Power supply control device, inspection method, and computer program product

Abstract

In the power supply control device (10), the power supply is controlled by switching the FET (20) to be on or off. In the case where the current flowing through the FET (20) rises, the risen current flows through the resistance circuit (25). The drive circuit (23) notifies in the case where the voltage between both ends of the resistance circuit (25) is a voltage equal to or higher than a reference voltage. The microcomputer (27) instructs the application circuit (26) to apply a voltage to the resistance circuit (25). Thereby, the application circuit (26) applies a voltage equal to or higher than the reference voltage to the resistance circuit (25). The microcomputer (27) determines whether the drive circuit (23) notifies after instructing the application circuit (26) to apply a voltage to the resistance circuit (25).

Description

Technical Field

[0001] This disclosure relates to power supply control devices, inspection methods, and computer programs.

[0002] This application claims priority based on Japanese Application No. 2020-071837, filed on April 13, 2020, and invokes all the contents of that Japanese application. Background Technology

[0003] Patent Document 1 discloses a power supply control device for a vehicle that controls the supply of power from a battery to a load. In this power supply control device, a switch is arranged in the current path of the current flowing from the battery to the load. By switching the switch to be on or off, the supply of power from the battery to the load is controlled.

[0004] In the power supply control device described in Patent Document 1, when the current flowing through the switch increases, the increased current flows through a resistor circuit. The resistor circuit includes a resistor. When the voltage across the resistor circuit is higher than a predetermined voltage, it is assumed that the current flowing through the current path is large, and the switch is switched off. This prevents overcurrent from flowing through the current path.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2017-103963 Summary of the Invention

[0008] One aspect of this disclosure relates to a power supply control device that controls power supply by switching a switch to be on or off. The power supply control device includes a resistor circuit through which a current increases when the current flowing through the switch increases; a notification circuit that notifies the user when the voltage between the two ends of the resistor circuit is a predetermined voltage or higher; an application circuit that applies the predetermined voltage or higher to the resistor circuit; and a processing unit that performs processing. The processing unit instructs the application circuit to apply a voltage to the resistor circuit, and after instructing the application circuit to apply a voltage, determines whether the notification circuit should provide notification.

[0009] One aspect of this disclosure relates to an inspection method that inspects a notification circuit that provides notification when the voltage between the two ends of a resistor circuit through which the current flowing via a switch increases is above a predetermined voltage. The inspection method is performed by a computer with the following steps: instructing the application of the voltage above the predetermined voltage to the resistor circuit; and determining whether the notification circuit provides notification after instructing the application of the voltage to the resistor circuit.

[0010] One aspect of this disclosure relates to a computer program for causing a computer to check a notification circuit that notifies the computer when the voltage between the two ends of a resistor circuit through which the current flowing via the switch increases is a voltage greater than a predetermined voltage. The computer program causes the computer to perform the following steps: instructing the computer to apply a voltage greater than the predetermined voltage to the resistor circuit; and determining, after instructing the computer to apply a voltage to the resistor circuit, whether the notification circuit notifies the computer.

[0011] Furthermore, this disclosure can be implemented not only as a power supply control device having such a characteristic processing unit, but also as a method for checking steps of the aforementioned characteristic processing unit, or as a computer program for causing a computer to execute the aforementioned steps. Additionally, this disclosure can be implemented as a semiconductor integrated circuit that implements part or all of the power supply control device, or as a power supply system including the power supply control device. Attached Figure Description

[0012] Figure 1 This is a block diagram showing the main structural components of the power supply system in Embodiment 1.

[0013] Figure 2 This is a block diagram showing the main structure of the drive circuit.

[0014] Figure 3 This is the circuit diagram of a latch circuit.

[0015] Figure 4 This is a block diagram showing the main structural components of a microcomputer.

[0016] Figure 5 This is an explanatory diagram showing the range of voltages at both ends of the A / D converter.

[0017] Figure 6 This is a flowchart illustrating the sequence of conduction processing.

[0018] Figure 7 This is a flowchart showing the sequence of disconnection processes.

[0019] Figure 8 It is a timing diagram used to illustrate the operation of the power supply control device.

[0020] Figure 9 This is a block diagram showing the main structural components of the power supply system in Embodiment 2. Detailed Implementation

[0021] [The problem this disclosure aims to solve]

[0022] In the conventional power supply control device described in Patent Document 1, when the voltage across the resistor circuit is above a predetermined voltage, the switch is switched to open, and a notification circuit is activated. If the notification circuit fails to activate properly, there is a high probability that the switch will not properly open. If the switch does not properly open, it is impossible to prevent overcurrent from flowing through the current path.

[0023] In recent years, there has been ongoing development of computer-driven autonomous vehicles. Since these vehicles are not driven by humans, a structure that reliably prevents the flow of overcurrent is required.

[0024] Therefore, the objective is to provide a power supply control device, a checking method, and a computer program for a notification circuit that can notify the user when the voltage between the two ends of a resistive circuit is above a predetermined voltage.

[0025] [The Effects of This Disclosure]

[0026] According to this disclosure, there is a notification circuit that can notify when the voltage between the two ends of a resistor circuit is above a predetermined voltage.

[0027] [Description of embodiments of this disclosure]

[0028] First, embodiments of this disclosure will be described by way of example. At least some of the embodiments described below may be combined arbitrarily.

[0029] (1) One aspect of the power supply control device disclosed herein controls power supply by switching a switch to be on or off. The power supply control device includes a resistor circuit through which a current increases when the current flowing through the switch increases; a notification circuit that notifies the user when the voltage between the two ends of the resistor circuit is a predetermined voltage or higher; an application circuit that applies the predetermined voltage or higher to the resistor circuit; and a processing unit that performs processing. The processing unit instructs the application circuit to apply a voltage to the resistor circuit and, after instructing the application circuit to apply a voltage, determines whether the notification circuit should provide notification.

[0030] (2) In a power supply control device according to one aspect of the present disclosure, the notification circuit provides notification by applying a voltage above the predetermined voltage to the resistor circuit. After instructing the application circuit to apply the voltage, the processing unit instructs the application circuit to stop applying the voltage. After instructing the application circuit to stop applying the voltage, the processing unit determines whether the notification circuit provides notification based on the voltage between the two ends of the resistor circuit.

[0031] (3) A power supply control device according to one aspect of the present disclosure includes a switching unit that switches the switch to open when the voltage between the two ends of the resistor circuit is a voltage greater than the predetermined voltage, and the processing unit instructs the application circuit to apply voltage to the resistor circuit when a disconnect signal instructing the switch to open is input.

[0032] (4) In a power supply control device according to one aspect of the present disclosure, when the processing unit determines that the notification circuit is to provide the notification, it instructs the notification circuit to stop applying voltage, and after instructing the notification circuit to stop applying voltage, it determines whether the voltage between the two ends of the resistor circuit is lower than the predetermined voltage.

[0033] (5) One aspect of the present disclosure relates to an inspection method that inspects a notification circuit that provides notification when the voltage between the two ends of a resistor circuit through which the current flowing via the switch increases is a voltage greater than or equal to a predetermined voltage. The inspection method is performed by a computer in the following steps: instructing the application of a voltage greater than or equal to the predetermined voltage to the resistor circuit; and after instructing the application of a voltage to the resistor circuit, determining whether the notification circuit provides notification.

[0034] (6) A computer program according to one aspect of the present disclosure is used to enable a computer to check a notification circuit that notifies when the voltage between the two ends of a resistor circuit through which the current flowing through the switch increases is a voltage greater than a predetermined voltage. The computer program enables the computer to perform the following steps: instructing the application of the voltage greater than the predetermined voltage to the resistor circuit; and after instructing the application of the voltage to the resistor circuit, determining whether the notification circuit notifies.

[0035] In the power supply control device, inspection method, and computer program described above, a voltage exceeding a predetermined voltage is applied to the resistive circuit, and it is determined whether the notification circuit should issue a notification. Thus, the notification circuit is inspected.

[0036] In the power supply control device described above, after the application circuit stops applying voltage, it is determined whether the notification circuit should issue a notification based on whether the voltage between the two ends of the resistor circuit is above a predetermined voltage. If the voltage between the two ends of the resistor circuit is above the predetermined voltage, it is determined that a notification has been issued. If the voltage between the two ends of the resistor circuit is below the predetermined voltage, it is determined that the notification circuit has not issued a notification.

[0037] In the power supply control device described above, when the current flowing through the switch increases, the voltage across the resistor circuit increases. When the voltage across the resistor circuit is higher than a predetermined voltage, the switch is switched to open. Therefore, overcurrent is prevented from flowing through the switch. Furthermore, at the time the disconnect signal is input, i.e., the time when the switch is required to switch to open, a notification circuit is checked. If no fault occurs in the device, the switch is switched to open when the application circuit applies a voltage higher than the predetermined voltage to the resistor circuit.

[0038] In the power supply control device described above, after the notification circuit stops applying voltage to the resistor circuit, it is determined whether the voltage between the two ends of the resistor circuit is lower than a predetermined voltage. This confirms that the voltage between the two ends of the resistor circuit has returned to a level lower than the predetermined voltage.

[0039] [Details of the embodiments disclosed herein]

[0040] Hereinafter, specific examples of power supply systems according to embodiments of the present disclosure will be described with reference to the accompanying drawings. Furthermore, the present invention is not limited to these examples, but is indicated by the claims, which are intended to encompass all modifications within the meaning and scope equivalent to the claims.

[0041] (Implementation Method 1)

[0042] <Structure of Power Supply System>

[0043] Figure 1 This is a block diagram showing the main structural components of the power system 1 in Embodiment 1. The power system 1 is suitably mounted in a vehicle and includes a power supply control device 10, a DC power supply 11, and a load 12. The DC power supply 11 is, for example, a battery. The load 12 is an electrical device mounted in the vehicle.

[0044] The power supply control device 10 has an N-channel FET (Field Effect Transistor) 20 that functions as a switch and a shunt resistor 21. The positive terminal of the DC power supply 11 is connected to the drain of the FET 20. The source of the FET 20 is connected to one end of the shunt resistor 21. The other end of the shunt resistor 21 is connected to one end of the load 12. The negative terminal of the DC power supply 11 and the other end of the load 12 are grounded.

[0045] When FET20 is turned on, the resistance between its drain and source is sufficiently small, allowing current to flow through both terminals. When FET20 is turned off, the resistance between its drain and source is sufficiently large, preventing current from flowing through either terminal.

[0046] The power supply control device 10 switches FET 20 to either on or off. When FET 20 is on, current flows sequentially from the positive terminal of DC power supply 11 through FET 20, shunt resistor 21, load 12, and the negative terminal of DC power supply 11, supplying power to load 12. During the period when power is supplied to load 12, load 12 operates. When FET 20 is off, the power supply to load 12 stops, and load 12 stops operating.

[0047] As described above, the power supply control device 10 controls the power supply from the DC power supply 11 to the load 12 by switching the FET 20 to be on or off.

[0048] An on signal instructing FET20 to switch on and an off signal instructing FET20 to switch off are input to the power supply control device 10. When an on signal is input, the power supply control device 10 switches FET20 to on. When an off signal is input, the power supply control device 10 switches FET20 to off.

[0049] <Structure of Power Supply Control Device 10>

[0050] In addition to FET 20 and shunt resistor 21, power supply control device 10 also includes regulator 22, drive circuit 23, current output circuit 24, resistor circuit 25, application circuit 26, and microcomputer (hereinafter referred to as microcomputer) 27. Resistor circuit 25 has a detection resistor 30.

[0051] The drain and gate of FET20 are connected to regulator 22 and drive circuit 23, respectively. One end and the other end of shunt resistor 21 are each connected to current output circuit 24. Current output circuit 24 is further connected to one end of sensing resistor 30 of resistor circuit 25. The other end of sensing resistor 30 is grounded. One end and the other end of sensing resistor 30 correspond to one end and the other end of resistor circuit 25, respectively. The connection node between current output circuit 24 and sensing resistor 30 is connected to drive circuit 23, application circuit 26, and microcomputer 27. Regulator 22, drive circuit 23, and application circuit 26 are further connected to microcomputer 27. Microcomputer 27 is also grounded.

[0052] FET20 is turned on when the gate voltage of FET20 (with a reference potential of ground) is above a constant turn-on voltage. FET20 is turned off when the gate voltage of FET20 (with a reference potential of ground) is below a constant turn-off voltage. The turn-on voltage exceeds the turn-off voltage. The turn-off voltage is a positive voltage. The drive circuit 23 switches FET20 on by raising the gate voltage of FET20 (with a reference potential of ground) to a voltage above the turn-on voltage. The drive circuit 23 switches FET20 off by lowering the gate voltage of FET20 (with a reference potential of ground) to a voltage below the turn-off voltage.

[0053] As described above, when FET20 is turned on, current flows sequentially through FET20 and shunt resistor 21. Current output circuit 24 outputs a current proportional to the current flowing through shunt resistor 21 to the detection resistor 30 of resistor circuit 25. The current output by current output circuit 24 flows through the detection resistor 30 of resistor circuit 25. Hereinafter, the current flowing through FET20 will be referred to as the switching current. The current flowing through shunt resistor 21 is substantially the same as the switching current. Therefore, the current output from current output circuit 24 is substantially the same as (switching current) / (predetermined number), increasing as the switching current increases. The predetermined number is a positive real number, for example, 4000.

[0054] The current output from the current output circuit 24 flows through the sensing resistor 30 of the resistor circuit 25. The voltage across the sensing resistor 30, i.e., the resistor circuit 25, is represented by (the current output from the current output circuit 24) * (the resistance value of the sensing resistor 30). Hereinafter, the voltage across the resistor circuit 25 will be described as the voltage across both terminals. As described above, the current output from the current output circuit 24 is substantially the same as (switching current) / (predetermined number). Therefore, the voltage across the resistor circuit 25 is substantially the same as (switching current) * (resistance value of the sensing resistor 30) / (predetermined number), and the higher the switching current, the higher the voltage.

[0055] The voltage at the connection node between the current output circuit 24 and the sensing resistor 30 is output to the drive circuit 23 and the microcomputer 27. Here, the reference potential of the voltage at the connection node is the ground potential. Therefore, the voltage at the connection node between the current output circuit 24 and the sensing resistor 30 is the voltage across the resistor circuit 25.

[0056] The regulator 22 generates a constant voltage Vc by reducing the output voltage of the DC power supply 11, whose reference potential is ground, and applies the generated constant voltage Vc to the microcomputer 27. As a result, current flows sequentially from the positive terminal of the DC power supply 11 through the regulator 22, the microcomputer 27, and the negative terminal of the DC power supply 11, supplying power to the microcomputer 27. The constant voltage Vc is 5.0V or 3.3V, etc.

[0057] Microcomputer 27 outputs a voltage to drive circuit 23. The reference potential of the output voltage of microcomputer 27 is ground potential. Microcomputer 27 switches the output voltage to drive circuit 23 to a high-level voltage or a low-level voltage. The high-level voltage is higher than the low-level voltage. The high-level voltage is, for example, consistent with a constant voltage Vc. The low-level voltage is, for example, zero V. Drive circuit 23 switches FET 20 to be turned on or off based on the output voltage of microcomputer 27 and the voltage across resistor circuit 25.

[0058] When the voltage across resistor circuit 25 is lower than the constant reference voltage, and the microcomputer 27 switches the output voltage from a low level to a high level, the drive circuit 23 switches FET 20 to conduct. When the voltage across resistor circuit 25 is lower than the reference voltage, and the microcomputer 27 switches the output voltage from a high level to a low level, the drive circuit 23 switches FET 20 to deactivate.

[0059] When the output voltage of the microcomputer 27 is at a high level and the voltage across the resistor circuit 25 is above the reference voltage, the drive circuit 23 switches the FET 20 off and applies voltage to the resistor circuit 25. The voltage applied to the resistor circuit 25 by the drive circuit 23 will be described below as the notification voltage. The notification voltage is a voltage above the reference voltage. The reference potential for the notification voltage is ground potential.

[0060] The drive circuit 23 informs the microcomputer 27 that the voltage across the resistor circuit 25 is above the reference voltage by applying a notification voltage to the resistor circuit 25. When the microcomputer 27 switches the output voltage from a high level to a low level, the drive circuit 23 stops applying the notification voltage to the resistor circuit 25 while keeping the FET 20 off.

[0061] When the output voltage of the microcomputer 27 is a low level voltage, the drive circuit 23 will keep the FET 20 off regardless of the voltage across the resistor circuit 25.

[0062] The application circuit 26 applies voltage to the resistor circuit 25 and stops applying voltage to the resistor circuit 25 according to the instructions of the microcomputer 27. The voltage applied to the resistor circuit 25 by the application circuit 26 is recorded as the applied voltage. The applied voltage is a voltage above a reference voltage. The reference potential of the applied voltage is the ground potential.

[0063] A turn-on signal and a turn-off signal are input to the microcomputer 27. When a turn-on signal is input, the microcomputer 27 switches the output voltage to the drive circuit 23 from a low level voltage to a high level voltage. This causes the drive circuit 23 to turn on the FET 20. As described above, when the FET 20 is on, current flows sequentially through the FET 20, the shunt resistor 21, and the load 12, supplying power to the load 12. The current output circuit 24 outputs a current proportional to the current flowing through the shunt resistor 21 to the detection resistor 30 of the resistor circuit 25.

[0064] When a disconnect signal is input, the microcomputer 27 instructs the application circuit 26 to apply a voltage. Consequently, the application circuit 26 applies a voltage higher than the reference voltage to the voltage across the resistor circuit. As a result, the voltage across the resistor circuit 25 becomes higher than the reference voltage, so the drive circuit 23 switches the FET 20 to disconnect. As described above, the drive circuit 23 provides notification by applying a notification voltage to the resistor circuit 25 when the voltage across the resistor circuit 25 is higher than the reference voltage.

[0065] After instructing the application circuit 26 to apply voltage, the microcomputer 27 instructs the application circuit 26 to stop applying voltage. Thus, the application circuit 26 stops applying voltages higher than the reference voltage. When no fault occurs in the power supply control device 10, the drive circuit 23 continues to apply voltages higher than the reference voltage after the application circuit 26 stops applying voltage. After instructing the application circuit 26 to stop applying voltage, the microcomputer 27 determines whether the drive circuit 23 has provided notification based on the voltage across the resistor circuit 25. Thus, the microcomputer 27 checks the notification function of the drive circuit 23.

[0066] After determining whether the drive circuit 23 has provided notification, the microcomputer 27 switches its output voltage to a low level. This stops the drive circuit 23 from applying the notification voltage to the resistor circuit 25. After switching the output voltage to a low level, the microcomputer 27 determines whether the voltage across the resistor circuit 25 is lower than a reference voltage. This allows the microcomputer 27 to confirm that the voltage across the resistor circuit 25 has returned to a level lower than the reference voltage.

[0067] <Structure of Application Circuit 26>

[0068] The application circuit 26 includes a transistor 40, a diode 41, and circuit resistors 42 and 43. Transistor 40 is a PNP bipolar transistor that functions as a switch. When transistor 40 is turned on, the resistance between its emitter and collector is sufficiently small, allowing current to flow through both electrodes. When transistor 40 is turned off, the resistance between its emitter and collector is sufficiently large, preventing current from flowing through either electrode.

[0069] The cathode of diode 41 is connected to the connection node between current output circuit 24 and sensing resistor 30. The anode of diode 41 is connected to the collector of transistor 40. Circuit resistor 42 is connected between the emitter and base of transistor 40. One end of circuit resistor 43 is connected to the base of transistor 40. The other end of circuit resistor 43 is connected to microcomputer 27. A constant voltage Vc is applied to the emitter of transistor 40, similarly to microcomputer 27.

[0070] Furthermore, the structure of applying a constant voltage Vc to the emitter of transistor 40 can also be achieved by applying a constant voltage Vc through regulator 22.

[0071] In transistor 40, transistor 40 is turned on when the base voltage, which is the reference potential (the emitter potential), is lower than a constant voltage threshold. The voltage threshold is a negative voltage. In transistor 40, transistor 40 is turned off when the base voltage, which is the reference potential (the emitter potential), is higher than the voltage threshold.

[0072] The microprocessor 27 adjusts the voltage at the other end of the circuit resistor 43 of the application circuit 26. The voltage at the other end of the circuit resistor 43 will be referred to as the resistor voltage. The reference potential of the resistor voltage is ground potential. The microprocessor 27 switches the transistor 40 to be on or off. The microprocessor 27 lowers the resistor voltage to a sufficiently low voltage, such as zero V. As a result, current flows sequentially from the emitter of the transistor 40 through circuit resistors 42 and 43, generating a voltage drop at circuit resistor 42. At this time, because the current flowing through circuit resistor 42 is large, the voltage at the base of the transistor 40, where the reference potential is the emitter potential, becomes below the voltage threshold. As a result, the transistor 40 switches to be on.

[0073] Microprocessor 27 raises the resistor voltage to a sufficiently high voltage, such as a constant voltage Vc. Consequently, the current flowing through circuit resistor 42 drops to zero A or a value close to zero A. At this point, in transistor 40, the base voltage, which is the emitter potential, rises to zero V or a value close to zero V, becoming a voltage above the voltage threshold. Therefore, transistor 40 switches off.

[0074] As described above, the microprocessor 27 switches the transistor 40 to be on or off.

[0075] When transistor 40 switches from off to on, current flows sequentially through transistor 40, diode 41, and resistor circuit 25, and application circuit 26 applies voltage to resistor circuit 25. The magnitude of the voltage drop generated at diode 41 when current flows sequentially through the anode and cathode in diode 41 is recorded as the forward voltage. The applied voltage applied by application circuit 26 to resistor circuit 25 is represented by (constant voltage Vc) - (forward voltage). As mentioned above, the applied voltage is above the reference voltage.

[0076] When transistor 40 switches from on to off, the flow of current through transistor 40 and diode 41 stops, and the application circuit 26 stops applying voltage to the resistor circuit 25.

[0077] As described above, the microprocessor 27 instructs the application circuit 26 to apply voltage to the resistor circuit 25 by causing the resistor voltage to drop to a sufficiently low voltage. Consequently, the transistor 40 switches to conduct, and the application circuit 26 applies a voltage above the reference voltage to the resistor circuit 25. The microprocessor 27 instructs the application circuit 26 to stop applying voltage to the resistor circuit 25 by causing the resistor voltage to rise to a sufficiently high voltage. Consequently, the transistor 40 switches to deactivation, and the application circuit 26 stops applying voltage to the resistor circuit 25.

[0078] <Structure of drive circuit 23>

[0079] Figure 2 This is a block diagram showing the main structure of the drive circuit 23. The drive circuit 23 includes a drive section 50, a comparator 51, and a latch circuit 52. The comparator 51 has a positive terminal, a negative terminal, and an output terminal. The gate of the FET 20 is connected to the drive section 50. The drive section 50 is further connected to the microcomputer 27. The connection node between the drive section 50 and the microcomputer 27 is connected to the latch circuit 52. The output terminal of the comparator 51 is connected to the drive section 50 and the latch circuit 52. The negative terminal of the comparator 51 and the latch circuit 52 are connected to the connection node between the current output circuit 24 and the resistor circuit 25. The aforementioned reference voltage Vr is applied to the positive terminal of the comparator 51. The reference voltage Vr is generated, for example, by reducing the output voltage of the DC power supply 11 through a regulator (not shown).

[0080] The drive unit 50 switches FET 20 to be on or off by adjusting the voltage of the gate of FET 20, whose reference potential is ground, as described above. Comparator 51 outputs a voltage from its output terminal to the drive unit 50 and the latch circuit 52. The reference potential of the output voltage of comparator 51 is ground. Comparator 51 switches the output voltage to a high-level voltage or a low-level voltage.

[0081] When the voltage across resistor circuit 25 is lower than the reference voltage Vr, comparator 51 outputs a high-level voltage to driver unit 50 and latch circuit 52. When the voltage across resistor circuit 25 is higher than the reference voltage Vr, comparator 51 switches the output voltage from high to low. When the voltage across resistor circuit 25 is lower than the reference voltage Vr, comparator 51 switches the output voltage from low to high. The reference voltage Vr corresponds to a predetermined voltage.

[0082] The output voltage of the microcomputer 27 is output to the drive unit 50 and the latch circuit 52. When the output voltage of the comparator 51 switches from a high level to a low level while the output voltage of the microcomputer 27 is high, the latch circuit 52 applies a notification voltage to the resistor circuit 25. This provides notification. As described above, the notification voltage is a voltage greater than or equal to the reference voltage Vr. The latch circuit 52 functions as a notification circuit. During the period when the latch circuit 52 applies the notification voltage to the resistor circuit 25, the output voltage of the comparator 51 remains fixed at a low level. When the output voltage of the microcomputer 27 switches from a high level to a low level, the latch circuit 52 stops applying the notification voltage to the resistor circuit 25. The latch circuit 52 continues to stop applying the notification voltage to the resistor circuit 25 until the output voltage of the comparator 51 switches from a high level to a low level while the output voltage of the microcomputer 27 is high.

[0083] When the comparator 51 outputs a high-level voltage, and the microcomputer 27 switches the output voltage from a low-level voltage to a high-level voltage, the drive unit 50 switches the FET 20 to conduct. A high-level voltage output from the comparator 51 means that the voltage across the resistor circuit 25 is lower than the reference voltage Vr. When the comparator 51 outputs a high-level voltage, and the microcomputer 27 switches the output voltage from a high-level voltage to a low-level voltage, the drive unit 50 switches the FET 20 to deactivate.

[0084] When the output voltage of comparator 51 switches from a high level to a low level while the output voltage of microcomputer 27 is at a high level, the drive unit 50 switches FET 20 to off. The drive unit 50 functions as a switching unit. As described above, when the switching current increases, the voltage across resistor circuit 25 increases. When the voltage across resistor circuit 25 is higher than or equal to the reference voltage Vr, the output voltage of comparator 51 switches from a high level to a low level, and the drive unit 50 switches FET 20 to off. Therefore, overcurrent is prevented from flowing through FET 20.

[0085] When the output voltage of comparator 51 switches from a high level to a low level while the output voltage of microcomputer 27 is at a high level, latch circuit 52 applies a notification voltage to resistor circuit 25 as described above, thereby fixing the output voltage of comparator 51 to a low level. When the output voltage of microcomputer 27 switches to a low level, latch circuit 52 stops applying the notification voltage and releases the fixation.

[0086] When the output voltage of the microcomputer 27 is a low level voltage, the drive unit 50 will keep the FET 20 off regardless of the output voltage of the comparator 51, that is, the voltage across the resistor circuit 25.

[0087] Figure 3 This is a circuit diagram of latch circuit 52. Latch circuit 52 includes an inverter 60, an OR circuit 61, second circuit resistors 62 and 63, a second transistor 64, and a second diode 65. Inverter 60 has an input terminal and an output terminal. OR circuit 61 has a first input terminal, a second input terminal, and an output terminal.

[0088] The second transistor 64 is a PNP bipolar transistor that functions as a switch. When the second transistor 64 is turned on, the resistance between its emitter and collector is sufficiently small, allowing current to flow through both electrodes. When the second transistor 64 is turned off, the resistance between its emitter and collector is sufficiently large, preventing current from flowing through either electrode.

[0089] The input terminal of inverter 60 is connected to the connection node between microcomputer 27 and driver unit 50. The output terminal of inverter 60 is connected to the first input terminal of OR circuit 61. The second input terminal of OR circuit 61 is connected to the output terminal of comparator 51. The output terminal of OR circuit 61 is connected to one end of second circuit resistor 62. The other end of second circuit resistor 62 is connected to the base of second transistor 64. Second circuit resistor 63 is connected between the emitter and base of second transistor 64. The collector of second transistor 64 is connected to the anode of second diode 65. The cathode of second diode 65 is connected to the connection node between current output circuit 24 and detection resistor 30 of resistor circuit 25.

[0090] A constant voltage Vc is applied to the emitter of the second transistor 64, similar to that applied to the microprocessor 27 and transistor 40.

[0091] Furthermore, the structure of applying a constant voltage Vc to the emitter of the second transistor 64 can also be achieved by applying a constant voltage Vc through the regulator 22.

[0092] Inverter 60 outputs a voltage to OR circuit 61. The reference potential for the output voltage of inverter 60 is ground. The output voltage of inverter 60 is either a high-level voltage or a low-level voltage. The output voltage of microcomputer 27 is input to inverter 60. When the output voltage of microcomputer 27 is high, inverter 60 outputs a low-level voltage to OR circuit 61. When the output voltage of microcomputer 27 is low, inverter 60 outputs a high-level voltage to OR circuit 61.

[0093] In the second transistor 64, the second transistor 64 is turned on when the voltage at the base, where the reference potential is the emitter potential, is lower than a constant second voltage threshold. The second voltage threshold is a negative voltage. In the second transistor 64, the second transistor 64 is turned off when the voltage at the base, where the reference potential is the emitter potential, is higher than the second voltage threshold.

[0094] OR circuit 61 adjusts the output voltage. This switches the second transistor 64 to either be on or off. OR circuit 61 lowers the output voltage to a sufficiently low level, such as zero V. As a result, current flows from the emitter of the second transistor 64 through the second circuit resistors 63 and 62 in sequence, creating a voltage drop at the second circuit resistor 63. Because the current flowing through the second circuit resistor 63 is large, the voltage at the base of the second transistor 64, where the reference potential is the emitter potential, becomes lower than the second voltage threshold. Consequently, the second transistor 64 switches to be on.

[0095] OR circuit 61 raises the output voltage to a sufficiently high voltage, such as a constant voltage Vc. Consequently, the current flowing through the second circuit resistor 62 drops to zero A or a value close to zero A. At this time, in the second transistor 64, the base voltage, which is the emitter potential, becomes a voltage above the second voltage threshold, so the second transistor 64 switches off.

[0096] As described above, the OR circuit 61 switches the second transistor 64 to either be on or off.

[0097] The output voltages of comparator 51 and inverter 60 are input to OR circuit 61. When the output voltage of comparator 51 switches from high to low while the output voltage of inverter 60 is low, OR circuit 61 switches the second transistor 64 from off to on. A low output voltage of inverter 60 means that the output voltage of microcomputer 27 is high. When the second transistor 64 switches from off to on, current flows sequentially through the second transistor 64, the second diode 65, and the resistor circuit 25. Latch circuit 52 then instructs the resistor circuit 25 to apply a voltage.

[0098] The magnitude of the voltage drop generated at the second diode 65 when current flows sequentially through the anode and cathode in the second diode 65 is recorded as the second forward voltage. The informant voltage applied to the resistor circuit 25 by the latch circuit 52 is represented by (constant voltage Vc) - (second forward voltage). As mentioned above, the informant voltage is a voltage above the reference voltage. During the period when the latch circuit 52 applies the informant voltage to the resistor circuit 25, the voltage across the resistor circuit 25 is above the reference voltage Vr, therefore, the comparator 51 continuously outputs a low-level voltage.

[0099] When the inverter 60 switches its output voltage from a low level to a high level in this state, i.e., when the microcomputer 27 switches its output voltage from a high level to a low level, the OR circuit 61 switches the second transistor 64 from on to off. When the second transistor 64 switches from on to off, the current flow through the second transistor 64 and the second diode 65 stops, and the latch circuit 52 stops applying voltage to the resistor circuit 25. Thereafter, the OR circuit 61 keeps the second transistor 64 off until the output voltage of the comparator 51 switches from a high level to a low level while the output voltage of the microcomputer 27 is at a high level.

[0100] <Structure of Microcomputer 27>

[0101] Figure 4 This is a block diagram showing the main structural components of the microcomputer 27. The microcomputer 27 includes an output unit 70, an adjustment unit 71, an A / D converter 72, an input unit 73, a notification unit 74, a storage unit 75, and a control unit 76. These are connected to an internal bus 77. The output unit 70 is further connected to the drive unit 50 of the drive circuit 23 and the inverter 60 of the latch circuit 52 of the drive circuit 23. The adjustment unit 71 is further connected to the other end of the circuit resistor 43 of the application circuit 26. The A / D converter 72 is further connected to the connection node between the current output circuit 24 and the resistor circuit 25.

[0102] The output unit 70 outputs voltage to the drive unit 50 and the inverter 60. The output voltage of the output unit 70 is the same as the output voltage of the microcomputer 27 described above. The output unit 70 switches the output voltage to a high-level voltage or a low-level voltage according to the instruction of the control unit 76.

[0103] The adjustment unit 71 switches the transistor 40 of the applied circuit 26 to be on or off by adjusting the voltage across the resistor, i.e., the voltage at the other end of the circuit resistor 43. The adjustment unit 71 switches the transistor 40 according to the instructions of the control unit 76.

[0104] The analog value of the voltage across the resistor circuit 25 is input to the A / D converter 72. The A / D converter 72 performs A / D conversion on the voltage across the resistor circuit 25, that is, conversion from analog value to digital value. The control unit 76 obtains the digital value of the voltage across the resistor circuit 25 from the A / D converter 72.

[0105] Figure 5 This is an illustration of the range of voltages across the terminals undergoing A / D conversion. The lower limit of the range is zero V. The upper limit is the constant voltage Vc applied to the microcomputer 27 by the regulator 22. The reference voltage Vr applied to the positive terminal of the comparator 51 exceeds zero V and is lower than the constant voltage Vc.

[0106] exist Figure 5 In this context, Va represents the applied voltage applied by the applying circuit 26 to the resistor circuit 25. Vi represents the notification voltage applied by the latching circuit 52 of the driving circuit 23 to the resistor circuit 25. Figure 5 The diagram shows an example where the forward voltage of diode 41 coincides with the second forward voltage of the second diode 65. The applied voltage Va and the informed voltage Vi are respectively above the reference voltage Vr and below the constant voltage Vc.

[0107] like Figure 4 As shown, an on signal and an off signal are input to the input unit 73. When a signal is input, the input unit 73 notifies the control unit 76 of the input signal.

[0108] The notification unit 74 provides notification according to the instructions of the control unit 76. The control unit 76 instructs the notification unit 74 to provide notification when, although it has instructed the latch circuit 52 to stop applying the notification voltage to the resistor circuit 25, the voltage across the resistor circuit 25 remains fixed at a level above the reference voltage Vr. Notification is achieved through methods such as lighting a lamp or transmitting a signal via a communication line (not shown).

[0109] Storage unit 75 is a non-volatile memory. Computer program P is stored in storage unit 75. Control unit 76 has a processing element for performing processing, such as a CPU (Central Processing Unit), and functions as a processing unit. Control unit 76 executes computer program P, thereby performing a turn-on process to switch FET 20 to on and a turn-off process to switch FET 20 to off.

[0110] Furthermore, the computer program P can also be stored in the storage medium A in a manner readable by the processing element of the control unit 76. In this case, the computer program P, read from the storage medium A by a reading device (not shown), is written to the storage unit 75. The storage medium A is an optical disc, floppy disk, magnetic disk, magneto-optical disk, or semiconductor memory, etc. The optical disc is a CD (Compact Disc)-ROM (Read Only Memory), DVD (Digital Versatile Disc)-ROM, or BD (Blu-ray Disc), etc. The magnetic disk is, for example, a hard disk. Alternatively, the computer program P can be downloaded from a device (not shown) connected to a communication network (not shown), and the downloaded computer program P can be written to the storage unit 75.

[0111] The number of processing elements in the control unit 76 is not limited to one, and may be two or more. In this case, multiple processing elements may also cooperate to perform conduction processing and disconnection processing, etc., according to the computer program P.

[0112] In addition to the computer program P, the storage unit 75 also stores the value of a fault flag. The value of the fault flag indicates whether a notification is sent by the latch circuit 52. A fault flag value of zero indicates that a notification is sent. A fault flag value of 1 indicates that no notification is sent. The value of the fault flag is changed by the control unit 76.

[0113] <Conduction Processing>

[0114] Figure 6 This is a flowchart illustrating the sequence of the turn-on process. The control unit 76 performs the turn-on process when the microcomputer 27 is started or after the de-start process has finished. The turn-on process is performed when the output voltage of the output unit 70 is low. When the output voltage of the output unit 70 is low, the drive unit 50 of the drive circuit 23 keeps the FET 20 off. When the FET 20 is off, current does not flow through the FET 20. Therefore, the voltage across the resistor circuit 25 is lower than the reference voltage, and the output voltage of the comparator 51 of the drive circuit 23 is high.

[0115] When the output voltage of the output unit 70 is a low level voltage, the latch circuit 52 stops applying the notification voltage. When the conduction process is performed, the adjustment unit 71 stops applying voltage by maintaining the voltage at the other end of the circuit resistor 43 of the application circuit 26, i.e., the resistor voltage, at a high voltage.

[0116] During the conduction process, the control unit 76 determines whether a conduction signal has been input to the input unit 73 (step S1). If the control unit 76 determines that a conduction signal has been input (S1: "Yes"), it determines whether the value of the fault flag is zero (step S2). Since the value of the fault flag is 1 or zero, a fault flag value that is not zero means that the value of the fault flag is 1.

[0117] If the control unit 76 determines that no conduction signal has been input (S1: "No"), or if the value of the fault mark is not zero (S2: "No"), it executes step S1 again. The control unit 76 remains in standby mode until a conduction signal is input to the input unit 73 when the value of the fault mark is zero. If the control unit 76 determines that the value of the fault mark is zero (S2: "Yes"), it instructs the output unit 70 to switch the output voltage from a low level voltage to a high level voltage (step S3).

[0118] If no fault occurs in the power supply control device 10, comparator 51 outputs a high-level voltage when step S3 is executed. If no fault occurs in the power supply control device 10, the drive unit 50 switches FET 20 to conduct when step S3 is executed. After executing step S3, the control unit 76 ends the conduction process.

[0119] As described above, when a conduction signal is input while the fault flag value is zero, the drive unit 50 of the drive circuit 23 switches FET 20 to conduction, supplying power to the load 12 via FET 20. When the fault flag value is 1, the drive unit 50 does not switch FET 20 to conduction.

[0120] <Disconnection Processing>

[0121] Figure 7 This is a flowchart illustrating the sequence of the disconnection process. The control unit 76 performs the disconnection process after the conduction process has ended. The disconnection process is performed when the output voltage of the output unit 70 is high and the fault flag value is zero. At the moment the disconnection process is performed, the adjustment unit 71 maintains the voltage at the other end of the circuit resistor 43 of the application circuit 26, i.e., the resistor voltage, at a high voltage, thereby stopping the application of voltage by the application circuit 26.

[0122] After the conduction process is completed, with the switching current remaining below the current threshold, the voltage across resistor circuit 25 is lower than the reference voltage. Therefore, the output voltage of comparator 51 is a high-level voltage. When the output voltage of comparator 51 is high, latch circuit 52 stops applying the notification voltage.

[0123] After the conduction process is completed, if the switching current is above the current threshold, the voltage across the resistor circuit 25 becomes above the reference voltage, and the comparator 51 switches the output voltage from a high level to a low level. As a result, the drive unit 50 switches the FET 20 off. When the output voltage of the comparator 51 is low, the latch circuit 52 continues to apply a notification voltage to the resistor circuit 25 as long as the output voltage of the output unit 70 remains high. Therefore, the voltage across the resistor circuit 25 remains above the reference voltage.

[0124] During the disconnection process, the control unit 76 determines whether the voltage across the resistor circuit 25 is above the reference voltage (step S11). Based on this, it determines whether a notification should be sent by the latch circuit 52. A voltage above the reference voltage means a notification should be sent. The voltage across the terminals is obtained from the A / D converter 72. If the control unit 76 determines that the voltage across the terminals is below the reference voltage (S11: "No"), it determines whether a disconnection signal has been input to the input unit 73 (step S12). If the control unit 76 determines that no disconnection signal has been input (S12: "No"), it executes step S11 again and waits until the voltage across the terminals becomes above the reference voltage or a disconnection signal is input.

[0125] When the control unit 76 determines that a disconnect signal has been input (S12: "Yes"), it instructs the application circuit 26 to apply an application voltage to the resistor circuit 25 (step S13). The control unit 76 instructs the application circuit 26 to apply the application voltage by causing the adjustment unit 71 to reduce the voltage at the other end of the circuit resistor 43, i.e., the resistor voltage. As described above, when the resistor voltage decreases, the transistor 40 switches to conduct, and the application circuit 26 applies the application voltage to the resistor circuit 25.

[0126] When no fault occurs in the power supply control device 10, the voltage across the resistor circuit 25 becomes a voltage higher than the reference voltage when an applied voltage is applied. Consequently, the drive unit 50 of the drive circuit 23 switches the FET 20 off, and the latch circuit 52 informs the resistor circuit 25 of the applied voltage. This is done by informing the user of the applied voltage.

[0127] After executing step S13, the control unit 76 instructs the application circuit 26 to stop applying the applied voltage (step S14). The control unit 76 instructs the application circuit 26 to stop applying the applied voltage by increasing the resistor voltage through the adjustment unit 71. As described above, when the resistor voltage rises, the transistor 40 switches off, and the application circuit 26 stops applying the applied voltage. When no fault occurs in the power supply control device 10, even after the application circuit 26 stops applying the applied voltage, the latching circuit 52 continues to apply the notification voltage, so the voltage across the resistor circuit 25 remains above the reference voltage.

[0128] After executing step S14, the control unit 76 determines whether the voltage across the resistor circuit 25 is above the reference voltage (step S15). Based on this, it determines whether the latch circuit 52 has issued a notification. A voltage above the reference voltage means a notification has been issued. A voltage below the reference voltage means no notification has been issued. By executing step S15, the control unit 76 checks the latch circuit 52. If the drive circuit 23 is a single integrated circuit, the drive circuit 23 may malfunction if the latch circuit 52 does not issue a notification. By checking the latch circuit 52, the possibility of a malfunction in the drive circuit 23 can be detected in advance. If the control unit 76 determines that the voltage across the resistor circuit 25 is below the reference voltage (S15: "No"), it changes the value of the fault flag to 1 (step S16).

[0129] If the control unit 76 determines that the voltage at both ends is above the reference voltage (S11: "Yes"), it determines whether a disconnect signal has been input to the input unit 73 (step S17). If the control unit 76 determines that no disconnect signal has been input (S17: "No"), it executes step S17 again and waits until a disconnect signal is input.

[0130] If the control unit 76 determines that the voltage across the terminals is above the reference voltage (S15: "Yes"), after executing step S16, or if it determines that a disconnect signal has been input (S17: "Yes"), it instructs the output unit 70 to switch the output voltage from a high-level voltage to a low-level voltage (step S18). When the output voltage of the output unit 70 switches to a low-level voltage while the latch circuit 52 is applying an indication voltage, the latch circuit 52 stops applying the indication voltage. Therefore, instructing the output unit 70 to switch the output voltage to a low-level voltage is equivalent to instructing the latch circuit 52 to stop applying the indication voltage.

[0131] When no fault occurs in the power supply control device 10, upon notification that the voltage application has stopped, the voltage across the resistor circuit 25 drops to a level below the reference voltage, for example, zero V. At the moment step S18 is executed, FET 20 is turned off. Therefore, by executing step S18 through the control unit 76, the state of FET 20 remains unchanged.

[0132] After executing step S18, control unit 76 determines whether the voltage across resistor circuit 25 is lower than a reference voltage (step S19). Therefore, it determines whether the voltage across the terminals has dropped below the reference voltage. If control unit 76 determines that the voltage across the terminals is above the reference voltage (S19: "No"), it instructs notification unit 74 to provide notification (step S20). If control unit 76 determines that the voltage across the terminals is lower than the reference voltage (S19: "Yes"), or after executing step S20, it terminates the disconnection process.

[0133] <Operation of Power Supply Control Device 10>

[0134] Figure 8 This is a timing diagram used to illustrate the operation of the power supply control device 10. Figure 8 The diagram shows the output voltage of output unit 70, the state of FET 20, the application state of application circuit 26, the application state of latch circuit 52, the voltage across resistor circuit 25, and the evolution of switching current. H and L represent high-level voltage and low-level voltage, respectively. Va, Vi, Vr, and Ith represent applied voltage, informative voltage, reference voltage, and current threshold, respectively. Figure 8 The diagram shows the operation when no fault occurs in the power supply control device 10 and the applied voltage Va and the informed voltage Vi are consistent.

[0135] like Figure 8 As shown, when the output voltage of the output unit 70 is a low-level voltage, the drive unit 50 keeps the FET 20 off, and the switching current is zero A. Since the switching current is zero A, the voltage across the resistor circuit 25 is zero V, which is lower than the reference voltage Vr. When the output voltage of the output unit 70 is a low-level voltage, the application circuit 26 and the latch circuit 52 stop applying the voltage and the notification voltage, respectively.

[0136] When an on signal is input to the input section 73 of the microcomputer 27, the control section 76 instructs the output section 70 to switch the output voltage from a low level to a high level. At this time, the switching current is zero A, and the voltage across the resistor circuit 25 is lower than the reference voltage. Therefore, the drive section 50 of the drive circuit 23 switches the FET 20 to conduct. With the FET 20 conducting, the switching current flows through the FET 20. As a result, the switching current rises to a current exceeding zero A but below the current threshold Ith. In addition, the voltage across the resistor circuit 25 rises to a voltage exceeding zero V but below the reference voltage Vr.

[0137] When a disconnect signal is input to input unit 73, control unit 76 instructs application circuit 26 to apply voltage Va to resistor circuit 25. As a result, the voltage across resistor circuit 25 rises to the applied voltage Va, which is higher than the reference voltage Vr. Consequently, drive unit 50 switches FET 20 to disconnect, and latch circuit 52 instructs voltage Vi to be applied to resistor circuit 25. When FET 20 is switched to disconnect, the switching current drops to zero A.

[0138] When the applied voltage Va and the informed voltage Vi are different from each other, during the application of the application circuit 26 and the latching circuit 52, the voltage across them is consistent with the higher of the applied voltage Va and the informed voltage Vi.

[0139] After applying the applied voltage Va to the applied circuit 26, the control unit 76 instructs the applied circuit 26 to stop applying the applied voltage Va. Even when the applied voltage Va is stopped, the voltage across the resistor circuit 25 remains above the reference voltage Vr because the latch circuit 52 applies the notification voltage Vi. After instructing the applied circuit 26 to stop applying the applied voltage Va, the control unit 76 determines whether the voltage across the resistor circuit 25 is above the reference voltage Vr. Therefore, the control unit 76 determines whether the latch circuit 52 has provided notification. If the control unit 76 determines that the voltage across the resistor circuit 25 is below the reference voltage Vr, it considers that no notification has been provided and changes the fault flag value from zero to 1.

[0140] After determining whether to issue a notification, the control unit 76 instructs the output unit 70 to switch the output voltage from a high level to a low level. As a result, the latch circuit 52 stops applying the notification voltage Vi. At this time, since the switching current is zero A, the voltage across the resistor circuit 25 drops to zero V. Zero V is a voltage lower than the reference voltage Vr. After the output unit 70 switches the output voltage to a low level, the control unit 76 determines whether the voltage across the resistor circuit 25 has dropped below the reference voltage Vr. This confirms that the voltage across the resistor circuit 25 has returned to a level lower than the reference voltage Vr. If the voltage across the resistor circuit 25 is above the reference voltage Vr, the control unit 76 instructs the notification unit 74 to issue a notification.

[0141] As described above, in the power supply control device 10, the latch circuit 52 is checked at the time when a disconnect signal is input, that is, at the time when FET 20 is required to switch to disconnect. If no fault occurs in the power supply control device 10, FET 20 switches to disconnect when the application circuit 26 applies the applied voltage to the resistor circuit 25.

[0142] <Modifications of Implementation Method 1>

[0143] FET 20 can function as a switch. Therefore, instead of FET 20, a P-channel FET, bipolar transistor, or relay contact can be used. Resistor circuit 25 can be a circuit with sensing resistor 30. Therefore, resistor circuit 25 can also be a circuit in which circuit elements, such as capacitors, are connected in parallel to sensing resistor 30. The voltage applied to the emitter of transistor 40 in application circuit 26 can be a voltage higher than the reference voltage Vr. Therefore, the voltage applied to the emitter of transistor 40 can also be different from the constant voltage Vc generated by regulator 22. Transistor 40 in application circuit 26 can function as a switch. Therefore, instead of transistor 40, a P-channel FET or relay contact can be used.

[0144] The application circuit 26 is simply a circuit that applies an applied voltage to the resistor circuit 25 according to the instructions of the microcomputer 27, i.e., the control unit 76. Therefore, the application circuit 26 can also be a circuit with a processing element such as a CPU. In this case, the processing element of the application circuit 26 instructs the control unit 76 to apply an applied voltage to the resistor circuit 25.

[0145] The voltage applied to the emitter of the second transistor 64 in the latch circuit 52 only needs to be higher than the reference voltage Vr. Therefore, the voltage applied to the emitter of the second transistor 64 can also be different from the constant voltage Vc generated by the regulator 22. The second transistor 64 in the latch circuit 52 can function as a switch. Therefore, a P-channel FET or relay contact can be used instead of the second transistor 64.

[0146] The latch circuit 52 is a circuit that applies and stops applying a notification voltage based on the output voltage of the output unit 70 and the output voltage of the comparator 51 of the microcomputer 27. Therefore, the application circuit 26 can also be a circuit with a processing element, such as a CPU. In this case, the processing element of the application circuit 26 determines whether to apply a notification voltage and whether to stop applying a notification voltage based on the output voltage of the output unit 70 and the comparator 51.

[0147] The timing for checking the latch circuit 52 is not limited to the time when a disconnect signal is input to the input unit 73 of the microcomputer 27. The control unit 76 of the microcomputer 27 may also periodically check the latch circuit 52. The timing for the latch circuit 52 to stop applying the notification voltage is not limited to the time when the output voltage of the output unit 70 switches from a high level voltage to a low level voltage; for example, it may be the time when a constant time has elapsed since the notification voltage was applied.

[0148] The notification provided by the latch circuit 52 is not limited to notification achieved by applying a notification voltage. For example, it can also be achieved by outputting a signal indicating that the voltage across the resistor circuit 25 is above the reference voltage.

[0149] (Implementation Method 2)

[0150] In Embodiment 1, the power supply control device 10 is disposed upstream of the load 12 in the current path from the positive terminal to the negative terminal of the DC power supply 11. However, the location of the power supply control device 10 is not limited to the upstream side of the load 12.

[0151] The differences between Embodiment 2 and Embodiment 1 will now be explained. Except for the structures described later, the other structures are the same as in Embodiment 1. Therefore, the same reference numerals are used for the structural parts common to Embodiment 1, and their descriptions are omitted.

[0152] <Structure of Power System 1>

[0153] Figure 9 This is a block diagram showing the main structure of the power supply system 1 in Embodiment 2. When comparing the power supply system 1 in Embodiment 2 with the power supply system 1 in Embodiment 1, the location of the power supply control device 10 differs. In the power supply system 1 of Embodiment 2, the power supply control device 10 is located downstream of the load 12 in the current path from the positive terminal to the negative terminal of the DC power supply 11.

[0154] The positive terminal of the DC power supply 11 is connected to one end of the load 12. In the case where the power supply control device 10 has a FET 20, the drain of the FET 20 is connected to the other end of the load 12. The source of the FET 20 is connected to one end of the shunt resistor 21, similar to Embodiment 1. The other end of the shunt resistor 21 is grounded. The negative terminal of the DC power supply 11 is grounded, similar to Embodiment 1.

[0155] The power supply control device 10 in Embodiment 2 also has the same effect as the power supply control device 10 in Embodiment 1.

[0156] It should be considered that the disclosed embodiments 1 and 2 are exemplary in all respects and not restrictive. The scope of the invention is defined not by the foregoing meaning but by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0157] Explanation of reference numerals in the attached figures

[0158] 1 Power System

[0159] 10 Power supply control device

[0160] 11 DC Power Supply

[0161] 12 Load

[0162] 20 FETs (switches)

[0163] 21 Shunt resistor

[0164] 22 Regulator

[0165] 23. Drive Circuit

[0166] 24 Current Output Circuit

[0167] 25 Resistor Circuit

[0168] 26 Application Circuit

[0169] 27 Microcomputer

[0170] 30 Sensing Resistor

[0171] 40 transistors

[0172] 41 Diode

[0173] 42, 43 Circuit Resistance

[0174] 50. Drive Unit (Switching Unit)

[0175] 51 comparator

[0176] 52. Latch circuit (notification circuit)

[0177] 60 inverter

[0178] 61 OR circuit

[0179] 62, 63 Second circuit resistors

[0180] 64 Second transistor

[0181] 65 Second Diode

[0182] 70 Output Section

[0183] 71 Adjustment Department

[0184] 72 A / D Conversion Section

[0185] 73 Input Section

[0186] 74 Notification Department

[0187] 75 Storage Section

[0188] 76. Control Department (Processing Department)

[0189] 77 Internal Bus

[0190] A storage medium

[0191] P is a computer program.

Claims

1. A power supply control device that controls power supply by switching a switch to be on or off. The power supply control device includes: A resistive circuit through which a rising current flows when the current flowing through the switch increases; The notification circuit notifies the user when the voltage across the two ends of the resistor circuit is above a predetermined voltage. An application circuit applies a voltage above the predetermined voltage to the resistor circuit; and Processing Department, Execute Processing The processing unit instructs the application circuit to apply voltage to the resistor circuit based on the input of the switch's open signal, and after instructing the application circuit to apply voltage, determines whether the notification circuit should provide notification.

2. The power supply control device according to claim 1, wherein, The notification circuit provides the notification by applying a voltage above the predetermined voltage to the resistor circuit. After instructing the application circuit to apply voltage, the processing unit instructs the application circuit to stop applying voltage. After instructing the application circuit to stop applying voltage, it determines whether the notification circuit should issue the notification based on the voltage between the two ends of the resistor circuit.

3. The power supply control device according to claim 2, wherein, The power supply control device includes a switching unit that switches the switch to open when the voltage across the resistor circuit is above the predetermined voltage. When the processing unit receives a disconnect signal indicating that the switch should be switched to open, it instructs the application circuit to apply a voltage to the resistor circuit.

4. The power supply control device according to claim 2 or 3, wherein, When the processing unit determines that the notification circuit is providing the notification, it instructs the application circuit to stop applying voltage. After instructing the application circuit to stop applying voltage, it determines whether the voltage between the two ends of the resistor circuit is lower than the predetermined voltage.

5. A method for checking a notification circuit, wherein the notification circuit provides notification when the voltage across a resistive circuit through which the increased current flows after a switch has increased is a voltage greater than or equal to a predetermined voltage. The inspection method is performed by a computer in the following steps: Based on the input of the switch's open signal, an instruction is given to apply a voltage above the predetermined voltage to the resistor circuit; and After instructing the application of voltage to the resistor circuit, it is determined whether the notification circuit should issue a notification.

6. A computer program product comprising a computer program for causing a computer to check a notification circuit, said notification circuit providing a notification when the voltage between the two ends of a resistive circuit through which the increased current flows when the current flowing through a switch increases is above a predetermined voltage. The computer program is used to cause the computer to perform the following steps: Based on the input of the switch's open signal, an instruction is given to apply a voltage above the predetermined voltage to the resistor circuit; and After instructing the application of voltage to the resistor circuit, it is determined whether the notification circuit should issue a notification.

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