JP3509197B2 - Drive device for inductance load - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for driving an inductance load with a constant current, and more particularly to a reverse connection protection function for preventing a reverse current from flowing in an internal circuit when a direct current power source is connected in the reverse direction. The present invention relates to a drive device for an inductance load that the user has.

[0002]

2. Description of the Related Art Conventionally, as one of drive devices for driving an inductance load (hereinafter, simply referred to as an L load) such as an electromagnetic actuator or an electromagnetic valve in an automobile, for example, an actuator has been used. A constant current drive type device is known in which a current path is switched at high speed to control a constant current flowing to an L load in order to keep a position, an opening of a solenoid valve, and the like constant.
In this type of device, high-frequency noise (so-called radio noise) occurs due to switching of the current path. Therefore, in order to remove this radio noise, connect a capacitor for removing radio noise to the power line of the L load. Is being carried out.

On the other hand, this type of driving device normally operates by receiving power supply from a DC power supply common to the L load, but since various electronic parts such as transistors are provided inside the driving device, the DC power supply is used. When is connected in the reverse direction, if a reverse current flows in the internal circuit, the internal electronic components may be damaged. Therefore, conventionally, in this type of drive device,
It is also practiced to provide a diode for preventing reverse current from flowing in the internal circuit even when the DC power source is connected in the reverse direction.

However, when such a reverse connection protection function is added to the L load drive circuit having the above-mentioned radio noise removing capacitor, when the DC power supply is cut off by a power switch or the like, the capacitor becomes a capacitor. The negative voltage may be charged, and the internal electronic parts may be deteriorated or destroyed.

The problems of such a conventional L load driving device will be described in detail below with reference to FIG. In addition,
FIG. 6 shows a solenoid valve as an L load (specifically, a solenoid valve) used for controlling the amount of hydraulic oil sent to a hydraulic timer of a column fuel injection pump for injecting fuel into a diesel engine in an automobile. 3 is an electric circuit diagram showing an example of an electronic control unit (ECU) 10 for opening and closing the solenoid 2) of FIG.

As shown in FIG. 6, in an automobile, the negative side of a battery 4 which is a direct current power source is normally grounded to the vehicle body as a ground electrode common to in-vehicle electrical equipment, and the positive side of the battery 4 serves as a power switch. 6 is connected to the power supply line routed inside the vehicle, the solenoid 2 or the ECU 10, which is an L load, or another electric load 8 is connected to the battery 4 via this power supply line.
The positive electrode side of is connected.

Therefore, in the ECU 10, the collector of the drive circuit 12 for energizing the solenoid 2 is connected to the end of the solenoid 2 opposite to the power supply line (that is, the negative electrode side) via the connection terminal BL. , An NPN-type transistor T whose emitter is grounded via a resistor R1
r1 is for driving the solenoid valve (in other words, for energizing the solenoid)
It is provided as a switching element of.

Further, when the transistor Tr1 is switched from on to off and the energization of the solenoid 2 is cut off, a flyback voltage is generated on the negative electrode side of the solenoid 2 due to the energy accumulated during energization. A flyback circuit 14 is provided which prevents the transistor Tr1 from being destroyed by the flyback voltage and forms a flyback current path for returning the energy to the battery 4 side. Since the flyback circuit 14 needs to flow the energy generated in the solenoid 2 as a flyback current in only one direction from the negative electrode side to the positive electrode side of the solenoid 2, the positive electrode side of the solenoid 2 (in other words, the power supply line). Connection terminal BF connected to
And the connection terminal B to which the negative electrode side of the solenoid 2 is connected.
It is provided between L and L, and a diode D1 for regulating the current direction is provided inside thereof.

On the other hand, the ECU 10 is provided with a detection circuit 16 for inputting a rotation signal from a rotation sensor for detecting the number of revolutions of an engine or a fuel pump, a detection signal from a sensor or a switch for detecting its operating state, and a buffer. Circuit 1
7 and 18, a microcomputer that calculates the opening / closing valve timing of the solenoid valve based on these various input signals and generates a drive signal VCOM2 for switching between energization and de-energization of the solenoid 2 (hereinafter, simply referred to as CPU). 20, C
Transistor T according to drive signal VCOM2 from PU20
A constant current circuit 24 for switching the energization / non-energization of the solenoid 2 by r1 and switching the transistor Tr1 at high speed when the solenoid 2 is energized to generate a control signal VCOM1 for supplying a constant current to the solenoid 2, and
A current detection circuit 22 that detects a current flowing through the drive circuit 12 and the flyback circuit 14 and feeds it back to the constant current circuit 24 is provided.

When the transistor Tr1 is switched at high speed in order to drive the solenoid 2 at a constant current as described above, high-frequency noise (radio noise) is generated by the switching. Therefore, in order to remove this radio noise, The flyback current path in the flyback circuit 14 is connected to a large-capacity (tens to hundreds of μF) noise removing capacitor C1 (aluminum capacitor or the like) whose one end is grounded.

On the other hand, the flyback current path can be formed only by the diode D1. However, even when the solenoid 2 is switched from the energized state to the non-energized state, the flyback current path causes the solenoid 2 to move. If the energy is returned to the battery side, the closing timing of the solenoid valve will be delayed due to the flyback current. Therefore, the flyback circuit 14 includes a diode D
Drive signal VCOM2 output from CPU 20 in series with 1
Thus, a PNP type transistor Tr2 that cuts off the flyback current path when the solenoid 2 is not energized is provided. Further, in the drive circuit 12, the transistor Tr1 and the transistor Tr2 are connected to the control signal VCOM1 and the drive signal VCO.
When the flyback voltage is generated on the negative side of the solenoid 2 by turning off by M2, the Zener diode Z turns on the transistor Tr1 by the flyback voltage.
D is provided.

That is, the energization of the solenoid 2 is stopped,
When closing the solenoid valve, the transistor Tr2 is turned off to cut off the flyback current path, and the flyback voltage generated in the solenoid 2 forcibly turns on the transistor Tr1 via the Zener diode ZD. The energy stored in the solenoid 2 is promptly absorbed by the transistor Tr1. As a result, the solenoid current falls quickly and the solenoid valve can be closed quickly.

The diode D1 and the transistor Tr
The resistor R2 provided between the current detecting circuit 22 and
Is a resistance for current detection for detecting the current. Next, in the automobile, the battery 4 is charged by the alternator and, conversely, is discharged by driving various electric loads, so that the battery voltage VB pulsates. Therefore, when the capacitor C1 for removing high frequency noise is provided in the flyback current path as described above, the capacitor C1 is repeatedly charged and discharged due to the pulsation of the battery voltage VB, and the capacitor C1 easily deteriorates. To prevent this, the capacitance of the capacitor C1 must be further increased.

Therefore, in order to solve these problems,
In the flyback circuit 14, between the capacitor C1 and the connection terminal BF (that is, the positive electrode side of the solenoid 2, and hence the power supply line), the current direction of the flyback current is the forward direction (that is, the anode is the capacitor C1 side). And the cathode is on the terminal BF side), and the diode D2 is provided. As a result, due to the diode D2, the charging / discharging of the capacitor C1 due to the ripple voltage of the battery 4 is reduced, and the capacitance of the capacitor C1 can be reduced.

On the other hand, the ECU 10 is provided with a power supply circuit 26 for supplying power to the internal circuit. The power supply circuit 26 includes a connection terminal BP connected to the positive side (that is, the power supply line) of the battery 4 via the key switch 6 and a connection terminal GND connected to the negative side (that is, the vehicle body) of the battery 4. When the key switch 6 is turned on, power is supplied from the battery 4 to generate a constant voltage (driving voltage) V2 for driving the internal circuit, and a capacitor C2 for voltage stabilization is provided.

In general, the reverse connection protection function is, as shown in FIG. 6, a diode having a connection terminal BP side as an anode in a current path from the connection terminal BP connected to the positive side of the battery 4 to the power supply circuit 26. This is realized by providing D4 or, conversely, providing a diode with the connection terminal GND as a cathode in the current path from the connection terminal GND connected to the negative electrode side of the battery 4 to the power supply circuit 26. In the circuit shown in FIG. 6, the reverse connection of the battery 4 prevents the reverse current (that is, the current from the emitter side to the collector side) of the transistor Tr1 in the drive circuit 12 to flow. A diode D3 for reverse connection protection is also provided between the connection terminal BL connected to the negative electrode side of the solenoid 2 and the connection terminal BL as an anode.

However, in the case where the ECU 10, in other words, the L load drive circuit is configured as described above, the key switch 6 is turned off when the solenoid 2 is energized, so that a negative surge (negative electric Noise), the diode D2
A current flows from the side of the capacitor C1 to the solenoid 2 via the, and the capacitor C1 is charged with a negative voltage.

That is, since the power supply circuit 26 is provided with the capacitor C2 for stabilizing the voltage, the drive voltage V2 is supplied to the internal circuit for a certain period even after the key switch 6 is turned off. Therefore, even if the key switch 6 is turned off while the transistor Tr1 is turned on and the solenoid 2 is energized, the transistor Tr1 is turned on and the solenoid 2 is energized by the operation of the internal circuit for a certain period thereafter. . However, at this time, since the key switch 6 has already been turned off, power cannot be supplied to the solenoid 2 from the power supply line, and a current is supplied to the solenoid 2 from the capacitor C1 so that the capacitor C1 becomes a negative voltage. It will be charged.

Next, when the capacitor C1 is charged to a negative voltage as described above, there is no problem if the negative voltage charged to the capacitor C1 can be discharged thereafter. However, the negative voltage discharge path of the capacitor C1 (in other words, the positive voltage charge path) is completely cut off by the diode D2 and the transistor Tr2, so that the capacitor C1 remains charged with the negative voltage. It is held until the next driving of the solenoid 2.

If the capacitor C1 is charged with a negative voltage in this way and if the voltage exceeds the withstand voltage values of the capacitor C1, the transistor Tr2, and the diode D2, these elements may be damaged. , In addition,
When the flyback current flows and the capacitor C1 is charged from the negative voltage to the battery voltage, the transistor Tr
An overvoltage may be applied between the collector and the emitter of the transistor No. 2 to deteriorate the transistor Tr2.

If there is no diode for reverse connection protection, such a problem can be easily solved by connecting the diode between the connection terminals BP and GND with the anode on the side of the connection terminal GND. That is, if a diode is provided between the connection terminals BP and GND in this way, the negative surge generated in the solenoid 2 when the key switch 6 is off can be absorbed by this diode, so that no current flows from the capacitor C1 to the solenoid 2. Without a capacitor C
It is possible to prevent the negative voltage from being charged to 1. However, when the diode is provided to realize the reverse connection protection function, the diode cannot absorb the negative surge, and the above problem occurs.

The present invention has been made in view of these problems. When the reverse connection protection function is added to a device having a capacitor for removing radio noise generated due to constant current driving of an inductance load as described above. Another object is to prevent the negative voltage from being charged / held in the capacitor due to the negative surge that occurs in the L load when the power is cut off.

[0023]

In order to achieve the above object, the invention according to claim 1 is characterized in that one end is connected to the positive electrode side of the DC power source through the power switch and the other end is connected to the positive electrode side of the DC power source. A driving switching element that conducts / blocks a current path leading to the negative electrode side of the DC power supply according to a control signal from the outside to drive the above-mentioned inductance load at a constant current, and the driving switching element from a conducting state by the control signal. When switched to the cutoff state,
A flyback current path that allows a flyback current to flow from the negative electrode side to the positive electrode side of the inductance load; a flyback current interruption switching element that conducts and interrupts the flyback current path according to an external command signal; When the switching element for shutting off the back current is in the shut-off state, the flyback voltage generated on the negative side of the inductance load causes the driving switching element to conduct, thereby rapidly reducing the flyback voltage. A reduction element, a high-frequency noise component generated in the flyback current path, provided between the flyback current path from the flyback current interruption switching element to the positive side of the inductance load and the negative side of the DC power supply. For removing noise, and the noise The current direction of the flyback current is provided as a forward direction on the flyback current path from the connection point between the leaving capacitor and the flyback current path to the positive electrode side of the inductance load, and from the voltage fluctuation of the DC power supply, Has a protection diode that protects the noise removal capacitor and a capacitor for voltage stabilization.
A power supply circuit that receives power from the DC power supply via the power switch to generate a constant voltage for driving an internal circuit,
The device is connected in the reverse direction to the DC power source,
A reverse connection protection semiconductor element that prevents reverse current from flowing in the internal circuit of the device, and a resistor for absorbing negative voltage is connected in parallel to the noise removing capacitor. Is characterized by.

Further, the invention described in claim 2 is, in the drive device of the inductance load according to claim 1, wherein the resistor for charging the noise removing capacitor is connected in parallel to the protective diode. It is characterized by According to a third aspect of the present invention, in the drive device for the inductance load according to the first or second aspect, the flyback current path is connected in series with a resistor connected in parallel to the noise removing capacitor. It is characterized by connecting diodes with the direction of the current flowing to the side as the forward direction.

[0025]

In the drive device for the inductance load according to claim 1, which is configured as described above,
The inductance load is driven with a constant current by the conduction / interruption of the driving switching element. When the drive switching element is switched from the conductive state to the cutoff state, a flyback current flows from the negative side of the inductance load to the positive side through the flyback current path,
The energy stored when the inductance load is energized is
It is returned to the positive electrode side of the inductance load, and further to the DC power source side.

Further, the flyback current path is provided with a flyback current interruption switching element that conducts / interrupts in response to an external command signal. When the switching element is in the interruption state, the inductance load When the flyback voltage is generated on the negative electrode side, the flyback voltage rapid reduction element makes the driving switching element conductive, and the flyback voltage is rapidly reduced. As a result, if the flyback current cutoff switching element is turned on when the driving of the inductance load is stopped, the current flowing through the inductance load can be quickly reduced.

On the other hand, since the drive switching element drives the inductance load with a constant current, it is switched at high speed by the control signal, and high frequency noise is generated by this switching operation. A noise removal capacitor is provided between the flyback current path from the inductor to the positive side of the inductance load and the negative side of the DC power supply, so noise generated by the switching operation of the drive switching element is removed. It

When the noise removing capacitor is directly connected to the positive electrode side of the inductance load (in other words, DC power supply), the noise removing capacitor is charged and discharged due to the voltage fluctuation of the DC power supply and deteriorates. However, a protection diode is provided on the flyback current path from the connection point between the noise removal capacitor and the flyback current path to the positive side of the inductance load with the current direction of the flyback current as the forward direction. Because
The noise removing capacitor is protected from the voltage fluctuation of the DC power supply by this diode.

Furthermore, in the drive device for the inductance load of the present invention, a power source is provided which has a capacitor for stabilizing the voltage and which receives power from a DC power source via a power switch to generate a constant voltage for driving an internal circuit. Circuit and
A reverse connection protection semiconductor element is provided which prevents a reverse current from flowing in an internal circuit of the device when the device is connected in the reverse direction to a DC power source.

Therefore, when the power switch is cut off while the driving switching element is conducting and the inductance load is being driven, the internal circuit of the device is charged by the electric charge accumulated in the capacitor in the power circuit. , It will continue to operate for a while, and the inductance load will continue to be energized. In this state, since power is not supplied to the inductance load, a negative surge occurs in the inductance load. Also, since the semiconductor device for reverse connection protection is built in the device, only the noise removing capacitor can absorb this negative surge, and the noise removing capacitor becomes negative voltage due to the negative surge of the inductance load. Be charged.

However, in the present invention, since a resistor for absorbing negative voltage is connected in parallel to the noise removing capacitor, even if the noise removing capacitor is once charged to a negative voltage, then The negative voltage of the noise removing capacitor is discharged with a time constant determined by the capacity of the capacitor and the resistance value of the resistor.

As a result, the negative voltage charged in the noise removing capacitor may damage switching elements for flyback current interruption, protective diodes, and other elements provided in the flyback current path. When the back current flows and the noise removing capacitor is charged from the negative voltage to the battery voltage, the over voltage is not applied to the flyback current cutoff switching element and this element is not deteriorated. The durability can be improved.

Further, in a drive device for an inductance load according to a second aspect of the present invention, a resistor for charging a noise removing capacitor is connected in parallel with a protective diode provided in a flyback current path. ing. This is because when a resistor is provided in parallel with the noise removing capacitor as described in claim 1, it is possible to prevent the negative voltage from being charged and held in the capacitor due to the negative surge of the inductance load. However, this is because the electric charge accumulated in the capacitor is discharged by the resistor during the normal inductance load driving, especially during the driving for a short time in which no flyback current is generated.

That is, when the noise removing capacitor is charged and discharged due to the presence / absence of the flyback current, the capacitor deteriorates. Therefore, by providing a resistor in parallel with the protection diode, the terminal voltage of the capacitor is controlled by the power source. The voltage can be held at a voltage value divided by these two resistors to prevent the noise removing capacitor from discharging. As a result, according to the present invention, the durability of the noise removing capacitor can be improved. It is desirable that the resistance values of the two resistors be larger than the resistance value connected in parallel with the noise removing capacitor. That is, in this way, the voltage of the noise removing capacitor can be brought closer to the power supply voltage, and the durability of the noise removing capacitor can be further improved.

Next, in the drive device for an inductance load according to a third aspect of the present invention, the direction of the current flowing on the flyback current path side is further serially connected to the resistor connected in parallel to the noise removing capacitor. The diode is connected in the forward direction. Therefore, according to the present invention,
With this diode, the discharge current path due to the resistor connected in parallel to the noise removing capacitor can be cut off, and the discharge of the noise removing capacitor can be blocked.

If this diode is combined with the resistor according to the second aspect of the present invention, the voltage of the noise removing capacitor can always be kept at the power supply voltage, which is more effective.

[0037]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows the electronic control unit (EC) of FIG. 6 described in the section “Prior Art and Problems to be Solved by the Invention”.
U) 10 is a resistor R for absorbing negative voltage according to claim 1.
2 illustrates the device configuration of the embodiment in which A is provided. This device has the same configuration as that of the device of FIG. 6 except for the resistor RA, and the operation of each part thereof is also the same as that described above. Therefore, in the following description, the action of the resistor RA will be described.・ Explain only the difference in effect.

As shown in FIG. 1, the resistor RA is connected in parallel with a capacitor C1 for removing high frequency noise provided in the flyback circuit 14. An electronic control unit (ECU) 1 as an L load driving device as in this embodiment
At 0, as shown in FIG. 2 (a), when the solenoid valve is normally driven, the CPU 20 energizes the solenoid 2 to open the solenoid valve. When the valve is closed, the drive signal VCOM2 which is low level is output, and the transistor Tr2 as a flyback current cutoff switching element in the flyback circuit 14 is turned on / off according to the drive signal VCOM2. It That is, the transistor Tr2 is turned on to be in a conductive state when the solenoid valve is opened, and is turned off to be in a cutoff state when the solenoid valve is closed.

The drive signal VCOM2 is also input to the constant current circuit 24. In the constant current circuit 24, when the drive signal VCOM2 is at the high level, the current detection circuit 22 detects the current, and The transistor Tr1 in the drive circuit 12 is controlled so that the solenoid current I becomes a constant current.
To turn on and off. That is, when the drive signal VCOM2 becomes high level, the high level control signal VCOM1 is output to the drive circuit 12 to turn on the transistor Tr1 until the solenoid current I reaches a predetermined current, and then the predetermined current is reached. , A control signal VCOM1 for switching the transistor Tr1 at high speed by using the built-in oscillation circuit
Is output to hold the solenoid current I at a constant current.
When the drive signal VCOM2 becomes low level, the control signal VCOM1 is set to low level to stop driving the transistor Tr1, in other words, energize the solenoid 2.

On the other hand, when the drive signal VCOM2 becomes low level and the transistors Tr1 and Tr2 are turned off, the flyback voltage generated in the solenoid 2 causes the Zener diode ZD (flyback voltage rapid reduction element) to break down, The transistor Tr1 is turned on and the flyback voltage drops. As a result, the solenoid current I also falls quickly and the solenoid valve is closed promptly.

If a flyback current is flowing at the time of switching the transistor Tr1, the voltage V1 of the capacitor C1 is maintained at approximately the battery voltage VB by this flyback current. Further, when the key switch 6 is turned on, a constant drive voltage V2 is supplied to each circuit by the operation of the power supply circuit 26.

By the way, the electronic control unit (EC
U) 10, in the device having the voltage stabilizing capacitor C2 in the power supply circuit 26, when the key switch 6 as the power supply switch is turned off, as shown in FIG. The electric charge accumulated in the capacitor C2 in the circuit 26 supplies power to the internal circuit for a certain time Th thereafter. If the solenoid 2 is energized at this time, a negative surge is generated in the solenoid 2 at the same time when the key switch 6 is turned off, a current flows from the capacitor C1 to the solenoid 2, and the voltage V1 of the capacitor C1 becomes a negative voltage. Become. However, in this embodiment, since the resistor RA is connected in parallel to the capacitor C1, even if the capacitor C1 is once charged to a negative voltage due to a negative surge,
After that, the negative voltage of the capacitor C1 is discharged with a time constant determined by the capacitance of the capacitor C1 and the resistance value of the resistor RA.

Therefore, according to the device of this embodiment, the voltage V1 of the capacitor C1 becomes a negative voltage until the next time when the solenoid 2 is energized, unlike the device shown in FIG. 6 in which the resistor RA is not provided. It is not held, and the transistor Tr is turned on by the negative voltage charged in the capacitor C1.
When the capacitor C1 is charged to the battery voltage VB by the flyback current due to the damage of the diode 2 and the diode D2 or the next energization of the solenoid 2, the overvoltage is applied to the transistor TR2. It is possible to prevent the transistor TR2 from deteriorating. Therefore, according to this embodiment, the durability of the device can be improved.

Next, FIG. 3 shows the configuration of the flyback current path when the resistor RB according to claim 2 is provided in parallel with the diode D2 in the flyback circuit 14 shown in FIG. There is. When the resistor RB is provided in parallel with the diode D2 in this way, the solenoid 2 is driven with a low duty drive signal V that does not generate a flyback current.
When the energization is controlled by COM2, the voltage V1 does not become "0" without charging the capacitor C1.

That is, in a device such as the device shown in FIG. 1 in which the resistor RB is not provided and only the resistor RA is provided in parallel with the capacitor C1, the negative surge to the capacitor C1 is caused by the negative surge of the solenoid 2. Although it is possible to prevent the voltage from being charged and held, as shown in FIG. 4, when the solenoid 2 is energized for a short time (low duty) so that a flyback current does not occur, the resistor RA causes , The electric charge accumulated in the capacitor C1 has been discharged, and as shown by the dotted line in FIG.
Becomes "0". However, as in this embodiment,
When the diode D2 is provided with the resistor RB, as shown by the solid line in FIG. 4, the voltage V1 of the capacitor C1 is a constant voltage (VB × RA) obtained by dividing the battery voltage VB by the resistor RA and the resistor RB. / (RA + RB)), and it is possible to prevent the capacitor C1 from being completely discharged. Therefore, according to the present embodiment, it is possible to suppress the voltage fluctuation of the capacitor C1 and improve the durability of the capacitor C1.

In order to prevent the capacitor C1 from being discharged by the resistor RA when the solenoid 2 is driven by the low duty drive signal VCOM2, it is not always necessary to use the resistor RB. A diode DA may be provided in series with the resistor RA, with the flyback current path side as the cathode, as shown in FIG. That is, in this way, the diode DA can interrupt the discharge current path formed by the resistor RA from the capacitor C1 to the ground line, and can prevent the discharge of the capacitor C1. is there.

In addition, in the device shown in FIG.
It is also possible to provide both A and resistor RB. And
In this case, the capacitor C1 is connected to the battery 4 via the resistor RB, and the discharge current path of the capacitor C1 is cut off by the diode DA, so that the voltage V1 of the capacitor C1 can be held at the battery voltage VB. It will be possible.

In the present embodiment, the NPN transistor Tr1 is used as the driving switching element and the PNP transistor Tr2 is used as the flyback current cutoff switching element.
Any commonly used switching element such as ET and triac can be used without any problem.

[Brief description of drawings]

FIG. 1 is an electronic control unit (EC for driving a solenoid valve of an embodiment)
It is an electric circuit diagram showing the composition of U).

FIG. 2 is a time chart explaining the operation of the electronic control unit (ECU) shown in FIG.

FIG. 3 is an electric circuit diagram showing a second configuration example of a flyback circuit.

FIG. 4 is a time chart explaining the effect of the flyback circuit shown in FIG.

FIG. 5 is an electric circuit diagram showing a third configuration example of a flyback circuit.

FIG. 6 is a conventional electronic control unit (ECU) for driving a solenoid valve.
3 is an electric circuit diagram showing a configuration example of FIG.

[Explanation of symbols]

2 ... Solenoid (L load) 4 ... Battery (DC power supply) 6 ... Key switch (power switch) 10 ... Electronic control unit (ECU) 12 ... Drive circuit 14 ... Flyback circuit 22 ...
Current detection circuit 24 ... Constant current circuit 26 ... Power supply circuit C1 ... Capacitor (for noise removal) C2 ... Capacitor (for voltage stabilization) D1 ... Diode (for flyback current path) D2 ... Diode (for protection) D4 ... Diode ( Reverse connection protection) RA ... Resistor RB ... Resistor DA ... Diode Tr1 ... Transistor (driving switching element) Tr2 ... Transistor (flyback current interruption switching element) ZD ... Zener diode (flyback voltage rapid reduction element)

Claims (3)

(57) [Claims] 1. A current path from an other end of an inductance load, one end of which is connected to a positive electrode side of a DC power source via a power switch, to a negative electrode side of the DC power source, is conducted / interrupted according to a control signal from the outside. A driving switching element for driving the inductance load at a constant current, and a flyback current from the negative side to the positive side of the inductance load when the driving switching element is switched from a conduction state to a cutoff state by the control signal. A flyback current path for flowing a current, a flyback current interrupting switching element that conducts and interrupts the flyback current path in response to an external command signal, and a flyback current interrupting switching element , The drive switch by the flyback voltage generated on the negative side of the inductance load A flyback voltage rapid reduction element for rapidly reducing the flyback voltage by conducting a switching element, a flyback current path from the flyback current interruption switching element to the positive electrode side of the inductance load, and the DC power supply. A noise removing capacitor provided between the flyback current path and the negative electrode side, for removing high frequency noise components generated in the flyback current path, and a positive electrode of the inductance load from a connection point between the noise removing capacitor and the flyback current path. Is installed on the flyback current path to the side with the current direction of the flyback current as the forward direction, and a protection diode that protects the noise removal capacitor from the voltage fluctuation of the DC power supply and a voltage stabilization capacitor are provided. Has a power supply from the DC power supply via the power switch. A power supply circuit for generating a constant voltage for the internal circuit drive Te, the device is connected in the opposite direction to the DC power source,
A semiconductor element for reverse connection protection that prevents reverse current from flowing in an internal circuit of the device, and further, in parallel with the noise removing capacitor,
A drive device for an inductance load, comprising a resistor for absorbing negative voltage. 2. The drive device for an inductance load according to claim 1, wherein a resistor for charging the noise removing capacitor is connected in parallel with the protective diode. 3. A diode is connected in series with a resistor connected in parallel to the noise removing capacitor, with a current flowing on the flyback current path side as a forward direction. Or the drive device of the inductance load according to claim 2.