| 摘要 |
PURPOSE:To prevent a titled circuit from malfunction also in case of the operation at high temperature by turning off a triac for controlling phase at the vicinity of a zerocross point of AC power voltage. CONSTITUTION:A breaking circuit CTa consisting of a volume VR in a voltage dividing circuit D and a two-way constant voltage element obtained by anti- parallel connecting Zener diodes ZD1, ZD2 is incorporated into a titled circuit. The breaking circuit CTa turns the voltage applied to a capacitor, divided voltage VD, to ''0'' at a point close to the zerocross point of AC power voltage and discharges the charge of the capacitor C through resistances R3-R5 and the gate of a triac TR1. At the initial time of the succeeding half cycle, gate current to the triac is interrupted and, at high temperature operation, a trigger element is not easily turned off and the triac TR1 is easily turned on, performing phase control precisely. |
