JPH0543334Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] This invention is applied to a drive device for a solenoid valve used in hydraulic equipment, etc., especially a semiconductor switching device that controls energization/deenergization of a solenoid in response to a small current input signal. This relates to prevention of malfunction of elements.

[Prior Art] In order to prevent signal lines and external equipment from being affected by electromagnetic noise generated when a solenoid is turned on and off, a special method is used, for example, to use a microcurrent signal-operated solenoid valve that controls the solenoid on and off using a small current. Gansho 60-
No. 187194 (filed on August 28, 1985), application filed in 1987-
No. 129937 (filed on August 28, 1985), Utility Application No. 1982-
No. 33254 (filed on March 7, 1988), etc.

FIG. 4 is a circuit diagram showing a conventional drive device that energizes and deenergizes a solenoid of a solenoid valve using a small current control signal. In the figure, a solenoid 4 of a solenoid valve is connected to one terminal 1 of a pair of power supply terminals 1 and 2 connected to an external DC excitation power source 3.
A collector-emitter output circuit of the power transistor 5 is connected in series with the collector-emitter output circuit of the power transistor 5. The photocoupler 6 constituting the input circuit consists of a light emitting diode (hereinafter referred to as LED) 6a as an input side element and a light emitting phototransistor 6b as an output side element.
a is connected to signal input terminals 9 and 10 via a constant current diode 7, which is a current limiting element, and a Zener diode 8, which prevents leakage current from flowing. On the other hand, the collector of the phototransistor 6b is connected to the power supply line via the resistor 11, and the emitter is connected to the base of the power transistor 5. 12 is a constant voltage diode, 13 is a smoothing capacitor, resistor 11 and constant voltage diode 12
and an external DC excitation power supply 3 with a smoothing capacitor 13
The non-smooth DC output is supplied to the phototransistor 6b as a smooth DC output.

14 is a signal transistor which is an output element of an external control means connected to the signal input terminal 10;
5 is a signal power supply. In addition, 16 is solenoid 4
This is a surge absorption element connected between both terminals of the .

In the drive device configured as described above, when the signal transistor 14 is turned on, the voltage of the signal power source 15 is applied between the signal input terminals 9 and 10, and the voltage is limited to a constant value by the constant current diode 7 to the LED 6a. The signal current flows. When this signal current flows, the phototransistor 6b becomes conductive, and
A base current flows through the base of the power transistor 5, and the power transistor 5 becomes conductive. When the power transistor 5 is turned on, an excitation current flows from the DC excitation power source 3 to the solenoid 4, thereby energizing the solenoid 4.

When the external signal transistor 14 is turned off in this state, the signal current flowing through the LED 6a is cut off, the phototransistor 6b becomes conductive, the power transistor 5 is turned off, and the solenoid 4 is deenergized.

In this way, the solenoid 4 is energized/deenergized by flowing a small switching control current through the signal line separated from the excitation power supply line, thereby energizing/deenergizing the solenoid 4 with respect to the signal line.
The influence of electromagnetic noise during de-energization can be reduced.

[Problem to be solved by the invention] In the drive device in which the solenoid 4 is driven by the power transistor 5 as described above, the power transistor 5 generates a large surge voltage from the solenoid 4 when the excitation current flowing through the solenoid 4 is turned off. Therefore, it must have high voltage resistance.
Furthermore, since the excitation current of the solenoid 4 is large, such as several amperes, the power transistor 5 requires a large power and is used in a Darlington connection. Therefore, the DC amplification factor of the power transistor 5 increases, and the phototransistor 6b of the photocoupler 6
Even if the current flowing through is small, the power transistor 5 is turned on. Therefore, even if a photocoupler 6 with a low current transfer rate is used, if the leakage current from the external signal transistor 14 is large, the power transistor 5 may turn on due to this leakage current alone and malfunction. be.

In order to prevent this power transistor 5 from malfunctioning, a Zener diode 8 is connected in series with the LED 6a of the photocoupler 6, and the voltage between the collector and emitter of the signal transistor 14 is lowered to reduce leakage current. However, the voltage between signal input terminals 9 and 10 is still higher than the Zener voltage due to leakage current and minute noise current.
This was not sufficient to prevent malfunction of the power transistor 5.

This invention was made to solve this problem, and even if there is some leakage current or minute noise current in the step-shaped switching command input signal, the semiconductor switching element that energizes and de-energizes the solenoid will malfunction. It is an object of the present invention to provide a solenoid valve drive device that can prevent such problems and operate stably.

[Means for Solving the Problems] The electromagnetic valve drive device according to the invention sends a control signal to a semiconductor switching element connected in series with the solenoid between a pair of power terminals to energize and deenergize the solenoid. In a drive device, a current limiting element and a voltage nonlinear element are connected in series to the input side of a photocoupler that receives a switching command input signal and supplies a control signal isolated from this input signal to the signal input side of a semiconductor switching element. , another current limiting element having a lower saturation current value than the current limiting element is connected in parallel with the signal input line consisting of the input side element of the photocoupler, the current limiting element, and the voltage nonlinear element connected in series. The above-mentioned problems have been achieved by this method.

Further, it is also possible to stabilize the pulsating flow of the input signal by preferably connecting a smoothing circuit including a capacitor in parallel with the signal line.

In a practical embodiment, constant current diodes are used as the current limiting element and another current limiting element to allow a constant current to flow.

[Function] In this invention, a signal input line is connected in parallel to the input side element of the photocoupler that receives a step-like switching command input signal, and a current limiting element and a voltage nonlinear element connected in series with this input side element. , another current limiting element whose saturation current value is lower than that of the current limiting element is connected to form a bypass, so that the current is not controlled until the input signal current from the outside reaches a predetermined current value. is shunted by another current limiting element connected in parallel with the signal input line, thereby preventing the voltage across the signal input line from exceeding the operating voltage of the voltage nonlinear element in that line. . After the input signal current reaches a predetermined value, an input signal current corresponding to the shunt ratio with the bypass path is passed through the signal input line. Electrify the element and operate it. Therefore, the current value of the input signal applied to the signal input terminal can be increased, and leakage current or the like can be prevented from flowing through the signal input line.

Furthermore, by connecting a smoothing capacitor circuit in parallel with the signal input line, it is possible to stabilize the input signal current with ripples.

Furthermore, if constant current diodes are used as the current limiting element and another current limiting element, the input signal current flowing to the signal input side of the photocoupler can be set to an arbitrarily selected constant current value.

[Embodiment] FIG. 1 is a circuit diagram showing an embodiment of this invention. In the figure, numerals 1 to 16 are exactly the same as the conventional example shown in FIG. 17 is another constant current diode, and this another constant current diode 17 is
The LED 6a of the photocoupler 6 connected in series is connected in parallel with a signal input line consisting of a Zener diode 8 and a constant current diode 7. The saturation current _I1 of this other constant current diode 17 is selected to be lower than the saturation current _I2 of the constant current diode 7 connected to the signal input line as shown in FIG. The pinch-off voltage V _P1 of the current diode 17 is selected to be lower than the Zener voltage of the Zener diode 8.

18 is a smoothing capacitor, and the smoothing capacitor 18 is connected in parallel with the other constant current diode 17 via a resistor 19. 20 is a diode that rectifies the input signal input to the signal input terminal 9.

In the solenoid valve drive device configured as described above, when the external signal transistor 14 has no leakage current and is completely off, the voltage of the external signal power source 15 is between the collector and emitter of the transistor 14. , the voltage V ₁ between the signal input terminals 9 and 10 is 0V, and no current flows through the constant current diode 17 and the LED 6a of the phototransistor 6.

When the signal transistor 14 begins to transition from the off region to the on region in this state, current begins to flow through the constant current diode 17. Then, the voltage V ₁ between the signal input terminals 9 and 10 increases, and when the voltage V ₁ reaches the pinch-off voltage V _P1 of the constant current diode 17, a constant current I ₁ flows through the constant current diode 17.
While this voltage V ₁ is lower than the Zener voltage of the Zener diode 8, the current I ₁ flows to the constant current diode 17 side.
flow.

When the signal transistor 14 further transitions to the on region and the voltage V ₁ between the signal input terminals 9 and 10 exceeds the pinch-off voltage V _P2 of the constant current diode 7 and the Zener voltage V ₂ of the Zener diode 8. As shown in FIG. 3, a constant current _I2 determined by a constant current diode 7 flows through the signal input line, causing the LED 6a of the photocoupler 6 to emit light.
This light emission from the LED 6a causes a base current of the power transistor 5 to flow through the phototransistor 6b, turning the power transistor 5 on. As a result, an excitation current flows from the excitation power source 3 to the solenoid 4 via the power transistor 5, energizing the solenoid 4.

In this way, another constant current diode 17 is provided in parallel with the signal input line consisting of the constant current diode 7, the Zener diode 8, and the LED 6a, and a constant current _I1 is first passed through the constant current diode 17, so that the signal input line is Even if leakage current or minute noise current flows through the transistor 14, the signal input terminals 9, 1
The voltage V ₁ between 0 and 0 can be suppressed to a low level, and leakage current and minute noise current can be prevented from flowing in the signal input line.

In addition, even if there is a leakage current, the voltage V ₁ between the signal input terminals 9 and 10 can be kept low, so the Zener voltage of the Zener diode 8
V _Z can be lowered, and the voltage level of the signal power supply 15 can be selected low.

Furthermore, since no leakage current or the like flows through the LED 6a of the signal input line, the current transfer rate of the photocoupler 6 can be increased. Since a relatively large input current _I2 can flow when the voltage _V1 exceeds the Zener voltage _V2 , the switching characteristics of the power transistor 5 can be improved regardless of the operating characteristics of the signal transistor 14. .

In addition, by providing a rectifying diode 20 after the signal input terminal 9 and providing a smoothing capacitor 18 in parallel with the constant current diode 17, the input signal current input from the external signal power source 15 is full-wave rectified. Even if the waveform is not smoothed, the input signal current can be smoothed and provided, and can be used regardless of the type of external signal power source.

[Effects of the invention] As explained above, this invention consists of an input side element of a photocoupler that receives a step-like switching command input signal, and a current limiting element and a voltage nonlinear element connected in series with this input side element. Connect a bypass using another current limiting element with low saturation current in parallel with the signal input line, and connect the external input current to the signal input line until the external input signal current reaches a predetermined current value. Since the voltage of the signal input line does not exceed the operating voltage of the voltage non-linear element by flowing it through the current limiting element in the side circuit parallel to the Malfunction of the switching element can be prevented.

In addition, since it is possible to prevent leakage current from flowing to the input side element of the photocoupler, it is possible to improve the switching characteristics of the semiconductor switching element by using a photocoupler with a large current transfer rate, and to control the transmission of input signals from the outside. The semiconductor switching element can be operated stably regardless of the type of output element of the means.

Furthermore, by connecting a smoothing capacitor in parallel with the signal input line, the semiconductor switching element can be stably operated regardless of the type of external signal power source.

In addition, by using a constant current diode as each current limiting element, the input signal current flowing through the input side element of the photocoupler can be selected to any constant current value, and the circuit configuration is simplified and the device is miniaturized. be able to.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing an embodiment of this invention, Figure 2 is a circuit diagram showing an embodiment of this invention.
The figure is a voltage-current characteristic diagram of the constant current diode of the above embodiment, and Fig. 3 is a voltage-current characteristic diagram showing the operation of the above embodiment.
The current characteristic diagram, FIG. 4, is a circuit diagram showing a conventional example. 1, 2...Power terminal, 4...Solenoid, 5...
...Power transistor, 6...Photocoupler, 7
... Constant current diode, 8 ... Zener diode, 17 ... Another constant current diode, 18 ... Smoothing capacitor.

Claims (1)

[Claims for Utility Model Registration] 1. A semiconductor switching element connected in series with a solenoid between a pair of power terminals, and a control for controlling conduction/cutoff on the signal input side of the semiconductor switching element in response to a switching command input signal. A solenoid valve drive device having a photocoupler that provides a signal, and a current limiting element and a voltage nonlinear element connected in series to an input side element of the photocoupler, the input side element of the photocoupler, the current limiting element, and the voltage nonlinear element. What is claimed is: 1. An electromagnetic valve driving device, characterized in that a bypass circuit is connected in parallel with a signal input line consisting of a current limiting element having a saturation current value lower than that of the current limiting element. 2. The electromagnetic valve drive device according to claim 1, further comprising a smoothing circuit including a capacitor connected in parallel with the signal input line. 3. The electromagnetic valve drive device according to claim 1 or 2, wherein the current limiting element and another current limiting element are constant current diodes.