Zero-voltage switching control circuit, method therefor, and voltage converter

Abstract

Disclosed are a novel zero-voltage switching control circuit and a control method. By a chip of a controller, a first switch unit is controlled to switch on-off of an input winding and a second switch unit is controlled to switch on-off between an auxiliary winding and a negative voltage level, wherein before the input winding is conducted, the auxiliary winding of a voltage converter is conducted with the negative voltage level in advance, and the input winding is forced to generates a negative current based on a coupling effect between the input winding and auxiliary winding, to release the energy of parasitic capacitance in the first switch unit cross voltages, so as to further enable a polarity inversion of the input winding, and the first switch unit cross-voltage decays to an expected low switching potential level. The invention can achieve the zero-voltage switching under a Continuous Conduction Mode (CCM) and a Dis-continuous Conduction Mode (DCM) to reduce the power consumption in switching of first electronic switch, and also in the embodiment of a Flyback converter, it separates the primary current and secondary current from each other that are originally with short overlap under the cross-over transition in CCM operation, so as to avoid a cross-conduction happens as well as to reduce the obstacle in controlling secondary side synchronous rectification.

Dependencies are inferred from the claim text.