Sgs-thomson Microelectronics S.a.

Jean-Claude Bielli

Thierry Castagnet

A rectifier power supply automatically adjusts to operate over either of two separate ranges of AC line voltages by reconfiguring filter capacitors so as to charge the capacitor serially when operated over the higher range of voltages and to charge the capacitors separately over each half cycle when operated over the lower voltage range. A triac device, used to control charging of the capacitors, is selectively activated only during a small portion of each half cycle to minimize power consumption. The device includes a bridge rectifier circuit receiving an AC line voltage and supplying pulsating DC to the serially connected two filter capacitors. The triac is used as a switch and is connected between one input terminal of the diode bridge and a node point between the two capacitors. An AC line voltage range detector and triac control circuit responsive to the range detector causes the triac to conduct when the AC line voltage is detected within the lower range. In particular, the control circuit causes the triac to conduct after a first time interval after a zero crossing of the AC line voltage and to cease conducting after a second time interval.

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Saint Martin d'Heres, France

Jean-Claude Bielli