JPS5854283A - Driving circuit for proportional valve - Google Patents

Abstract

PURPOSE:To reduce a loss of a collector of a transistor which drives a proportional valve and to restrain a rise in internal temperature of a device by adopting a switching system for a driving circuit wherein interrupted current is supplied to a smoothing circuit which consists of a choke coil and a capacitor. CONSTITUTION:A comparator 21 which consists of an arithmetic amplifier receives a control voltage VA at the noninverted input terminal and a terminal voltage VB of a resistance 23 which detects a valve current flowing through a solenoid coil 22 of a proportional valve at the inverted input terminal, inverting the output dependently on the comparative relationship between the intensities of both the voltages VA and VB to turn on or off a transistor 24. A transistor 26 is switched on and off in company with the on and off actions of the transistor 24 and supplies a smoothing circuit which consists of a choke coil 27 and a capacitor 28 with a current which is controlled on or off.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a drive circuit for arbitrarily adjusting and setting the valve opening of a proportional valve.

A proportional valve changes its valve opening degree in an analog manner according to the valve current flowing through the solenoid coil. For example, it adjusts the flow of fluid such as gas supplied to combustion equipment in an analog manner, and controls the amount of combustion. It is used to.

As an example of 141 using this type of proportional valve, a gas instant wA that continuously controls the amount of combustion gas with a proportional valve
The basic structure of the boiler is shown in Figure 1. Briefly explaining the operation of this gas instantaneous water heater 1, when you open the faucet to dispense hot water, the flow switch 5 installed at the water intake of the heat exchanger 4 detects running water, and the detection signal is sent to the combustion control@
112, the combustion control device @2 opens the main valve 6 provided in the gas pipe line and directs the gas to the gas governor 7.
゜Supplied to the burner 8 via the proportional valve 3. At the same time that gas is started to be supplied to the burner 8, the ignition transformer 9 is driven, the ignition electrode 10 sparks, and the burner 8 is ignited. The rise in wI temperature after ignition is detected by the thermistor 11 provided at the output low of the heat exchanger 4. From this detection signal, the setting of 81 degrees in the combustion control device 2, the detection signal of the flow switch 5, etc., a control voltage of a predetermined level corresponding to the temperature difference between [121 and the set temperature is created, and this control voltage will be described later. When the input is input to the drive circuit, the proportional valve 3 is supplied with a predetermined valve current according to the level of the control voltage by this drive circuit, and the valve opening changes in an analog manner to keep the water temperature constant. The amount of combustion in burner 8 is controlled.

An ignition detection rod 12 is provided to detect the ignition of the burner 8, and an alarm 13 is used to notify the outside when an ignition error occurs.

FIG. 3 shows a drive circuit for controlling the proportional valve 3.

This drive circuit uses a differential amplifier 16 to amplify the difference between the control voltage and the terminal voltage of a resistor 15 that detects the valve current flowing through the solenoid coil 14, and uses its output to adjust the base current of the transistor 17. As a result, solenoid coil 1
4i) the valve current is controlled according to the level of the control voltage;
The opening degree of the proportional valve changes in an analog manner.

However, in such a circuit configuration of the drive circuit, current always flows through the transistor 17, so its collector loss is large, and a heat sink is usually required. Therefore, when designing a printed circuit board, there are restrictions such as the inability to place electronic components with low heat resistance near the transistors and their heat sinks. In addition, when such a printed circuit board is mounted on a device, it causes an increase in m* inside the device, which has a negative impact on other electronic components.This requires special heat dissipation measures, and this is the cause of cost increase. This also made it difficult to downsize the device.

This invention was made in view of these conventional problems, and by using a switching system for the drive circuit, it drastically reduces the collector loss of the transistor that drives the proportional valve, and also improves the efficiency when mounting the device. The purpose of the present invention is to provide a drive circuit that can suppress an increase in internal heating, eliminate the need for a special heat radiator, and contribute to downsizing of the device.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

In FIG. 3, a comparator 21 consisting of a deductive amplifier
The control voltage VA mentioned above is input to the non-inverting input terminal, and the terminal voltage VB of the resistor 23 that detects the valve current flowing through the solenoid coil 22 of the proportional valve is input to the one-inverting input terminal, and the magnitudes of both voltages VA and VB are input. Based on the relationship, the output is inverted and the transistor 24 is turned on and off. The collector of the transistor 24 is connected to the base of the transistor 26 via the resistor 25, and as the transistor 24 turns ON and OFF, the transistor 26 turns on and off.
ON・0FFL/, choke coil 27 and capacitor 2
A current that is ON/OFF controlled is supplied to a smoothing circuit consisting of 8. In addition, the diode 29 is connected to the transistor 26 when the transistor 26 is
When turned off, the current sustaining characteristic of the choke coil 27 is maintained.

Now, when the control voltage VA is larger than the terminal voltage VB, the output of the comparator 21 becomes a high level, so the transistors 24 and 26 are sequentially ONL, current flows to the choke coil 27, the capacitor 2B is charged, and the solenoid A valve current flows through the coil 22. As a result, as the proportional valve slowly increases its opening, the terminal voltage VB rises towards the control voltage VA. When the valve current increases and the terminal voltage VB becomes larger than the control voltage VA, the comparator 21 operates in reverse and outputs a low level, and as a result, the transistors 24 and 26 are sequentially turned off, and the current supply to the choke coil 27 is cut off. dripping

At this time, the current due to the current sustaining characteristic of the inductance of the choke coil 7 flows to the solenoid coil 22. Resistance 23. While being consumed in the closed circuit formed by the diode 29, the discharge current of the capacitor 28 flows through the solenoid coil 22. Flowing through resistor 23, the valve current decreases for a while. As a result, the proportional valve slowly decreases its opening and the terminal voltage VB falls towards the control voltage. And terminal electric I
When +VB becomes lower than the control voltage VA, the comparator 21 performs an inversion operation and returns to the above-described operation.

As a result of repeating the above operations, the valve cylinder flow becomes a waveform containing ripples as shown in FIG. Determined by time constant. The above-mentioned increase or decrease in the valve opening of the proportional valve is a phenomenon in this ripple portion, but since the switching frequency of the transistor 26 is sufficiently higher than the response limit frequency of the proportional valve, the increase or decrease in the valve opening in this ripple portion is a phenomenon. It can be almost ignored. Therefore, the valve cylinder flow is regarded as an averaged constant current, as shown by the broken line in the figure, and the proportional valve maintains a predetermined valve opening determined by the control voltage VA.

The valve opening degree of the proportional valve is changed by changing the magnitude of the control voltage VA, but as mentioned above, since the valve cylinder flow can be regarded as a substantially constant current, the valve cylinder flow changes as the control voltage VA changes. The flow changes in an analog manner, and the opening of the proportional valve can be changed smoothly as before.

Note that when the transistor 26 is reversed from OFF to ON, the diode 29 recovers from ON to OFF, but within the recovery time of the diode 29, the diode 29! i
In order to prevent this, it is preferable to use a high-speed diode 29, since this will cause the current to flow and deteriorate the efficiency of the power supply. Furthermore.

A comparator circuit is usually provided with a hysteresis circuit for the purpose of stabilizing its operation, but in this invention, this is not provided, and the circuit obtains hysteresis characteristics by utilizing the input/output response delay of the operational amplifier itself as the comparator 21. We are trying to simplify the process.

As explained in detail above, since the proportional valve drive circuit according to the present invention uses a switching method, the collector loss of the transistor that drives the proportional valve is only the loss during switching, and this loss is small compared to the conventional one. About 10
It can be reduced by about 1/2.

As a result, constraints on printed circuit board design are significantly relaxed, and an increase in internal temperature of the device during device mounting is suppressed.

Therefore, the problem of heat resistance of the electronic part can be solved, the lifespan and reliability can be expected to be improved, and the device can be made smaller.

Furthermore, since the hysteresis characteristic during switching utilizes the response delay of the operational amplifier itself, it is possible to simplify the circuit and achieve the effect of reducing costs.

[Brief explanation of the drawing]

Figure 1 shows an example of the application of the proportional valve! Combustion! Block diagram of the device,
Fig. 2 is a circuit diagram showing a conventional proportional valve drive circuit, Fig. 3 is a circuit diagram showing a proportional valve drive circuit according to the present invention, and Fig. 4 is a circuit diagram showing a proportional valve drive circuit according to the present invention.
The figure is a schematic diagram illustrating the state of the valve cylinder flow of the solenoid coil. 3... Proportional valve 21... Comparator 22... Solenoid coil 23... Valve cylinder flow detection resistor 26... Transistor 27... ... Choke coil 28 ... Capacitor 29 ... Diode Patent applicant Tateishi Electric Co., Ltd. Figure 1 Figure 2 υ1 Figure 3 Figure 4

Claims (1)

[Claims] (1) A drive circuit that controls the valve current flowing through the solenoid coil in response to the control voltage and changes the valve opening of the proportional valve in an analog manner, so that the control voltage is applied to one input terminal and the other input terminal is applied to the drive circuit. A comparator to which the terminal voltage of the resistor that detects the valve current is input, a transistor that is driven by the output of the comparator and outputs a current that is ON-OFF controlled, and a transistor that smooths the output current of the transistor and controls the solenoid. A smoothing circuit that applies voltage to the series circuit of the coil and the valve current detection resistor, and a smoothing circuit that applies the voltage to the series circuit of the coil and the valve current detection resistor, and the transistor that is 0FF
L, when the series circuit constitutes a closed circuit with the choke coil of the smoothing circuit, and includes a diode for maintaining the valve current flowing through the solenoid coil, the valve current equivalently corresponds to the control voltage. A drive circuit for a proportional valve, characterized in that an analog current of a magnitude is generated.