A critical conduction/bi-directional constant off-time converter with high power factor

A novel technique is introduced which allows a DC-DC power converter to be operated in either of two modes: critical conduction; or bidirectional constant off-time. This dual mode power converter allows operation from full load to no-load without loss of output regulation. A small signal AC model for the power stage of the dual mode power converter is presented. The proposed new dual mode operation is applied to an offline flyback power converter. The converter can be controlled as a conventional DC/DC converter or may be applied as a high power factor AC/DC converter. Both simulated and measured results are presented