JP2002319506A - Solenoid drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of wire harness to a solenoid by improving constitution of a solenoid drive device. SOLUTION: A resistor 32 for current detection is connected with the other end of the solenoid 30 whose one end is connected with ground G. An NMOS 33 and the cathode of a diode 34 are connected with the resistor 32. The anode of the diode 34 is connected with the ground G. When the NMOS 33 is turned on, a current flows in the solenoid 30 from a battery 31 via the resistor 32. When the NMOS 33 is turned off, a regenerative current flows in the solenoid 30 from the ground G via the diode 34 and the resistor 32. As a result, current driving of the solenoid 30 is enabled without connecting the anode of the diode 34 with the solenoid 30 by using a lead wire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solenoid driving device for driving a solenoid incorporated in an automobile or the like by supplying a current thereto.

[0002]

2. Description of the Related Art In recent years, in order to perform high-accuracy and high-speed control, electronic components for control are mounted and electronic control is performed. For example, in an automatic transmission (automatic vehicle), hydraulic pressure is used to realize the automatic transmission.
2. Description of the Related Art An automatic vehicle is equipped with a solenoid for controlling hydraulic pressure and a solenoid drive device for supplying a current to the solenoid.

[0003] As a technique related to a solenoid drive device mounted on an automobile or the like, for example, Japanese Patent Application Laid-Open No. 3-177668 is disclosed.
JP, JP-A-4-50550, or JP-A-8-50
There is one described in JP-A-240277. FIG.
FIG. 1 is a configuration diagram showing a conventional solenoid driving device disclosed in the above-mentioned document. This solenoid drive device drives the solenoid 10 by passing a current through it. The battery 11 has a negative electrode connected to the ground, and an N-channel MOS transistor (a switching element having a drain connected to the positive electrode of the battery 11) as a switching element. (Hereinafter referred to as NMOS)
12 are provided.

A control circuit 13 is connected to the gate of the NMOS 12.
Supplies a control signal S12. The source of the NMOS 12 is connected to the cathode of the diode 14 and one end of the solenoid 10. The anode of the diode 14 is connected to ground, and the other end of the solenoid 10 is connected to a resistor 1
5 is connected to one end. The other end of the resistor 15 is connected to the ground. The resistor 15 is a current detection circuit for detecting a current flowing through the solenoid 10, and the resistor 15
Are connected to the positive-phase input terminal (+) and the negative-phase input terminal (−) of the amplifier 16.

[0005] The output terminal of the amplifier 16 is connected to one end of a resistor 17. The other end of the resistor 17 is connected to a capacitor 18
, And the other electrode of the capacitor 18 is connected to the ground.

FIGS. 9A to 9D are waveform diagrams showing the operation of the solenoid driving device shown in FIG. 8. The operation of the conventional solenoid driving device will be described with reference to FIG. In this solenoid driving device, the control circuit 13
As shown in (a), a control signal S that repeats a high level (hereinafter, referred to as “H”) and a low level (hereinafter, referred to as “L”)
13 is supplied to the gate of the NMOS 12. Control signal S1
When “3” is “H”, the NMOS 12 is turned on, and the one end 10 a of the solenoid 10 is connected to the positive electrode of the battery 11.
When one end 10 a is connected to the positive electrode of the battery 11, the positive electrode of the battery 11 and the solenoid 10 are connected to the solenoid 10.
And resistor 15, the current I ₁ flowing in the order of the negative electrode of the ground and the battery 11 flows.

[0007] NMOS12 the current value of the current _{I 1} immediately after on, as in FIG. 9 (b), is equal to the current value of the current flowing in the solenoid 10 immediately before NMOS12 is turned on, with time To increase. Control signal S13
Changes to "L", the NMOS 12 is turned off. NM
When the OS 12 is turned off, a back electromotive force is generated in the solenoid 10. This counter electromotive force, the anode from the ground diode 14, the cathode of the diode 14, the solenoid 10, the resistor 15 and the regenerative current I ₀ in the direction of the ground flow. The regenerative current I ₀ immediately after the NMOS 12 is turned on
Current value is the same as the current value of the current I ₁ flowing in the immediately preceding, decreases the time passes.

When the current I ₁ and the regenerative current I ₀ flow, a voltage proportional to the current flowing through the solenoid 10 is generated across the resistor 15. The amplifier 16 amplifies a voltage generated at both ends of the resistor 15 to generate a current detection signal. Since the negative-phase input terminal of the amplifier 16 is connected to the ground, the input voltage of the negative-phase input terminal is fixed to the ground voltage, and the input voltage of the positive-phase input terminal of the amplifier 16 is equal to the current I _1.
And a value proportional to the regenerative current I _0.

The amplifier 16 amplifies the difference between the voltage input to the negative phase input terminal and the voltage input to the positive phase input terminal,
A pulsating voltage is output as shown in FIG. Resistance 17
And a capacitor 18 smoothes the output voltage of the amplifier 16 as shown in FIG. 9D, and outputs a smoothed signal S17. This signal S17 is fed back to the control circuit 13, for example. The control circuit 13 changes the duty ratio of the control signal S13 with reference to the signal S17. That is, PWM control is performed. As a result, the solenoid path 1
The current flowing to zero is optimized.

[0010]

However, the conventional solenoid drive has the following problems. The control circuit 13, the NMOS 12, the resistor 15, the amplifier 16, the resistor 17, the capacitor 18 and the like of the solenoid driving device are
Usually, it is housed in the control unit 20 as shown in FIG. On the other hand, the solenoid 10 is installed at a place away from the control unit 20. Therefore, it is necessary to connect the source of the NMOS 12 and the solenoid 10 with a lead wire, and to connect between the solenoid 10 and the resistor 15 with a lead wire. That is, two lead wires are required for one solenoid 10. When driving a plurality of solenoids 10, or when the solenoid 10 and the control unit 20
When the distance between the wire harnesses is long, the amount of the wire harness increases. In that case, particularly in the case of automobiles and the like, when the amount of the wire harness is large, the weight increases by that amount, and this has contributed to the deterioration of fuel efficiency.

On the other hand, the smoothing circuit constituted by the resistor 17 and the capacitor 18 outputs an output signal S17 obtained by averaging the current flowing through the solenoid 10. Therefore, even if the current flowing through the solenoid 10 changes suddenly,
The output signal S17 of the smoothing circuit does not follow it. Therefore, when the output signal S17 of the smoothing circuit is used for controlling the driving of the solenoid 10, it is assumed that high-speed control cannot be performed.

An object of the present invention is to provide a solenoid driving device capable of reducing the amount of a wire harness.

[0013]

In order to achieve the above object, a solenoid driving device according to a first aspect of the present invention comprises:
A solenoid having one end connected to ground and a load element having one end connected to the other end of the solenoid, detects a current flowing through the load element, and outputs a current detection signal corresponding to a current flowing through the load element. A current detection circuit to be generated, connected between the other end of the load element and a power supply, repeats a process of turning on and off between the load element and the power supply, and when turned on, a current flows from the power supply to the solenoid. A switching element that drives the solenoid, and is connected between the ground and the other end of the load element, and the current generated by the back electromotive force generated in the solenoid when the switching element is turned off is output from the ground. A rectifying element for flowing the solenoid to drive the solenoid.

By employing such a configuration, the solenoid, the load element in the current detection circuit for detecting the current flowing through the solenoid, and the switching element are connected in series between the power supply and the ground. In addition, a rectifying element that allows current to flow from the ground to the solenoid when the switching element is off is connected in parallel with the load element and the solenoid between the switching element and the ground.
Therefore, one end of the solenoid and one end of the rectifying element are connected via the ground, and a closed circuit is formed in which a current flows according to the back electromotive force generated in the solenoid when the switching element is turned off. Therefore, it is not necessary to connect lead wires to both ends of the solenoid.

[0015] To achieve the above object, a second aspect of the present invention is provided.
The solenoid driving device according to the aspect of the present invention samples the current detection signal at a predetermined timing, and holds the current detection signal as a signal representing a current flowing through the solenoid during a period when the switching element is on and a period when the switching device is off. It is characterized by further comprising a sample and hold circuit. By employing such a configuration, when the current flowing through the solenoid increases or decreases, the current flowing through the solenoid also changes during the period when the switching element is on or off. Since the sample and hold circuit samples and holds the current detection signal during the period when the switching element is on or off, the change in the current flowing through the solenoid is displayed quickly.

[0016] The sample and hold circuit may sample the current detection signal when the switching element is on. Further, the sample and hold circuit may sample the current detection signal when the switching element is off.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 is a configuration diagram of a solenoid drive device according to a first embodiment of the present invention. This solenoid driving device drives the solenoid 30 incorporated in an electromagnetic valve by, for example, monitoring the current and supplying the current while monitoring the current. The battery 31 serving as a driving power source of the solenoid 30 and the current flowing through the solenoid 30 are driven by the solenoid 30. The circuit includes a resistor 32 as a load element for converting into a voltage, an NMOS 33 as a switching element, a diode 34 as a rectifier element, and an amplifier 35 which, together with the resistor 32, forms a current detection circuit.

The negative electrode of the battery 31 is connected to the ground G. One end 30a of the solenoid 30 is connected to the ground G. The other end 30b of the solenoid 30
Is connected to one end of the resistor 32. The other end of the resistor 32 is connected to the source of the NMOS 33, and the drain of the NMOS 33 is connected to the positive electrode of the battery 31.

The connection point between the drain of the NMOS 33 and the resistor 32 is connected to the cathode of the diode 34 and the positive-phase input terminal (+) of the amplifier 35. The anode of the diode 34 is connected to the ground G. The negative-phase input terminal (−) of the amplifier 35 is connected to a resistor 3
2 and the other end b of the solenoid 30.

The output terminal of the amplifier 35 is connected to the amplifier 3
5 is connected to a sample-and-hold circuit 36 for sampling and holding the output signal of No. 5. A control signal S3 for controlling ON / OFF of the NMOS 33 is provided to the gate of the NMOS 33.
7 is connected. To the control circuit 37, an arithmetic circuit 38 configured by a computer or the like and setting the sampling timing of the sample and hold circuit 36 is further connected.

Resistance 32, NMOS 33, diode 3
4, the amplifier 35, the control circuit 37, the arithmetic circuit 38, and the sample-and-hold circuit 36
0. The control circuit 37 and the NMOS
33 is incorporated in the IC (integrated circuit) 21.

FIG. 2 is a circuit diagram showing the amplifier 35 in FIG. The amplifier 35 has a resistor R1 having one end connected to the positive-phase input terminal (+), a resistor R2 having one end connected to the other end of the resistor R1, and one end connected to the negative-phase input terminal (-). And a resistor R3.

The emitter of the PNP transistor Tr1 and the emitter of the PNP transistor Tr2 are connected to the other end of the resistor R2. The collector of the transistor Tr1 is connected to the collector and the base of the NPN transistor Tr3. The emitter of the transistor Tr3 is connected to the ground G. Transistor Tr1
And the collector and the base of the transistor Tr2 are connected to a constant current source 35a.

On the other hand, the other end of the resistor R3 is connected to the emitter of the PNP transistor Tr4 and the PNP transistor Tr4.
5 are connected. Transistor Tr4
Is connected to the collector of the NPN transistor Tr6. The base of the transistor Tr6 is
The collector of the transistor Tr3 is connected, and the emitter of the transistor Tr6 is connected to the ground G. The base of the transistor Tr4 and the base and collector of the transistor Tr5 are connected to the constant current source 35a.

A base of a PNP transistor Tr7 is connected to a connection node between the collector of the transistor Tr4 and the collector of the transistor Tr6. The emitter of the transistor Tr7 is connected to a connection node between the resistors R1 and R2, and the collector of the transistor Tr7 is connected to ground via the resistor R4. The collector of the transistor Tr7 is the output terminal of the amplifier 35.

FIG. 3 is a circuit diagram showing a main part of the sample and hold circuit in FIG. Sample hold circuit 36
Includes a switch 36a having one end connected to the output terminal of the amplifier 35, and a capacitor 36b having one end connected to the other end of the switch 36a. Capacitor 36
“b” samples and holds the output voltage of the amplifier 35, and the other electrode of the capacitor 36b is connected to the ground. One end of a resistor 36c is connected to a connection node between one electrode of the capacitor 36b and the switch 36a. The switch 36a is connected to the capacitor 36
It turns on and off between b and the amplifier 35, and receives a pulse signal S38 from the arithmetic circuit 38.

FIG. 4 is a waveform diagram showing the operation of FIG.
The operation of the solenoid driving device of FIG. 1 will be described with reference to FIG. The control circuit 37, as shown in FIG.
The control signal S37 that repeats “H” and “L” is sent to the NMOS3
Give to gate 3. The NMOS 33 outputs the control signal S37
Turns on when "H" is "H", and connects between the battery 31 and the resistor 32. As a result, the resistance 3
The solenoid 30 through the 2, flows a current _{I 1} in Figure 4 (b).

When the control signal S37 is "L", the NMOS
33 turns off and cuts off the connection between the resistor 32 and the battery 31. When the NMOS 33 interrupts the connection between the resistor 32 and the battery 31, the voltage at the other end 30b of the solenoid 30 whose one end 30a is connected to the ground G is reduced by the back electromotive force, and a forward voltage is applied to the diode 34. . The diode 34 to which the forward voltage is applied becomes conductive,
The regenerative current I ₀ shown in FIG. 4B is passed from the ground G to the solenoid 30 via the resistor 32. That is, the diode 3
4. The resistor 32 and the solenoid 30 form one closed loop via the ground G. Accordingly, the solenoid 30 is driven by the current _{I 1} and the regenerative current _{I 0.}

The current I ₁ and the regenerative current I ₀ flow through the resistor 32 alternately. When the current I ₁ flows through the resistor 32, the voltage drop, both ends of the resistor 32, a potential difference is produced. Similarly, when the current I ₀ flows through the resistor 32, a potential difference is generated between both ends of the resistor 32. That is, the input voltages of the positive-phase input terminal (+) and the negative-phase input terminal (−) of the amplifier 35 are applied to FIG.
A difference as shown in FIG.

[0030] When the current I ₁ is flowing, the positive-phase input terminal (+) and the negative phase input terminal (-) is a positive voltage, and reverse phase input terminal the input voltage is positive-phase input terminal (+) It becomes higher than the input voltage (-). When the current I ₀ is flowing, the positive-phase input terminal (+) and the negative-phase input terminal (−) are negative voltages, and the input voltage of the positive-phase input terminal (+) is negative phase input terminal (−). Input voltage.

In the amplifier 35, the transistors Tr1 to Tr
r6 and the constant current source 35a function as a constant current source circuit, and operate so that the current flowing through the resistor R2 is equal to the current flowing through the resistor R3. For example, when the current I ₁ is flowing, the input voltage of the positive-phase input terminal (+) is, negative phase input terminal (-) becomes higher than the input voltage, the emitter voltage of the transistors Tr1, Tr2 increases, The voltage between the base and the emitter of the transistors Tr1 and Tr2 increases. As a result, the current flowing through the resistor R2 increases. When the current flowing through the resistor R2 starts increasing, the current flowing through the resistor R3 decreases, and the base voltage of the transistor Tr7 decreases.

When the base voltage of the transistor Tr7 decreases, the base-emitter voltage of the transistor Tr7 increases, and the emitter current of the transistor Tr7 increases. As a result, the current flowing through the resistor R2 is reduced, and the currents flowing through the resistor R3 and the resistor R2 become equal.
Transistor Tr7 with increased base-emitter voltage
Flows the collector current to the ground through the resistor R4.
The resistor R4 generates a voltage corresponding to the collector current of the transistor Tr7 and outputs it as a current detection signal S35.

[0033] When the current I ₀ is flowing, the input voltage and the negative phase input terminal of the positive-phase input terminal (+) (-) since the input voltage is negative, the constant current source formed by transistor Tr1~Tr6 The circuit does not operate, and the output signal S35 of the amplifier 35 is fixed at a voltage near the ground G.

When the control signal S37 output from the control circuit 37 is "H", the arithmetic circuit 38 outputs a pulse signal S38 indicating the timing at which the sample-and-hold circuit 36 performs sampling, as shown in FIG. I do.

Switch 3 in sample and hold circuit 36
6a, as shown in FIG. 4 (f), turns on while the pulse signal S38 is "H", and charges the capacitor 36b with the voltage of the current detection signal S35. The capacitor 36b charged with the voltage of the current detection signal S35 holds and outputs the charged voltage. The resistor 36c prevents the capacitor 36b from discharging and changing the charging voltage.

As described above, in the first embodiment,
It has the following advantages. (1) Since one end of the solenoid 30 is connected to the ground G, the number of lead wires connecting the solenoid 30 to the control unit 20 is reduced to one. Therefore, the amount of the wire harness can be reduced, and the increase in weight when there are many solenoids 30 can be minimized. (2) A sample hold circuit 36 is provided, and a signal representing a current flowing through the solenoid 30 is supplied to the sample hold circuit 3.
Since so as to output the 6, current I ₁ flowing through the solenoid 30 is also changed, it is possible to indicate quickly the change.

[0037] The (3) sample and hold circuit 36, since the output signal S35 in amplifier 35 in a period in which current I ₁ is flowing to sample, there is no need to use an amplifier 35 that can cope with the negative input voltage . Therefore, the amplifier 35 can be configured with a simple configuration as shown in FIG.

[Second Embodiment] FIG. 5 shows a second embodiment of the present invention.
It is a configuration diagram of a solenoid drive device showing an embodiment of,
Elements common to those in FIG. 1 of the first embodiment are denoted by common reference numerals. This solenoid drive is
The amplifier 35 of the first embodiment is replaced with a new amplifier 40, and the arithmetic circuit 38 of the first embodiment is replaced with an arithmetic circuit 41. Other configurations are the same as those of FIG. I have. The other end 30b of the solenoid 30 and the resistor 32
The negative-phase input terminal (−) of the amplifier 35 is connected to a connection node with the other end of the amplifier 35, and the positive-phase input terminal (+) of the amplifier 35 is connected with a connection node between one end of the resistor 32 and the other end 30 b of the solenoid 30. It is connected.

FIG. 6 is a circuit diagram showing the amplifier in FIG. The amplifier 40 has a resistor R11 having one end connected to the positive-phase input terminal (+), a resistor R12 having one end connected to the negative-phase input terminal (-), and one end connected to the other end of the resistor R12. And a resistor R13. The other end of the resistor R11 is connected to the emitter of the NPN transistor Tr11 and NP.
The emitter of the N-type transistor Tr12 is connected. The collector of the transistor Tr11 is connected to the collector of the PNP transistor Tr13. The emitter of the transistor Tr13 is connected to a power supply.
Base of transistor Tr11 and transistor Tr12
Are connected to the constant current source 40a.

On the other hand, the other end of the resistor R13 is connected to the emitter of the NPN transistor Tr14 and the emitter of the PNP transistor Tr15. The collector of the transistor Tr14 has a PNP transistor Tr1
6 collectors and bases are connected. The base of the transistor Tr16 is connected to the base of the transistor Tr13, and the emitter of the transistor Tr16 is connected to the power supply. The base of the transistor Tr14 and the base and collector of the transistor Tr15 are connected to the constant current source 40a.

The connection node between the collector of the transistor Tr13 and the collector of the transistor Tr11 has an NPN
The base of the type transistor Tr17 is connected. The emitter of the transistor Tr17 includes a resistor R12 and a resistor R12.
13, the collector of the transistor Tr17 is connected to the collector and base of the PNP transistor Tr18 and the base of the PNP transistor Tr19. The collectors of the transistors Tr18 and Tr19 are commonly connected to a power supply. The transistor Tr19 is a transistor Tr18
The collector of the transistor Tr19 is connected to the ground via the resistor R14. Resistor R14 and transistor Tr1
The connection node with the collector 9 is the output terminal of the amplifier 40.

The arithmetic circuit 41 includes the sample hold circuit 3
6. A pulse signal S4 for setting the sampling timing
1 during the period when the control signal S37 output from the control circuit 37 is "L".

FIG. 7 is a waveform chart showing the operation of the solenoid drive circuit of FIG. The control circuit 37 outputs a control signal S37 that repeats “H” and “L” as shown in FIG.
It is given to the gate of OS33. The NMOS 33 operates in the same manner as in the first embodiment, and turns on when the control signal S37 is “H” to connect between the battery 31 and the resistor 32. Thus, the solenoid 30 from the battery 31 via the resistor 32, current flows _{I 1} in Figure 7 (b).

When the control signal S37 is "L", the NMOS
33 turns off and cuts off the connection between the resistor 32 and the battery 31. When the NMOS 33 interrupts the connection between the resistor 32 and the battery 31, the voltage at the other end 30b of the solenoid 30 whose one end 30a is connected to the ground G is reduced by the back electromotive force, and a forward voltage is applied to the diode 34. . The diode 34 to which the forward voltage is applied becomes conductive,
A regenerative current I ₀ shown in FIG. 7B is passed from the ground G to the solenoid 30 via the resistor 32. That is, the diode 3
4. The resistor 32 and the solenoid 30 form one closed loop via the ground G. Accordingly, the solenoid 30 is driven by the current _{I 1} and the regenerative current _{I 0.}

The current I ₁ and the regenerative current I ₀ flow through the resistor 32 alternately. When the current I ₁ flows through the resistor 32, the voltage drop, both ends of the resistor 32, a potential difference is produced. Similarly, when the current I ₀ flows through the resistor 32, the voltage effect causes
A potential difference is generated between both ends of the resistor 32. That is, the amplifier 4
A difference as shown in FIG. 7C occurs between the input voltages of the positive-phase input terminal (+) and the negative-phase input terminal (−) of 0.

The current when I ₁ is flowing, as in the first embodiment the positive phase input terminal (+) and the negative phase input terminal (-) is a positive voltage, and, the positive-phase input terminal (+) Is higher than the input voltage of the negative-phase input terminal (−).
When the current I ₀ is flowing, the positive-phase input terminal (+) and the negative-phase input terminal (−) are negative voltages, and the input voltage of the positive-phase input terminal (+) is negative phase input terminal (−). Input voltage.

In the amplifier 40, the transistors Tr11 to Tr11
The Tr16 and the constant current source 40a function as a constant current source circuit, and operate so that the current flowing through the resistor R11 is equal to the current flowing through the resistor R13. For example, when the current I ₀ is flowing, the input voltage of the positive-phase input terminal (+) becomes
When the voltage becomes higher than the input voltage of the negative-phase input terminal (-), the voltage of the emitters of the transistors Tr11 and Tr12 increases, the base-emitter voltage of the transistors Tr11 and Tr12 decreases, and the current flowing through the resistor R11 decreases. The current flowing through the resistor R13 tends to increase.
At the same time, the voltage of the collector of the transistor Tr11 starts to increase. Therefore, the base-emitter voltage of the transistor Tr17 increases, and the transistor Tr17
And the current flowing through the resistor R12 increases. Resistance R1
As the current flowing through 2 increases, the voltage at the connection node between resistors R13 and R12 increases, and the current flowing through resistor R13 decreases. Thus, the operation is performed so that the currents flowing through the resistors R13 and R11 become equal.

When the current flowing through the transistor Tr17 increases, the base voltages of the transistors Tr18 and Tr19 decrease, and the collector current of the transistor Tr19 increases. Therefore, the current flowing through the resistor R14 increases, and the output voltage of the amplifier 40 increases. The output voltage of the amplifier 40 is output to the sample and hold circuit 36 as a current detection signal S40.

[0049] On the other hand, when the current I ₁ is flowing, the input voltage and the negative phase input terminal of the positive-phase input terminal (+) (-) since the input voltage is the power supply voltage near the transistor Tr
The constant current source circuit composed of 11 to Tr16 does not operate,
Signal S40 of amplifier 40 is fixed at a voltage near ground G.

When the control signal S37 output from the control circuit 37 is "L", the arithmetic circuit 41 outputs a pulse signal S40 indicating the timing at which the sample hold circuit 36 performs sampling. The sample hold circuit 36
Similarly to the first embodiment, when the pulse signal S40 is "H", the capacitor 36b is connected to the current detection signal S4.
Charge to zero voltage. The capacitor 36b charged with the voltage of the current detection signal S35 holds and outputs the charged voltage.

As described above, in the second embodiment,
It has the following advantages. (1) Since one end of the solenoid 30 is connected to the ground G as in the first embodiment, the number of lead wires connecting the solenoid 30 and the control unit 20 is reduced to one. Therefore, the amount of wire harness can be reduced, and the increase in weight when there are many solenoids 30 can be minimized.

(2) Since the signal indicating the current flowing through the solenoid 30 is output from the sample hold circuit 36, when the current flowing through the solenoid 30 changes, the change can be indicated quickly. (3) by the sample-and-hold circuit 36, since the output signal S40 of the amplifier 40 in a period in which current I ₀ flows to sample, it is not necessary to use an amplifier 40 that can cope with the input voltage close to the power supply voltage. Therefore, the amplifier 40 can be configured with a simple configuration as shown in FIG.

Note that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in FIG. 3, only one set of the switch 36a and the capacitor 36b is shown to show the outline of the sample and hold circuit 36,
A plurality of switches 36a and a plurality of capacitors 36b may be used.

[0054]

As described in detail above, according to the present invention, the solenoid, the current detecting circuit, the switching element, and the rectifying element constitute a solenoid driving device, and one end of the solenoid is connected to the ground. The amount of harness of the solenoid driving device can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a solenoid driving device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing an amplifier in FIG.

FIG. 3 is a circuit diagram showing a main part of a sample and hold circuit in FIG. 1;

FIG. 4 is a waveform chart showing an operation of the solenoid driving device of FIG. 1;

FIG. 5 is a configuration diagram of a solenoid drive device according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing the amplifier in FIG. 5;

FIG. 7 is a waveform chart showing the operation of FIG. 5;

FIG. 8 is a configuration diagram showing a conventional solenoid drive device.

FIG. 9 is a waveform chart showing the operation of FIG.

[Explanation of symbols]

 Reference Signs List 30 solenoid 31 battery 32 resistor constituting current detection circuit 33 NMOS as switching element 34 diode as rectifying element 35, 40 amplifier constituting current detection circuit 36 sample and hold circuit 37 control circuit 38, 41 arithmetic circuit

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[Procedure amendment]

[Submission date] May 31, 2002 (2002.5.3)
1)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction contents]

The connection point between the source of the NMOS 33 and the resistor 32 is connected to the cathode of the diode 34 and to the positive-phase input terminal (+) of the amplifier 35. The anode of the diode 34 is connected to the ground G. The negative-phase input terminal (−) of the amplifier 35 is connected to a resistor 3
2 and is connected to the other end 30 b of the solenoid 30.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

Claims (4)

[Claims] A solenoid having one end connected to ground, a load element having one end connected to the other end of the solenoid, and detecting a current flowing through the load element to generate a current detection signal corresponding to the current. A current detection circuit to be generated, connected between the other end of the load element and a power supply, turns on and off between the load element and the power supply, and flows the current from the power supply to the solenoid when turned on. A switching element that drives the solenoid, and is connected between the ground and the other end of the load element;
And a rectifying element that drives the solenoid by flowing the current generated by the back electromotive force generated in the solenoid when the switching element is turned off from the ground to the solenoid. 2. A sample-and-hold circuit which samples the current detection signal at a predetermined timing and holds the signal as a signal representing a current flowing through the solenoid during a period when the switching element is on and a period when the switching device is off. The solenoid drive according to claim 1, further comprising: 3. The solenoid driving device according to claim 2, wherein the sample and hold circuit samples the current detection signal when the switching element is turned on. 4. The solenoid driving device according to claim 2, wherein the sample and hold circuit samples the current detection signal when the switching element is off.