JP7702267B2 - Control device and control method - Google Patents

Description

This disclosure relates to a control device and a control method.

There is a known technology for a vehicle power supply device that, even if an abnormality occurs on the higher voltage side of a specified position of the power supply device, supplies power from a power storage unit on the lower voltage side of the specified position to a path on the lower voltage side (see Patent Document 1).

JP 2018-148733 A

Non-isolated DC-DC converters are installed in systems such as vehicles, with two power sources, such as batteries or storage batteries, connected to them. If the main switch of the DC-DC converter fails, an overcurrent may occur even before operation, causing the fuse to blow.

The present disclosure aims to provide a control device and control method that can suppress overcurrent in a system equipped with a DC-DC converter in advance or before the DC-DC converter operates.

The control device according to the present disclosure includes a converter provided between a first power source and a second power source, the converter including at least one high-side switch element having a drain terminal electrically connected to a power source 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 shutoff switch unit having one end electrically connected to the 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 shutoff switch unit having one end electrically connected to the positive electrode of the second power source 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 state of the first shutoff switch unit and the second shutoff switch unit to an off state when the midpoint voltage detection unit detects the midpoint voltage.

In the control device according to the present disclosure, the control unit determines whether at least one of the high-side switch element and the low-side switch element is faulty based on the result of detection of the midpoint voltage by the midpoint voltage detection unit.

The control device according to the present disclosure includes an auxiliary power supply that applies an auxiliary voltage to the drain of the high-side switch element, and the control unit determines whether at least one of the high-side switch element and the low-side switch element is faulty based on the midpoint voltage detection result by the midpoint voltage detection unit when the auxiliary voltage is applied to the drain terminal of the high-side switch element.

In the control device according to the present disclosure, the first shutoff switch unit and the second shutoff switch unit each include at least one semiconductor element.

The control method according to the present disclosure includes, in a converter including at least one 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 source line, and at least one 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, the steps of: detecting a midpoint voltage between the high-side switch element and the low-side switch element; and, when detecting the midpoint voltage, controlling to an off state a first cutoff switch unit having one end electrically connected to the positive electrode of the first power source 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 the positive electrode of the second power source and the other end electrically connected to the drain terminal of the high-side switch element.

According to the present disclosure, it is possible to suppress overcurrent in a system equipped with a DC-DC converter in advance or before the DC-DC converter operates.

FIG. 1 is a diagram showing an example of the configuration of a power supply system according to the first embodiment. FIG. 2 is a diagram illustrating an example of the configuration of the cutoff switch unit. FIG. 3 is a diagram showing a configuration example of a modified example of the cutoff switch unit. FIG. 4 is a diagram showing a configuration example of a modified example of the cutoff switch unit. FIG. 5 is a diagram showing a configuration example of a modified example of the cutoff switch unit. FIG. 6 is a diagram for explaining a method for detecting a midpoint voltage between a high-side switching element and a low-side switching element. FIG. 7 is a timing chart for explaining the fault determination process for the switching element according to the first embodiment. FIG. 8 is a flowchart showing an example of the flow of a failure determination process for the shutoff switch unit according to the first embodiment. FIG. 9 is a flowchart showing an example of the flow of a failure determination process for a switching element of the cutoff switch unit according to the first embodiment. FIG. 10 is a diagram showing an example of the configuration of a power supply system according to the second embodiment. FIG. 11 is a timing chart for explaining the discharge process according to the second embodiment. FIG. 12 is a flowchart showing an example of the flow of a discharge process of the converter according to the second embodiment.

Below, an embodiment of the present disclosure will be described in detail with reference to the attached drawings. Note that the present disclosure is not limited to this embodiment, and in the following embodiments, the same parts are designated by the same reference numerals to avoid redundant description.

[First embodiment]
1 is a diagram showing an example of the configuration of a power supply system according to a 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.

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

The second power source 2 is a power supply device that supplies power to the control device 10. The second power source 2 is a power supply device that outputs a lower voltage than the first power source 1. The voltage of the second power source 2 is, for example, 12 V, but is not limited to this. The second power source 2 may be, for example, a capacitor. The second power source 2 outputs a voltage to an in-vehicle device such as a windshield wiper.

One end of the fuse 3 is electrically connected to the positive electrode of the first power source 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 source 1. The fuse 3 is a current fuse that melts due to self-heating when the current passing through it exceeds the rated current. The fuse 3 melts when an excessive current exceeding the rated current flows from the control device 10, preventing the excessive current from flowing into the first power source 1 and various devices connected to the first power source 1.

One end of the fuse 4 is electrically connected to the positive electrode of the second power source 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 source 2. The fuse 4 is a current fuse that melts due to self-heating when the current passing through it exceeds the rated current. The fuse 4 melts when an excessive current exceeding the rated current flows from the control device 10, preventing the excessive current from flowing into the second power source 2.

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.

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 according 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 to this.

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 source 1 and the converter 23. The cutoff switch unit 12 is also called the first cutoff switch unit.

Figure 2 is a diagram showing an example of the configuration of the cutoff switch unit. In Figure 2, the fuse 3 and the current detection unit 11 are omitted. As shown in Figure 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). In other words, the cutoff switch unit 12 is composed of a semiconductor element. When the switching element Q11 is in an off state, it electrically cuts off the first power source 1 and the converter 23. When a control signal is input to the gate of the switching element Q11, the switching element Q11 switches to an on state and electrically connects the first power source 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), or the like.

The configuration of the shutoff switch unit 12 is not limited to the example configuration shown in FIG. 2. FIGS. 3, 4, and 5 are diagrams showing modified examples of the shutoff switch unit.

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 source 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.

As shown in FIG. 4, the shutoff switch unit 12B may include a switching element Q11 and a switching element Q12. The shutoff switch unit 12B differs from the shutoff 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.

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

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, according to an overcurrent diagnosis signal from the control unit 26. For example, when the overcurrent detection unit 13 detects an overcurrent, it outputs a control signal to the overcurrent stop circuit unit 32.

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 a first voltage detection unit.

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 a second voltage detection unit.

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.

The current detection unit 17 has one end electrically connected to the fuse 4 and the other end 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 according 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 to this.

The shutoff switch unit 18 has one end electrically connected to the current detection unit 17 and the other end connected to the converter 23. The shutoff switch unit 18 is configured to cut off the electrical connection between the second power source 2 and the converter 23. The shutoff switch unit 18 can be configured in the same manner as the shutoff switch unit 12 shown in Figures 2 to 5. The shutoff switch unit 18 is also called a second shutoff switch unit.

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 an overcurrent diagnosis signal from the control unit 26. For example, when the overcurrent detection unit 19 detects an overcurrent, it outputs a control signal to the overcurrent stop circuit unit 32.

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 a third voltage detection unit.

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.

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.

Converter 23 is a bidirectional DC-DC converter. Converter 23 includes switching element Q1, switching element Q3, ..., switching element Qp (p is any odd number) on the high side. Converter 23 includes switching element Q2, switching element Q4, ..., switching element Qn (n is any even number) on the low side. Converter 23 includes the same number of switching elements on both the high side and the low side. Converter 23 needs to include at least switching element Q1 on the high side and switching element Q2 on the low side.

The drain terminals of the high-side switching elements Q1, Q3, ..., Qp are electrically connected to a high potential (the power line of the first power source 1). The drain terminals of the high-side switching elements Q1, Q3, ..., Qp are electrically connected to the cutoff switch unit 12. The source terminals of the high-side switching elements Q1, Q3, ..., Qp are electrically connected to the drain terminals of the low-side switching elements Q2, Q4, ..., Qn.

The source terminals of the low-side switching elements Q2, Q4, ..., Qn are each electrically connected to a low potential (ground line).

Converter 23 includes capacitors C1, C2, ..., Cm (where m is any integer).

One end of the capacitor C1 is electrically connected to the drain terminal of the switching element Q1, and the other end is electrically connected to the source terminal of the switching element Q2. One end of the capacitor C2 is electrically connected to the drain terminal of the switching element Q3, and the other end is electrically connected to the source terminal of the switching element Q4. One end of the capacitor Cm is electrically connected to the drain terminal of the switching element Qp, and the other end is electrically connected to the source terminal of the switching element Qn. That is, in the converter 23, the 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.

The converter 23 includes coil L1, coil L2, ..., coil Lm.

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

The switching element diagnostic unit 24 outputs a signal for determining a failure of each switch element of the converter 23. The switching element diagnostic unit 24 outputs, for example, a voltage Vc from an auxiliary power source different from the first power source 1 and the second power source 2 as a signal for determining a failure of each switch element of the converter 23. The auxiliary power source is, for example, a power source (not shown) that generates the power required inside the converter 23.

The midpoint voltage detection unit 25 detects the midpoint voltage, which is the voltage between each switch element on the high side and each switch element on the low side. The midpoint voltage detection unit 25 detects, for example, the midpoint voltage between switching element Q1 and switching element Q2.

The control unit 26 includes a cutoff switch drive unit 30, a cutoff switch drive unit 31, an overcurrent stop circuit unit 32, a switching element control unit 33, and a power supply control unit 34.

The shutoff switch drive unit 30 switches the shutoff switch unit 12 between the on and off states. For example, when measuring the midpoint voltage between the high-side switching element and the low-side switching element of the converter 23, the shutoff switch drive unit 30 turns the shutoff switch unit 12 off.

The shutoff switch drive unit 31 switches the shutoff switch unit 18 between the on and off states. For example, when measuring the midpoint voltage between the high-side switching element and the low-side switching element of the converter 23, the shutoff switch drive unit 31 turns the shutoff switch unit 18 off.

The overcurrent stop circuit unit 32 outputs a control signal to stop each switching element of the converter 23 when the overcurrent detection unit 13 or the overcurrent detection unit 19 detects an overcurrent.

The switching element control unit 33 controls each switching element of the converter 23. For example, when the overcurrent detection unit 13 or the overcurrent detection unit 19 detects an overcurrent, the switching element control unit 33 controls each switching element of the converter 23 according to a 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 in order to determine whether the target switching element of the converter 23 has a short-circuit failure. The switching element control unit 33 switches the target switching element of the converter 23 to the ON state in order to determine whether the target switching element of the converter 23 has an open-circuit failure.

The power supply control unit 34 controls each unit 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 shutoff switch drive unit 30 to control the shutoff switch unit 12. For example, the power supply control unit 34 outputs a control signal S4 to the shutoff switch drive unit 31 to control the shutoff 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 a 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.

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 the short-circuit failure 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.

The power supply control unit 34 obtains the detection result of the midpoint voltage between the high-side switching element and the low-side switching element of the converter 23 from the midpoint voltage detection unit 25. Based on the detection result of the midpoint voltage obtained from the midpoint voltage detection unit 25, the power supply control unit 34 determines whether there is a short-circuit fault or an open-circuit fault in the high-side switching element and the low-side switching element.

Using FIG. 6, we will explain a method for detecting the midpoint voltage between the high-side switching element and the low-side switching element. Below, we will explain a method for detecting the midpoint voltage between switching element Q1 and switching element Q2.

As shown in FIG. 6, the switching element diagnostic unit 24 includes a transistor Tr1, a diode 241, and a resistor element 242.

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

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 resistor element 242.

One end of the resistor 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 resistor element 242 is a resistor element for limiting current.

That is, the switching element diagnostic unit 24 applies voltage Vc to the drain terminal of the switching element Q1 by inputting voltage Vc to the emitter terminal of transistor Tr1 and control signal S5 to the base terminal.

The midpoint voltage detection unit 25 includes a Zener diode 251, a resistive element 252, a voltage divider circuit 253, and a voltage detection unit 254.

The anode terminal of the Zener diode 251 is electrically connected to the source terminal of the switching element Q2, and the cathode terminal is electrically connected to one end of the resistor element 252.

One end of the resistor 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, one end of which is electrically connected between the switching element Q1 and the switching element Q2.

One end of the voltage divider circuit 253 is electrically connected to the cathode terminal of the Zener diode 251, and the other end is electrically connected to the anode terminal of the Zener diode 251. In other words, the voltage divider circuit 253 is connected in parallel to the Zener diode 251.

The voltage detection unit 254 detects the midpoint voltage between the switching elements Q1 and Q2 based on the output from the voltage divider circuit 253.

The switching element control unit 33 switches the on state and off state of the switching element Q1 when detecting the midpoint voltage between the switching elements Q1 and Q2. By detecting the midpoint voltage between the switching elements Q1 and Q2, it is possible to determine whether the switching element Q1 or the switching element Q2 is faulty.

For example, when switching element Q1 is in the off state, if switching element Q1 is normal, the midpoint voltage between switching element Q1 and switching element Q2 is 0. If switching element Q1 has a short-circuit fault, the midpoint voltage between switching element Q1 and switching element Q2 becomes the auxiliary power supply voltage Vc input to the switching element diagnosis unit 24.

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

In other words, a fault in switching element Q1 or switching element Q2 can be determined based on the state of switching element Q1 and the value of the midpoint voltage between switching element Q1 and switching element Q2.

The fault determination process for the switching element according to the first embodiment will be described with reference to FIG. 7. FIG. 7 is a timing chart for describing the fault determination process for the switching element according to the first embodiment. Note that the timing chart shown in FIG. 7 is a timing chart for the case where the shutoff switch unit 12 has the configuration shown in FIG. 2 and the shutoff switch unit 18 has the configuration shown in FIG. 3.

Figure 7 shows the process of determining whether switching element Q1 or switching element Q2 of converter 23 in the first embodiment has a fault.

In FIG. 7, the period from timing t1 to timing t2 is the period for checking for a short-circuit fault between the shutoff switch unit 12 and the shutoff switch unit 18. The period from timing t2 to timing t5 is the period for checking the midpoint voltage between the switching element Q1 and the switching element Q2.

In FIG. 7, (a) shows the voltage value of the auxiliary power supply that supplies voltage to the switching element diagnostic unit 24. (b) shows the state of the shutoff switch unit 12. (c) shows the state of the shutoff 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 diagnostic unit 24. (g) shows the voltage value of the midpoint voltage between the switching elements Q1 and Q2. (h) shows the waveform 101 indicating the voltage detection result of the voltage detection unit 14, and the waveform 102 indicating the voltage detection result of the voltage detection unit 15. (i) shows the waveform 201 indicating the voltage detection result of the voltage detection unit 20, and the waveform 202 indicating the voltage detection result of the voltage detection unit 21.

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

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

At time t2, as shown in waveform 101, the voltage value detected by voltage detection unit 14 reaches V1a. If there are no failures in shutoff switch unit 12 and shutoff switch unit 18 during the period from time t2 to time t3, the detection result of voltage detection unit 14 will be V1a, the detection result of voltage detection unit 15 will be V1, the detection result of voltage detection unit 20 will be 0, and the detection result of voltage detection unit 21 will be V2.

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

At timing t4, switching element Q1 is turned on. When switching element Q1 is turned on, the midpoint voltage between switching element Q1 and switching element Q2 gradually increases.

During the period from timing t4 to timing t5, the midpoint voltage between switching element Q1 and switching element Q2 reaches a divided voltage Vc1 obtained by dividing the auxiliary power supply Vc according to the voltage divider circuit 253. If switching element Q1 has an open circuit fault during the period from timing t4 to timing t5, the midpoint voltage between switching element Q1 and switching element Q2 becomes 0. If switching element Q2 has a short circuit fault during the period from timing t4 to timing t5, the midpoint voltage between switching element Q1 and 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 a predetermined voltage value V2a.

At time t5, switching element Q1 turns off.

During the period from timing t5 to timing t6, the midpoint voltage between switching element Q1 and 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.

At timing t6, the switching element diagnostic unit 24 is turned off. This ends the fault determination process for the switching element according to the first embodiment.

[Processing content]
The processing contents of the control unit according to the first embodiment will be described with reference to Fig. 8. Fig. 8 is a flowchart showing an example of the flow of a failure determination process of the cutoff switch unit according to the first embodiment.

The processing of the control unit 26 shown in FIG. 8 is performed with the shutoff switch unit 12 and the shutoff switch unit 18 in the OFF state.

The control unit 26 determines whether the voltage inside the cutoff switch unit 18 on the second power source 2 side is less than a predetermined value (step S101). Specifically, the control unit 26 determines whether the voltage detection result 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.

If the answer to step S101 is Yes, it is determined whether or not the voltage inside the cutoff switch unit 12 on the first power source 1 side is less than a predetermined value (step S102). Specifically, the control unit 26 determines whether or not the voltage detection result 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.

If step S102 returns Yes, the control unit 26 determines that the shutoff switch unit 12 and the shutoff switch unit 18 are normal (step S103). Specifically, the control unit 26 determines that the shutoff switch unit 12 and the shutoff switch unit 18 are not malfunctioning. Then, the process of FIG. 8 ends.

If step S101 or step S102 is judged as No, the control unit 26 judges that the shutoff switch unit 12 or the shutoff switch unit 18 is abnormal (step S104). Specifically, if step S101 is judged as No, the control unit 26 judges that the shutoff switch unit 18 is malfunctioning. If step S102 is judged as No, the control unit 26 judges that the shutoff switch unit 12 is malfunctioning. If the control unit 26 judges that the shutoff switch unit 12 or the shutoff switch unit 18 is malfunctioning, it outputs information to that effect to a higher-level device (not shown). Then, the processing of FIG. 8 ends.

The processing contents of the control unit according to the first embodiment will be described using FIG. 9. FIG. 9 is a flowchart showing an example of the flow of the fault determination process of the switching elements of the cutoff switch unit according to the first embodiment. Below, an example will be described in which faults are determined for switching elements Q1 and Q2.

The processing of the control unit 26 shown in FIG. 9 is performed when the shutoff switch unit 12 and the shutoff switch unit 18 are in the off state.

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

The control unit 26 determines whether or not a voltage has been detected inside the cutoff switch unit 12 on the first power source 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), the process proceeds to step S203. If it is not determined that a voltage has been detected inside the cutoff switch unit 12 (step S202; No), the process proceeds to step S210.

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

If step S203 returns Yes, the control unit 26 switches the switching element Q1 to the ON state (step S204). Then, the process proceeds to step 205.

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.

The control unit 26 determines whether the voltage inside the cutoff switch unit 18 on the second power source 2 side is equal to or greater 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 greater than a predetermined value. If it is determined that the voltage inside the cutoff switch unit 18 is equal to or greater than the 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 greater than the predetermined value (step S206; No), the process proceeds to step S210.

If step S206 returns Yes, the control unit 26 determines that they are 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.

The control unit 26 switches the switching element Q1 to the OFF state (step S208). Then, the process proceeds to step S209.

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

If it is determined that 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, if it is determined that No in step S202, the control unit 26 determines that there is an abnormality in the auxiliary power supply. If it is determined that No in step S203, the control unit 26 determines that there is a short-circuit failure in the switching element Q1. If it is determined that No in step S205 and the detected voltage is 0, the control unit 26 determines that Q1 has an open circuit failure. If it is determined that No in step S205 and the detected voltage changes from the voltage Vc of the auxiliary power supply to 0, the control unit 26 determines that there is a short circuit failure in the switching element Q2. If it is determined that No in step S206, the control unit 26 determines that there is a precharge abnormality caused by the second power supply 2. If the determination in step S206 is No, the control unit 26 determines that the fault is due to the coil L1. An example of a fault due to the coil L1 will be described. For example, in step S206, the switching element Q1 and the switching element diagnostic unit 24 are in the ON state, so that the voltage Vc of the auxiliary power supply is applied from the coil L1 to the cutoff switch unit 18. Here, an abnormality in the voltage from the auxiliary power supply is determined in step S202. Therefore, for example, if the coil L1 has an open fault, the control unit 26 determines No in step S206. Then, the process of FIG. 9 ends.

As described above, in the first embodiment, with two power sources connected to the converter 23, a fault determination can be performed for each switching element by measuring the midpoint voltage of the high-side switching element and the low-side switching element of the converter 23. As a result, in the first embodiment, even if a fault occurs in each switching element, a fault determination can be performed for each switching element without blowing a fuse provided between the converter 23 and the power source.

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

After converter 23 starts operating, when the operation ends, charge may remain in capacitors C1 to Cm inside converter 23. When converter 23 performs a process to detect the midpoint voltage before the next operation, if charge remains inside converter 23, the reference value will change, and it may not be possible to detect an accurate midpoint voltage value. Therefore, in the second embodiment, the charge inside converter 23 is discharged after converter 23 ends its operation.

The discharge circuit unit 27 has one end electrically connected to the drain terminal of the switching element on the high side of the converter 23, and the other end 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 in accordance with a control signal from the discharge circuit drive 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 to this.

The discharge circuit drive unit 35 outputs a control signal to the discharge circuit unit 27 to drive the discharge circuit unit 27 and discharge the charge inside the converter 23. The discharge circuit drive unit 35 outputs a control signal to the discharge circuit unit 27 according to the control from the power supply control unit 34.

The power supply control unit 34 outputs a control signal to the discharge circuit drive unit 35 to cause the discharge circuit drive unit 35 to drive the discharge circuit unit 27. For example, when the voltage detection results 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 outputting the control signal.

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 for the case where 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.

Figure 11 shows the processing after the operation of the converter 23 ends. In Figure 11, the period from timing t3 to timing t4 is the period during which the charge inside the converter 23 is discharged.

In FIG. 11, (a) shows the voltage value of the auxiliary power supply that supplies voltage to the switching element diagnostic unit 24. (b) shows the state of the shutoff switch unit 12. (c) shows the state of the shutoff 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 diagnostic unit 24. (g) shows the voltage value of the midpoint voltage between the switching elements Q1 and Q2. (h) shows the waveform 101 indicating the voltage detection result of the voltage detection unit 14, and the waveform 102 indicating the voltage detection result of the voltage detection unit 15. (i) shows the waveform 201 indicating the voltage detection result of the voltage detection unit 20, and the waveform 202 indicating the voltage detection result of the voltage detection unit 21. (j) shows the state of the discharge circuit unit 27.

At timing t1, the cutoff switch unit 12 is turned off while all switching elements are turned off. During the period from timing t1 to timing t2, the voltage value detected by the voltage detection unit 20 decreases.

At timing t2, the cutoff switch unit 18 is turned off.

At timing t3, the discharge circuit unit 27 is turned on. During the period from timing t3 to timing t4, the discharge circuit unit 27 continues to be in the on state.

During the period from timing t3 to timing t4, the voltage value detected by the voltage detection unit 14 decreases. At timing t4, the discharge circuit unit 27 is turned off.

During the period from timing t4 to timing t5, the auxiliary power supply is turned off due to a command from a higher-level device (not shown) or a stop command from an external device. This ends the discharge process according to the second embodiment.

[Processing content]
The processing contents of the control unit according to the second embodiment will be described with reference to Fig. 12. Fig. 12 is a flowchart showing an example of the flow of the discharge processing of the converter according to the second embodiment.

The process shown in FIG. 12 is performed by the control unit 26A after the converter has finished operating and after it receives a stop command from an external device, etc.

The control unit 26A turns off the cutoff switch unit 12 on the first power source 1 side (step S301). Specifically, the control unit 26A turns off the cutoff switch unit 12 to electrically cut off the first power source 1 and the converter 23. Then, the process proceeds to step S302.

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

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, the process proceeds to step S304.

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

The control unit 26A determines whether the voltage inside the cutoff switch unit 18 on the second power source 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 source 2. If it is determined that the voltage inside the cutoff switch unit 18 is less than the predetermined value (step S305; Yes), the process proceeds to step S306. If it is not determined that the voltage inside the cutoff switch unit 18 is less than the predetermined value (step S305; No), the process proceeds to step S308.

If the answer to step S305 is Yes, the control unit 26A determines whether the voltage inside the cutoff switch unit 12 on the first power source 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 a 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 source 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.

If the determination in step S306 is Yes, 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 and ends the discharge process of the converter 23. Then, the process of FIG. 12 ends.

If step S305 is judged as No or if step S306 is judged as No, the control unit 26A judges that the shutoff switch unit 12 or the shutoff switch unit 18 has a fault (step S308). Specifically, if step S305 is judged as No, the control unit 26A judges that the shutoff switch unit 18 has a short-circuit fault. If step S306 is judged as No, the control unit 26A judges that the shutoff switch unit 12 has a short-circuit fault. Then, the processing of FIG. 12 ends.

As described above, in the second embodiment, the electric charge inside the converter 23 can be discharged after the operation of the converter 23 ends. As a result, in the second embodiment, the state before and after the start of the converter 23 can be made the same, so that when the converter 23 is restarted, the midpoint voltage between the switching element on the high side and the switching element on the low side can be appropriately detected.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the contents of these embodiments. The above-mentioned components include those that a person skilled in the art can easily imagine, those that are substantially the same, and those that are within the so-called equivalent range. Furthermore, the above-mentioned components can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the components can be made without departing from the spirit of the above-mentioned embodiments.

REFERENCE SIGNS LIST 1 First power supply 2 Second power supply 3, 4 Fuse 10 Control device 11, 17 Current detection section 12, 18 Shutdown switch section 13, 19 Overcurrent detection section 14, 15, 20, 21, 254 Voltage detection section 16, 22 Output capacitor 23 Converter 24 Switching element diagnostic section 241 Diode 242, 252 Resistance element 25 Midpoint voltage detection section 251 Zener diode 253 Voltage divider circuit 26, 26A Control section 27 Discharge circuit section 30, 31 Shutdown switch drive section 33 Switching element control section 34 Power supply control section 35 Discharge circuit drive section 100 Power supply system

Claims (5)

a converter including at least one high-side switch element provided between a first power source and a second power source, the high-side switch element having a drain terminal electrically connected to a power source 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 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 source 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;
a control unit that controls the first shutoff switch unit and the second shutoff switch unit to an off state when the midpoint voltage detection unit detects the midpoint voltage;
A control device comprising: 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.
The control device according to claim 1 . an auxiliary power supply that applies an auxiliary voltage to a drain of the high-side switch element;
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 in which an auxiliary voltage is applied to a drain terminal of the high-side switch element.
The control device according to claim 1 or 2. The first shutoff switch unit and the second shutoff switch unit each include at least one semiconductor element.
The control device according to any one of claims 1 to 3. In a converter including at least one high-side switch element provided between a first power source and a second power source, the high-side switch element having a drain terminal electrically connected to a power source 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, the converter comprises: detecting a midpoint voltage between the high-side switch element and the low-side switch element;
a step of controlling, when detecting the midpoint voltage, a first shutoff switch unit, one end of which is electrically connected to the positive electrode of the first power supply and the other end of which is electrically connected to the drain terminal of the high-side switch element, and a second shutoff switch unit, one end of which is electrically connected to the positive electrode of the second power supply and the other end of which is electrically connected to the source terminal of the high-side switch element, to an off state;
A control method comprising:

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