Short circuit detection circuit

Abstract

To provide a short circuit determination circuit capable of appropriately determining a short circuit.SOLUTION: A short circuit determination circuit 60 has a current detection part 61, a voltage detection part 62, and a short circuit determination part 63. The current detection part 61 detects current flowing through a power circuit P. The voltage detection part 62 detects voltage applied to the power circuit P. The short circuit determination part 63 determines a short circuit in the power circuit P based on a difference between a detection value of the current detected by the current detection part 61 and a detection value of the voltage detected by the voltage detection part 62.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a short circuit determination circuit. [Background technology]

[0002] For example, Patent Document 1 describes a power supply device that can quickly interrupt bidirectional current. This power supply device includes a power converter that converts power from a power supply and outputs it to a load, a switch connected between the power supply and the power converter, a first rectifier circuit and a second rectifier circuit connected to a current path that flows from the power supply to the power converter via the switch, and a switching circuit connected in parallel to at least one of the first rectifier circuit and the second rectifier circuit, where the first rectifier circuit and the second rectifier circuit are circuits that conduct current only in the forward direction and are connected in series to the current path with their forward directions opposite to each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-028971 Summary of the Invention [Problem to be solved by the invention]

[0004] The power supply device described in the above-mentioned Patent Document 1 quickly cuts off bidirectional current through the first rectifier circuit and the second rectifier circuit by turning off the switching circuit in an emergency, but this emergency may be, for example, a short circuit, and it is desirable for the power supply device to quickly and accurately determine whether this short circuit has occurred.

[0005] SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has as its object to provide a short circuit determination circuit that can properly determine whether a short circuit has occurred. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the short circuit determination circuit of the present invention is characterized by comprising a current detection unit that detects the current flowing in a power circuit, a voltage detection unit that detects the voltage applied to the power circuit, and a short circuit determination unit that determines a short circuit in the power circuit based on the difference between the detection value of the current detected by the current detection unit and the detection value of the voltage detected by the voltage detection unit. [Effects of the Invention]

[0007] The short circuit detection circuit according to the present invention detects a short circuit based on a differential voltage value, thereby canceling noise occurring in the current and voltage, and thus accurately detecting a short circuit without the need for a filter circuit to remove noise. Furthermore, because the short circuit detection circuit detects a short circuit based on a differential voltage value, the time from when a short circuit occurs to when a short circuit is detected can be shortened compared to when a voltage abnormality is detected based on the slope of the voltage change over time, for example. As a result, the short circuit detection circuit can accurately detect a short circuit. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a circuit diagram showing an example of the configuration of a power supply device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the difference between current and voltage according to the embodiment. [Figure 3] FIG. 3 is a diagram showing state transitions of the interrupter circuit according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of the operation of the short circuit determination circuit according to the embodiment. [Figure 5] FIG. 5 is a flowchart showing an example of the operation of the short circuit determination circuit according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Modes (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by a person skilled in the art and those that are substantially the same. Furthermore, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configuration can be made within the scope of the gist of the present invention.

[0010] A power supply device 1 according to an embodiment will be described with reference to the drawings. The power supply device 1 is mounted on a vehicle and supplies power to a load of the vehicle, and determines an electrical connection abnormality such as a short circuit or a ground fault (earth leakage) in a power circuit P and cuts off the power supply path. As shown in Fig. 1, 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, an interruption circuit 30, a gate driver 40, a gate driver control unit 50, and a short-circuit determination circuit 60. The power circuit P is provided between the main battery 10 and the sub-battery 20.

[0011] The main battery 10 is a storage battery capable of charging and supplying power, such as a lead-acid battery or a lithium-ion battery. The main battery 10 supplies power to a load mounted on the vehicle. The main battery 10 is also connected to the sub-battery 20 via a breaker circuit 30 and charges the sub-battery 20.

[0012] The sub-battery 20 is a storage battery capable of charging and supplying power, such as a lead-acid battery or a lithium-ion battery. The sub-battery 20 supplies power to a load mounted on the vehicle. The sub-battery 20 is also connected to the main battery 10 via a breaker circuit 30, and is charged with power supplied from the main battery 10.

[0013] The interrupter circuit 30 interrupts current and is, for example, a back-to-back circuit. The interrupter circuit 30 includes a pair of FETs 31a and 31b, a pair of FETs 31c and 31d, a pair of 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.

[0014] Specifically, the source terminals of the pair of FETs 31a, 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 a resistor R1, the drain terminal of the other FET 31b is connected to the sub-battery 20, and the gate terminal of the other FET 31b is connected to the gate driver 40 via a resistor R2. When a voltage is applied to the gate terminals of the pair of FETs 31a, 31b, the pair of FETs 31a, 31b turn ON to allow bidirectional conduction between the main battery 10 and the sub-battery 20, and when no voltage is applied to the gate terminals, the pair of FETs 31a, 31b turn OFF to block bidirectional conduction between the main battery 10 and the sub-battery 20.

[0015] The source terminals of the pair of FETs 31c, 31d are connected to each other, the drain terminal of one FET 31c is connected to the main battery 10, and the gate terminal of the other FET 31c is connected to the gate driver 40 via a resistor R3. The drain terminal of the other FET 31d is connected to the sub-battery 20, and the gate terminal of the other FET 31d is connected to the gate driver 40 via a resistor R4. When a voltage is applied to the gate terminals of the pair of FETs 31c, 31d, they are turned ON to allow bidirectional conduction between the main battery 10 and the sub-battery 20, and when no voltage is applied to the gate terminals, they are turned OFF to block bidirectional conduction between the main battery 10 and the sub-battery 20.

[0016] The source terminals of the pair of FETs 31e, 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 a resistor R5. The drain terminal of the other FET 31f is connected to the sub-battery 20, and the gate terminal of the other FET 31f is connected to the gate driver 40 via a resistor R6. When a voltage is applied to the gate terminals of the pair of FETs 31e, 31f, they are turned ON to allow bidirectional conduction between the main battery 10 and the sub-battery 20, and when no voltage is applied to the gate terminals, they are turned OFF to block bidirectional conduction between the main battery 10 and the sub-battery 20.

[0017] The gate driver 40 controls the interruption circuit 30. The gate driver 40 is connected to the gate terminals of the FETs 31a to 31f of the interruption circuit 30, and turns on the FETs 31a to 31f by applying a voltage to the gate terminals, and turns off the FETs 31a to 31f by stopping the application of the voltage to the gate terminals.

[0018] The gate driver control unit 50 controls the gate driver 40 based on commands from the short-circuit determination circuit 60. The gate driver control unit 50 includes 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 to 31f, the emitter terminal is connected to ground, and the base terminal is connected to the short-circuit determination circuit 60. When the short-circuit determination circuit 60 applies a voltage to the transistor 51 and turns it on, a collector current (a current output from the gate driver 40) flows from the collector terminal to the emitter terminal, thereby stopping the application of voltages to the gate terminals by the gate driver 40. Therefore, the transistor 51 can turn off the FETs 31a to 31f. On the other hand, when the short-circuit determination circuit 60 does not apply a voltage to the transistor 51 and turns it off, no collector current flows from the collector terminal to the emitter terminal, allowing the gate driver 40 to continue applying voltages to the gate terminals. Therefore, the transistor 51 can keep the FETs 31a to 31f ON.

[0019] The short circuit determination circuit 60 determines whether an electrical connection abnormality such as a short circuit or a ground fault has occurred. For example, if the short circuit determination circuit 60 determines that the main battery 10 has a ground fault, it will shut off the interruption circuit 30. The short circuit determination circuit 60 includes a current detection unit 61, a voltage detection unit 62, and a short circuit determination unit 63.

[0020] The current detection unit 61 detects a current, and in this example, detects a current flowing between the main battery 10 and the sub-battery 20. The current detection unit 61 includes a shunt resistor R7, a current amplification circuit 611, and resistors R8 to R11.

[0021] The shunt resistor R7 is provided between the main battery 10 and the sub-battery 20, and has one end connected to the main battery 10 and the other end connected to the sub-battery 20.

[0022] The current amplifier circuit 611 amplifies a current. The current amplifier 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 a resistor R8. The inverting input terminal (-) is connected between the shunt resistor R7 and the main battery 10 via a resistor R10, and is also connected to the output terminal via a resistor R11. The output terminal is connected to the short-circuit 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 connected to ground. The resistor R9 divides the voltage applied to the shunt resistor R7. The gain of the current amplifier circuit 611 is determined based on the ratio of the resistance of the resistor R10 to the resistance of the resistor R11. The current amplifier circuit 611 amplifies the voltage applied to the shunt resistor R7 and outputs the amplified voltage value (detection value) to the short circuit determination unit 63.

[0023] The voltage detection unit 62 detects a voltage, and in this example, detects the voltage applied between the main battery 10 and the sub-battery 20. The voltage detection unit 62 includes a voltage conversion circuit 621 and a resistor R12.

[0024] The voltage conversion circuit 621 converts voltage. The voltage conversion circuit 621 constitutes, for example, a voltage follower circuit and 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 a resistor R12. The non-inverting input terminal (+) is connected, for example, between a 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 short-circuit determination unit 63. The voltage conversion circuit 621 outputs a voltage value (detected value) of the power supply voltage applied between the main battery 10 and the sub-battery 20 to the short-circuit determination unit 63. Note that the voltage follower circuit may not be necessary depending on the configuration of the short-circuit determination unit 63 in the subsequent stage.

[0025] The short-circuit determination unit 63 determines an electrical connection abnormality such as a short circuit or a ground fault. The short-circuit determination unit 63 determines a short circuit in the power circuit P based on the difference between the detected value of the current (voltage value) detected by the current detection unit 61 and the detected value of the voltage (voltage value) detected by the voltage detection unit 62. The short-circuit determination unit 63 determines a short circuit (detects a short circuit) when, for example, the difference between the detected value of the current detected by the current detection unit 61 and the detected value of the voltage detected by the voltage detection unit 62 is equal to or greater than a predetermined threshold Th (see FIG. 4 ), and shuts off the interruption circuit 30 via the gate driver control unit 50. On the other hand, when the difference between the detected value of the current detected by the current detection unit 61 and the detected value of the voltage detected by the voltage detection unit 62 is less than the threshold Th, the short-circuit determination unit 63 does not determine a short circuit (does not detect a short circuit) and does not shut off the interruption circuit 30 via the gate driver control unit 50. The short-circuit determination unit 63 includes a differential amplifier circuit 631 and resistors R13 to R17.

[0026] The differential amplifier circuit 631 amplifies the differential voltage. The differential amplifier circuit 631 has a non-inverting input terminal (+), an inverting input terminal (-), and an output terminal. The non-inverting input terminal (+) is connected to the output terminal of the current amplifier circuit 611 via a resistor R13. The inverting input terminal (-) is connected to the output terminal of the voltage conversion circuit 621 via a resistor R15, and is also connected to the output terminal of the differential amplifier circuit 631 via a resistor R16. The output terminal of the differential amplifier circuit 631 is connected to the gate driver control unit 50 via a resistor R17. One end of the resistor R14 is connected between the resistor R13 and the non-inverting input terminal (+), and the other end is connected to ground. The resistor R14 divides the voltage output from the output terminal of the current amplifier circuit 611. The gain of the differential amplifier circuit 631 is determined based on the ratio between the resistance of the resistor R15 and the resistance of the resistor R16.

[0027] When the differential voltage value obtained by amplifying the difference between the voltage value of the current output by the current amplifier circuit 611 and the voltage value of the voltage output by the voltage conversion circuit 621 is equal to or greater than the threshold Th, i.e., when a ground fault or the like is detected, the differential amplifier circuit 631 outputs a shutdown signal to the interruption circuit 30 via the gate driver control unit 50 to shut down the interruption circuit 30. For example, the differential amplifier circuit 631 applies a predetermined voltage (a differential voltage equal to or greater than the threshold Th) as the shutdown signal from the output terminal to the base terminal of the transistor 51 of the gate driver control unit 50 to turn on the transistor 51 and shut down the interruption circuit 30. On the other hand, when the differential voltage value obtained by amplifying the difference between the voltage value of the current output by the current amplifier circuit 611 and the voltage value of the voltage output by the voltage conversion circuit 621 is less than the threshold Th, i.e., when a ground fault or the like is not detected, the differential amplifier circuit 631 does not output the shutdown signal to the interruption circuit 30 via the gate driver control unit 50 and does not shut down the interruption circuit 30. The differential amplifier circuit 631 turns off the transistor 51 by, for example, not applying a predetermined voltage (a differential voltage equal to or greater than the threshold value Th) from the output terminal to the base terminal of the transistor 51 of the gate driver control unit 50, thereby maintaining the conducting state of the cutoff circuit 30. Note that the differential voltage value is a voltage value obtained by amplifying the difference between the voltage value of the current output from the current amplifier circuit 611 and the voltage value of the voltage output from the voltage conversion circuit 621, and for example, as shown in FIG. 2, even if the current and voltage change, the relative differential voltage value between the voltage value of the current and the voltage value does not change.

[0028] Next, the state transitions of the power supply device 1 configured as described above will be described. For example, as shown in Fig. 3, when the power supply device 1 is turned on, it transitions the interruption circuit 30 to the interruption state. Then, when the power supply device 1 is turned on, if the short-circuit determination circuit 60 does not detect an abnormality such as a ground fault and the wake-up condition for starting up the power supply device 1 is met, it transitions the interruption circuit 30 to the conducting state. After transitioning the interruption circuit 30 to the conducting state, if the short-circuit determination circuit 60 detects an abnormality such as a ground fault and the sleep condition for putting the power supply device 1 into standby is met, it transitions the interruption circuit 30 to the interruption state. In this way, the power supply device 1 transitions states from power-on.

[0029] Next, an example of the operation of the power supply device 1 will be described. In this example, it is assumed that, in the power supply device 1, current flows from the main battery 10 to the sub-battery 20 under normal conditions. For example, as shown in FIG. 4, when a ground fault occurs in the main battery 10 (time t1), the voltage value of the voltage detected by the voltage conversion circuit 621 of the power supply device 1 decreases (time t1). Thereafter, current flows backward from the sub-battery 20 to the main battery 10 (time t2). At this time, the current amplifier circuit 611 detects the current flowing from the sub-battery 20 to the main battery 10, and outputs the voltage value of the detected current to the differential amplifier circuit 631 of the short-circuit determination unit 63 (time t2). When the differential voltage value obtained by amplifying the difference between the voltage value of the current output from the current amplifier circuit 611 and the voltage value of the voltage output from the voltage conversion circuit 621 is equal to or greater than the threshold value Th (time t3), the differential amplifier circuit 631 determines that a short circuit (ground fault) has occurred and outputs a shutdown signal (a differential voltage equal to or greater than the threshold value Th), turning on the transistor 51 of the gate driver control unit 50 and shutting off the shutdown circuit 30 (time t3). The gate driver control unit 50 has a latch circuit (not shown), and when the shutdown signal is output from the differential amplifier circuit 631, the latch circuit keeps the transistor 51 on until a predetermined time has elapsed, maintaining the shutdown state of the shutdown circuit 30 (time limit control: times t3 to t5). At time t4, the voltage value of the current output from the current amplifier circuit 611 becomes zero, and the backflow of current stops. When a predetermined time has elapsed after the shutdown of the shutdown circuit 30, the gate driver control unit 50 releases the shutdown of the shutdown circuit 30 and switches the shutdown circuit 30 to a conducting state (time t5). After the energized state is established, at time t6, the voltage value of the voltage detected by the voltage conversion circuit 621 is restored to the voltage in the energized state.

[0030] Subsequently, when a ground fault occurs again in the main battery 10 and current flows backward from the sub-battery 20 to the main battery 10 (time t7), the differential amplifier circuit 631 determines whether the difference voltage value, obtained by amplifying the difference between the voltage value of the current output from the current amplifier circuit 611 and the voltage value of the voltage output from the voltage conversion circuit 621, is equal to or greater than the threshold value Th. If the difference voltage value is less than the threshold value Th, the differential amplifier circuit 631 does not shut off the cutoff circuit 30 via the gate driver control unit 50 (time t7). Furthermore, when an overcurrent flows from the main battery 10 to the sub-battery 20, the current amplifier circuit 611 does not detect the overcurrent flow by masking it with a mask circuit (not shown) (time t8). As a result, the difference voltage value becomes less than the threshold value Th, and the differential amplifier circuit 631 does not shut off the cutoff circuit 30 via the gate driver control unit 50 (time t8). The mask circuit is a circuit that invalidates (masks) the current detected by the current detection unit 61 when a current flows from the main battery 10 to the sub-battery 20.

[0031] Next, an example of the operation of the short-circuit determination circuit 60 will be described with reference to a flowchart. As shown in Fig. 5, the short-circuit determination circuit 60 detects the current flowing between the main battery 10 and the sub-battery 20 using the current detection unit 61, and detects the voltage applied between the main battery 10 and the sub-battery 20 using the voltage detection unit 62 (step S1). If the difference between the voltage value of the current detected by the current detection unit 61 and the output value of the voltage detected by the voltage detection unit 62 is equal to or greater than the threshold Th (step S2; Yes), the short-circuit determination unit 65 determines that a short circuit has occurred and shuts off the interruption circuit 30 via the gate driver control unit 50 (step S3). On the other hand, if the difference between the voltage value of the current detected by the current detection unit 61 and the output value of the voltage detected by the voltage detection unit 62 is less than the threshold Th (step S2; No), the short-circuit determination unit 65 does not determine that a short circuit has occurred and does not shut off the interruption circuit 30 via the gate driver control unit 50.

[0032] As described above, the short circuit determination circuit 60 according to the embodiment includes the current detection unit 61, the voltage detection unit 62, and the short circuit determination unit 63. 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 short circuit determination unit 63 determines whether a short circuit has occurred in the power circuit P based on the difference between the detected value of the current detected by the current detection unit 61 and the detected value of the voltage detected by the voltage detection unit 62.

[0033] With this configuration, the short circuit determination circuit 60 determines a short circuit based on the differential voltage value, thereby canceling noise that occurs in the current and voltage, and thus accurately determining a short circuit without the need for a filter circuit to remove noise. Furthermore, because the short circuit determination circuit 60 determines a short circuit based on the differential voltage value, the time from when a short circuit occurs to when a short circuit is determined can be shortened compared to when a voltage abnormality is determined based on the slope of the voltage change over time, for example. As a result, the short circuit determination circuit 60 can accurately determine a short circuit.

[0034] In the short-circuit determination circuit 60, the power circuit P is provided between the main battery 10 and the sub-battery 20. The sub-battery 20 is connected to the main battery 10 via the interruption circuit 30. A current detection unit 61 detects the current flowing between the main battery 10 and the sub-battery 20. A voltage detection unit 62 detects the voltage applied between the main battery 10 and the sub-battery 20. A short-circuit determination unit 63 determines that a short circuit has occurred when the difference between the detected value of the current detected by the current detection unit 61 and the detected value of the voltage detected by the voltage detection unit 62 is equal to or greater than a predetermined threshold value Th, and interrupts the interruption circuit 30. With this configuration, the short-circuit determination circuit 60 can properly determine whether a short circuit has occurred between the main battery 10 and the sub-battery 20 and execute interruption processing.

[0035] In the short-circuit determination circuit 60, the current detection unit 61 includes a current amplifier circuit 611 that amplifies the current and a shunt resistor R7. The voltage detection unit 62 includes a voltage conversion circuit 621 that amplifies the voltage. The short-circuit determination unit 63 includes a differential amplifier circuit 631 that amplifies the differential voltage. The shunt resistor R7 is provided between the main battery 10 and the sub-battery 20. The current amplifier circuit 611 amplifies the voltage applied to the shunt resistor R7 and outputs the amplified voltage value to the differential amplifier circuit 631 as a current detection value. The voltage conversion circuit 621 converts the voltage applied between the main battery 10 and the sub-battery 20 and outputs the converted voltage value to the differential amplifier circuit 631 as a voltage detection value. When the amplified differential voltage value between the voltage value of the current output by the current amplifier circuit 611 and the voltage value of the voltage output by the voltage conversion circuit 621 is equal to or greater than a threshold Th, the differential amplifier circuit 631 outputs a shutdown signal to the shutdown circuit 30 to shut off the shutdown circuit 30. With this configuration, the short circuit determination circuit 60 can properly determine whether a short circuit or the like has occurred between the main battery 10 and the sub-battery 20 using analog circuits such as the current amplifier circuit 611.

[0036] In the above description, the short-circuit determination circuit 60 is an example in which analog circuits such as the current amplifier circuit 611 are used, but the invention is not limited to this and may be configured using, for example, digital circuits.

[0037] Although an example has been described in which the first electric device is the main battery 10 and the second electric device is the sub-battery 20, the present invention is not limited to this, and the first electric device and the second electric device may be other electric devices.

[0038] Although the current detection unit 61 has been described as detecting a current value using the shunt resistor R7 and the current amplifier circuit 611, the present invention is not limited to this and may detect a current value based on a magnetic field generated by the current, for example.

[0039] In the above description, the short-circuit determination unit 63 applies a differential voltage equal to or greater than the threshold value Th to turn on the transistor 51 of the gate driver control unit 50 and shut off the shut-off circuit 30 when the differential voltage value obtained by amplifying the difference between the voltage value of the current output by the current amplifier circuit 611 and the voltage value of the voltage output by the voltage conversion circuit 621 is equal to or greater than the threshold value Th, but the present invention is not limited to this. For example, the short-circuit determination unit 63 may compare the differential voltage value obtained by amplifying the difference between the voltage value of the current output by the current amplifier circuit 611 and the voltage value of the voltage output by the voltage conversion circuit 621 with the threshold value Th, determine that a short circuit has occurred when the differential voltage value is equal to or greater than the threshold value Th, and output a shut-off signal to the gate driver control unit 50 to turn on the transistor 51 and shut off the shut-off circuit 30.

[0040] The power supply device 1 shown in FIG. 1 is a circuit for detecting a ground fault occurring on the main battery 10 side (current flowing from the sub-battery to the main battery in FIG. 4), but is not limited to this. For example, if the polarity of the current amplifier circuit (OP amplifier) ​​611 of the current detection unit 61 is reversed, the power supply device 1 can also detect a ground fault on the sub-battery 20 side. In this way, the power supply device 1 is not limited to the direction of current detection. Furthermore, the power supply device 1 shows an example of detecting a ground fault on the main battery 10 side, and does not detect current detection in FIG. 4 (current flowing from the main battery to the sub-battery).

[0041] Although the voltage conversion circuit 621 is configured as a voltage follower circuit in the above example, the voltage conversion circuit 621 is not limited to this. For example, the voltage conversion circuit 621 may be a voltage amplifier circuit that amplifies the voltage by controlling the voltage adjustment of the current amplifier circuit 611 and the differential amplifier circuit 631, or a voltage divider circuit using resistors. [Explanation of symbols]

[0042] 10 Main battery (first electrical device) 20 Sub-battery (second electrical equipment) 30 Breaking Circuit 60 Short circuit detection circuit 61 Current detection section 62 Voltage detection section 63 Short circuit determination unit 611 Current Amplifier Circuit 621 Voltage Conversion Circuit 631 Differential Amplifier Circuit Th threshold R7 Shunt resistor P power circuit

Claims

1. a current detection unit that detects a current flowing in a power circuit and outputs the detected current as a voltage value; a voltage detection unit that detects a voltage applied to the power circuit and outputs the detected voltage as a voltage value; a short circuit determination unit that determines a short circuit in the power circuit based on a difference between a voltage value as a detection value of the current detected by the current detection unit and a voltage value as a detection value of the voltage detected by the voltage detection unit; A short circuit determination circuit comprising:

2. the power circuit is provided between a first electric device and a second electric device, the first electrical device is a main battery capable of supplying power, the second electrical device is a sub-battery connected to the main battery via an interrupter circuit and capable of supplying power; 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; 2. The short circuit determination circuit according to claim 1, wherein the short circuit determination unit determines that a short circuit has occurred and shuts off the shutoff circuit when a difference between a voltage value as a detected value of the current detected by the current detection unit and a voltage value as a detected value of the voltage detected by the voltage detection unit is equal to or greater than a predetermined threshold.

3. the current detection unit includes a current amplification circuit that amplifies the current and a shunt resistor; the voltage detection unit includes a voltage conversion circuit that converts a voltage, the short circuit determination unit includes a differential amplifier circuit that amplifies a differential voltage; The shunt resistor is provided between the main battery and the sub-battery, the current amplifier circuit amplifies the voltage applied to the shunt resistor and outputs the amplified voltage to the differential amplifier circuit as the detection value of the current; the voltage conversion circuit converts a voltage applied between the main battery and the sub-battery and outputs the converted voltage value to the differential amplifier circuit as the detected value of the voltage; 3. The short-circuit determination circuit according to claim 2, wherein the differential amplifier circuit outputs a disconnection signal to the disconnection circuit to disconnect the disconnection circuit when a differential voltage value obtained by amplifying the difference between the voltage value output by the current amplifier circuit and the voltage value output by the voltage conversion circuit is equal to or greater than the threshold value.

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