JPH05152126A - Driving circuit for plunger solenoid - Google Patents

Abstract

PURPOSE:To provide a driving circuit which returns a self-holding type plunger solenoid to the return state when a power-supply voltage is dropped. CONSTITUTION:The followings are installed: a self-holding type plunger solenoid 1; a driving circuit 2 which drives the plunger solenoid 1; a microcomputer 3 which supplies a control signal to the driving circuit 2; and a DC power supply 4 which supplies an operating voltage to the driving circuit 2 and the micro-computer 3. The followings are installed: a diode D11 for reverse-current prevention; a capacitor C11; a voltage detection circuit 11 which detects an output voltage of the DC power supply 4; and a circuit 12 which supplies the detection output of the voltage detection circuit 11 to the driving circuit 2 in parallel with the control signal supplied to the driving circuit 2 from the micro-computer 3. When the output voltage of the DC power supply is dropped, the operation of the driving circuit 2 is maintained by the charging voltage of the capacitor C11, the driving circuit 2 is controlled by the detection output of the voltage detection circuit 11 and the plunger solenoid 1 is returned to the return state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a self-holding plunger solenoid.

[0002]

2. Description of the Related Art Plunger solenoids (hereinafter referred to as "solenoids") are roughly classified into energization-holding solenoids and self-holding solenoids.

The energization-holding type solenoid is in the attracting state by generating the holding force while the power is being supplied, and is in the returning state by losing the holding force while the power is not being supplied. Therefore, this energization-holding solenoid returns to the return state when the drive voltage is not supplied due to a power failure or the like in the attracting state, so that a trouble in use hardly occurs.

For example, when it is used for driving a pinch roller or reel of a data recorder, even if a power failure occurs during reproduction, the data recorder will be in a stopped state.
Does not damage the data recorder or tape.

However, the energization-holding type solenoid always consumes electric power when it is in the attracting state, resulting in a large power consumption. In addition, it also generates a large amount of heat and is not suitable for small devices.

On the other hand, the self-holding solenoid is in a suction state when a negative drive pulse voltage is supplied, and returns to a return state when a positive drive pulse voltage is supplied. When the drive voltage is not supplied, the attracted state or the restored state is maintained.

Therefore, this self-holding solenoid consumes less electric power and is suitable for power-saving equipment, and since it also generates less heat, it is also suitable for small equipment.
However, even if the drive voltage is not supplied due to a power failure or the like in the suction state, the suction state is maintained and the return state is not returned, which may cause a trouble.

[0008]

As described above, the self-holding type solenoid consumes less electric power and is suitable for power saving equipment or small equipment, but there is a power failure or the like in the suction state. However, since it does not return to the recovery state, trouble may occur.

The present invention is intended to solve such a problem in a self-holding solenoid.

[0010]

Therefore, in the present invention, when the reference numerals of the respective parts correspond to the embodiments described later, a self-holding type plunger solenoid 1 and a predetermined drive pulse voltage for the plunger solenoid 1 are provided. Drive circuit 2 for driving the plunger solenoid 1 to the suction state and the return state, a microcomputer 3 for supplying a control signal to the drive circuit 2 to output a drive pulse voltage, the drive circuit 2 and the microcomputer 3 A DC power supply 4 for supplying these operating voltages to the DC power supply 4, a diode D11 for preventing backflow connected in series between the DC power supply 4, the power supply line 5 of the drive circuit 2 and the microcomputer 3, and the diode D11 of the diode D11. On the output side, connected to the power line 5 and connected to the DC power source 4
From the microcomputer 3 to the drive circuit for detecting the output of the DC power supply 4 and the voltage detection circuit 11 for detecting whether or not the output voltage of the DC power supply 4 is a predetermined value or more. A circuit 12 for supplying the drive circuit 2 is provided in parallel with the control signal supplied to the drive circuit 2. Then, when the output voltage of the DC power supply 4 is no more than the predetermined value, the operation of the drive circuit 2 is maintained by the charging voltage of the capacitor C11, and
The drive circuit 2 is controlled by the detection output of the voltage detection circuit 11 to return the plunger solenoid 1 to the return state.

[0011]

In the normal state, the control signal from the microcomputer 3 is supplied to the drive circuit 2 to control the plunger solenoid 1 to the attracting state or the returning state. However, when the output voltage of the power source 4 drops, this is detected by the voltage detecting circuit. Another control signal detected by 11 and based on the detection output is supplied to the drive circuit 2 in parallel with the control signal from the microcomputer 3, and as a result, the plunger solenoid 1 is returned to the return state.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is a plunger solenoid to be controlled, 2 is its drive circuit, 3 is a microcomputer, and 4 is a DC power supply.

The output voltage V4 of the DC power supply 4 is supplied to a power supply terminal Vcc of the microcomputer 3 and a power supply terminal Vcc of the drive circuit 2 through a backflow prevention diode D11 and a power supply line 5 which will be described later.

In this case, the drive circuit 2 is one chip I
It has been converted to C, and as shown equivalently in FIG.
The switching transistors Q1 to Q4 are bridge-connected, one pair of connection points is the power supply terminal Vcc and the ground terminal GND, and the other pair of connection points is the output terminal.
These are OUT1 and OUT2. And these output terminals OUT
The solenoid 1 is connected between 1 and OUT2. Further, the drive circuit 2 has input terminals IN1 and IN2,
According to the voltage level of these input terminals IN1 and IN2,
The on / off states of the transistors Q1 to Q4 are controlled, and the output terminals OUT1 and OUT2 have "H" level, "L" level or high output impedance. That is, in this example, when IN1 = "H" and IN2 = "L", OUT1 = "L", OUT
2 = "H" IN1 = "L", IN2 = "H", OUT1 = "H", OUT
When 2 = “L” IN1 = “H” and IN2 = “H”, OUT1 and OUT2 = high output impedance.

Further, in this example, the solenoid 1
Is in the suction state when OUT1 = "L" and OUT2 = "H". When OUT1 = "H" and OUT2 = "L", the return state is entered. When OUT1 and OUT2 = high output impedance, the current holding state is set. I shall.

Further, the microcomputer 3 forms a control signal for the solenoid 1 in accordance with a user's key operation and an operating state of a device using this circuit. Therefore, the microcomputer 3 has an output port (not shown).
Output terminals P1 and P2, and the output transistor (or output FET) of the output port is an open collector. The output terminals P1 and P2 are connected to the power supply line 5 through the pull-up resistors R1 and R2, and the input terminals IN1 and IN of the drive circuit 2 are connected.
It is connected to 2 and controls the voltage level of these terminals IN1 and IN2.

Further, the DC power source 4 is equivalent to the power source of the device in which this circuit is used. In practice, for example, the commercial AC voltage is AC / DC converted to drive the drive circuit 2 and the microcomputer. 3 operating voltages are formed.

Under normal conditions, the voltage levels of the input terminals IN1 and IN2 of the drive circuit 2 are controlled by the control signals from the output terminals P1 and P2 of the microcomputer 3, and as a result, the output terminals OUT1 and OUT2 of the drive circuit 2 are controlled. Is controlled as described above to supply the suction pulse voltage or the return pulse voltage to the solenoid 1, and the solenoid 1 is controlled to the suction state or the return state.

That is, when the solenoid 1 is brought into the attracting state, IN1 = “H” and IN2 = “L” are temporarily set by the control signal from the microcomputer 1, and OUT1 =
"L", OUT2 = "H", a drive pulse voltage in the positive direction is supplied to the solenoid OUT1 from the terminal OUT2, and the drive pulse voltage causes the solenoid 1 to be attracted.
Then, after that, IN1 = "H" and IN2 = "H" are set, the terminals OUT1 and OUT2 are set to the high output impedance state, and the suction state of the solenoid 1 is maintained.

Further, when the solenoid 1 is returned to the reset state, the control signal from the microcomputer 1 causes a temporary IN
1 = "L", IN2 = "H", OUT1 = "H", OU
T2 = “L”, the drive pulse voltage in the positive direction of the terminal OUT1 is supplied to the solenoid 1, and the drive pulse voltage returns the solenoid 1 to the return state. And
After that, IN1 = "H", IN2 = "H", and the terminal
OUT1 and OUT2 are in a high output impedance state, and the return state of the solenoid 1 is maintained.

Furthermore, in order to cope with the case where the output voltage V4 of the DC power supply 4 suddenly stops being output due to a power failure or the like,
The present invention is further configured as follows.

That is, the backflow preventing diode D11 is connected to the power supply line 5 as described above, and the capacitor C11 is connected to the power supply line 5 on the output side of the diode D11. The capacitor C11 is for holding the voltage of the entire circuit for a necessary period when the output voltage V4 of the power source 4 drops, and therefore has a relatively large capacity.

Further, a voltage comparison circuit 11 is provided as a detection circuit for detecting the output voltage V4 of the power supply 4. And the series circuit of the resistors R11 and R12 is connected in parallel to the power source 4 and
The divided voltage V12 of the output voltage V4 of the above is taken out, this voltage V12 is supplied to the non-inverting input terminal of the comparison circuit 11, and a predetermined reference voltage V14 is formed by the resistor R13 and the constant voltage diode D12. The voltage V14 is the comparison circuit 1
1 is supplied to the inverting input terminal.

The output voltage V15 of the comparison circuit 11 is
But resistor R14 → transistor Q11 → resistors R15, R16
Is supplied to the base of the transistor Q12 through the signal line and the collector of the transistor Q12 is connected to the output terminal P1 of the microcomputer 3. At this time,
The terminal P1 and the collector of the transistor Q12 constitute the wired OR circuit 12 of negative logic.

Further, an output port (not shown) is prepared for the microcomputer 3, and a time constant circuit 13 having resistors R18, R19 and a capacitor C12 at an output terminal P3 of the output port.
Is connected to the base of the transistor Q13 and its collector is connected to the resistor R17.
Through to the base of the transistor Q14. And between the collector and emitter of this transistor Q14,
It is connected in series between the emitter of the transistor Q11 and the power supply line 5.

With such a configuration, when the output voltage V4 of the power source 4 decreases, the voltage of each part changes as shown in FIG. 2 and the solenoid 1 is returned to the reset state.

That is, in FIG. 2, it is assumed that the time point t3 is the time point when the supply of the output voltage V4 of the power source 4 is stopped. Further, the voltage drop of the diode D11 is set to the voltage Vf.

Then, before the time t3, the output voltage V4 of the power source 4 is normal, and the voltage V13 from the diode D11.
(= V4-Vf) is output, and this voltage V13 is supplied to the microcomputer 3 and the drive circuit 2 as their operating voltage through the power supply line 5.

Since the output voltage V4 is normal before the time t3, V12> V14, and therefore these voltages V4
The voltage V15, which is a comparison output of 12 and V14, is at "H" level.

When V15 = "H", the transistor Q11 is off, and the voltage V18 at the connection point of the resistors R15 and R16 is "L" level, so the transistor Q12 is also off. If the transistor Q12 is off, it is equivalent to the transistor Q12 not being connected to the output terminal P1 or the input terminal IN1.

Therefore, before the time t3, as described above, the microcomputer 3 can control the solenoid 1 through the drive circuit 2 to the suction state or the return state.

When it is predicted that inconvenience will occur if the supply of the output voltage V4 of the power source 4 is stopped while the solenoid 1 is in the attracting state, the microcomputer 3 sets its output terminal P3 to the "H" level. And In FIG. 2, P3 = "H" is set at time t1.

Then, when P3 = "H" at time t1,
When the output voltage V16 of the time constant circuit 13 gradually increases from the time point t1 to the voltage at the time point t2, the transistor Q13 is turned on and the transistor Q14 is turned on. Then, from this time t2, the transistor Q
The emitter voltage V17 of 11 becomes "H" level.

However, even if V17 = "H", the time t3
Previously, the voltage V15 caused the transistor Q11 to
Is off and transistor Q12 is off. Therefore, before the time t3, the solenoid 1 is operated by the microcomputer 3
Is controlled to a suction state or a return state.

Then, at time t3, the output voltage V4 of the power source 4
When the supply of V is stopped, the voltage V4 gradually decreases from the time point t3, and the voltage V12 also gradually decreases in proportion to this.

Then, the voltage V12 drops and V becomes V at time t4.
When 12 ≦ V14, V15 = “L”, so that the transistor Q11 is turned on. At this time, since the voltage V17 is supplied to the emitter of the transistor Q11, the voltage becomes V from time t4.
18 = “H”. Therefore, since the transistor Q12 is turned on from the time point t4, the drive circuit 2 becomes IN1 = "L" from the time point t4. At this time, the drive circuit 2 can operate normally due to the voltage charged in the capacitor C11, and IN2 = "H".

Therefore, at time t4, IN1 = "L", IN
Since 2 = “H”, the drive circuit 2 returns the solenoid 1 to the return state.

At time t5, the voltage V16 becomes lower than the base-emitter voltage of the transistor Q13, so that the transistor Q13 is turned off, which turns off the transistor Q14 and turns off the transistor Q11. The transistor Q12 is also turned off. Therefore, from time t5, IN1 = "H" and IN2 = "H",
Since the output terminals OUT1 and OUT2 are in the high impedance state and the voltage V13 of the power supply line 5 is also considerably lowered, the solenoid 1 continues to be in the return state.

Thus, at the time t3, the output voltage V of the power source 4
Even if the supply of 4 is stopped, the solenoid 1 is returned to the reset state at the subsequent time t4.

The time constant circuit 13, especially the capacitor C
Reference numeral 12 is for turning on the transistor Q13 until the solenoid 1 returns to the reset state when the voltage V4 drops. The resistor R19 is a transistor Q.
This is for discharging the electric charge of the capacitor C13 when the on / off of 13 is continuously repeated.

Next, a method of setting each part of this drive circuit will be described. First, when the output voltage V4 of the power source 4 decreases from the normal value by the resistance ratio of the resistors R11 and R12 and the Zener voltage V14 of the constant voltage diode D12, a control signal for returning the solenoid 1 to the reset state is given. It can be set whether to form.

For example, the voltage V4 is less than αV4 (α <1)
If it is desired to return the solenoid 1 to the reset state when it becomes, when R12 / (R11 + R12) = β, the values α and β are set so that αβV4 = V14, and the constant voltage diode D12 is set. Make a selection. Subtle adjustment may be made by setting the resistance ratio of the resistors R11 and R12 according to the constant voltage diode D12.

With the above setting, when the voltage V4 drops to αV4, the output voltage V15 of the comparison circuit 11 changes from the "H" level to the "L" level. It must meet one condition. That is, even if the voltage V15 changes from the "H" level to the "L" level and the transistor Q11 is turned on, the transistor Q12 is not turned on unless the sufficient voltage V17 is supplied to the emitter of the transistor Q11. Instead, it remains off, so the solenoid 1 does not return to the return state.

To supply a sufficient level of voltage V17 to the emitter of transistor Q11, transistor Q11
It suffices if 14 is on, for this purpose transistor Q13
Must be on, and for this purpose, the output terminal P3 of the microcomputer 3 must be at "H" level.

Therefore, whether or not the pulse voltage for returning the solenoid 1 to the reset state is supplied when the voltage V4 of the power source 4 drops can be selected by the level of the output terminal P3 of the microcomputer 3.

When it is not necessary to return the solenoid 1 to the return state, if the output terminal P3 is set to "L" level, the solenoid 1 retains the previous state even if the voltage V4 is lowered. In addition, it can be used as a safety mechanism in the case where the solenoid 1 must not operate in the process of the voltage V4 gradually rising from zero.

As described above, according to the present invention, the power source 4
Of the output voltage V4 is detected by the comparator circuit 1, and when the voltage V4 becomes less than the specified value, the control signal based on the detected output voltage V15 is transmitted to the transistors Q11, Q12 and the OR circuit 12 Through microcomputer 3
It is supplied to the drive circuit 2 in parallel with the control signal from. Therefore, if the supply of the output voltage V4 of the power supply 4 is stopped while the solenoid 1 is in the attracting state, the solenoid 1 immediately returns to the reset state and no trouble occurs.

Further, when the output voltage V4 of the power source 4 is not supplied in this way, the solenoid 1 returns to the return state, so that the self-holding type solenoid 1 can be used as the solenoid 1 and power saving can be realized. .. That is, it is possible to realize both power saving and stable operation of the solenoid.

Further, when the output voltage V4 of the power source 4 is no longer supplied, the degree of freedom in setting the conditions for returning the solenoid 1 to the return state is large, so that it can be applied to a wide range.

In the example shown in FIG. 4, the microcomputer 3 is
This is a case where the voltage comparison circuit 11 is realized by the A / D converter and software when the / D converter is built in. Further, FETs (Q11 to Q14) are used instead of the transistors Q11 to Q14.

That is, in this example, the voltage V12 is supplied to the microcomputer 3, and the microcomputer 3 compares the voltage with the reference voltage V14 by software.
The comparison output is the output terminal P4 of the output port of the microcomputer 3.
To the output voltage V15. In addition, resistor R20
Is a pull-down resistor for turning on the FET (Q11) when the voltage V13 at the terminal Vcc of the microcomputer 3 drops.

Therefore, as in the example of FIG. 1, when the voltage V4 of the power source 4 drops, the solenoid 1 can be returned to the return state. Further, when the power is turned on, V15 = “L”, but the FET (Q12) is in the off state by the time constant circuit 13 and the FETs (Q13, Q14), and the drive circuit 2 does not malfunction.

In the above description, when the voltage drop of the diode 11 becomes a problem, a plurality of diodes connected in parallel, a Schottky diode, or the collector / emitter of the transistor may be connected instead of the diode 11.

[0054]

According to the present invention, the output voltage V of the power source 4 is
It is detected by the comparator circuit 1 whether 4 is equal to or higher than the specified value, and when the voltage V4 becomes equal to or lower than the specified value, the control signal based on the detected output voltage V15 is applied to the transistor Q11
Through the Q12 and the OR circuit 12, the control signal from the microcomputer 3 is supplied in parallel to the drive circuit 2. Therefore, if the supply of the output voltage V4 of the power supply 4 is stopped while the solenoid 1 is in the attracting state, the solenoid 1 immediately returns to the reset state and no trouble occurs.

Further, when the output voltage V4 of the power source 4 is not supplied in this way, the solenoid 1 returns to the return state, so that the self-holding type solenoid 1 can be used as the solenoid 1 and power saving can be realized. .. That is, it is possible to realize both power saving and stable operation of the solenoid.

Further, when the output voltage V4 of the power source 4 is no longer supplied, the degree of freedom in setting conditions for returning the solenoid 1 to the return state is large, so that it can be applied to a wide range.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of the present invention.

FIG. 2 is a waveform diagram of each part of the example of FIG.

FIG. 3 is an equivalent circuit diagram of part of a drive circuit.

FIG. 4 is a system diagram showing another example of the present invention.

[Explanation of symbols]

 1 Plunger Solenoid 2 Drive Circuit 3 Microcomputer 4 DC Power Supply 5 Power Supply Line 11 Voltage Comparison Circuit 12 Wired OR Circuit 13 Time Constant Circuit

Claims (1)

[Claims] 1. A self-holding type plunger solenoid, a drive circuit for supplying a predetermined drive pulse voltage to the plunger solenoid to drive the plunger solenoid to a suction state and a return state, and a control signal to the drive circuit. Between the microcomputer for outputting the drive pulse voltage and the DC power supply for supplying the operating voltage to the drive circuit and the microcomputer, and between the DC power supply and the power line of the drive circuit and the microcomputer. A diode for backflow prevention connected in series with the capacitor, a capacitor connected to the power supply line on the output side of the diode and charged by the output voltage of the DC power supply, and an output voltage of the DC power supply having a predetermined value or more. Voltage detection circuit to detect whether there is And a circuit for supplying the detection output of the voltage detection circuit to the drive circuit in parallel with the control signal supplied from the microcomputer to the drive circuit, wherein the output voltage of the DC power supply is the predetermined value. When the above is no longer the case, the operation of the drive circuit is maintained by the charging voltage of the capacitor, and the drive circuit is controlled by the detection output of the voltage detection circuit to return the plunger solenoid to the reset state. Solenoid drive circuit.