JPH03121385A - Solenoid valve driving circuit - Google Patents

Abstract

PURPOSE:To increase the speed of switching response of a semiconductor power switching element and to reduce heating loss to the utmost by providing a short-circuit for bypassing between both ends of a non-linear element on detecting that an electric current flows through a control input terminal of a semiconductor switching element. CONSTITUTION:When a switching command signal is given from the outside to cause a non-linear element 8 of an input circuit to conduct and the impedance is lowered, an electric current starts flow through the control input terminal of a semiconductor switching element 6. Simultaneously, the current at the control input terminal is feedbacked and the non-linear element 8 is bypassed by a short circuit (photo coupler) 20 to suddenly increase the control current given from the input circuit to the control input terminal of the semiconductor switching element 6. Thus, at the time of switching operation when the semiconductor switching element 6 is ON, it is passed through a proportional area at high speed and immediately transferred to the conducting condition.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a drive circuit for an electromagnetic switching valve used in hydraulic equipment, etc., and in particular to a semiconductor switching element that controls energization/deenergization of a solenoid using a microcurrent control signal. This relates to the prevention of abnormal heat generation.

[Prior technology] In order to prevent the influence of electromagnetic noise generated when turning on and off the solenoid of an electromagnetic switching valve from affecting signal lines and external equipment, a micro-current signal operation solenoid is used to control the operation of the solenoid using a micro-current. A valve is disclosed, for example, in Japanese Patent Application Laid-Open No. 62-49085.

FIG. 4 is a circuit diagram showing a conventional drive circuit that energizes and deenergizes a solenoid of an electromagnetic valve using a minute current control signal. As shown in the figure, a solenoid 4 of a solenoid valve is connected to one terminal 1 of a pair of power supply terminals 1.2 connected to an external DC excitation power source 3.
is connected to the solenoid 4, and a collector-emitter output circuit of a power transistor 5 is connected in series to the solenoid 4. An input circuit that provides a switching control signal to the power transistor 5 has a photocoupler 6 consisting of a light emitting diode (hereinafter referred to as LED) 6a and a light receiving phototransistor 6b. The LED 6a is connected to a signal input terminal 9.10 via a constant current diode 7 and a Zener diode 8, which are current limiting elements, and a phototransistor 6.
The collector of b is connected to the power supply line through a resistor 11, and the emitter is connected to the base of the power transistor 5 via a base resistor 19. 12 is a constant voltage diode, and 13 is a smoothing capacitor. The resistor 11, the constant voltage diode 12, and the smoothing capacitor 13 smooth the non-smooth DC output of the external DC excitation power source 3 and supply it to the phototransistor 6b.

External control signal means 15 is connected to the signal input terminal 10 of the input circuit.
A constant current diode 16 is connected between the signal input terminals 9 and 10 to prevent leakage current when the input transistor 14 is turned off. A signal input power supply 17 is connected between the emitter of the transistor 14 and the signal input terminal 9. In addition, 18 is solenoid 4
This is a surge absorption element connected between both terminals of the .

In the drive circuit configured as described above, when a pulsed external human input signal having a finite time change in rise and fall is input from the external control signal means 15 to the base of the input end transistor 14, the rise First, the input current of 11.4
begins to flow, but the input terminal 11N increases over time as shown in the input terminal waveform diagram of FIG. 5(a).

As this input current 11N increases, the signal input terminal 9°10
However, until the voltage V reaches the Zener voltage ■2 of the Zener diode 8, the current I flowing through the constant current diode 16 is equal to I and one input terminal r+s
flows only through the constant current diode 16. When voltage ■1 reaches Zener voltage V2 due to this increase in current 11,
The Zener diode 8 breaks down, current 2 flows through the LED 6a of the photocoupler 6, and the phototransistor 6b starts to turn on. In this state, the input terminal II
N is I IN=I I + I2.

On the other hand, the input current IIN further increases and the current 1. flowing through the constant current diode 16 increases. When enters the constant current characteristic region, the current ■,
becomes a constant current Its as shown in Fig. 6, and thereafter L
The current 2 flowing through the ED6a increases as the input current IIN increases. When the current I2 flowing through the LED 6a gradually increases, the current flowing through the phototransistor 6b
3 will be applied to the base of the power transistor 5 in increasing amounts. As the input current I IN increases, the current ■3 increases and passes from the off region (blocking region) of the power transistor 5 to the non-saturated proportional region ΔI and reaches the on region (conduction region). conducts. Due to this conduction of the power transistor 5, a current flows from the DC excitation power source 3 to the solenoid 4 through the excitation 61i', thereby energizing the solenoid 4.

After energizing the solenoid 4, the input current 118 is a constant current determined by the characteristics of the constant current diode 7 connected in series with the LED 6a! By 2s, I IN= T Is+ I 2s
This results in a state of saturation.

In this state, when the external input signal input from the external control signal means 15 is cut off in order to turn off the solenoid 4, this is done within a finite time during which the external input signal also falls. Therefore, in this case, as the input terminal IIN decreases as the external input signal falls, the current I2 flowing through the LED 6a gradually decreases, and the current I3 flowing through the phototransistor 5 also gradually decreases. And the current ■
3 passes through the proportional region of the power transistor 5 and reaches the off region, the power transistor 5 cuts off and deenergizes the solenoid 4.

In this way, one line is connected to the signal line separated from the excitation power supply line.
The solenoid 4 is energized and deenergized by passing a minute current of about 0 to 20 mA, and the electromagnetic noise 129 generated when the solenoid 4 is energized and deenergized relative to the signal line is reduced.

[Problems to be Solved by the Invention] In the conventional electromagnetic valve drive circuit, the external human input signal inputted from the external control signal means 15 changes over a finite period of time, and the input terminal IIN changes as shown in FIG. 5(a). In the case where the power increases and decreases over a finite time as shown in , there is a finite time during which the power transistor 5 operates in the proportional region Δ■ while switching. Therefore, the power transistor 5
The operating time in the proportional region △I becomes longer, and as shown in Fig. 5 (
As shown in the waveform diagram showing the heat loss characteristics in b), the heat generation amount W of the power transistor 5 increases in the proportional region △■, and when the solenoid 4 is energized and deenergized again, the power transistor 5 is thermally destroyed. There was a risk of being exposed.

Also, if there is a noise component in the external human input signal, the input terminal I
1.4 fluctuates in the proportional region △I as shown in Figure 7(a), so as the input current 11N fluctuates, power 1 to transistor 5 turn on and off as shown in Figure 7(b). Repeatedly, depending on the case, an oscillation state may occur, causing abnormal heat generation, and there is a risk that the power transistor 5 may be thermally destroyed.

This invention has been made to solve these shortcomings, and it is possible to speed up the switching response of a semiconductor power switching element that energizes and deenergizes a solenoid, regardless of the switching response speed of an external human input signal. The object of the present invention is to obtain an electromagnetic valve drive circuit that can reduce heat loss as much as possible and stably use a semiconductor power switching element.

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the solenoid valve drive circuit of the present invention includes a semiconductor switching element connected in series with a solenoid between a pair of power supply terminals, and a predetermined voltage value. An input circuit that provides a switching control signal to the control input terminal of the semiconductor switching element via a non-linear element that becomes conductive when receiving an applied voltage of
The apparatus further includes a short circuit that detects when a current flows through the control input terminal of the semiconductor switching element and bypasses the current between both ends of the nonlinear element.

In this case, it is preferable that the short circuit is constituted by a photocoupler consisting of a light emitting diode connected in series to the control input terminal of the semiconductor switching element and a phototransistor connected in parallel to the non-linear element.

[Function] In the present invention, when a switching command signal is applied from the outside to cause the non-linear element of the input circuit to conduct and become low impedance, a current is applied to the control input terminal of the semiconductor switching element via the non-linear element. At the same time that the current at the control input terminal starts to flow, the nonlinear element is bypassed by a short circuit, and the control current applied from the input circuit to the control input terminal of the semiconductor switching element is rapidly increased. During the switching operation when the switching element is turned on, the proportional region is passed through at high speed, and the switching element immediately changes to a conductive state.

Also, once the switching command signal from the outside is cut off,
When the voltage across the nonlinear element of the input circuit becomes less than a predetermined voltage value, the decrease in current at the control input terminal of the semiconductor switching element is fed back to open the nonlinear element's bypass due to the short circuit, and the control input terminal By rapidly reducing the applied control current, the semiconductor switching element passes through the proportional region at high speed during the off-time switching operation, and immediately transitions to the cutoff region.

In this case, if a photocoupler is used as the short circuit,
The signal circuit and solenoid circuit can be electrically isolated.

[Embodiment] FIG. 1 is a circuit diagram showing an embodiment of the present invention. In the figure, 1 to 19 are exactly the same as the conventional example shown in FIG. 4. A photo coupler 20 is connected to the Zener diode 8, which serves as the non-linear element of the input circuit that provides a switching control signal to the power transistor 5, and forms a short-circuited path between both ends thereof. That is, the input end LED 20a of the odocoupler 20 is connected in series with the phototransistor 6b which is the output element of the photocoupler 6 of the input circuit, and the phototransistor 20b on the output side of the photocoupler 20 is connected as the nonlinear element of the input circuit. is connected in parallel between both ends of the Zener diode 8 to form the aforementioned bypass.

In the drive circuit configured as described above, when an external human input signal that gradually increases over time is applied to the input side transistor 14 from the external control input means 15, the collector of the input side transistor 14 passes through the constant current diode 16.
At the input terminal between the emitters, steam IIN begins to flow, as shown in Figure 2 (
As shown in the input current waveform diagram a), the input terminal 11N gradually increases.

This input terminal 11N is further increased, and the signal input terminal 9.
When the voltage v1 between 10 and 10 reaches the Zener voltage V2 of the Zener diode 8, the Zener diode 8 breaks down and becomes low impedance at point A in FIG. The input current IIN becomes I, N=I, +I2, and the phototransistor 6b of the photocoupler 6 starts to conduct exclusively. This phototransistor 6b begins to conduct, and the current flow begins. When the current begins to flow, the LED 20a of the photocoupler 20 starts emitting light, and the phototransistor 20b connected in parallel with the Zener diode 8 starts to conduct.

When this phototransistor 20b begins to conduct, the voltage generated across the Zener diode 8 begins to decrease. Furthermore, when the input current 2 increases, the current I2 flowing through the LED 6a increases, and the current I3 flowing through the transistor 6b, that is, the LED 20a increases, the phototransistor 20b of the photocoupler 20 becomes completely conductive, and the signal The voltage V between the input terminals 9 and 10 is directly applied to the LED 6a of the photocoupler 6 and the constant current diode 7, and the current I2 increases rapidly. As a result, input terminal 11
N increases rapidly and reaches point B in FIG. 2(a).

Due to this rapid increase in the input terminal 1N, that is, the current 2, the phototransistor 6b rapidly becomes conductive, and the power transistor 5 quickly passes through the proportional region and transitions to the conductive region, turning the power transistor 5 on immediately. In this way, since the power transistor 5 rapidly passes through the proportional region, it is possible to reduce the total heat generation iVJ in the proportional region of the power transistor 5, as shown in the waveform diagram showing heat generation loss characteristics in FIG. 2(b). can.

After the power transistor 5 becomes conductive and the solenoid 4 is energized in this way, when the external human power signal from the external control human power means 5 is turned off, the voltage between the input terminals 9 and 10 starts to decrease as the input terminal 11N starts decreasing. V gradually decreases.

As the voltage (1) decreases, the current (2) flowing to the LED 6a through the phototransistor 20b bypassing the Zener diode 8 begins to decrease, and the phototransistor 6b begins to turn off. At this time, since the Zener diode 8 is short-circuited by the phototransistor 20b, the current I2 flows directly to the LED 6a, and the current I2 flows directly to the LED 6a. The Zener diode 8 remains on until the point, that is, the voltage (2) becomes equal to or less than the Zener voltage Vz. When the input current IIN decreases and reaches the 0 point, the phototransistor 20b of the photocoupler 20 is cut off due to the decrease in the current 3 flowing through the phototransistor 6b.

When the phototransistor 20b is cut off, the current 2 flowing through the LED 6a is immediately cut off by the Zener diode 8, and the input terminal IIN rapidly changes from point 0 to point D. On the other hand, as the current I2 is cut off, the photocoupler 6 is rapidly turned off, and the power transistor 5 is also immediately completely turned off. Therefore, even when the solenoid 4 is cut off, the power transistor 5 quickly passes through the proportional region, and the heat generation fiw can be reduced as shown in FIG. 2(b).

In addition, hysteresis can be given to the input terminal value IIN0N for the power transistor 5 to be in the conductive state and the input terminal value 11NOF for the power transistor 5 to be in the cutoff state in the relationship of IIN0N>IIN0F, as shown in FIG. ) Even if there are noise components in the input current, the power transistor 5 can be stably switched without being affected by these noise components as shown in FIG. 7(C).

[Effects of the Invention] As explained above, in the present invention, the non-linear element of the input circuit becomes conductive in response to a switching command signal from the outside.
When a control current starts to flow through the non-linear element and a current starts to flow to the control input terminal of the semiconductor switching element, the current at the control input terminal is fed back to close the short circuit, and the input circuit is connected to the control input terminal of the semiconductor switching element. By rapidly increasing the applied control current, the current at the control input terminal can be rapidly increased, and the semiconductor switching element can be brought into conduction immediately.

Furthermore, after the switching command signal from the outside decreases, the control current of the input circuit decreases, and the voltage across the nonlinear element becomes below a certain level, the decrease in current at the control input terminal of the semiconductor switching element is fed back to short circuit. By opening the circuit and rapidly reducing the control current applied to the control input terminal to rapidly transition the semiconductor switching element to the cut-off state, the operation of the semiconductor switching element can have hysteresis characteristics, and the external input signal Since the semiconductor switching element rapidly passes through the proportional region regardless of temporal changes, heat loss in the proportional region can be significantly reduced.

In addition, because the semiconductor switching element quickly passes through the proportional region and has hysteresis characteristics, it can be turned on repeatedly even if the external human input signal contains noise components.
This prevents oscillation due to off-state and allows the semiconductor switching element to operate without abnormal heat generation due to oscillation.
Semiconductor switching elements can be used stably.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing an embodiment of this invention, Figure 2 (a)
(b) is a waveform diagram showing the operation of the above embodiment, Fig. 3 is an output characteristic diagram of the power transistor of the above embodiment, Fig. 4 is a circuit diagram showing the conventional example, and Figs. 5 (a) and (b) are Waveform diagrams showing the operation of the conventional example, Figure 6 is a diagram of the operating characteristics of a constant current diode, Figures 7 (a) and (b) are waveform diagrams showing the human output characteristics of the conventional example, and Figure 7 (C) is the main FIG. 3 is a waveform diagram showing human output characteristics of an embodiment of the invention. 4... Solenoid, 5... Power transistor, 6
．． 20...Photo coupler, 7.16... Constant current diode, 8... Zener diode. Figure 1

Claims (1)

[Claims] 1. A semiconductor switching element connected in series with a solenoid between a pair of power supply terminals, and a non-linear element that becomes conductive when an applied voltage of a predetermined voltage value or higher is applied to the semiconductor switching element. In a solenoid valve drive circuit equipped with an input circuit that applies a switching control signal to a control input terminal of a switching element, when a current flows through the control input terminal of the semiconductor switching element, this is detected and the current flows between both terminals of the nonlinear element. A solenoid valve drive circuit further comprising a short circuit that bypasses the. 2. The electromagnetic valve drive circuit according to claim 1, wherein the short circuit includes a photocoupler.