JPS6045444B2 - temperature control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature control circuit using a heat-sensitive thyristor driven by a DC power source.

FIG. 1 shows an example of a temperature control circuit using a heat-sensitive thyristor driven by a conventional DC power supply.

In the figure, 1 is a DC power supply, 2 is a relay coil serving as a load, 3 is a rectifier diode for flywheeling that is connected in parallel to the relay coil 2 in the opposite direction to the power supply 1, and 4 is the power supply. Relay coil 2 between both ends of 1
5 is a noise prevention capacitor connected between the gate and anode of the heat sensitive thyristor 4, and 6 is connected in parallel to the capacitor 5, and is connected to the switch of the heat sensitive thyristor 4. These are variable resistors that set the temperature, and these constitute a temperature control circuit.

Note that 21 is an AC power source, 22 is a relay contact driven by the relay coil 2, and 23 is a load such as a heater. Next, the operation will be explained.

First, the switch temperature of the heat-sensitive thyristor 4 is set by the variable resistor 6.
and the applied voltage of the DC power supply 1 in advance. For example, when the temperature of the detected part, such as the vicinity of the heater 23, is lower than the set switch temperature of the heat-sensitive thyristor 4, the heat-sensitive thyristor 4, which is thermally coupled to the detected part, naturally turns off. To show, relay coil 2
No power is supplied to the Therefore, if the relay contact 22 is normally closed at this time, the heater 23 will heat up continuously and increase the temperature of the detected part. Next, when the temperature of the detected part rises and becomes equal to or higher than the switch temperature of the thermal thyristor 4, the thermal thyristor 4 turns on and supplies power to the relay coil 2. Therefore, contrary to the above, the relay contact 22 is opened, and the heating of the heater 23 can be stopped.
However, since the heat-sensitive thyristor 4 has a holding function, once it indicates an on state, it maintains that state and supplies power to the relay coil 2 even if the temperature of the detected part drops to below the switch temperature. It has the disadvantage of continuing to do so.

In other words, the circuit in Figure 1 works only the first time, but
The drawback was that it was not suitable for repeated temperature control. This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and includes a recovery control circuit that periodically applies a reverse bias voltage to the heat-sensitive thyristor when the heat-sensitive thyristor is turned on. Accordingly, it is an object of the present invention to provide a temperature control circuit that can return a heat-sensitive thyristor to an OFF state when the temperature of a detected part becomes equal to or lower than the switch temperature.

FIG. 2 is a circuit diagram showing an embodiment of the present invention.

In the figure, the same reference numerals as in FIG. 1 indicate the same or corresponding parts, respectively.

7 is an NPN transistor connected between both ends of DC power supply 1 via relay coil 2; 9 is a diode connected in antiparallel between the base and emitter of transistor 7;
is a resistor connected between the base of the transistor 7 and the cathode of the heat-sensitive thyristor 4, 10 and 11 are resistors connected in series between both ends of the DC power supply 1 together with the heat-sensitive thyristor 4-, and 14 and 12 are the resistors connected to the DC power supply 1. A resistor is connected in series across both ends of the resistor and . A programmable union transistor (hereinafter abbreviated as PUT), 15 and 16 are resistors connected in series between the positive electrode of the DC power supply 1 and the collector of the transistor 7, and 13 is connected between the anode of the heat-sensitive thyristor 4 and the anode of PUTl2. Conde. It is Nsa.

Note that the gate terminal of PUTl2 is connected to the connection point between the resistor 15 and the resistor 16. Next, the operation of the circuit shown in FIG. 2 will be explained.

When the temperature of the heat-sensitive thyristor 4 is lower than the switch temperature, the heat-sensitive thyristor 4 is turned off, the transistor 7 is also turned off, and no power is supplied to the relay coil 2. Therefore, the relay contact 22 is closed and the heater 23 continues to be heated. Also, capacitor 1
No. 3 is not charged because the heat-sensitive thyristor 4 is in an off state. Therefore, PUTl2 does not oscillate. next,
When the temperature of the heat-sensitive thyristor 4 (same as the temperature of the detected part) becomes higher than the switch temperature, the heat-sensitive thyristor 4 is turned on, so a voltage is generated across the resistor 11, and the resistor 8
Since the base current flows through the transistor 7 through the transistor 7, the transistor 7 is turned on.

Therefore, power is supplied to the relay coil 2. Therefore, the relay contact 22 is opened, and power is no longer supplied to the heater 23. On the other hand, the gate of the P region 12 is connected to the resistor 16 and the transistor 7. Therefore, when the voltage of the capacitor 13 becomes equal to or higher than the gate voltage determined by the division ratio of the resistors 15 and 16, PUT12 turns on and starts so-called relaxation oscillation. A reverse bias is periodically applied to the heat-sensitive thyristor 4 due to the discharge current of However, when the temperature of the detected part becomes equal to or lower than the switch temperature, the heat-sensitive thyristor 4 automatically returns to the OFF state. By repeating the above-described operation, repeated temperature control can be realized.

Incidentally, since the oscillation of PUTl2 is not performed only when the heat-sensitive thyristor 4 is in the ON state, power consumption can be relatively small.

FIG. 3 is a circuit diagram showing another embodiment of the present invention, and the difference from FIG. 2 is that the relay coil 2 and diode 3 are
In addition to replacing the parallel connection body with the resistor 18, the heater 2
3 is connected between both ends of the DC power source 1 via a power transistor 17, and the base electrode of the power transistor 17 is connected to the connection point between the resistor 18 and the transistor 7.

With such a configuration, when the heat-sensitive thyristor 4 is off, the transistor 7 is off, and the transistor 1 is off.
7 is turned on, and power is supplied to the heater 23. On the other hand, when the heat-sensitive thyristor 4 is turned on, the transistor 7 is turned on and the transistor 17 is turned off, so that no power is supplied to the heater 23. Also, at this time, as in the case of FIG. 2, a reverse bias is periodically applied to the heat-sensitive thyristor 4, so when the temperature drops below the switch temperature, the heat-sensitive thyristor 4 returns to the on state, and the heater 2
Power is now supplied to 3. In the above embodiment, an n-gate type σ thermal thyristor 4 was used, but a P-gate type? It can also be configured using a thyristor. However, in this case, it goes without saying that the variable resistor 6 for setting the switch temperature and the noise prevention capacitor 5 are connected between the cathode and the gate. Also, around P
2, it can also be constructed using an oscillation element such as SUS, SBS, or DIAC.

As described above, according to the present invention, when the heat-sensitive thyristor becomes conductive, a reverse bias is periodically applied to the heat-sensitive thyristor, so that the temperature of the heat-sensitive thyristor falls below its switch temperature. A circuit in which the heat-sensitive thyristor can be returned to the on state and repeated temperature control can be obtained.
1 Brief Description of the Drawings Fig. 1 is a circuit diagram showing a conventional temperature control circuit, Fig. 2 is a circuit diagram showing one embodiment of the present invention, and Fig. 3 is a circuit diagram showing another embodiment of the present invention. It is.

Claims (1)

[Claims] 1. A heat-sensitive thyristor that is thermally coupled to the detected part and connected between both ends of a DC power supply and becomes conductive when a predetermined switch temperature is reached; A temperature control circuit comprising: a switching element for controlling power supply; and a return control circuit that periodically applies a reverse bias to the heat-sensitive thyristor when the heat-sensitive thyristor is conductive. 2. The temperature control circuit according to claim 1, wherein the switching element is connected in series with the load. 3. The temperature control circuit according to claim 1, wherein the switching element controls opening and closing of a switching means connected in series with the load. 4. The temperature control circuit according to any one of claims 1 to 3, wherein the return control circuit includes an oscillation element that oscillates when the heat-sensitive thyristor becomes conductive.