Resonant half-bridge flyback power converter with skipping cycles and control method thereof

A resonant half-bridge flyback power converter comprising:

• a first transistor and a second transistor which are configured to form a half-bridge circuit;
• a transformer and a resonant capacitor which are connected in series and are coupled to the half-bridge circuit;
• and
• a switching control circuit configured to operably generate a first driving signal and a second driving signal to control the first transistor and the second transistor respectively for switching the transformer to generate an output voltage;
• wherein the first driving signal is configured to magnetize the transformer;
• wherein the second driving signal includes at most one pulse between two consecutive pulses of the first driving signal, wherein the at most one pulse of the second driving signal includes either a resonant pulse for operating a resonant cycle after the transformer is magnetized or a ZVS (zero voltage switching) pulse for achieving ZVS of the first transistor;
• wherein the switching control circuit includes a timer configured to operably generate a skipping cycle period when an output power corresponding to the output voltage is lower than a predetermined threshold;
• wherein a resonant pulse of the second driving signal is skipped during the skipping cycle period;
• wherein the skipping cycle period is increased in response to the decrease of the output power;
• wherein the resonant cycle further includes an extended ZVS period for achieving ZVS of the first transistor.