JP2000184582A - Solenoid driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a solenoid driver having a function to detect disconnection of a reflow circuit for reflowing a current associated with the fly-back voltage. SOLUTION: A solenoid driver comprises a solenoid 10 and a reflow circuit 14 formed of a diode 12. Depending on the ON/OFF condition of FET 22 connected to the solenoid 10, power feeding to the solenoid 10 can be controlled. If a disconnection occurs in the reflow circuit 14, a high fly-back voltage is generated and it charges a capacitor 38 via a zener diode 32. The charging voltage of capacitor 38 turns on the transistor to set the potential of the output terminal 46 to a low level. CPU 26 detects disconnection of the reflow circuit 14, based on the potential level of the output terminal 46.

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, and more particularly, to a solenoid driving device capable of detecting disconnection of a circulation circuit for circulating a current caused by a flyback voltage of a solenoid.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Application Publication No.
As disclosed in No. 5, an electromagnetic valve driving device that controls energization of a solenoid included in an electromagnetic valve is known. This device includes a booster circuit for generating a high voltage, a capacitor charged by the booster circuit, and switching elements provided corresponding to each solenoid. When the switching element is turned on, the capacitor is discharged via the solenoid corresponding to the switching element, so that an exciting current is supplied to the solenoid.

When an exciting current is supplied to the solenoid by discharging the capacitor, the charged voltage of the capacitor decreases. On the other hand, when a disconnection occurs in the solenoid or a current supply path to the solenoid (hereinafter, simply referred to as a current supply path), even if the switching element is turned on, the capacitor is not discharged, and the charged voltage does not change. Therefore, in the above-described conventional device, the disconnection of the current supply path is detected by comparing the charged voltage of the capacitor at the time when the switching element is turned on and turned off again with a predetermined threshold value.

[0004]

Incidentally, the above-mentioned conventional device includes a diode arranged so as to form a free-circulating circuit together with the solenoid. When the energization of the solenoid is cut off, the flyback voltage is absorbed by the current caused by the back electromotive force circulating in the circulation circuit. Therefore, even when the power supply to the solenoid is cut off, the current flowing through the solenoid does not immediately disappear, and the power supply state to the solenoid is maintained. Therefore, according to the circulation circuit, it is possible to control the average current by duty driving the solenoid. In order to maintain the function of the circulation circuit, it is necessary to detect disconnection of the circulation circuit. However, in the above-mentioned conventional device, although the disconnection of the current supply path to the solenoid can be detected,
No consideration is given to detecting disconnection of the circulation circuit.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is possible to detect a disconnection of a circulation circuit that enables current control to a solenoid by circulating a current accompanying a flyback voltage. It is an object to provide a solenoid driving device.

[0006]

The above object is achieved by the present invention.
As described in the above, energization control means for controlling energization to the solenoid, a circulation circuit including the solenoid, flyback voltage detection means for detecting a flyback voltage generated when the energization to the solenoid is cut off, This is achieved by a solenoid driving device including: a disconnection detecting unit that detects disconnection of the circulation circuit based on a flyback voltage.

In the present invention, when the circulation circuit including the solenoid is disconnected, a high flyback voltage is generated when the power supply to the solenoid is cut off. On the other hand, when the circulation circuit is not disconnected, the current flows through the circulation circuit when the power supply to the solenoid is cut off, so that the flyback voltage is absorbed. Therefore, the disconnection detecting means can detect the disconnection of the circulation circuit based on the flyback voltage. The disconnection of the circulation circuit means a disconnection of a portion of the circulation circuit that is not an energization path to the solenoid.

[0008]

FIG. 1 is a circuit diagram of a solenoid driving device according to a first embodiment of the present invention. The solenoid driving device according to the present embodiment is configured as a device that controls energization of the solenoid 10. As shown in FIG. 1, the solenoid driving device includes a circulation circuit 14 including a solenoid 10 and a diode 12. The diode 12 is provided in parallel with the solenoid 10 so that the direction from the first terminal 10a to the second terminal 10b of the solenoid 10 is forward.

A second terminal 10b of the solenoid 10 is connected to a power supply voltage line 16. In the second terminal 10b,
The power supply voltage VB is supplied from the power supply voltage line 16. A solenoid energization output circuit 18 and a flyback voltage detection signal generation circuit 20 are connected to the first terminal 10a of the solenoid 10. Solenoid energization output circuit 18
Includes an FET 22. The drain terminal 22a of the FET 22 is connected to the first terminal 10a of the solenoid 10. The source terminal 22b of the FET 22 is connected to the ground line. Further, the gate terminal 22c of the FET 22 is connected to the CPU 26. FET22
Is turned on when a high-level signal is supplied from the CPU 26 to the gate terminal 22c.

The flyback voltage detection signal generation circuit 20 includes a transistor 28. The first of the solenoid 10
Between the terminal 10a and the base terminal 28a of the transistor 28, a resistor 30, a Zener diode 32, a diode 34, and a resistor 3 are arranged in this order from the first terminal 10a side.
6 are connected in series with each other. The Zener diode 32 is connected such that the direction from the transistor 28 toward the solenoid 10 is forward. In addition,
The Zener diode 32 has a Zener voltage Vz
The power supply voltage is higher than the power supply voltage VB, and is lower than the maximum value of the flyback voltage generated when the circulation circuit 14 is disconnected as described later when the power supply to the solenoid 10 is cut off. The diode 34 is connected so that the direction from the solenoid 10 to the transistor 28 is forward. A capacitor 38 is connected between the connection between the diode 34 and the resistor 36 and the ground line. Further, a resistor 40 is connected between a connection between the resistor 36 and the base terminal 28a of the transistor 28 and an earth line.

The emitter terminal 28b of the transistor 28 is connected to a ground line. Transistor 2
8 is connected to the power supply voltage line 16 via the resistor 42 and is connected to the output terminal 46 of the flyback voltage detection signal generation circuit 20 via the resistor 44. A capacitor 48 is connected between the output terminal 46 and the ground line. The output terminal 46 is connected to the CPU 26.

As described above, when a high level voltage is supplied from the CPU 26 to the gate terminal 22c of the FET 22, F
ET22 is turned on. In this case, an exciting current is supplied to the solenoid 10 by conducting a circuit from the power supply voltage line 16 to the earth line via the solenoid 10 and the FET 22. Further, when the exciting current is supplied to the solenoid 10, the gate terminal 22 of the FET 22 is turned off.
When the voltage of c becomes a low level, the FET 22 is turned off, so that the power supply to the solenoid 10 is cut off. In this case, the back electromotive force of the solenoid 10 causes the circulation circuit 1
A current flows from the first terminal 10a to the first terminal 10a via the diode 12, the second terminal 10b, and the solenoid 10 to return to the first terminal 10a. For this reason, when energization of the solenoid 10 is interrupted, generation of a high flyback voltage is prevented, and energization of the solenoid 10 is maintained even after energization is interrupted, thereby enabling current control by duty control. .

As described above, the circulation circuit 14 absorbs the flyback voltage by circulating the current caused by the back electromotive force when the power supply to the solenoid 10 is cut off, and makes it possible to control the amount of current supply by duty control. It has the function to do. The solenoid drive device of the present embodiment is characterized in that the disconnection of the circulation circuit 14 having such a function can be detected. The disconnection of the circulation circuit 14 means that the second terminal is connected to the first terminal 10 a of the solenoid 10 via the diode 12.
This means a disconnection of a path leading to the terminal 10b, that is, a path that is not an energizing path to the solenoid 10. Hereinafter, the operation of the solenoid driving device according to the above-described feature of the present embodiment will be described.

In the solenoid driving device of the present embodiment,
When the FET 22 is maintained in the off state, that is, when the energization of the solenoid 10 is not performed,
The first terminal 10a of the solenoid 10 has a solenoid 10
The power supply voltage VB is applied via As described above, the Zener voltage Vz of the Zener diode 32 is equal to the power supply voltage VB.
The pressure is higher than that of. Therefore, even if the power supply voltage VB is applied to the first terminal 10a, the Zener diode 32
Does not occur, and the capacitor 38 is not charged. In this case, the base terminal 2 of the transistor 28
The potential of 8a becomes low level, and the transistor 28 is maintained in the off state. When the transistor 28 is kept off, the output terminal 46 is connected to the resistors 42 and 44.
The power supply voltage VB is supplied via the
The potential of 6 becomes high level.

When the FET 22 is maintained in the ON state, that is, when power is supplied to the solenoid 10, the potential of the first terminal 10a becomes low due to the voltage drop in the solenoid 10. When the potential of the first terminal 10a is at a low level, the above-described F
As in the case where the ET 22 is maintained in the off state, the charging of the capacitor 38 is not performed.
Is at a high level.

As described above, when the FET 22 is maintained in the off state or the on state, that is, the solenoid 1
When the energized state or the non-energized state of 0 is maintained,
Regardless of whether the circulation circuit 14 is disconnected or not, the output terminal 46
Is maintained at a high level. If no disconnection occurs in the circulation circuit 14, as described above, when the FET 22 is switched from the on state to the off state, that is, when the energization to the solenoid 10 is cut off,
Circulates the current to prevent the generation of a high flyback voltage. Therefore, the potential of the first terminal 10a of the solenoid 10 is maintained lower than the Zener voltage Vz of the Zener diode 32, and the potential of the output terminal 46 becomes high. That is, when no disconnection occurs in the circulation circuit 14, the potential of the output terminal 46 is always maintained at the high level regardless of the energization state of the solenoid 10.

On the other hand, if a disconnection occurs in the circulation circuit 14, when the power supply to the solenoid 10 is cut off, the solenoid 1
A high flyback voltage is generated with the back electromotive force of zero. FIG. 2 shows the first terminal 1 when the energization of the solenoid 10 is interrupted in a situation where the circulation circuit 14 is disconnected.
The time change of the potential 0a is shown. As shown in FIG.
Up to 1, since the solenoid 10 is energized, the potential of the first terminal 10a is maintained at a low level. When energization of the solenoid 10 is interrupted at time t1, a high flyback voltage is generated at the first terminal 10a. As described above, the Zener voltage Vz of the Zener diode 32 is lower than the maximum value of the high flyback voltage generated when the circulation circuit 14 is disconnected. Therefore, the potential of the first terminal 10a sharply rises beyond the Zener voltage Vz.

The potential of the first terminal 10a is equal to the Zener voltage Vz.
Is exceeded, a Zener effect occurs in the Zener diode 32, and the Zener diode 32 has a reverse direction (ie,
A current flows in a direction from the solenoid 10 toward the transistor 28). The capacitor 38 is charged by this current, and the potential of the first terminal 10a gradually decreases. Then, the potential of the first terminal 10a becomes the Zener voltage V
Below z, the current flow is stopped. Accordingly, the capacitor 38 is charged with an amount of electric charge corresponding to a region indicated by hatching in FIG. When the capacitor 38 is charged, the charge voltage is applied to the base terminal 28a of the transistor 28, so that the base-emitter voltage of the transistor 28 increases. As a result, the transistor 28 is turned on, and the capacitor 4
8 is discharged and the resistor 4
Due to the voltage drop at 2, the potential of the output terminal 46 becomes low level. That is, when the circulation circuit 14 is disconnected, the potential of the output terminal 46 becomes low level when the power supply to the solenoid 10 is cut off. As described above, when no disconnection occurs in the circulation circuit 14, the potential of the output terminal 46 is always maintained at the high level. On the other hand, if the circulation circuit 14 is disconnected, the solenoid 10
When the power supply to the terminal is cut off, the potential of the output terminal 46 changes to a low level. Therefore, the disconnection of the circulation circuit 14 can be detected by determining the potential level of the output terminal 46 by the CPU 26.

By the way, as a method of detecting a disconnection of the circulation circuit, a configuration in which a resistor for current detection is provided in the circulation circuit (hereinafter, referred to as a comparison configuration) can be considered. FIG. 3 shows a circuit diagram of a comparison configuration. In FIG. 3, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. As shown in FIG. 3, in the contrast configuration, the first terminal 10a of the solenoid 10 and the diode 12
Is connected to the resistor 100. Solenoid 1
0, the diode 12, and the resistor 100
2. An A / D converter 104 is connected to both ends of the resistor 100. The A / D converter 104 converts the voltage across the resistor 100 into a digital signal,
Supply to U26.

In the above configuration, the circulation circuit 102
If the disconnection does not occur, when the power to the solenoid 10 is cut off, the current accompanying the back electromotive force
2 circulates through the resistor 2, and this current generates a voltage across the resistor 100. On the other hand, if a disconnection occurs in the circulation circuit 102, no current can flow through the circulation circuit 102, so that no voltage is generated across the resistor 100. Therefore, according to the comparison configuration, the CPU 26 monitors the voltage across the resistor 100 via the A / D converter 104, and
2 can be detected.

However, in the above-described contrast configuration, the resistor 10
In order to minimize the influence of 0 on the operation of the solenoid driving device, the resistance value of the resistor 100 must be set small. In this case, the voltage generated at both ends of the resistor 100 is also small. Expensive voltage detecting means such as the A / D converter 104 is required to detect such a minute voltage, and the cost of the apparatus increases. In addition, the circulation circuit 1
02, the resistor 100 is provided, so that the circulation circuit 1
02 and a circuit for detecting disconnection of the circulation circuit 102 (that is, the resistor 100 and the A / D converter 104) cannot be separated, and the degree of freedom in designing the entire circuit is reduced.

On the other hand, according to the solenoid driving device of the present embodiment, it is not necessary to add any components to the circulation circuit 14, so that the disconnection of the circulation circuit 14 can be performed without affecting the operation of the driving circuit. Can be detected. Also,
Since the disconnection can be detected based on the high / low potential level of the output terminal 46, it is not necessary to provide a voltage detecting means. It can be composed of only inexpensive components. Therefore, according to the solenoid driving device of the present embodiment, it is possible to significantly reduce the cost as compared with the above-described configuration. Further, the circulation circuit 14 and a circuit for detecting disconnection of the circulation circuit 14 (that is, the flyback voltage detection signal generation circuit 2
0) are completely separated from each other, so that a large design flexibility of the entire circuit can be secured.

Next, a second embodiment of the present invention will be described. FIG. 4 is a circuit diagram of the solenoid driving device of the present embodiment. In FIG. 4, components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. A plurality of solenoid driving devices of this embodiment (FIG. 3)
Are configured as devices for controlling the energization of the two solenoids 10).

As shown in FIG. 4, the solenoid driving device comprises:
A circulation circuit 14 including a diode 12 and a solenoid energization output circuit 18 are provided for each solenoid 10. The flyback voltage detection signal generation circuit 20
Has a resistor 30 and a Zener diode 32 corresponding to each solenoid 10. Components of the flyback voltage detection signal generation circuit 20 except for the resistor 30 and the Zener diode 32 are provided in common for all the solenoids 10.

In the solenoid driving device of the present embodiment, similarly to the solenoid driving device of the first embodiment, when any one of the FETs 22 is turned on, the exciting current is supplied to the solenoid 10 corresponding to the FET 22. Supplied. If a disconnection occurs in any one of the circulation circuits 14, when the power supply to the solenoid 10 corresponding to the circulation circuit 14 is cut off, the potential of the first terminal 10a rises beyond the Zener voltage Vz. In this case, when the capacitor 38 is charged, the transistor 28 is turned on, and the potential of the output terminal 46 becomes low. Therefore,
Also in the solenoid driving device of the present embodiment, the output terminal 4
When the potential of the circuit 6 becomes low level, it is possible to detect that any of the circulation circuits 14 is disconnected.

FIG. 5 is a circuit diagram in the case where the comparison structure shown in FIG. 3 is applied as a device for driving a plurality of solenoids 10. In FIG. 5, components having the same functions as those in FIG. 3 are denoted by the same reference numerals. As shown in FIG. 5, in the contrast configuration, each solenoid 10
It is necessary to provide the A / D converters 104 corresponding to the above, and since a digital signal is input from each A / D converter 104 to the CPU 26, the number of input ports of the CPU 26 also increases. As described above, according to the comparison configuration, when applied as a device that drives a plurality of solenoids 10,
This will increase the cost and complexity of the device.

On the other hand, in the solenoid driving apparatus of the present embodiment, as described above, the disconnection of each circulation circuit 14 is detected only by providing the resistor 30 and the Zener diode 32 corresponding to each solenoid 10. be able to. That is, components other than the resistor 30 and the Zener diode 32 are shared by the plurality of solenoids 10, so that the device configuration can be simplified.

FIG. 3 shows two solenoids 1
Although the case where two reflux circuits 14 are provided corresponding to 0 is shown, the present invention is not limited to this, and when three or more reflux circuits 14 are provided, the resistor 30 and the Zener diode By providing the circuit 32, it is possible to detect a disconnection of each circulation circuit 14 based on the potential level of the output terminal 46 in the same manner as above.

In the first and second embodiments, the charge associated with the flyback voltage is charged in the capacitor 38 via the Zener diode 32, and the transistor 28 is turned on by the charged voltage, whereby the circulation circuit 14 The disconnection was detected. However, the present invention is not limited to this.
The break of the circulation circuit 14 may be detected by monitoring the potential of the first terminal 10a and directly detecting the flyback voltage.

In the first and second embodiments, the solenoid energization output circuit 18 is described in the energization control means described in the claims, and the flyback voltage detection signal generation circuit 20 is described in the claims. The claims correspond to flyback voltage detection means, respectively, and are described in claims by the CPU 26 detecting a disconnection of the circulation circuit 14 based on the potential level of the output terminal 46 of the flyback voltage detection signal generation circuit 20. Disconnection detecting means is realized.

[0031]

As described above, according to the solenoid driving device of the present invention, it is possible to detect a disconnection of the circulation circuit which enables the current control of the solenoid by circulating the current accompanying the flyback voltage.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a temporal change in the potential of a first terminal of the solenoid before and after the energization of the solenoid is interrupted when a disconnection occurs in the circulation circuit.

FIG. 3 is a circuit diagram of a comparative configuration.

FIG. 4 is a circuit diagram of a solenoid driving device according to a second embodiment of the present invention.

FIG. 5 is a circuit diagram in the case where the comparison configuration shown in FIG. 3 is applied as a device that drives a plurality of solenoids.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Solenoid 12 Diode 14 Recirculation circuit 18 Solenoid energization output circuit 20 Flyback voltage detection signal generation circuit 26 CPU

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsuneharu Yotsuya 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor Koichi Kondo 1 Toyota Town, Toyota City, Aichi Prefecture Toyota Motor Corporation (72) Inventor St. Miyake 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Hiromi Maehata 1-1-1, Showa-cho, Kariya-shi, Aichi Prefecture Inside Denso Corporation (72) Inventor Suzukawa Tetsuo 1-1-1 Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation (72) Inventor Shuichi Yonemura 1-1-1, Showa-cho, Kariya city, Aichi Prefecture F-term in DENSO Corporation 5G004 AA04 AB02 BA05 CA02 DB01 DC04 EA01 GA02 5G053 AA07 AA09 BA04 DA01 EB02 EC03 FA07

Claims (1)

[Claims] A power supply control means for controlling power supply to a solenoid; a circulation circuit including the solenoid; a flyback voltage detection means for detecting a flyback voltage generated when the power supply to the solenoid is interrupted; A solenoid drive device comprising: a disconnection detecting unit configured to detect a disconnection of the circulation circuit based on a flyback voltage.