Power converter and control method thereof

A power converter, comprising:

• a primary side switching circuit comprising a first set of switches;
• a secondary side switching circuit comprising a second set of switches;
• a transformer coupled between the primary side switching circuit and the secondary side switching circuit;
• and
• a control circuit configured to control power transfer between the primary side switching circuit and the secondary side switching circuit by controlling the first and second sets of switches, wherein the control circuit is adapted to enable the first and second sets of switches in an enabling duration and disable the first and second sets of switches in a disabling duration, wherein the enabling duration and the disabling duration are operated respectively and alternatively, wherein the control circuit is configured to perform a control method comprising steps of:
• (a) recording an operation time of the power converter continuously;
• (b) enabling the first and second sets of switches;
• (c) determining whether the operation time is smaller than a time of the enabling duration, wherein in the enabling duration, the first and second sets of switches are enabled to operate with alternate gate pulses and a switching period, and wherein the enabling duration is longer than the disabling duration;
• (d) performing the step (c) again if the determining result of the step (c) is satisfied, and disabling the first and second sets of switches if the determining result of the step (c) is not satisfied;
• (e) determining whether the operation time is smaller than a sum of the time of the enabling duration and a time of the disabling duration;
• and
• (f) performing the step (e) again if the determining result of the step (e) is satisfied, and resetting the operation time to zero and performing the step (a) if the determining result of the step (e) is not satisfied, wherein the first and second sets of switches are disabled to be off constantly in the disabling duration, and the time of the disabling duration is determined by at least one of a maximum magnetizing current and a magnitude of a voltage that resets a magnetizing current or the maximum magnetizing current.