110 Vac/200 VAC Detector Switch
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
A technique is described whereby alternating current input voltages ranging from 90 volts to 270 volts are detected through the use of a detector circuit, incorporated into a power supply to detect the specific range of the input power. By utilizing this circuit, the need for separate 110 VAC and 220 VAC power supplies is eliminated. When the input voltage 10 is applied, as shown in the drawing, the voltage at capacitors 11 and 12 is sampled by one of the secondary windings of transformer 13 as transistors Q1 and Q2 are alternately turned on. The voltage at the secondary of transformer 13 is related to the capacitor voltage by the turns ratio of transformer 13. The pulse train voltage is half-wave rectified and filtered at 14 and 15.