Load drive device

Abstract

This invention provides a method to prevent large currents from flowing during normal load drive control when the load is short-circuited. The load drive device (100) includes: drive switches (61, 62) for switching the current supplied from the power source to the load (70) on or off; a switch drive circuit (20) for sending drive signals to the drive switches (61, 62) based on control commands from the arithmetic unit (10); and a constant current source (40) for supplying current to the load (70) without passing through the drive switches (61, 62). Furthermore, when the drive switches (61, 62) are off and current is supplied from the constant current source (40) to the load (70), the switch drive circuit (20) controls the load (70) to be off when the voltage across the load (70) is below a predetermined value.

Description

Technical Field

[0001] This invention relates to a load driving device for driving loads, and particularly to a technique for protecting the circuitry of the load driving device. Background Technology

[0002] As a circuit protection mechanism for a load drive device, such as in the abnormal detection device for a fuel injection valve in Patent Document 1, there is a known technique in which a constant current source is provided downstream of the fuel injection valve, and an abnormality of the fuel injection valve is detected based on the potential difference generated at a predetermined part of the circuit when the current provided does not reach the level of fuel injection.

[0003] Furthermore, in the method and apparatus for diagnosing a fault in a fuel injection device in Patent Document 2, the following technique is known: generating a constant current such that the fuel injection valve does not operate, detecting the current value when the fuel injection device is energized, thereby detecting a fault in the fuel injection device.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 6-65864

[0007] Patent Document 2: Japanese Patent Application Publication No. 10-252539 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, in the event of a short-circuit fault at the load (fuel injection valve side), if normal control is performed only through diagnostics, there is no load-limited current, and the circuit becomes low-resistance, thus causing excessive current to flow into the circuit, which in the worst case leads to circuit damage or burnout.

[0010] Furthermore, when using current value diagnosis in load drive control based on existing technology, and the diagnosis indicates a load short circuit, even when the method for disabling the operation of the load drive device is implemented, the load becomes a low-resistance load due to the short circuit condition, compared to the normal load. Therefore, a large current flows in the circuit of the load drive device from the time the diagnosis is confirmed until the operation of the load drive device is disabled.

[0011] Therefore, the driver used in the load drive is not the driver that can withstand the absolute maximum rated value of the current value used in normal load drive, but rather the driver that needs to be selected that can withstand the absolute maximum rated value of the large current flowing through the load drive before using diagnostics to disable the operation of the load drive when the load is short-circuited and under normal control.

[0012] Based on the above situation, it is desirable to have a method that can prevent large currents from flowing during normal load drive control when the load is short-circuited.

[0013] Technical means to solve the problem

[0014] To address the aforementioned issues, one aspect of the load driving device of the present invention includes: a drive switch that connects or disconnects current supplied from a power source to a load; a switch driving circuit that sends a drive signal to the drive switch based on a control command from an arithmetic device; and a constant current source that supplies current to the load without passing through the drive switch. Furthermore, when the drive switch is open and current is supplied to the load from the constant current source, the switch driving circuit controls the load to prevent the drive switch from being turned on if the voltage across the load falls below a predetermined value.

[0015] In other embodiments of the present invention, the load driving device includes: a drive switch that connects or disconnects the current supplied from the power source to the load; a switch driving circuit that sends a drive signal to the drive switch based on a control command from a computing device; and a constant current source that supplies current to the load without passing through the drive switch, wherein multiple different determination values ​​are set as determination values. Furthermore, when the drive switch is open and current is supplied to the load from the constant current source, the switch driving circuit determines which range of the range divided by the multiple determination values ​​the voltage across the load falls within, and notifies the computing device of the determination result, which then performs control corresponding to the determination result.

[0016] The effects of the invention

[0017] According to at least one embodiment of the present invention, when the load is short-circuited, the short-circuit fault is diagnosed and the operation of the load drive device is prohibited before load drive control is performed, thereby preventing large currents from flowing during normal load drive control.

[0018] Other issues, structures, and effects not mentioned above will be clarified through the following description of the implementation methods. Attached Figure Description

[0019] Figure 1 This is a circuit diagram illustrating an example configuration of the load drive device according to the first embodiment of the present invention.

[0020] Figure 2 This is a timing diagram showing the operation and signals of each part of the load drive device according to the first embodiment of the present invention.

[0021] Figure 3 This is a circuit diagram illustrating other configuration examples of the load drive device according to the first embodiment of the present invention.

[0022] Figure 4 This is a circuit diagram illustrating an example configuration of the load drive device according to the second embodiment of the present invention.

[0023] Figure 5 This is a timing diagram showing the operation and signals of each part of the load drive device according to the second embodiment of the present invention.

[0024] Figure 6 This is a flowchart illustrating an example of the diagnostic and control steps of the load drive device according to the second embodiment of the present invention.

[0025] Figure 7 This is a circuit diagram illustrating an example configuration of the load drive device according to the third embodiment of the present invention.

[0026] Figure 8 This is a timing diagram showing the operation and signals of each part of the load drive device according to the third embodiment of the present invention.

[0027] Figure 9 This is a circuit diagram illustrating an example configuration of the load drive device according to the fourth embodiment of the present invention. Detailed Implementation

[0028] Hereinafter, examples of embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In this specification and drawings, constituent elements having substantially the same function or structure are given the same reference numerals and repeated descriptions are omitted.

[0029] <First Implementation>

[0030] First, the configuration of the load drive device according to the first embodiment of the present invention will be described.

[0031] Figure 1 This is a circuit diagram illustrating a configuration example of the load drive device 100 according to the first embodiment. The load drive device 100 consists of an electronic control unit 1 and an injector circuit 90 that drives the injector 70 according to control commands from the electronic control unit 1. The electronic control unit 1 is, for example, an ECU (Electronic Control Unit) that controls the controlled device mounted on a vehicle. The injector 70 is a fuel injection device that directly injects fuel into the combustion chamber of an internal combustion engine, and is an example of a load. The injector circuit 90 can be built into the electronic controller 1.

[0032] The electronic control device 1 includes an arithmetic unit 10, a memory 11, and a pre-driver circuit 20.

[0033] The arithmetic unit 10 may use a processor such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The memory 11 may be a semiconductor memory such as ROM or RAM. The arithmetic unit 10 implements the functions of the electronic control unit 1, i.e., the load drive unit 100, by reading and executing the computer program stored in the memory 11.

[0034] The pre-driver circuit 20 (an example of a switch drive circuit) includes a controller 30, an internal constant current source 40, and a voltage monitoring circuit 50.

[0035] The controller 30 controls the overall operation of the pre-driver circuit 20 based on control commands output from the arithmetic unit 10. For example, based on the control commands from the arithmetic unit 10, the controller 30 generates drive signals to be sent to the valve opening driver 62 and the holding driver 61 of the injector circuit 90. In addition, based on the drive signals for the valve opening driver 62 and the holding driver 61, the controller 30 generates commands to control the energization and de-energization of the internal constant current source 40.

[0036] An internal constant current source 40 (an example of a constant current source) is connected to the upstream side of the injector 70 (load), i.e., the source side of the valve-opening driver 62 and the holding driver 61. The internal constant current source 40 generates a constant current supplied to the injector 70 based on a voltage Vint obtained from any power source, according to instructions from the controller 30. For example, a reference voltage VB supplied by a battery (not shown) can also be used as the voltage Vint. In this embodiment, the constant current generated by the internal constant current source 40 is not supplied to the injector 70 via the valve-opening driver 62 and the holding driver 61. Alternatively, the internal constant current source 40 may be located outside the pre-driver circuit 20.

[0037] Voltage monitoring circuit 50 and injector 70 ( Figure 1 The two ends of the excitation coil shown are connected to the voltage applied across the injector 70 (voltage across both ends), and the voltage monitoring circuit 50 includes a differential voltage measuring device 51, a voltage comparison result calculation circuit 55, and a judgment value table 56.

[0038] The differential voltage measuring device 51 measures the differential voltage (monitoring voltage) corresponding to the voltage across the injector 70 and outputs the measurement result to the voltage comparison result calculation circuit 55.

[0039] The judgment value table 56 stores the voltage value, which is predetermined as the comparison reference for fault diagnosis, as the judgment value. In addition, in this embodiment, the judgment value table 56 stores predetermined fixed values, but since the resistance value is predicted to vary depending on the driven load, it is also possible to freely change the composition of the judgment values ​​in the judgment value table 56.

[0040] The voltage comparison result calculation circuit 55 compares the judgment value stored in the judgment value table 56 with the differential voltage measured by the differential voltage measuring device 51, and makes a judgment on the comparison result. The voltage comparison result calculation circuit 55 outputs the judgment result to the controller 30, and the controller 30 controls the drive of the injector 70 according to the judgment result.

[0041] The injector circuit 90 includes: a holding driver 61 (first drive switch) that turns on or off the current supplied to the injector 70 from a power source (reference voltage VB) such as a battery (not shown); and a valve opening driver 62 (second drive switch) that turns on or off the current supplied to the injector 70 from a boost circuit 63 that generates a high voltage (valve opening voltage VH) based on the power source voltage (reference voltage VB). The holding driver 61 and the valve opening driver 62 use switching elements such as MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors).

[0042] These drive switches (holding driver 61, valve opening driver 62) are configured upstream of the load in the direction of current flow from the power source (e.g., a battery with reference voltage VB) to the load (injector 70). This allows switching the load's energization / de-energization from the upstream side. Furthermore, an injector current monitoring resistor 80 is connected between the downstream side of the injector 70 and the ground terminal.

[0043] Additionally, an operation display device 150 is connected to the arithmetic unit 10 of the electronic control device 1 via an input / output interface (not shown). The operation display device 150 includes a display unit 151 and an operation unit 152. The display unit 151 displays information output from the arithmetic unit 10 indicating the status of the load drive device 100. The display unit 151 may be, for example, an indicator light (warning light) or a liquid crystal panel. The operation unit 152 generates input signals corresponding to user operations and outputs them to the arithmetic unit 10. The arithmetic unit 10 performs calculations and controls corresponding to the input signals. For example, the operation display device 150 may be a portable information processing device (PC) such as a tablet computer.

[0044] In addition, the load drive device 100 can be a high-side drive mode that connects or disconnects the load (injector 70) on the power supply side, but it can also be a low-side drive mode that connects or disconnects the load (injector 70) on the ground side.

[0045] Figure 2 It is a timing diagram showing the operation and signals of each part of the load drive device 100.

[0046] In the load drive device 100, the arithmetic unit 10 inputs a control command signal (signal 101) to the pre-drive circuit 20 via the pre-drive control command line 5. Upon receiving the control command signal, the pre-drive circuit 20 energizes the injector 70 (load) by controlling the valve opening driver 62 and the holding driver 61 from the controller 30 (signals 102, 103).

[0047] The control command signal includes an opening current control signal and a holding current control signal. The opening current control signal is used to control the current applied to the excitation coil in order to open the injector 70. This is equivalent to, for example, in... Figure 2 In the INJ current shown in waveform 105, the current rises from its peak value until it becomes a constant value. The holding current control signal controls the current applied to the excitation coil to maintain the open valve state of the injector 70 for a certain period of time. This is equivalent to, for example, in... Figure 2 The constant current value is a lower value after the peak value of the INJ current, as shown in waveform 105.

[0048] Within the injector circuit 90, the current flowing to the injector 70 is monitored by an injector current monitoring resistor 80 connected to the downstream side of the injector 70. The pre-driver circuit 20 controls the current supplied to the injector 70 based on the current detected by the injector current monitoring resistor 80.

[0049] In addition, the controller 30, together with the valve opening actuator 62 and the holding actuator 61, also controls the internal constant current source 40 and the voltage monitoring circuit 50. The controller 30 turns on the internal constant current source 40 via the internal constant current source control line 41 (signal 104), thereby energizing the injector 70. In this embodiment, when the controller 30 does not control the valve opening actuator 62 and the holding actuator 61 (during periods other than the monitoring prohibition period T), the internal constant current source 40 is turned on to energize the injector 70. Furthermore, during the period when the injector 70 is energized from the internal constant current source 40, the voltage across the injector 70 is monitored by the voltage monitoring circuit 50, thereby performing fault diagnosis (also simply referred to as "diagnosis").

[0050] The internal constant current source 40 supplies current to the injector 70 according to the control of the controller 30. The current supplied by the internal constant current source 40 to the injector 70 is a weak current that is smaller than the current flowing through the injector 70 when the injector 70 is driven (current threshold Ith), that is, a weak current to the extent that the injector 70 does not open the valve.

[0051] In this embodiment, the injector 70 is assumed to be the load, and the current output by the internal constant current source 40 is a weak current at the level of not opening the valve. However, as the actual driven load, various loads such as motors, relays, and valves are assumed. The weak current is the current at the level of these loads not operating, and the value of the weak current varies depending on the type and characteristics of the driven load.

[0052] When the internal constant current source 40 is energized by the controller 30, the voltage monitoring circuit 50 monitors the voltage applied across the injector 70 via the differential voltage measuring device 51.

[0053] The monitoring voltage (waveform 106) obtained by the differential voltage measuring device 51 is output to the voltage comparison result calculation circuit 55 and compared with the judgment value stored in the judgment value table 56. Here, since the current flowing through the injector 70 is constant due to the internal constant current source 40, the voltage across the injector 70 is determined by the resistance value of the injector 70 according to Ohm's law. Therefore, for example, in the case of a short circuit fault (short circuit) in the injector 70, the resistance value of the injector 70 is significantly smaller than before the fault, and the voltage across the injector 70 also decreases proportionally to the resistance value of the injector 70 during the short circuit.

[0054] Therefore, the judgment value (voltage threshold Vth) stored in the judgment value table 56 is predetermined based on the resistance value of the injector 70 under normal conditions and the constant current value of the internal constant current source 40. If the measurement result obtained by the differential voltage meter 51 (voltage across the injector 70) is below the judgment value (voltage threshold Vth) in the judgment value table 56, it is assumed that the resistance value of the injector 70 is small, i.e., an abnormal state (e.g., a short circuit fault). Therefore, the voltage comparison result calculation circuit 55 outputs a load stop command (signal 107) to the controller 30 via the load stop command line 21. Conversely, if the measurement result obtained by the differential voltage meter 51 is larger than the judgment value (voltage threshold Vth) in the judgment value table 56, it is assumed that the resistance value of the injector 70 is large, i.e., normal.

[0055] Upon receiving a load stop command, the controller 30 disables the output of the on / off control for the valve opening actuator 62 and the holding actuator 61. In other words, the controller 30 disconnects the valve opening actuator 62 and the holding actuator 61. This ensures that the valve opening actuator 62 and the holding actuator 61 are not connected.

[0056] (Voltage amplifier circuit)

[0057] Furthermore, in this embodiment, it is assumed that the differential voltage obtained by the differential voltage measuring device 51 is directly output to the voltage comparison result calculation circuit 55. However, if the load resistance of the injector 70 is small or the current supplied from the internal constant current source 40 is weak, the value of the differential voltage obtained by the differential voltage measuring device 51 will be very small, and based on the resolution of the voltage comparison result calculation circuit 55, it may not be able to make a proper judgment. Therefore, as... Figure 3 As shown, it is also possible to configure a voltage amplifier circuit 52 for amplifying the differential voltage obtained by the differential voltage measuring device 51 between the differential voltage measuring device 51 and the voltage comparison result calculation circuit 55.

[0058] As described above, the load drive device (load drive device 100) of the first embodiment includes: a drive switch (valve opening driver 62, holding driver 61) that turns on or off the current supplied from a power source (e.g., a battery with a reference voltage VB) to the load (injector 70); a switch drive circuit (pre-driver circuit 20) that sends a drive signal to the drive switch based on a control command (signal 101) from an arithmetic unit (arithmetic unit 10); and a constant current source (internal constant current source 40) that supplies current to the load without passing through the drive switch. Furthermore, the switch drive circuit is configured to, when the drive switch is off (during periods other than the monitoring prohibition period T) and current (waveform 105) is supplied to the load from the constant current source, control to prevent the drive switch from turning on when the voltage across the load falls below a determination value (voltage threshold Vth).

[0059] According to the first embodiment of the load drive device configured as described above, the short circuit fault is diagnosed and the operation of the load drive device is prohibited before load drive control is performed when the load is short-circuited, thus preventing the large current flowing during normal load drive control.

[0060] That is, in the load drive device 100 described above, when the valve opening driver 62 or the holding driver 61 is disconnected, a constant current from the internal constant current source 40 of the pre-driver circuit 20 is supplied to the injector 70. Then, the voltage across the injector 70 is monitored by the voltage monitoring circuit 50 of the pre-driver circuit 20, and the monitored voltage is compared with the judgment value in the judgment value table 56 to determine a short circuit fault in the injector 70. Here, in the case of a short circuit fault in the injector 70, the pre-driver circuit 20 prohibits the connection control of the valve opening driver 62 and the holding driver 61. Thus, when the injector 70 becomes low-resistance due to a short circuit fault, a large current can be prevented from flowing through the circuit by controlling the connection of the valve opening driver 62 or the holding driver 61.

[0061] Therefore, when a short circuit fault occurs in the injector 70, the switch-on valve actuator 62 and the holding actuator 61 are switched on to prevent abnormal heating of the circuit caused by the large current flowing through, thereby preventing circuit failure.

[0062] Furthermore, since it is possible to prevent large currents from flowing before the load drive is stopped during diagnostics after the operation of existing load drives, the absolute maximum rating of the driver used in the control can be smaller than before. Therefore, smaller and less expensive components can be selected as the driver.

[0063] Furthermore, the controller 30 and voltage monitoring circuit 50, which are configured in hardware to pre-drive circuit 20, perform load stop control when the load drive is stopped. Thus, compared with the load stop control performed by the arithmetic unit 10 based on the comparison result of the monitored voltage, the load can be stopped quickly.

[0064] Furthermore, in the above embodiment, the drive switch is composed of a first drive switch (holding driver 61) and a second drive switch (valve opening driver 62). The first drive switch turns on or off the current supplied from the power supply to the load (coil of the injector 70) (waveform 105), and the second drive switch turns on or off the current supplied from the boost circuit (boost circuit 63) that boosts the voltage of the power supply to the load (waveform 105). Moreover, the switch drive circuit (pre-driver circuit 20) is configured such that, in the state where the first and second drive switches are off and current is supplied to the load from the constant current source (waveform 105), if the voltage across the load is below a predetermined value (voltage threshold Vth), it controls the first and second drive switches to remain off.

[0065] According to this embodiment with the above configuration, even when the load drive device is equipped with a first drive switch and a second drive switch used to connect / disconnect different currents, the same effect as the above configuration can be obtained. That is, before performing load drive control when the load is short-circuited, the short-circuit fault is diagnosed and the operation of the load drive device is prohibited, thus preventing large currents from flowing during normal load drive control.

[0066] Furthermore, in the above embodiment, the switch drive circuit (pre-driver circuit 20) is configured to generate commands (signals 104) for controlling the energization and de-energization of the constant current source (internal constant current source 40) based on the drive signals for the drive switches (valve opening driver 62, holding driver 61).

[0067] Based on the above configuration, during the period when the drive signals (signals 102, 103) for the drive switches (valve opening driver 62, holding driver 61) are off, the energization and de-energization of the load from the constant current source are controlled. Therefore, it is possible to prevent large currents from flowing during energization under normal load drive control.

[0068] Furthermore, in the above embodiment, the constant current source (internal constant current source 40) is configured to supply a current (waveform 105) to the load when the load is not driven, which is smaller than the current (current threshold Ith) flowing to the load when the load (ejector 70) is driven.

[0069] Based on the above configuration, during fault diagnosis, a current (waveform 105) smaller than the current flowing to the load (current threshold Ith) when the load (ejector 70) is not driven is supplied to the load when it is not driven. Therefore, during fault diagnosis, it is possible to prevent the load from being driven even when it is not normally driven.

[0070] Furthermore, in the above embodiment, the switch drive circuit (pre-driver circuit 20) includes: a controller (controller 30) that generates drive signals for driving switches (valve opening driver 62, holding driver 61) based on control commands (signal 101); a constant current source (internal constant current source 40); and a voltage monitoring circuit (voltage monitoring circuit 50) that monitors the voltage across the load (injector 70) and determines whether the voltage across the load is below a determination value (voltage threshold Vth). The controller is configured such that, in a state where the drive switch is off and current (waveform 105) is supplied to the load from the constant current source, if the voltage monitoring circuit determines that the voltage across the load is below the determination value (voltage threshold Vth), it does not send a drive signal indicating an on state to the load and stops the load.

[0071] Furthermore, in the above embodiment, the switch drive circuit (pre-driver circuit 20) can control the energization and de-energization of the constant current source (internal constant current source 40) at any time during the period when the drive switch (valve opening driver 62, holding driver 61) is off (the period other than the monitoring prohibition period T).

[0072] For example, in Figure 1 In the load drive device 100 shown, due to the influence of the inductive and capacitive components within the injector circuit 90, it may not be possible to perform diagnostics immediately after the internal constant current source 40 is turned on. Therefore, during the period when the control commands (valve opening driver 62, holding driver 61) are off ( Figure 2 The signals 102 and 103 are intended to be configured to control the energization and de-energization of the constant current source (internal constant current source 40) at any time.

[0073] <Second Implementation Method>

[0074] The load drive device of the second embodiment differs from the load drive device of the first embodiment in that the decision value table 56 has multiple decision values ​​and that it has a decision counter 57.

[0075] Figure 4 This is a circuit diagram showing a configuration example of the load drive device 100a according to the second embodiment. The load drive device 100a is in Figure 1 The load drive device 100 shown is configured with a decision counter 57, a comparison result transmission line 22, and a pre-driver diagnostic information transmission line 6. That is, the pre-driver circuit 20A within the electronic control device 1 includes a controller 30, an internal constant current source 40, and a voltage monitoring circuit 50A. Figure 4 In the middle, the following was omitted. Figure 1 The description of the boost circuit 63 shown.

[0076] The voltage monitoring circuit 50A includes a differential voltage measuring device 51, a voltage amplification circuit 52, and a voltage comparison result calculation circuit 55A. The voltage amplification circuit 52 can be omitted depending on the magnitude of the input voltage. Furthermore, the voltage comparison result calculation circuit 55A includes a judgment value table 56 and a judgment counter 57.

[0077] Judgment value table 56 can set multiple different judgment values ​​according to the abnormal state (in Figure 5 The judgment values ​​are 1, n, and n+1. Furthermore, the configuration is as follows: the user operates the operation unit 152, which can arbitrarily select from a plurality of judgment values ​​that can be set in the judgment value table 56 a judgment value (specified judgment value) to prohibit the on / off control of the valve opening actuator 62 and the holding actuator 61. The arithmetic unit 10 displays the selectable judgment values ​​on the display unit 151 of the operation display device 150, and the user selects an appropriate judgment value (specified judgment value) from the plurality of judgment values ​​according to an abnormal state. In addition, the judgment value table 56 also records a predetermined number of times for determining that the voltage at both ends of the injector 70 falls within a predetermined range.

[0078] The voltage comparison result calculation circuit 55A determines which range of the voltage (differential voltage) across the injector 70 (load) obtained from the differential voltage meter 51 falls within, according to the range defined by multiple judgment values ​​set in the judgment value table 56. Furthermore, it is configured to transmit the judgment result of the voltage comparison result calculation circuit 55A to the arithmetic unit 10 using the pre-driver diagnostic information transmission line 6.

[0079] As described above, in the first embodiment, even if the voltage comparison result calculation circuit 55A determines an abnormal state once, the voltage comparison result calculation circuit 55A disables the load drive of the controller 30 of the pre-driver circuit 20A. However, in a single abnormal determination, even if no fault has occurred but an abnormal state is mistakenly determined only once due to unwanted external noise, the operation of the injector circuit 90 will be stopped.

[0080] Furthermore, if the resistance value of the injector 70 decreases due to deterioration of the injector 70, or if the resistance value of the injector 70 decreases due to a minor fault in the injector 70 (a circuit fault caused by a large current flowing through the injector circuit 90 without abnormal heating), the operation of the injector circuit 90 will be stopped even if the operation is not intended to be stopped.

[0081] Therefore, in the second embodiment, by providing a determination counter 57 within the voltage monitoring circuit 50A, the number of abnormal states can be counted. For example... Figure 6 As shown in the flowchart, the configuration is such that the monitored voltage is compared with the judgment value, and the load stop command is output to the controller 30 only when the number of times the abnormal state is judged reaches a certain number.

[0082] Furthermore, in this embodiment, the specified number of times is assumed to be a predetermined value, but it is assumed that the specified number of times is set to an arbitrary number. In addition, as a counting method for the determination counter 57, in addition to the method of counting once each time an abnormal state is determined, a method of starting to count when two or more consecutive abnormal states continue can also be considered.

[0083] Alternatively, one could consider resetting the count value after counting abnormal states multiple times, in the event that no abnormal states are counted within a certain period.

[0084] Figure 5 It is a timing diagram showing the operation and signals of each part of the load drive device 100A.

[0085] In the load drive device 100A, a control command signal (signal 101) is input from the arithmetic unit 10 to the pre-drive circuit 20. Upon receiving the control command signal, the pre-drive circuit 20A controls the opening valve driver 62 and the holding driver 61 to be switched on from the controller 30. Figure 2 Signals 102 and 103 energize the injector 70 (load).

[0086] Here, with the internal constant current source 40 energized by the controller 30 (signal 104), the voltage monitoring circuit 50A monitors the voltage applied across the injector 70 via the differential voltage measuring device 51. The monitored voltage (waveform 106) obtained by the differential voltage measuring device 51 is output to the voltage comparison result calculation circuit 55 and compared with multiple judgment values ​​1, n, and n+1 stored in the judgment value table 56. As an example, a case where the monitored voltage is below the judgment value n is considered abnormal.

[0087] exist Figure 5 In the first instance, since the monitored voltage value when the internal constant current source 40 is turned on is greater than the judgment value n+1, the voltage comparison result calculation circuit 55A outputs the comparison result "normal" to the judgment counter 57. Conversely, since the monitored voltage value when the internal constant current source 40 is turned on for the second time is within the range of judgment value 1 and judgment value n, but below judgment value n, the voltage comparison result calculation circuit 55A outputs the comparison result "abnormal" to the judgment counter 57.

[0088] The determination counter 57 counts the number of times the voltage comparison result calculation circuit 55A determines that the monitored voltage belongs to a predetermined range (e.g., an abnormal state) within a range divided by multiple determination values. Therefore, as... Figure 5 As shown, the determination counter 57 does not count (count value "m") when it receives the first comparison result "normal", and counts the value from "m" up to "m+1" when it receives the second comparison result "abnormal".

[0089] Then, the voltage monitoring circuit 50A uses the pre-driver diagnostic information transmission line 6 to transmit the judgment result of the voltage comparison result calculation circuit 55A to the arithmetic unit 10 each time.

[0090] Figure 6 This is a flowchart illustrating the diagnostic and control steps of the load drive device 100A.

[0091] First, the voltage comparison result calculation circuit 55A of the voltage monitoring circuit 50A compares the voltage (monitoring voltage) across the injector 70 with multiple judgment values ​​and calculates the comparison result (S1).

[0092] Next, the voltage comparison result calculation circuit 55A determines whether the monitored voltage is below a specified judgment value based on the comparison result (S2). The specified judgment value refers to the judgment value among multiple judgment values ​​that prohibits the on-state control of the valve opening driver 62 and the holding driver 61, which in the above example is equivalent to judgment value n. Here, if the monitored voltage is not below the specified judgment value (S2 no), the voltage comparison result calculation circuit 55A does not issue a load stop command to the controller 30 and continues the load drive control (S3).

[0093] On the other hand, when the monitored voltage is below the specified judgment value (S2), the voltage comparison result calculation circuit 55A increments the count of the number of times the monitored voltage, counted by the judgment counter 57, is below the judgment value (S4).

[0094] Next, the voltage comparison result calculation circuit 55A determines whether the number of times the monitored voltage has fallen below the judgment value has reached a predetermined number (S5). Then, if the number of times the monitored voltage has fallen below the judgment value has not reached the predetermined number (S5 no), the voltage comparison result calculation circuit 55A does not issue a load stop command to the controller 30 and continues load drive control (S6).

[0095] Alternatively, in parallel with steps S3 and S6, the determination result (the range of the monitored voltage and the count value of the determination counter 57) of the voltage comparison result calculation circuit 55A can be notified to the arithmetic unit 10 using the pre-driver diagnostic information transmission line 6. The arithmetic unit 10 then outputs the determination result to the display unit 151.

[0096] On the other hand, if the monitored voltage falls below the judgment value a predetermined number of times (as in S5), the voltage comparison result calculation circuit 55A outputs a load stop command to the controller 30 via the load stop command line 21 (S7). After processing in steps S3, S6, or S7, the process returns to step S1 and repeats a series of processes.

[0097] In addition, Figures 4-6 In the example shown, the voltage comparison result calculation circuit 55A has a configuration that sets multiple judgment values ​​in the judgment value table 56 and a configuration that has a judgment counter 57, but it can also be configured to have only one of them.

[0098] As described above, in the load drive device (load drive device 100A) of the second embodiment, multiple different determination values ​​(determination value 1, n, n+1) are set as determination values. The switch drive circuit (pre-driver circuit 20A) is configured to control the drive switch not to be turned on when the drive switch (valve opening driver 62, holding driver 61) is open and current is supplied to the load (injector 70) from the constant current source (internal constant current source 40), and the voltage across the load is within a predetermined range (e.g., below a specified determination value) divided by the multiple determination values.

[0099] According to the second embodiment of the load drive device configured as described above, similarly to the first embodiment, the short-circuit fault is diagnosed and the operation of the load drive device is prohibited before load drive control is performed when the load is short-circuited. Therefore, it is possible to prevent large currents flowing during normal load drive control. Furthermore, according to this embodiment, multiple determination values ​​that can be arbitrarily set according to an abnormal state are provided to determine whether the voltage across the load falls within a predetermined range (abnormal state) defined by the multiple determination values. Thus, for example, if the resistance value of the load decreases to the point where a large current flows through the load (injector circuit 90) without causing a circuit fault due to abnormal heating, it is possible to avoid an emergency stop of the load (such as an automobile engine).

[0100] Furthermore, in the load drive device (load drive device 100A) of the second embodiment, multiple different determination values ​​(determination value 1, n, n+1) are set as determination values. The switch drive circuit (pre-driver circuit 20A) is configured such that when the drive switch (valve opening driver 62, holding driver 61) is open and current is supplied from the constant current source (internal constant current source 40) to the load (injector 70), if the voltage across the load is within a predetermined range (e.g., below a specified determination value) divided by the multiple determination values, and the number of times the voltage across the load is within the predetermined range reaches a predetermined number, the drive switch is not turned on.

[0101] According to the second embodiment of the load drive device with the above-described configuration, similarly to the first embodiment, before performing load drive control in the event of a load short circuit, the short circuit fault is diagnosed and the operation of the load drive device is prohibited. Therefore, it is possible to prevent large currents flowing during normal load drive control. Furthermore, according to this embodiment, similarly to the above configuration, multiple determination values ​​are provided, and it is determined whether the voltage across the load falls within a predetermined range (abnormal state) defined by the multiple determination values. As a result, when the resistance value of the load decreases to a level that does not cause circuit failure due to abnormal heating, it is possible to avoid an emergency stop of the load (such as an automobile engine).

[0102] Furthermore, according to this embodiment, anomaly determination is performed by counting the number of times the voltage across the load falls within a predetermined range, preventing false detection of an abnormal state based on a small number of occurrences, such as one, caused by external noise. Therefore, it is possible to prevent emergency shutdown of the load (such as a car engine) caused by false detection of anomalies due to unexpected external noise.

[0103] Furthermore, the load drive device (load drive device 100A) in the second embodiment includes: a drive switch (valve opening driver 62, holding driver 61) that turns on or off the current supplied from a power source (e.g., a battery with a reference voltage VB) to the load (coil of the injector 70); a switch drive circuit (pre-driver circuit 20) that sends a drive signal to the drive switch based on a control command (signal 101) from an arithmetic unit (arithmetic unit 10); and a constant current source (internal constant current source 40) that supplies current to the load without passing through the drive switch, and is equipped with multiple different determination values ​​(determination value 1, n, n+1) as determination values. Furthermore, the switch drive circuit (pre-driver circuit 20A) is configured such that, when the drive switch (valve opening driver 62, holding driver 61) is open and current is supplied from the constant current source (internal constant current source 40) to the load (injector 70), it determines whether the voltage across the load is within a predetermined range (e.g., below a specified determination value) divided by multiple determination values, and notifies the arithmetic unit (arithmetic unit 10) of the determination result, which then performs control corresponding to the determination result.

[0104] Furthermore, in the above-described embodiment, the above-described arithmetic device (arithmetic device 10) performs control by outputting a control command to the switch drive circuit (pre-driver circuit 20A) to turn on the drive switch (valve opening driver 62, holding driver 61) or outputting a warning, based on the above-described determination result.

[0105] The load drive device of this embodiment, as described above, similarly to the first embodiment, diagnoses the short-circuit fault and prohibits the operation of the load drive device before performing load drive control when the load is short-circuited, thus preventing the large current flowing during normal load drive control.

[0106] Furthermore, according to this embodiment, similarly to the above configuration, it includes multiple determination values, and determines whether the voltage across the load is within a predetermined range (abnormal state) defined by the multiple determination values, and notifies the computing device of the determination result. Thus, depending on the severity of the determination result, it can either continue driving the load without determining it as a fault, or, as needed, convey the fault status to the driver via the display unit 151 (such as a warning light in the car), providing time to move the car to a safe location and prompting repair shops such as dealerships to perform repairs.

[0107] For example, it can be set to stop the load when the voltage across the load is below the judgment value 1, raise awareness (continue load operation) when the voltage is between the judgment value 1 and the judgment value n, issue a warning (continue load operation) when the voltage is between the judgment value n and the judgment value n+1, and determine that it is normal when the voltage is greater than the judgment value n+1. The arithmetic unit 10 performs load drive control or attention / warning output based on these judgment value settings.

[0108] Furthermore, in the first embodiment, the load drive device 100 ( Figure 1 The system includes a pre-driver diagnostic information transmission line 6, and the pre-driver circuit 20 (switch drive circuit) can also be configured to notify the arithmetic unit 10 when the voltage across the injector 70 falls below a predetermined value. That is, in... Figure 1 In this circuit, the monitoring results (load short-circuit abnormality) of the voltage monitoring circuit 50 are sent from the pre-driver circuit 20 to the arithmetic unit 10 via the pre-driver diagnostic information transmission line 6, and then output to the display unit 151. Thus, for example, a car driver can determine that the engine stopped because of a load short-circuit abnormality.

[0109] <Third Implementation Method>

[0110] The third embodiment is a configuration in which a drive switch is provided on the downstream side of the injector 70, relative to the load drive device 100 of the first embodiment.

[0111] Figure 7 This is a circuit diagram illustrating a configuration example of the load drive device 100B according to the third embodiment. In the injector circuit 90 of the first embodiment... Figure 1 In the first embodiment, since there is no path to cut off the current downstream of the injector 70, a constant current can be supplied to the injector 70 by turning on the internal constant current source 40. However, in the injector circuit 90B of the third embodiment, a drive switch (power-on / power-off switching driver 64) is provided, which is arranged downstream of the load in the direction of current flow from the power source (e.g., a battery with reference voltage VB) to the load (injector 70). Figure 7 In this device, a driver 64 for switching between energizing and de-energizing the injector 70 is connected between the coil of the injector 70 and the injector current monitoring resistor 80 on its downstream side. This allows switching the energization / de-energization of the load on its downstream side.

[0112] Since fault diagnosis is performed when the control of the valve opening actuator 62, the holding actuator 61, and the energizing / de-energizing switching actuator 64 are all off, the constant current supplied from the internal constant current source 40 is cut off by the energizing / de-energizing switching actuator 64. Therefore, in the load drive device 100B of this embodiment, compared with the first embodiment, an internal switch 45 and an internal switch control line 46 are added downstream of the injector 70, and the internal switch 45 is turned on via the internal switch control line 46 while the internal constant current source 40 is turned on. The energizing / de-energizing switching actuator 64 and the internal switch 45 use switching elements such as MOSFETs.

[0113] Therefore, the pre-driver circuit 20B has a diagnostic switch (internal switch 45) located downstream of the load (ejector 70). This diagnostic switch is turned on to supply current to the load from the constant current source (internal constant current source 40) when the downstream drive switch (energizing / de-energizing switch driver 64) is off. Thus, even if the downstream drive switch (energizing / de-energizing switch driver 64) is off, current from the constant current source can still flow through the load.

[0114] Figure 8 This is a timing diagram showing the operation and signals of each part of the load drive device in the third embodiment. Figure 8 In China, Figure 2 The timing diagram adds the drive signal (signal 111) for the power-on / power-off switching driver 64 and the command signal (signal 112) for the internal switch 45, while omitting the load stop command (signal 107).

[0115] like Figure 8 As shown, during the period when the control command output from the arithmetic unit 10 is in the "on control" state, the drive signal supplied from the controller 30 to the power-on / non-power-off switching driver 64 is also in the "on control" state (signal 111). The internal switch 45 is turned on by the controller 30 via the internal switch control line 46 while the internal constant current source 40 is on (signal 112). Other related... Figure 2 The timing diagrams are the same.

[0116] As described above, in the load drive device (load drive device 200B) of the third embodiment, in the direction of current flow from the power source to the load (ejector 70), there are an upstream drive switch (valve opening driver 62, holding driver 61) and a downstream drive switch (energizing / non-energizing switching driver 64) as drive switches. The upstream drive switch is disposed on the upstream side of the load, and the downstream drive switch is disposed on the downstream side of the load. The load drive device also includes a diagnostic switch (internal switch 45), which supplies current to the load from a constant current source (internal constant current source 40) by turning on when the upstream drive switch and the downstream drive switch are off.

[0117] Furthermore, in this embodiment, when the upstream drive switch (valve opening driver 62, holding driver 61) and the downstream drive switch (energizing / non-energizing switching driver 64) are off, and the diagnostic switch (internal switch 45) is turned on to supply current from the constant current source (internal constant current source 40) to the load (ejector 70), if the voltage across the load is below the determination value, the switch drive circuit (pre-driver circuit 20B) controls the upstream drive switch or the downstream drive switch to be off, or both the upstream drive switch and the downstream drive switch to be off.

[0118] Even with a downstream drive switch located downstream of the load, the load drive device of this embodiment, configured as described above, can supply current to the load from a constant current source without passing through an upstream drive switch and a downstream drive switch by including a diagnostic switch. Therefore, in this embodiment, the same operational effects as in the first and second embodiments can be obtained. That is, before performing load drive control in the event of a load short circuit, the short circuit fault is diagnosed, and the operation of the load drive device is prohibited, thus preventing large currents flowing during normal load drive control.

[0119] In addition, Figure 7 In this configuration, an internal constant current source 40 is configured on the upstream side of the injector 70, and an internal switch 45 is configured on the downstream side of the injector 70. Alternatively, an internal switch 45 can be configured on the upstream side of the injector 70, and an internal constant current source 40 can be configured on the downstream side of the injector 70.

[0120] Alternatively, instead of configuring the internal switch 45 on the downstream side of the injector 70, it is also possible to control the switching of the energized / de-energized actuator 64 to energize the injector 70 by means of the disconnection control of the actuator 62 for the opening valve and the holding actuator 61, so that the current of the internal constant current source 40 energizes the injector 70.

[0121] <Fourth Implementation Method>

[0122] The fourth embodiment is to provide a plurality of injectors in the load drive device 100B of the third embodiment to replace the injector 70 as the load.

[0123] Figure 9 This is a circuit diagram showing a configuration example of the load drive device 100C according to the fourth embodiment.

[0124] In the injector circuit 90C of the load drive device 100C, Figure 7 The injector 70 is replaced with injectors 70a and 70b. Therefore, the injector circuit 90C is configured such that energized / de-energized switching drivers 64a and 64b and injector current monitoring resistors 80a and 80b are provided for injectors 70a and 70b, respectively. Furthermore, in the pre-driver circuit 20C, internal switches 45a and 45b and internal switch control lines 46a and 46b are provided corresponding to the configuration of the injector circuit 90C.

[0125] In this embodiment, the loads connected downstream of the valve opening actuator 62 and the holding actuator 61 are the two injectors 70a and 70b, but it is also possible to consider a configuration that connects more than two (n+1) loads. In this case, the internal switch 45, the internal switch control line 46, the injector current monitoring resistor 80, and the energized / de-energized switching actuator 64 are also configured as (n+1) units.

[0126] Furthermore, in this embodiment, the internal switch control line 46 is configured individually each time the internal switch 45 is added, such as 1, 2, ..., n+1, but it is not limited to this example. For example, it is also possible to consider using one internal switch control line to control multiple internal switches 45 simultaneously.

[0127] As described above, in the load drive device (load drive device 200C) of the fourth embodiment, in the direction of current flow from the power source to the load, the load consists of a first load (injector 70a) downstream of the drive switch (valve opening driver 62, holding driver 61) and a second load (injector 70b) arranged in parallel with the first load. The load drive device includes a first downstream drive switch (power-on / power-off switching driver 64a) arranged downstream of the first load and a second downstream drive switch (power-on / power-off switching driver 64b) arranged downstream of the second load.

[0128] Furthermore, in this embodiment, when the drive switch (pre-driver circuit 20C) is in a state where the drive switch (valve opening driver 62, holding driver 61), the first downstream drive switch (energizing / non-energizing switching driver 64a), and the second downstream drive switch (energizing / non-energizing switching driver 64b) are disconnected, and current is supplied from the constant current source (internal constant current source 40) to the first load (injector 70a) or the second load (injector 70b), if the voltage across the first load or the second load is below a determination value, the switch control circuit (pre-driver circuit 20C) will prevent the first downstream drive switch or the second downstream drive switch from being turned on.

[0129] Even if the load drive device of this embodiment is configured with multiple downstream drive switches arranged downstream of each load corresponding to multiple (e.g., two) loads, current can be supplied to the load from a constant current source without going through each drive switch by controlling the opening or closing of the upstream drive switch (valve opening driver 62, holding driver 61) and the multiple downstream drive switches. Therefore, in this embodiment, the same operating effect as in the first to third embodiments can be obtained. That is, before load drive control is performed when one of the multiple loads is short-circuited, the short-circuit fault is diagnosed and the operation of the load drive device is prohibited, thus preventing large currents from flowing when energized under normal load drive control.

[0130] Furthermore, in this embodiment, a first downstream diagnostic switch (internal switch 45a) and a second downstream diagnostic switch (internal switch 45b) are provided. The first downstream diagnostic switch (internal switch 45a) is disposed downstream of the first load (injector 70a) in the direction of current flow from the power source to the load. When the first downstream drive switch (power-on / power-off switching driver 64a) is off, it supplies current to the first load from the constant current source (internal constant current source 40) by turning it on. The second downstream diagnostic switch (internal switch 45b) is disposed downstream of the second load (injector 70b). When the second downstream drive switch (power-on / power-off switching driver 64b) is off, it supplies current to the second load from the constant current source (internal constant current source 40) by turning it on.

[0131] Even if the load drive device of this embodiment has a configuration with multiple downstream drive switches arranged downstream of each load corresponding to multiple (e.g., two) loads, by including a first diagnostic switch and a second diagnostic switch, it is possible to supply current to the load from a constant current source without going through the upstream drive switches (valve opening driver 62, holding driver 61) and multiple downstream drive switches. Therefore, in this embodiment, the same operating effect as in the first to third embodiments can be obtained. That is, before performing load drive control when one of the multiple loads is short-circuited, the short-circuit fault is diagnosed and the operation of the load drive device is prohibited, thus preventing large currents flowing during normal load drive control.

[0132] exist Figure 9 In the load drive device 100C of this embodiment shown, there is only one set of drivers on the upstream side of the load, namely, a valve opening driver 62 and a holding driver 61, and it also includes an injector circuit 90C consisting of multiple loads (injectors 70a, 70b). Furthermore, the load drive device 100C includes, for each of the multiple injectors 70a, 70b, a power-on / power-off switching driver 64a, 64b, an injector current monitoring resistor 80a, 80b, and an internal switch 45a, 45b. Therefore, by applying a constant current from the internal constant current source 40 to each injector 70a, 70b, fault diagnosis can be performed on each injector 70a, 70b.

[0133] <Other>

[0134] Furthermore, the present invention is not limited to the above-described embodiments. Various other applications and modifications may be adopted without departing from the spirit of the invention as described in the claims.

[0135] For example, the above embodiments have described the configuration of the load drive device in detail and specifically to aid in understanding the present invention, and are not necessarily limited to having all the described constituent elements. Furthermore, a portion of the configuration of one embodiment may be replaced with constituent elements of other embodiments. Additionally, constituent elements of other embodiments may be added to the configuration of one embodiment. Furthermore, for a portion of the configuration of each embodiment, other constituent elements may be added, replaced, or deleted.

[0136] Furthermore, the aforementioned components, functions, and processing units can also be implemented in hardware, for example, by designing some or all of them using integrated circuits. As hardware, FPGAs (Field Programmable Gate Arrays) or ASICs (Application Specific Integrated Circuits) can also be used. Alternatively, the aforementioned components and functions can be implemented in software by having a processor (e.g., the CPU used in the arithmetic unit 10) interpret and execute the programs that implement their respective functions. The programs, tables, files, and other information implementing each function can be stored in semiconductor memory (e.g., memory 11), or in recording devices such as hard disks, SSDs (Solid State Drives), or recording media such as IC cards, SD cards, or optical discs.

[0137] Furthermore, in the above embodiments, the representation of control lines and information lines is considered necessary for the description, and not all control lines and information lines may necessarily be represented on the product. In reality, almost all constituent elements can be considered to be interconnected.

[0138] Symbol Explanation

[0139] 1…Electronic Control Unit (ECU), 5…Pre-driver control command line, 6…Pre-driver diagnostic information transmission line, 10…Arithmetic unit, 11…Memory, 20, 20A…Pre-driver circuit, 21…Load stop command line, 22…Comparison result transmission line, 30…Controller, 40…Internal constant current source, 41…Internal constant current source control line, 45…Internal switch, 46…Internal switch control line, 50, 50A…Voltage monitoring circuit, 51…Differential voltage meter, 52…Voltage amplifier circuit, 55, 5… 5A… Voltage comparison result calculation circuit, 56… Judgment value table, 57… Judgment counter, 61… Holding driver, 62… Valve opening driver, 63… Boost circuit, 64… Power-on / non-power-off switching driver, 70, 70a, 70b… Injector, 80, 80a, 80b… Injector current monitoring resistor, 90, 90B, 90C… Injector circuit, 100, 100A~100C… Load drive device, 150… Operation display device, 151… Display unit, 152… Operation unit.

Claims

1. A load driving device, characterized in that, have: A drive switch that connects or disconnects the current supplied from the power source to the load; A switch driving circuit that sends a driving signal to the drive switch based on a control command from a computing device; as well as A constant current source that supplies current to the load without passing through the drive switch. When the drive switch is off and current is supplied from the constant current source to the load, and the voltage across the load is below a predetermined value, the switch drive circuit controls the drive switch to prevent it from being turned on.

2. The load driving device according to claim 1, characterized in that, The drive switch consists of a first drive switch and a second drive switch. The first drive switch turns on or off the current supplied from the power source to the load, and the second drive switch turns on or off the current supplied from the boost circuit that boosts the voltage of the power source to the load. When the first drive switch and the second drive switch are off and current is supplied from the constant current source to the load, if the voltage across the load is below the determination value, the switch drive circuit controls the first drive switch and the second drive switch to prevent them from being turned on.

3. The load driving device according to claim 1, characterized in that, The switch driving circuit generates instructions for controlling the energization and de-energization of the constant current source based on the driving signal for the driving switch.

4. The load driving device according to claim 1, characterized in that, The constant current source supplies a smaller current to the load when the load is not driven than the current flowing through the load when the load is driven.

5. The load driving device according to claim 1, characterized in that, The constant current source is configured upstream of the load.

6. The load driving device according to claim 1, characterized in that, The switch driving circuit includes: a controller that generates a driving signal for driving the switch based on the control command; a constant current source; and a voltage monitoring circuit that monitors the voltage across the load and determines whether the voltage across the load is below a predetermined value. When the drive switch is off and current is supplied to the load from the constant current source, if the voltage monitoring circuit determines that the voltage across the load is below the determined value, the controller controls the load by not sending the drive signal indicating the load is on and stopping the load.

7. The load driving device according to claim 1, characterized in that, The drive switch is positioned upstream of the load in the direction of current flow from the power source to the load.

8. The load driving device according to claim 1, characterized in that, The drive switch is configured downstream of the load in the direction of current flow from the power source to the load.

9. The load drive device according to claim 8, characterized in that, It also includes a diagnostic switch disposed downstream of the load, which supplies current from the constant current source to the load by turning on the diagnostic switch when the drive switch on the downstream side is off.

10. The load driving device according to claim 1, characterized in that, Multiple different judgment values ​​are set as the judgment values. When the drive switch is off and current is supplied from the constant current source to the load, and the voltage across the load falls within a predetermined range defined by the plurality of determination values, the switch drive circuit controls the drive switch to de-energize it.

11. The load driving device according to claim 1, characterized in that, Multiple different judgment values ​​are set as the judgment values. When the drive switch is off and current is supplied from the constant current source to the load, and the voltage across the load falls within a predetermined range defined by the plurality of determination values, and the number of times the voltage across the load falls within the predetermined range reaches a predetermined number, the switch drive circuit controls the drive switch to de-energize the drive switch.

12. The load driving device according to claim 1, characterized in that, The switch drive circuit notifies the computing device when the voltage across the load is below the determination value.

13. The load driving device according to claim 1, characterized in that, In the direction of current flow from the power source to the load, there are upstream drive switches and downstream drive switches as drive switches, the upstream drive switch being disposed upstream of the load and the downstream drive switch being disposed downstream of the load. The load drive device also includes a diagnostic switch, which supplies current from the constant current source to the load by turning on the diagnostic switch when the upstream drive switch and the downstream drive switch are off.

14. The load driving device according to claim 13, characterized in that, When the upstream drive switch and the downstream drive switch are off, and the diagnostic switch is turned on to supply current from the constant current source to the load, if the voltage across the load is below the determination value, the switch drive circuit controls the switch to either turn off the upstream drive switch or the downstream drive switch, or to turn off both the upstream drive switch and the downstream drive switch.

15. The load drive device according to claim 1, characterized in that, In the direction of current flow from the power source to the load, the load consists of a first load downstream of the drive switch and a second load connected in parallel with the first load. The load driving device includes: a first downstream drive switch disposed on the downstream side of the first load and a second downstream drive switch disposed on the downstream side of the second load.

16. The load drive device according to claim 15, characterized in that, When the drive switch, the first downstream drive switch, and the second downstream drive switch are disconnected, and current is supplied from the constant current source to the first load or the second load, if the voltage across the first load or the second load is below the determination value, the switch drive circuit controls the first downstream drive switch or the second downstream drive switch to prevent the first downstream drive switch or the second downstream drive switch from being turned on.

17. The load drive device according to claim 15, characterized in that, It includes: a first downstream diagnostic switch, which is disposed downstream of the first load in the direction of current flow from the power source to the load, and supplies current from the constant current source to the first load by turning on the first downstream diagnostic switch when the first downstream drive switch is off. as well as A second downstream diagnostic switch is configured downstream of the second load. When the second downstream drive switch is off, current is supplied from the constant current source to the second load by turning on the second downstream diagnostic switch.

18. The load driving device according to claim 1, characterized in that, The switch driving circuit can control the energization and de-energization of the constant current source at any time during the period when the drive switch is off.

19. A load driving device, characterized in that, have: A drive switch that connects or disconnects the current supplied from the power source to the load; A switch driving circuit that sends a driving signal to the drive switch based on a control command from a computing device; as well as A constant current source that supplies current to the load without passing through the drive switch. Multiple different judgment values ​​are set as judgment values. When the drive switch is off and current is supplied from the constant current source to the load, the switch drive circuit determines which range of the range defined by the plurality of determination values ​​the voltage across the load falls within, and notifies the computing device of the determination result. The computing device performs control corresponding to the determination result. When the drive switch is off and current is supplied from the constant current source to the load, and the voltage across the load falls within a predetermined range defined by the plurality of determination values, the switch drive circuit controls the drive switch to de-energize it.

20. The load drive device according to claim 19, characterized in that, Based on the determination result, the computing device controls the output of the control command to the switch driving circuit to turn on the drive switch, or controls the output of a warning.

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