A soft switching power converter includes a first switch for switching a transformer to transfer energy. A second switch is equipped to switch energy in a capacitor to the transformer to achieve soft switching for the next switching cycle. A control circuit is coupled to an output of the power converter for generating a first signal and a second signal in response to a feedback signal for regulating the output of the power converter. A first delay time is generated after the first switch is turned off and before the second signal is on. A second delay time is generated after the second switch is turned off and before the first signal is on. The second delay time is increased corresponding to a decrement of the feedback signal under light load conditions.