Patent ID: 9621056
Date: 2017-04-11
CPC Classifications: H02M,Y02B

Claim:
1. A method of controlling a phase-shift full-bridge (PSFB) converter in a light load operation to switch control modes by detecting magnetizing current of a transformer of the phase-shift full-bridge converter, the phase-shift full-bridge converter comprising a full-bridge switching circuit having a first power switch, a second power switch, a third power switch and a fourth power switch, the method comprising following steps: (a) operating the PSFB converter in an extended PSFB control mode when the magnetizing current of the transformer compared to an output choke current mapped to a primary side thereof is larger; (b) operating the PSFB converter in a modified PSFB control mode when the magnetizing current is gradually reduced until the electric charge transported by the residual magnetizing current is close to or less than or equal to a half of a DC input voltage; (c) implementing the optimal degree of soft driving the PSFB converter to double the magnetizing current under the modified PSFB control mode; and (d) when the phase-shift full-bridge converter is operated in the modified PSFB control mode, a second switch control signal and a third switch control signal being simultaneously converted from low levels to high levels so that the second power switch and the third power switch are simultaneously turned on, switching losses being jointly burdened by the second power switch and the third power switch, wherein the full-bridge switching circuit is not controlled to be operated in a burst mode by a frequency reduction.