Patent ID: 8649189

Claim:
A power supply for converting an input voltage into an output voltage, comprising: a switch circuit capable of transferring energy of the input voltage; a transformer having a primary side and a secondary side for storing energy transferred from the switch circuit at the primary side and transferring stored energy at the primary side to the secondary side according to a switching operation of the switch circuit, thereby generating the output voltage; a resonant circuit connected between the switch circuit and the primary side of the transformer capable of generating resonance to transfer energy of the input voltage to the primary side of the transformer; a power control circuit for comparing an input current sensing signal indicative of a sensed input current of the power supply and a power level control input which indicates magnitude of an output power desired by a user for generating a frequency modulation control signal, wherein the frequency modulation control signal is capable of controlling the output power of the power supply and a suppression of harmonics of an input current of the power supply; and a square wave generator connected to the power control circuit for generating a driving signal for driving the switch circuit according to the frequency modulation control signal, and wherein a frequency of the driving signal is varied synchronously with a frequency of the frequency modulation control signal, thereby suppressing harmonics of the input current of the power supply and regulating a switching frequency of the switch circuit, so as to regulate an output power of the power supply.