Apple Inc.
Active Clamp Resonant Flyback Converter with Integrated Boost Stage

Abstract:

A single-stage power converter can include a boost segment configured to receive an input DC voltage and a flyback segment configured to generate an output DC voltage. The boost and flyback segments may share common switching devices, including a main switch and an auxiliary switch. The boost segment can further include a boost inductor. The flyback segment can further include a bulk capacitor, a resonant capacitor, a flyback transformer, and an output rectifier. The flyback segment can still further include a resonant inductance in addition to a primary winding of the flyback transformer, which may be a parasitic inductance and/or a discrete inductor. The converter can further include control circuitry configured to vary timing, frequency, and/or duty cycle of the main switch to regulate the output voltage. The converter can still further include a rectifier configured to receive an AC input voltage and produce the DC input voltage.