| 摘要 |
PURPOSE:To perform on-off control over a small or inductive load at a voltage zero-cross point stably in safety by using an oscillator which oscillates continuously in a half period after the voltage zero-cross point as a voltage zero-cross pulse generator. CONSTITUTION:When the temperature of a controlled system is lower than a set value, the temperature is detected by a detector 18 and sent to a control circuit 19. The circuit 19 opens a control terminal 2 for oscillation output after the next voltage zero-cross point by the signal. Consequently, the pulse oscillator 20 starts oscillating at the voltage zero-cross point and its oscillation output is sent to an electronic switch 16. The electronic switch 16 turns on securely almost at the voltage zero-cross point by a continuous pulse string which is sent subsequently even when a heater 17 is a small or inductive load and can not secure a hold current in the 1st pulse arrival. When the temperature of the controlled system is higher than the set value, on the other hand, the electronic switch 16 holds itself in the on state during the period because of its properties as a holding element and turns off at the next voltage zero-cross point. |
