AUTOMATIC VOLTAGE SWITCHING DEVICE

摘要

PURPOSE:To connect an equipment to a plural kinds of rated AC power sources specified in the face plate without any adjustment and to eliminate the damage of the equipment due to power source mismatching by providing an automatic switching circuit between a load and the output side of a full-wave rectifying circuit provided on the secondary side of a power source transformer. CONSTITUTION:The primary side PR of the power source transformer PTR is connected to a power source plug PC and a center tap CT is provided on the secondary side SD of this transformer PTR to output voltages V1 and V2 on the secondary side. The voltage V1+V2 is rectified by diodes D1-D4 on full-wave basis to apply nearly equal voltages to smoothing capacitors C1 and C2. This reference potential GND is connected to one terminal of the load L and a potential VL is connected to one terminal of the automatic voltage switching circuit 6; and the connection point A between the circuit 6 and load L is connected to a potential VCT through a diode D5. The Zener diode ZD and transistor TR1 of this circuit 6 compare the potential VL with a reference supply voltage and TR2 and TR3 select a rated DC voltage on the basis of the comparison result to supply it to the load.