Apple Inc.
Continuous Conduction Boost Converter with Zero Voltage Switching and Power Factor Correction

Abstract:

A ZVS boost converter can include a boost inductor coupled to a DC voltage bus, a main switch configured to selectively store energy from the DC voltage bus in the boost inductor and deliver the stored energy to a load, a synchronous rectifier, and a resonant circuit coupled across the main switch. The resonant circuit can allow for zero voltage switching of the main switch and the synchronous rectifier switch. The resonant circuit can be a series resonant RC circuit. The boost converter can be operated in a continuous current mode, with the main switch operated at a constant frequency with a variable duty cycle to maintain output voltage regulation and the synchronous rectifier operated complementarily to the main switch. The duty cycle of the main switch can be controlled using a current window controller. The ZVS boost converter may be incorporated in a power factor corrected AC-DC converter.