The present invention provides a wireless power transmitter circuit which includes a power converter circuit, a power inverter circuit, a resonant transmitter circuit and a power control circuit. The power conversion circuit converts an input power to a conversion output power which includes a conversion output voltage. The power inverter circuit converts the conversion output power to an AC output power. The resonant transmitter circuit converts the AC output power to a resonant wireless power. The power control circuit generates a current reference signal according to the conversion output voltage, and generates a conversion control signal according to a difference between the current reference signal and a resonant current related signal, to control the power converter circuit such that the resonant wireless power is regulated substantially at a predetermined power level.