JPS59180217A - Control circuit of current control type proportional valve - Google Patents

Abstract

PURPOSE:To obtain a cheap limitting device with high accuracy and simple constitution by a structure wherein a Zener diode to monitor the output voltage of a heat requiring load calculating circuit is arranged on the output terminal of the heat requiring load calculating circuit. CONSTITUTION:A Zener diode to monitor the output voltage signal of a heat requiring load calculating circuit 1 is arranged between the heat requiring load calculating circuit 1 and a voltage-current converter circuit 2 or concretely between the output voltage line of the heat requiring load calculating circuit 1 and the ground. In the above-mentioned constitution, the selection of a Zener diode, the Zener breakdown voltage of which is in accordance with the current capacity of a proportioning valve drive winding 3 to be employed, is enough and not any complicate circuit configuration is necessary. In spite of that, the sure action with a few variable factors is resulted. Even if the output voltage V0 of the heat requiring load calculating circuit 1 intends to increase beyond the Zener breakdown voltage, no voltage higher than the Zener breakdown voltage is applied to an operational amplifier OP, resulting in supplying no excess current to the proportioning valve drive winding 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is used to control fuel supply according to the current hot water temperature or heat demand load, etc., in order to always maintain the hot water supply temperature of a water heater at a predetermined set temperature. Regarding the control circuit for a current-controlled proportional valve, in particular: This relates to a current control type proportional valve Flj1011 circuit which has fF flow control force control type proportional 51゛overflow supply prevention +1 function.

The conventional control '11 circuit for this type of current-controlled proportional valve is basically as shown in Figure 1.

The output voltage generated by the heat demand negative operation circuit 1 is received at the positive phase input of the operational amplifier OP in the 1L voltage-'current conversion circuit 2,
The output is used to drive the switching transistor TR, and the proportional valve drive winding 3 is connected to the switching transistor TR.
- Connected in series with transistor TR.

The current flowing through the proportional valve drive winding 3 is converted into a voltage and detected by a current detection resistor R, and is fed back to the negative phase input of the operational amplifier OP. Therefore, the thermal quadrupling load calculation circuit 1
The switching I/transistor TR performs appropriate switching operations in response to the heavy pressures ir and i generated by the valve, and the IL flow required at that time flows through the proportional valve drive winding 3, not shown. The valve portion also controls the flow of fluid, such as fuel, according to the current If-1 at any given time.

However, in such control mechanism 1, the hot yellow demand r+:j F+i'! ; Voltage I1 emitted from J circuit 10
(When the current becomes large, there is a danger that an excessive current exceeding the maximum iM capacity current intake value will flow through the proportional drive winding 3.

Therefore, a number of countermeasures have been considered in the past. The second method is to set the power supply voltage Vc applied to the proportional jf drive winding 3 to a predetermined maximum voltage Vcma.
This is a method of limiting the number to X. In other words, this method is a method in which the maximum current is limited only by the sum of the resistance values of the proportional valve drive winding 3 (it4 and the backflow detection resistor R) when the switching transistor TR is turned on/on. This is called the absolute maximum pressure limitation method.

On the other hand, a slightly more complicated method as shown in FIG. 2 has also been adopted. This second method prepares a second power supply voltage Vr, and from this second power supply voltage
A reference voltage for limiting the maximum output voltage is created, and an active limiter circuit 4 is constructed using this reference voltage and a plurality of operational amplifiers. As a result, the supply to the proportional valve drive winding 3 is reduced to
The aim is to keep the +- to a minimum. This method can be called a limiter circuit.

However, the absolute maximum tonne pressure limitation method for the front beach is
1) By not using a special configuration for the control circuit 1)
)] It has the drawback that the accuracy of the current limiting function is low due to variations in the power supply voltage Vc and the resistance value of the proportional 51 drive winding 3 (=J). The later-named Norimink method has the accuracy of one level, but it has the drawbacks of being complicated and expensive.

In view of the above-mentioned conventional circumstances, the present invention has good accuracy and
At the same time, the present invention aims to provide a limiting device that is inexpensive and has a IIW 'l' configuration.

FIG. 3 shows a circuit configuration of a preferred embodiment of the present invention. Constructors that are circuitically or functionally equivalent to those in the conventional example are given the same line return as used in FIG. 1.2.

In the present invention, between the heat demand load calculation circuit 1 and the voltage-to-current conversion circuit 2, the output of the heat demand load calculation circuit 1, the output of the heat demand load calculation circuit I, is monitored between the heavy pressure line and the ground. The feature is that a Zener diode 5 is provided. The principle and operation of the water circuit will be explained below.

The output voltage of the heat required load calculation circuit 1 is Vo, and the current flowing through the proportional valve drive winding 3 is 13. switching transistor T
The base of R' is the quasi current b, the resistance 6fj of the current detection resistor H
Assuming that r is, the equation (1) holds true in a normal control mode.

Vo=r(+30lb)...(1)
Here, since generally 13)) Ib, the above equation (1) can be transformed as follows.

+3=Vo/r・−・(2) The maximum allowable current value to the proportional block f drive winding 3 is 13Iaax.

If so, if the maximum output voltage Vo (1 flomax) of the heat required load calculation circuit 1 satisfies the following equation, the It-like current limiting function for the proportional valve drive winding 3 can be achieved.

Vomax, = r-13max, ・
(3) The Zener TiO 1 Ki 5 used in the present invention is based on this knowledge, and it is sufficient that the Zener breakdown pressure corresponds to Vo II lax in the equation (3).

Conversely, according to the configuration of the present invention, it is only necessary to select the Zener diode 5 with the Zener breakdown pressure corresponding to the current capacity of the proportional valve drive winding 3 to be used, and no extraneous circuit configuration is required.
Not needed. Nevertheless, its operation is reliable and has few variables. Even if the output 7If pressure vO of the heat required load calculation circuit l attempts to increase beyond the Zener breakdown pressure,
Since no voltage higher than the Zener breakdown voltage is applied to the Qt calculation amplifier OP, excessive current is not supplied to the proportional valve drive winding 3 either.

To summarize the above, according to the present invention, it is possible to provide a highly reliable overcurrent prevention function to a current-controlled proportional valve with an extremely simple configuration using five control circuits. , the maximum allowable fi for the proportional valve 4IJ to be used.
Even if the ti value changes, there is no major change, and the thermal requirement load of 11ν, which causes the maximum allowable current value to flow; You can also obtain extremely high versatility by simply selecting I.5.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of the basic configuration of a conventional current 1j control force type proportional Jt control circuit, and Figure 21 is a current control force type proportional valve with a function to prevent excessive current to a current control force type proportional valve. FIG. 3 is a schematic diagram of a second conventional example of the f control circuit, and FIG. 3 is a schematic diagram of a preferred embodiment of the present invention. In the figure, l is a thermal demand load calculation circuit, 2 is a voltage-'current conversion circuit, 3 is a proportional valve drive winding, 4 is a limiter circuit, 5 is a Zener diode, TR is a switching transistor, O
P is a 6:I amplifier, and R is a current detection resistor.

Claims (1)

[Claims] It has a heat request load calculation circuit and a voltage-to-current conversion circuit, and has a heat demand j applied to the voltage input terminal of the voltage-current conversion circuit. In the control circuit of the current control type proportional valve, which flows through the drive winding of the current control force type proportional valve, -1 - the output voltage value of the heat storage request load calculation circuit is applied to the output terminal of the heat storage request load calculation circuit. A control circuit for a current-controlled proportional valve, characterized in that it is equipped with a zener diode for monitoring.