Power supply device and switch diagnosis method

Abstract

This power supply device is configured to be connected between a first DC power supply and a second DC power supply. The power supply device comprises: a first switch configured such that one end thereof is connected to the first DC power supply; a DC-DC converter having a first capacitor connected to the other end of the first switch; and a control unit configured to control the DC-DC converter and the first switch, and to detect a potential difference between the one end and the other end of the first switch. The DC-DC converter is configured to perform: a first action to convert a voltage stored by the first capacitor to a second voltage and output the converted second voltage to the second DC power supply; and / or a second action to convert the second voltage supplied and held by the second DC power supply to a third voltage and output the converted third voltage to the first capacitor. The control unit is configured to: detect a potential difference after issuing an instruction to shut off the first switch and causing the DC-DC converter to perform the first action or the second action; and determine that, when the detected potential difference is greater than a reference potential difference, the first switch is normal.

Description

How to diagnose power supplies and switches

[0001] The present disclosure relates to a power supply device connected between two DC power sources and a method for diagnosing a switch included in the power supply device.

[0002] A power supply device connected between two DC power sources (a first DC power source and a second DC power source) for converting power may include a DC-DC converter that converts the voltage on the input side (i.e., the first DC power source) to a desired voltage and outputs (i.e., charges) the voltage on the output side (i.e., the second DC power source). Such a power supply device generally includes a switch that connects or disconnects the DC-DC converter to components on the input side, and a switch that connects or disconnects the DC-DC converter to components on the output side, in order to protect the two components connected to both ends. Regarding the disconnection of the switch in particular, the switch is turned off and the potential difference between both ends of the switch is measured to diagnose whether the switch is in a state where it can be disconnected (i.e., whether the switch is normal).

[0003] As a prior art document disclosing such a conventional technique, for example, Patent Document 1 is known.

[0004] International Publication No. 2019 / 077958

[0005] In conventional power supply devices, the potential difference between both ends of the switch is measured after the switch is in the cut-off state to diagnose the cut-off capability of the switch. In other words, if the potential difference between both ends of the switch is greater than a predetermined potential difference, the cut-off capability of the switch is determined to be normal, and if not, the cut-off capability of the switch is determined to be abnormal.

[0006] However, if an electric charge (hereinafter referred to as "internal charge") is stored inside the DC-DC converter, the voltage caused by the accumulation of this internal charge will affect the potential difference between the two ends of the switch, and even if the switch is able to properly respond to an instruction to turn off the switch, it may not be possible to properly diagnose whether the switch is turned off.

[0007] In addition, in order to correctly diagnose the interruption state of the switch, leakage current from resistors in the DCDC converter or a decrease in internal charge due to spontaneous emission may be used. However, such methods may require a long time to discharge the internal charge of the DCDC converter, which may require a long waiting time to diagnose the interruption of the switch.

[0008] Furthermore, even when the voltage on the input or output side is held by a capacitor, if the voltage on the input or output side is equal to ground potential and the internal voltage of the DCDC converter is also equal to ground potential, the potential difference between both ends of the switch becomes small even if the switch is able to cut off in response to the cut-off state instruction, making it difficult to diagnose the cut-off ability of the switch from the potential difference between both ends of the switch.

[0009] To correctly diagnose the disconnection state of the switch, one possible method is to boost the voltage on the input or output side using the power supply, then disconnect the switch, wait for leakage current from resistors in the DCDC converter to decrease, or for internal charge to decrease due to natural discharge, and then diagnose the disconnection state of the switch. However, this method may require a long time to discharge the internal charge of the DCDC converter, and may require a long wait time before the power supply can start operating in order to diagnose the disconnection of the switch.

[0010] In view of the above-mentioned problems, the present disclosure aims to provide a power supply device and a switch diagnostic method that can quickly diagnose the interruption performance of a switch provided between the input side or output side and a DC-DC converter provided in the power supply device.

[0011] According to one aspect of the present disclosure, a power supply device is configured to be connected between 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. The power supply device includes a first switch configured to have one end connected to the first DC power supply, a DC-DC converter having a first capacitance connected to the other end of the first switch, and a control unit configured to control the DC-DC converter and the first switch and detect a potential difference between one end and the other end of the first switch. The DC-DC converter is configured to perform at least one of a first operation of converting a voltage stored in the first capacitance to a second voltage and outputting the converted second voltage to the second DC power supply, and a second operation of converting the second voltage supplied and maintained by the second DC power supply to a third voltage and outputting the converted third voltage to the first capacitance. The control unit is configured to instruct the DC-DC converter to turn off the first switch and perform the first or second operation, and then detect the potential difference, and determine that the first switch is normal if the detected potential difference is greater than a reference potential difference.

[0012] In the power supply device diagnostic method according to one aspect of the present disclosure, after instructing the DC-DC converter to perform the first operation or the second operation by turning off the switch, a potential difference between the first end and the other end of the switch is detected, and if the detected potential difference is greater than a reference potential difference, the switch is determined to be normal.

[0013] The present disclosure provides a power supply device and a switch diagnostic method that can quickly diagnose the interruption performance of a switch provided between the input side or output side and a DC-DC converter included in the power supply device.

[0014] FIG. 1A is a diagram illustrating a configuration of a power supply device according to an embodiment. FIG. 1B is a diagram illustrating a flowchart of a process for diagnosing the interruption performance of a first switch, which is part of the operation of the power supply device according to the embodiment. FIG. 1C is a diagram illustrating a flowchart of a process for diagnosing the interruption performance of a second switch, which is part of the operation of the power supply device according to the embodiment. FIG. 2 is a diagram illustrating a configuration example of a power supply device according to a first modified example of the embodiment. FIG. 3 is a diagram illustrating a configuration example of a power supply device according to a second modified example of the embodiment. FIG. 4 is a diagram illustrating a configuration example of a power supply device according to a third modified example of the embodiment. FIG. 5 is a diagram illustrating a configuration example of a power supply device according to a fourth modified example of the embodiment. FIG. 6 is a diagram illustrating a configuration example of a power supply device according to a fifth modified example of the embodiment. FIG. 7 is a diagram illustrating a circuit of a DC-DC converter according to a first specific example of the power supply device according to the embodiment. FIG. 8 is a diagram illustrating a circuit of a DC-DC converter according to a second specific example of the power supply device according to the embodiment. FIG. 9 is a diagram illustrating a circuit of a DC-DC converter according to a third specific example of the power supply device according to the embodiment.

[0015] Hereinafter, embodiments of a power supply device according to the present disclosure will be described with reference to the drawings. Note that the embodiments disclosed below are all examples and are not intended to impose limitations on the power supply device according to the present disclosure.

[0016] Furthermore, in the embodiments disclosed below, more detailed explanation than necessary may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the explanation and to facilitate understanding by those skilled in the art. Furthermore, "A and B are connected" means that A and B are electrically connected, and includes not only cases where A and B are directly connected, but also cases where A and B are indirectly connected with another circuit element sandwiched between them.

[0017] Fig. 1A is a block diagram showing the configuration of a power supply device 1 according to an embodiment. In this embodiment, the power supply device 1 is mounted on a vehicle 100. As shown in Fig. 1A, the power supply device 1 according to the embodiment includes a first DC power supply 2, a second DC power supply 3, a DC-DC converter 4, a first switch 5, a second switch 6, a control unit 7 having a diagnostic unit 8, a first voltage detection unit 51, a second voltage detection unit 52, a third voltage detection unit 61, and a fourth voltage detection unit 62.

[0018] For the sake of convenience, the control unit 7 includes the diagnostic unit 8. However, the control unit 7 and the diagnostic unit 8 may be separate elements. The first voltage detection unit 51, the second voltage detection unit 52, the third voltage detection unit 61, and the fourth voltage detection unit 62 may be incorporated in the diagnostic unit 8.

[0019] The first DC power supply 2 is capable of outputting (i.e., supplying and maintaining) a first voltage and is, for example, a battery. The second DC power supply 3 is capable of outputting (i.e., supplying and maintaining) a second voltage and is, for example, an electric double layer capacitor.

[0020] Furthermore, a DC-DC converter 4 is connected between the first DC power supply 2 and the second DC power supply 3. The DC-DC converter 4 has a first capacitance 91 capable of storing a first voltage, a second capacitance 92 capable of storing a second voltage, a current sensor 42 that measures the current flowing through the DC-DC converter 4, and a power conversion circuit 41 that performs DC voltage conversion to step down the first voltage to a second voltage and to step up the second voltage to the first voltage.

[0021] The DCDC converter 4 steps down the first voltage input from the first DC power supply 2 and outputs the stepped-down voltage to the second DC power supply 3. Also, the DCDC converter 4 steps up the second voltage input from the second DC power supply 3 and outputs the stepped-up voltage to the first DC power supply 2. In the present embodiment, the DCDC converter 4 steps down the first voltage input from the first DC power supply 2 and outputs it to the second DC power supply 3, and steps up the second voltage input from the second DC power supply 3 and outputs it to the first DC power supply 2. However, conversely, the DCDC converter 4 may step up the first voltage input from the first DC power supply 2 and output it to the second DC power supply 3, and step down the second voltage input from the second DC power supply 3 and output it to the first DC power supply 2.

[0022] Furthermore, a first switch 5 is connected between the first DC power supply 2 and the DCDC converter 4, and is capable of connecting and disconnecting the first DC power supply 2 and the DCDC converter 4.

[0023] A second switch 6 is connected between the second DC power supply 3 and the DC-DC converter 4, and allows the second DC power supply 3 and the DC-DC converter 4 to be connected or disconnected.

[0024] The first switch 5 and the second switch 6 are, for example, semiconductor switches such as metal oxide film field effect transistors (MOSFETs) or contactors such as electromagnetic relays.

[0025] The first voltage detection unit 51, the second voltage detection unit 52, the third voltage detection unit 61, and the fourth voltage detection unit 62 are voltmeters, and are, for example, analog-to-digital (A / D) converters.

[0026] The control unit 7 can instruct the DCDC converter 4 to perform step-down control to step down the voltage input to the DCDC converter 4 (i.e., step down the first voltage and output it to the second DC power supply 3) or step-up control to step up the voltage (i.e., step up the second voltage and output it to the first DC power supply 2). The control unit 7 can also instruct the first switch 5 to connect or disconnect the first DC power supply 2 and the DCDC converter 4. The control unit 7 can also instruct the second switch 6 to connect or disconnect the second DC power supply 3 and the DCDC converter 4.

[0027] Furthermore, the control unit 7 can cause the diagnosis unit 8 to measure the voltage across the first switch 5 or the potential difference between the two ends.

[0028] As a result, when it is desired to diagnose the breaking performance of the first switch 5, the control unit 7 issues a break instruction to the first switch 5 and a connect instruction to the second switch 6, and then the DCDC converter 4 performs a voltage conversion operation and discharges the charge of the first capacitance 91 to the second DC power supply 3. Therefore, it is possible to provide a power supply device 1 that can diagnose the breaking performance of the first switch 5 in a short time.

[0029] The control unit 7 and the diagnosis unit 8 are realized by a memory that stores a program, a processor that executes the program, an A / D converter, a timer, and the like.

[0030] Next, the overall operation of the power supply device 1 will be described.

[0031] First, normal voltage conversion operation will be described. The normal voltage conversion operation is an operation of stepping down the first voltage of the first DC power supply 2 to a second voltage and outputting the second voltage to the second DC power supply 3, and an operation of stepping up the second voltage of the second DC power supply 3 to the first voltage and outputting the first voltage to the first DC power supply 2.

[0032] For example, when the vehicle 100 equipped with the power supply device 1 begins to start up or while the vehicle 100 is already running, the control unit 7 instructs the first switch 5 to connect the first DC power supply 2 and the DCDC converter 4. The control unit 7 also instructs the second switch 6 to connect the second DC power supply 3 and the DCDC converter 4.

[0033] The first switch 5 connects the first DC power supply 2 and the DCDC converter 4 based on an instruction from the control unit 7. The second switch 6 connects the second DC power supply 3 and the DCDC converter 4 based on an instruction from the control unit 7.

[0034] The voltage input to the DCDC converter 4 from the first DC power supply 2 or the second DC power supply 3 is converted based on a signal from the control unit 7 to the DCDC converter 4. At this time, the first capacitance 91 is charged to the first voltage of the first DC power supply 2. Also, the second capacitance 92 is charged to the second voltage of the second DC power supply 3.

[0035] Next, a diagnostic operation for the function of cutting off the connection with the outside after the normal voltage conversion operation described above is explained.

[0036] First, the case where the interruption performance of the first switch 5 is diagnosed will be described.

[0037] FIG. 1B is a flowchart of a process for diagnosing the interruption performance of the first switch 5 (that is, a switch diagnosis method) in the operation of the power supply device 1 according to the embodiment.

[0038] The control unit 7 instructs the first switch 5 to disconnect the first DC power supply 2 from the DCDC converter 4. Based on the instruction from the control unit 7, the first switch 5 instructs the first switch 5 to disconnect the first DC power supply 2 from the DCDC converter 4 (S10).

[0039] The control unit 7 also instructs the second switch 6 to connect the second DC power supply 3 and the DCDC converter 4. Based on the instruction from the control unit 7, the second switch 6 connects the second DC power supply 3 and the DCDC converter 4 (S11). The order of steps S10 and S11 may be reversed from that shown in Fig. 1B, or steps S10 and S11 may be performed simultaneously.

[0040] Next, the control unit 7 operates the DCDC converter 4 to discharge the charge stored in the first capacitance 91 of the DCDC converter 4 to the second DC power supply 3 (S12). Specifically, the control unit 7 instructs the DCDC converter 4 to perform a voltage step-down operation, and discharges the charge stored in the first capacitance 91 of the DCDC converter 4 to the second DC power supply 3.

[0041] Next, the diagnostic unit 8 measures voltages at two locations across the first switch 5 using the first voltage detection unit 51 and the second voltage detection unit 52, and calculates the potential difference across the first switch 5 (S13). If the potential difference across the first switch 5 calculated by the diagnostic unit 8 is not greater than the reference value (No in S14), it is confirmed that the first switch 5 has not been able to disconnect the first DC power supply 2 from the DCDC converter 4, and the first switch 5 is determined to be abnormal rather than normal (S15). If the potential difference across the first switch 5 calculated by the diagnostic unit 8 is greater than the reference value (Yes in S14), it is confirmed that the first switch 5 has been able to disconnect the first DC power supply 2 from the DCDC converter 4, and the first switch 5 is determined to be normal (S16). This makes it possible to determine whether the disconnection function of the first switch 5 is operating normally. The control unit 7 outputs a determination signal based on the result of the determination of whether the first switch 5 is normal, for example, to an electronic control unit (ECU) mounted on the vehicle 100. The ECU performs an operation (display, control, etc.) in accordance with the determination signal.

[0042] As described above, in this embodiment, when the control unit 7 instructs the first switch 5 to disconnect the first DC power supply 2 and the DCDC converter 4, the control unit 7 causes the DCDC converter 4 to discharge the charge stored in the first capacitance 91 connected between the first switch 5 and ground in the DCDC converter 4. As a result, when the first switch 5 is disconnected, the potential difference across the first switch 5 can be made larger than when the charge is not discharged, and the diagnostic unit 8 can easily and reliably diagnose the first switch 5.

[0043] Here, when the control unit 7 instructs the first switch 5 to disconnect the first DC power supply 2 and the DCDC converter 4, the charge stored in the first capacitance 91 remains. In other words, the first switch 5 is simply disconnected. At this time, when the diagnostic unit 8 measures the potential difference between both ends of the first switch 5, because charge remains in the first capacitance 91, the potential difference between both ends of the first switch 5 is smaller than in the power supply device 1 of the present disclosure, even if the first switch 5 is normally disconnected. For this reason, the diagnostic unit 8 cannot determine whether the first switch 5 is normally disconnected.

[0044] Furthermore, because charge naturally dissipates from the first capacitance 91 over time due to leakage current from the resistor connected in parallel and the DCDC converter 4, it is possible to determine whether the first switch 5 has been properly shut off by measuring the potential difference between both ends of the first switch 5 after a certain period of time has elapsed. However, in the power supply device 1 of the present disclosure, after the control unit 7 instructs the first switch 5 to shut off the first DC power supply 2 and the DCDC converter 4, the control unit 7 instructs the DCDC converter 4 to perform voltage conversion, thereby actively discharging the charge from the first capacitance 91 in a short period of time. This allows the charge from the first capacitance 91 to be discharged in a significantly shorter time than the natural discharge of charge, making it possible to determine whether the first switch 5 has been properly shut off in a shorter time than the natural discharge.

[0045] Next, a case where the interruption performance of the second switch 6 is diagnosed will be described.

[0046] FIG. 1C is a flowchart of a process for diagnosing the interruption performance of the second switch 6 (i.e., a switch diagnosis method) in the operation of the power supply device 1 according to the embodiment.

[0047] The control unit 7 instructs the second switch 6 to disconnect the second DC power supply 3 and the DCDC converter 4. Based on the instruction from the control unit 7, the second switch 6 instructs the second switch 6 to disconnect the second DC power supply 3 and the DCDC converter 4 (S20).

[0048] Furthermore, the control unit 7 instructs the first switch 5 to connect the first DC power supply 2 and the DCDC converter 4. Based on the instruction from the control unit 7, the first switch 5 connects the first DC power supply 2 and the DCDC converter 4 (S21). The order of steps S20 and S21 may be reversed from that shown in Fig. 1C, or steps S20 and S21 may be performed simultaneously.

[0049] Next, the control unit 7 operates the DCDC converter 4 to discharge the charge stored in the second capacitance 92 of the DCDC converter 4 to the first DC power supply 2 (S22). Specifically, the control unit 7 instructs the DCDC converter 4 to perform a boost operation, and discharges the charge stored in the second capacitance 92 of the DCDC converter 4 to the first DC power supply 2.

[0050] Next, the diagnostic unit 8 measures voltages at two locations, namely, both ends of the second switch 6 and the third and fourth voltage detection units 61 and 62, and thereby calculates a potential difference across the second switch 6 (S23). If the potential difference across the second switch 6 calculated by the diagnostic unit 8 is not greater than the reference value (No in S24), it is confirmed that the second switch 6 has not been able to disconnect the second DC power supply 3 and the DCDC converter 4, and it is determined that the second switch 6 is not normal but abnormal (S25). On the other hand, if the potential difference across the second switch 6 measured by the diagnostic unit 8 is greater than the reference value (Yes in S24), it is confirmed that the second switch 6 has been able to disconnect the second DC power supply 3 and the DCDC converter 4, and it is determined that the second switch 6 is normal (S26). If the potential difference across the second switch 6 measured by the diagnostic unit 8 is not greater than the reference value (No in S24), it can be confirmed that the second switch 6 has not been able to cut off the connection between the second DC power supply 3 and the DCDC converter 4, and it is determined that the second switch 6 is not normal but abnormal (S26). This makes it possible to determine whether the cut-off function of the second switch 6 is operating normally. The control unit 7 outputs a determination signal to, for example, an electronic control unit (ECU) mounted on the vehicle 100, depending on the result of the determination as to whether the second switch 6 is normal. The ECU performs an operation (display, control, etc.) according to the determination signal.

[0051] As described above, in this embodiment, when the control unit 7 instructs the second switch 6 to disconnect the second DC power supply 3 and the DCDC converter 4, the control unit 7 causes the DCDC converter 4 to discharge the charge stored in the second capacitance 92 connected between the second switch 6 and the ground in the DCDC converter 4. As a result, when the second switch 6 is disconnected, the potential difference across the second switch 6 can be made larger than when the charge is not discharged, and the diagnostic unit 8 can easily and reliably diagnose the second switch 6.

[0052] Here, when the control unit 7 instructs the second switch 6 to disconnect the second DC power supply 3 and the DCDC converter 4, the charge stored in the second capacitance 92 remains. In other words, the second switch 6 is simply disconnected. At this time, when the diagnostic unit 8 measures the potential difference between both ends of the second switch 6, because charge remains in the second capacitance 92, the potential difference between both ends of the second switch 6 is smaller than in the power supply device 1 of the present disclosure, even if the second switch 6 is normally disconnected. For this reason, the diagnostic unit 8 cannot determine whether the second switch 6 is normally disconnected.

[0053] Furthermore, in conventional power supplies, charge in the second capacitance 92 is naturally released over time due to leakage current from the resistor connected in parallel and the DCDC converter 4, so that it is possible to determine whether the second switch 6 has been properly shut off by measuring the potential difference between both ends of the second switch 6 after a certain period of time has elapsed. However, in the power supply device 1 of the present disclosure, after the control unit 7 instructs the second switch 6 to shut off the second DC power supply 3 and the DCDC converter 4, the control unit 7 instructs the DCDC converter 4 to perform voltage conversion, thereby actively releasing the charge in the second capacitance 92 in a short period of time. This allows the charge in the second capacitance 92 to be released in a significantly shorter time than the natural release of charge, so that it is possible to determine whether the second switch 6 has been properly shut off in a shorter time than in the conventional power supply.

[0054] The reference values ​​of the potential difference between both ends of the first switch 5 and the second switch 6 are determined based on the cut-off characteristics of the elements or parts used in the first switch 5 and the second switch 6 .

[0055] It should be noted that a capacitor may be substituted for the first DC power supply 2. The first voltage does not necessarily have to be supplied from an active power supply, and a capacitor may be charged by the DCDC converter 4, and the voltage after charging may be used as the first voltage. This allows the power supply of the vehicle 100 to be constituted by only the second DC power supply 3, resulting in a vehicle configuration that is advantageous in terms of cost, component arrangement, weight, and the like.

[0056] It should be noted that a capacitor may be substituted for the second DC power supply 3. The second voltage does not necessarily have to be supplied from an active power supply, and a capacitor may be charged by the DCDC converter 4, and the voltage after charging may be used as the second voltage. This allows the power supply of the vehicle 100 to be constituted by only the first DC power supply 2, resulting in a vehicle configuration that is advantageous in terms of cost, component arrangement, weight, etc.

[0057] 2, a fifth voltage detection unit 53 that directly measures the potential difference between both ends of the first switch 5 may be provided in place of the first voltage detection unit 51 and the second voltage detection unit 52 in FIG. 1A. The fifth voltage detection unit 53 is, for example, an A / D converter.

[0058] 2, instead of the third voltage detection unit 61 and the fourth voltage detection unit 62 in FIG. 1A, a sixth voltage detection unit 63 may be provided that directly measures the potential difference between both ends of the second switch 6. The sixth voltage detection unit 63 is, for example, an A / D converter.

[0059] In the embodiment, when diagnosing the interruption performance of the first switch 5, the DCDC converter 4 may operate to control the voltage of the first capacitance 91. Specifically, after the control unit 7 instructs the first switch 5 to interrupt the connection between the first DC power source 2 and the DCDC converter 4, the control unit 7 instructs the DCDC converter 4 to perform voltage conversion. At this time, the voltage of the first capacitance 91 is controlled using the voltage of the first capacitance 91 detected by the second voltage detection unit 52 in FIG. 1A , so that the voltage of the first capacitance 91 can be controlled (i.e., set) to an arbitrary voltage.

[0060] When the first switch 5 is connected, in order to reduce the rush current that flows through the first switch 5 when the first switch 5 is connected, the first capacitance 91 is charged in advance so that the voltage becomes close to that of the first DC power supply 2, and then the first switch 5 is connected.

[0061] Therefore, when determining whether the cut-off function of the first switch 5 is operating normally, if all the charge in the first capacitance 91 is discharged, when the first switch 5 is connected again, the first capacitance 91 is charged to the voltage of the first DC power source 2.

[0062] On the other hand, if the voltage of the first capacitance 91 is controlled to an arbitrary voltage other than zero, the charging time when the first switch 5 is closed again can be shortened.

[0063] For example, when the voltage of the first capacitance 91 is controlled to an arbitrary voltage other than zero, the first voltage detection unit 51 is used to monitor that voltage, and by controlling the voltage of the second voltage detection unit 52 to maintain a potential difference necessary for determining whether the cut-off function of the first switch 5 is operating normally, for example, by controlling the voltage of the first capacitance 91 to a voltage that is lower than the first voltage by a reference value for determination, the charge discharge of the first capacitance 91 can be minimized to the minimum necessary for determining the cut-off function of the first switch 5. This makes it possible to shorten the time required to determine the cut-off function and the charging time required to reconnect the first switch 5.

[0064] Similarly, when diagnosing the interruption performance of the second switch 6, the DCDC converter 4 may operate to control the voltage of the second capacitance 92. Specifically, after the control unit 7 instructs the second switch 6 to interrupt the connection between the second DC power source 3 and the DCDC converter 4, the control unit 7 instructs the DCDC converter 4 to perform voltage conversion. At this time, the voltage of the second capacitance 92 is controlled using the voltage of the second capacitance 92 detected by the third voltage detection unit 61, so that the voltage of the second capacitance 92 can be controlled (i.e., set) to an arbitrary voltage.

[0065] When the second switch 6 is connected, in order to reduce the rush current that flows through the second switch 6 when the second switch 6 is connected, the second capacitance 92 is charged in advance so that the voltage approaches that of the second DC power supply 3, and then the second switch 6 is connected.

[0066] Therefore, when determining whether the cut-off function of the second switch 6 is operating normally, if all the charge in the second capacitance 92 is discharged, when the second switch 6 is connected again, the second capacitance 92 is charged to the voltage of the second DC power source 3.

[0067] On the other hand, if the voltage of the second capacitance 92 is controlled to an arbitrary voltage other than zero, the charging time when the second switch 6 is closed again can be shortened.

[0068] For example, when the voltage of the second capacitance 92 is controlled to an arbitrary voltage other than zero, the fourth voltage detection unit 62 is used to monitor that voltage, and by controlling the voltage with respect to the voltage of the third voltage detection unit 61 to maintain a potential difference necessary for determining whether the cut-off function of the second switch 6 is operating normally, for example, by controlling the voltage of the second capacitance 92 to a voltage that is lower than the second voltage by a reference value for determination, the charge discharge of the second capacitance 92 can be minimized to the minimum necessary for determining the cut-off function of the second switch 6. This makes it possible to shorten the time required to determine the cut-off function and the charging time required to reconnect the second switch 6.

[0069] The diagnostic unit 8 may use the current sensor 42 to detect the current flowing through the power conversion circuit 41 of the DCDC converter 4. After the control unit 7 instructs the first switch 5 to disconnect the first DC power supply 2 and the DCDC converter 4, or after the control unit 7 instructs the second switch 6 to disconnect the second DC power supply 3 and the DCDC converter 4, the control unit 7 instructs the DCDC converter 4 to perform voltage conversion. At this time, the DCDC converter 4 is controlled to control the current so that the current detected by the current sensor 42 is equal to or less than a specified current, or the DCDC converter 4 detects that the current has exceeded the specified current and stops conversion. This makes it possible to prevent excessive power from being supplied to the first DC power supply 2 or the second DC power supply 3 or an excessive current from flowing, even if the interruption performance of the first switch 5 or the second switch 6 to be diagnosed has been lost.

[0070] In addition, as in the configuration example of the power supply device 1b according to the second modification of the embodiment shown in Figure 3, the power supply device 1b does not have the second switch 6 of the embodiment and is composed only of the first switch 5, and the DC-DC converter 4a is composed only of the first capacitance 91 and the power conversion circuit 41, it is also possible to diagnose the interruption performance of the first switch 5.

[0071] Similarly, in a power supply device 1c according to the third modified example of the embodiment shown in Figure 4, which does not have a first switch 5 and is composed only of a second switch 6, and in which the DC-DC converter 4b is composed only of a second capacitance 92 and a power conversion circuit 41, the interruption performance of the second switch 6 can also be diagnosed.

[0072] Furthermore, even when each of the first switch 5 a and the second switch 6 a is configured with a single MOSFET, as in the configuration example of the power supply device 1 d according to the fourth modification of the embodiment shown in FIG. 5, the interruption performance of the first switch 5 a and the second switch 6 a can be diagnosed using a method similar to that of the above embodiment.

[0073] The first switch 5a is configured as a MOSFET having a body diode as shown in the figure, with the forward direction being from the DCDC converter 4 toward the first DC power supply 2, and therefore has the function of interrupting the current flowing from the first DC power supply 2 to the DCDC converter 4, but does not have the function of interrupting the current flowing from the DCDC converter 4 to the first DC power supply 2. Even with this type of first switch 5a, in the embodiment, the voltage of the first capacitance 91 is lowered after the first switch 5a is interrupted in diagnosing the interrupting performance, so that the interrupting performance of the first switch 5a can be diagnosed.

[0074] Similarly, the second switch 6a is configured as a MOSFET having a body diode as shown in the figure, with the forward direction being from the DCDC converter 4 to the second DC power supply 3, and therefore has the function of interrupting the current flowing from the second DC power supply 3 to the DCDC converter 4, but does not have the function of interrupting the current flowing from the DCDC converter 4 to the second DC power supply 3. Even with such a second switch 6a, in the embodiment, the voltage of the second capacitance 92 is lowered after the second switch 6a is interrupted in diagnosing the interrupting performance, so that the interrupting performance of the second switch 6a can be diagnosed.

[0075] FIG. 6 is a diagram showing an example of the configuration of a power supply device 1e according to a fifth modification of the embodiment.

[0076] The power supply device 1e includes a first DC power supply 2, a second DC power supply 3, a DCDC converter 4, a first switch 5b, a second switch 6b, a control unit 7a having a diagnostic unit 8, a first voltage detection unit 51, a second voltage detection unit 52, a third voltage detection unit 61, and a fourth voltage detection unit 62. The same components as those in the embodiment are given the same reference numerals and their description will be omitted, and the following description will focus on the differences from the above embodiment.

[0077] The first switch 5b is configured by connecting two MOSFETs in series, each having body diodes in opposite forward directions, as shown in Fig. 6. Similarly, the second switch 6b is configured by connecting two MOSFETs in series, each having body diodes in opposite forward directions, as shown in Fig. 6, and is also capable of blocking current in both directions.

[0078] In addition to the functions described in the embodiment, the control unit 7a and the DCDC converter 4 have the following functions in this modification.

[0079] In other words, when diagnosing the first switch 5b, after the control unit 7a issues a disconnection instruction to the first switch 5b, the DCDC converter 4 performs voltage conversion by boosting the voltage of the second capacitance 92 and outputting it to the first capacitance 91, thereby charging the first capacitance 91.

[0080] In addition, when diagnosing the second switch 6b, after the control unit 7a issues a disconnection instruction to the second switch 6b, the DCDC converter 4 performs voltage conversion by reducing the voltage of the first capacitance 91 and outputting it to the second capacitance 92, thereby charging the second capacitance 92.

[0081] Therefore, it is possible to provide a power supply device 1e that can diagnose the interruption performance of the first switch 5b that interrupts the first DC power supply 2 and the DC-DC converter 4, and the second switch 6b that interrupts the second DC power supply 3 and the DC-DC converter 4 in a short period of time.

[0082] Next, the overall operation of the power supply device 1e will be described.

[0083] The normal voltage conversion operation is the same as in the embodiment.

[0084] The operation when the connection with the outside is cut off after the normal voltage conversion operation is performed will be described.

[0085] The control unit 7a instructs the first switch 5b to disconnect the first DC power supply 2 and the DCDC converter 4. Based on the instruction from the control unit 7a, the first switch 5b disconnects the first DC power supply 2 and the DCDC converter 4. At this time, for example, the control unit 7a further switches the target of voltage detection and monitoring to the first capacitance 91, and detects and monitors the voltage of the first capacitance 91.

[0086] Next, the control unit 7a operates the DCDC converter 4 and controls the voltage of the first capacitance 91 of the DCDC converter 4 so that it is higher than the voltage of the first DC power supply 2. Specifically, the control unit 7a instructs the DCDC converter 4 to perform a boost operation, boosts the voltage of the second DC power supply 3 using the DCDC converter 4, and controls the voltage of the first capacitance 91 so that it is higher than the voltage of the first DC power supply 2. At this time, by setting the first capacitance 91 as the controlled object of power conversion, the voltage of the first capacitance 91 can be controlled to an arbitrary voltage higher than zero by the existing DCDC converter 4.

[0087] Next, the diagnostic unit 8 measures the potential difference between both ends of the first switch 5b. If the potential difference between both ends of the first switch 5b measured by the diagnostic unit 8 is equal to or less than a reference value, it can be confirmed that the first switch 5b has not been able to disconnect the first DC power supply 2 and the DCDC converter 4 in a state where it is unable to properly respond to instructions from the control unit 7a. Furthermore, if the potential difference between both ends of the first switch 5b measured by the diagnostic unit 8 is greater than the reference value, it can be confirmed that the first switch 5b has been able to disconnect the first DC power supply 2 and the DCDC converter 4 in a state where it is able to properly respond to instructions from the control unit 7a. This makes it possible to determine whether the first switch 5b has been able to properly disconnect the first DC power supply 2 and the DCDC converter 4.

[0088] 5 according to the fourth modification is configured with a single MOSFET, and therefore generally, even when the first switch 5a is controlled to be in an off state, the first switch 5a does not have the ability to cut off current flowing in the direction from the DCDC converter 4 to the first DC power supply 2 due to the body diode, and therefore only cuts off current flowing in the direction from the first DC power supply 2 to the DCDC converter 4. In contrast, when the first switch 5b according to the present modification shown in FIG. 6 has the ability to cut off current flowing in the direction from the DCDC converter 4 to the first DC power supply 2, the method of this modification can diagnose the cutting performance for current flowing in the direction from the DCDC converter 4 to the first DC power supply 2.

[0089] In the explanation of the operation when the connection to the outside is cut off, the control unit 7a instructs the first switch 5b to cut off the first DC power supply 2 and the DCDC converter 4, but the same operation occurs when the control unit 7a instructs the second switch 6b to cut off the second DC power supply 3 and the DCDC converter 4.

[0090] That is, the control unit 7a instructs the second switch 6b to disconnect the second DC power supply 3 and the DCDC converter 4. Based on the instruction from the control unit 7a, the second switch 6b disconnects the second DC power supply 3 and the DCDC converter 4. At this time, for example, the control unit 7a further switches the target of voltage detection and monitoring to the second capacitance 92, and detects and monitors the voltage of the second capacitance 92.

[0091] Next, the control unit 7a operates the DCDC converter 4 and controls the voltage of the second capacitance 92 of the DCDC converter 4 so that it is higher than the voltage of the second DC power supply 3. Specifically, the control unit 7a instructs the DCDC converter 4 to perform a step-down operation, so that the voltage of the first DC power supply 2 is stepped down by the DCDC converter 4, and the voltage of the second capacitance 92 is controlled so that it is higher than the voltage of the second DC power supply 3. At this time, by setting the second capacitance 92 as the controlled object of power conversion, the voltage of the second capacitance 92 can be controlled to an arbitrary voltage higher than zero by the existing DCDC converter 4.

[0092] Next, the diagnostic unit 8 measures the potential difference between both ends of the second switch 6b. If the potential difference between both ends of the second switch 6b measured by the diagnostic unit 8 is equal to or less than a reference value, it can be confirmed that the second switch 6b has not been able to disconnect the second DC power supply 3 and the DCDC converter 4 in a state where it is unable to properly respond to instructions from the control unit 7a. On the other hand, if the potential difference between both ends of the second switch 6b measured by the diagnostic unit 8 is greater than the reference value, it can be confirmed that the second switch 6b has been able to disconnect the second DC power supply 3 and the DCDC converter 4 in a state where it is able to properly respond to instructions from the control unit 7a. This makes it possible to determine whether the second switch 6b has been able to properly disconnect the second DC power supply 3 and the DCDC converter 4.

[0093] 5 according to the fourth modification, is configured with a single MOSFET, and therefore generally, even when the second switch 6a is controlled to be in an off state, the body diode does not provide the ability to cut off current flowing from the DCDC converter 4 to the second DC power supply 3, and therefore the second switch 6a only cuts off current flowing from the second DC power supply 3 to the DCDC converter 4. In contrast, when the second switch 6b according to the present modification shown in FIG. 6 has the ability to cut off current flowing from the DCDC converter 4 to the second DC power supply 3, the method of this modification can diagnose the cutting performance in the direction from the DCDC converter 4 to the second DC power supply 3.

[0094] [Specific Configuration of DC-DC Converter 4] The internal circuit of the DC-DC converter 4 in the embodiment has, for example, the following specific configuration and operates as follows.

[0095] 7 is a diagram illustrating a circuit of a DC-DC converter 4c according to a first specific example of the DC-DC converter 4 of the embodiment. Here, the diagram illustrates the overall configuration of a power supply device 1f including the DC-DC converter 4c.

[0096] The DC-DC converter 4 c includes a first switching element 411 , a second switching element 412 , a reactor 413 , a current sensor 42 , a first capacitance 91 , and a second capacitance 92 .

[0097] 7, in the DC-DC converter 4c, a first switching element 411 and a reactor 413 are connected in series at a junction J4c in order from the first switch 5 side to the second switch 6 side. One end of the second switching element 412 is connected to the junction J4c of the first switching element 411 and the reactor 413, and the other end is connected to ground.

[0098] The first switching element 411 and the second switching element 412 are both N-channel MOSFETs and each have a body diode. The anode of the body diode is connected to the source electrode side of the first switching element 411 and the second switching element 412, and the cathode is connected to the drain electrode side of the body diode.

[0099] Next, the operation of the DC-DC converter 4c will be described.

[0100] In the power supply device 1f, when charging is performed from the first DC power supply 2 to the second DC power supply 3, the DCDC converter 4c performs a step-down operation.

[0101] The first switching element 411 and the second switching element 412 perform switching operations in accordance with control by the control unit 7, the DC voltage of the first DC power supply 2 is stepped down, and the second DC power supply 3 is charged. Specifically, as an example, the first switching element 411 is turned on and the second switching element 412 is turned off, causing a current to flow from the first DC power supply 2 to the second DC power supply 3 via the first switching element 411 and the reactor 413, thereby storing energy in the reactor 413. Furthermore, the first switching element 411 is turned off and the second switching element 412 is turned on, releasing the energy stored in the reactor 413 and causing a current to flow from the ground to the second DC power supply 3 via the second switching element 412 and the reactor 413. The state in which energy is stored in the reactor 413 and the state in which a current flows from the ground to the second DC power supply 3 via the second switching element 412 and the reactor 413 are alternately repeated.

[0102] In the switching operation of the first switching element 411 and the second switching element 412, the control unit 7 feeds back the voltage of the second DC power supply 3 to the control unit 7, and then, for example, in the case of a drive signal using pulse width modulation (PWM), the on-duty of the drive signal is determined to control the output from the DCDC converter 4c.

[0103] The control unit 7 may determine the on-duty of the drive signals to the first switching element 411 and the second switching element 412 based on the difference between the target current value and the current value detected by the current sensor 42.

[0104] In the power supply device 1f, when charging is performed from the second DC power supply 3 to the first DC power supply 2, the DCDC converter 4c performs a step-up operation.

[0105] The first switching element 411 and the second switching element 412 perform switching operations in accordance with control by the control unit 7, the DC voltage of the second DC power supply 3 is boosted, and the first DC power supply 2 is charged. Specifically, as an example, the first switching element 411 is turned off and the second switching element 412 is turned on, causing a current to flow from the second DC power supply 3 to ground via the reactor 413 and the second switching element 412, and thereby energy is stored in the reactor 413. Furthermore, the first switching element 411 is turned on and the second switching element 412 is turned off, and the energy stored in the reactor 413 is released, causing a current to flow from the second DC power supply 3 to the first DC power supply 2 via the reactor 413 and the first switching element 411. The state in which energy is stored in the reactor 413 and the state in which current flows from the second DC power supply 3 to the first DC power supply 2 via the reactor 413 and the first switching element 411 are alternately repeated.

[0106] In the switching operation of the first switching element 411 and the second switching element 412, the control unit 7 feeds back the voltage of the first DC power supply 2 to the control unit 7, and then, in the case of a drive signal using pulse width modulation (PWM), for example, the on-duty of the drive signal is determined to control the output from the DCDC converter 4c.

[0107] The control unit 7 may determine the on-duty of the drive signals to the first switching element 411 and the second switching element 412 based on the difference between the target current value and the current value detected by the current sensor 42.

[0108] 8 is a diagram illustrating a circuit of a DC-DC converter 4d according to a second specific example of the DC-DC converter 4 of the embodiment. Here, the diagram illustrates the overall configuration of a power supply device 1g including the DC-DC converter 4d.

[0109] The DC-DC converter 4d includes a first switching element 411, a second switching element 412, a reactor 413, a third switching element 414, a fourth switching element 415, a current sensor 42, a first capacitance 91, and a second capacitance 92. The DC-DC converter 4d has a configuration in which the third switching element 414 and the fourth switching element 415 are added to the DC-DC converter 4c according to specific example 1. The following description will focus on the differences from the DC-DC converter 4c according to specific example 1.

[0110] 8, in the DC-DC converter 4d, a first switching element 411, a reactor 413, and a third switching element 414 are connected in series at a node J4d in this order from the first switch 5 side to the second switch 6 side. One end of a fourth switching element 415 is connected to the node J4d between the third switching element 414 and the reactor 413, and the other end is connected to ground.

[0111] The third switching element 414 and the fourth switching element 415 are both N-channel MOSFETs and each have a body diode. The body diode has an anode connected to the source electrode side of the third switching element 414 and the fourth switching element 415 and a cathode connected to the drain electrode side of the third switching element 414 and the fourth switching element 415.

[0112] Next, the operation of the DC-DC converter 4d will be described.

[0113] In the power supply device 1g, when charging the second DC power supply 3 from the first DC power supply 2, the DCDC converter 4d can perform not only a step-down operation but also a step-up operation according to instructions from the control unit 7.

[0114] When performing a step-down operation, the third switching element 414 is kept on and the fourth switching element 415 is kept off, and the DC-DC converter 4c according to the first specific example operates in the same manner as the DC-DC converter 4c according to the first specific example.

[0115] On the other hand, when a boost operation is performed, the first switching element 411 is kept on and the second switching element 412 is kept off, and the third switching element 414 and the fourth switching element 415 perform switching operations in accordance with control by the control unit 7, so that the DC voltage of the first DC power supply 2 is boosted and the second DC power supply 3 is charged. Specifically, as an example, the first switching element 411 is kept on and the second switching element 412 is kept off, and the third switching element 414 is turned off and the fourth switching element 415 is turned on, so that a current flows from the first DC power supply 2 to the ground via the first switching element 411, the reactor 413, and the fourth switching element 415, and energy is thereby stored in the reactor 413. Furthermore, with the first switching element 411 maintained on and the second switching element 412 maintained off, the third switching element 414 is turned on and the fourth switching element 415 is turned off, and the energy stored in the reactor 413 is released, causing a current to flow from the first DC power supply 2 to the second DC power supply 3 via the first switching element 411, the reactor 413, and the third switching element 414. The state in which energy is stored in the reactor 413 and the state in which a current flows from the first DC power supply 2 to the second DC power supply 3 via the first switching element 411, the reactor 413, and the third switching element 414 are alternately repeated.

[0116] According to the power supply device 1g of specific example 2, similarly to the embodiment, when it is desired to diagnose the breaking performance of the first switch 5, the control unit 7 issues a breaking instruction to the first switch 5 and a connecting instruction to the second switch 6, and then the DCDC converter 4d performs a voltage conversion operation and discharges the charge of the first capacitance 91 to the second DC power supply 3. Therefore, it is possible to provide a power supply device 1 that can diagnose the breaking performance of the first switch 5 in a short time.

[0117] In the switching operation of the third switching element 414 and the fourth switching element 415, the control unit 7 feeds back the voltage of the second DC power supply 3 to the control unit 7, and then, for example, in the case of a drive signal using pulse width modulation (PWM), the on-duty of the drive signal is determined to control the output from the DCDC converter 4d.

[0118] The control unit 7 may determine the on-duty of the drive signals to the third switching element 414 and the fourth switching element 415 based on the difference between the target current value and the current value detected by the current sensor 42.

[0119] Furthermore, in the power supply device 1g, when charging the first DC power supply 2 from the second DC power supply 3, the DCDC converter 4d can perform not only a step-up operation but also a step-down operation in accordance with instructions from the control unit 7.

[0120] When performing a boost operation, the third switching element 414 is kept on and the fourth switching element 415 is kept off, and the DC-DC converter 4c according to the first specific example operates in the same manner as the DC-DC converter 4c according to the first specific example.

[0121] On the other hand, when a step-down operation is performed, the first switching element 411 is kept on and the second switching element 412 is kept off, and the third switching element 414 and the fourth switching element 415 perform switching operations in accordance with control by the control unit 7, so that the DC voltage of the second DC power supply 3 is stepped down to charge the first DC power supply 2. Specifically, as an example, the first switching element 411 is kept on and the second switching element 412 is kept off, and the third switching element 414 is turned on and the fourth switching element 415 is turned off, so that a current flows from the second DC power supply 3 to the first DC power supply 2 via the third switching element 414, the reactor 413, and the first switching element 411, and energy is thereby stored in the reactor 413. Furthermore, with the first switching element 411 maintained on and the second switching element 412 maintained off, the third switching element 414 is turned off and the fourth switching element 415 is turned on, and the energy stored in the reactor 413 is released, causing a current to flow from the ground to the first DC power supply 2 via the fourth switching element 415, the reactor 413, and the first switching element 411. The state in which energy is stored in the reactor 413 and the state in which a current flows from the ground to the first DC power supply 2 via the fourth switching element 415, the reactor 413, and the first switching element 411 are alternately repeated.

[0122] According to the power supply device 1g of specific example 2, similarly to the embodiment, when it is desired to diagnose the breaking performance of the second switch 6, the control unit 7 issues a breaking instruction to the second switch 6 and a connecting instruction to the first switch 5, and then the DCDC converter 4d performs a voltage conversion operation and discharges the charge of the second capacitance 92 to the first DC power supply 2. Therefore, it is possible to provide a power supply device 1 that can diagnose the breaking performance of the second switch 6 in a short time.

[0123] In the switching operation of the third switching element 414 and the fourth switching element 415, the control unit 7 feeds back the voltage of the first DC power supply 2 to the control unit 7, and then, for example, in the case of a drive signal using pulse width modulation (PWM), the on-duty of the drive signal is determined to control the output from the DCDC converter 4d.

[0124] The control unit 7 may determine the on-duty of the drive signals to the third switching element 414 and the fourth switching element 415 based on the difference between the target current value and the current value detected by the current sensor 42.

[0125] 9 is a diagram illustrating a circuit of a DC-DC converter 4e according to a third specific example of the embodiment. Here, the diagram illustrates the overall configuration of a power supply device 1h including a DC-DC converter 4e.

[0126] The DC-DC converter 4 e includes a fifth switching element 416 , a transformer 417 , a diode 418 , a current sensor 42 , a first capacitance 91 , and a second capacitance 92 .

[0127] 9 , in the DC-DC converter 4e, the primary winding of the transformer 417 and the fifth switching element 416 are connected in series from the first switch 5 side. The fifth switching element 416 is an N-channel MOSFET with a source electrode grounded and a drain electrode connected to the primary winding of the transformer 417, and has a body diode. The anode of the body diode is connected to the source electrode side of the fifth switching element 416, and the cathode is connected to the drain electrode side.

[0128] One end of the secondary winding of the transformer 417 is grounded, and the other end is connected to the anode of the diode 418. The cathode of the diode 418 is connected to the second switch 6.

[0129] Next, the operation of the DC-DC converter 4e will be described.

[0130] The DCDC converter 4e charges the second DC power supply 3 from the first DC power supply 2. In the power supply device 1h, when charging the second DC power supply 3 from the first DC power supply 2, the DCDC converter 4e performs a step-up / step-down operation in accordance with instructions from the control unit 7. Whether the operation is step-up or step-down at this time is determined by the winding ratio of the transformer 417 and the on-duty of the control signal from the control unit 7 to the fifth switching element 416, etc.

[0131] When charging the second DC power supply 3 from the first DC power supply 2, the fifth switching element 416 performs switching operation in accordance with control by the control unit 7, and the DC voltage of the first DC power supply 2 is increased or decreased to charge the second DC power supply 3. Specifically, as an example, current flows intermittently through the primary winding of the transformer 417 due to switching of the fifth switching element 416, generating an AC voltage in the secondary winding of the transformer 417. The AC voltage is half-wave rectified by the diode 418 and smoothed by the second capacitance 92 to become a DC voltage, which is output to the second DC power supply 3.

[0132] According to the power supply device 1h of specific example 3, similarly to the embodiment, when it is desired to diagnose the breaking performance of the first switch 5, the control unit 7 issues a breaking instruction to the first switch 5 and a connecting instruction to the second switch 6, and then the DCDC converter 4e performs a voltage conversion operation and discharges the charge of the first capacitance 91 to the second DC power supply 3. Therefore, it is possible to provide a power supply device 1 that can diagnose the breaking performance of the first switch 5 in a short time.

[0133] In the switching operation of the fifth switching element 416, the control unit 7 feeds back the voltage of the second DC power supply 3 to the control unit 7, and then, for example, in the case of a drive signal using pulse width modulation (PWM), the on-duty is determined and the output from the DCDC converter 4e is controlled.

[0134] The control unit 7 may determine the on-duty of the drive signal to the fifth switching element 416 based on the difference between the current value detected by the current sensor 42 and a target current value.

[0135] As described above, the power supply device 1 according to the present embodiment, modifications, and specific examples is a power supply device connected between the first DC power supply 2 that supplies and maintains a first voltage and the second DC power supply 3 that supplies and maintains a second voltage, and has a first switch 5 one end of which is connected to the first DC power supply 2 and a first capacitance 91 connected to the other end of the first switch 5, and performs a first operation of converting a voltage stored in the first capacitance 91 into a second voltage and outputting the converted second voltage to the second DC power supply 3, and a second operation of converting a voltage stored in the first capacitance 91 into a second voltage and outputting the converted second voltage to the second DC power supply 3. The device comprises a DC-DC converter 4 that performs at least one of a second operation of converting a second voltage into a third voltage and outputting the converted third voltage to a first capacitance 91, and a control unit 7 that controls the DC-DC converter 4 and a first switch 5 and detects a potential difference across the first switch 5, wherein the control unit 7 instructs the first switch 5 to be turned off, causes the DC-DC converter 4 to perform the first operation or the second operation, and then detects the potential difference, and determines that the first switch 5 is normal when the detected potential difference is greater than a first reference potential difference.

[0136] As a result, in diagnosing the first switch 5, the first operation or the second operation is performed on the DCDC converter 4 after the first switch 5 is turned off, so if the breaking capability of the first switch 5 is normal, the potential difference between both ends of the first switch 5 increases in a shorter time than before. This makes it possible to realize a power supply device that can quickly diagnose the breaking capability of a switch provided between the input side or output side and the DCDC converter included in the power supply device.

[0137] Here, the DC-DC converter 4 may perform a step-down operation or a step-up operation as the first operation or the second operation, thereby realizing a power supply device that performs power conversion between the first DC power supply 2 and the second DC power supply 3 having various voltages.

[0138] Furthermore, the DC-DC converter 4 may include a current sensor 42 that detects a current flowing through the DC-DC converter 4. This allows the DC-DC converter 4 to perform at least one of the first operation and the second operation by control based on the current detected by the current sensor 42.

[0139] For example, when the current detected by the current sensor 42 is equal to or greater than a specified value, the DC-DC converter 4 determines that an abnormality has occurred and can stop at least one of the first operation and the second operation.

[0140] Furthermore, the DC-DC converter 4 may charge the first capacitance 91 to an arbitrary third voltage through the first operation or the second operation while the first switch 5 is cut off. This prevents the potential difference between both ends of the first switch 5 from becoming too large during the diagnosis of the first switch 5, and shortens the time required to restore the voltage of the first capacitance 91 at the end of the diagnosis.

[0141] Furthermore, after interrupting the first switch 5, the control unit 7 may cause the DCDC converter 4 to perform a first operation, thereby decreasing the voltage of the first capacitance 91 to be smaller than the first voltage. This not only enables the first switch 5 to be diagnosed for its interruption capability in a shorter time than before, but also enables the first switch 5 to be diagnosed for its interruption capability with respect to a current flowing in a direction from the terminal connected to the first DC power supply 2 to the terminal connected to the first capacitance 91.

[0142] Furthermore, after interrupting the first switch 5, the control unit 7 may cause the DC-DC converter 4 to perform a second operation, thereby increasing the voltage of the first capacitance 91 to be higher than the first voltage. This not only enables the first switch 5 to be diagnosed for its interruption capability in a shorter time than before, but also enables the first switch 5 to be diagnosed for its interruption capability with respect to a current flowing in a direction from the terminal connected to the first capacitance 91 to the terminal connected to the first DC power supply 2.

[0143] The power supply device 1 further includes a second switch 6 having one end connected to the second DC power source 3, and the DC-DC converter 4 further includes a second capacitance 92 connected to the other end of the second switch 6. The control unit 7 may further turn off the second switch 6, cause the DC-DC converter 4 to perform a first operation or a second operation, and then detect a potential difference across the second switch 6, and determine that the second switch 6 is normal when the detected potential difference is greater than a second reference potential difference.

[0144] This allows not only the first switch 5 to be diagnosed, but also the second switch 6 to be diagnosed in the same manner as the first switch 5 .

[0145] Furthermore, the switch diagnostic methods according to the present embodiment, the modified examples, and the specific example are methods for diagnosing a first switch 5 included in a power supply device 1 connected between 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, the first switch 5 having one end connected to the first DC power supply 2, and the power supply device 1 including a DCDC converter 4 having a first capacitance 91 connected to the other end of the first switch 5, which converts a voltage stored in the first capacitance 91 into a second voltage and outputs the converted second voltage to the second DC power supply 3. The diagnostic method includes a DCDC converter 4 that performs at least one of a first operation, a second operation, and a third operation, in which a second voltage supplied and held by a second DC power source 3 is converted into a third voltage and the converted third voltage is output to a first capacitance 91. The diagnostic method includes disconnecting both ends of a first switch 5 (S10), causing the DCDC converter 4 to perform the first operation or the second operation (S12), detecting a potential difference across the first switch 5 (S13), and when the detected potential difference is greater than a first reference potential difference (No in S14), determining that the first switch 5 is normal (S16).

[0146] As a result, in diagnosing the first switch 5, the first operation or the second operation is performed on the DCDC converter 4 after the first switch 5 is turned off, so if the breaking capability of the first switch 5 is normal, the potential difference between both ends of the first switch 5 increases in a shorter time than in the past. Thus, a switch diagnostic method is realized that can quickly diagnose the breaking capability of a switch provided between the input side or output side and the DCDC converter provided in the power supply device.

[0147] While the power supply device and switch diagnostic method according to the present disclosure have been described above based on the embodiments, modifications, and specific examples, the present disclosure is not limited to these embodiments, modifications, and specific examples. As long as they do not deviate from the gist of the present disclosure, various modifications that a person skilled in the art would conceive of, such as modifications to the present embodiments, modifications, and specific examples, and other forms constructed by combining some of the components of the embodiments, modifications, and specific examples, are also included within the scope of the present disclosure.

[0148] The power supply device according to the present disclosure can be widely used as a power supply device connected between two DC power sources to perform voltage conversion, and more specifically as a power supply device that can quickly diagnose the interruption performance of a switch provided between the input side or output side and a DCDC converter provided in the power supply device, for example, in an on-board power conversion device that converts power between a battery and a capacitor.

[0149] REFERENCE SIGNS LIST 1, 1a to 1h Power supply device 2 First DC power supply 3 Second DC power supply 4, 4a to 4e DCDC converter 41 Power conversion circuit 411 First switching element 412 Second switching element 413 Reactor 414 Third switching element 415 Fourth switching element 416 Fifth switching element 417 Transformer 418 Diode 42 Current sensor 5, 5a, 5b First switch 51 First voltage detection unit 52 Second voltage detection unit 53 Fifth voltage detection unit 6, 6a, 6b Second switch 61 Third voltage detection unit 62 Fourth voltage detection unit 63 Sixth voltage detection unit 7, 7a Control unit 8 Diagnosis unit 91 First capacitance 92 Second capacitance 100 Vehicle

Claims

1. A power supply device configured to be connected between 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, A first switch having one end connected to the first DC power source; a DC-DC converter having a first capacitance connected to the other end of the first switch; a control unit configured to control the DC-DC converter and the first switch and to detect a potential difference between the one end and the other end of the first switch; Equipped with The DC-DC converter comprises: a first operation of converting a voltage stored in the first capacitance to the second voltage and outputting the converted second voltage to the second DC power supply; a second operation of converting the second voltage supplied and held by the second DC power supply into a third voltage and outputting the converted third voltage to the first capacitance; and The control unit is detecting the potential difference after instructing the first switch to be turned off and causing the DC-DC converter to perform the first operation or the second operation; determining that the first switch is normal when the detected potential difference is greater than a first reference potential difference; It is configured as follows: power supply.

2. The control unit is configured to determine that the first switch is abnormal when the detected potential difference is not larger than the first reference potential difference.

2. The power supply device of claim 1.

3. The DC-DC converter is configured to perform a step-down operation as the first operation or the second operation.

2. The power supply device of claim 1.

4. The DC-DC converter is configured to perform a boost operation as the first operation or the second operation.

2. The power supply device of claim 1.

5. the DC-DC converter having a current sensor configured to detect a current through the DC-DC converter; 2. The power supply device of claim 1.

6. The DC-DC converter is configured to perform at least one of the first operation and the second operation by control based on a current detected by the current sensor.

6. The power supply device according to claim 5.

7. The DC-DC converter is configured to stop at least one of the first operation and the second operation when the current detected by the current sensor is equal to or greater than a specified value.

7. The power supply device of claim 6.

8. The DC-DC converter is configured to charge the first capacitance to any one of the third voltages by the first operation or the second operation when the first switch is cut off.

2. The power supply device of claim 1.

9. The control unit is configured to cause the DC-DC converter to perform the first operation after instructing the first switch to be turned off, thereby decreasing the voltage of the first capacitance so that the voltage of the first capacitance becomes smaller than the first voltage.

2. The power supply device of claim 1.

10. The control unit is configured to increase the voltage of the first capacitance so that the voltage of the first capacitance becomes larger than the first voltage by causing the DC-DC converter to perform the second operation after instructing the first switch to be turned off.

2. The power supply device of claim 1.

11. A second switch having one end connected to the second DC power source, the DC-DC converter further includes a second capacitance connected to the other end of the second switch; The control unit is Instructing the second switch to be cut off and causing the DCDC converter to perform the first operation or the second operation, and then detecting a potential difference between both ends of the second switch; When the detected potential difference is greater than a second reference potential difference, the second switch is determined to be normal. It is configured as follows:

11. The power supply device according to claim 1.

12. 1. A method for diagnosing a power supply device connected between 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, comprising: a switch having one end connected to the first DC power source; A DC-DC converter having a first capacitance connected to the other end of the switch, a first operation of converting a voltage stored in the first capacitance into the second voltage and outputting the converted second voltage to the second DC power supply; a second operation of converting the second voltage supplied and held by the second DC power supply into a third voltage and outputting the converted third voltage to the first capacitance; A DC-DC converter configured to perform at least one of the above. providing a power supply device comprising: detecting a potential difference between the one end and the other end of the switch after instructing the switch to be turned off and causing the DC-DC converter to perform the first operation or the second operation; determining that the switch is normal when the detected potential difference is greater than a reference potential difference; A diagnostic method comprising:

13. The method further includes determining that the switch is abnormal when the detected potential difference is not greater than the reference potential difference. The diagnostic method according to claim 12.