Diagnostic system

Abstract

To provide a diagnostic system capable of diagnosing the state of a semiconductor switch while uninterruptedly supplying power.SOLUTION: A diagnostic system comprises a controller that transmits a control command to a semiconductor switch for turning on-off of the semiconductor switch and detects the voltage of the semiconductor switch. A plurality of semiconductor switches includes a first semiconductor switch, a second semiconductor switch, a third semiconductor switch and a fourth semiconductor switch, and is electrically connected to a power supply part. The first semiconductor switch is series connected to the second semiconductor switch. The third semiconductor switch is series connected to the fourth semiconductor switch. A first series circuit in which the first semiconductor switch is series connected to the second semiconductor switch, and a second series circuit in which the third semiconductor switch is series connected to the fourth semiconductor switch are connected in parallel. The controller diagnoses the abnormal condition of the semiconductor switch on the basis of the instruction contents instructed to the semiconductor switch by the control command and the voltage of the semiconductor switch.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a diagnostic device.

Background Art

[0002] Conventionally, a vehicle power supply system that supplies power to an electrical load has been known. For example, the vehicle power supply system described in Patent Document 1 includes an alternator, a lead-acid battery and a lithium-ion battery, a MOS switch that conducts and interrupts both batteries, and an ECU. The ECU turns off the MOS switch during non-regenerative power generation to supply power from the lithium-ion battery to the electrical load, and turns on the MOS switch during regenerative power generation to perform charging (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above vehicle power supply system, when the MOS switch is turned off to diagnose the stuck state of the MOS switch, there is a problem that the power supply from the power source including the alternator and the lead battery to the electrical load is interrupted.

[0005] The problem to be solved by the present invention is to provide a diagnostic device that can diagnose the state of a semiconductor switch without interrupting the power supply.

Means for Solving the Problems

[0006] The present invention electrically connects a plurality of semiconductor switches to a power supply unit, connects a first semiconductor switch and a second semiconductor switch in series with the forward direction of a first parasitic diode and the forward direction of a second parasitic diode being opposite to each other, connects a third semiconductor switch and a fourth semiconductor switch in series with the forward direction of a third parasitic diode and the forward direction of a fourth parasitic diode being opposite to each other, connects a first series circuit connecting the first semiconductor switch and the second semiconductor switch in series and a second series circuit connecting the third semiconductor switch and the fourth semiconductor switch in series in parallel, and diagnoses an abnormal state of the semiconductor switches based on the instruction content to the semiconductor switches indicated by a control command and the voltage of the semiconductor switches, thereby solving the above problems.

Effect of the Invention

[0007] The present invention can diagnose the state of semiconductor switches.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] FIG. 1 is a block diagram of a power supply system 100 according to an embodiment of the present invention. The power supply system 100 according to this embodiment is a system for supplying the power generated by a generator 1 and / or the power of batteries 2 and 13 to loads 3 and 4 to operate the loads 3 and 4. Further, the power supply system 100 is a system for charging the battery 13 with the power generated by the generator 1, or a system for charging and discharging between the battery 2 and the battery 13. The power supply system 100 is provided, for example, in a vehicle, and supplies power from a generator or an in-vehicle battery to loads such as accessories of an in-vehicle display.

[0011] The power supply system 100 includes a generator 1, a battery 2, loads 3 and 4, and a power supply device 10. The generator 1 corresponds to a motor for a vehicle and generates electric power by regeneration of the motor. Note that the generator 1 may be electrically connected to a high-voltage battery (not shown in FIG. 1). The battery 2 is a battery for auxiliary equipment, for example, a lead-acid secondary battery. The load 3 is a load that operates with the electric power generated by the generator 1 or the electric power of the battery 2. The load 3 is, for example, a lamp, a heater, a fan of air-conditioning equipment, etc. The load 3 may operate with the electric power of the battery 13. The generator 1 and the battery 2 are electrically connected to the load 3. The generator 1 and the battery 2 are connected to the load 4 via a circuit breaker 11. Also, the generator 1 and the battery 2 are connected to the load 4 via circuit breakers 11 and 12.

[0012] The load 4 is an in-vehicle load other than the load 3. Examples of the load 4 include a display for a navigation system, a communication device that performs wireless communication with the outside of the vehicle, etc. The load 4 is connected to the generator 1 and the battery 2 via the circuit breaker 11. Also, the load 4 is connected to the battery 13 via the circuit breaker 12. Note that the load 4 receives power supply from the battery 13 when, for example, it cannot receive power supply from the battery 2 due to an abnormality of the battery 2.

[0013] The power supply device 10 is a backup power supply device including the diagnostic device according to the present invention. The power supply device 10 includes circuit breakers 11 and 12, a battery 13, and an ECU 14. Note that the device including the ECU 14 corresponds to the diagnostic device according to the present invention. The circuit breaker 11 switches electrical conduction and interruption between a power supply including the generator 1 and the battery 2 and the load 4, and between a power supply including the generator 1 and the battery 2 and the battery 13. The circuit breaker 11 is electrically connected to the generator 1 and the batteries 2 and 13. Note that the generator 1 and the batteries 2 and 13 correspond to the "power supply unit" of the present invention. Note that the power supply unit may include at least one power supply among the generator 1, the battery 2, and the battery 13.

[0014] The breaker 12 switches between electrical conduction and interruption between the power source including the generator 1 and the battery 2 and the battery 13, and between the load 4 and the battery 13. The breaker 12 is electrically connected to the generator 1 and the batteries 2 and 13. The battery 13 is a backup battery, for example, a lithium-ion secondary battery. The battery 13 can be charged by the generated power of the generator 1 and / or the power of the battery 2. Also, when discharging, the battery 13 can supply power to the load 4, and can supply power to the battery 2 and the load 3.

[0015] The ECU 14 is an electronic control unit for controlling the breakers 11 and 12. The ECU 14 transmits a control command for switching on and off to the semiconductor switches included in the breaker 11 and / or the breaker 12. The ECU 14 detects the voltage of the semiconductor switch. Also, the ECU 14 diagnoses the instruction content to the semiconductor switch indicated by the control command and the abnormal state of the semiconductor switch. The ECU 14 performs an on / off stuck diagnosis as the diagnosis of the abnormal state of the semiconductor switch. The diagnosis method will be described later.

[0016] Next, the configuration of the breaker 11 will be described with reference to FIG. 2. FIG. 2 is a block diagram of the power supply device 10. The breaker 11 has semiconductor switches Q 1 ~Q 4 . The semiconductor switches Q 1 ~Q 4 are transistors such as MOSFETs or IGBTs and are bidirectional switches. The semiconductor switch Q 1 and the semiconductor switch Q 2 are connected in series with the forward directions of the parasitic diodes D 1 included in the semiconductor switch Q 1 and the parasitic diodes D 2 included in the semiconductor switch Q 2 being opposite to each other. The directions in which forward currents flow through the parasitic diodes D 1 , D 2 correspond to the forward directions. For example, the semiconductor switch Q 1 and the semiconductor switch Q 2When it is an N-channel MOSFET, the source terminal of the semiconductor switch Q 1 is connected to the source terminal of the semiconductor switch Q 2 . The drain terminal of the semiconductor switch Q 1 is connected to the generator 1 side, and the drain terminal of the semiconductor switch Q 2 is connected to the battery 13 side. In the following description, the input (In in FIG. 2) of the series circuit 11a of the plurality of semiconductor switches Q 1 , Q 2 corresponds to the generator 1 side, and the output (Out in FIG. 2) of the series circuit 11a corresponds to the load 4 or the battery 13 side. The series circuit 11a is a circuit in which the semiconductor switch Q 1 and the semiconductor switch Q 2 are connected in series. The series circuit 11b is a circuit in which the semiconductor switch Q 3 and the semiconductor switch Q 4 are connected in series. The circuit configuration of the series circuit 11b is the same as that of the series circuit 11a. The series circuit 11a and the series circuit 11b are connected in parallel. Although FIG. 2 does not show the circuit configuration of the circuit breaker 12, the circuit configuration of the circuit breaker 12 may be a configuration in which a plurality of semiconductor switches are connected in series in the same manner as the circuit configuration of the circuit breaker 11. Also, either one of the circuit breakers 11 and 12 may have the same circuit configuration as the series circuit 11a, and the other circuit breaker may be a relay switch (for example, a mechanical relay). In the following description, the semiconductor switches Q 1 ~Q 4 will be described as an example of an N-channel MOSFET, but the semiconductor switches Q 1 ~Q 4 may be P-channel MOSFETs.

[0017] Next, a diagnostic method for the semiconductor switches Q 1 ~Q 4 by the ECU 14 will be described. The ECU 14 uses a sensor to detect the voltage (V 1 ) of the drain terminal of the semiconductor switch Q a1 , the voltage (V 1 ) of the source terminals of the semiconductor switches Q 2 , and the voltage (V b1 ) of the source terminal of the semiconductor switch Q 2The voltage (V c1 ) of the drain terminal is detected respectively. Also, the ECU 14 uses a sensor to detect the voltage (V 3 ) of the drain terminal of the semiconductor switch Q a2 ), the voltage (V 3 ) of the source terminals of the semiconductor switches Q 4 and Q b2 ), and the voltage (V 4 ) of the drain terminal of the semiconductor switch Q c2 respectively. The voltages (V a1 , V c1 ) correspond to the input and output voltages of the series circuit 11a, and the voltages (V a2 , V c2 ) correspond to the input and output voltages of the series circuit 11b. The voltage (V b1 ) is the intermediate voltage of the series circuit 11a and corresponds to the voltage at the connection point connecting the source terminals of the semiconductor switches Q 1 and Q 2 . Also, the voltage (V b2 ) is the intermediate voltage of the series circuit 11b and corresponds to the voltage at the connection point connecting the source terminals of the semiconductor switches Q 3 and Q 4 .

[0018] The ECU 14 determines the semiconductor switches Q 1 to Q 4 to be diagnosed by selecting between the series circuit 11a and the series circuit 11b. When the series circuit 11a is selected, the semiconductor switches Q 1 and Q 2 become the diagnosis targets. When the series circuit 11b is selected, the semiconductor switches Q 3 and Q 4 become the diagnosis targets. In the following description, the diagnosis method when the semiconductor switches Q 1 and Q 2 included in the series circuit 11a are selected as the diagnosis targets will be described.

[0019] The ECU 14 outputs a control command to turn on for the semiconductor switches Q 3 and Q 4 that are not the diagnosis targets. The semiconductor switches Q 3 and Q 4is turned on, and the series circuit 11b becomes conductive. For example, when the circuit breaker 12 is on and the battery 13 discharges to charge the battery 2 or supply power to the load 3, the discharge current of the battery 13 flows through the series circuit 11b.

[0020] The ECU 14 diagnoses the abnormal state of the semiconductor switches with the semiconductor switches Q 1 、Q 2 included in the series circuit 11a as the switches to be diagnosed, while a current is flowing through the series circuit 11b. The ECU 14 detects the voltage (V 1 ) of the drain terminal of the semiconductor switch Q a1 , the voltages (V 1 ) of the source terminals of the semiconductor switches Q 2 、Q b1 , and the voltage (V 3 ) of the drain terminal of the semiconductor switch Q c1 respectively, and diagnoses the abnormal state of the semiconductor switches Q a1 、Q b1 based on the voltages (V c1 、V 1 、V 2 ).

[0021] The ECU 14 outputs a control command to turn on the semiconductor switches Q 1 、Q 2 to be diagnosed. When there is no open fixation in the semiconductor switches Q 1 、Q 2 , the semiconductor switches Q 1 、Q 2 turn on in response to the close instruction. Therefore, the voltage (V 1 ) of the drain terminal of the semiconductor switch Q a1 , the voltages (V 1 ) of the source terminals of the semiconductor switches Q 2 、Q b1 , and the voltage (V 3 ) of the drain terminal of the semiconductor switch Q c1 become substantially the same voltage (V a1 、V c1 =V b1 ). On the other hand, for the semiconductor switch Q 1When open fixation occurs, the voltage (V 1 ) of the drain terminal of semiconductor switch Q a1 becomes higher than the voltage (V b1 ) of the source terminal (V a1 >V b1 ). Similarly, when open fixation occurs in semiconductor switch Q 2 , the voltage (V 2 ) of the drain terminal of semiconductor switch Q c1 becomes higher than the voltage (V b1 ) of the source terminal (V c1 >V b1 ). That is, when the instruction content to semiconductor switches Q 1 and Q 2 is a close instruction, and the voltage (V 1 ) of the drain terminal of semiconductor switch Q a1 or the voltage (V 2 ) of the drain terminal of semiconductor switch Q c1 is higher than the voltage (V 1 ) of the source terminals of semiconductor switches Q 2 and Q b1 , it is determined that open fixation has occurred in semiconductor switches Q 1 and Q 2 .

[0022] Also, ECU14 outputs a control command to turn off the semiconductor switches Q 1 and Q 2 to be diagnosed. When there is no short circuit fixation in semiconductor switches Q 1 and Q 2 , semiconductor switches Q 1 and Q 2 turn off due to an open instruction. Therefore, the voltage (V 1 ) of the drain terminal of semiconductor switch Q a1 and the voltage (V 2 ) of the drain terminal of semiconductor switch Q c1 become higher than the voltage (V 1 ) of the source terminals of semiconductor switches Q 2 and Q b1 (V a1 , V c1 >V b1On the other hand, the semiconductor switch Q 1 If the semiconductor switch Q is stuck closed, 1 The voltage at the drain terminal of a1 ) and semiconductor switch Q 1 The voltage at the source terminal of b1 ) will be almost the same voltage (V a1 =V b1 ). Also, the semiconductor switch Q 2 If the semiconductor switch Q is stuck closed, 2 The voltage at the drain terminal of c1 ) and semiconductor switch Q 2 The voltage at the source terminal of b1 ) will be almost the same voltage (V c1 =V b1 That is, the ECU 14 operates the semiconductor switch Q 1 , Q 2 The instruction to the semiconductor switch Q is an open instruction. 1 The voltage difference between the drain terminal voltage and the source terminal voltage (V a1 -V b1 : Semiconductor switch Q 1 (the drain-source voltage of the 2 The voltage difference between the drain terminal voltage and the source terminal voltage (V c1 -V b1 : Semiconductor switch Q 2 The drain-source voltage of th5 ), the semiconductor switch Q 1 , Q 2 It is determined that a stuck-close occurs in the voltage threshold (V th5 ) is a semiconductor switch Q 1 , Q 2 The threshold value for detecting a closed state between the terminals may be set to zero or a value close to zero.

[0023] In addition, the semiconductor switch Q included in the series circuit 11b 3 , Q 4 When the semiconductor switch Q is selected as the diagnostic target, the ECU 14 1 , Q 2In a manner similar to the diagnostic method, the semiconductor switches Q 3 , Q 4 may be diagnosed for abnormal conditions. Further, when the load currents flowing through loads 3 and 4 are equal to or less than a predetermined current threshold value, the ECU 14 may diagnose the abnormal conditions of the semiconductor switches Q 1 ~Q 4 . For example, the current threshold value is a value equal to or less than the rated current of the semiconductor switches Q 1 ~Q 4 and is preset. When diagnosing the abnormal conditions of the semiconductor switches Q 1 ~Q 4 as described above, since either one of the semiconductor switches Q 1 , Q 2 and the semiconductor switches Q 3 , Q 4 turns off, the load current flows through one of the series circuits 11а and 11b on one side. During normal times when no abnormality diagnosis is performed, since the semiconductor switches Q 1 ~Q 4 are on, the rating of the semiconductor switch may be half of the maximum value of the load current. In this embodiment, since one of the series circuits 11а and 11b on one side turns off for abnormality diagnosis, for example, when performing abnormality diagnosis when the maximum load current is flowing, the rating of the semiconductor switch needs to be adjusted according to the maximum value of the load current. Therefore, the abnormality diagnosis is performed only in a scene where the load current becomes equal to or less than the current threshold value (in the case of a vehicle, a scene where only the AAC power supply is on). As a result, switches with a small rating can be used for the semiconductor switches Q 1 ~Q 4 .

[0024] As described above, in the diagnostic device according to this embodiment, the semiconductor switches included in the circuit breakers 11 and 12 are semiconductor switches Q 1 having a parasitic diode D 1 (corresponding to the "first parasitic diode" of the present invention) and semiconductor switches Q 2 having a parasitic diode D 2 (corresponding to the "second parasitic diode" of the present invention), parasitic diode D 3(Corresponding to the "third parasitic diode" of the present invention) semiconductor switch Q 3 (Corresponding to the "third semiconductor switch" of the present invention) and parasitic diode D 4 (Corresponding to the "fourth parasitic diode" of the present invention) semiconductor switch Q 4 (Corresponding to the "fourth semiconductor switch" of the present invention), and is electrically connected to power supply units such as generator 1, battery 2, 14, etc. Semiconductor switches Q 1 、Q 2 have their forward directions of parasitic diode D 1 and parasitic diode D 2 connected in series with their forward directions opposite to each other. Semiconductor switches Q 3 、Q 4 have their forward directions of parasitic diode D 3 and parasitic diode D 4 connected in series with their forward directions opposite to each other. Also, series circuit 11а and series circuit 11b are connected in parallel. And ECU14 diagnoses the abnormal states of semiconductor switches Q 3 、Q 4 based on the instruction content to the semiconductor switches Q 3 、Q 4 and the voltages of semiconductor switches Q 3 、Q 4 . Thereby, the states of semiconductor switches Q 3 、Q 4 can be diagnosed without interrupting the power supply.

[0025] Incidentally, in a power supply system that requires power supply interruption for diagnosing the sticking of a switch (hereinafter also referred to as a system reference example), the circuit breaker can be interrupted to perform the sticking diagnosis before starting the system. However, the system reference example has a problem that the startup of the system is delayed. Further, in the system reference example, the sticking diagnosis can be performed only in a specific scene where the circuit breaker can be interrupted (for example, in the example of FIG. 1, a scene where it is not necessary to supply power from the generator 1 or the battery 2 to the load 4 and it is not necessary to charge and discharge the battery 13). However, when a power supply system such as the system reference example is provided in a vehicle, the scenes where the sticking diagnosis can be performed are limited, and the diagnosis timing is reduced. The cutoff device according to the present embodiment can increase the diagnosis timing without delaying the startup of the system in order to diagnose the abnormal state of the semiconductor switches Q 1 ~Q 4 In order to diagnose the abnormal state of, the diagnosis timing can be increased without delaying the startup of the system.

[0026] Further, in the present embodiment, the ECU 14 diagnoses the abnormal state of the semiconductor switches Q 1 ~Q 4 by using the semiconductor switches Q 1 ~Q 4 included in the other series circuit 11а or 11b of the series circuits 11а and 11b while current is flowing through one of the series circuits 11а and 11b as the diagnosis target switches. As a result, the abnormal state of the semiconductor switches Q 1 ~Q 4 can be diagnosed without interrupting the power supply.

[0027] Further, in the present embodiment, the ECU 14 detects the input voltage, the output voltage, and the intermediate voltage of the series circuits 11а and 11b, respectively, and based on the instruction content, the input voltage, the output voltage, and the intermediate voltage to the semiconductor switches Q 1 ~Q 4 diagnoses the abnormal state of the semiconductor switches Q 1 ~Q 4 As a result, the abnormal state of the semiconductor switches Q 1~Q 4 can diagnose the abnormal state of

[0028] Also, in this embodiment, the ECU 14 diagnoses the semiconductor switches Q 1 ~Q 4 If the instruction content to is a close instruction and the input voltage or output voltage is greater than the intermediate voltage, it is determined that an open fault has occurred in the semiconductor switches Q 1 ~Q 4 This makes it possible to diagnose the open faults of the semiconductor switches Q 1 ~Q 4 without interrupting the power supply.

[0029] Also, in this embodiment, the ECU 14 diagnoses the semiconductor switches Q 1 ~Q 4 If the instruction content to is an open instruction and the voltage difference between the input voltage and the intermediate voltage or the voltage difference between the output voltage and the intermediate voltage is less than the voltage difference threshold (V th5 ), it is determined that a short fault has occurred in the semiconductor switches Q 1 ~Q 4 This makes it possible to diagnose the short faults of the semiconductor switches Q 1 ~Q 4 without interrupting the power supply.

[0030] <<Second Embodiment>> Next, the second embodiment will be described with reference to the drawings. In this embodiment, the circuit configuration of the circuit breaker 11 and the diagnostic method of the semiconductor switches are different. In the following description, the parts different from the first embodiment will be described, and the parts having the same configuration as the first embodiment will be denoted by the same reference numerals and the description thereof will be omitted. Also, the description of the first embodiment may be appropriately applied to the second embodiment.

[0031] Referring to FIGS. 1 and 2, the diagnostic method of the semiconductor switches Q 1 ~Q 4 by the ECU 14 will be described. In the following description, the semiconductor switches Q 1 , Q 2The diagnostic method when selecting the object to be diagnosed will be described. When the ECU 14 outputs a control command to turn on the semiconductor switches Q 3 and Q 4 , the semiconductor switches Q 3 and Q 4 turn on, and the series circuit 11b becomes conductive.

[0032] The ECU 14 uses a sensor to detect the voltage (V 1 ) at the drain terminal of the semiconductor switch Q a1 , the voltages (V 1 , V 2 ) at the source terminals of the semiconductor switches Q b1 and Q 2 , and the voltage (V c1 ) at the drain terminal of the semiconductor switch Q a1 . The voltages (V c1 ) correspond to the input / output voltages of the series circuit 11a, the voltage (V b1 ) is the intermediate voltage of the series circuit 11a, and corresponds to the voltage at the connection point connecting the source terminals of the semiconductor switches Q 1 and Q 2 . Note that the ECU 14 may detect the voltages (V 1 , V 2 , V a , V b , V c ) using a voltage sensor connected between the drain and source of the semiconductor switches Q

[0033] The ECU 14 outputs a control command to the semiconductor switches Q 1 and Q 2 so that a forward current flows through one of the parasitic diodes D 1 and D 2 . When the voltage at the input (In) of the series circuit 11a is higher than the voltage at the output (Out), when the inside of the series circuit 11a conducts, current flows from the input (In) to the output (Out). The current is input from the generator 1 or the battery 2 into the series circuit 11a. In such a case, the ECU 14 outputs an on control command (close instruction) to the semiconductor switch Q 1Output to and output a control command for off (open instruction) to semiconductor switch Q 2 Thereafter, ECU 14 controls semiconductor switch Q 1 , Q 2 such that the on / off states of semiconductor switches Q 1 are closed and semiconductor switches Q 2 are open, and then detects the voltages of semiconductor switches Q 1 , Q 2 . The voltages of semiconductor switches Q 1 , Q 2 are the drain-source voltages of semiconductor switches Q 1 , Q 2 , and correspond to the voltage differences between voltage (V а1 ) and voltage (V b1 ), and between voltage (V b1 ) and voltage (V c1 ).

[0034] When no open fixation occurs in semiconductor switch Q 1 , semiconductor switch Q 1 turns on according to the close instruction, and thus the drain-source voltage of semiconductor switch Q 1 becomes zero or a voltage close to zero (less than the forward voltage). On the other hand, when open fixation occurs in semiconductor switch Q 1 , even if the control command to semiconductor switch Q 1 is on, semiconductor switch Q 1 remains open, and the drain-source voltage of semiconductor switch Q 1 becomes equal to or higher than the forward voltage. That is, ECU 14 detects the voltage between the terminals of semiconductor switch Q 1 , and when the instruction content to semiconductor switch Q 1 is a close instruction and the detected voltage between the terminals is equal to or lower than a voltage threshold (V th1 ) lower than the forward voltage, it determines that semiconductor switch Q 1 is normal (no open fixation occurs). The voltage threshold (V th1 ) is for semiconductor switch Q 1A threshold value for detecting a closed state between terminals, which may be set to zero or a value close to zero. On the other hand, for the semiconductor switch Q 1 if the instruction content to it is a close instruction and the detected voltage between the terminals is equal to or higher than the forward voltage, the ECU14 determines that 1 an open fixation has occurred in the semiconductor switch Q

[0035] When no close fixation has occurred in the semiconductor switch Q 2 the semiconductor switch Q 2 turns off, so the forward current flows through the parasitic diode D 2 and a voltage drop occurs across the parasitic diode D 2 On the other hand, when a close fixation has occurred in the semiconductor switch Q 2 even if the control command to the semiconductor switch Q 2 is off, the semiconductor switch Q 2 remains in the closed state and no voltage drop occurs across the parasitic diode D 2 The drain-source voltage of the semiconductor switch Q 2 becomes zero or a voltage close to zero (less than the forward voltage). That is, the ECU14 detects the voltage between the terminals of the semiconductor switch Q 2 and when the instruction content to the semiconductor switch Q 2 is an open instruction and the detected voltage between the terminals is equal to or higher than the forward voltage, it determines that the semiconductor switch Q 2 is normal (no close fixation has occurred). On the other hand, when the instruction content to the semiconductor switch Q 2 is an open instruction and the detected voltage between the terminals is equal to or lower than a voltage threshold (V th3 ), the ECU14 determines that a close fixation has occurred in the semiconductor switch Q 2 . The voltage threshold (V th3 ) or lower is a threshold value for detecting a closed state between the terminals of the semiconductor switch Q 2 , which may be set to zero or a value close to zero. In this way, the ECU14 diagnoses the abnormal state of the semiconductor switch Q 2 based on the presence or absence of the forward voltage of the parasitic diode D 2 .

[0036] Note that the ECU 14 may diagnose the closed adhesion of the semiconductor switch Q 1 . When the current is flowing in the series circuit 11a, the ECU 14 outputs a control command (open instruction) to turn off the semiconductor switch Q 1 . When there is no closed adhesion in the semiconductor switch Q 1 , the semiconductor switch Q 1 turns off according to the open instruction. Therefore, the voltage (V 1 ) of the drain terminal of the semiconductor switch Q a1 becomes the output voltage of the generator 1 or the battery 2, and the voltage (V 1 ) of the source terminal of the semiconductor switch Q b1 becomes the output voltage of the battery 13. For example, if the battery 2 is a 14V auxiliary battery and the battery 13 is a 12.3V battery, the drain-source voltage of the semiconductor switch Q 1 is 1.7V. That is, the ECU 14 detects the voltage between the terminals of the semiconductor switch Q 1 . When the instruction content to the semiconductor switch Q 1 is an open instruction and the detected voltage between the terminals is equal to or higher than a predetermined voltage threshold (V th2 ), it is determined that the semiconductor switch Q 1 is normal (no closed adhesion has occurred). The voltage threshold (V th2 ) is set to a value higher than at least zero, and may be set according to the difference between the output voltage of the generator 1 or the battery 2 and the output voltage of the battery 13. On the other hand, when the instruction content to the semiconductor switch Q 1 is an open instruction and the detected voltage between the terminals is zero or a voltage close to zero, the ECU 14 determines that a closed adhesion has occurred in the semiconductor switch Q 1 .

[0037] Also, the ECU 14 may diagnose the open adhesion of the semiconductor switch Q 2 . When a forward current is flowing through the parasitic diode D 2 , the ECU 14 outputs a control command (close instruction) to turn on the semiconductor switch Q 2 . When the semiconductor switch Q2 When there is no open fixation in it, semiconductor switch Q 2 becomes in the closed state, and no voltage drop occurs across parasitic diode D 2 . On the other hand, when there is an open fixation in semiconductor switch Q 2 , a forward current flows through parasitic diode D 2 , and a voltage drop occurs across parasitic diode D 2 . That is, when the instruction content to semiconductor switch Q 2 is a close instruction and the detected voltage across the terminals of semiconductor switch Q 2 is lower than the forward voltage threshold (V th3 ), ECU14 determines that semiconductor switch Q 2 is normal (no open fixation has occurred). On the other hand, when the instruction content to semiconductor switch Q 2 is a close instruction and the detected voltage across the terminals of semiconductor switch Q 2 is equal to or higher than the forward voltage, ECU14 determines that an open fixation has occurred in semiconductor switch Q 2 .

[0038] When the voltage of the output (Out) of series circuit 11а is higher than the voltage of the input (In), when series circuit 11а conducts, current flows from the output (Out) to the input (In). The current is input from battery 13 to series circuit 11а. In such a case, ECU14 outputs an off control command (open instruction) to semiconductor switch Q 1 and outputs an on control command (close instruction) to semiconductor switch Q 2 . Then, ECU14 controls the on / off of semiconductor switches Q 1 , Q 2 to be in the control state indicated by the control command (keeping semiconductor switch Q 1 in the open state and semiconductor switch Q 2 in the closed state), and detects the voltages of semiconductor switches Q 1 , Q 2 .

[0039] Semiconductor switch Q 2When there is no open fault in semiconductor switch Q 2 it turns on according to the close instruction, so the voltage between the drain and source of semiconductor switch Q 2 becomes zero or a voltage close to zero (less than the forward voltage). On the other hand, when there is an open fault in semiconductor switch Q 2 even if the control command to semiconductor switch Q 2 is on, semiconductor switch Q 2 remains in the open state, and the voltage between the drain and source of semiconductor switch Q 2 becomes equal to or higher than the forward voltage. That is, ECU14 detects the voltage between the terminals of semiconductor switch Q 2 , and when the instruction to semiconductor switch Q 2 is a close instruction and the detected voltage between the terminals is lower than the voltage threshold (V th3 ) of the forward voltage, it determines that semiconductor switch Q 2 is normal (no open fault occurs). On the other hand, when the instruction to semiconductor switch Q 2 is a close instruction and the detected voltage between the terminals is equal to or higher than the forward voltage, ECU14 determines that there is an open fault in semiconductor switch Q 2 .

[0040] When there is no short circuit fault in semiconductor switch Q 1 it turns off, so the forward current flows through parasitic diode D 1 and a voltage drop occurs across parasitic diode D 1 . On the other hand, when there is a short circuit fault in semiconductor switch Q 1 even if the control command to semiconductor switch Q 1 is off, semiconductor switch Q 1 remains in the closed state and no voltage drop occurs across parasitic diode D 1 . The voltage between the drain and source of semiconductor switch Q 1 becomes zero or a voltage close to zero (less than the forward voltage). That is, ECU14 detects the voltage between the terminals of semiconductor switch Q 1 and 1 detects the voltage between the terminals of semiconductor switch Q 1When the instruction content to it is an open instruction and the detected voltage between the terminals is equal to or higher than the forward voltage, the semiconductor switch Q 1 is determined to be normal (no closed short has occurred). On the other hand, for the semiconductor switch Q 1 when the instruction content to it is an open instruction and the detected voltage between the terminals is lower than the forward voltage and lower than or equal to the voltage threshold (V th4 ), the ECU14 determines that a closed short has occurred in the semiconductor switch Q 1 . In this way, the ECU14 diagnoses the abnormal state of the semiconductor switch Q 1 based on the presence or absence of the forward voltage of the parasitic diode D 1 .

[0041] Note that the ECU14 may also diagnose a closed short of the semiconductor switch Q 2 . The ECU14 outputs a control command to turn off the semiconductor switch Q 2 while current is flowing in the series circuit 11a. When no closed short has occurred in the semiconductor switch Q 2 , the semiconductor switch Q 2 turns off due to the open instruction, so the voltage between the drain and source of the semiconductor switch Q 2 becomes a value higher than zero. That is, the ECU14 detects the voltage between the terminals of the semiconductor switch Q 2 , and when the instruction content to the semiconductor switch Q 2 is an open instruction and the detected voltage between the terminals is equal to or higher than a predetermined voltage threshold, the semiconductor switch Q 1 is determined to be normal (no closed short has occurred). The voltage threshold only needs to be set to a value higher than at least zero. On the other hand, when the instruction content to the semiconductor switch Q 2 is an open instruction and the detected voltage between the terminals is zero or a voltage close to zero, the ECU14 determines that a closed short has occurred in the semiconductor switch Q 2 .

[0042] Also, the ECU14 may diagnose an open short of the semiconductor switch Q 1 . The ECU14 diagnoses based on the parasitic diode D 1When a forward current is flowing, a control command (close instruction) for turning on the semiconductor switch Q 1 is output. When there is no open fault in the semiconductor switch Q 1 , the semiconductor switch Q 1 becomes in the closed state, and no voltage drop occurs across the parasitic diode D 1 . On the other hand, when an open fault occurs in the semiconductor switch Q 1 , the forward current flows through the parasitic diode D 1 , and a voltage drop occurs across the parasitic diode D 1 . That is, when the instruction content to the semiconductor switch Q 1 is a close instruction and the detected voltage between the terminals of the semiconductor switch Q 1 is lower than the forward voltage threshold (V th3 ), the ECU14 determines that the semiconductor switch Q 1 is normal (no open fault occurs). On the other hand, when the instruction content to the semiconductor switch Q 1 is a close instruction and the detected voltage between the terminals of the semiconductor switch Q 1 is equal to or higher than the forward voltage, the ECU14 determines that an open fault has occurred in the semiconductor switch Q 1 .

[0043] The ECU14 may switch between the semiconductor switch Q 1 to be diagnosed and the semiconductor switch Q 2 during charging and discharging of the battery 13. Charging of the battery 13 occurs when the semiconductor switch Q 1 is on and the semiconductor switch Q 2 is off, and the charging current flows from the generator 1 etc. to the semiconductor switches Q 1 , Q 2 . Discharging of the battery 13 occurs when the semiconductor switch Q 1 is off and the semiconductor switch Q 2 is on, and the discharging current flows from the battery 13 to the semiconductor switches Q 1 , Q 2 . And, as described above, the semiconductor switch Q 1 and the semiconductor switch Q 2When diagnosing the closed fixation, semiconductor switch Q 1 and semiconductor switch Q 2 have different directions of forward current flowing through them. Therefore, with the breaker 12 turned on, the ECU 14 may diagnose the abnormal state of the semiconductor switch Q 2 during the charging of the battery 13. Also, with the breaker 12 turned on, the ECU 14 may diagnose the abnormal state of the semiconductor switch Q 2 during the charging of the battery 13. Thereby, the abnormal diagnosis of the semiconductor switches Q 1 , Q 2 can be performed without interrupting the charge and discharge of the battery 13.

[0044] In addition, when the semiconductor switches Q 3 , Q 4 included in the series circuit 11b are selected as the diagnosis targets, the ECU 14 may diagnose the abnormal states of the semiconductor switches Q 1 , Q 2 in the same way as the diagnosis method of the above semiconductor switches Q 1 , Q 2 .

[0045] As described above, in the diagnostic device according to this embodiment, the ECU 14 transmits a control command so that the forward current flows through one of the parasitic diodes D 1 and parasitic diode D 2 , and diagnoses the abnormal states of the semiconductor switches Q 1 , Q 2 including one of the parasitic diodes based on the presence or absence of the forward voltage of one of the parasitic diodes. The states of the semiconductor switches Q 1 , Q 2 can be diagnosed without interrupting the power supply.

[0046] Also, in this embodiment, the ECU 14 detects the voltage between the terminals of the semiconductor switches Q 1 and parasitic diode D 2 including the other parasitic diode, and the semiconductor switches Q 1 , Q 2 including the other parasitic diode. 1, Q 2 When the instruction to Q is a close instruction and the voltage between the terminals is equal to or higher than the forward voltage, a semiconductor switch Q including other parasitic diodes 1 , Q 2 is determined to have an open short. Thereby, the open short of the semiconductor switch Q 1 , Q 2 can be diagnosed.

[0047] Also, in the present embodiment, the ECU 14 detects the voltage between the terminals of a semiconductor switch Q including one parasitic diode, and when the instruction to the semiconductor switch Q including one parasitic diode 1 , Q 2 is an open instruction and the voltage between the terminals is equal to or lower than a voltage threshold lower than the forward voltage, it is determined that a closed short has occurred in the semiconductor switch Q including one parasitic diode 1 , Q 2 . Thereby, without interrupting the power supply, the closed short of the semiconductor switch Q 1 , Q 2 can be diagnosed. 1 , Q 2

[0048] Also, in the present embodiment, when the semiconductor switch Q 1 is on and the semiconductor switch Q 2 is off, the charging current of the battery 13 flows through the semiconductor switch Q 1 , Q 2 , and when the semiconductor switch Q 1 is off and the semiconductor switch Q 2 is on, the discharge current of the battery 13 flows through the semiconductor switch Q 1 , Q 2 . The ECU 14 diagnoses the abnormal state of the semiconductor switch Q when the charging current flows through the semiconductor switch Q 1 , Q 2 , and diagnoses the abnormal state of the semiconductor switch Q when the discharge current flows through the semiconductor switch Q 2 when the discharge current flows through the semiconductor switch Q 1 , Q 2 , and diagnoses the abnormal state of the semiconductor switch Q 1Diagnose the abnormal state. This enables the diagnosis of the states of semiconductor switches Q 1 , Q 2 without preventing the charge and discharge of the battery 13.

Explanation of Signs

[0049] 1 Generator 2 Battery 3, 4 Load 4 Load 10 Power supply device 11 Circuit breaker 11а, 11b Series circuit 12 Circuit breaker 13, 14 Battery 100 Power supply system Q 1 ~Q 4 Semiconductor switch D 1 ~D 4 Parasitic diode

Claims

1. A diagnostic device for diagnosing the states of a plurality of semiconductor switches, comprising: a controller that transmits a control command for switching on and off the semiconductor switches to the semiconductor switches and detects the voltages of the semiconductor switches; the plurality of semiconductor switches include: a first semiconductor switch having a first parasitic diode, a second semiconductor switch having a second parasitic diode, a third semiconductor switch including a third parasitic diode, and a fourth semiconductor switch including a fourth parasitic diode; electrically connected to a power supply unit; the first semiconductor switch and the second semiconductor switch are connected in series with the forward directions of the first parasitic diode and the second parasitic diode facing opposite to each other; the third semiconductor switch and the fourth semiconductor switch are connected in series with the forward directions of the third parasitic diode and the fourth parasitic diode facing opposite to each other; a first series circuit connecting the first semiconductor switch and the second semiconductor switch in series and a second series circuit connecting the third semiconductor switch and the fourth semiconductor switch in series are connected in parallel; the controller: is a diagnostic device that diagnoses an abnormal state of the semiconductor switch based on the instruction content to the semiconductor switch indicated by the control command and the voltage of the semiconductor switch.

2. The diagnostic device according to claim 1, wherein: the controller: diagnoses an abnormal state of the semiconductor switch with the semiconductor switch included in the other series circuit of the first series circuit and the second series circuit as a diagnostic target switch in a state where a current is flowing through one of the first series circuit and the second series circuit.

3. The diagnostic device according to claim 2, wherein: the controller: detects an input voltage, an output voltage, and an intermediate voltage of the other series circuit, respectively; diagnoses an abnormal state of the diagnostic target switch based on the instruction content to the diagnostic target switch, the input voltage, the output voltage, and the intermediate voltage; the input voltage and the output voltage are terminal voltages of the semiconductor switch; the intermediate voltage is a voltage at a connection point connecting the plurality of semiconductor switches.

4. The diagnostic device according to claim 3, wherein: the controller: A diagnostic device that determines that an open fault has occurred in the switch to be diagnosed when the instruction content for the switch to be diagnosed is a close instruction and the input voltage or the output voltage is greater than the intermediate voltage.

5. The diagnostic device according to claim 3 or 4, wherein the controller determines that a short circuit fault has occurred in the switch to be diagnosed when the instruction content for the switch to be diagnosed is an open instruction and the voltage difference between the input voltage and the intermediate voltage or the voltage difference between the output voltage and the intermediate voltage is less than a voltage difference threshold value.

6. The diagnostic device according to claim 1, wherein the controller sends the control command so that the forward current flows through one of the first parasitic diode and the second parasitic diode, and diagnoses an abnormal state of the semiconductor switch including the one parasitic diode based on the presence or absence of the forward voltage of the one parasitic diode.

7. The diagnostic device according to claim 6, wherein the controller detects the voltage between the terminals of the semiconductor switch including the other parasitic diode among the first parasitic diode and the second parasitic diode, and determines that an open fault has occurred in the semiconductor switch including the other parasitic diode when the instruction content for the semiconductor switch including the other parasitic diode is a close instruction and the voltage between the terminals is equal to or higher than the forward voltage.

8. The diagnostic device according to claim 6, wherein the controller detects the voltage between the terminals of the semiconductor switch including the one parasitic diode, and determines that a short circuit fault has occurred in the semiconductor switch including the one parasitic diode when the instruction content for the semiconductor switch including the one parasitic diode is an open instruction and the voltage between the terminals is equal to or lower than a voltage threshold lower than the forward voltage.

9. The diagnostic device according to claim 8, wherein the power supply unit includes a battery, when the first semiconductor switch is on and the second semiconductor switch is off, the charging current of the battery flows through the plurality of semiconductor switches, when the first semiconductor switch is off and the second semiconductor switch is on, the discharge current of the battery flows through the plurality of semiconductor switches, the controller When the charging current flows through the plurality of semiconductor switches, an abnormal state of the second semiconductor switch is diagnosed, A diagnostic device that diagnoses an abnormal state of the first semiconductor switch when the discharge current flows through the plurality of semiconductor switches. **Claim 10** The diagnostic device according to claim 1, wherein the plurality of semiconductor switches are electrically connected to a load, and the controller diagnoses an abnormal state of the semiconductor switch when a load current flowing through the load is equal to or less than a current threshold value.

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