Frequency modulated self-oscillating switching power supply

摘要

A switching power supply that can operate in critical conduction mode as self-oscillating power supply (SOP) during moderate load, and in discontinuous conduction mode (DCM) under the control of a pulse-width modulated signal under small load, whereby the power consumption of the supply is decreases continuously as the load is decreased. A frequency modulated self-oscillating switching power supply (FMSOP) having a power switch, the switch being held OFF, after a zero-current detector detects that an output current falls to zero, until allowed to turn ON after a pulse having a load-modulated width that corresponds to the load. The FMSOP operates with a switch controller that may include a flip-flop to latch the detector's signal, a load-modulated pulse generator, and a combinatorial logic gate to combine the pulse and the latched signal.