| 摘要 |
PURPOSE:To suppress a current in the operating part of a phase control circuit to the standardized value or less without reducing the phase control range of a TRIAC by a method wherein a discharge current of capacitor for timing is detected, and the necessary current for a gate of TRIAC is supplied from a different electric power source. CONSTITUTION:The operating part 24 to control the ON angle of TRIAC and the timing capacitor 22 are connected to both the ends of the TRIAC 13, and load of the TRIAC 13 is controled by controlling the gate of the TRIAC 13 through a bi-directionally switching element 14. A series circuit of a resistor 23 and a capacitor 21 is provided, and the node thereof is connected to transistors 17, 18 to detect the discharge current of the capacitor 22. Accordingly by making the gate current of the TRIAC 13 to be supplied by the discharge current of the capacitor 21, and making the capacitor 22 as to supply only base currents of the transistors 17, 18, the current in the operating part 24 to be touched with a man's hand can be suppressed to the standardized value or less. |
