Apple Inc.
Quasi-resonant power converter with reduced dynamic switching losses

Abstract:

A power converter includes a current-monitoring on-state controller that is configured to adjust the timing of a switch-mode voltage conversion stage of the power converter. For example, the timing of the turn-on of a MOSFET associated with a buck converter operated in a discontinuous conduction mode (e.g., quasi-resonant) can be adjusted based on a zero crossing of current through a tank inductor also associated with the buck converter. More particularly, the MOSFET may be turned on after a predetermined delay is initiated after current through the tank inductor reaches zero. The predetermined delay is based on a resonance period defined by the characteristic capacitance of the MOSFET and the inductance of the tank inductor.