JP6707873B2 - Vehicle load drive control device - Google Patents

Description

The present invention relates to a vehicle load drive control device.

This type of vehicle load drive control device is configured to be connected to a load by wire connection, for example, by a harness. In the harness, there is a possibility that the power supply side of the load and the power supply terminal may be short-circuited or the ground side node of the load and the ground node may be short-circuited due to human error such as maintenance of the vehicle. A technique for detecting such a short circuit is disclosed in Patent Document 1, for example. According to the technique described in Patent Document 1, the voltage value downstream of the electromagnetic load is input to the diagnostic unit, and the voltage value downstream of the electromagnetic load when both the switching element of the high-side driver and the switching element of the low-side driver are turned on. It is disclosed to detect whether or not a rare short-circuit failure has occurred in the switch element of the high side driver by detecting.

JP, 2010-62675, A (Drawing 7).

For example, when the technique described in Patent Document 1 is used, the following problems occur. For example, when the impedance of the harness for connecting the load and the downstream terminal is relatively large and the harness is mistakenly connected between the downstream terminal and the ground node, the switching element and the low side driver of the high side driver are connected. Even if both the switch elements of the driver are turned on, the current flowing through the current detection resistor does not change greatly according to the short-circuit current, and the abnormality detection is overlooked, resulting in poor reliability of abnormality detection.

An object of the disclosure of the present invention is to improve reliability of detection of a short circuit to a ground node of a downstream terminal in a configuration in which a harness is connected between a downstream terminal and a load and fail-safe processing can be performed when an abnormality is detected. Another object of the present invention is to provide a load drive control device for a vehicle.

The invention according to claim 1 is directed to a vehicle load drive control device for driving a vehicle load connected between an upstream terminal and a downstream terminal. This vehicle load drive control device includes a high side switch, a low side switch, a switch control unit, an abnormality confirmation control unit, and an abnormality detection unit. The high-side switch is connected between the power supply voltage supply node and the upstream terminal of the load, and the low-side switch is connected between the ground node and the downstream terminal of the load.

In addition, during normal operation, the switch control section normally keeps the low-side switch normally turned on, and also normally turns on/off the high-side switch in response to the duty control pulse signal being applied to the high-side switch to drive the inductive load. When confirming an abnormality, the abnormality confirmation control unit turns off the low side switch and turns on or off the high side switch while the high side switch is normally off. At this time, if the harness is normally connected, at least the downstream terminal of the inductive load and the ground node are opened. Normally, the downstream terminal and the ground node are opened unless the downstream terminal is short-circuited to the ground node. On the contrary, if the downstream terminal is short-circuited to the ground node by a harness, for example, the abnormality detection unit can detect the short-circuit of the downstream terminal to the ground node. This can improve the reliability of detecting a short circuit to the ground node.

According to the third aspect of the invention, normally, if the downstream terminal is not short-circuited to the ground node, the downstream terminal and the ground node are opened, so that the current flowing through the inductive load is supplied to the power supply through the freewheeling diode. Since it will flow to the voltage supply node, the voltage at the downstream terminal will be a larger value than the ground potential. Conversely, if the downstream terminal is short-circuited to the ground node by a harness, for example, the voltage of the downstream terminal becomes the ground potential or a value close to this voltage. Therefore, the abnormality detection unit can detect a short circuit to the ground node of the downstream terminal according to the voltage of the downstream terminal detected by the voltage detection unit or the voltage proportional to this voltage. This can improve the reliability of detecting a short circuit to the ground node.

Electrical configuration diagram schematically showing the electronic control unit of the first embodiment. Timing chart showing the operation Timing chart showing the fail-safe operation Explanatory diagram schematically showing the comparison target technology Electrical configuration diagram schematically showing the electronic control unit of the second embodiment. Timing chart showing the operation

Hereinafter, some embodiments of an electronic control device as a vehicle load drive control device will be described with reference to the drawings. In each of the embodiments described below, configurations that perform the same or similar operations are denoted by the same or similar reference numerals, and description thereof will be omitted as necessary.

(First embodiment)
FIG. 1 is a schematic block diagram showing an electrical configuration example of an electronic control unit. An electronic control unit (ECU) 1 is configured to drive a fuel pump 2, for example. For example, an internal combustion engine such as a diesel engine using a common rail system compresses fuel at high pressure and discharges the high pressure fuel compressed by the fuel pump 2 to the common rail. At this time, the electronic control unit 1 operates as a vehicle load drive control unit that drives and controls the fuel pump 2. The fuel pump 2 is driven by using an electromagnetic coil 2a, which is connected between the upstream terminal 1a and the downstream terminal 1b of the electronic control unit 1 and is configured as an inductive load. ..

The electronic control unit 1 includes an arithmetic unit 3 and a drive circuit 4 connected to the subsequent stage of the arithmetic unit 3. The arithmetic unit 3 is composed of, for example, a microcomputer, includes a CPU, an input/output unit, and a storage unit (not shown) such as RAM, ROM, or EEPROM, and is guided based on a program stored in the storage unit. Drive sexual load. The arithmetic unit 3 has functions as a switch control unit 5, a voltage detection unit 6, a current detection unit 7, an abnormality detection unit 8, and an abnormality confirmation control unit 9. The voltage detector 6 detects the edge detection voltage V1 and the voltage V2 at the downstream terminal.

The arithmetic unit 3 includes a sensor signal acquisition terminal 3a that acquires various sensor signals, a command signal output terminal 3b that outputs a command signal, an edge detection voltage acquisition terminal 3c that acquires an edge detection voltage, and an abnormality confirmation that outputs an abnormality confirmation control signal. Control terminal 3d, downstream terminal voltage acquisition terminal 3e that acquires the voltage of the downstream terminal 1b, fail-safe control signal output terminal 3f that outputs a control signal during fail-safe, and detection that acquires a current signal flowing through the electromagnetic coil 2a A current acquisition terminal 3g is provided.

The drive circuit 4 that drives the electromagnetic coil 2a includes a comparator CP1, an operational amplifier OP1, resistors R1 to R14, capacitors C1 and C2, free wheeling diodes D1 and D2, and transistors Tr1 to Tr4, SH and SL. As shown in FIG. 1, the drive circuit 4 includes transistors SH and SL on the high side and the low side at the final stage. However, for convenience of description, these transistors SH and SL are distinguished from the other transistors Tr1 to Tr4. , And high side switch SH and low side switch SL, respectively.

The arithmetic unit 3 outputs a pulse signal by duty control as a command signal from the command signal output terminal 3b according to the sensor signal acquired from the sensor signal acquisition terminal 3a, for example. The non-inverting input terminal of the comparator CP1 is connected to the command signal output terminal 3b via the resistor R1 and the capacitor C1. The resistor R1 and the capacitor C1 delay the output voltage of the command signal output terminal 3b and input it to the comparator CP1. The comparator CP1 sets the output to the “H” or “L” logic level based on the level of the input voltage of the comparator CP1 and applies the logic level to the control terminal of the transistor Tr1 through the resistors R2 and R3.

The type of the transistor Tr1 is not particularly limited, but the transistor Tr1 is composed of, for example, an N-channel type MOS transistor. The transistor Tr1 turns on/off between the drain and the source by inputting the output logic level of the comparator CP1 to the gate which is the control terminal. The resistor R2 is connected in series between the output terminal of the comparator CP1 and the control terminal of the transistor Tr1, and the resistor R3 is connected between the control terminal of the transistor Tr1 and the supply node NVC of the logic power supply Vcc. It is configured as a pull-up resistor that pulls up to the logic power supply Vcc. The edge detection voltage acquisition terminal 3c of the arithmetic unit 3 is connected to the control terminal of the transistor Tr1, and thus the edge detection voltage V1 can be acquired. The edge detection voltage acquisition terminal 3c of the arithmetic unit 3 is provided to acquire the voltage of the common connection node between the resistors R2 and R3 and the control terminal of the transistor Tr1.

The resistor R4 is connected in series between the power supply voltage supply node NB of the battery voltage VB and the drain of the transistor Tr1, and the resistor R5 is connected between this common connection point and the control terminal of the high side switch SH. ing. The high-side switch SH is composed of, for example, a P-channel type MOS transistor, and is composed of a source and a drain connected between the power supply voltage supply node NB and the upstream terminal 1a. The battery voltage VB is supplied to the power supply voltage supply node NB. The diode D2 is reversely connected between the upstream terminal 1a and the ground node NS to which the ground potential is applied. This diode D2 is configured as a freewheeling diode.

On the other hand, the fail-safe control signal output terminal 3f of the arithmetic unit 3 is connected to the control terminal of the transistor Tr2 through the resistor R6. The fail-safe control signal output terminal 3f is a terminal used for fail-safe processing by forcibly turning off the power when a drive abnormality of the electromagnetic coil 2a is detected. Sets the output of the fail-safe control signal output terminal 3f to the non-active level "L", and sets the output of the fail-safe control signal output terminal 3f to the active level "H" when the operation is forcibly stopped. The transistor Tr2 is composed of, for example, an NPN type transistor, the emitter serving as a conducting terminal is connected to the ground node NS, and the collector serving as a conducting terminal is connected to the supply node NVC of the logic power supply Vcc via the pull-up resistor R7. ..

The collector of the transistor Tr2 is connected to the control terminal of the low side switch SL via the resistor R8. The low-side switch SL is formed of, for example, an N-channel type MOS transistor, and is formed by connecting the drain and source between the downstream terminal 1b and the ground node NS. A diode D1 is reversely connected between the power supply voltage supply node NB and the downstream terminal 1b. This diode D1 is configured as a freewheeling diode. The downstream terminal voltage acquisition terminal 3e of the arithmetic device 3 is connected to the downstream terminal 1b. The downstream terminal voltage acquisition terminal 3e of the arithmetic unit 3 is provided to obtain information on the voltage of the downstream terminal 1b.

A current detection resistor R9 is connected in series between the downstream terminal 1b and the ground node NS together with a drain source serving as two energizing terminals of the low side switch SL. Both terminals of the current detection resistor R9 are input to the non-inverting input terminal of the operational amplifier OP1 via the resistors R10 and R11 for voltage division. The operational amplifier OP1 has a resistor R13 connected between the output terminal and the inverting input terminal, and further has a resistor R12 connected between the inverting input terminal and the ground node NS. As a result, the operational amplifier OP1 and the resistors R12 and R13 form the positive phase amplifier circuit 10. The output terminal of the operational amplifier OP1 is connected to the detected current acquisition terminal 3g of the arithmetic unit 3 through the resistor R14. The detected current acquisition terminal 3g is provided in particular to obtain information on the current flowing through the current detection resistor R9, and the current detection unit 7 acquires information about the current flowing through the current detection resistor R9 from the detected current acquisition terminal 3g.

A capacitor C2 is connected between the detected current acquisition terminal 3g and the ground node NS, and the resistor R14 and the capacitor C2 form a low-pass filter 11. Further, the output of the operational amplifier OP1 is input to the inverting input terminal of the comparator CP1 through the resistor R15, and the feedback control circuit 12 is configured by this.

The abnormality confirmation control terminal 3d of the arithmetic unit 3 is connected to the control terminals of the transistors Tr3 and Tr4. The abnormality confirmation control terminal 3d is provided to output a signal for periodically turning off the high side switch SH and the low side switch SL for confirming the abnormality. The transistor Tr3 is composed of, for example, a PNP type transistor. A logic power supply Vcc is applied to the emitter of the transistor Tr3, and the collector is connected to the common connection node of the resistor R6 and the control terminal of the transistor Tr2. Further, the abnormality confirmation control terminal 3d of the arithmetic unit 3 is connected to the control terminal of the transistor Tr4. The transistor Tr4 is composed of, for example, a PNP type transistor, the logic power supply Vcc is applied to the emitter, and the collector is connected to the resistors R2 and R3 and the common connection node of the control terminals of the transistor Tr1. These configurations are provided to deal with a short circuit abnormality of the downstream terminal 1b to the ground node NS.

Although the detailed configuration is not described, the arithmetic unit 3 of the electronic control unit 1 turns off the low-side switch SL when it detects that the upstream terminal 1a is short-circuited to the battery voltage VB by using a configuration (not shown). By doing so, the fail-safe processing is performed by stopping the power supply operation of the battery voltage VB.

Further, as will be described later, the arithmetic device 3 turns off the high-side switch SH when it detects that the downstream terminal 1b is short-circuited to the ground node NS, thereby stopping the power supply operation of the battery voltage VB. It is configured for failsafe processing.

The operation of the above configuration will be described. FIG. 2 schematically shows a timing chart showing signals such as voltage and current of each node according to the command signal of the arithmetic unit 3. First, in normal times, the arithmetic unit 3 turns off the transistor Tr2 by outputting the fail-safe control signal as a non-active level "L" by the function of the switch control unit 5. As a result, the logic power supply Vcc is applied to the control terminal of the low side switch SL through the pull-up resistor R7, and the low side switch SL is normally turned on. In a state where the low-side switch SL is normally turned on, the arithmetic unit 3 outputs a pulse signal as a command signal to the control terminal of the high-side switch SH by the function of the switch control unit 5, thereby turning on/off the high-side switch SH. By switching, the energization of the electromagnetic coil 2a is controlled.

As shown in FIG. 2, when the logic levels “H” and “L” of the command signal change, the output logic level of the comparator CP1 changes with a delay depending on the influence of the time constant of the delay circuit formed by the resistor R1 and the capacitor C1. To do. For example, when the output level of the comparator CP1 becomes "H", the transistor Tr1 is turned on, so that the control terminal of the high side switch SH becomes "L", which turns on the high side switch SH. Since the low side switch SL is normally turned on as described above, when the high side switch SH is turned on, a current flows along the path of the high side switch SH, the electromagnetic coil 2a, the low side switch SL, and the current detection resistor R9. As a result, the load current flowing through the electromagnetic coil 2a monotonically increases as shown in periods T1 and T3 of FIG.

On the contrary, when the output logic level of the comparator CP1 becomes “L”, the transistor Tr1 is turned off, so that the control terminal of the high side switch SH becomes “H”, and the high side switch SH is turned off. Since the low-side switch SL is normally turned on, if the high-side switch SH is turned off, the current flowing through the electromagnetic coil 2a will flow through the freewheeling diode D2, and the current will flow in the forward direction of the diode D2 and the electromagnetic coil. 2a, the low-side switch SL, and the current detection resistor R9. As a result, the current is no longer supplied from the power supply voltage supply node NB, and the current flowing through the electromagnetic coil 2a monotonically decreases as shown in periods T2 and T4 in FIG. Thereby, the arithmetic unit 3 can control the load current of the electromagnetic coil 2a to rise/fall by pulse-controlling the command signal.

When the duty ratio of the pulse signal of the command signal is large, the load current increases, and when the duty ratio is small, the load current decreases. At this time, if the load current increases, the detection voltage of the current detection resistor R9 increases, and if the load current decreases, the detection voltage of the current detection resistor R9 also decreases. The operational amplifier OP1 positively amplifies the voltage detected by the current detection resistor R9 together with the resistors R10 to R13. Since the output of the operational amplifier OP1 is input to the inverting input terminal of the comparator CP1 through the resistor R15, the output of the operational amplifier OP1 increases when the load current increases, and when the comparator CP1 operates with the output of the operational amplifier OP1 as a reference, As a result, the duty ratio of the command signal can be suppressed low, and negative feedback control can be performed. In the vehicle, the battery voltage VB fluctuates according to various factors, but the arithmetic unit 3 responds to this feedback control action so as to control the load current within a certain range around a certain constant current SH. Therefore, the load current can be controlled within a fixed range even if the battery voltage VB changes.

<Abnormality confirmation control process>
In such a normal flow, the arithmetic unit 3 outputs an abnormality confirmation control signal from the abnormality confirmation control terminal 3d. At this time, the arithmetic unit 3 outputs the abnormality confirmation control signal for turning on the high side switch SH for confirming the abnormality and for turning off the low side switch SL.

Further, in this case, the arithmetic unit 3 sets the active level “L” of the abnormality confirmation control signal so that the load current is in the middle of decreasing, that is, the output of the comparator CP1 becomes “L” level and the high side switch. It is desirable to turn off the low-side switch SL by setting the abnormality confirmation control signal to the active level "L" during the period when SH is normally off. Further, for example, when the “L” level of the abnormality confirmation control signal is set to the active level, the arithmetic unit 3 preferably makes the active level period shorter than the period in which the high side switch SH is normally turned off.

In the present embodiment, the arithmetic unit 3 acquires the edge detection voltage of the edge detection voltage acquisition terminal 3c by the voltage detection unit 6 and slightly delays from the timing when the edge detection voltage shifts from “H” to “L”. When the edge detection voltage is surely at "L", the function of the abnormality confirmation control section 9 outputs the active level "L" of the abnormality confirmation control signal, and then outputs the abnormality confirmation control signal to the non-active level "H". ".

When the arithmetic unit 3 outputs the abnormality confirmation control signal as the active level "L", both the transistors Tr3 and Tr4 are turned on. When the transistor Tr4 is turned on, a voltage close to the logic power supply Vcc is input to the control terminal of the transistor Tr1. As a result, the transistor Tr1 is turned on, and the control terminal of the high side switch SH becomes "L" accordingly. SH turns on. Simultaneously with this operation, when the transistor Tr3 is turned on, a voltage close to the logic power supply Vcc is input to the control terminal of the transistor Tr2, whereby the transistor Tr2 is turned on, and the low side switch SL is turned off accordingly. That is, when the arithmetic unit 3 outputs the abnormality confirmation control signal as the active level "L", the high side switch SH is turned on and the low side switch SL is turned off as shown in a period T2a of FIG.

Normally, during the periods T2 and T4 during which the load current is decreasing, as described above, the current flows through the upstream reflux diode D2, the electromagnetic coil 2a, the low-side switch SL, and the current detection resistor R9. .. Here, when the high-side switch SH is turned on and the low-side switch SL is turned off by the arithmetic unit 3 outputting the abnormality confirmation control signal as the active level “L”, this current path is cut off. That is, the battery voltage VB comes to be applied to the downstream terminal 1b through the high side switch SH and the electromagnetic coil 2a. Considering the influence of the current flowing through the electromagnetic coil 2a immediately before this, the current is regenerated from the electromagnetic coil 2a to the node NB side of the battery voltage VB through the diode D1 for circulation on the downstream side.

Therefore, if, for example, a harness short circuit abnormality has not occurred, the voltage V2 of the downstream terminal 1b becomes pulsed in synchronization with the timing when the abnormality confirmation control signal becomes the active level "L", as shown in the period T2a of FIG. To rise. The arithmetic unit 3 acquires the voltage V2 of the downstream terminal voltage acquisition terminal 3e in synchronization with the abnormality confirmation control signal, determines whether this voltage V2 has reached a predetermined threshold voltage Vt, and determines the threshold voltage Vt. If it has reached, it is determined to be normal.

Here, a case where the downstream terminal 1b is short-circuited to the ground node NS will be described. Although the downstream terminal 1b is connected to the electromagnetic coil 2a using the harness H1, it is assumed that the downstream terminal 1b is erroneously connected to the ground node NS. For example, when the impedance of the harness H1 is relatively low, for example, about 20 mΩ, and the resistance value of the current detection resistor R9 is, for example, about several Ω, a short-circuit current flows to the ground node NS through the harness H1. At this time, for example, as shown in FIG. 3, even if the arithmetic unit 3 continues to output the pulsed command signal, the short-circuit current flows from the short-circuit timing of the ground node NS to the ground node NS side through the harness H1. to continue. Therefore, the detection current of the current detection resistor R9 decreases and becomes almost zero.

Even if the arithmetic unit 3 continues to output the pulsed command signal, the output of the operational amplifier OP1 does not rise unless the detection current of the current detection resistor R9 rises. Therefore, a relatively low voltage is input to the inverting input terminal of the comparator CP1, and the comparator CP1 holds its output as "H". At this time, since the edge detection voltage V1 acquired from the edge detection voltage acquisition terminal 3c is not synchronized with the command signal at this time, the arithmetic unit 3 can determine an abnormal state during the period T10 in FIG. 3 by the function of the abnormality detection unit 8. In this abnormal state, the arithmetic unit 3 outputs the fail-safe control signal to the active level "H" from the fail-safe control signal output terminal 3f, thereby turning on the transistor Tr2 and turning on the low-side switch SL at the timing ta in FIG. Turn off forcibly. The arithmetic unit 3 also turns off the high-side switch SH by stopping the output of the pulsed command signal and setting it to "L". That is, in such a case, fail-safe processing can be realized without acquiring the voltage of the downstream terminal 1b.

Considering the case where the downstream terminal 1b is ground short-circuited to have a relatively high impedance, for example, when the electromagnetic coil 2a used in the pump and the electronic control unit 1 are separated by a considerable distance, these are connected. The impedance of the harness H2 is relatively high and is, for example, about 200 mΩ. In such a case, for example, when the resistance value of the current detection resistor R9 becomes similar to this value (for example, a fraction to several times), as shown in the waveform example of FIG. At T11, the current detected by the current detection resistor R9 does not change significantly. At this time, it has been found that even if the arithmetic unit 3 acquires a signal from the detected current acquisition terminal 3g and uses it for the ground short-circuit detection process, the abnormality detection may be overlooked.

For example, even if the downstream terminal 1b is short-circuited to the ground by the harness H2, if the electromagnetic coil 2a is continuously driven without being able to detect an abnormality, the load current corresponding to the duty of the pulse signal of the command signal decreases, so this load Feedback control works to increase the current. At this time, although the load current becomes large, there arises a problem that the increase in the load current cannot be detected. When the electromagnetic coil 2a is applied to a pump that sends fuel to the common rail, the load current increases and the pump that sends the fuel closes, so that the fuel pressure in the common rail decreases, and the engine stops without the cause of abnormality being identified. It will be decided.

In this case, the arithmetic unit 3 cannot output the fail-safe control signal as the active level "H", and fail-safe processing cannot be normally realized. Therefore, in the present embodiment, in order to improve the reliability of abnormality detection even if the impedance of the harness H2 is affected, the downstream terminal voltage acquisition terminal 3e is provided, and the ground short circuit detection is performed according to the voltage of the downstream terminal 1b. I am trying to do it.

<Operation of this embodiment>
As shown in FIG. 2, the arithmetic unit 3 acquires the voltage V2 of the downstream terminal 1b from the downstream terminal voltage acquisition terminal 3e. Therefore, the arithmetic unit 3 periodically sets the abnormality confirmation control signal to the active level "L" to turn on the high-side switch SH and turn off the low-side switch SL, and in synchronization with this timing, the downstream terminal voltage acquisition terminal 3e to the downstream side. The voltage of the terminal 1b is acquired. At this time, if the voltage V2 of the downstream terminal 1b does not reach the threshold voltage Vt, it is determined that an abnormal state is present as indicated by timings tb and tc in FIG.

When the harness H2 having a relatively high impedance is connected between the downstream terminal and the ground, the current is short-circuited to the ground node NS through the harness while the low side switch SL is turned off. At this time, if the impedance of the harness H2 is, for example, about 200 mΩ, the voltage of the downstream terminal 1b does not increase, and the arithmetic unit 3 can determine that the abnormality detection unit 8 is in an abnormal state. This makes it possible to reliably detect that the harness H2 is short-circuited to the ground node NS. Even when the low-impedance harness H1 is connected between the downstream terminal 1b and the ground node NS, the voltage of the downstream terminal 1b does not rise similarly. Therefore, it is possible to make a determination according to the voltage V2 of the downstream terminal 1b without using the signal of the detected current acquisition terminal 3g.

The contents of this embodiment are functionally summarized as follows. The arithmetic unit 3 turns off the low side switch SL for abnormality confirmation by the function of the abnormality confirmation control unit 9 while the high side switch SH is normally turned off by the function of the switch control unit 5. Therefore, if the harnesses H1 and H2 are normally connected, at least the downstream terminal 1b of the electromagnetic coil 2a and the ground node NS are opened. At this time, the arithmetic unit 3 detects the voltage of the downstream terminal 1b by the voltage detection unit 6, and detects the short circuit of the downstream terminal 1b to the ground node NS by the function of the abnormality detection unit 8 according to the voltage of the downstream terminal 1b. To do.

Normally, if the downstream terminal 1b is not short-circuited to the ground node NS, the downstream terminal 1b and the ground node NS are opened, so that the current flows from the downstream terminal 1b to the node NB side of the battery voltage VB through the reflux diode D1. As a result, the voltage at the downstream terminal 1b rises and becomes higher than the voltage 0V at the ground node NS. On the contrary, if the downstream terminal 1b is ground-shorted by the harnesses H1 and H2, the voltage of the downstream terminal 1b becomes the voltage of the ground node NS or a value close to this voltage. Therefore, the arithmetic unit 3 can detect a short circuit of the downstream terminal 1b of the electromagnetic coil 2a to the ground node NS by the function of the abnormality detection unit 8. As a result, the reliability of detecting a short circuit to the ground node NS can be improved.

The arithmetic unit 3 turns on the high-side switch SH when turning off the low-side switch SL for confirming an abnormality. At this time, the potential of the upstream terminal 1a is approximately the battery voltage VB and the potential of the downstream terminal 1b is approximately. It becomes the battery voltage VB. Therefore, at this time, the applied voltage across the electromagnetic coil 2a is approximately the voltage (≈0V) applied to the electromagnetic coil 2a when the current circulates through the diode D1 when the high side switch SH is normally turned off. Can be controlled to the same voltage. Therefore, it is possible to confirm whether or not the short circuit abnormality to the ground node NS has occurred without changing the degree of change of the current flowing through the electromagnetic coil 2a as much as possible.

The arithmetic unit 3 commands the timing of the off control of the low side switch SL and the on control of the high side switch SH by the abnormality confirmation control unit 9, and during the period when the timing instruction is issued from the abnormality confirmation control unit 9, the abnormality detection unit 8 Detects a short circuit to the ground node NS according to an output change of the downstream terminal 1b according to switching of the low side switch SL on/off. Therefore, the arithmetic unit 3 can perform timing control according to the command from the abnormality confirmation control unit 9.

When the abnormality detection unit 8 detects a short circuit to the ground node at the downstream terminal 1b, the arithmetic unit 3 turns off the high side switch SH to perform fail-safe processing. Therefore, even if an abnormality occurs, this abnormality occurs. Can be dealt with immediately.

(Second embodiment)
5 and 6 show additional explanatory views of the second embodiment. FIG. 5 schematically shows an electrical configuration example of the electronic control device replacing FIG. 1, and FIG. 6 schematically shows a timing chart replacing FIG.

As shown in FIG. 5, the arithmetic device 203, which replaces the arithmetic device 3, is not provided with the abnormality confirmation control terminal 3d. Instead, the electronic control unit 201 includes the one-shot timer 13 as an abnormality confirmation control unit. The one-shot timer 13 inputs the output of the comparator CP1 and outputs a falling pulse when detecting the falling timing of this output. The output of the one-shot timer 13 is input to the control terminals of the transistors Tr3 and Tr4. Since other configurations are similar to those shown in FIG. 1, the description of the configuration is omitted.

The operation of this configuration will be described with reference to FIG. As shown in FIG. 6, the output of the comparator CP1 also changes with a delay in the change of the command signal, but the one-shot timer 13 outputs a pulse of active level “L” in synchronization with the falling output of the comparator CP1. ..

That is, the output of the comparator CP1 changes from "H" to "L", and at the same time, the one-shot timer 13 outputs a pulse of the active level "L", so that the transistors Tr3 and Tr4 have the timing t21 shown in FIG. Turns on at t23. At this time, since the logic power supply Vcc is applied to the control terminals of the transistors Tr3 and Tr4, the high side switch SH is turned on and the low side switch SL is turned off, as in the above embodiment. Since the high-side switch SH is on at the timing immediately before the timings t21 and t23 at which the one-shot timer 13 outputs the pulse of the active level "L", the high-side switch SH is turned on at the timings t21 to t22 and t23 to t24. The switch SH continues to be in the on state. In other words, the one-shot timer 13 turns on the high-side switch SH for a predetermined time t21 to t22 and t23 to t24 even if the switch controller 5 issues an off command from the state where the high-side switch SH is turned on. It means that the state is continuing.

If the harnesses H1 and H2 are normally connected, at timings t21 and t23 when the output of the comparator CP1 falls, a current flows through the freewheeling diode D1 and the voltage of the downstream terminal 1b rises. The arithmetic device 203 acquires the voltage V2 of the downstream terminal 1b from the downstream terminal voltage acquisition terminal 3e, determines whether or not this voltage has reached the threshold voltage Vt, and determines that it is normal if the voltage has reached the threshold voltage Vt.

In the abnormal state where the high-impedance harness H2 is short-circuited to the ground node NS, the voltage V2 at the downstream terminal 1b does not rise even at the timings t25 and t27 when the output of the comparator CP1 falls. Therefore, the arithmetic device 203 determines that the voltage V2 of the downstream terminal 1b has not reached the threshold voltage Vt at the timings t25 to t26 and t27 to t28, and thus determines that there is an abnormal state. This operation is the same when the harness H1 having a low impedance is short-circuited to the ground.

Therefore, according to the present embodiment as well, the same operational effects as those of the above-described embodiments can be obtained. Moreover, the one-shot timer 13 keeps the high-side switch SH turned on for a predetermined time even if the high-side switch SH is turned off by the switch control unit 5 and an off command is issued. Therefore, the low-side switch SL is off-controlled during this synchronization. For this reason, the arithmetic unit 203 can be controlled without generating the on/off command timing of the transistors Tr3 and Tr4, and the arithmetic unit 203 can be controlled by the control method of the abnormality confirmation control unit 9 shown in the first embodiment. Eliminates the need to incorporate.

(Other embodiments)
The present invention is not limited to the above-mentioned embodiment, and the following modifications or expansions are possible. The configurations of the above-described embodiments can be appropriately combined and applied.

The voltage detection unit 6 of the arithmetic units 3 and 203 has shown the mode in which the voltage of the downstream terminal 1b is directly acquired through the downstream terminal voltage acquisition terminal 3e, but the voltage V2 of the downstream terminal 1b is concerned with the voltage through the resistance voltage dividing circuit. You may make it acquire and detect the voltage proportional to V2.

The arithmetic unit 3 has shown the mode in which the high-side switch SH is turned on at the timing when the low-side switch SL is turned off by the abnormality confirmation control unit 9, but at this time, the high-side switch SH may be kept off.

The reference numerals in parentheses in the claims indicate the correspondence with the specific means described in the above-described embodiments as one aspect of the present invention, and do not imply a technical scope of the present invention. It is not limited.

In the drawing, reference numeral 1, 201 is an electronic control device, 1a is an upstream terminal, 1b is a downstream terminal, 3203 is a computing device, 5 is a switch control unit, 6 is a voltage detection unit, 9 is an abnormality confirmation control unit, and 13 is one. A shot timer (timer, abnormality confirmation control unit), SH is a high side switch, SL is a low side switch, and D1 is a free wheeling diode.

Claims (6)

An electronic control device for driving an inductive load for a vehicle, which is connected using a harness between an upstream terminal (1a) and a downstream terminal (1b),
A high side switch (SH) connecting between a power supply voltage supply node (NB) and the upstream terminal (1a),
A low-side switch (SL) connecting between a ground node (NS) to which a ground potential lower than the power supply voltage supplied to the power supply voltage supply node is applied and a downstream terminal of the inductive load;
A switch controller that normally keeps the low-side switch normally turned on and normally turns on/off the high-side switch in response to applying a pulse signal for duty control to the high-side switch during normal operation. (5),
When confirming an abnormality, an abnormality confirmation control unit (9, 13) that turns off the low side switch and turns on or off the high side switch during a period in which the high side switch is normally off,
An abnormality detection unit (8) for detecting a short circuit of the downstream terminal to the ground node (NS) when the low-side switch is turned off, and a load drive control device for a vehicle. The vehicle load drive control device according to claim 1,
The load drive control device for a vehicle, wherein the abnormality confirmation control unit turns off the low side switch and turns on the high side switch during a period in which the high side switch is normally turned off. The load drive control device for a vehicle according to claim 1 or 2,
A free wheeling diode (D1) reversely connected between the power supply voltage supply node and the low side switch;
A voltage detection unit (6) for acquiring the voltage of the downstream terminal or a voltage proportional to this voltage,
The vehicle load drive control device, wherein the abnormality detection unit detects a short circuit to the ground node of the downstream terminal according to the voltage of the downstream terminal detected by the voltage detection unit or a voltage proportional to this voltage. The vehicle load drive control device according to any one of claims 1 to 3,
The abnormality confirmation control unit (9) is configured to instruct timing of off control of the low side switch and on control of the high side switch,
The abnormality detection unit detects a short circuit to a ground node in response to a change in the downstream terminal or a proportional voltage thereof in response to the on/off switching of the low-side switch during a timing commanded period from the abnormality confirmation control unit. Load drive control device for a vehicle. The vehicle load drive control device according to any one of claims 1 to 3,
The abnormality confirmation control unit (13) keeps the high-side switch on for a predetermined time even if the high-side switch is turned off by the switch control unit and keeps the high-side switch on for a predetermined time. And a timer (13) for turning off the low-side switch for the same period as the period in which the on-state is continued,
The load drive control device for a vehicle, wherein the abnormality detection unit detects a short circuit to the ground node in response to a change in the downstream terminal or a voltage proportional thereto in response to switching on/off of the low side switch by the timer. The vehicle load drive control device according to any one of claims 1 to 5,
A vehicle load drive control device configured to turn off the high side switch to perform fail safe when the abnormality detection unit detects a short circuit to a ground node.

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