Philips Electronics North America Corporation

Patrick E Smeets

Naveed Majid

Jerzy Janczak

A resonant mode power supply includes a D.C. voltage source and switching elements for alternatively connecting an oscillating circuit, including a primary winding of a transformer, to the D.C. voltage source and to ground. A first secondary winding supplies the main output voltage of the power supply and a second secondary winding provides a control output voltage. An opto-coupler is included and has a light emitter connected to the second secondary winding, and a light sensor connected to a controller for controlling the switching of the switching elements, wherein the higher the frequency of the switching, the lower the power being supplied by the power supply. Burst mode stand-by is started by the first secondary winding being shunted to the second secondary winding causing the light emitter to emit a maximum amount of light. The controller increases the switching frequency until it exceeds a predetermined maximum frequency. The controller then stops the switching of the switching elements until the voltage across the light emitter falls below a predetermined value, and the controller then re-starts the switching.

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Geldrop, Netherlands

Patrick E Smeets