JPH0717823Y2 - Electromagnetic pump drive circuit - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic pump drive circuit for driving an electromagnetic pump used in a combustor or the like.

[0002]

2. Description of the Related Art FIG. 2 shows a conventional electromagnetic pump drive circuit. In the figure, 1 is an AC power supply, 2 is an insulation transformer, 3a and 3b are diode bridges, 4 is a constant voltage element, 5 is a micro computer (hereinafter referred to as a microcomputer), and 6a is a light emitting diode of the photocoupler 6. 6b is a transistor of the photocoupler 6 and 7 is an electromagnetic pump (M
P), C1 and C2 are capacitors, r1 to r4 are resistors,
ZD is Zener diode, D1 is diode, TR1
Is a switching transistor, and TR2 is a transistor.

Here, a resistor r2 and a transistor TR
2 and the Zener diode ZD constitute a DC constant voltage power supply, and the DC constant voltage power supply and the photocoupler 6
Transistor 6b, diode D1, transistor T
A drive circuit for the electromagnetic pump 7 is configured by R1 and the resistors r3 and r4.

The output of the insulation transformer 2 to which the AC power is applied is rectified and smoothed by the diode bridge 3a, the capacitor C1, the diode bridge 3b and the capacitor C2, respectively. The transformer output smoothed by the capacitor C1 is applied as a DC constant voltage to the microcomputer 5 via the constant voltage element 4. As a result, a pulse as a control signal having a period adjusted in advance from the microcomputer 5 is emitted from the light emitting diode 6a of the photocoupler 6.
Is output to the cathode side of. This makes the light emitting diode
The dot 6a emits light at a predetermined cycle.

With the light emission of the light emitting diode 6a, the transistor 6b of the photocoupler 6 is turned on, and the transistor TR1 is also turned on. Further, as the transistor TR1 is turned on, a constant DC voltage is applied to the electromagnetic pump 7, and the electromagnetic pump 7 is driven. The drive state of the electromagnetic pump 7 is maintained while the transistor TR1 is on, that is, while the photocoupler 6 is on. Here, when the photocoupler 6 is turned off and the transistor TR1 is turned off, the voltage application to the electromagnetic pump 7 is stopped,
The electromagnetic pump 7 stops.

[0006]

However, in the above-mentioned conventional circuit, the voltage application to the electromagnetic pump 7 is controlled via the transistor TR1.
The output of the DC constant voltage power supply is easily affected by the loss of the transistor TR1, and there is a drawback that a stable pump output cannot be obtained.

Further, in the above-mentioned conventional circuit, the microcomputer 5 and the photocoupler 6 may malfunction due to noise or the like,
Alternatively, if these fail and the transistor 6b of the photocoupler 6 is continuously energized, the electromagnetic pump 7 continues to be driven, resulting in an unnecessary pump output.

The present invention has been made in view of the above circumstances, and an object thereof is to apply a constant voltage to an electromagnetic pump without being affected by the loss of a switching transistor and to improve safety and reliability. An object is to provide an electromagnetic pump drive circuit.

[0009]

In order to achieve the above object, the invention of claim 1 is an electromagnetic pump drive circuit for applying a constant voltage to an electromagnetic pump based on a control signal, wherein switching is performed on / off based on the control signal. And a constant voltage power source for applying a constant voltage to the electromagnetic pump driven by the ON operation of the switching transistor.

According to a second aspect of the invention, in the electromagnetic pump drive circuit according to the first aspect, there is provided a protection circuit for forcibly turning off the switching transistor after a lapse of a predetermined time after the switching transistor is turned on. It has a feature.

[0011]

According to the first aspect of the present invention, when the switching transistor is turned on based on the control signal, the constant voltage power source is driven by this, and the constant voltage is applied from the constant voltage power source to the electromagnetic pump.

According to the second aspect of the invention, after a lapse of a predetermined time after the switching transistor is turned on, the transistor is forcibly turned off and the voltage application to the electromagnetic pump is stopped. Other functions are similar to those of the first aspect of the invention.

[0013]

FIG. 1 shows an electromagnetic pump drive circuit according to the present invention. In this embodiment, the same reference numerals are used for the parts having the same configurations as those of the conventional example (FIG. 2). In the figure, 1 is an AC power supply, 2 is an insulation transformer, 3a and 3b are diode bridges, 4 is a constant voltage element, 5 is a microcomputer, and 6
Is a photo coupler, and 6a is a light emitting diode of the photo coupler 6.
, 6b is a transistor of the photocoupler 6, 7 is an electromagnetic pump (MP), 7a and 7b are terminals of the electromagnetic pump 7, 10
Is a DC constant voltage power supply, 10i is an input terminal, 10o is an output terminal, 10c is a common terminal, 11 is a protection circuit, and C1, C2.
C3 is a capacitor, r1, R1 to R7 are resistors, and 3ZD
Is a 3-terminal shunt regulator (for example, TL431 manufactured by Texas Instruments), D1 and D2 are diodes, TR1 and TR2 are NPN type transistors, and TR.
3 is a PNP type transistor.

Here, the drive circuit of the electromagnetic pump 7 is constituted by the DC constant voltage power source 10, the protection circuit 11, the transistor 6b of the photocoupler 6, the diode D1 and the transistor TR1.

The DC constant voltage power source 10 is a transistor TR.
1, which supplies a constant DC voltage to the electromagnetic pump 7 only when the transistor 1 is in the ON state, the transistor TR2 and the resistors R1 to R3.
And a shunt regulator 3ZD.

Explaining these connection states, the collector of the transistor TR2 is connected via the input terminal 10i to the midpoint of connection between the diode bridge 3b and one terminal of the capacitor C2, and the emitter is connected to the terminal 7a of the electromagnetic pump 7. It is connected to the midpoint of connection of the diode D1 with the cathode. A resistor R1 is connected between the collector and the base, and the cathode of the shunt regulator 3ZD is connected to the midpoint of the connection between the resistor R1 and the base. further,
Resistors R2 and R3 are connected in series between the emitter of the transistor TR2 and the anode of the shunt regulator 3ZD. The midpoint of connection between these resistors R2 and R3 is the control terminal of the shunt regulator 3ZD. It is connected.

The transistor TR1 has an anode of the shunt regulator 3ZD, that is, a common terminal 1.
0c and the terminal 7b of the electromagnetic pump 7 (the anode of the diode D1) are connected to the midpoint, and the emitter is connected to the midpoint of the diode bridge 3b and the other terminal of the capacitor C2. The base is connected to the protection circuit 11 via a resistor R4.

The protection circuit 11 includes a transistor TR1 when the transistor 6b of the photocoupler 6 is in the ON state.
Is maintained for a certain time, and is composed of a transistor TR3, a diode D2, a capacitor C3 and resistors R5 to R7.

Explaining these connection states, the emitter of the transistor TR3 is connected to the midpoint of connection between the diode bridge 3b and one terminal of the capacitor C2, and the collector is connected to the base of the transistor TR1 via the resistor R4. It is connected. Also, a resistor R is provided between the emitter and the base.
5 is connected, and the midpoint of connection between the resistor R5 and the base is connected to the collector of the transistor 6b of the photocoupler 6 via the resistor R6 and the capacitor C3. Further, the diode D2 is connected in such a manner as to be in the forward direction from the midpoint of connection between the resistor R6 and the capacitor C3 toward the emitter of the transistor TR3, and the cathode of the diode D2 is connected.
A resistor R7 is connected between the connection midpoint between the capacitor C3 and the transistor 6b. Also, the transistor 6b
Is connected to the emitter of the transistor TR1, that is, the midpoint of connection between the diode bridge 3b and the other terminal of the capacitor C2.

Next, the operation of the above circuit will be described. The output of the insulation transformer 2 to which the AC power is applied is rectified and smoothed by the diode bridge 3a, the capacitor C1, the diode bridge 3b, and the capacitor C2. The transformer output smoothed by the capacitor C1 is applied as a DC constant voltage to the microcomputer 5 via the constant voltage element 4. As a result, a pulse as a control signal having a cycle adjusted in advance from the microcomputer 5,
The light is output to the cathode side of the light emitting diode 6a of the photocoupler 6. As a result, the light emitting diode 6a emits light at a predetermined cycle.

As the light emitting diode 6a emits light, the transistor 6b of the photocoupler 6 is turned on. As a result, the transistor TR3 is turned on and charging of the capacitor C3 is started. Also, the transistor TR
With the turning on of 3, the transistor TR1 is turned on.

When the transistor TR1 is turned on, the equilibrium state of the shunt regulator 3ZD of the DC constant voltage power supply 10 is broken, and a DC constant voltage is applied from the DC constant voltage power supply 10 to the electromagnetic pump 7 to cause the electromagnetic pump 7 to operate. To drive.
The driving state of the electromagnetic pump 7 is maintained while the transistor TR1 is on, that is, until the transistor 6b of the photocoupler 6 is off.

Further, for example, even if the transistor 6b of the photocoupler 6 remains in the ON state for a certain period of time, the capacitor C3 of the protection circuit 11 is gradually charged with electric charge, and after a predetermined time has elapsed, the transistor Tb is turned on.
When the base potential of R3 reaches a predetermined potential, the transistor TR
3 turns off. Along with this, the transistor TR1 is also turned off. As a result, the application of the DC constant voltage from the DC constant voltage power supply 10 to the electromagnetic pump 7 is stopped, and the electromagnetic pump 7 is stopped.

As described above, according to this embodiment,
Since the electromagnetic pump 7 and the DC constant voltage power supply 10 for applying a DC constant voltage thereto are driven by the switching transistor TR1, the output of the DC constant voltage power supply 10 is not affected by the loss of the transistor TR1. Therefore, it is possible to supply the electromagnetic pump 7 accurately and stably.

Further, since the protection circuit 11 for suppressing the ON state of the transistor TR1 is provided for a predetermined time or more regardless of the driving state of the photocoupler 6, the reliability of the driving circuit can be improved.

In this embodiment, the DC constant voltage power supply is composed of the shunt regulator 3ZD and the transistor TR2, but the present invention is not limited to this, and the Zener diode and the transistor are used. It goes without saying that a device using a three-terminal regulator or the like can be applied.

[0027]

As described in detail above, according to the first aspect of the invention, since the constant voltage power source can be driven by the switching transistor to apply the constant voltage to the electromagnetic pump, the output of the constant voltage power source is switched. It is possible to supply the electromagnetic pump accurately and stably without being affected by the loss of the use transistor.

According to the second aspect of the present invention, even when the electromagnetic pump continues to be driven due to malfunction or failure, the ON time of the switching transistor is limited to forcibly stop the electromagnetic pump, and safety, It is possible to improve reliability. The other effects are the same as those of the invention of claim 1.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an electromagnetic pump drive circuit according to the present invention.

FIG. 2 is a conventional electromagnetic pump drive circuit diagram.

[Explanation of symbols] 1 ... AC power supply, 2 ... Insulation transformer, 3
a, 3b ... Diode bridge, 4 ... Constant voltage element, 5 ...
Microcomputer, 6 ... Photo coupler, 6a ... Light emitting diode, 6b ... Transistor, 7 ...
Electromagnetic pump (MP), 7a, 7b ... Terminal, 10 ... DC constant voltage power supply, 10i ... Input terminal, 10o ... Output terminal, 10
c ... Common terminal, 11 ... Protection circuit, TR1 ... NPN type transistor (switching transistor).

Claims (2)

[Scope of utility model registration request] 1. An electromagnetic pump drive circuit for applying a constant voltage to an electromagnetic pump based on a control signal, wherein:
And a switching transistor that turns on and off,
It is driven by the ON operation of the switching transistor.
Equipped with a constant voltage power supply for applying a constant voltage to the electromagnetic pump
And, an electromagnetic pump drive circuit, characterized in that. 2. A switching transistor is turned on.
Electromagnetic pump drive circuit according to claim 1, wherein the to and including a protection circuit for forcibly Oh <br/> off the transistor after a predetermined time has elapsed, characterized in that.