Control device and control method

Abstract

To suppress an overcurrent of a system mounting a DC-DC converter.SOLUTION: A control device comprises: a converter provided between a first power supply and a second power supply and that includes at least one high-side switch element whose drain terminal is electrically connected with a power supply line and at least one low-side switch element whose drain terminal is electrically connected with a source terminal of the high-side switch element and whose source terminal is electrically connected with a ground line; a first isolating switch whose one end is electrically connected with a positive electrode of the first power supply and whose the other end is electrically connected with the drain terminal of the high-side switch element; a second isolating switch whose one end is electrically connected with a positive electrode of the second power supply and whose the other end is electrically connected with the drain terminal of the high-side switch element; a midpoint voltage detector that detects a midpoint voltage between the high-side switch element and the low-side switch element; and a controller that turns off the first and second isolating switches when the midpoint voltage detector detects the midpoint voltage.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a control device and a control method.

Background Art

[0002] As a power supply device for a vehicle, even when an abnormality occurs on the higher voltage side than a predetermined position of the power supply device, a technique for supplying power based on a power storage unit on the lower voltage side to a path on the lower voltage side is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A non-insulated DC-DC converter is mounted on a system such as a vehicle in a state where two power supplies such as a battery and an accumulator are connected. If the main switch section of the DC-DC converter fails, an overcurrent may occur even before operation and the fuse may blow.

[0005] An object of the present disclosure is to provide a control device and a control method capable of suppressing an overcurrent in a system equipped with a DC-DC converter in advance or before the operation of the DC-DC converter.

Means for Solving the Problems

[0006] The control device according to the present disclosure includes, between a first power supply and a second power supply, a high-side switch element provided with its drain terminal electrically connected to a power line, and a low-side switch element provided with its drain terminal electrically connected to the source terminal of the high-side switch element and its source terminal electrically connected to a ground line, a converter including at least one of each, a first cutoff switch unit having one end electrically connected to the positive electrode of the first power supply and the other end electrically connected to the drain terminal of the high-side switch element, a second cutoff switch unit having one end electrically connected to the positive electrode of the second power supply and the other end electrically connected to the drain terminal of the high-side switch element, a midpoint voltage detection unit that detects a midpoint voltage between the high-side switch element and the low-side switch element, and a control unit that controls the states of the first cutoff switch unit and the second cutoff switch unit to an off state when the midpoint voltage detection unit detects the midpoint voltage.

[0007] In the control device according to the present disclosure, the control unit determines a failure of at least one of the high-side switch element and the low-side switch element based on a detection result of the midpoint voltage by the midpoint voltage detection unit.

[0008] In the control device according to the present disclosure, an auxiliary power supply for applying an auxiliary voltage to the drain of the high-side switch element is provided, and the control unit determines a failure of at least one of the high-side switch element and the low-side switch element based on a detection result of the midpoint voltage by the midpoint voltage detection unit in a state where the auxiliary voltage is applied to the drain terminal of the high-side switch element.

[0009] In the control device according to the present disclosure, each of the first cutoff switch unit and the second cutoff switch unit includes at least one semiconductor element.

[0010] The control method according to the present disclosure is provided between a first power supply and a second power supply, and includes at least one high-side switch element having a drain terminal electrically connected to a power line, and a low-side switch element having a drain terminal electrically connected to a source terminal of the high-side switch element and a source terminal electrically connected to a ground line. In a converter including at least one of each, a step of detecting a midpoint voltage between the high-side switch element and the low-side switch element, and when detecting the midpoint voltage, a first cutoff switch unit having one end electrically connected to a positive electrode of the first power supply and the other end electrically connected to the drain terminal of the high-side switch element, and a second cutoff switch unit having one end electrically connected to a positive electrode of the second power supply and the other end electrically connected to the drain terminal of the high-side switch element are controlled to be in an off state.

Effects of the Invention

[0011] According to the present disclosure, overcurrent in a system equipped with a DC-DC converter can be suppressed in advance or before the operation of the DC-DC converter.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. Note that the present disclosure is not limited by this embodiment, and in the following embodiments, the same parts are denoted by the same reference numerals to omit redundant explanations.

[0014] [First Embodiment] FIG. 1 is a diagram showing a configuration example of the power supply system according to the first embodiment. The power supply system 100 includes a first power supply 1, a second power supply 2, a fuse 3, a fuse 4, and a control device 10.

[0015] The first power supply 1 is a power supply device that supplies power to the control device 10. The voltage of the first power supply 1 is, for example, 24V or 48V, but is not limited thereto. The first power supply 1 outputs a voltage to a power source such as a motor (not shown), for example.

[0016] The second power supply 2 is a power supply device that supplies power to the control device 10. The second power supply 2 is a power supply device that outputs a lower voltage than the first power supply 1. The voltage of the second power supply 2 is, for example, 12V, which is exemplified but not limited thereto. The second power supply 2 may be, for example, a capacitor. The second power supply 2 outputs a voltage to in-vehicle devices such as wipers.

[0017] One end of the fuse 3 is electrically connected to the positive electrode of the first power supply 1, and the other end is electrically connected to the current detection unit 11 of the control device 10. The fuse 3 is provided to protect the first power supply 1. The fuse 3 is a current fuse that melts due to self-heating when the passing current exceeds the rated current. When an excessive current exceeding the rated current flows from the control device 10, the fuse 3 melts to prevent the excessive current from flowing into the first power supply 1 and various devices connected to the first power supply 1.

[0018] One end of the fuse 4 is electrically connected to the positive electrode of the second power supply 2, and the other end is electrically connected to the current detection unit 17 of the control device 10. The fuse 4 is provided to protect the second power supply 2. The fuse 4 is a current fuse that melts due to self-heating when the passing current exceeds the rated current. When an excessive current exceeding the rated current flows from the control device 10, the fuse 4 melts to prevent the excessive current from flowing into the second power supply 2.

[0019] The control device 10 includes a current detection unit 11, a cutoff switch unit 12, an overcurrent detection unit 13, a voltage detection unit 14, a voltage detection unit 15, an output capacitor 16, a current detection unit 17, a cutoff switch unit 18, an overcurrent detection unit 19, a voltage detection unit 20, a voltage detection unit 21, an output capacitor 22, a converter 23, a switching element diagnosis unit 24, a midpoint voltage detection unit 25, and a control unit 26.

[0020] The current detection unit 11 has one end electrically connected to the fuse 3 and the other end electrically connected to the cutoff switch unit 12. The current detection unit 11 detects the output current output from the converter 23. The current detection unit 11 outputs a current detection signal corresponding to the detection result to the overcurrent detection unit 13. The current detection unit 11 is, for example, a well-known current sensor, but is not limited thereto.

[0021] The cutoff switch unit 12 has one end electrically connected to the current detection unit 11 and the other end connected to the converter 23. The cutoff switch unit 12 is configured to cut off the electrical connection between the first power supply 1 and the converter 23. The cutoff switch unit 12 is also called the first cutoff switch unit.

[0022] FIG. 2 is a diagram showing a configuration example of the cutoff switch unit. In FIG. 2, the fuse 3 and the current detection unit 11 are omitted. As shown in FIG. 2, the cutoff switch unit 12 includes a switching element Q11. The switching element Q11 is a transistor such as a MOSFET (Metal - Oxide - Semiconductor Field Effect Transistor). That is, the cutoff switch unit 12 is composed of semiconductor elements. When the switching element Q11 is in the off state, it electrically cuts off the connection between the first power supply 1 and the converter 23. When a control signal is input to the gate of the switching element Q11, it switches to the on state and electrically connects the first power supply 1 and the converter 23. The switching element Q11 may be a silicon power device, a GaN power device, a SiC power device, an IGBT (Insulated Gate Bipolar Transistor), etc.

[0023] Note that the configuration of the cutoff switch unit 12 is not limited to the configuration example shown in FIG. 2. FIGS. 3, 4, and 5 are diagrams showing configuration examples of modified examples of the cutoff switch unit.

[0024] As shown in FIG. 3, the cutoff switch unit 12A may include a switching element Q11 and a switching element Q12. For example, the drain terminal of the switching element Q11 is electrically connected to the first power supply 1, and the source terminal is electrically connected to the source terminal of the switching element Q12. For example, the source terminal of the switching element Q12 may be electrically connected to the source terminal of the switching element Q11, and the drain terminal may be electrically connected to the converter 23. In the example shown in FIG. 3, a common control signal is input to the gate terminal of the switching element Q11 and the gate terminal of the switching element Q12, respectively.

[0025] As shown in FIG. 4, the cutoff switch unit 12B may include a switching element Q11 and a switching element Q12. The cutoff switch unit 12B is different from the cutoff switch unit 12A shown in FIG. 3 in that different control signals are input to the source terminal of the switching element Q11 and the gate terminal of the switching element Q12, respectively.

[0026] As shown in FIG. 5, the cutoff switch unit 12C may include a relay RY. The cutoff switch unit 12C may be mechanically configured. In this case, the relay RY electrically disconnects or electrically connects between the first power supply 1 and the converter 23 by mechanical operation.

[0027] Returning to FIG. 1. The overcurrent detection unit 13 detects an overcurrent based on the current detection signal received from the current detection unit 11. The overcurrent detection unit 13 detects an overcurrent, for example, in accordance with an overcurrent diagnosis signal from the control unit 26. When the overcurrent detection unit 13 detects an overcurrent, for example, it outputs a control signal to the overcurrent stop circuit unit 32.

[0028] The voltage detection unit 14 detects the voltage between the cutoff switch unit 12 and the converter 23. The voltage detection unit 14 outputs the detection result of the voltage between the cutoff switch unit 12 and the converter 23 to the control unit 26. The voltage detection unit 14 is also called the first voltage detection unit.

[0029] The voltage detection unit 15 detects the voltage between the fuse 3 and the current detection unit 11. The voltage detection unit 15 outputs the detection result of the voltage between the fuse 3 and the current detection unit 11 to the control unit 26. The voltage detection unit 15 is also called the second voltage detection unit.

[0030] The output capacitor 16 smoothes the voltage from the converter 23. The voltage of the output capacitor 16 becomes the voltage output to the first power supply 1 side.

[0031] One end of the current detection unit 17 is electrically connected to the fuse 4, and the other end is electrically connected to the cutoff switch unit 18. The current detection unit 17 detects the output current output from the converter 23. The current detection unit 17 outputs a current detection signal corresponding to the detection result to the overcurrent detection unit 19. The current detection unit 17 is, for example, a well-known current sensor, but is not limited thereto.

[0032] One end of the cutoff switch unit 18 is electrically connected to the current detection unit 17, and the other end is connected to the converter 23. The cutoff switch unit 18 is configured to cut off the electrical connection between the second power supply 2 and the converter 23. The cutoff switch unit 18 can be configured in the same manner as the cutoff switch unit 12 shown in FIGS. 2 to 5. The cutoff switch unit 18 is also called the second cutoff switch unit.

[0033] The overcurrent detection unit 19 detects an overcurrent based on the current detection signal received from the current detection unit 17. The overcurrent detection unit 19 detects an overcurrent, for example, according to the overcurrent diagnosis signal from the control unit 26. When the overcurrent detection unit 19 detects an overcurrent, for example, it outputs a control signal to the overcurrent stop circuit unit 32.

[0034] The voltage detection unit 20 detects the voltage between the cutoff switch unit 18 and the converter 23. The voltage detection unit 20 outputs the detection result of the voltage between the cutoff switch unit 18 and the converter 23 to the control unit 26. The voltage detection unit 20 is also called the third voltage detection unit.

[0035] The voltage detection unit 21 detects the voltage between the fuse 4 and the current detection unit 17. The voltage detection unit 21 outputs the detection result of the voltage between the fuse 4 and the current detection unit 17 to the control unit 26. The voltage detection unit 21 is also called the fourth voltage detection unit.

[0036] The output capacitor 22 smoothes the voltage from the converter 23. The voltage of the output capacitor 22 becomes the voltage output to the second power supply 2 side.

[0037] The converter 23 is a bidirectional DC-DC converter. The converter 23 includes, on the high side, a switching element Q1, a switching element Q3, ···, a switching element Qp (p is an arbitrary odd number). The converter 23 includes, on the low side, a switching element Q2, a switching element Q4, ···, a switching element Qn (n is an arbitrary even number). The converter 23 includes the same number of switching elements on the high side and the low side, respectively. The converter 23 only needs to include at least the switching element Q1 on the high side and the switching element Q2 on the low side.

[0038] The drain terminals of the switching elements Q1, Q3, ···, Qp on the high side are electrically connected to the high potential (the power line of the first power supply 1), respectively. The drain terminals of the switching elements Q1, Q3, ···, Qp on the high side are electrically connected to the cutoff switch unit 12, respectively. The source terminals of the switching elements Q1, Q3, ···, Qp on the high side are electrically connected to the drain terminals of the switching elements Q2, Q4, ···, Qn on the low side, respectively.

[0039] The source terminals of the switching elements Q2, Q4, ···, Qn on the low side are electrically connected to the low potential (ground line), respectively.

[0040] Converter 23 includes a capacitor C1, a capacitor C2, ···, and a capacitor Cm (m is an arbitrary integer).

[0041] One end of capacitor C1 is electrically connected to the drain terminal of switching element Q1, and the other end is electrically connected to the source terminal of switching element Q2. One end of capacitor C2 is electrically connected to the drain terminal of switching element Q3, and the other end is electrically connected to the source terminal of switching element Q4. One end of capacitor Cm is electrically connected to the drain terminal of switching element Qp, and the other end is electrically connected to the source terminal of switching element Qn. That is, in converter 23, capacitors are connected in parallel to the high-side switching element and the low-side switching element. Capacitors C1 to Cm suppress noise generated when each switching element performs a switching operation.

[0042] Converter 23 includes an inductor L1, an inductor L2, ···, and an inductor Lm.

[0043] One end of coil L1 is electrically connected between switching element Q1 and switching element Q2, and the other end is electrically connected to cutoff switch section 18. One end of coil L2 is electrically connected between switching element Q3 and switching element Q4, and the other end is electrically connected to cutoff switch section 18. One end of coil Lm is electrically connected between switching element Qp and switching element Qn, and the other end is electrically connected to cutoff switch section 18. That is, in converter 23, coils are electrically connected between each switching element on the high side and each switching element on the low side, and between cutoff switch section 18. In other words, each coil has one end electrically connected between the switching element on the high side and the switching element on the low side, and the other end electrically connected to cutoff switch section 18. That is, in converter 23, cutoff switch section 18 is electrically connected between each switching element on the high side and each switching element on the low side, respectively.

[0044] Switching element diagnosis section 24 outputs a signal for determining the failure of each switching element of converter 23. Switching element diagnosis section 24 outputs, for example, voltage Vc from an auxiliary power supply different from first power supply 1 and second power supply 2 as a signal for determining the failure of each switching element of converter 23. The auxiliary power supply is, for example, a power supply (not shown) that generates necessary power inside converter 23.

[0045] Midpoint voltage detection section 25 detects the midpoint voltage, which is the voltage between each switching element on the high side and each switching element on the low side. Midpoint voltage detection section 25 detects, for example, the midpoint voltage between switching element Q1 and switching element Q2.

[0046] Control section 26 includes cutoff switch drive section 30, cutoff switch drive section 31, overcurrent stop circuit section 32, switching element control section 33, and power supply control section 34.

[0047] The cutoff switch driving unit 30 switches between the on state and the off state of the cutoff switch unit 12. When measuring the midpoint voltage between the switching element on the high side and the switching element on the low side of the converter 23, for example, the cutoff switch driving unit 30 turns off the cutoff switch unit 12.

[0048] The cutoff switch driving unit 31 switches between the on state and the off state of the cutoff switch unit 18. When measuring the midpoint voltage between the switching element on the high side and the switching element on the low side of the converter 23, for example, the cutoff switch driving unit 31 turns off the cutoff switch unit 18.

[0049] When the overcurrent detection unit 13 or the overcurrent detection unit 19 detects an overcurrent, the overcurrent stop circuit unit 32 outputs a control signal for stopping each switching element of the converter 23.

[0050] The switching element control unit 33 controls each switching element of the converter 23. When the overcurrent detection unit 13 or the overcurrent detection unit 19 detects an overcurrent, for example, the switching element control unit 33 controls each switching element of the converter 23 according to the control signal from the overcurrent stop circuit unit 32. The switching element control unit 33 switches the target switching element of the converter 23 to the off state to determine a short - circuit fault of the target switching element. The switching element control unit 33 switches the target switching element of the converter 23 to the on state to determine an open - circuit fault of the target switching element.

[0051] The power supply control unit 34 controls each part of the control device 10. For example, the power supply control unit 34 outputs a control signal S1 to the overcurrent detection unit 13 to detect an overcurrent. For example, the power supply control unit 34 outputs a control signal S2 to the overcurrent detection unit 19 to detect an overcurrent. For example, the power supply control unit 34 outputs a control signal S3 to the cutoff switch driving unit 30 to control the cutoff switch unit 12. For example, the power supply control unit 34 outputs a control signal S4 to the cutoff switch driving unit 31 to control the cutoff switch unit 18. For example, the power supply control unit 34 outputs a control signal S5 to the switching element diagnosis unit 24 to execute a process of detecting the midpoint voltage between the switching element on the high side and the switching element on the low side of the converter 23. For example, the power supply control unit 34 outputs a control signal S6 to the switching element control unit 33 to control each switching element.

[0052] The power supply control unit 34 acquires the detection result of the voltage between the cutoff switch unit 12 and the converter 23 from the voltage detection unit 14. The power supply control unit 34 acquires the detection result of the voltage between the fuse 3 and the current detection unit 11 from the voltage detection unit 15. The power supply control unit 34 acquires the detection result of the voltage between the cutoff switch unit 18 and the converter 23 from the voltage detection unit 20. The power supply control unit 34 acquires the detection result of the voltage between the fuse 4 and the current detection unit 17 from the voltage detection unit 21. The power supply control unit 34 determines a short - circuit fault of the cutoff switch unit 12 and the cutoff switch unit 18 based on the detection results acquired from the voltage detection unit 14, the voltage detection unit 15, the voltage detection unit 20, and the voltage detection unit 21.

[0053] The power supply control unit 34 acquires the detection result of the midpoint voltage between the switching element on the high side and the low side of the converter 23 from the midpoint voltage detection unit 25. The power supply control unit 34 determines a short - circuit fault and an open - circuit fault of the switching element on the high side and the switching element on the low side based on the detection result of the midpoint voltage acquired from the midpoint voltage detection unit 25.

[0054] Using FIG. 6, a method for detecting the midpoint voltage between the high-side switching element and the low-side switching element will be described. Hereinafter, a method for detecting the midpoint voltage between the switching element Q1 and the switching element Q2 will be described.

[0055] As shown in FIG. 6, the switching element diagnosis unit 24 includes a transistor Tr1, a diode 241, and a resistance element 242.

[0056] The transistor Tr1 is, for example, a bipolar transistor, but is not limited thereto. A voltage Vc from an auxiliary power supply (not shown) is input to the emitter terminal of the transistor Tr1. A control signal S5 from the power supply control unit 34 is input to the base terminal of the transistor Tr1. When the control signal S5 is input to the base terminal of the transistor Tr1, a current corresponding to the voltage Vc input to the emitter terminal flows from the emitter terminal to the collector terminal.

[0057] The anode terminal of the diode 241 is electrically connected to the collector terminal of the transistor Tr1, and the cathode terminal is electrically connected to one end of the resistance element 242.

[0058] One end of the resistance element 242 is electrically connected to the cathode terminal of the diode 241, and the other end is electrically connected to the drain terminal of the switching element Q1. The resistance element 242 is a current-limiting resistance element.

[0059] That is, in the switching element diagnosis unit 24, when the voltage Vc is input to the emitter terminal of the transistor Tr1 and the control signal S5 is input to the base terminal, the voltage Vc is applied to the drain terminal of the switching element Q1.

[0060] The midpoint voltage detection unit 25 includes a Zener diode 251, a resistance element 252, a voltage dividing circuit 253, and a voltage detection unit 254.

[0061] The Zener diode 251 has its anode terminal electrically connected to the source terminal of the switching element Q2, and its cathode terminal electrically connected to one end of the resistance element 252.

[0062] One end of the resistance element 252 is electrically connected to the cathode terminal of the Zener diode 251, and the other end is electrically connected to the other end of the coil L1 whose one end is electrically connected between the switching element Q1 and the switching element Q2.

[0063] The voltage dividing circuit 253 has one end electrically connected to the cathode terminal of the Zener diode 251 and the other end electrically connected to the anode terminal of the Zener diode 251. In other words, the voltage dividing circuit 253 is connected in parallel with the Zener diode 251.

[0064] The voltage detection unit 254 detects the midpoint voltage between the switching element Q1 and the switching element Q2 based on the output from the voltage dividing circuit 253.

[0065] When detecting the midpoint voltage between the switching element Q1 and the switching element Q2, the switching element control unit 33 switches the on state and the off state of the switching element Q1. By detecting the midpoint voltage between the switching element Q1 and the switching element Q2, a failure of the switching element Q1 or the switching element Q2 can be determined.

[0066] For example, when the switching element Q1 is in the off state, if the switching element Q1 is normal, the midpoint voltage between the switching element Q1 and the switching element Q2 is 0. When the switching element Q1 has a short - circuit failure, the midpoint voltage between the switching element Q1 and the switching element Q2 becomes the voltage Vc of the auxiliary power supply input to the switching element diagnostic unit 24.

[0067] For example, when the switching element Q1 is in the on state, if the switching element Q1 is normal, the midpoint voltage between the switching element Q1 and the switching element Q2 becomes the voltage Vc of the auxiliary power supply input to the switching element diagnosis unit 24. When the switching element Q1 has an open fault, the midpoint voltage between the switching element Q1 and the switching element Q2 becomes 0. When the switching element Q2 has a short-circuit fault, the midpoint voltage between the switching element Q1 and the switching element Q2 gradually changes from the voltage Vc of the auxiliary power supply input to the switching element diagnosis unit 24 to 0.

[0068] That is, the fault of the switching element Q1 or the switching element Q2 can be determined based on the state of the switching element Q1 and the value of the midpoint voltage between the switching element Q1 and the switching element Q2.

[0069] Using FIG. 7, the fault determination process of the switching element according to the first embodiment will be described. FIG. 7 is a timing chart for explaining the fault determination process of the switching element according to the first embodiment. Note that the timing chart shown in FIG. 7 is a timing chart when the cutoff switch unit 12 has the configuration shown in FIG. 2 and the cutoff switch unit 18 has the configuration shown in FIG. 3.

[0070] FIG. 7 shows the process of determining the fault of the switching element Q1 or the switching element Q2 of the converter 23 according to the first embodiment.

[0071] In FIG. 7, the period from timing t1 to timing t2 is the confirmation period for the short-circuit fault of the cutoff switch unit 12 and the cutoff switch unit 18. The period from timing t2 to timing t5 is the confirmation period for the midpoint voltage between the switching element Q1 and the switching element Q2.

[0072] In FIG. 7, (a) shows the voltage value of the auxiliary power supply that supplies voltage to the switching element diagnosis unit 24. (b) shows the state of the cutoff switch unit 12. (c) shows the state of the cutoff switch unit 18. (d) shows the state of the switching element Q1. (e) shows the state of the switching element Q2. (f) shows the state of the switching element diagnosis unit 24. (g) shows the voltage value of the midpoint voltage between the switching element Q1 and the switching element Q2. (h) shows that waveform 101 is the detection result of the voltage of the voltage detection unit 14, and waveform 102 is the detection result of the voltage of the voltage detection unit 15. (i) shows that waveform 201 is the detection result of the voltage of the voltage detection unit 20, and waveform 202 is the detection result of the voltage of the voltage detection unit 21.

[0073] The voltage value of the auxiliary power supply is Vc during the period from timing t1 to timing t5. The cutoff switch unit 12, the cutoff switch unit 18, and the switching element Q2 are in the off state during the period from timing t1 to timing t5. The voltage value detected by the voltage detection unit 15 during the period from timing t1 to timing t5 is V1, which is the voltage value of the first power supply 1. The voltage value detected by the voltage detection unit 21 during the period from timing t1 to timing t5 is V2, which is the voltage value of the second power supply 2.

[0074] At timing t1, the switching element diagnosis unit 24 receives the control signal S5 and switches to the on state. As a result, at timing t1, a voltage value of Vc is applied to the drain terminal of the switching element Q1. At timing t1, as shown in waveform 101, the voltage value detected by the voltage detection unit 14 gradually increases.

[0075] At timing t2, as shown in waveform 101, the voltage value detected by the voltage detection unit 14 reaches V1a. During the period from timing t2 to timing t3, if there is no failure in the cutoff switch unit 12 and the cutoff switch unit 18, the detection result of the voltage detection unit 14 is V1a, the detection result of the voltage detection unit 15 is V1, the detection result of the voltage detection unit 20 is 0, and the detection result of the voltage detection unit 21 is V2.

[0076] During the period from timing t3 to timing t4, the switching element Q1 is in the off state, and the midpoint voltage between the switching element Q1 and the switching element Q2 is 0. If a short-circuit fault occurs in the switching element Q1 during the period from timing t3 to timing t4, the value of the midpoint voltage becomes Vc.

[0077] At timing t4, the switching element Q1 becomes in the on state. When the switching element Q1 becomes in the on state, the midpoint voltage between the switching element Q1 and the switching element Q2 gradually increases.

[0078] During the period from timing t4 to timing t5, the midpoint voltage between the switching element Q1 and the switching element Q2 reaches the divided voltage Vc1 obtained by dividing the Vc of the auxiliary power supply according to the voltage dividing circuit 253. When the switching element Q1 has an open fault during the period from timing t4 to timing t5, the midpoint voltage between the switching element Q1 and the switching element Q2 becomes 0. When the switching element Q2 has a short-circuit fault during the period from timing t4 to timing t5, the midpoint voltage between the switching element Q1 and the switching element Q2 gradually changes to 0 after reaching Vc. During the period from timing t4 to timing t5, the detection result of the voltage detection unit 20 reaches V2a which is a predetermined voltage value.

[0079] At timing t5, the switching element Q1 becomes in the off state.

[0080] During the period from timing t5 to timing t6, the midpoint voltage between the switching element Q1 and the switching element Q2 becomes 0. During the period from timing t5 to timing t6, the detection result of the voltage detection unit 20 becomes 0.

[0081] At timing t6, the switching element diagnosis unit 24 becomes in the off state. Thereby, the failure determination process of the switching element according to the first embodiment ends.

[0082] [Processing content] Using FIG. 8, the processing content of the control unit according to the first embodiment will be described. FIG. 8 is a flowchart showing an example of the flow of the failure determination process of the cutoff switch unit according to the first embodiment.

[0083] The processing of the control unit 26 shown in FIG. 8 is processing performed with the cutoff switch unit 12 and the cutoff switch unit 18 in the off state.

[0084] The control unit 26 determines whether the voltage inside the cutoff switch unit 18 on the second power supply 2 side is less than a predetermined value (step S101). Specifically, the control unit 26 determines whether the detection result of the voltage of the voltage detection unit 20 is less than a predetermined value. If it is determined that the voltage inside the cutoff switch unit 18 is less than the predetermined value (step S101; Yes), the process proceeds to step S102. If it is not determined that the voltage inside the cutoff switch unit 18 is less than the predetermined value (step S101; No), the process proceeds to step S104.

[0085] When it is determined Yes in step S101, it is determined whether the voltage inside the cutoff switch unit 12 on the first power supply 1 side is less than a predetermined value (step S102). Specifically, the control unit 26 determines whether the detection result of the voltage of the voltage detection unit 14 is less than a predetermined value. If it is determined that the voltage inside the cutoff switch unit 12 is less than the predetermined value (step S102; Yes), the process proceeds to step S103. If it is not determined that the voltage inside the cutoff switch unit 12 is less than the predetermined value (step S102; No), the process proceeds to step S104.

[0086] When it is determined Yes in step S102, the control unit 26 determines that the cutoff switch unit 12 and the cutoff switch unit 18 are normal (step S103). Specifically, the control unit 26 determines that the cutoff switch unit 12 and the cutoff switch unit 18 are not faulty. Then, the processing of FIG. 8 ends.

[0087] If it is determined as No in step S101 or step S102, the control unit 26 determines that the cutoff switch unit 12 or the cutoff switch unit 18 is abnormal (step S104). Specifically, when it is determined as No in step S101, the control unit 26 determines that the cutoff switch unit 18 has failed. When it is determined as No in step S102, the control unit 26 determines that the cutoff switch unit 12 has failed. When the control unit 26 determines that the cutoff switch unit 12 or the cutoff switch unit 18 has failed, it outputs information to that effect to a higher-level device (not shown). Then, the process of FIG. 8 ends.

[0088] Using FIG. 9, the processing content of the control unit according to the first embodiment will be described. FIG. 9 is a flowchart showing an example of the flow of the failure determination process of the switching element of the cutoff switch unit according to the first embodiment. Hereinafter, the case of determining the failure of the switching element Q1 and the switching element Q2 will be described as an example.

[0089] The processing of the control unit 26 shown in FIG. 9 is processing performed with the cutoff switch unit 12 and the cutoff switch unit 18 in the off state.

[0090] The control unit 26 turns on the switching element diagnosis unit 24 (step S201). Specifically, the control unit 26 outputs the control signal S5 to the switching element diagnosis unit 24 to turn on the switching element diagnosis unit 24. Then, it proceeds to step S202.

[0091] The control unit 26 determines whether or not it has detected a voltage inside the cutoff switch unit 12 on the first power supply 1 side (step S202). Specifically, the control unit 26 determines whether or not the voltage detection unit 20 has detected a voltage. If it is determined that a voltage has been detected inside the cutoff switch unit 12 (step S202; Yes), it proceeds to step S203. If it is not determined that a voltage has been detected inside the cutoff switch unit 12 (step S202; No), it proceeds to step S210.

[0092] If it is determined Yes in step S202, the control unit 26 determines whether the midpoint voltage is 0 (step S203). Specifically, the control unit 26 determines whether the midpoint voltage between the switching element Q1 and the switching element Q2 detected by the midpoint voltage detection unit 25 is 0. If it is determined that the midpoint voltage is 0 (step S203; Yes), the process proceeds to step S204. If it is determined that the midpoint voltage is not 0 (step S203; No), the process proceeds to step S210.

[0093] If it is determined Yes in step S203, the control unit 26 switches the switching element Q1 to the on state (step S204). Then, the process proceeds to step 205.

[0094] The control unit 26 determines whether the midpoint voltage is a predetermined value (step S205). Specifically, the control unit 26 determines whether the midpoint voltage between the switching element Q1 and the switching element Q2 detected by the midpoint voltage detection unit 25 is the voltage Vc of the auxiliary power supply. If it is determined that the midpoint voltage is a predetermined value (step S205; Yes), the process proceeds to step S206. If it is not determined that the midpoint voltage is a predetermined value (step S205; No), the process proceeds to step S210.

[0095] The control unit 26 determines whether the voltage inside the cutoff switch unit 18 on the second power supply 2 side is equal to or higher than a predetermined value (step S206). Specifically, the control unit 26 determines whether the voltage detected by the voltage detection unit 20 is equal to or higher than a predetermined value. If it is determined that the voltage inside the cutoff switch unit 18 is equal to or higher than a predetermined value (step S206; Yes), the process proceeds to step S207. If it is not determined that the voltage inside the cutoff switch unit 18 is equal to or higher than a predetermined value (step S206; No), the process proceeds to step S210.

[0096] If it is determined Yes in step S206, the control unit 26 determines that it is normal (step S207). Specifically, the control unit 26 determines that the switching element Q1, the switching element Q2, and the coil L1 are not faulty. Then, the process proceeds to step S208.

[0097] The control unit 26 switches the switching element Q1 to the off state (step S208). Then, it proceeds to step S209.

[0098] The control unit 26 turns off the switching element diagnostic unit 24 (step S209). Specifically, the control unit 26 stops the control signal S5 to turn off the switching element diagnostic unit 24. Then, the process of FIG. 9 ends.

[0099] If it is determined as No in step S202, No in step S203, No in step S205, or No in step S206, the control unit 26 determines that there is an abnormality (step S210). Specifically, when the control unit 26 determines as No in step S202, it determines that there is an abnormality in the auxiliary power supply. When the control unit 26 determines as No in step S203, it determines that there is a short - circuit fault in the switching element Q1. When the control unit 26 determines as No in step S205 and the detected voltage is 0, it determines that Q1 has an open - circuit fault. When the control unit 26 determines as No in step S205 and the detected voltage changes from the voltage Vc of the auxiliary power supply to 0, it determines that the switching element Q2 has a short - circuit fault. When the control unit 26 determines as No in step S206, it determines that there is a pre - charge abnormality due to the second power supply 2. When the control unit 26 determines as No in step S206, it determines that there is a fault due to the coil L1. An example of a fault due to the coil L1 will be described. For example, in step S206, since the switching element Q1 and the switching element diagnostic unit 24 are in the on state, the voltage Vc of the auxiliary power supply is applied from the coil L1 to the cut - off switch unit 18. Here, the abnormality of the voltage from the auxiliary power supply is determined in step S202. Therefore, for example, when the coil L1 has an open - circuit fault, the control unit 26 determines as No in step S206. Then, the process of FIG. 9 ends.

[0100] As described above, in the first embodiment, with two power supplies connected to the converter 23, the midpoint voltage between the switching element on the high side and the switching element on the low side of the converter 23 is measured to determine whether each switching element has failed. As a result, in the first embodiment, even if a failure has occurred in each switching element, it is possible to determine the failure of each switching element without blowing the fuse provided between the converter 23 and the power supply.

[0101] [Second Embodiment] FIG. 10 is a diagram showing a configuration example of a power supply system according to the second embodiment. The power supply system 100A is different from the power supply system 100 shown in FIG. 1 in that the discharge circuit unit 27 and the control unit 26A includes a discharge circuit driving unit 35.

[0102] After the converter 23 starts operating, when it finishes operating, there may be charge remaining in the capacitors C1 to Cm inside the converter 23. When performing the process of detecting the midpoint voltage before the next operation of the converter 23, if there is charge remaining inside the converter 23, the reference value will change, so it may not be possible to accurately detect the value of the midpoint voltage. Therefore, in the second embodiment, after the operation of the converter 23 ends, the charge inside the converter 23 is discharged.

[0103] One end of the discharge circuit unit 27 is electrically connected to the drain terminal of the switching element on the high side of the converter 23, and the other end is electrically connected to the source terminal of the switching element on the low side of the converter 23. The discharge circuit unit 27 discharges the charge inside the converter 23 according to a control signal from the discharge circuit driving unit 35. The discharge circuit unit 27 discharges the charge inside the converter 23 when the cutoff switch unit 12 and the cutoff switch unit 18 are in the off state. The discharge circuit unit 27 is composed of, for example, a transistor, but is not limited thereto.

[0104] The discharge circuit driving unit 35 outputs a control signal to the discharge circuit unit 27 to drive the discharge circuit unit 27, discharging the charge inside the converter 23. The discharge circuit driving unit 35 outputs a control signal to the discharge circuit unit 27 according to the control from the power supply control unit 34.

[0105] The power supply control unit 34 outputs a control signal to the discharge circuit driving unit 35 to drive the discharge circuit unit 27 by the discharge circuit driving unit 35. For example, when the detection results of the voltages of the voltage detection unit 14 and the voltage detection unit 20 become equal to or lower than a predetermined voltage value, the power supply control unit 34 stops the output of the control signal.

[0106] The discharge process of the converter according to the second embodiment will be described with reference to FIG. 11. FIG. 11 is a timing chart for explaining the discharge process according to the second embodiment. Note that the timing chart shown in FIG. 11 is a timing chart when the cutoff switch unit 12 has the configuration shown in FIG. 2 and the cutoff switch unit 18 has the configuration shown in FIG. 3.

[0107] FIG. 11 shows the process after the operation of the converter 23 ends. In FIG. 11, the period from timing t3 to timing t4 is the period for discharging the charge inside the converter 23.

[0108] In FIG. 11, (a) shows the voltage value of the auxiliary power supply that supplies voltage to the switching element diagnosis unit 24. (b) shows the state of the cutoff switch unit 12. (c) shows the state of the cutoff switch unit 18. (d) shows the state of the switching element Q1. (e) shows the state of the switching element Q2. (f) shows the state of the switching element diagnosis unit 24. (g) shows the voltage value of the midpoint voltage between the switching element Q1 and the switching element Q2. (h) shows that waveform 101 shows the detection result of the voltage of the voltage detection unit 14, and waveform 102 shows the detection result of the voltage of the voltage detection unit 15. (i) shows that waveform 201 shows the detection result of the voltage of the voltage detection unit 20, and waveform 202 shows the detection result of the voltage of the voltage detection unit 21. (j) shows the state of the discharge circuit unit 27.

[0109] At timing t1, each switching element is off and the cutoff switch section 12 is in the off state. During the period from timing t1 to timing t2, the voltage value detected by the voltage detection section 20 decreases.

[0110] At timing t2, the cutoff switch section 18 becomes the off state.

[0111] At timing t3, the discharge circuit section 27 becomes the on state. During the period from timing t3 to timing t4, the discharge circuit section 27 continues to be in the on state.

[0112] During the period from timing t3 to timing t4, the voltage value detected by the voltage detection section 14 decreases. At timing t4, the discharge circuit section 27 becomes the off state.

[0113] During the period from timing t4 to timing t5, since a stop command has occurred from a higher-level device (not shown) or an external device, etc., the auxiliary power supply becomes the off state. Thereby, the discharge process according to the second embodiment ends.

[0114] [Processing content] Using FIG. 12, the processing content of the control section according to the second embodiment will be described. FIG. 12 is a flowchart showing an example of the flow of the discharge process of the converter according to the second embodiment.

[0115] The process shown in FIG. 12 is a process that the control section 26A executes after receiving a stop command from an external device or the like after the operation of the converter ends.

[0116] The control section 26A turns off the cutoff switch section 12 on the first power supply 1 side (step S301). Specifically, the control section 26A turns off the cutoff switch section 12 to electrically cut off the first power supply 1 and the converter 23. Then, it proceeds to step S302.

[0117] The control unit 26A turns off the cutoff switch unit 18 on the second power supply 2 side (step S302). Specifically, the control unit 26A turns off the cutoff switch unit 18 to electrically cut off the second power supply 2 and the converter 23. Then, it proceeds to step S303.

[0118] The control unit 26A turns on the discharge circuit unit 27 (step S303). Specifically, the control unit 26A turns on the discharge circuit unit 27 to discharge the charge inside the converter 23. Then, it proceeds to step S304.

[0119] The control unit 26A waits for a predetermined time (step S304). Specifically, the control unit 26A waits until the charge of the converter 23 is discharged. Then, it proceeds to step S305.

[0120] The control unit 26A determines whether the voltage inside the cutoff switch unit 18 on the second power supply 2 side is less than a predetermined value (step S305). Specifically, the control unit 26A determines whether the voltage value detected by the voltage detection unit 20 is less than a predetermined value. More specifically, the control unit 26A determines whether the voltage value detected by the voltage detection unit 20 is less than the voltage V2 of the second power supply 2. If it is determined that the voltage inside the cutoff switch unit 18 is less than a predetermined value (step S305; Yes), it proceeds to step S306. If it is not determined that the voltage inside the cutoff switch unit 18 is less than a predetermined value (step S305; No), it proceeds to step S308.

[0121] If it is determined Yes in step S305, the control unit 26A determines whether the voltage inside the cutoff switch unit 12 on the first power supply 1 side is less than a predetermined value (step S306). Specifically, the control unit 26A determines whether the voltage value detected by the voltage detection unit 14 is less than the predetermined value. More specifically, the control unit 26A determines whether the voltage value detected by the voltage detection unit 14 is less than the voltage V1 of the first power supply 1. If it is determined that the voltage inside the cutoff switch unit 12 is less than the predetermined value (step S306; Yes), the process proceeds to step S307. If it is not determined that the voltage inside the cutoff switch unit 12 is less than the predetermined value (step S306; No), the process proceeds to step S308.

[0122] If it is determined Yes in step S306, the control unit 26A turns off the discharge circuit unit 27 (step S307). Specifically, the control unit 26A turns off the discharge circuit unit 27 to end the discharge process of the converter 23. Then, the process of FIG. 12 ends.

[0123] If it is determined No in step S305 or if it is determined No in step S306, the control unit 26A determines that the cutoff switch unit 12 or the cutoff switch unit 18 is malfunctioning (step S308). Specifically, when it is determined No in step S305, the control unit 26A determines that the cutoff switch unit 18 has a short - circuit failure. When it is determined No in step S306, the control unit 26A determines that the cutoff switch unit 12 has a short - circuit failure. Then, the process of FIG. 12 ends.

[0124] As described above, the second embodiment can discharge the charge inside the converter 23 after the operation of the converter 23 ends. Thereby, the second embodiment can make the state before and after the startup of the converter 23 the same. Therefore, when the converter 23 is restarted, the mid - point voltage between the high - side switching element and the low - side switching element can be appropriately detected.

[0125] The embodiments of the present disclosure have been described above, but the present disclosure is not limited by the contents of these embodiments. Further, the above-described components include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within the so-called equivalent range. Furthermore, the above-described components can be combined as appropriate. Still further, various omissions, substitutions, or changes of the components can be made without departing from the gist of the above-described embodiments.

Description of Reference Numerals

[0126] 1 First power supply 2 Second power supply 3, 4 Fuses 10 Control device 11, 17 Current detection unit 12, 18 Cut-off switch unit 13, 19 Overcurrent detection unit 14, 15, 20, 21, 254 Voltage detection unit 16, 22 Output capacitor 23 Converter 24 Switching element diagnosis unit 241 Diode 242, 252 Resistance element 25 Midpoint voltage detection unit 251 Zener diode 253 Voltage dividing circuit 26, 26A Control unit 27 Discharge circuit unit 30, 31 Cut-off switch drive unit 33 Switching element control unit 34 Power supply control unit 35 Discharge circuit drive unit 100 Power supply system

Claims

1. A converter including at least one each of a high-side switch element provided between a first power source and a second power source and having a drain terminal electrically connected to a power line, and a low-side switch element having a drain terminal electrically connected to a source terminal of the high-side switch element and a source terminal electrically connected to a ground line; A first cutoff switch section having one end electrically connected to a positive electrode of the first power source and the other end electrically connected to the drain terminal of the high-side switch element; A second cutoff switch section having one end electrically connected to a positive electrode of the second power source and the other end electrically connected to the source terminal of the high-side switch element; A midpoint voltage detection section for detecting a midpoint voltage between the high-side switch element and the low-side switch element; A control section for controlling states of the first cutoff switch section and the second cutoff switch section to an off state when the midpoint voltage detection section detects the midpoint voltage; A control device comprising the above.

2. The control section determines a failure of at least one of the high-side switch element and the low-side switch element based on a detection result of the midpoint voltage by the midpoint voltage detection section. The control device according to Claim 1. The control device according to Claim 1.

3. An auxiliary power source for applying an auxiliary voltage to the drain of the high-side switch element is provided, and the control section determines a failure of at least one of the high-side switch element and the low-side switch element based on a detection result of the midpoint voltage by the midpoint voltage detection section in a state where the auxiliary voltage is applied to the drain terminal of the high-side switch element. The control device according to Claim 1 or 2. The control device according to Claim 1 or 2.

4. Each of the first cutoff switch section and the second cutoff switch section includes at least one semiconductor element. The control device according to any one of Claims 1 to 3. The control device according to any one of Claims 1 to 3.

5. In a converter including at least one each of a high-side switch element provided between a first power source and a second power source and having a drain terminal electrically connected to a power line, and a low-side switch element having a drain terminal electrically connected to a source terminal of the high-side switch element and a source terminal electrically connected to a ground line, a step of detecting a midpoint voltage between the high-side switch element and the low-side switch element. ​ When detecting the midpoint voltage, a step of controlling a first cutoff switch portion having one end electrically connected to the positive electrode of the first power supply and the other end electrically connected to the drain terminal of the high-side switch element, and a second cutoff switch portion having one end electrically connected to the positive electrode of the second power supply and the other end electrically connected to the source terminal of the high-side switch element to an off state; A control method including the above.

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