STEP-DOWN CIRCUIT FOR UTILITY POWER SUPPLY

摘要

PURPOSE: A step-down circuit for an utility power supply is provided to drop the utility power supply by implementing a simple circuit using an element characteristic without a transformer. CONSTITUTION: A triac(T) performs a switching operation at a zero volt point when an AC voltage of 220V is input. A diac(D) is connected with a gate of the triac(T) to trigger the triac. A variable resistor(VR) and a constant resistor(R2) are connected with the diac(D) and one terminal of the triac(T) to detect the zero volt point. A capacitor(C) is connected with the diac(D) and the other terminal of the triac(T). A varistor(V) is connected with the capacitor(C) in parallel to compensate the temperature of current input to the diac(D). A resistor(R1) is connected to an output(Vout) in parallel to prevent the overcurrent phenomenon of current applied to a load.