by the first current sensor 414, and controls the duty cycle of the PWM control signal output to the first switching element 411 and the second switching element 412 so that the current value is below a specified upper limit value or within a specified range, thereby controlling the switching action of the first switching element 411 and the second switching element 412.

[0066] In the second DC / DC converter 42, the third switching element 421 is turned off and the fourth switching element 422 is turned on, whereby, as shown by the current path 32a, the current supplied from the second DC power source 3 flows to the reference potential GND via the second reactor 423 and the fourth switching element 422, and as a result, energy is stored in the second reactor 423. In addition, the third switching element 421 is turned on and the fourth switching element 422 is turned off, whereby, as shown by the current path 32b, the energy stored in the second reactor 423 is released, and the current flows from the second DC power source 3 to the first DC power source 2 via the second reactor 423, the third switching element 421, the second current sensor 424, and the first switch 5. In the second DC / DC converter 42, the above-mentioned state in which energy is stored in the second reactor 423 and the above-mentioned state in which the energy stored in the second reactor 423 is released are alternately and repeatedly switched.

[0067] At this time, the control unit 7 monitors the current value detected by the second current sensor 424, and controls the duty cycle of the PWM control signal output to the third switching element 421 and the fourth switching element 422 so that the current value is below a specified upper limit value or within a specified range, thereby controlling the switching action of the third switching element 421 and the fourth switching element 422.

[0068] As described above, in the boost operation mode, first DC / DC converter 41 and second DC / DC converter 42 perform a boost operation in parallel to boost the second voltage supplied from second DC power source 3 to the first voltage and output the voltage to first DC power source 2 .

[0069] Figure 4B Yes Description Figure 4A FIG. 1 is a diagram showing a failure of a switching element in a boost operation mode of the power supply device 1 shown in FIG. In this figure, the flow of current when the first switching element 411 is in an open circuit failure is shown. As shown in this figure, when the first switching element 411 is in an open circuit failure, as shown in the current path 31b, the current flowing from the first inductor 413 toward the first current sensor 414 becomes a current flowing in the forward direction of the body diode via the body diode of the first switching element 411.

[0070] Figure 4C 4 is a timing chart showing the operation of the first DC / DC converter 41 for explaining an open-circuit failure of the first switching element 411. Figure 4CIn the figure, "low-side (Lo-Side) switch (412)" indicates the on-off of the second switch element 412, "high-side (Hi-Side) switch (411)" indicates the on-off of the first switch element 411, "inductor (413) current: high output" indicates the current flowing in the first inductor 413 at high output, "inductor (413) current: low output (synchronous rectification: continuous mode)" indicates the current flowing in the first inductor 413 when the first switch element 411 is normal at low output, and "inductor (413) current: low output (non-synchronous rectification: discontinuous mode)" indicates the current flowing in the first inductor 413 when the first switch element 411 is in an open circuit fault at low output.

[0071] according to Figure 4C From the current waveform of "Inductor (413) current: low output (asynchronous rectification: discontinuous mode)", it can be seen that even when the first switch element 411 is in an open circuit fault, at low output, the operation mode is only changed from synchronous rectification (continuous mode) to asynchronous rectification (discontinuous mode) to perform a boost operation.

[0072] This phenomenon also occurs when the third switching element 421 in the second DC / DC converter 42 is in an open-circuit failure.

[0073] Therefore, in the boost operation mode, even if the high (Hi) side switching elements in each DC / DC converter, i.e., the first switching element 411 and the third switching element 421, are in an open circuit fault, the boost operation is performed, so it is difficult to detect the fault. In contrast, as described later, in the diagnostic mode, an open circuit fault of the switching element can be detected.

[0074] Figure 5A Yes means Figure 2 Flow chart of a method for diagnosing switches 5 and 6 in power supply device 1 is shown.

[0075] First, the control unit 7 instructs the first switch 5 and the second switch 6 to be in the OFF state ( S10 ).

[0076] Next, the control unit 7 causes the DC / DC converter unit 4 to perform a step-up / step-down operation, thereby releasing the charge accumulated in the first electrostatic capacitor 91 and the charge accumulated in the second electrostatic capacitor 92 (S11). Specifically, the control unit 7 causes the first DC / DC converter 41 to perform a step-down operation for a certain period of time (for example, 1 second), and in parallel, that is, simultaneously, causes the second DC / DC converter 42 to perform a step-up operation, thereby releasing the charge accumulated in the first electrostatic capacitor 91 and the second electrostatic capacitor 92.

[0077] Figure 5B Yes means Figure 5A FIG. 5 is a diagram of the flow of current in step S11.

[0078] In the first DC / DC converter 41, the first switching element 411 is turned on and the second switching element 412 is turned off, thereby, as shown by the current path 21a, the charge accumulated in the first electrostatic capacitor 91 is released, and the current flows to the second electrostatic capacitor 92 via the first current sensor 414, the first switching element 411, and the first reactor 413, and as a result, energy is accumulated in the first reactor 413. In addition, the first switching element 411 is turned off and the second switching element 412 is turned on, thereby, as shown by the current path 21b, the energy accumulated in the first reactor 413 is released, and the current flows from the reference potential GND to the second electrostatic capacitor 92 via the second switching element 412 and the first reactor 413, and further, according to the output mode (high output / low output), the current flows in the opposite path. In the first DC / DC converter 41 , the state in which energy is stored in the first reactor 413 and the state in which the energy stored in the first reactor 413 is released are switched alternately and repeatedly.

[0079] By the voltage step-down operation performed by the first DC / DC converter 41 , the charge accumulated in the first electrostatic capacitor 91 is released, and the voltage of the first electrostatic capacitor 91 decreases.

[0080] In the second DC / DC converter 42, the third switching element 421 is turned off and the fourth switching element 422 is turned on, thereby, as shown by the current path 32a, the charge accumulated in the second electrostatic capacitor 92 is released, and the current flows to the reference potential GND via the second reactor 423 and the fourth switching element 422, and as a result, energy is accumulated in the second reactor 423. In addition, the third switching element 421 is turned on and the fourth switching element 422 is turned off, thereby, as shown by the current path 32b, the energy accumulated in the second reactor 423 is released, and the current flows from the second electrostatic capacitor 92 to the first electrostatic capacitor 91 via the second reactor 423, the third switching element 421, and the second current sensor 424. In the second DC / DC converter 42, the above state of accumulating energy in the second reactor 423 and the above state of releasing the energy accumulated in the second reactor 423 are alternately switched repeatedly.

[0081] By the voltage step-up operation performed by the second DC / DC converter 42 , the charge accumulated in the second electrostatic capacitor 92 is released, and the voltage of the second electrostatic capacitor 92 decreases.

[0082] At this time, the second electrostatic capacitor 92 is charged by the first DC / DC converter 41, and the first electrostatic capacitor 91 is charged by the second DC / DC converter 42. However, due to the loss caused by the on-resistance of the switches 5 and 6 or the conduction loss of the inductors 413 and 423, the conversion efficiency in the first DC / DC converter 41 and the second DC / DC converter 42 will not be 100% or more. Therefore, although the second electrostatic capacitor 92 is charged by the first DC / DC converter 41 and the first electrostatic capacitor 91 is charged by the second DC / DC converter 42, the total energy of the first electrostatic capacitor 91 and the second electrostatic capacitor 92 is reduced due to the loss of the first DC / DC converter 41 and the second DC / DC converter 42, so the voltages of the first electrostatic capacitor 91 and the second electrostatic capacitor 92 are gradually reduced.

[0083] Next, in order to detect the potential difference V5 across the first switch 5, the diagnosis section 8 of the control section 7 calculates the difference between the voltage detected by the first potential detection section 51 and the voltage detected by the second potential detection section 52, i.e., the first potential difference V5 (S12), and determines whether the calculated first potential difference V5 is larger than a specified first reference potential difference (S13). If the first potential difference V5 is larger than the first reference potential difference (S13: Yes), it is determined that the cutting capacity of the first switch 5 is normal (S14). If the first potential difference V5 is not larger than the first reference potential difference (S13: No), it is determined that the cutting capacity of the first switch 5 is abnormal (S15).

[0084] Next, in order to detect the potential difference V6 across the second switch 6, the diagnosis unit 8 of the control unit 7 calculates the difference between the voltages detected by the third potential detection unit 61 and the voltage detected by the fourth potential detection unit 62, i.e., the second potential difference V6 (S16), and determines whether the calculated second potential difference V6 is larger than a specified second reference potential difference (S17). If the second potential difference V6 is larger than the second reference potential difference (S17: Yes), it is determined that the cutting capacity of the second switch 6 is normal (S18). If the second potential difference V6 is not larger than the second reference potential difference (S17: No), it is determined that the cutting capacity of the second switch 6 is abnormal (S19).

[0085] Like this, in the diagnosis of the first switch 5 and the second switch 6, after an instruction is given to put the first switch 5 and the second switch 6 into the cut-off state, due to the step-down action performed by the first DC / DC converter 41, the charge accumulated in the first electrostatic capacitor 91 is released and the voltage of the first electrostatic capacitor 91 decreases, and at the same time, due to the step-up action performed by the second DC / DC converter 42, the charge accumulated in the second electrostatic capacitor 92 is released and the voltage of the second electrostatic capacitor 92 decreases.

[0086] Thus, compared to the power supply device of the comparative example without the step-down operation performed by the first DC / DC converter 41 and the step-up operation performed by the second DC / DC converter 42, when the cut-off capability of the first switch 5 is normal, the potential difference V5 across the first switch 5 increases in a short time, and similarly, when the cut-off capability of the second switch 6 is normal, the potential difference V6 across the second switch 6 increases in a short time. Thus, the cut-off capabilities of the first switch 5 and the second switch 6 are diagnosed simultaneously in a shorter time than in the power supply device of the comparative example. Figure 5A In the above, the diagnosis of the second switch 6 in steps S16 to S19 may be performed before the diagnosis of the first switch 5 in steps S12 to S15.

[0087] In addition, after the switches 5 and 6 are disconnected and the diagnosis of the switches 5 and 6 is completed, the control unit 7 may monitor the voltage detected by the second potential detection unit 52, thereby causing the first DC / DC converter 41 and the second DC / DC converter 42 to perform a voltage step-up operation to charge the first electrostatic capacitor 91 so that the voltage of the first electrostatic capacitor 91 is close to the original first voltage, and after the potential difference V5 at both ends of the first switch 5 becomes within a predetermined range, the first switch 5 is turned on. Thus, the generation of an inrush current due to the first switch 5 being turned on from the disconnected state when the potential difference V5 at both ends is large is suppressed.

[0088] Similarly, after the switches 5 and 6 are disconnected and the diagnosis of the switches 5 and 6 is completed, the control unit 7 may monitor the voltage detected by the fourth potential detection unit 62, thereby causing the first DC / DC converter 41 and the second DC / DC converter 42 to perform a voltage step-down operation to charge the second electrostatic capacitor 92 so that the voltage of the second electrostatic capacitor 92 is close to the original second voltage, and after the potential difference V6 across the two ends of the second switch 6 becomes within a predetermined range, the second switch 6 is turned on. Thus, the generation of an inrush current caused by turning the second switch 6 from the disconnected state to the on state when the potential difference V6 across the two ends is large is suppressed.

[0089] Figure 5C Yes means Figure 2 1 is a diagram showing a modified example of the flow of current in the diagnosis of the switches in the power supply device 1. In this modified example, the control unit 7 performs step-up and step-down control in the step-up and step-down operation mode with the second switch element 412 and the third switch element 421 always turned off (hereinafter, this state is also referred to as "fixed open circuit").

[0090] Specifically, in the first DC / DC converter 41, under the control of the control unit 7, the first switching element 411 is turned on while the second switching element 412 is kept off, thereby, as shown by the current path 21a, the charge accumulated in the first electrostatic capacitor 91 is released, and the current flows to the second electrostatic capacitor 92 via the first current sensor 414, the first switching element 411, and the first reactor 413, and as a result, energy is accumulated in the first reactor 413. In addition, in the first DC / DC converter 41, under the control of the control unit 7, the first switching element 411 is turned off while the second switching element 412 is kept off, thereby, as shown by the current path 21b, the energy accumulated in the first reactor 413 is released, and the current flows from the reference potential GND to the second electrostatic capacitor 92 via the body diode of the second switching element 412 and the first reactor 413. In the first DC / DC converter 41 , under the control of the control unit 7 , the state in which energy is stored in the first reactor 413 and the state in which the energy stored in the first reactor 413 is released are alternately switched while the second switching element 412 is kept in the off state.

[0091] By the voltage step-down operation performed by the first DC / DC converter 41 , the charge accumulated in the first electrostatic capacitor 91 is released, and the voltage of the first electrostatic capacitor 91 decreases.

[0092] In the second DC / DC converter 42, under the control of the control unit 7, the third switch element 421 is kept in the off state, and the fourth switch element 422 is turned on, thereby, as shown by the current path 32a, the charge accumulated in the second electrostatic capacitor 92 is released, and the current flows to the reference potential GND via the second reactor 423 and the fourth switch element 422, and as a result, energy is accumulated in the second reactor 423. In addition, in the second DC / DC converter 42, under the control of the control unit 7, the fourth switch element 422 is turned off while the third switch element 421 is kept in the off state, thereby, as shown by the current path 32b, the energy accumulated in the second reactor 423 is released, and the current flows from the second electrostatic capacitor 92 to the first electrostatic capacitor 91 via the second reactor 423, the body diode of the third switch element 421, and the second current sensor 424. In the second DC / DC converter 42, under the control of the control unit 7, the state in which energy is stored in the second reactor 423 and the state in which the energy stored in the second reactor 423 is released are alternately switched while the third switching element 421 is kept in the off state.

[0093] By the voltage step-up operation performed by the second DC / DC converter 42 , the charge accumulated in the second electrostatic capacitor 92 is released, and the voltage of the second electrostatic capacitor 92 decreases.

[0094] In the step-up / down operation mode according to such a modification, as compared to the prior art in which there is no step-down operation by the first DC / DC converter 41 and no step-up operation by the second DC / DC converter 42, when the cut-off capability of the first switch 5 is normal, the potential difference V5 across the first switch 5 increases in a short time, and when the cut-off capability of the second switch 6 is normal, the potential difference V6 across the second switch 6 increases in a short time. Thus, the cut-off capabilities of the first switch 5 and the second switch 6 can be diagnosed in a shorter time than before and at the same time.

[0095] Fig. 6A Yes means Figure 2 1 is a flowchart of a method for detecting a failure of a switching element in a buck-boost operation mode of the power supply device 1 shown.

[0096] First, the control unit 7 turns the first switch 5 and the second switch 6 into an OFF state ( S20 ).

[0097] Next, the control unit 7 causes the DC / DC converter unit 4 to perform a step-up / step-down operation, thereby releasing the charges accumulated in the first electrostatic capacitor 91 and the second electrostatic capacitor 92 (S21). Specifically, the control unit 7 causes the first DC / DC converter 41 to perform a step-down operation for a certain period of time (e.g., 1 second), and in parallel causes the second DC / DC converter 42 to perform a step-up operation, thereby releasing the charges accumulated in the first electrostatic capacitor 91 and the charges accumulated in the second electrostatic capacitor 92.

[0098] Then, the control unit 7 detects the first potential P15 (S22) by the second potential detection unit 52, and determines whether the first potential P15 detected by the second potential detection unit 52 is lower than a specified first reference potential (S23). When the first potential P15 is lower than the first reference potential (S23: Yes), it is determined that the first switch element 411 is normal (S24). On the other hand, when the first potential P15 is not lower than the first reference potential (S23: No), it is determined that the first switch element 411 is in a fixed off state (open circuit fault) (S25).

[0099] Next, the control unit 7 detects the second potential P16 (S36) by the fourth potential detection unit 62, and determines whether the second potential P16 detected by the fourth potential detection unit 62 is lower than a specified second reference potential (S27). When the second potential P16 is lower than the second reference potential (S27: Yes), it is determined that the fourth switch element 422 is normal (S28). On the other hand, when the second potential P16 is not lower than the second reference potential (S27: No), it is determined that the fourth switch element 422 is in a fixed off state (open circuit fault) (S29).

[0100] Figure 6BYes Description Fig. 6A The determination in steps S23 to S25 and Fig. 6A Here, based on the determination in steps S27 to S29. Figure 5C The figure shows the difference in the flow of current when the first switching element 411 and the fourth switching element 422 are in an open-circuit failure.

[0101] In the first DC / DC converter 41, when the first switching element 411 is normal, as shown by the current path 21a, the first switching element 411 is turned on, thereby, the charge accumulated in the first electrostatic capacitor 91 is released, and the current flows to the second electrostatic capacitor 92 via the first current sensor 414, the first switching element 411, and the first reactor 413, and as a result, energy is accumulated in the first reactor 413. In addition, in the first DC / DC converter 41, when the first switching element 411 is normal, as shown by the current path 21b, the first switching element 411 is turned off, thereby, the energy accumulated in the first reactor 413 is released, and the current flows from the reference potential GND to the second electrostatic capacitor 92 via the body diode of the second switching element 412 and the first reactor 413. In the first DC / DC converter 41 , when the first switching element 411 is normal, the state in which energy is stored in the first reactor 413 and the state in which the energy stored in the first reactor 413 is released are alternately and repeatedly switched.

[0102] Thus, by the voltage reduction operation performed by the first DC / DC converter 41, the charge accumulated in the first electrostatic capacitor 91 is released, and the voltage of the first electrostatic capacitor 91 decreases. However, when the first switching element 411 is in an open circuit fault, the current does not flow in the direction from the first electrostatic capacitor 91 to the first reactor 413 via the first switching element 411. Therefore, the first DC / DC converter 41 does not perform the voltage reduction operation, the charge accumulated in the first electrostatic capacitor 91 is not fully released, and the voltage of the first electrostatic capacitor 91, that is, the first potential P15 detected by the second potential detection unit 52, does not sufficiently decrease, or it takes time to sufficiently decrease.

[0103] Thus, when the first potential P15 detected by the second potential detection unit 52 is not lower than the first reference potential ( S23 : No), the control unit 7 can determine that the first switching element 411 is in an open-circuit failure ( S25 ).

[0104] Similarly, in the second DC / DC converter 42, when the fourth switching element 422 is normal, as shown by the current path 32a, the fourth switching element 422 is turned on, thereby, the charge accumulated in the second electrostatic capacitor 92 is released, and the current flows to the reference potential GND via the second reactor 423 and the fourth switching element 422, and as a result, energy is accumulated in the second reactor 423. In addition, in the second DC / DC converter 42, when the fourth switching element 422 is normal, as shown by the current path 32b, the fourth switching element 422 is turned off, thereby, the energy accumulated in the second reactor 423 is released, and the current flows from the second electrostatic capacitor 92 to the first electrostatic capacitor 91 via the second reactor 423, the body diode of the third switching element 421, and the second current sensor 424. In the second DC / DC converter 42 , when the fourth switching element 422 is normal, the state in which energy is stored in the second reactor 423 and the state in which the energy stored in the second reactor 423 is released are alternately and repeatedly switched.

[0105] By the voltage step-up operation performed by the second DC / DC converter 42, the charge accumulated in the second electrostatic capacitor 92 is released, and the voltage of the second electrostatic capacitor 92 decreases. However, when the fourth switch element 422 is in an open circuit fault, the current does not flow in the direction from the second electrostatic capacitor 92 to the reference potential GND via the second reactor 423 and the fourth switch element 422. Therefore, the second DC / DC converter 42 does not perform the voltage step-up operation, the charge accumulated in the second electrostatic capacitor 92 is not fully released, and the second electrostatic capacitor 92, that is, the second potential P16 detected by the fourth potential detection unit 62, does not fully decrease, or it takes time to fully decrease.

[0106] Thus, when the second potential P16 detected by the fourth potential detector 62 is not lower than the second reference potential ( S27 : No), the control unit 7 can determine that the fourth switching element 422 is in an open-circuit failure ( S29 ).

[0107] Thus, in the step-up / step-down operation mode (diagnosis mode), not only the cutoff capabilities of the first switch 5 and the second switch 6 can be diagnosed, but also the open-circuit failures of the first switching element 411 and the fourth switching element 422 can be diagnosed.

[0108] In addition, Fig. 6AIn the fault detection method of the switching element in the buck-boost operation mode shown in the figure, the buck operation and the boost operation of the first DC / DC converter 41 and the second DC / DC converter 42 may be switched. That is, it is also possible to perform buck-boost control in which the first DC / DC converter 41 boosts the voltage of the second electrostatic capacitor 92 and outputs it to the first electrostatic capacitor 91 while the first switch 5 and the second switch 6 are disconnected, and the second DC / DC converter 42 steps down the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92 in parallel.

[0109] Figure 6C It means that Fig. 6A In the step-up / step-down operation mode shown in FIG. 1 , the step-down operation and the step-up operation of the first DC / DC converter 41 and the second DC / DC converter 42 are switched. Figure 2 1 is a flowchart of a method for detecting a failure of a switching element in a buck-boost operation mode of the power supply device 1 shown.

[0110] First, the control unit 7 turns the first switch 5 and the second switch 6 into an OFF state ( S30 ).

[0111] Next, the control unit 7 causes the DC / DC converter unit 4 to perform a step-up / step-down operation, thereby releasing the charges accumulated in the first electrostatic capacitor 91 and the second electrostatic capacitor 92 (S31). Specifically, the control unit 7 causes the first DC / DC converter 41 to perform a step-up operation for a certain period of time (e.g., 1 second), and in parallel causes the second DC / DC converter 42 to perform a step-down operation, thereby releasing the charges accumulated in the first electrostatic capacitor 91 and the charges accumulated in the second electrostatic capacitor 92.

[0112] Then, the control unit 7 checks the first potential P15 (S32) by the second potential detection unit 52, and determines whether the first potential P15 detected by the second potential detection unit 52 is lower than the specified first reference potential (S33). When the first potential P15 is lower than the first reference potential (S33: Yes), it is determined that the third switch element 421 is normal (S34). On the other hand, when the first potential P15 is not lower than the first reference potential (S33: No), it is determined that the third switch element 421 is in a fixed off state (open circuit fault) (S35).

[0113] Next, the control unit 7 detects the second potential P16 (S36) by the fourth potential detection unit 62, and determines whether the second potential P16 detected by the fourth potential detection unit 62 is lower than a specified second reference potential (S37). When the second potential P16 is lower than the second reference potential (S37: Yes), it is determined that the second switch element 412 is normal (S38). On the other hand, when the second potential P16 is not lower than the second reference potential (S37: No), it is determined that the second switch element 412 is in a fixed off state (open circuit fault) (S39).

[0114] Fig.6D Yes Description Figure 6C The determination in steps S33 to S35 and Figure 6C Here, based on Figure 5C The figure shows the difference in the flow of current when the second switching element 412 and the third switching element 421 are in an open-circuit failure.

[0115] In the second DC / DC converter 42, when the third switching element 421 is normal, as shown by the current path 22a, the third switching element 421 is turned on, thereby, the charge accumulated in the first electrostatic capacitor 91 is released, and the current flows to the second electrostatic capacitor 92 via the second current sensor 424, the third switching element 421, and the second reactor 423, and as a result, energy is accumulated in the second reactor 423. In addition, in the second DC / DC converter 42, when the third switching element 421 is normal, as shown by the current path 22b, the third switching element 421 is turned off, thereby, the energy accumulated in the second reactor 423 is released, and the current flows from the reference potential GND to the second electrostatic capacitor 92 via the body diode of the fourth switching element 422 and the second reactor 423. In the second DC / DC converter 42 , when the third switching element 421 is normal, the state in which energy is stored in the second reactor 423 and the state in which the energy stored in the second reactor 423 is released are alternately and repeatedly switched.

[0116] Thus, by the voltage reduction operation performed by the second DC / DC converter 42, the charge accumulated in the first electrostatic capacitor 91 is released, and the voltage of the first electrostatic capacitor 91 gradually decreases. However, when the third switching element 421 is in an open circuit fault, the current does not flow from the first electrostatic capacitor 91 to the second reactor 423 via the third switching element 421. Therefore, the second DC / DC converter 42 does not perform the voltage reduction operation, the charge accumulated in the first electrostatic capacitor 91 is not fully released, and the voltage of the first electrostatic capacitor 91, that is, the first potential P15 detected by the second potential detection unit 52, does not drop sufficiently, or it takes time to drop sufficiently.

[0117] Thus, when the first potential P15 detected by the second potential detection unit 52 is not lower than the first reference potential ( S33 : No), the control unit 7 can determine that the third switching element 421 is in an open-circuit failure ( S35 ).

[0118] Similarly, in the first DC / DC converter 41, when the second switching element 412 is normal, as shown by the current path 31a, the second switching element 412 is turned on, thereby, the charge accumulated in the second electrostatic capacitor 92 is released, and the current flows to the reference potential GND via the first reactor 413 and the second switching element 412, and as a result, energy is accumulated in the first reactor 413. In addition, in the first DC / DC converter 41, when the second switching element 412 is normal, as shown by the current path 31b, the second switching element 412 is turned off, thereby, the energy accumulated in the first reactor 413 is released, and the current flows from the second electrostatic capacitor 92 to the first electrostatic capacitor 91 via the first reactor 413, the body diode of the first switching element 411, and the first current sensor 414. In the first DC / DC converter 41 , when the second switching element 412 is normal, the state in which energy is stored in the first reactor 413 and the state in which the energy stored in the first reactor 413 is released are alternately and repeatedly switched.

[0119] By the voltage step-up operation performed by the first DC / DC converter 41, the charge accumulated in the second electrostatic capacitor 92 is released, and the voltage of the second electrostatic capacitor 92 gradually decreases. However, when the second switching element 412 is in an open circuit fault, the current does not flow in the direction from the second electrostatic capacitor 92 to the reference potential GND via the first reactor 413 and the second switching element 412. Therefore, the first DC / DC converter 41 does not perform the voltage step-up operation, the charge accumulated in the second electrostatic capacitor 92 is not fully released, and the second electrostatic capacitor 92, that is, the second potential P16 detected by the fourth potential detection unit 62, does not fully decrease, or it takes time to fully decrease.

[0120] Thus, when the second potential P16 detected by the fourth potential detector 62 is not lower than the second reference potential ( S37 : No), the control unit 7 can determine that the second switching element 412 is in an open-circuit failure ( S39 ).

[0121] Thus, in the step-up / step-down operation mode (diagnosis mode), not only the cutoff capabilities of the first switch 5 and the second switch 6 can be diagnosed, but also the open-circuit failures of the second switching element 412 and the third switching element 421 can be diagnosed.

[0122] As described above, the power supply device 1 according to the embodiment is connected to the first DC power supply 2 for supplying and maintaining the first voltage and the second DC power supply 3 for supplying and maintaining the second voltage lower than the first voltage, and includes: the first switch 5 having one end connected to the first DC power supply 2, the first electrostatic capacitor 91 connected between the other end of the first switch 5 and the reference potential GND, the second switch 6 having one end connected to the second DC power supply 3, the second electrostatic capacitor 92 connected between the other end of the second switch 6 and the reference potential GND, the DC / DC converter section 4 having the first DC / DC converter 41 and the second DC / DC converter 42 connected in parallel between the other end of the first switch 5 and the other end of the second switch 6, and the control section 7 for controlling the first switch 5, the second switch 6, and the DC / DC converter section 4, the control section 7 having a step-down operation mode for performing step-down control, in which the first switch 5 and the second switch 6 are switched to the step-down operation mode. 6 is turned on, the first DC / DC converter 41 and the second DC / DC converter 42 are caused to step down the first voltage supplied from the first DC power supply 2 into the second voltage in parallel and output it to the second DC power supply 3; a step-up operation mode for performing step-up control, in which the first DC / DC converter 41 and the second DC / DC converter 42 are caused to step up the second voltage supplied from the second DC power supply 3 into the first voltage in parallel and output it to the first DC power supply 2, while the first switch 5 and the second switch 6 are turned on; and a step-up and step-down operation mode (diagnosis mode) for performing step-up and step-down control, in which the first DC / DC converter 41 steps down the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92, while the second DC / DC converter 42 steps up the voltage of the second electrostatic capacitor 92 and outputs it to the first electrostatic capacitor 91, while the first switch 5 and the second switch 6 are turned off.

[0123] Thus, in the diagnosis mode, in the state where the first switch 5 and the second switch 6 are cut off, the voltage of the first electrostatic capacitor 91 is stepped down by the first DC / DC converter 41 and is transmitted to the second electrostatic capacitor 92, and in parallel, the voltage of the second electrostatic capacitor 92 is stepped up by the second DC / DC converter 42 and is output to the first electrostatic capacitor 91. Thus, when the cutting ability of the first switch 5 is normal, the potential difference V5 across the first switch 5 increases in a short time, and when the cutting ability of the second switch 6 is normal, the potential difference V6 across the second switch 6 increases in a short time. As a result, the cutting abilities of the first switch 5 and the second switch 6 can be diagnosed in a shorter time than before and at the same time.

[0124] Specifically, the power supply device 1 includes a first potential difference detection unit for detecting a potential difference V5 between both ends of the first switch 5, and a second potential difference detection unit for detecting a potential difference V6 between both ends of the second switch 6. The control unit 7 determines whether the first potential difference V5 detected by the first potential difference detection unit is larger than the first reference potential difference after the boost / boost control in the boost / boost operation mode, and determines that the first switch 5 is normal when the first potential difference V5 is larger than the first reference potential difference, and determines that the first switch 5 is abnormal and cannot be disconnected when the first potential difference V5 is not larger than the first reference potential difference. Furthermore, the control unit 7 determines whether the second potential difference V6 detected by the second potential difference detection unit is larger than the second reference potential difference after the boost / boost control in the boost / boost operation mode, and determines that the second switch 6 is normal when the second potential difference V6 is larger than the second reference potential difference, and determines that the second switch 6 is abnormal and cannot be disconnected when the second potential difference V6 is not larger than the second reference potential difference.

[0125] Here, the control unit 7 may be configured to perform voltage step-down of the first DC / DC converter 41 and voltage step-up of the second DC / DC converter 42 for a certain period of time after turning off the first switch 5 and the second switch 6 in the step-up / step-down operation mode. Thus, the potential difference V6 across the first switch 5 and the second switch 6 can be set to an appropriate value.

[0126] Here, the first DC / DC converter 41 may include a first switching element 411 and a first reactor 413 connected in series between the first switch 5 and the second switch 6, and a second switching element 412 having a body diode connected between a connection point J41 where the first switching element 411 and the first reactor 413 are connected in series with each other and a reference potential GND, and the second DC / DC converter 42 may include a third switching element 421 and a second reactor 423 having a body diode connected in series between the first switch 5 and the second switch 6, and a fourth switching element 422 connected between a connection point J42 where the third switching element 421 and the second reactor 423 are connected in series with each other and the reference potential GND. Thus, the first DC / DC converter 41 and the second DC / DC converter 42 are realized by a simple circuit.

[0127] Alternatively, the control unit 7 may perform the step-up / step-down control in the step-up / step-down operation mode while the second switch element 412 and the third switch element 421 are always turned off. Thus, in the step-up / step-down operation mode, current flows through the body diodes of the second switch element 412 and the third switch element 421, thereby consuming more power and diagnosing the cutoff capabilities of the first switch 5 and the second switch 6 in a shorter time.

[0128] Alternatively, the first DC / DC converter 41 and the second DC / DC converter 42 may include a first current sensor 414 and a second current sensor 424 for detecting the current flowing in the first DC / DC converter 41 and the second DC / DC converter 42, and the control unit 7 may control the DC / DC converter unit 4 in the step-down operation mode, the step-up operation mode, and the step-up / step-down operation mode so that the current detected by the first current sensor 414 and the second current sensor 424 is within a predetermined range. Thus, the current flowing in the first DC / DC converter 41 and the second DC / DC converter 42 is limited to a certain value or less, thereby suppressing the occurrence of the inrush current.

[0129] Alternatively, the power supply device 1 may include a second potential detection unit 52 for detecting the potential P15 at the other end of the first switch 5, and a fourth potential detection unit 62 for detecting the potential P16 at the other end of the second switch 6. In the step-up / down operation mode, the control unit 7 determines whether the first potential P15 detected by the second potential detection unit 52 is lower than the first reference potential, and when the first potential P15 is not lower than the first reference potential, determines that the first switch element 411 is abnormally fixedly turned off, and determines whether the second potential P16 detected by the fourth potential detection unit 62 is lower than the second reference potential, and when the second potential P16 is not lower than the second reference potential, determines that the fourth switch element 422 is abnormally fixedly turned off. Thus, the open circuit failures of the first switch element 411 and the fourth switch element 422 are detected simultaneously with the diagnosis of the first switch 5 and the second switch 6.

[0130] In addition, the diagnostic method of the power supply device 1 involved in the embodiment is a diagnostic method for a power supply device connected to a first DC power supply 2 that supplies and maintains a first voltage and a second DC power supply 3 that supplies and maintains a second voltage lower than the first voltage. The power supply device 1 includes: a first switch 5 having one end connected to the first DC power supply 2, a first electrostatic capacitor 91 connected between the other end of the first switch 5 and a reference potential GND, a second switch 6 having one end connected to the second DC power supply 3, a second electrostatic capacitor 92 connected between the other end of the second switch 6 and the reference potential GND, and a DC / DC converter unit 4 having a first DC / DC converter 41 and a second DC / DC converter 42 connected in parallel between the other end of the first switch 5 and the other end of the second switch 6. The diagnostic method includes: a step-down step of performing a step-down control in which the first switch 5 and the second switch 6 are turned on. In the on state, the first DC / DC converter 41 and the second DC / DC converter 42 are caused to step down the first voltage supplied from the first DC power supply 2 to the second voltage in parallel and output it to the second DC power supply 3; a step-up step of step-up control is performed, in which the first switch 5 and the second switch 6 are turned on, the first DC / DC converter 41 and the second DC / DC converter 42 are caused to step up the second voltage supplied from the second DC power supply 3 to the first voltage in parallel and output it to the first DC power supply 2; and a step-up / down control (diagnostic mode) is performed, in which the first switch 5 and the second switch 6 are turned off, the first DC / DC converter 41 steps down the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92, and the second DC / DC converter 42 steps up the voltage of the second electrostatic capacitor 92 and outputs it to the first electrostatic capacitor 91 in parallel.

[0131] Thus, in the diagnosis mode, in the state where the first switch 5 and the second switch 6 are cut off, the voltage of the first electrostatic capacitor 91 is stepped down by the first DC / DC converter 41 and is transmitted to the second electrostatic capacitor 92, and in parallel, the voltage of the second electrostatic capacitor 92 is stepped up by the second DC / DC converter 42 and is output to the first electrostatic capacitor 91. Thus, when the cutting ability of the first switch 5 is normal, the potential difference V5 across the first switch 5 increases in a short time, and when the cutting ability of the second switch 6 is normal, the potential difference V6 across the second switch 6 increases in a short time. As a result, the cutting abilities of the first switch 5 and the second switch 6 can be diagnosed in a shorter time than before and at the same time.

[0132] Specifically, in the step of stepping up and down, after the stepping up and down control, it is determined whether the first potential difference V5 detected by the first potential difference detection unit is larger than the first reference potential difference. If the first potential difference V5 is larger than the first reference potential difference, it is determined that the first switch 5 is normal. If the first potential difference V5 is not larger than the first reference potential difference, it is determined that the first switch 5 is abnormal and cannot be cut off. Furthermore, in the step of stepping up and down, after the stepping up and down control, it is determined whether the second potential difference V6 detected by the second potential difference detection unit is larger than the second reference potential difference. If the second potential difference V6 is larger than the second reference potential difference, it is determined that the second switch 6 is normal. If the second potential difference V6 is not larger than the second reference potential difference, it is determined that the second switch 6 is abnormal and cannot be cut off.

[0133] The power supply device and the power supply device diagnostic method involved in the present disclosure are described above based on the embodiment, but the present disclosure is not limited to the embodiment. As long as it does not deviate from the main purpose of the present disclosure, the present embodiment is subjected to various deformations that can be thought of by a person skilled in the art, and other methods constructed by combining some of the constituent elements in the embodiment are also included in the scope of the present disclosure.

[0134] For example, the DC / DC converter included in the power supply device is not limited to Figure 2 The circuit shown may be another circuit. Hereinafter, a power supply device according to a modified example including a different type of DC / DC converter will be described.

[0135] Figure 7 1 is a block diagram showing the configuration of a power supply device 1a according to a first modification of the embodiment. The power supply device 1a according to this modification includes: Figure 2 The DC / DC converter unit 4 in the power supply device 1 according to the embodiment shown is replaced with a DC / DC converter unit 4a according to this modification. The following description will focus on the differences from the embodiment.

[0136] The DC / DC converter unit 4a includes a first DC / DC converter 41a and a second DC / DC converter 42a which are connected in parallel.

[0137] The first DC / DC converter 41a has, in addition to the configuration of the first DC / DC converter 41 according to the embodiment, a fifth switching element 415 connected in series with the first reactor 413, and a sixth switching element 416 connected between a connection point J41a at which the fifth switching element 415 and the first reactor 413 are connected in series with each other and a reference potential GND. The second DC / DC converter 42a has, in addition to the configuration of the second DC / DC converter 42 according to the embodiment, a seventh switching element 425 connected in series with the second reactor 423, and an eighth switching element 426 connected between a connection point J42a at which the seventh switching element 425 and the second reactor 423 are connected in series with each other and a reference potential GND.

[0138] The fifth switching element 415, the sixth switching element 416, the seventh switching element 425 and the eighth switching element 426 are, for example, N-channel MOSFETs and have body diodes. The body diodes have anodes on the source electrode side of the switching element and cathodes on the drain electrode side.

[0139] The first DC / DC converter 41a can perform not only a step-down operation but also a step-up operation when charging the second DC power supply 3 from the first DC power supply 2 under the control of the control unit 7. When performing the step-down operation, the same operation as the DC / DC converter unit 4 according to the embodiment is performed while maintaining the fifth switching element 415 turned on and the sixth switching element 416 turned off.

[0140] On the other hand, when a boost operation is performed, while the first switch element 411 is maintained in the on state and the second switch element 412 is maintained in the off state, the fifth switch element 415 is turned off and the sixth switch element 416 is turned on, and a current flows from the first DC power supply 2 via the first current sensor 414, the first switch element 411, the first inductor 413 and the sixth switch element 416 to the reference potential GND, thereby accumulating energy in the first inductor 413; and a state in which the fifth switch element 415 is turned on and the sixth switch element 416 is turned off, and a current flows from the first DC power supply 2 via the first current sensor 414, the first switch element 411, the first inductor 413 and the fifth switch element 415 to the second DC power supply 3 due to the release of the energy accumulated in the first inductor 413, are repeated alternately.

[0141] In addition, the first DC / DC converter 41a can perform not only a step-up operation but also a step-down operation when charging the first DC power source 2 from the second DC power source 3 under the control of the control unit 7. When performing the step-up operation, the same operation as the DC / DC converter unit 4 involved in the embodiment is performed while maintaining the fifth switching element 415 turned on and the sixth switching element 416 turned off.

[0142] On the other hand, when a voltage reduction operation is performed, while the first switch element 411 is maintained in the on state and the second switch element 412 is maintained in the off state, the fifth switch element 415 is turned on, the sixth switch element 416 is turned off, and the current flows from the second DC power supply 3 via the fifth switch element 415, the first inductor 413, the first switch element 411 and the first current sensor 414 to the first DC power supply 2, thereby accumulating energy in the first inductor 413; and the fifth switch element 415 is turned off and the sixth switch element 416 is turned on, and the current flows from the reference potential GND via the sixth switch element 416, the first inductor 413, the first switch element 411 and the first current sensor 414 to the first DC power supply 2 due to the release of the energy accumulated in the first inductor 413, are alternately repeated.

[0143] The second DC / DC converter 42a, like the first DC / DC converter 41a, can perform not only a step-down operation but also a step-up operation when charging the second DC power source 3 from the first DC power source 2 under the control of the control unit 7. In addition, the second DC / DC converter 42a, like the first DC / DC converter 41a, can perform not only a step-up operation but also a step-down operation when charging the first DC power source 2 from the second DC power source 3 under the control of the control unit 7.

[0144] In the power supply device 1a according to this modification, the control unit 7 operates as follows in the step-down operation mode, the step-up operation mode, and the step-up / step-down operation mode (diagnosis mode). That is, the control unit 7 can perform the following operation control in addition to the operation control in the embodiment.

[0145] When the second voltage supplied from the second DC power source 3 is higher than the first voltage supplied from the first DC power source 2 , the control unit 7 performs the following control.

[0146] As a step-down operation mode, the control unit 7 performs step-down control. In this step-down control, when the first switch 5 and the second switch 6 are turned on, the first DC / DC converter 41 and the second DC / DC converter 42 in parallel step down the second voltage supplied from the second DC power supply 3 to the first voltage and output it to the first DC power supply 2.

[0147] In addition, as a boost action mode, the control unit 7 performs boost control. In this boost control, when the first switch 5 and the second switch 6 are turned on, the first DC / DC converter 41 and the second DC / DC converter 42 are operated in parallel to boost the first voltage supplied from the first DC power supply 2 to a second voltage and output it to the second DC power supply 3.

[0148] In addition, as a step-up / down operation (diagnostic mode), the control unit 7 performs step-up / down control in which the first DC / DC converter 41 steps down the voltage of the second electrostatic capacitor 92 and outputs it to the first electrostatic capacitor 91 while the first switch 5 and the second switch 6 are turned off, and in parallel, the second DC / DC converter 42 steps up the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92. Alternatively, the control unit 7 performs step-up / down control in which the first DC / DC converter 41 steps up the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92 while the first switch 5 and the second switch 6 are turned off, and in parallel, the second DC / DC converter 42 steps down the voltage of the second electrostatic capacitor 92 and outputs it to the first electrostatic capacitor 91.

[0149] According to the power supply device 1a involved in this variant, similar to the embodiment, in the step-up / step-down action mode (diagnostic mode), after the first switch 5 and the second switch 6 are set to the cut-off state, the charge accumulated in the first electrostatic capacitor 91 is released and the voltage of the first electrostatic capacitor 91 decreases through the step-down action or the step-up action performed by the first DC / DC converter 41, and on the other hand, the charge accumulated in the second electrostatic capacitor 92 is released and the voltage of the second electrostatic capacitor 92 decreases through the step-up action or the step-down action performed by the second DC / DC converter 42.

[0150] Thus, compared to the prior art without the step-up operation or step-down operation performed by the first DC / DC converter 41 and the second DC / DC converter 42, when the cut-off capability of the first switch 5 is normal, the potential difference V5 across the first switch 5 increases in a short time, and when the cut-off capability of the second switch 6 is normal, the potential difference V6 across the second switch 6 increases in a short time. Thus, the cut-off capabilities of the first switch 5 and the second switch 6 can be diagnosed in a shorter time than before and at the same time.

[0151] Figure 8 1 is a block diagram showing the configuration of a power supply device 1b according to a second modification of the embodiment. The power supply device 1b according to this modification includes: Figure 2 The DC / DC converter unit 4 in the power supply device 1 according to the embodiment shown is replaced with a DC / DC converter unit 4b according to this modification. The following description will focus on the differences from the embodiment.

[0152] The DC / DC converter unit 4b includes a first DC / DC converter 41b and a second DC / DC converter 42b which are connected in parallel.

[0153] The first DC / DC converter 41b includes a first current sensor 414, a ninth switching element 417, a tenth switching element 418, and a first transformer 419. The first current sensor 414, the primary winding of the first transformer 419, and the ninth switching element 417 are connected in series. In addition, the secondary winding of the first transformer 419 and the tenth switching element 418 are connected in series.

[0154] The second DC / DC converter 42b includes a second current sensor 424, an 11th switching element 427, a 12th switching element 428, and a second transformer 429. The second current sensor 424, the primary winding of the second transformer 429, and the 11th switching element 427 are connected in series. In addition, the secondary winding of the second transformer 429 and the 12th switching element 428 are connected in series.

[0155] The ninth switching element 417, the tenth switching element 418, the eleventh switching element 427, and the twelfth switching element 428 are, for example, N-channel MOSFETs and have body diodes. The body diodes have anodes on the source electrode side of the switching element and cathodes on the drain electrode side.

[0156] The first DC / DC converter 41b performs a step-up and step-down operation when charging the second DC power supply 3 from the first DC power supply 2 under the control of the control unit 7. At this time, whether to perform a step-up operation or a step-down operation is determined based on the winding ratio of the first transformer 419 and the duty ratio of the control signal from the control unit 7 to the ninth switch element 417.

[0157] Specifically, when charging the second DC power supply 3 from the first DC power supply 2, the ninth switch element 417 performs a switching operation in response to the control of the control unit 7, and the DC voltage of the first DC power supply 2 is stepped up and down to charge the second DC power supply 3. Specifically, as an example, a state in which the ninth switch element 417 is turned on and the current flows from the first DC power supply 2 to the reference potential GND via the first current sensor 414, the primary winding of the first transformer 419, and the ninth switch element 417, thereby accumulating energy in the first transformer 419, and a state in which the ninth switch element 417 is turned off and the current flows from the reference potential GND via the secondary winding of the first transformer 419 and the body diode of the tenth switch element 418 to the second DC power supply 3 due to the release of the energy accumulated in the first transformer 419 are repeated alternately.

[0158] In addition, the first DC / DC converter 41b performs a step-up and step-down operation when charging the first DC power source 2 from the second DC power source 3 under the control of the control unit 7. At this time, whether to perform a step-up operation or a step-down operation is determined based on the winding ratio of the first transformer 419 and the duty ratio of the control signal from the control unit 7 to the tenth switching element 418.

[0159] Specifically, when charging the first DC power source 2 from the second DC power source 3, the tenth switching element 418 performs a switching operation in response to the control of the control unit 7, and the DC voltage of the second DC power source 3 is stepped up and down to charge the first DC power source 2. Specifically, as an example, a state in which the tenth switching element 418 is turned on and the current flows from the second DC power source 3 to the reference potential GND via the tenth switching element 418 and the secondary winding of the first transformer 419, thereby accumulating energy in the first transformer 419, and a state in which the tenth switching element 418 is turned off and the current flows from the reference potential GND via the body diode of the ninth switching element 417, the primary winding of the first transformer 419, and the first current sensor 414 to the first DC power source 2 due to the release of the energy accumulated in the first transformer 419 are repeated alternately.

[0160] The second DC / DC converter 42b performs a step-up and step-down operation when charging the second DC power source 3 from the first DC power source 2 under the control of the control unit 7. At this time, whether to perform a step-up operation or a step-down operation is determined based on the winding ratio of the second transformer 429 and the duty ratio of the control signal from the control unit 7 to the 11th switching element 427.

[0161] Specifically, when charging the second DC power supply 3 from the first DC power supply 2, the 11th switching element 427 performs a switching operation in response to the control of the control unit 7, and the DC voltage of the first DC power supply 2 is stepped up and down to charge the second DC power supply 3. Specifically, as an example, due to the conduction of the 11th switching element 427, the current flows from the first DC power supply 2 to the reference potential GND via the second current sensor 424, the primary winding of the second transformer 429, and the 11th switching element 427, thereby accumulating energy in the second transformer 429, and the state in which the 11th switching element 427 is turned off and the current flows from the reference potential GND via the secondary winding of the second transformer 429 and the body diode of the 12th switching element 428 to the second DC power supply 3 due to the release of the energy accumulated in the second transformer 429 is repeated alternately.

[0162] In addition, the second DC / DC converter 42b performs a step-up and step-down operation when charging the first DC power supply 2 from the second DC power supply 3 under the control of the control unit 7. At this time, whether to perform a step-up operation or a step-down operation is determined based on the winding ratio of the second transformer 429 and the duty ratio of the control signal from the control unit 7 to the twelfth switching element 428.

[0163] Specifically, when charging the first DC power source 2 from the second DC power source 3, the 12th switching element 428 performs a switching operation in response to the control of the control unit 7, and the DC voltage of the second DC power source 3 is stepped up and down to charge the first DC power source 2. Specifically, as an example, due to the conduction of the 12th switching element 428, the current flows from the second DC power source 3 to the reference potential GND via the 12th switching element 428 and the secondary winding of the second transformer 429, thereby accumulating energy in the second transformer 429, and the 12th switching element 428 is turned off. Due to the release of the energy accumulated in the second transformer 429, the current flows from the reference potential GND via the body diode of the 11th switching element 427, the primary winding of the second transformer 429, and the second current sensor 424 to the first DC power source 2, and the state is repeated alternately.

[0164] According to the power supply device 1b in this modification, the control unit 7 can perform the following operation control. That is, as the step-down operation mode or the step-up operation mode, the control unit 7 performs step-up control or step-down control, in which, in the state where the first switch 5 and the second switch 6 are turned on, the first DC / DC converter 41 and the second DC / DC converter 42 are made to step up or step down the first voltage supplied from the first DC power supply 2 to the second voltage in parallel and output it to the second DC power supply 3. Alternatively, the control unit 7 performs step-up control or step-down control, in which, in the state where the first switch 5 and the second switch 6 are turned on, the first DC / DC converter 41 and the second DC / DC converter 42 are made to step up or step down the second voltage supplied from the second DC power supply 3 to the first voltage in parallel and output it to the first DC power supply 2.

[0165] In addition, as a step-up / down operation mode (diagnosis mode), the control unit 7 performs step-up / down control in which the first DC / DC converter 41 steps up or steps down the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92 while the first switch 5 and the second switch 6 are turned off, and in parallel, the second DC / DC converter 42 steps up or steps down the voltage of the second electrostatic capacitor 92 and outputs it to the first electrostatic capacitor 91. Alternatively, the control unit 7 performs step-up / down control in which the second DC / DC converter 42 steps up or steps down the voltage of the first electrostatic capacitor 91 and outputs it to the second electrostatic capacitor 92 while the first switch 5 and the second switch 6 are turned off.

[0166] According to the power supply device 1b involved in this variant, similar to the embodiment, in the step-up / step-down action mode (diagnostic mode), after the first switch 5 and the second switch 6 are set to the cut-off state, the charge accumulated in the first electrostatic capacitor 91 is released and the voltage of the first electrostatic capacitor 91 decreases through the step-down action or the step-up action performed by the first DC / DC converter 41, and on the other hand, the charge accumulated in the second electrostatic capacitor 92 is released and the voltage of the second electrostatic capacitor 92 decreases through the step-up action or the step-down action performed by the second DC / DC converter 42.

[0167] Thus, compared to the prior art without the step-up operation or step-down operation performed by the first DC / DC converter 41 and the second DC / DC converter 42, when the cut-off capability of the first switch 5 is normal, the potential difference V5 across the first switch 5 increases in a short time, and when the cut-off capability of the second switch 6 is normal, the potential difference V6 across the second switch 6 increases in a short time. Thus, the cut-off capabilities of the first switch 5 and the second switch 6 can be diagnosed in a shorter time than before and at the same time.

[0168] In addition, the DC / DC converter included in the power supply device according to the present disclosure is not limited to a configuration consisting of two DC / DC converters connected in parallel. Fig. 9 As shown, the system may be composed of three or more DC / DC converters.

[0169] Fig. 9 1 is a block diagram showing the configuration of a power supply device 1c according to a third variation of the embodiment. The power supply device 1c according to this variation includes: Figure 2 The DC / DC converter unit 4 in the power supply device 1 according to the embodiment shown is replaced with a DC / DC converter unit 4 c according to this modification. The following description will focus on the differences from the embodiment.

[0170] The DC / DC converter unit 4c includes a first DC / DC converter 41, a second DC / DC converter 42, and a third DC / DC converter 43 connected in parallel. The detailed structure of the third DC / DC converter 43 may be: Figure 2 The configuration of the first DC / DC converter 41 according to the embodiment shown may also be Figure 7 The configuration of the first DC / DC converter 41 a according to the first modification example shown above may also be configured by other types of circuits.

[0171] In the power supply device 1 c according to the present modification, in addition to the operation control in the embodiment, the following operation control can be performed.

[0172] That is, when the first voltage supplied from the first DC power supply 2 is charged to the second DC power supply 3, the control unit 7 controls so that when the first switch 5 and the second switch 6 are turned on, the first DC / DC converter 41, the second DC / DC converter 42 and the third DC / DC converter 43 in parallel boost or step down the first voltage supplied from the first DC power supply 2 to the second voltage and output it to the second DC power supply 3.

[0173] In addition, when the second voltage supplied from the second DC power supply 3 is charged to the first DC power supply 2, the control unit 7 controls so that when the first switch 5 and the second switch 6 are turned on, the first DC / DC converter 41, the second DC / DC converter 42 and the third DC / DC converter 43 in parallel boost or step down the second voltage supplied from the second DC power supply 3 to the first voltage and output it to the first DC power supply 2.

[0174] In addition, as a step-up or step-down action (diagnostic mode), the control unit 7 controls so that when the first switch 5 and the second switch 6 are disconnected, one or two DC / DC converters among the first DC / DC converter 41 to the third DC / DC converter 43 step up or step down the voltage of the first electrostatic capacitor 91 and output it to the second electrostatic capacitor 92, and in parallel, the remaining two or one DC / DC converters step up or step down the voltage of the second electrostatic capacitor 92 and output it to the first electrostatic capacitor 91.

[0175] Thus, after the first switch 5 and the second switch 6 are in the cut-off state, the charge accumulated in the first electrostatic capacitor 91 is released and the voltage of the first electrostatic capacitor 91 decreases through the operation of one or two DC / DC converters. On the other hand, the charge accumulated in the second electrostatic capacitor 92 is released and the voltage of the second electrostatic capacitor 92 decreases through the operation of two or one DC / DC converters.

[0176] Thus, compared to the prior art in which no DC / DC converter is used, when the first switch 5 has a normal disconnection capability, the potential difference V5 across the first switch 5 increases in a short time, and when the second switch 6 has a normal disconnection capability, the potential difference V6 across the second switch 6 increases in a short time. Thus, the disconnection capabilities of the first switch 5 and the second switch 6 can be diagnosed simultaneously in a shorter time than before.

[0177] Industrial Applicability

[0178] The power supply device involved in the present disclosure can be used as a power supply device that is connected between two DC power supplies and converts voltage, and in particular, can be used as a power supply device that can diagnose the disconnection capacity of switches connected between each of the two DC power supplies and the power supply device in a shorter time than before, for example, as a voltage conversion device that is mounted on a vehicle and connected between a battery and a double electric layer capacitor serving as a backup therefor.

[0179] Description of reference numerals:

[0180] 1. 1a~1c power supply device

[0181] 21st DC power supply

[0182] 3. Second DC power supply

[0183] 4. 4a~4c DC / DC converter unit

[0184] 41, 41a, 41b 1st DC / DC converter

[0185] 411 1st switch element

[0186] 412 2nd switch element

[0187] 413 No.1 Reactor

[0188] 414 No.1 Current Sensor

[0189] 415 5th switch element

[0190] 416 6th switch element

[0191] 417 9th switch element

[0192] 418 No. 10 Switching Element

[0193] 419 No.1 Transformer

[0194] 42, 42a, 42b second DC / DC converter

[0195] 421 3rd switch element

[0196] 422 4th switch element

[0197] 423 Second Reactor

[0198] 424 2nd current sensor

[0199] 425 7th switch element

[0200] 426 8th switch element

[0201] 427 11th switch element

[0202] 428 12th switch element

[0203] 429 No. 2 Transformer

[0204] 433DC / DC Converter

[0205] 51st switch

[0206] 51 first potential detection unit

[0207] 52 second potential detection unit

[0208] 6 2nd switch

[0209] 61 3rd potential detection unit

[0210] 62 4th potential detection unit

[0211] 7. Control Unit

[0212] 8Diagnosis Department

[0213] 91 No.1 Electrostatic Capacitor

[0214] 92 2nd electrostatic capacitance

[0215] 100 vehicles

Claims

1. A power supply device, configured to be connected to a first DC power supply for supplying and maintaining a first voltage and a second DC power supply for supplying and maintaining a second voltage lower than the first voltage, comprising: a first switch, one end of which is connected to the first DC power source; a first electrostatic capacitor connected between the other end of the first switch and a reference potential; a second switch, one end of which is connected to the second DC power supply; a second electrostatic capacitor connected between the other end of the second switch and the reference potential; a first DC / DC converter connected between the other end of the first switch and the other end of the second switch; a second DC / DC converter connected in parallel with the first DC / DC converter between the other end of the first switch and the other end of the second switch; and a control unit configured to control the first switch, the second switch, the first DC / DC converter, and the second DC / DC converter, The control unit has: a step-down operation mode for performing step-down control, in which, with the first switch and the second switch turned on, the first DC / DC converter and the second DC / DC converter step down the first voltage supplied from the first DC power supply to the second voltage in parallel and output it to the second DC power supply; a boost operation mode for performing boost control, in which, with the first switch and the second switch turned on, the first DC / DC converter and the second DC / DC converter are operated in parallel to boost the second voltage supplied from the second DC power supply to the first voltage and output the voltage to the first DC power supply; as well as A step-up / step-down action mode for performing step-up / step-down control, in which, with the first switch and the second switch disconnected, the first DC / DC converter steps down the voltage of the first electrostatic capacitor and outputs it to the second electrostatic capacitor, and in parallel, the second DC / DC converter steps up the voltage of the second electrostatic capacitor and outputs it to the first electrostatic capacitor.

2. The power supply device according to claim 1, further comprising: a first potential difference detection unit configured to detect a first potential difference between both ends of the first switch; and a second potential difference detection unit configured to detect a second potential difference between both ends of the second switch; The control unit is configured so that, in the step-up / step-down operation mode, After the step-up / step-down control, it is determined whether the first potential difference detected by the first potential difference detection unit is larger than a first reference potential difference. When the first potential difference is greater than the first reference potential difference, it is determined that the first switch is normal. determining whether the second potential difference detected by the second potential difference detection unit is greater than a second reference potential difference, When the second potential difference is larger than the second reference potential difference, it is determined that the second switch is normal.

3. The power supply device according to claim 2, The control unit is configured so that, in the step-up / step-down operation mode, When the first potential difference is not greater than the first reference potential difference, it is determined that the first switch is abnormal. When the second potential difference is not greater than the second reference potential difference, it is determined that the second switch is abnormal.

4. The power supply device according to claim 2 or 3, The control unit is configured to, in the step-up / down operation mode, turn off the first switch and the second switch and then perform step-down of the first DC / DC converter and step-up of the second DC / DC converter for a certain period of time.

5. The power supply device according to any one of claims 1 to 4, The first DC / DC converter comprises: a first switching element and a first reactor connected in series with each other at a first connection point between the first switch and the second switch; and a second switching element having a body diode, connected between the first connection point and the reference potential, The second DC / DC converter has: a third switching element having a body diode and a second reactor connected in series with each other at a second connection point between the first switch and the second switch; and The fourth switch element is connected between the second connection point and the reference potential.

6. The power supply device according to claim 5, The control unit is configured to perform the step-up and step-down control in a state where the second switching element and the third switching element are always off in the step-up and step-down operation mode.

7. The power supply device according to any one of claims 1 to 6, further comprising: a current sensor for detecting a current flowing in one of the first DC / DC converter and the second DC / DC converter, The control unit is configured to control one of the first DC / DC converter and the second DC / DC converter in the step-down operation mode, the step-up operation mode, and the step-up / step-down operation mode so that the current detected by the current sensor is within a predetermined range.

8. The power supply device according to claim 5, further comprising: a first potential detection unit configured to detect a potential at the other end of the first switch; and a second potential detection unit for detecting a potential of the other end of the second switch; In the step-up / step-down operation mode, the control unit determining whether the first potential detected by the first potential detection unit is equal to or lower than a first reference potential, When the first potential is not lower than the first reference potential, it is determined that the first switching element is abnormally fixed in off state, determining whether the second potential detected by the second potential detection unit is equal to or lower than a second reference potential, When the second potential is not lower than the second reference potential, it is determined that the fourth switching element is abnormally fixed in off state.

9. The power supply device according to claim 8, The control unit is configured so that, in the step-up / step-down operation mode, When the first potential is lower than or equal to the first reference potential, it is determined that the first switching element is normal. When the second potential is equal to or lower than the second reference potential, it is determined that the fourth switching element is normal.

10. A method for diagnosing a power supply device, the power supply device being connected to a first DC power supply for supplying and maintaining a first voltage and a second DC power supply for supplying and maintaining a second voltage lower than the first voltage, The power supply device diagnosis method includes the step of preparing a power supply device, wherein the power supply device is configured to include: a first switch, one end of which is connected to the first DC power supply; a first electrostatic capacitor connected between the other end of the first switch and a reference potential; a second switch, one end of which is connected to the second DC power supply; a second electrostatic capacitor connected between the other end of the second switch and the reference potential; a first DC / DC converter connected between the other end of the first switch and the other end of the second switch; as well as The second DC / DC converter is connected between the other end of the first switch and the other end of the second switch. The power supply device performs a step-down control in which, in a state where the first switch and the second switch are turned on, the first DC / DC converter and the second DC / DC converter are operated in parallel to step down the first voltage supplied from the first DC power supply to the second voltage and output it to the second DC power supply, The power supply device performs a voltage boost control in which, in a state where the first switch and the second switch are turned on, the first DC / DC converter and the second DC / DC converter are operated in parallel to boost the second voltage supplied from the second DC power supply to the first voltage and output the voltage to the first DC power supply, The diagnostic method of the power supply device also includes the step of performing step-up and step-down control, in which, with the first switch and the second switch being disconnected, the first DC / DC converter steps down the voltage of the first electrostatic capacitor and outputs it to the second electrostatic capacitor, and in parallel, the second DC / DC converter steps up the voltage of the second electrostatic capacitor and outputs it to the first electrostatic capacitor.

11. The method for diagnosing a power supply device according to claim 10, The power supply device further comprises: a first potential difference detection unit for detecting a potential difference between both ends of the first switch; as well as a second potential difference detection unit for detecting a potential difference between both ends of the second switch; The diagnostic method of the power supply device further includes: After the step of performing the step of step-up / step-down control, a step of determining whether the first potential difference detected by the first potential difference detection unit is greater than a first reference potential difference; a step of determining that the first switch is normal when the first potential difference is greater than the first reference potential difference; After the step of performing the step of step-up / step-down control, a step of determining whether the second potential difference detected by the second potential difference detection unit is greater than a second reference potential difference; as well as A step of determining that the second switch is normal when the second potential difference is larger than the second reference potential difference.

12. The method for diagnosing a power supply device according to claim 11, further comprising: a step of determining that the first switch is abnormal when the first potential difference is not greater than the first reference potential difference; as well as A step of determining that the second switch is abnormal when the second potential difference is not greater than the second reference potential difference.

13. A method for diagnosing a power supply device, the power supply device being connected to a first DC power supply for supplying and maintaining a first voltage and a second DC power supply for supplying and maintaining a second voltage lower than the first voltage, The power supply device diagnosis method comprises the steps of preparing the power supply device, the power supply device comprising: a first switch, one end of which is connected to the first DC power supply; a first electrostatic capacitor connected between the other end of the first switch and a reference potential; a second switch, one end of which is connected to the second DC power supply; a second electrostatic capacitor connected between the other end of the second switch and the reference potential; a first DC / DC converter connected between the other end of the first switch and the other end of the second switch; as well as The second DC / DC converter is connected between the other end of the first switch and the other end of the second switch. The diagnostic method of the power supply device also includes the step of performing step-up and step-down control, in which, with the first switch and the second switch being disconnected, the first DC / DC converter steps down the voltage of the first electrostatic capacitor and outputs it to the second electrostatic capacitor, and in parallel, the second DC / DC converter steps up the voltage of the second electrostatic capacitor and outputs it to the first electrostatic capacitor.

14. The method for diagnosing a power supply device according to claim 13, The power supply device further comprises: a first potential difference detection unit for detecting a potential difference between both ends of the first switch; as well as a second potential difference detection unit for detecting a potential difference between both ends of the second switch; The diagnostic method of the power supply device further includes: After the step of performing the step of step-up / step-down control, a step of determining whether the first potential difference detected by the first potential difference detection unit is greater than a first reference potential difference; a step of determining that the first switch is normal when the first potential difference is greater than the first reference potential difference; After the step of performing the step of step-up / step-down control, a step of determining whether the second potential difference detected by the second potential difference detection unit is greater than a second reference potential difference; as well as A step of determining that the second switch is normal when the second potential difference is larger than the second reference potential difference.

15. The method for diagnosing a power supply device according to claim 14, further comprising: a step of determining that the first switch is abnormal when the first potential difference is not greater than the first reference potential difference; as well as A step of determining that the second switch is abnormal when the second potential difference is not greater than the second reference potential difference.

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