JPS54134279A - Temperature control device - Google Patents

Abstract

PURPOSE: To prevent an erroneous operation of a temperature control device by setting a heat sensitive thyristor at the same potential as one terminal of an AC power supply and triggering always in next positive half-cycle when a triode AC switch triggers in negative half-cycle to thereby trigger the switch with the potential phase of the power supply voltage.

CONSTITUTION: When the temperature of an article to be heated is low and a heat sensitive thyristor 4 is OFF, a capacitor 41 is charged at the polarity shown during the positive half-cycle period of an AC power supply 1. When the power supply phase tends to invert, the current of the capacitor 41 flows through the gate of an auxiliary thyristor 6 to trigger in zero phase of the power supply 1. A current will flow through the gate of a triode AC switch in a loop of the power supply 1 - heater 2 - terminal T₁ of triode AC switch 3 - gate - resistor 47 - auxiliary thyristor 6 - power supply 1 at this time to cause half-wave current to flow through the heater 2. The second capacitor 42 is charged at the polarity shown during the negative half- cycle period to cause the voltage to be inverted. Thus, a current will flow through the base of a transistor 49 during positive half-cycle period to thereby conduct the transistor 49.

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