Short circuit determination circuit

Abstract

The short circuit determination circuit (60) includes a current detection unit (61) that detects a current flowing through the power circuit (P), a voltage detection unit (62) that detects a voltage applied to the power circuit (P), a current abnormality determination unit (63) that determines a current abnormality, a voltage abnormality determination unit (64) that determines a voltage abnormality, and a short circuit determination unit (65) that determines a short circuit in the power circuit (P). A current abnormality determination unit (63) determines a current abnormality on the basis of the current value of the current detected by the current detection unit (61) and a predetermined current threshold value, and a voltage abnormality determination unit (64) determines a voltage abnormality on the basis of the voltage value of the voltage detected by the voltage detection unit (62) and a predetermined voltage threshold value. A short circuit determination unit (65) determines an electrical connection abnormality such as a short circuit or a ground fault (electric leakage) on the basis of the determination result determined by the current abnormality determination unit (63) and the determination result determined by the voltage abnormality determination unit (64).

Description

Technical Field

[0001] The present invention relates to a short - circuit judgment circuit. Background Art

[0002] Conventionally, for example, Patent Document 1 discloses a power supply device capable of quickly cutting off current flowing bidirectionally. The power supply device includes: a power converter that converts the power of a power supply and outputs it to a load; a switch connected between the power supply and the power converter; first and second rectifier circuits connected to a current path from the power supply through the switch to the power converter; and a switch circuit connected in parallel with at least one of the first and second rectifier circuits. The first and second rectifier circuits are circuits that only conduct forward current and are connected in series with the current path with their forward directions opposite to each other.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017 - 028971 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] However, the power supply device described in the above - mentioned Patent Document 1 disconnects the switch circuit in an emergency, thereby quickly cutting off bidirectional current through the first rectifier circuit and the second rectifier circuit. As such an emergency, for example, a short - circuit is considered. Moreover, it is desired that the power supply device quickly and accurately determine the short - circuit.

[0008] Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to provide a short - circuit judgment circuit capable of appropriately judging a short - circuit.

[0009] Means for Solving the Problems

[0010] In order to solve the above problems and achieve the object, the short - circuit judgment circuit according to the present invention is characterized by having: a current detection unit that detects a current flowing through a power circuit; a voltage detection unit that detects a voltage applied to the power circuit; a current abnormality judgment unit that judges current abnormality based on a current value of the current detected by the current detection unit and a predetermined current threshold; a voltage abnormality judgment unit that judges voltage abnormality based on a voltage value of the voltage detected by the voltage detection unit and a predetermined voltage threshold; and a short - circuit judgment unit that judges a short - circuit in the power circuit based on a judgment result judged by the current abnormality judgment unit and a judgment result judged by the voltage abnormality judgment unit.

[0011] Advantages of the Invention

[0012] The short - circuit judgment circuit according to the present invention judges short - circuits based on both current values and voltage values. Therefore, even without providing a filter circuit for removing noise, short - circuits can be judged with high precision. In addition, the short - circuit judgment circuit judges voltage abnormalities based on the detected voltage value and a voltage threshold value. Therefore, compared with, for example, judging voltage abnormalities based on the slope of the change in voltage with respect to time, the time from the occurrence of a short - circuit to the judgment of the short - circuit can be shortened. As a result, the short - circuit judgment circuit can appropriately judge short - circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a circuit diagram showing a configuration example of a power supply device according to an embodiment.

[0014] Figure 2 It is a diagram showing the state transition of a cut - off circuit according to an embodiment.

[0015] Figure 3 It is a diagram showing an operation example of a short - circuit judgment circuit according to an embodiment.

[0016] Figure 4 It is a diagram showing a judgment example of a short - circuit judgment circuit according to an embodiment.

[0017] Figure 5 It is a flowchart showing an operation example of a short - circuit judgment circuit according to an embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] A mode (embodiment) for implementing the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to the content described in the following embodiments. In addition, the constituent elements described below include elements that can be easily conceived by those skilled in the art and substantially identical elements. Furthermore, the configurations described below can be appropriately combined. In addition, various omissions, substitutions, or changes in the structure can be made without departing from the gist of the present invention.

[0019] The power supply device 1 according to the embodiment will be described with reference to the accompanying drawings. The power supply device 1 is mounted on a vehicle, supplies power to a load section of the vehicle, and, for example, judges electrical connection abnormalities such as short - circuits and ground faults (leakage) in the power circuit P and cuts off the power supply path. As Figure 1 shown, the power supply device 1 includes a power circuit P, a main battery 10 as a first electrical device, a sub - battery 20 as a second electrical device, a cut - off circuit 30, a gate driver 40, a gate driver control section 50, and a short - circuit judgment circuit 60. The power circuit P is provided between the main battery 10 and the sub - battery 20.

[0020] The main battery 10 is a rechargeable and power-supplying storage battery, such as a lead storage battery or a lithium-ion battery. The main battery 10 supplies power to the load unit mounted on the vehicle. In addition, the main battery 10 is connected to the auxiliary battery 20 via a cut-off circuit 30 and charges the auxiliary battery 20.

[0021] The auxiliary battery 20 is a rechargeable and power-supplying storage battery, such as a lead storage battery or a lithium-ion battery. The auxiliary battery 20 supplies power to the load unit mounted on the vehicle. In addition, the auxiliary battery 20 is connected to the main battery 10 via the cut-off circuit 30 and is charged with the power supplied from the main battery 10.

[0022] The cut-off circuit 30 is a component that cuts off current, such as a back-to-back circuit. The cut-off circuit 30 includes paired FETs 31a and 31b, paired FETs 31c and 31d, paired FETs 31e and 31f, and resistors R1 to R6. These FETs 31a to 31f are, for example, N-channel MOSFETs. The three pairs of FETs are connected in parallel with each other.

[0023] Specifically, the source terminals of the paired FETs 31a and 31b are connected to each other. The drain terminal of one FET 31a is connected to the main battery 10. The gate terminal of one FET 31a is connected to the gate driver 40 via the resistor R1. The drain terminal of the other FET 31b is connected to the auxiliary battery 20. The gate terminal of the other FET 31b is connected to the gate driver 40 via the resistor R2. The paired FETs 31a and 31b are turned on when a voltage is applied to the gate terminals, enabling bidirectional conduction between the main battery 10 and the auxiliary battery 20. When no voltage is applied to the gate terminals, they are turned off, cutting off the main battery 10 and the auxiliary battery 20 so that bidirectional conduction is not possible.

[0024] The source terminals of the paired FETs 31c and 31d are connected to each other. The drain terminal of one FET 31c is connected to the main battery 10. The gate terminal of one FET 31c is connected to the gate driver 40 via the resistor R3. In addition, the drain terminal of the other FET 31d is connected to the auxiliary battery 20. The gate terminal of the other FET 31d is connected to the gate driver 40 via the resistor R4. The paired FETs 31c and 31d are turned on when a voltage is applied to the gate terminals, enabling bidirectional conduction between the main battery 10 and the auxiliary battery 20. When no voltage is applied to the gate terminals, they are turned off, cutting off the main battery 10 and the auxiliary battery 20 so that bidirectional conduction is not possible.

[0025] The mutual source terminals of the paired FETs 31e and 31f are connected to each other. The drain terminal of one FET 31e is connected to the main battery 10, and the gate terminal of one FET 31e is connected to the gate driver 40 via the resistor R5. Additionally, the drain terminal of the other FET 31f is connected to the auxiliary battery 20, and the gate terminal of the other FET 31f is connected to the gate driver 40 via the resistor R6. The paired FETs 31e and 31f are turned on when a voltage is applied to the gate terminals, enabling bidirectional conduction between the main battery 10 and the auxiliary battery 20. When no voltage is applied to the gate terminals, they are turned off, cutting off the connection between the main battery 10 and the auxiliary battery 20 to prevent bidirectional conduction.

[0026] The gate driver 40 controls the cut-off circuit 30. The gate driver 40 is connected to the gate terminals of the FETs 31a - 31f in the cut-off circuit 30. By applying a voltage to these gate terminals, the FETs 31a - 31f are turned on, and by stopping the voltage application to these gate terminals, the FETs 31a - 31f are turned off.

[0027] The gate driver control unit 50 controls the gate driver 40 based on an instruction from the short-circuit judgment circuit 60. The gate driver control unit 50 is configured to include a transistor 51. The transistor 51 is, for example, an npn-type bipolar transistor. The collector terminal is connected between the gate driver 40 and the gate terminals of the FETs 31a - 31f, the emitter terminal is grounded, and the base terminal is connected to the short-circuit judgment circuit 60. When the transistor 51 is turned on by the voltage applied by the short-circuit judgment circuit 60, a collector current (the current output from the gate driver 40) flows from the collector terminal to the emitter terminal, thereby causing the gate driver 40 to stop applying voltage to each gate terminal. Thus, the transistor 51 can turn off the FETs 31a - 31f. On the other hand, when the transistor 51 is turned off without the voltage being applied by the short-circuit judgment circuit 60, the collector current does not flow from the collector terminal to the emitter terminal, thereby causing the gate driver 40 to continue applying voltage to each gate terminal. Thus, the transistor 51 can maintain the conduction of the FETs 31a - 31f.

[0028] The short-circuit judgment circuit 60 judges electrical connection abnormalities such as short circuits and ground faults. For example, when the short-circuit judgment circuit 60 determines that the main battery 10 has a ground fault, it cuts off the cut-off circuit 30. The short-circuit judgment circuit 60 includes a current detection unit 61, a voltage detection unit 62, a current abnormality judgment unit 63, a voltage abnormality judgment unit 64, and a short-circuit judgment unit 65.

[0029] The current detection unit 61 detects current. In this example, it detects the current flowing between the main battery 10 and the auxiliary battery 20. The current detection unit 61 is configured to include a shunt resistor R7, a current amplifier circuit 611, and resistors R8 - R11.

[0030] The shunt resistor R7 is disposed between the main battery 10 and the sub-battery 20, with one end connected to the main battery 10 and the other end connected to the sub-battery 20.

[0031] The current amplification circuit 611 amplifies the current. The current amplification circuit 611 has a non-inverting input terminal (+), an inverting input terminal (-), and an output terminal. The non-inverting input terminal (+) is connected between the sub-battery 20 and the shunt resistor R7 via the resistor R8. The inverting input terminal (-) is connected between the shunt resistor R7 and the main battery 10 via the resistor R10 and is connected to the output terminal via the resistor R11. The output terminal is connected to the current anomaly determination unit 63. One end of the resistor R9 is connected between the resistor R8 and the non-inverting input terminal (+), and the other end is grounded. The resistor R9 divides the voltage applied to the shunt resistor R7. The amplification factor of the current amplification circuit 611 is determined based on the ratio of the resistance of the resistor R10 to the resistance of the resistor R11. The current amplification circuit 611 outputs the amplified voltage (current value) obtained by amplifying the voltage applied to the shunt resistor R7 to the current anomaly determination unit 63.

[0032] The voltage detection unit 62 detects the voltage. In this example, it detects the voltage applied between the main battery 10 and the sub-battery 20. The voltage detection unit 62 is configured to include a voltage amplification circuit 621 and a resistor R12.

[0033] The voltage amplification circuit 621 is a part that amplifies the voltage. The voltage amplification circuit 621 has a non-inverting input terminal (+), an inverting input terminal (-), and an output terminal. The non-inverting input terminal (+) is connected between the main battery 10 and the sub-battery 20 via the resistor R12. The non-inverting input terminal (+) is connected, for example, between the shunt resistor R7 and the sub-battery 20. The inverting input terminal (-) is connected to the output terminal. The output terminal is connected to the voltage anomaly determination unit 64. The voltage amplification circuit 621 forms a voltage follower, and the amplification factor is 1 times. The voltage amplification circuit 621 outputs the amplified voltage (voltage value) obtained by amplifying the voltage applied between the main battery 10 and the sub-battery 20 to the voltage anomaly determination unit 64. Additionally, depending on the structure of the subsequent voltage comparison circuit 641, a voltage follower may not be required sometimes.

[0034] The current anomaly determination unit 63 determines the anomaly of the current. The current anomaly determination unit 63 determines the current anomaly, for example, based on the current value of the current detected by the current detection unit 61 and a pre-determined current threshold Ith (refer to Figure 3 ). The current anomaly determination unit 63 is configured to include a current comparison circuit 631 and a resistor R13.

[0035] The current comparison circuit 631 is a comparison circuit that compares current values. The current comparison circuit 631 is connected to the current amplification circuit 611 via the resistor R13, compares the current value (amplified voltage) output from the current amplification circuit 611 with the current threshold Ith, and outputs a current anomaly signal (high-level signal) indicating current anomaly to the short-circuit determination unit 65 when the current value is equal to or higher than the current threshold Ith. On the other hand, when the current value output from the current amplification circuit 611 is less than the current threshold Ith, the current comparison circuit 631 outputs a current normal signal (low-level signal) indicating normal current to the short-circuit determination unit 65.

[0036] The voltage anomaly determination unit 64 determines voltage anomalies. The voltage anomaly determination unit 64 determines voltage anomalies, for example, based on the voltage value of the voltage detected by the voltage detection unit 62 and a predetermined voltage threshold Vth (see Figure 3 ). The voltage anomaly determination unit 64 is configured to include a voltage comparison circuit 641 and a resistor R14.

[0037] The voltage comparison circuit 641 is a comparison circuit that compares voltage values. The voltage comparison circuit 641 is connected to the voltage amplification circuit 621 via the resistor R14, compares the voltage value (amplified voltage) output from the voltage amplification circuit 621 with the voltage threshold Vth, and outputs a voltage anomaly signal (high-level signal) indicating voltage anomaly to the short-circuit determination unit 65 when the voltage value is less than the voltage threshold Vth. On the other hand, when the voltage value output from the voltage amplification circuit 621 is equal to or higher than the voltage threshold Vth, the voltage comparison circuit 641 outputs a voltage normal signal (low-level signal) indicating normal voltage to the short-circuit determination unit 65.

[0038] The short-circuit determination unit 65 determines electrical connection anomalies such as short circuits and ground faults. The short-circuit determination unit 65 determines short circuits, for example, based on the determination result determined by the current anomaly determination unit 63 and the determination result determined by the voltage anomaly determination unit 64. The short-circuit determination unit 65 determines a short circuit, for example, when the current anomaly determination unit 63 determines current anomaly and the voltage anomaly determination unit 64 determines voltage anomaly, and cuts off the cut-off circuit 30. The short-circuit determination unit 65 is configured to include an AND circuit 651.

[0039] The AND circuit 651 includes a first input terminal, a second input terminal, and an output terminal. The first input terminal is connected to the current comparison circuit 631, the second input terminal is connected to the voltage comparison circuit 641, and the output terminal is connected to the transistor 51 of the gate driver control unit 50. The AND circuit 651 is a logical product circuit of logical products. When high-level signals are input to the first input terminal and the second input terminal, a cut-off signal is output to the transistor 51. As this cut-off signal, the AND circuit 651 applies a voltage to the transistor 51, for example, to turn on the transistor 51. On the other hand, when a low-level signal is input to at least one of the first input terminal and the second input terminal, the AND circuit 651 does not output a cut-off signal to the transistor 51. The AND circuit 651 turns off the transistor 51, for example, by not applying a voltage to the transistor 51. In this example, when a high-level signal (current abnormal signal) is output from the current comparison circuit 631 and a high-level signal (voltage abnormal signal) is output from the voltage comparison circuit 641, that is, when a ground fault or the like is detected, the AND circuit 651 turns on the transistor 51 to cut off the cut-off circuit 30. On the other hand, when a low-level signal is output from at least one of the current comparison circuit 631 and the voltage comparison circuit 641, that is, when a ground fault or the like is not detected, the AND circuit 651 turns off the transistor 51 to maintain the energized state of the cut-off circuit 30.

[0040] Next, the state transition of the power supply device 1 configured as described above will be described. For example, as shown in Figure 2 When the power is turned on, the cut-off circuit 30 is changed to the cut-off state. And when the power is turned on, when no abnormality such as a ground fault is detected by the short-circuit determination circuit 60 and the wake-up condition for starting the power supply device 1 is satisfied, the cut-off circuit 30 is changed to the energized state. After the power supply device 1 changes the cut-off circuit 30 to the energized state, when an abnormality such as a ground fault is detected by the short-circuit determination circuit 60 and the sleep condition for putting the power supply device 1 on standby is satisfied, the cut-off circuit 30 is changed to the cut-off state. In this way, the state of the power supply device 1 changes from being energized.

[0041] Next, an operation example of the power supply device 1 will be described. In this example, the power supply device 1 assumes a situation where current flows from the main battery 10 to the sub-battery 20 in a normal state. For example, as shown in Figure 3As shown, in the case of a ground fault in the main battery 10 (at time t1), the current flows reversely from the secondary battery 20 to the main battery 10 (at time t2). At this time, when the voltage value output from the voltage amplifier circuit 621 is less than the voltage threshold Vth, the voltage comparison circuit 641 outputs a voltage anomaly signal (high-level signal) indicating voltage anomaly to the AND circuit 651 (between time t1 and time t2). In addition, when the current value output from the current amplifier circuit 611 is equal to or greater than the current threshold Ith, the current comparison circuit 631 outputs a current anomaly signal (high-level signal) indicating current anomaly to the AND circuit 651 (at time t3).

[0042] The AND circuit 651 determines a short circuit (ground fault) and outputs a cut-off signal when a current anomaly signal (high-level signal) is output from the current comparison circuit 631 and a voltage anomaly signal (high-level signal) is output from the voltage comparison circuit 641, causing the transistor 51 of the gate driver control unit 50 to conduct and cutting off the cut-off circuit 30 ( Figure 3 at time t3 Figure 4 and at time t1). The gate driver control unit 50 has a latch circuit (not shown). When a cut-off signal is output from the AND circuit 651, the transistor 51 is continuously conducted through the latch circuit to maintain the cut-off state of the cut-off circuit 30 (from time t3 to time t5) until a current normal signal (low-level signal) is output from the current comparison circuit 631 and a voltage normal signal (low-level signal) is output from the voltage comparison circuit 641. After the cut-off circuit 30 is cut off, the gate driver control unit 50 releases the cut-off of the cut-off circuit 30 to make the cut-off circuit 30 in an energized state (at time t5) when a current normal signal (low-level signal) is output from the current comparison circuit 631 and a voltage normal signal (low-level signal) is output from the voltage comparison circuit 641.

[0043] In addition, when the AND circuit 651 outputs a voltage anomaly signal (high-level signal) from the voltage comparison circuit 641 and a current normal signal (low-level signal) is output from the current comparison circuit 631, although the voltage value is abnormal, the current value is normal, so the cut-off circuit 30 is not cut off (at time t6). In addition, when an overvoltage is applied between the main battery 10 and the secondary battery 20 and an overcurrent flows from the main battery 10 to the secondary battery 20, the current detection unit 61 cannot detect the overcurrent flowing through by using a shielding circuit (not shown). Here, the shielding circuit is a circuit that invalidates (shields) the current detected by the current detection unit 61 when the current flows from the main battery 10 to the secondary battery 20.

[0044] Next, the operation example of the short-circuit judgment circuit 60 will be described with reference to the flowchart. As Figure 5As shown, the short-circuit determination circuit 60 detects the current flowing between the main battery 10 and the secondary battery 20 through the current detection unit 61, and detects the voltage applied between the main battery 10 and the secondary battery 20 through the voltage detection unit 62 (step S1). When the short-circuit determination unit 65 determines that there is a short circuit or the like when it is determined by the current abnormality determination unit 63 that the current is abnormal and it is determined by the voltage abnormality determination unit 64 that the voltage is abnormal (step S2; Yes), the cut-off circuit 30 is cut off (step S3). When the result detected in step S1 by the short-circuit determination unit 65 is that at least one of the current and the voltage is normal (step S2; No), the cut-off circuit 30 is not cut off.

[0045] As described above, the short-circuit determination circuit 60 according to the embodiment includes a current detection unit 61, a voltage detection unit 62, a current abnormality determination unit 63, a voltage abnormality determination unit 64, and a short-circuit determination unit 65. The current detection unit 61 detects the current flowing through the power circuit P. The voltage detection unit 62 detects the voltage applied to the power circuit P. The current abnormality determination unit 63 determines current abnormality based on the current value of the current detected by the current detection unit 61 and a preset current threshold Ith. The voltage abnormality determination unit 64 determines voltage abnormality based on the voltage value of the voltage detected by the voltage detection unit 62 and a preset voltage threshold Vth. The short-circuit determination unit 65 determines electrical connection abnormalities such as short circuits and ground faults (leakage) in the power circuit P based on the determination result determined by the current abnormality determination unit 63 and the determination result determined by the voltage abnormality determination unit 64.

[0046] According to this configuration, the short-circuit determination circuit 60 determines a short circuit or the like based on both the current value and the voltage value. Therefore, even if a filter circuit for removing noise is not provided, malfunction due to minute noise can be suppressed, and a short circuit or the like can be determined with high accuracy. In addition, since the short-circuit determination circuit 60 determines voltage abnormality based on the detected voltage value and the voltage threshold Vth, the time from the occurrence of a short circuit to the determination of the short circuit can be shortened compared with, for example, the case of determining voltage abnormality based on the slope of the change in voltage with respect to time. As a result, the short-circuit determination circuit 60 can appropriately determine a short circuit or the like.

[0047] In the short-circuit determination circuit 60, the power circuit P is provided across the main battery 10 and the secondary battery 20. The secondary battery 20 is connected to the main battery 10 via the cut-off circuit 30. The current detection unit 61 detects the current flowing between the main battery 10 and the secondary battery 20. The voltage detection unit 62 detects the voltage applied between the main battery 10 and the secondary battery 20. The short-circuit determination unit 65 determines that there is a short circuit or the like when it is determined by the current abnormality determination unit 63 that the current is abnormal and it is determined by the voltage abnormality determination unit 64 that the voltage is abnormal, and cuts off the cut-off circuit 30. According to this configuration, the short-circuit determination circuit 60 can appropriately determine a short circuit or the like between the main battery 10 and the secondary battery 20 and perform a cut-off process.

[0048] In the short-circuit determination circuit 60, the current detection unit 61 includes a current amplification circuit 611 that amplifies a current and a shunt resistor R7, the voltage detection unit 62 includes a voltage amplification circuit 621 that amplifies a voltage, the current abnormality determination unit 63 includes a current comparison circuit 631 that compares currents, the voltage abnormality determination unit 64 includes a voltage comparison circuit 641 that compares voltages, and the short-circuit determination unit 65 includes an AND circuit 651 that performs an AND operation. The shunt resistor R7 is provided between the main battery 10 and the sub-battery 20. The current amplification circuit 611 outputs a current value obtained by amplifying the voltage applied to the shunt resistor R7 to the current comparison circuit 631. The voltage amplification circuit 621 outputs a voltage value obtained by amplifying the voltage applied between the main battery 10 and the sub-battery 20 to the voltage comparison circuit 641. When the current value output from the current amplification circuit 611 is equal to or greater than the current threshold Ith, the current comparison circuit 631 outputs a current abnormality signal indicating current abnormality to the AND circuit 651. When the voltage value output from the voltage amplification circuit 621 is less than the voltage threshold Vth, the voltage comparison circuit 641 outputs a voltage abnormality signal indicating voltage abnormality to the AND circuit 651. When a current abnormality signal is output from the current comparison circuit 631 and a voltage abnormality signal is output from the voltage comparison circuit 641, the AND circuit 651 outputs a cut-off signal to the cut-off circuit 30 to cut off the cut-off circuit 30. With this configuration, the short-circuit determination circuit 60 can appropriately determine a short circuit or the like between the main battery 10 and the sub-battery 20 using analog circuits such as the current amplification circuit 611.

[0049] In addition, in the above description, an example in which the short-circuit determination circuit 60 uses analog circuits such as the current amplification circuit 611 has been described, but it is not limited thereto, and for example, digital circuits may be used to configure it.

[0050] An example in which the first electrical device is the main battery 10 and the second electrical device is the sub-battery 20 has been described, but it is not limited thereto, and the first electrical device and the second electrical device may be other electrical devices.

[0051] Figure 1 The power supply device 1 shown is a circuit for detecting a ground fault generated on the main battery 10 side ( Figure 3 in the energizing current: sub-battery → main battery), but it is not limited thereto. For example, if the polarity of the current amplification circuit (OP amplifier) 611 of the current detection unit 61 of the power supply device 1 is reversed, the ground fault detection on the sub-battery 20 side can also be performed. Thus, the power supply device 1 is not limited to the detection direction of the current. In addition, the power supply device 1 shows an example of detecting a ground fault on the main battery 10 side, Figure 3 and the current detection (energizing current: main battery → sub-battery) therein is not an object of detection.

[0052] Description of Reference Numerals

[0053] 10 Main battery (first electrical device)

[0054] 20 Sub-battery (second electrical device)

[0055] 30 Cut-off circuit

[0056] 60 Short-circuit judgment circuit

[0057] 61 Current detection section

[0058] 62 Voltage detection section

[0059] 63 Current abnormality judgment section

[0060] 64 Voltage abnormality judgment section

[0061] 65 Short-circuit judgment section

[0062] 611 Current amplifier circuit

[0063] 621 Voltage amplifier circuit

[0064] 631 Current comparison circuit

[0065] 641 Voltage comparison circuit

[0066] 651 AND circuit

[0067] Ith Current threshold

[0068] Vth Voltage threshold

[0069] R7 Shunt resistor

[0070] P Power circuit

Claims

1. A short circuit judgment circuit, characterized in that: have: a current detection unit configured to detect a current flowing through the power circuit; a voltage detection unit configured to detect a voltage applied to the power circuit; a current abnormality determination unit that determines that the current is abnormal based on a current value of the current detected by the current detection unit and a predetermined current threshold value; a voltage abnormality determination unit configured to determine whether a voltage is abnormal based on a voltage value of a voltage detected by the voltage detection unit and a predetermined voltage threshold; as well as A short circuit determination unit determines a short circuit in the power circuit based on a determination result determined by the current abnormality determination unit and a determination result determined by the voltage abnormality determination unit.

2. The short circuit detection circuit according to claim 1, characterized in that: The power circuit is arranged between the first electrical device and the second electrical device, The first electrical device is a main battery capable of supplying electric power, The second electrical device is a sub-battery capable of supplying electric power, the sub-battery being connected to the main battery via a cutoff circuit, The current detection unit detects a current flowing between the main battery and the sub-battery. The voltage detection unit detects a voltage applied between the main battery and the sub-battery, and The short circuit determination unit determines that there is a short circuit and disconnects the disconnection circuit when the current abnormality determination unit determines that there is a current abnormality and the voltage abnormality determination unit determines that there is a voltage abnormality.

3. The short circuit determination circuit according to claim 2, characterized in that: The current detection unit includes a current amplifying circuit for amplifying the current and a shunt resistor. The voltage detection unit includes a voltage amplification circuit for amplifying the voltage. The current abnormality determination unit includes a current comparison circuit for comparing currents. The voltage abnormality determination unit includes a voltage comparison circuit for comparing voltages. The short circuit determination unit includes an AND circuit that calculates a logical product. The shunt resistor is disposed between the main battery and the sub-battery. The current amplifier circuit outputs a current value obtained by amplifying the voltage applied to the shunt resistor to the current comparison circuit. The voltage amplifier circuit outputs a voltage value obtained by amplifying the voltage applied between the main battery and the sub-battery to the voltage comparison circuit. The current comparison circuit outputs a current abnormality signal indicating current abnormality to the AND circuit when the current value outputted from the current amplifier circuit is equal to or greater than the current threshold value. The voltage comparison circuit outputs a voltage abnormality signal indicating voltage abnormality to the AND circuit when the voltage value outputted from the voltage amplifier circuit is smaller than the voltage threshold value, and When the current abnormality signal is output from the current comparison circuit and the voltage abnormality signal is output from the voltage comparison circuit, the AND circuit outputs a cutoff signal to the cutoff circuit to cut off the cutoff circuit.

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