drive device

Abstract

A drive device (11) drives a load (13). In a current path of an electric current flowing through the load (13), an N-channel MOSFET (20) is arranged on a downstream side of the load (13). A circuit resistance (21) is connected between a direct-current power supply (10) and a gate of the MOSFET (20). A first switch (22) is connected between the gate and a source of the MOSFET (20). A microcomputer (30) outputs a voltage referenced to a potential of an output terminal of a second switch (26) to a control terminal of the second switch (26). Thus, the second switch (26) is switched on or off. In a case where the second switch (26) is switched on, a switching circuit (25) switches the first switch (22) on, and in a case where the second switch (26) is switched off, the switching circuit (25) switches the first switch (22) off.

Description

Technical Field

[0001] This disclosure relates to a drive device.

[0002] This application claims priority based on Japanese Application No. 2019-229585, filed on December 19, 2019, and invokes all the contents of that Japanese application. Background Technology

[0003] In a vehicle, a power system is provided, such as a battery, to supply power to a load. The power system includes a drive device for driving the load. Patent Document 1 discloses a drive device for driving a load. This drive device includes a switch disposed downstream of the load in the current path flowing through the load, and a drive circuit for switching the switch on or off. When the switch is on, current flows sequentially from the DC power source through the load and the switch, supplying power to the load.

[0004] The switch is an N-channel FET (Field Effect Transistor). The drain of the switch is connected to the load. The source of the switch is grounded. The driving circuit outputs a control signal consisting of a high-level voltage and a low-level voltage to the gate of the switch. The switch turns on when the gate voltage (referenced to the source potential) is above a threshold, and turns off when the gate voltage (referenced to the source potential) is below the threshold. The driving circuit switches the switch on by switching the control signal voltage high and off by switching the control signal voltage low.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-216229 Summary of the Invention

[0008] One aspect of the present disclosure is a driving device for driving a load, the driving device comprising: an N-channel MOSFET disposed downstream of the load in a current path through which current flows via the load; a resistor connected between a DC power supply and the gate of the MOSFET; a first switch connected between the gate and source of the MOSFET; a second switch that is turned on when the voltage at a control terminal, based on the potential of the output terminal where current is output, is above a threshold; a switching circuit that switches the first switch on when the second switch is turned on, and switches the first switch off when the second switch is turned off; and an output unit that outputs a voltage based on the potential of the output terminal of the second switch to the control terminal of the second switch. Attached Figure Description

[0009] Figure 1 This is a block diagram showing the main structural components of the power supply system in Embodiment 1.

[0010] Figure 2 This is the circuit diagram of the drive device.

[0011] Figure 3 This is a timing diagram used to illustrate the switching of MOSFETs.

[0012] Figure 4 This is a block diagram showing the main structural components of the drive device in Embodiment 2.

[0013] Figure 5 It is a timing diagram used to illustrate the operation of the drive device.

[0014] Figure 6 This is the circuit diagram of the first downstream drive circuit. Detailed Implementation

[0015] [The problem this disclosure aims to solve]

[0016] In conventional drive devices as described in Patent Document 1, the drive circuit is grounded via a wire. Grounding is achieved by connecting to a grounding conductor. One end of the wire is connected to the drive circuit. The other end of the wire is grounded. The voltage of the control signal output by the drive circuit is a voltage referenced to the potential of one end of the wire. In a vehicle, electrical equipment different from the load may be grounded via a common wire. In this structure, the current flowing through the wire varies due to the operation or cessation of the electrical equipment. Wires typically have inductive and resistive components. Therefore, when the current flowing through the wire varies, the voltage at one end of the wire, referenced to the grounding potential, varies. Furthermore, even if the electrical equipment is not grounded via a common wire, the voltage at one end of the wire, referenced to the grounding potential, varies when noise-related current flows through the wire or when the contact resistance of the wire at the grounding conductor increases.

[0017] Because the source of the switch is grounded, the switch switches to on or off based on the voltage at the gate, which is referenced to the ground potential. If the voltage at one end of the wire referenced to the ground potential is negative, the switch may not switch to on even if the control signal outputs a high-level voltage. Conversely, if the voltage at one end of the wire referenced to the ground potential is high, the switch may not switch to off even if the control signal outputs a low-level voltage.

[0018] Therefore, the objective is to provide a drive device that can switch the switch on or off without error even when the reference potential of the control voltage changes.

[0019] [The Effects of This Disclosure]

[0020] According to this disclosure, even if the reference potential of the control voltage changes, the MOSFET can be switched on or off without error.

[0021] [Description of embodiments of this disclosure]

[0022] First, embodiments of this disclosure will be described by way of example. At least some of the embodiments described below may be combined arbitrarily.

[0023] (1) A driving device according to one aspect of the present disclosure drives a load, the driving device comprising: an N-channel MOSFET disposed downstream of the load in a current path through which current flows through the load; a resistor connected between a DC power supply and the gate of the MOSFET; a first switch connected between the gate and the source of the MOSFET; a second switch turned on when the voltage at a control terminal based on the potential of the output terminal where current is output is above a threshold; a switching circuit that turns the first switch on when the second switch is turned on, and turns the first switch off when the second switch is turned off; and an output unit that outputs a voltage based on the potential of the output terminal of the second switch to the control terminal of the second switch.

[0024] In one of the above methods, the output unit outputs a control voltage based on the potential of the output terminal of the second switch. The second switch switches on or off according to the voltage at the control terminal, which is based on the potential of the output terminal. Therefore, even if the voltage at the output terminal of the second switch, which is based on the reference potential of the control voltage (i.e., the ground potential), changes, the second switch will switch on or off without error.

[0025] When the second switch is turned on, the switching circuit turns the first switch on. When the first switch is turned on, the gate voltage in the MOSFET, referenced to the source potential, drops to zero V, and the MOSFET turns off. When the second switch is turned off, the switching circuit turns the first switch off. When the first switch is turned off, the gate voltage in the MOSFET, referenced to the source potential, rises, and the MOSFET turns on. If the second switch switching is error-free, the MOSFET switching also proceeds error-free. As a result, even if the reference potential of the control voltage changes, the MOSFET switches on or off without error.

[0026] (2) In one aspect of the driving device of this disclosure, the output terminal of the second switch is connected to a ground conductor via a first wire, and the source of the MOSFET is connected to the ground conductor via a second wire.

[0027] In one of the above methods, grounding is achieved by connecting to a grounding conductor. The first conductor has both inductive and resistive components. Therefore, when the current flowing through the first conductor changes, the voltage at the output of the second switch, which is referenced to the potential of the grounding conductor (i.e., the grounding potential), changes.

[0028] (3) A driving device according to one aspect of the present disclosure, wherein the first switch is turned on when the voltage of the control terminal based on the potential of the output terminal where the current is output is above a second threshold, the driving device includes a second resistor connected between the control terminal and the output terminal of the first switch, the input terminal of the first switch where the current is input is connected to the gate of the MOSFET, the output terminal of the first switch is connected to the source of the MOSFET, the switching circuit includes a third switch that is turned on when the voltage of the control terminal based on the potential of the input terminal where the current is input is below a third threshold and a third resistor connected between the control terminal and the input terminal of the third switch, the input terminal of the third switch is connected to the DC power supply, the output terminal of the third switch where the current is output is connected to the control terminal of the first switch, and the control terminal of the third switch is connected to the input terminal of the second switch where the current is input.

[0029] In one of the above methods, for example, the source of the MOSFET and the output of the second switch are grounded. When the second switch is on, current flows sequentially through the third resistor and the second switch. At this time, in the third switch, the voltage at the control terminal, referenced to the input potential, is negative, below the third threshold. Therefore, when the second switch is on, the third switch is on. When the third switch is on, current flows sequentially through the third switch and the second resistor. At this time, in the first switch, the voltage at the control terminal, referenced to the output potential, is positive, above the second threshold. Therefore, when the third switch is on, the first switch is on.

[0030] When the second switch is open, no current flows through the third resistor. At this time, in the third switch, the voltage at the control terminal, referenced to the input potential, is zero V, which is above the third threshold. Therefore, when the second switch is open, the third switch is open. When the third switch is open, no current flows through the second resistor. At this time, in the first switch, the voltage at the control terminal, referenced to the output potential, is zero V, which is below the second threshold. Therefore, when the third switch is open, the first switch is open.

[0031] [Details of the embodiments disclosed herein]

[0032] 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 invention is not limited to these examples, but is indicated by the claims, which are intended to include all modifications within the meaning and scope equivalent to the claims.

[0033] (Implementation Method 1)

[0034] <Structure of Power Supply System>

[0035] Figure 1This 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 DC power supply 10, a drive unit 11, multiple electrical devices 12, a load 13, a first conductor 14, a second conductor 15, and a ground conductor 16. The DC power supply 10 is, for example, a battery. The load 13 is an electrical device mounted in the vehicle. The electrical device 12 is, for example, an ECU (Electronic Control Unit). The first conductor 14 and the second conductor 15 each have an inductive component and a resistive component. The equivalent circuit of the first conductor 14 is represented by a series circuit of an inductor 14a and a conductor resistor 14b. One end and the other end of the first conductor 14 each correspond to one end and the other end of the series circuit. The equivalent circuit of the second conductor 15 is also represented by a series circuit of an inductor and a conductor resistor.

[0036] The positive terminal of the DC power supply 10 is connected to the drive unit 11 and multiple electrical devices 12. The drive unit 11 is connected to one end and the other end of the load 13. The negative terminal of the DC power supply 10 is connected to the grounding conductor 16. The drive unit 11 and the multiple electrical devices 12 are connected to one end of the first conductor 14. The other end of the first conductor 14 is connected to the grounding conductor 16. The drive unit 11 is further connected to one end of the second conductor 15. The other end of the second conductor 15 is connected to the grounding conductor 16.

[0037] The grounding conductor 16 is, for example, the body of a vehicle. The negative terminal of the DC power supply 10 is grounded by connecting it to the grounding conductor 16. The drive unit 11 and the plurality of electrical devices 12 are grounded by connecting them to the grounding conductor 16 via the first conductor 14.

[0038] The DC power supply 10 supplies power to the drive unit 11 and a plurality of electrical devices 12. When the DC power supply 10 supplies power to the drive unit 11, current flows sequentially from the positive terminal of the DC power supply 10 through the drive unit 11, the first conductor 14, and the grounding conductor 16, and returns to the negative terminal of the DC power supply 10. When the DC power supply 10 supplies power to the electrical devices 12, current flows sequentially from the positive terminal of the DC power supply 10 through the electrical devices 12, the first conductor 14, and the grounding conductor 16, and returns to the negative terminal of the DC power supply 10.

[0039] When the electrical equipment 12 is operating, or when the electrical equipment 12 is not operating, the current output from the electrical equipment 12 to the first conductor 14 changes. When the electrical equipment 12 is operating, the current output from the electrical equipment 12 to the first conductor 14 increases. When the electrical equipment 12 is not operating, the current output from the electrical equipment 12 to the first conductor 14 decreases.

[0040] Multiple electrical devices 12 operate or stop operating respectively. Therefore, the current flowing through the first conductor 14 fluctuates significantly. As the current flowing through the first conductor 14 increases, the voltage drop caused by the conductor resistance 14b of the first conductor 14 increases, thus increasing the voltage at one end of the first conductor 14 relative to the potential of the ground conductor 16. The greater the increase in current flowing through the first conductor 14, the greater the increase in voltage at one end of the first conductor 14 relative to the potential of the ground conductor 16.

[0041] When the current flowing through the first conductor 14 decreases, the inductor 14a causes a decrease in the voltage at one end of the first conductor 14, which is referenced to the potential at one end of the ground conductor 16. Consequently, the voltage at one end of the first conductor 14, referenced to the potential of the ground conductor 16, decreases. The greater the decrease in the current flowing through the first conductor 14, the greater the decrease in the voltage at one end of the first conductor 14, referenced to the potential of the ground conductor 16.

[0042] Based on the above, the voltage at one end of the first conductor 14, which is referenced to the potential of the grounding conductor 16, changes. The voltage at one end of the first conductor 14 is the voltage of the connection node between the drive device 11 and the first conductor 14.

[0043] Furthermore, the power supply system 1 may not have electrical equipment 12. That is, electrical equipment 12 may not be connected to one end of the first conductor 14. Even in this case, the current flowing through the first conductor 14 changes when noise-related current flows through the first conductor 14 or when the contact resistance of the first conductor 14 at the grounding conductor 16 increases. As a result, the voltage at one end of the first conductor 14, based on the potential of the grounding conductor 16, changes.

[0044] The following is an example illustrating the structure of connecting multiple electrical devices 12 to one end of the first conductor 14.

[0045] One end of the load 13 is connected to the positive terminal of the DC power supply 10 via the drive device 11. The drive device 11 has an N-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) 20 (see reference) that functions as a switch. Figure 2The other end of load 13 is connected to ground conductor 16 via MOSFET 20 and second wire 15. Drive device 11 switches MOSFET 20 to ON. Thus, DC power supply 10 supplies power to load 13, and load 13 operates. Drive device 11 drives load 13 by switching MOSFET 20 ON. Drive device 11 switches MOSFET 20 OFF. Thus, DC power supply 10 stops supplying power to load 13, and load 13 stops operating.

[0046] Even if the voltage at one end of the first wire 14, which is based on the potential of the ground conductor 16, changes as described later, the drive device 11 can switch the MOSFET 20 on or off without error.

[0047] <Structure of Drive Unit 11>

[0048] Figure 2 This is a circuit diagram of the drive device 11. In addition to the MOSFET 20, the drive device 11 also includes a circuit resistor 21, a first switch 22, first switching resistors 23 and 24, a switching circuit 25, a second switch 26, second switching resistors 27 and 28, a regulator 29, and a microcomputer (hereinafter referred to as a microcomputer) 30. The switching circuit 25 includes a third switch 40 and third switching resistors 41 and 42. The first switch 22 and the second switch 26 are each NPN bipolar transistors. The third switch 40 is a PNP bipolar transistor.

[0049] The drain of MOSFET 20 is connected to the other end of load 13. The source of MOSFET 20 is connected to ground conductor 16 via second wire 15. One end of circuit resistor 21 is connected to the positive terminal of DC power supply 10. The other end of circuit resistor 21 is connected to the gate of MOSFET 20. The gate of MOSFET 20 is further connected to the collector of first switch 22. The emitter of first switch 22 is connected to the source of MOSFET 20 and one end of second wire 15. First switch resistor 23 is connected between the base and emitter of first switch 22. First switch resistor 23 functions as a second resistor. The base of first switch 22 is further connected to one end of first switch resistor 24.

[0050] The positive terminal of the DC power supply 10 is connected to the emitter of the third switch 40 in the switching circuit 25. The collector of the third switch 40 is connected to the other end of the first switching resistor 24. Within the switching circuit 25, a third switching resistor 41 is connected between the base and emitter of the third switch 40. The third switching resistor 41 functions as a third resistor. The base of the third switch 40 is further connected to one end of the third switching resistor 42.

[0051] The other end of the third switching resistor 42 is connected to the collector of the second switch 26. The emitter of the second switch 26 is connected to one end of the first wire 14. The second switching resistor 27 is connected between the base and emitter of the second switch 26. The base of the second switch 26 is further connected to one end of the second switching resistor 28. The other end of the second switching resistor 28 is connected to the microcomputer 30.

[0052] The positive terminal of the DC power supply 10 is connected to the regulator 29. The regulator 29 is further connected to the microcomputer 30. The microcomputer 30 is further connected to one end of the first wire 14.

[0053] As described above, the first switch 22 is connected between the gate and source of the MOSFET 20. The emitter of the second switch 26 is connected to the ground conductor 16 via the first wire 14. A plurality of electrical devices 12 are connected to the connection node between the emitter of the second switch and the first wire 14.

[0054] The collector of the third switch 40 is connected to the base of the first switch 22 via the first switch resistor 24.

[0055] The base of the third switch 40 is connected to the collector of the second switch 26 via the third switch resistor 42.

[0056] <Operation of Drive Unit 11>

[0057] When the gate voltage in MOSFET 20, referenced to the source potential, is above the gate threshold, the resistance between the drain and source is sufficiently small. In this case, MOSFET 20 is turned on, and current flows through the drain and source. When the gate voltage in MOSFET 20, referenced to the source potential, is below the gate threshold, the resistance between the drain and source is sufficiently large. In this case, MOSFET 20 is turned off, and current does not flow through the drain and source. The gate threshold is a positive, constant value and is preset.

[0058] When the base voltage (based on the emitter potential) in the first switch 22 is above a first voltage threshold, the resistance between the collector and emitter is sufficiently small. At this time, the first switch 22 is closed, and current can flow through the collector and emitter. When the base voltage (based on the emitter potential) in the first switch 22 is below the first voltage threshold, the resistance between the collector and emitter is sufficiently large. At this time, the first switch 22 is open, and current does not flow through the collector and emitter. The first voltage threshold is a positive constant value and is preset. The first voltage threshold corresponds to the second threshold.

[0059] The second switch 26 is configured similarly to the first switch 22. The second switch 26 is turned on when the base voltage (based on the emitter potential) in the second switch 26 is above a second voltage threshold. The second switch 26 is turned off when the base voltage (based on the emitter potential) in the second switch 26 is below the second voltage threshold. The second voltage threshold is a positive constant value and is preset.

[0060] When the base voltage (based on the emitter potential) in the third switch 40 is lower than the third voltage threshold, the resistance between the emitter and collector is sufficiently small. At this time, the third switch 40 is closed, and current can flow through the emitter and collector. When the base voltage (based on the emitter potential) in the third switch 40 is higher than the third voltage threshold, the resistance between the emitter and collector is sufficiently large. At this time, the third switch 40 is open, and current does not flow through the emitter and collector. The third voltage threshold is a negative constant value and is preset. The third voltage threshold is equivalent to the third threshold.

[0061] The voltage of the DC power supply 10, referenced to the potential of the ground conductor 16, will be described as the power supply voltage. The regulator 29 reduces the power supply voltage to a target voltage and applies the target voltage to the microcomputer 30. Thus, power is supplied to the microcomputer 30. The power supply voltage is, for example, 12V. The target voltage is, for example, 5V. When power is supplied to the microcomputer 30, current flows sequentially from the positive terminal of the DC power supply 10 through the regulator 29, the microcomputer 30, the first wire 14, and the ground conductor 16.

[0062] The microprocessor 30 outputs a control signal consisting of a high-level voltage and a low-level voltage to the control terminal of the second switch 26 via the second switching resistor 28. The high-level voltage and low-level voltage are each set as the potential of the emitter of the second switch 26. The high-level voltage is higher than the low-level voltage. The low-level voltage is, for example, zero V. By switching the voltage of the control signal, the microprocessor 30 switches the MOSFET 20 to be on or off. The microprocessor 30 functions as an output unit.

[0063] As described above, the current flowing through the first conductor 14 changes due to the operation or cessation of multiple electrical devices. When the current flowing through the first conductor 14 changes, the voltage at one end of the first conductor 14 changes based on the potential of the emitter of the second switch 26, i.e., the potential of the ground conductor 16.

[0064] Furthermore, as described above, when the contact resistance of the first conductor 14, which is related to noise, increases, the current flowing through the first conductor 14 also changes, and the voltage at one end of the first conductor 14, which is based on the potential of the ground conductor 16, also changes.

[0065] Figure 3 This is a timing diagram used to illustrate the switching of MOSFET20. Figure 3 In the diagram, "H" represents a high-level voltage and "L" represents a low-level voltage. The evolution of the control signal voltage and the states of the second switch 26, the third switch 40, the first switch 22, and the MOSFET 20 are shown. Time is represented on the horizontal axis to illustrate these evolutions.

[0066] When the control signal voltage exceeds zero V, current flows from the microprocessor 30 through the second switching resistors 28 and 27 sequentially, returning to the microprocessor 30. When driving the load 13, the microprocessor 30 switches the control signal voltage from a high level to a low level. When the control signal voltage is low, the current flowing through the second switching resistor is sufficiently small or zero A. Therefore, in the second switch 26, the base voltage, referenced to the emitter potential, is sufficiently low or zero V, below the second voltage threshold. Therefore, the second switch 26 is open.

[0067] With the second switch 26 open, no current flows through the third switch resistors 41 and 42. Therefore, in the third switch 40, the base voltage relative to the emitter potential is zero V, which is above the third voltage threshold. Therefore, the third switch 40 is open.

[0068] With the third switch 40 open, no current flows through the first switch resistors 23 and 24. Therefore, in the first switch 22, the base voltage, referenced to the emitter potential, is zero V, which is below the first voltage threshold. Thus, the first switch 22 is open. Therefore, when the second switch 26 is switched open, the switching circuit 25 switches the first switch 22 to open as well.

[0069] When the first switch 22 is open, no current flows through the circuit resistor 21, so the gate voltage, referenced to the potential of the ground conductor 16, is the power supply voltage. When noise-related current flows through the second conductor 15, or when the contact resistance of the second conductor 15 at the ground conductor 16 increases, the voltage at one end of the second conductor 15, i.e., the source of the MOSFET 20, referenced to the potential of the ground conductor 16, fluctuates. The power supply voltage is sufficiently greater than the maximum value of the source voltage of the MOSFET 20, referenced to the potential of the ground conductor 16. The difference between this maximum value and the power supply voltage is above the gate threshold. Therefore, when the first switch 22 is open, in the MOSFET 20, the gate voltage, referenced to the source potential, is above the gate threshold, and the MOSFET 20 is turned on.

[0070] When MOSFET 20 is turned on, current flows from the positive terminal of DC power supply 10 through load 13, MOSFET 20, second wire 15, and ground conductor 16, and returns to the negative terminal of DC power supply 10. This supplies power to load 13, causing load 13 to operate. At this time, current is input to the drain of MOSFET 20 and output from the source of MOSFET 20.

[0071] The current path from the positive terminal of the DC power supply 10 through the load 13, MOSFET 20, second conductor 15, and ground conductor 16 is the current path through the load 13. MOSFET 20 is positioned downstream of the load 13 in this current path.

[0072] When the microprocessor 30 stops the operation of the load 13, it switches the control signal voltage from a low level to a high level. When the control signal voltage is high, the current flowing sequentially through the second switching resistors 28 and 27 is sufficiently large. Therefore, when the control signal voltage is high, the base voltage in the second switch 26, referenced to the emitter potential, is above the second voltage threshold, and the second switch 26 is turned on.

[0073] With the second switch 26 closed, current flows sequentially from the positive terminal of the DC power supply 10 through the third switch resistors 41 and 42, the second switch 26, the first wire 14, and the grounding conductor 16, returning to the negative terminal of the DC power supply 10. This results in a voltage drop at the third switch resistor 41, and in the third switch 40, the base voltage, referenced to the emitter potential, is lower than the third voltage threshold. Consequently, with the second switch 26 closed, the third switch 40 is closed.

[0074] When the second switch 26 is turned on, current is input to the collector of the second switch 26, and current is output from the emitter of the second switch 26. Regarding the second switch 26, the collector, emitter, and base function as the input terminal, output terminal, and control terminal, respectively.

[0075] When the third switch 40 is closed, current flows sequentially from the positive terminal of the DC power supply 10 through the third switch 40, the first switching resistors 24 and 23, the second wire 15, and the grounding conductor 16, returning to the negative terminal of the DC power supply 10. This results in a voltage drop across the first switching resistor 23, and in the first switch 22, the base voltage, referenced to the emitter potential, is above a first voltage threshold. Consequently, when the third switch 40 is closed, the first switch 22 is closed. When the second switch 26 is closed, the switching circuit 25 switches the first switch 22 to closed.

[0076] As described above, the power supply voltage is sufficiently greater than the maximum voltage at the source of MOSFET 20, i.e., the emitter of the first switch 22, which is referenced to the potential of ground conductor 16. Therefore, the current flowing through the first switching resistor 23 is large, and the voltage drop across the first switching resistor 23 is greater than the first voltage threshold. Therefore, when the third switch 40 is turned on, the first switch 22 reliably switches to the on position.

[0077] When the third switch 40 is turned on, current is input to the emitter of the third switch 40, and current is output from the collector of the third switch 40. Regarding the third switch 40, the emitter, collector, and base function as the input terminal, output terminal, and control terminal, respectively.

[0078] When the first switch 22 is turned on, the gate voltage in MOSFET 20, referenced to the source potential, is zero V, which is below the gate threshold. Therefore, when the first switch 22 is turned on, MOSFET 20 is turned off.

[0079] As described above, when the control signal voltage is a low level, that is, when the microcomputer 30 outputs a low level voltage to the gate of the second switch 26, the MOSFET 20 is turned on. When the control signal voltage is a high level, that is, when the microcomputer 30 outputs a high level voltage to the gate of the second switch 26, the MOSFET 20 is turned off.

[0080] When the first switch 22 is closed, current flows from the positive terminal of the DC power supply 10 through the circuit resistor 21, the first switch 22, the second wire 15, and the grounding conductor 16, returning to the negative terminal of the DC power supply 10. When the first switch 22 is closed, current is input to the collector of the first switch 22, and current is output from the emitter of the first switch 22. Regarding the first switch 22, the collector, emitter, and base function as the input terminal, output terminal, and control terminal, respectively.

[0081] In the event of a break in the first conductor 14, or a detachment of the connection between the drive device 11 via the first conductor 14 and the ground conductor 16, the emitter of the second switch 26 becomes open. In this case, no current flows through the second switch resistor 27, so the base voltage in the second switch 26, based on the emitter potential, is zero V, below the second voltage threshold. At this time, the second switch 26 is turned off. As described above, when the second switch 26 is turned off, the third switch 40 and the first switch 22 are also turned off, and the MOSFET 20 is turned on. Therefore, even when the emitter of the second switch 26 becomes open, the MOSFET 20 remains on.

[0082] <Effects of Drive Unit 11>

[0083] The high-level and low-level voltages output by the microcomputer 30 to the second switch 26 are voltages referenced to the potential of the emitter of the second switch 26. The second switch 26 switches on or off based on the voltage of its base, which is referenced to the emitter potential. Therefore, even if the voltage of the emitter of the second switch 26, which is referenced to the potential of the ground conductor 16, changes, the second switch 26 will switch on or off without error.

[0084] Furthermore, the power supply voltage of DC power supply 10 is sufficiently higher than the maximum voltage at one end of the first conductor 14, which is referenced to the potential of ground conductor 16. Therefore, when the second switch 26 is turned on, a sufficiently large current flows through the third switch resistor 41, and in the third switch 40, the base voltage, referenced to the emitter potential, is lower than the third voltage threshold. As a result, when the second switch 26 is turned on, the third switch 40 is turned on regardless of the voltage at one end of the first conductor 14, which is referenced to the potential of ground conductor 16. As described above, when the third switch 40 is turned on, the first switch 22 is turned on, and the MOSFET 20 is turned off.

[0085] When the second switch 26 is switched off, the current flow through the third switch resistor 41 stops regardless of the voltage at one end of the first wire 14, which is referenced to the potential of the ground conductor 16, and the third switch 40 is switched off. As described above, when the third switch 40 is switched off, the first switch 22 is switched off, and the MOSFET 20 is switched on.

[0086] As described above, when the switching of the second switch 26 is error-free, the switching of the MOSFET 20 also proceeds error-free. As a result, even if the voltage at one end of the first wire 14, which is based on the reference potential of the control signal voltage (i.e., the potential of the ground conductor 16), changes, the MOSFET 20 switches to on or off error-free.

[0087] <Postscript>

[0088] MOSFET20 can be switched on by raising the voltage at the control terminal, which is based on the potential of the output terminal where the current is output. Therefore, it can be replaced by N-channel FET, IGBT (Insulated Gate Bipolar Transistor), or NPN bipolar transistor, which are different from MOSFET.

[0089] (Implementation Method 2)

[0090] In embodiment 1, the number of switches for controlling the power supply to the load 13 is one. However, the number of switches for controlling the power supply to the load 13 is not limited to one, and may be two or more.

[0091] The differences between Embodiment 2 and Embodiment 1 will now be explained. Except for the structures described later, the structures are the same as those in Embodiment 1. Therefore, the same reference numerals are used for the structural parts common to Embodiment 1, and their descriptions are omitted.

[0092] <Overview of Drive Unit 11>

[0093] Figure 4 This is a block diagram showing the main structural components of the drive unit 11 in Embodiment 2. In the power supply system 1 of Embodiment 2, the drive unit 11 drives the motor M as a load 13. The power supply system 1 in Embodiment 2 may also be similar to that in Embodiment 1, without electrical equipment 12. The drive unit 11 has a first upstream switch 50u, a first downstream switch 50d, a second upstream switch 51u, and a second downstream switch 51d. A first current path and a second current path are provided as current paths for the current flowing from the positive terminal of the DC power supply 10 through the motor M.

[0094] In the first current path, a first upstream switch 50u and a first downstream switch 50d are respectively arranged upstream and downstream of the motor M. In the second current path, a second upstream switch 51u and a second downstream switch 51d are respectively arranged upstream and downstream of the motor M. When current flows through the first current path, the direction of the current flowing through the motor M is the first direction. Figure 4 In the middle, it faces downwards. When the current flows through the second current path, the direction of the current flowing through the motor M is the second direction. Figure 4 In the middle, the direction is upward. The first direction is different from the second direction.

[0095] With the second upstream switch 51u and the second downstream switch 51d open, the drive unit 11 switches the first upstream switch 50u and the first downstream switch 50d to open. As a result, current in the first direction flows through the motor M, causing the motor M to rotate in the forward direction. The motor M has a cylindrical rotor. The rotation of the motor M means the rotation of the rotor about its axis. For example, the forward direction is clockwise.

[0096] With the first upstream switch 50u and the first downstream switch 50d open, the drive device 11 switches the second upstream switch 51u and the second downstream switch 51d to open. As a result, current flows through the motor M in the second direction, causing the motor M to rotate in the opposite direction. The forward direction is clockwise, and the reverse direction is counterclockwise.

[0097] Motor M is used, for example, to open and close the windows of a vehicle. When motor M rotates in the forward direction, it opens the vehicle's windows, for example. When motor M rotates in the reverse direction, it closes the vehicle's windows, for example.

[0098] The drive unit 11 switches the first upstream switch 50u and the second upstream switch 51u to the off position. As a result, the power supply from the DC power supply 10 to the motor M stops, and the motor M stops operating.

[0099] <Structure of Drive Unit 11>

[0100] like Figure 4 As shown, in addition to the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d, the driving device 11 also includes a regulator 29, a microcomputer 30, a first upstream driving circuit 52u, a first downstream driving circuit 52d, a second upstream driving circuit 53u, a second downstream driving circuit 53d, and switching resistors 54 and 55. The first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d are each N-channel MOSFETs.

[0101] The DC power supply 10, regulator 29, microcomputer 30, first wire 14, and grounding conductor 16 are connected in the same manner as in Embodiment 1. Multiple electrical devices 12 are connected to one end of the first wire 14. The drain of the first upstream switch 50u is connected to the positive terminal of the DC power supply 10. The source of the first upstream switch 50u is connected to one end of the motor M. The other end of the motor M is connected to the drain of the first downstream switch 50d. The source of the first downstream switch 50d is connected to the grounding conductor 16 via the second wire 15. A switching resistor 54 is connected between the gate and source of the first downstream switch 50d.

[0102] The drain of the second upstream switch 51u is connected to the positive terminal of the DC power supply 10. The source of the second upstream switch 51u is connected to the connection node between the first downstream switch 50d and the motor M. The connection node between the first upstream switch 50u and the motor M is connected to the drain of the second downstream switch 51d. The source of the second downstream switch 51d is connected to the ground conductor 16 via the second wire 15. A switching resistor 55 is connected between the gate and source of the second downstream switch 51d.

[0103] The gates of the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d are each connected to the gates of the first upstream drive circuit 52u, the first downstream drive circuit 52d, the second upstream drive circuit 53u, and the second downstream drive circuit 53d, respectively. The first upstream drive circuit 52u is connected to the microcomputer 30. The connection node between the first upstream drive circuit 52u and the microcomputer 30 is connected to the second downstream drive circuit 53d. The second upstream drive circuit 53u is connected to the microcomputer 30. The connection node between the second upstream drive circuit 53u and the microcomputer 30 is connected to the first downstream drive circuit 52d.

[0104] The microprocessor 30 is further directly connected to the first downstream drive circuit 52d and the second downstream drive circuit 53d, respectively. The first downstream drive circuit 52d and the second downstream drive circuit 53d are each connected to the connection node between the microprocessor 30 and the first wire 14. The first downstream drive circuit 52d is further connected to the source of the first downstream switch 50d. The second downstream drive circuit 53d is further connected to the source of the second downstream switch 51d.

[0105] The first downstream drive circuit 52d and the second downstream drive circuit 53d are each connected to the positive terminal of the DC power supply 10. To avoid making the attached diagrams too complicated, in... Figure 4 The connection lines between them are omitted from the text.

[0106] <Operation of Drive Unit 11>

[0107] Regarding the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d, respectively, when the gate voltage, referenced to the source potential, is above the switching threshold, the resistance between the drain and the source is sufficiently small. At this time, the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d are each turned on, allowing current to flow through the drain and the source.

[0108] Regarding the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d, respectively, when the gate voltage (based on the source potential) is lower than the switching threshold, the resistance between the drain and source is sufficiently large. At this time, the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d are each disconnected, and current does not flow through the drain and source. The switching threshold is a positive constant value and is preset. The switching thresholds of the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d can be the same as or different from the other switching thresholds.

[0109] The microcomputer 30 outputs the right-side control signal to the first upstream drive circuit 52u and the second downstream drive circuit 53d. The microcomputer 30 also outputs the left-side control signal to the second upstream drive circuit 53u and the first downstream drive circuit 52d. Both the right-side and left-side control signals are composed of a high-level voltage and a low-level voltage, respectively. The microcomputer 30 switches the voltages of the right-side and left-side control signals to either a high-level voltage or a low-level voltage. The first upstream drive circuit 52u and the second downstream drive circuit 53d are switched on or off according to the voltage of the right-side control signal. Similarly, the second upstream drive circuit 53u and the first downstream drive circuit 52d are switched on or off according to the voltage of the left-side control signal.

[0110] Figure 5 This is a timing diagram used to illustrate the operation of the drive unit 11. Figure 5 In this diagram, "H" represents a high-level voltage and "L" represents a low-level voltage. The diagram shows the evolution of the control signals on the right and left sides, as well as the evolution of the states of the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d. Time is shown on the horizontal axis to represent these evolutions.

[0111] The voltages for the right-side and left-side control signals have three states. The first state is when the voltages for the right-side and left-side control signals are respectively a high-level voltage and a low-level voltage. The second state is when the voltages for the right-side and left-side control signals are respectively a low-level voltage and a high-level voltage. The third state is when the voltages for the right-side and left-side control signals are both low-level voltages.

[0112] When the right-side control signal switches from a low-level voltage to a high-level voltage, the first upstream drive circuit 52u raises the gate voltage of the first upstream switch 50u, which is referenced to the potential of the ground conductor 16. Consequently, in the first upstream switch 50u, the gate voltage, referenced to the source potential, becomes above the switching threshold, and the first upstream switch 50u switches to ON. Under the same conditions, the second downstream drive circuit 53d lowers the gate voltage, referenced to the source potential, to zero V in the second downstream switch 51d. Consequently, in the second downstream switch 51d, the gate voltage, referenced to the source potential, falls below the switching threshold, and the second downstream switch 51d switches to OFF. Therefore, when the voltage of the right-side control signal is a high-level voltage, the first upstream switch 50u and the second downstream switch 51d are respectively ON and OFF.

[0113] When the left-side control signal switches from a high-level voltage to a low-level voltage, the second upstream drive circuit 53u causes the gate voltage of the second upstream switch 51u, which is referenced to the potential of the ground conductor 16, to decrease. Consequently, in the second upstream switch 51u, the gate voltage, referenced to the source potential, falls below the switching threshold, and the second upstream switch 51u switches off. Under the same conditions, the first downstream drive circuit 52d causes the gate voltage, referenced to the source potential, to increase in the first downstream switch 50d. Consequently, in the first downstream switch 50d, the gate voltage, referenced to the source potential, becomes above the switching threshold, and the first downstream switch 50d switches on. Therefore, when the voltage of the left-side control signal is a low-level voltage, the second upstream switch 51u and the first downstream switch 50d are each turned off and on respectively.

[0114] When the voltages of the right-side control signal and the left-side control signal are respectively high-level and low-level voltages, the first upstream switch 50u and the first downstream switch 50d are turned on, and the second upstream switch 51u and the second downstream switch 51d are turned off. At this time, current flows from the positive terminal of the DC power supply 10 through the first upstream switch 50u, the motor M, the first downstream switch 50d, the second wire 15, and the grounding conductor 16, and returns to the negative terminal of the DC power supply 10. Thus, current in the first direction flows through the motor M, and the motor M rotates in the positive direction.

[0115] When the first upstream switch 50u and the first downstream switch 50d are turned on, the drain current is input to the first upstream switch 50u and the source current is output from the first downstream switch 50d.

[0116] When the right-side control signal switches from a high-level voltage to a low-level voltage, the first upstream drive circuit 52u causes the gate voltage of the first upstream switch 50u, based on the potential of the ground conductor 16, to decrease. Consequently, in the first upstream switch 50u, the gate voltage, based on the source potential, falls below the switching threshold, and the first upstream switch 50u switches off. Under the same conditions, the second downstream drive circuit 53d causes the gate voltage, based on the source potential, to increase in the second downstream switch 51d. Consequently, in the second downstream switch 51d, the gate voltage, based on the source potential, becomes above the switching threshold, and the second downstream switch 51d switches on. Therefore, when the voltage of the right-side control signal is a low-level voltage, the first upstream switch 50u and the second downstream switch 51d are each turned off and on respectively.

[0117] When the left-side control signal switches from a low-level voltage to a high-level voltage, the second upstream drive circuit 53u raises the gate voltage of the second upstream switch 51u, which is referenced to the potential of the ground conductor 16. Consequently, in the second upstream switch 51u, the gate voltage, referenced to the source potential, becomes above the switching threshold, and the second upstream switch 51u switches to ON. Under the same conditions, the first downstream drive circuit 52d lowers the gate voltage, referenced to the source potential, to zero V in the first downstream switch 50d. Consequently, in the first downstream switch 50d, the gate voltage, referenced to the source potential, falls below the switching threshold, and the first downstream switch 50d switches to OFF. Therefore, when the voltage of the left-side control signal is a high-level voltage, the second upstream switch 51u and the first downstream switch 50d are respectively ON and OFF.

[0118] When the voltages of the right-side control signal and the left-side control signal are respectively a low-level voltage and a high-level voltage, the first upstream switch 50u and the first downstream switch 50d are disconnected, and the second upstream switch 51u and the second downstream switch 51d are connected. At this time, current flows from the positive terminal of the DC power supply 10 through the second upstream switch 51u, the motor M, the second downstream switch 51d, the second wire 15, and the grounding conductor 16, and returns to the negative terminal of the DC power supply 10. As a result, current in the second direction flows through the motor M, and the motor M rotates in the opposite direction.

[0119] When the second upstream switch 51u and the second downstream switch 51d are turned on, the drain current is input to the second upstream switch 51u and the source current is output from the second downstream switch 51d.

[0120] When the voltages of the right-side and left-side control signals are at low levels, the first upstream switch 50u and the second upstream switch 51u are open, and the first downstream switch 50d and the second downstream switch 51d are closed. Because the first upstream switch 50u and the second upstream switch 51u are open, no power is supplied to the motor M, and the motor M stops operating.

[0121] Motor M has an inductor (not shown). During the supply of power to motor M, current flows through the inductor, storing energy. When the first downstream switch 50d and the second downstream switch 51d are closed, current flows from one end of motor M through the first downstream switch 50d and the second downstream switch 51d, and motor M releases energy. Figure 5 As shown, when the direction of rotation of motor M is changed, the operation of motor M is temporarily stopped, and motor M releases energy.

[0122] <Structure of the first downstream drive circuit 52d>

[0123] Figure 6This is a circuit diagram of the first downstream drive circuit 52d. The first downstream drive circuit 52d includes circuit resistor 21, a first switch 22, first switch resistors 23 and 24, a switching circuit 25, a second switch 26, second switch resistors 27 and 28, and a circuit switch 60. The switching circuit 25 in Embodiment 2, like in Embodiment 1, includes a third switch 40 and third switch resistors 41 and 42. The connections of circuit resistor 21, first switch 22, first switch resistors 23 and 24, switching circuit 25, second switch 26, second switch resistors 27 and 28, third switch 40, and third switch resistors 41 and 42 are the same as in Embodiment 1.

[0124] One end of circuit switch 60 is connected to the positive terminal of DC power supply 10. The other end of circuit switch 60 is connected to the connection node between circuit resistor 21 and the emitter of third switch 40. The connection node between circuit resistor 21 and the collector of first switch 22 is connected to the gate of first downstream switch 50d. The emitter of first switch 22 is connected to the source of first downstream switch 50d.

[0125] Similar to embodiment 1, the base of the second switch 26 is connected to the microcomputer 30 via the second switch resistor 28, and the emitter of the second switch 26 is connected to one end of the first wire 14.

[0126] As described above, circuit resistor 21 is connected between the positive terminal of DC power supply 10 and the gate of the first downstream switch 50d. The first switch 22 is connected between the gate and source of the first downstream switch 50d.

[0127] <Operation of the first downstream drive circuit 52d>

[0128] The microcomputer 30 switches the circuit switch 60 to either on or off. The microcomputer 30 outputs a left-side control signal to the base of the second switch 26. The high-level and low-level voltages of the left-side control signal are referenced to the emitter of the second switch 26. Therefore, when the circuit switch 60 is on, the second switch 26, the third switch 40, and the first switch 22 switch to either on or off based on the voltage of the left-side control signal.

[0129] With circuit switch 60 on, and the voltage of the control signal on the left side at a low level, the second switch 26, the third switch 40, and the first switch 22 are off, similar to Embodiment 1. With the first switch 22 off, current flows sequentially from the positive terminal of the DC power supply 10 through the circuit resistor 21, the switching resistor 54, the second wire 15, and the ground conductor 16, returning to the negative terminal of the DC power supply 10. A voltage drop is generated at the switching resistor 54. At this time, in the first downstream switch 50d, the gate voltage, referenced to the source potential, is above the switching threshold, and the first downstream switch 50d is on. The power supply voltage is sufficiently greater than the maximum value of the source voltage of the first downstream switch 50d, referenced to the ground conductor 16. Therefore, the magnitude of the voltage drop generated at the switching resistor 54 is above the switching threshold. Therefore, with the first switch 22 off, the first downstream switch 50d reliably switches to on.

[0130] With circuit switch 60 on, and the voltage of the left control signal being high, the second switch 26, the third switch 40, and the first switch 22 are on, similarly to Embodiment 1. With the first switch 22 on, in the first downstream switch 50d, the gate voltage, referenced to the source potential, is zero V, below the switching threshold. As a result, the first downstream switch 50d is off. Similar to Embodiment 1, the power supply voltage is sufficiently greater than the maximum value of the emitter voltage of the first switch 22, referenced to the potential of the ground conductor 16. Therefore, with the second switch 26 on, the voltage drop across the first switch resistor 23 is greater than or equal to the first voltage threshold. Therefore, with the third switch 40 on, the first switch 22 reliably switches on.

[0131] As described above, when circuit switch 60 is turned on, such as Figure 5 As shown, when the voltage of the left-side control signal is low, the first downstream switch 50d is turned on. Under the same conditions, when the voltage of the left-side control signal is high, the first downstream switch 50d is turned off.

[0132] With circuit switch 60 open, no current flows through switch resistor 54 regardless of whether second switch 26 is closed, i.e., regardless of the voltage of the control signal on the left. Therefore, with circuit switch 60 open, the gate voltage in the first downstream switch 50d, referenced to the source potential, is zero V, which is below the switching threshold. Therefore, the first downstream switch 50d is open.

[0133] Therefore, when the microcomputer 30 switches the voltage of the left control signal to a low level and switches the circuit switch 60 to open, it can switch the second upstream switch 51u and the first downstream switch 50d to open.

[0134] <Second downstream drive circuit 53d>

[0135] The second downstream drive circuit 53d is configured in the same way as the first downstream drive circuit 52d. By replacing the first downstream switch 50d with the second downstream switch 51d in the description of the connection of the first downstream drive circuit 52d, the connection of the second downstream drive circuit 53d can be explained.

[0136] The operation of the second downstream drive circuit 53d is the same as that of the first downstream drive circuit 52d. By replacing the left-side control signal, the first downstream switch 50d, and the switching resistor 54 with the right-side control signal, the second downstream switch 51d, and the switching resistor 55 respectively in the explanation of the operation of the first downstream drive circuit 52d, the operation of the second downstream drive circuit 53d can be explained. The voltage of the right-side control signal is based on the potential of the emitter of the second switch 26 in the second downstream drive circuit 53d.

[0137] Therefore, when circuit switch 60 is on, the second downstream switch 51d is on when the voltage of the right-side control signal is low. Under the same conditions, the second downstream switch 51d is off when the voltage of the right-side control signal is high. When the microcomputer 30 switches the voltage of the right-side control signal to low and switches circuit switch 60 of the second downstream drive circuit 53d to off, it can switch the first upstream switch 50u and the second downstream switch 51d to off.

[0138] The microcomputer 30 switches the voltages of the right-side control signal and the left-side control signal to a low-level voltage, and switches the circuit switches 60 of the first downstream drive circuit 52d and the second downstream drive circuit 53d to open. This enables the first upstream switch 50u, the first downstream switch 50d, the second upstream switch 51u, and the second downstream switch 51d to be in an open state.

[0139] With circuit switch 60 on, when the emitters of the second switches 26 in the first downstream drive circuit 52d and the second downstream drive circuit 53d become open, the second switches 26 switch off. Therefore, the first downstream switches 50d and the second downstream switches 51d switch on. As a result, the voltage across the motor M becomes the same, and the motor M stops operating.

[0140] <Effects of Drive Unit 11>

[0141] The drive device 11 in Embodiment 2 also functions as the drive device 11 in Embodiment 1. Therefore, when the circuit switch 60 is on, even if the voltage at one end of the first wire 14, which is based on the reference potential of the voltages of the right-side control signal and the left-side control signal (i.e., the potential of the ground conductor 16), changes, the first downstream switch 50d and the second downstream switch 51d will switch on or off without error. When the circuit switch 60 is off, regardless of the voltage at one end of the first wire 14, which is based on the potential of the ground conductor 16, both the first downstream switch 50d and the second downstream switch 51d will be off.

[0142] <Postscript>

[0143] In Embodiment 2, the first upstream switch 50u and the second upstream switch 51u each function as switches. Therefore, they are not limited to N-channel MOSFETs, but can also be N-channel FETs, P-channel FETs, IGBTs, bipolar transistors, or relay contacts, etc., which are different from MOSFETs. The first downstream switch 50d and the second downstream switch 51d each switch to be turned on by raising the voltage of the control terminal based on the potential of the output terminal where the current is output. Therefore, the first downstream switch 50d and the second downstream switch 51d are not limited to N-channel MOSFETs, but can also be N-channel FETs, IGBTs, or NPN bipolar transistors, etc., which are different from MOSFETs. In Embodiment 2, the load driven by the drive device 11 is not limited to the motor M, but can be any electrical device that switches the direction of DC voltage application.

[0144] In Embodiment 1, similarly to Embodiment 2, a resistor can be connected between the gate and source of MOSFET 20. In this case, when the first switch 22 is open, current flows from the positive terminal of DC power supply 10 through circuit resistor 21, resistor, and ground conductor 16, and returns to the negative terminal of DC power supply 10. Due to the voltage drop generated at the resistor, the gate voltage, referenced to the source potential, is above the gate threshold in MOSFET 20, and MOSFET 20 is turned on.

[0145] In embodiments 1 and 2, the first switch 22 and the second switch 26 can each be switched on by raising the voltage of the control terminal, which is based on the potential of the output terminal where the current is output. Therefore, the first switch 22 and the second switch 26 are not limited to NPN bipolar transistors, but can also be N-channel FETs or IGBTs, etc.

[0146] Furthermore, in embodiments 1 and 2, the third switch 40 can be any switch that is switched on by lowering the voltage of the control terminal, which is based on the potential of the output terminal where the current is output. Therefore, the third switch 40 is not limited to a PNP type bipolar transistor; for example, it can also be a P-channel type FET. The number of electrical devices 12 included in the power supply system 1 in embodiments 1 and 2 is not limited to 2 or more; it can also be 1.

[0147] 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.

[0148] Explanation of reference numerals in the attached figures

[0149] 1 Power System

[0150] 10 DC power supply

[0151] 11. Drive unit

[0152] 12 Electrical equipment

[0153] 13 Load

[0154] 14 First Conductor

[0155] 14A Inductor

[0156] 14b Wire resistance

[0157] 15 Second conductor

[0158] 16 Grounding conductor

[0159] 20 MOSFET

[0160] 21 Circuit Resistance

[0161] 22 First Switch

[0162] 23 First switch resistor (second resistor)

[0163] 24 First Switch Resistor

[0164] 25 Switching Circuit

[0165] 26 Second Switch

[0166] 27, 28 Second switching resistors

[0167] 29 Regulator

[0168] 30. Microcomputer (output section)

[0169] 40 Third Switch

[0170] 41. Third Switch Resistor (Third Resistor)

[0171] 42 Third Switch Resistor

[0172] 50d First downstream switch

[0173] 50u First upstream switch

[0174] 51d Second Downstream Switch

[0175] 51u Second Upstream Switch

[0176] 52d First downstream drive circuit

[0177] 52u First upstream drive circuit

[0178] 53d Second downstream drive circuit

[0179] 53u Second upstream drive circuit

[0180] 54, 55 Switching resistors

[0181] 60 Circuit Switch

[0182] M Motor (Load).

Claims

1. A driving device for driving a load, The drive device includes: An N-channel MOSFET is positioned downstream of the load in the current path of the current flowing through the load. A resistor is connected between the DC power supply and the gate of the MOSFET; The first switch is connected between the gate and source of the MOSFET; The second switch is turned on when the voltage at the control terminal, which is based on the potential of the output terminal where the current is output, is above a threshold. The switching circuit switches the first switch to the on and the MOSFET to the off when the second switch is on, and switches the first switch to the off and the MOSFET to the on when the second switch is off. and The output section outputs a voltage based on the potential of the output terminal of the second switch to the control terminal of the second switch.

2. The driving device according to claim 1, wherein, The output terminal of the second switch is connected to the grounding conductor via the first wire. The source of the MOSFET is connected to the ground conductor via a second wire.

3. The driving device according to claim 1 or 2, wherein, The first switch is turned on when the voltage at the control terminal, which is based on the potential of the output terminal where the current is output, is above the second threshold. The driving device includes a second resistor connected between the control terminal and the output terminal of the first switch. The input terminal of the first switch, to which current is input, is connected to the gate of the MOSFET. The output terminal of the first switch is connected to the source of the MOSFET. The switching circuit has: The third switch is turned on when the voltage at the control terminal, which is based on the potential of the input terminal where the current is input, is lower than the third threshold. and The third resistor is connected between the control terminal and the input terminal of the third switch. The input terminal of the third switch is connected to the DC power supply. The output terminal of the third switch, from which current is output, is connected to the control terminal of the first switch. The control terminal of the third switch is connected to the input terminal of the second switch into which current is input.

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