Apple Inc.
Adaptive Wakeup Time Control In Burst Mode Of A Primary Side Regulated Flyback Converter

Abstract:

A flyback converter can include an auxiliary winding magnetically coupled to the secondary (output) for sensing a reflected output voltage. A controller can operate a power switch of the flyback converter in a burst mode to deliver a number of pulses, causing the output voltage to reach a threshold, and thereafter suspend switching for a predetermined time period before delivering a further number of pulses. The delivered number of pulses can be counted, and, responsive to a determination that the count is less than a predetermined minimum number of pulses, the predetermined time period can be increased. Responsive to a determination that the count is greater than a predetermined maximum number of pulses, the predetermined time period can be decreased.