Zero trigger integrated circuit temperature control circuit one b

Zero-trigger integrated circuits such as KJ008 type, KC08 type, etc. are monolithic integrated circuits used for voltage zero-crossing triggering or current zero-crossing triggering of bidirectional thyristors (or two unidirectional thyristors connected in reverse parallel
). They can directly trigger 50A bidirectional thyristors. Such as external
power expansion. Can trigger bidirectional thyristors with a capacity of 200A or more.
    The circuit is shown in Figure 11-84 (a). It uses a voltage zero trigger circuit of KJ008 or KC08 integrated circuit
to achieve automatic temperature control. Figure 11-84(b) is the internal circuit of this series of integrated circuits.
    The integrated circuit
cooperates with the external resistor R3, diode VD and capacitor cl to form a 12~ 14V DC voltage between pin 14 and pin 7 for use by the chip. The grid voltage is added between pin 1 and pin 14 through the resistor Rz to detect
the zero crossing point of the power supply voltage. Pin 4, pin 11, and pin 12 are short-circuited to each other, and a fixed potential is obtained at pin 4. The potential of pin 2
depends on the thermistor R with negative temperature coefficient. Voltage divider with potentiometer RP. As the temperature increases, R. The resistance decreases and the potential of pin 2
increases. When the temperature reaches the set value (can be changed by adjusting RP), the potential of pin 2 is higher than the potential of pin 4, and the zero-
crossing trigger pulse disappears; conversely, when the temperature drops below the set value, the potential of pin 2 of A is lower than At the potential of pin 4, the bidirectional thyristor
V gets a zero trigger pulse and turns on, turning on the electric heater EH for heating. When the temperature rises and reaches the set value, V is closed and
the above process is repeated, thereby keeping the controlled temperature near the set value.