JPH05146058A - Current limiter for solenoid drive circuit - Google Patents

Abstract

PURPOSE:To realize positive current limitation even for a faint short circuit by detecting a current from a DC resistor connected with a power supply for a solenoid, integrating thus detected current value, adding a predetermined current to a feedback control circuit when a predetermined integrated value is reached, and then retaining the predetermined current for a predetermined time. CONSTITUTION:Upon turn ON of transistors(TR) Q1, Q2, a capacitor C3 is charged with the voltage of resistors R1, R2 through a risistor R4. Upon increase of the charging voltage of the capacitor C3, a TR Q4 is turned ON and collector current thereof is fed through a resistor R9 to an integrator/amplifier AM and then added to the feedback circuit in a comparator IC 1. Consequently, the comparator IC 1 has a feedback amount similar to that when an overcurrent flows through a solenoid S and thereby the TR Q1, TR Q2 are turned OFF by means of the comparator IC 1 and a modulation circuit IC 2 thus bringing the solenoid S into interrupted state. According to the invention, current can positively be limited even for a faint variation of current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current limiting device for controlling a current when an overcurrent such as a short circuit is applied to the solenoid driving circuit, and more particularly to a solenoid driving circuit for controlling the duty ratio of the solenoid. The present invention relates to a current limiting device.

[0002]

2. Description of the Related Art A current limiting device for a solenoid drive circuit of this type is constructed as shown in FIGS.

FIG. 2 is a circuit diagram of a current limiting device for a conventional solenoid drive circuit, and FIG. 3 is a timing chart when the duty ratio of the solenoid is controlled.

In FIG. 2, when a PWM signal for controlling the duty ratio of the solenoid S is input to the base of the transistor Q11, the transistor Q11 is turned on according to "H (high level)" or "L (low level)" of the PWM signal.・
The transistor Q12 is turned off and the transistor Q12 is turned on / off via the base resistor R61. For example, when the transistor Q12 is on, the solenoid S is energized via the resistor R62. That is, the energization of the solenoid S is controlled by turning on / off the transistor Q12.

At this time, the voltage applied to the solenoid S as shown in FIG. 3 is P as shown in FIG.
The waveforms correspond to “H” and “L” of the WM signal, and the current supplied to the solenoid S is the average current flowing in the reactance component of the solenoid S as shown in FIG. 3B. Become.

On the other hand, when an overcurrent is applied to the resistor R62 due to a short circuit between the solenoids S, a short circuit between grounds, etc., the resistance R62
The voltage drop of the transistor becomes large, turns on the transistor Q13, and the collector current of the transistor Q13 increases,
The voltage between the emitter and base of the transistor Q12 drops,
By reducing the base current of the transistor Q12 and raising the resistor R63, the collector current of the transistor Q12 is reduced and the current of the solenoid S is suppressed.

[0007]

However, in the above technique, the transistor Q12 side of the solenoid S falls to the ground,
When the scale of the interlayer short circuit is large, it is easy to detect it. However, when the scale of the interlayer short circuit of the solenoid S is small, or when the solenoid S is short-circuited to the ground side near the ground side, it is normal. The difference between the normal operating current and the normal operating current becomes small, and it becomes difficult to distinguish between the threshold value in the case of a short circuit and the normal operating current, and they cannot be detected accurately. Further, the transistor Q12 is controlled in an analog manner, and its heat generation becomes a problem.

Therefore, the present invention surely protects the switching element from a large current flowing in an instant, and when the scale of the interlayer short circuit of the solenoid is small, or when the solenoid is short-circuited to the earth side near the earth side. It is an object of the present invention to provide a current limiting device for a solenoid drive circuit that can surely limit the current even with a slight change in the current.

[0009]

SUMMARY OF THE INVENTION A current limiting device for a solenoid drive circuit according to the present invention energizes a solenoid with a pulse width-modulated pulse signal corresponding to an average current designated by the solenoid drive circuit. Feedback control the pulse signal. At this time, the overcurrent detection circuit detects the overcurrent conduction from the series resistance connected to the power supply supplied to the solenoid, adds a predetermined current to the feedback control circuit, and holds it for a predetermined time. That detects the current from the series resistance connected to the power supply that supplies it, integrates it, and when it reaches a predetermined integrated value, adds a predetermined current to the feedback control circuit and holds it for a predetermined time Is.

[0010]

In the present invention, the pulse width-modulated pulse signal corresponding to the specified average current is supplied to the solenoid, and the feedback control is performed so that the supplied pulse signal matches the specified average current. At this time,
The current value of the pulse signal supplied from the power supply is detected as an overcurrent conduction from the series resistance connected to the power supply, a predetermined current is added to the feedback control circuit to increase the feedback amount, and the energization current of the solenoid is changed for a predetermined time. Just suppress and repeat this process. In addition, the current is detected from the series resistance connected to the power supply that supplies the solenoid, the current is integrated, and when the predetermined integrated value is reached, the predetermined current is added to the feedback control circuit to increase the minute current. On the other hand, by holding it for a predetermined time, the abnormality is detected by the increase of the minute current supplied to the solenoid.

[0011]

1 is an overall circuit diagram of a current limiting device for a solenoid drive circuit according to an embodiment of the present invention.

In FIG. 1, terminals SOL + and SOL- of the solenoid S are connected to one power supply terminal + B for driving the solenoid S via resistors R1 and R2, and
The other power supply terminal, which is the ground in this embodiment, is connected through a resistor R3. These resistors R1, R2 and R3 all have low resistance values. The solenoid S, the resistors R1, R2 and R3, and the transistor Q2 as a switching element constitute a solenoid output circuit 10 for supplying electric power to the solenoid S. Although a plurality of low resistances are connected in series in the present embodiment, a single resistance or a plurality of resistances may be used when implementing the present invention.

A pulse width-modulated pulse signal for driving the solenoid S is applied as follows.

The command of the average current supplied to the solenoid S is applied to the terminal VIN as a voltage corresponding to the average command current, and the signal is input to the comparison circuit IC1 via the resistors R31 and R32. A far-back amount, which is a negative feedback amount of the energizing current of the solenoid S, is input to the comparison circuit IC1, and the average current energizing the solenoid S is controlled to be a command value. Then, the output of the comparison circuit IC1 is input to the modulation circuit IC2 including a comparator. A repeating signal of a triangular wave having a stable waveform is input from the triangular wave generating circuit PG to the modulating circuit IC2.
The triangular wave generation circuit PG of this embodiment is an amplifier circuit IC.
4 and a capacitor C21 and resistors R21, R22, R23 and resistors R24, R25, which are non-stable multivibrators, but the present invention is not limited thereto.

Therefore, in the modulation circuit IC2, a rectangular wave output having a pulse width corresponding to the output time of the comparison circuit IC1 below the output of the triangular wave generation circuit PG is the modulation circuit IC2.
Is output. The output of the modulation circuit IC2 is input to the base of the transistor Q1 via the resistor R33. When the rectangular wave output of the modulation circuit IC2 is “H”, the transistor Q
Since 1 is turned off and no base current flows through the base of the transistor Q2, the transistor Q2 is also turned off and the solenoid S is not energized. When the rectangular wave output of the modulation circuit IC2 is "L", the base current flowing through the resistor R33 turns on the transistor Q1, and the turning on of the transistor Q1 causes the base resistance R5 of the transistor Q2.
Also, the base current flows, the transistor Q2 is also turned on, and the solenoid S is energized.

The current flowing through the solenoid S at this time is detected as a voltage drop across the resistor R3, the ripple is smoothed by the capacitor C11, and the amplifier circuit IC3 that operates as an integral amplifier circuit AM through the resistors R11 and R12. Input to one terminal, and the amplifier circuit IC3 with resistors R13, R14 and R15
Has determined the amplification factor of. The output of the integration amplification circuit AM is negatively fed back as a feedback amount input signal of the comparison circuit IC1. The integration amplifier circuit AM includes an amplifier circuit IC3, a capacitor C12 for setting an integration constant, and a resistor R.
15 and input resistors R12, R13 and R14.

The diode D2 is for a flywheel, and the Zener diode ZD2 is for preventing application of an abnormal voltage. Further, the resistor R34 applies a bias so that the feedback amount of a predetermined value is always maintained even when the input of the integrating amplifier circuit AM is not energized to the solenoid S. The capacitor C4 of the present embodiment slows the response of the output of the amplifier circuit IC3 and is inserted depending on the application of the solenoid S, and is necessarily required when the present invention is carried out. is not.
Similarly, when implementing the present invention, an amplifier circuit may be used instead of the integral amplifier circuit AM.

As described above, the comparison circuit IC1 and the modulation circuit IC for obtaining the PWM signal corresponding to the designated average current.
2. Transistor Q1 and transistor Q2 consisting of switching elements controlled by PWM signal, solenoid S
Integral amplifier circuit AM for determining feedback amount by resistor R3 inserted in series to solenoid drive circuit 2
Configures 0. Further, a resistor R3 inserted in series with the solenoid S, an integral amplifier circuit AM, and a comparison circuit IC1.
Feedback amount input terminal of the feedback circuit 2
Configure 0A.

Further, the voltage of the resistor R1 having a low resistance connected in series to the solenoid S is connected between the emitter and the base of the transistor Q3 via the base resistor R6. The collector output of the transistor Q3 is applied to the parallel circuit of the resistor R7 and the capacitor C1.
The capacitor C2 is charged via. At the same time, the collector output of the transistor Q3 is added to the feedback amount input signal of negative feedback of the comparison circuit IC1 via the resistor R8 and the backflow prevention diode D1.

That is, these circuits detect an overcurrent from the series resistor R1 connected to the power source supplied to the solenoid S by the solenoid drive circuit with the transistor Q3, and become a part of the feedback control circuit of the comparison circuit IC1. An instantaneous overcurrent detection circuit 30 is configured to add a predetermined current to the feedback amount input terminal and hold it for a predetermined time.

The voltages of the low resistance resistors R1 and R2 connected in series to the solenoid S are applied between the emitter and the base of the transistor Q4 via the base resistor R4. A capacitor C3 is connected between the emitter and base of the transistor Q4. That is, the voltages of the resistors R1 and R2 are applied to the base resistor R4 and the capacitor C3, and the charging voltage of the capacitor C3 is input to the base of the transistor Q4. The output of the transistor Q4 is connected to the connection point between the resistors R12 and R11 of the integrating amplifier circuit AM via the resistor R9.

These circuits detect the voltage from the series resistors R1 and R2 connected to the power source for supplying the solenoid S by the solenoid drive circuit, integrate the voltage, and when the predetermined integrated value is reached, the feedback control is performed. The integrated current detection circuit 40 is configured to add a predetermined current to the circuit and hold it for a predetermined time.

The current limiting device of the solenoid drive circuit 20 of the present embodiment constructed as described above operates as follows.

First, a voltage corresponding to the average command current supplied to the solenoid S is applied to a terminal VIN from an external sensor (not shown) or the like, and the result obtained by integrating the difference with the feedback amount input signal being negatively fed back is compared. It becomes the output of the circuit IC1. That is, when the feedback amount is smaller than the average command current, this output voltage increases, and conversely, when the feedback amount is large, this output decreases. This is input to the modulation circuit IC2, compared with the output of the triangular wave generation circuit PG, and when the output of the comparison circuit IC1 is large,
When the "L" time is long and the output of the comparison circuit IC1 is small, the "L" side which shortens the "L" time has information P.
WM signal.

When the output of the modulation circuit IC2 is "L", the transistors Q1 and Q2 are turned on and the solenoid S is energized. Further, when the output of the modulation circuit IC2 is "H", the transistors Q1 and Q2 are turned off and the solenoid S is cut off. However, since the "H" and "L" repetition frequencies of the modulation circuit IC2 are high, the inductance of the solenoid S causes a phase shift of the current, and the current flows through the solenoid S without interrupting the energized state. The average current at this time becomes the average command current applied to the terminal VIN. The current of the solenoid S at this time is detected as a voltage by the resistor R3, and becomes an input signal of the comparison circuit IC1 as a feedback amount via the integral amplification circuit AM.

In this way, the solenoid drive circuit 20 of this embodiment controls the normal solenoid S according to the predetermined average current by the PWM signal.

Here, it is assumed that the terminal SOL + side of the solenoid S is short-circuited to the ground.

At this time, the impedance of the solenoid S decreases, and the voltage drop across the resistors R1 and R2 becomes large. The voltage of the resistor R1 is applied between the emitter and the base of the transistor Q3 via the base resistor R6, the base current of the transistor Q3 flows, and the transistor Q3
The collector current of is supplied to the parallel circuit of the resistor R7 and the capacitor C1 and, at the same time, is added to the feedback circuit 20A of the comparison circuit IC1 via the resistor R8 and the backflow prevention diode D1, and the feedback amount is increased. The comparison circuit IC1 has the same feedback amount as when an excessive current flows through the solenoid S, and the comparison circuit IC1 and the modulation circuit IC2 turn off the transistors Q1 and Q2. As a result, the energization of the solenoid S is instantly cut off. Further, the capacitor C1 is instantly charged by the collector current of the transistor Q3, and the charge of the capacitor C1 is charged to the capacitor C2 via the resistor R8. Therefore, the charge of the capacitor C2 determines the time constant of the resistors R8 and C2. The predetermined voltage state is maintained for a limited time.

Therefore, when an overcurrent, such as when the terminal SOL + side of the solenoid S is short-circuited to ground, flows through the resistor R1, the current of the solenoid S is instantaneously cut off, the state is continued for a predetermined time, and the resistor R8 When a time limit determined by the time constant of the capacitor C2 and the time constant of the capacitor C2 elapses, "L" is output as the output of the modulation circuit IC2 that turns on the transistors Q1 and Q2 to gradually energize the solenoid S. However, the solenoid SOL terminal SOL +
Since the side is short-circuited to the ground and the impedance is lowered, the transistors Q1 and Q2 are momentarily turned on and, at the same time, repeatedly cut off. Therefore, when the terminal SOL + side of the solenoid S is temporarily short-circuited to the ground side, it is possible to recover during this time. During this period, the current passing through the transistor Q2 as a switching element does not destroy the transistor Q2.

Next, it is assumed that when the terminal SOL- side of the solenoid S is short-circuited to the ground side or an interlayer short circuit causes an increase in current to the extent that the transistor Q3 is not turned on.

The voltages of the resistors R1 and R2, which are low resistance and are connected in series to the solenoid S, are the same as those of the transistor Q1.
And when the transistor Q2 is turned on, a voltage drop occurs across the transistor Q2. The voltage of the resistors R1 and R2 is the same as that of the resistor R4.
The capacitor C3 is charged via. When the charging voltage of the capacitor C3 rises, the base current of the transistor Q4 flows, the collector current of the transistor Q4 becomes the input of the integrating amplifier circuit AM through the resistor R9, and the feedback circuit of the comparing circuit IC1 passes through the integrating amplifier circuit AM. By adding to the circuit and increasing the feedback amount, the comparison circuit IC1 has the same feedback amount as when an excessive current is flowing to the solenoid S, and the comparison circuit IC1
The modulation circuit IC2 turns off the transistors Q1 and Q2. As a result, the solenoid S is turned off. Resistor R4 and capacitor C3 at this time
The time constant of is the duty ratio for driving the normal solenoid S, and is set so that the charging voltage of the capacitor C3 does not rise with the current that is normally supplied.

Therefore, the operation of the transistor Q4 is
Since it is determined by the integrated voltage of the capacitor C3, when the terminal SOL- side of the solenoid S is short-circuited to the ground side or an interlayer short-circuit occurs, the solenoid S is continuously energized and an abnormality judgment is made based on the integrated value. ing. When the transistor Q1 and the transistor Q2 are turned off by the operation of the transistor Q4, the charging voltage of the capacitor C3 is lowered by discharging, and the solenoid S is energized again. At this time, since the operation of the transistor Q4 is determined by the integrated voltage of the capacitor C3, energization and interruption are repeated at the timing according to the abnormal state.

As described above, the current limiting device of the solenoid drive circuit 20 of this embodiment supplies electric power to the solenoid S and the solenoid S including the resistors R1, R2 and R3 of the series resistance thereof and the transistor Q2 including the switching element. Solenoid output circuit 10, comparison circuit IC1 and modulation circuit I for obtaining a PWM signal corresponding to a specified average current
C2, a transistor Q2 as a switching element controlled by the PWM signal of its output, and a solenoid drive circuit 20 comprising an integral amplifier circuit AM for determining the feedback amount by a resistor R3 inserted in series with the solenoid S.
And the solenoid S by the solenoid drive circuit 20
An overcurrent is detected by a transistor Q3 from a series resistor R1 connected to a power supply supplied to a resistor R3 inserted in series with a solenoid S of the comparison circuit IC1 and an integral amplifier circuit A.
An instantaneous overcurrent detection circuit 30 that adds a predetermined current to an input terminal that is a part of a feedback control circuit 20A including M and holds the current for a predetermined time, and a power supply that supplies a solenoid S by a solenoid drive circuit 20. A voltage is detected from the connected series resistors R1 and R2, the voltage is integrated, and when a predetermined integration value is reached, a predetermined current is added to the feedback control circuit 20A and the integration current is held for a predetermined time. It is composed of a detection circuit 40.

As described above, the current limiting device of the solenoid drive circuit 20 of the present embodiment supplies electric power to the solenoid S and the solenoid S including the resistors R1, R2 and R3 of series resistances thereof and the transistor Q2 including a switching element. Solenoid output circuit 10, comparison circuit IC1 and modulation circuit I for obtaining a PWM signal corresponding to a specified average current
C2, a transistor Q2 as a switching element controlled by the PWM signal of its output, and a solenoid drive circuit 20 comprising an integral amplifier circuit AM for determining the feedback amount by a resistor R3 inserted in series with the solenoid S.
And the solenoid S by the solenoid drive circuit 20
An overcurrent is detected by a transistor Q3 from a series resistor R1 connected to a power supply supplied to a resistor R3 inserted in series with a solenoid S of the comparator circuit IC1 and an integral amplifier circuit A.
An instantaneous overcurrent detection circuit 30 that adds a predetermined current to an input terminal that is a part of a feedback control circuit 20A including M and holds the current for a predetermined time, and a power supply that supplies a solenoid S by a solenoid drive circuit 20. A voltage is detected from the connected series resistors R1 and R2, the voltage is integrated, and when a predetermined integration value is reached, a predetermined current is added to the feedback control circuit 20A and the integration current is held for a predetermined time. It is composed of a detection circuit 40.

In particular, in the present embodiment, the instantaneous overcurrent detection circuit 30 does not operate for a slight short circuit, and the integrated current detection circuit 40 judges it. Therefore, the interlayer short circuit of the solenoid S and the solenoid S Even if a short circuit occurs on the ground side near the ground side, it can be used up to the limit of use, so the entire system will not be stopped due to a minor abnormality. Further, it can be handled in a fail-safe manner depending on the usage state.

In the solenoid output circuit 10 of the above embodiment, a plurality of series resistances R1, R2, and R3 are connected to the solenoid S. By having a change, 1
It is also possible to use individual series resistors.

Further, as the solenoid drive circuit 20, a comparison circuit IC1 and a modulation circuit IC2 are used to provide a predetermined PW.
Although the M signal has been obtained, when the present invention is carried out, it is sufficient to add the signals arriving at the modulation circuit configured by the comparator and the like, so that it can be carried out as a PWM modulator.

The instantaneous overcurrent detection circuit 30 and / or the integrated current detection circuit 40 sends a signal only to the feedback circuit 20A when an abnormality is detected. However, in the case of implementing the present invention, The output of the instantaneous overcurrent detection circuit 30 and / or the integrated current detection circuit 40 can be used as an abnormality detection signal as a notification signal for display or the like.

[0039]

As described above, the current limiting device for the solenoid drive circuit of the present invention energizes the solenoid with a pulse width-modulated pulse signal corresponding to the average current designated by the solenoid drive circuit. In the solenoid drive circuit for feedback controlling the pulse signal, the overcurrent detection circuit detects overcurrent conduction from the series resistance connected to the power supply to the solenoid at that time, and adds a predetermined current to the feedback control circuit. , Hold it for a predetermined time, detect the current from the series resistance connected to the power supply to the solenoid, integrate it, and when it reaches a predetermined integrated value, feed the feedback control circuit with the predetermined current. Is added and held for a predetermined time.

Therefore, the switching element is instantly and surely protected against a large current flowing in a moment when the solenoid is energized, and when the scale of the interlayer short circuit of the solenoid is small, or the earth side of the solenoid is connected. When short-circuited to the ground side in the vicinity, prevent the appearance of an undesired state of the solenoid that is not energized, and limit the energizing current under the condition that energization is maintained, and use while suppressing the power consumption of the switching element and solenoid. However, the switching element can be protected.

[Brief description of drawings]

FIG. 1 is an overall circuit diagram of a current limiting device for a solenoid drive circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional current limiting device for a solenoid drive circuit.

FIG. 3 is a timing chart when the duty ratio of the solenoid of the conventional solenoid drive circuit is controlled.

[Explanation of symbols]

 L solenoid R1, R2, R3 low resistance IC1 comparison circuit IC2 modulation circuit Q2 transistor (switching element) Q1, Q3 transistor AM integration amplification circuit 10 solenoid output circuit 20 solenoid drive circuit 30 instantaneous overcurrent detection circuit 40 integration current detection circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyuki Hamada 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. A solenoid output circuit comprising a solenoid connected in series with a low resistance and connected to a power source, and a pulse width-modulated pulse signal corresponding to a specified average current is energized to the solenoid. A solenoid drive circuit that controls feedback of a pulse signal, and an overcurrent conduction is detected from a series resistance connected to a power supply supplied to the solenoid by the solenoid drive circuit, and a predetermined current is added to the feedback control circuit for a predetermined time. An instantaneous overcurrent detection circuit that holds the voltage, a voltage is detected from a series resistance connected to a power supply supplied to the solenoid by the solenoid drive circuit, the voltage is integrated, and when a predetermined integrated value is reached, the feedback control is performed. Equipped with an integrated current detection circuit that adds a predetermined current to the circuit and holds it for a predetermined time A current limiting device for a solenoid drive circuit, characterized in that