Patent ID: 7737642

Claim:
A DC/AC inverter for inverting a DC voltage source to an AC power source to drive a load, the DC/AC inverter comprising: a resonant tank coupled to said load for transforming DC input power to an AC signal to supply power to said load; a half-bridge power switch circuitry coupled to said resonant tank and said DC voltage source for selectively coupling said DC voltage source to said resonant tank, the half-bridge power switch circuitry comprising: a first switch having an input terminal coupled to the DC voltage source, an output terminal coupled to the resonant tank, and a control terminal; and a second switch having an input terminal coupled to a ground line, an output terminal coupled to the resonant tank, and a control terminal; a current sensing circuit coupled to said load for providing a conduction sensing signal indicating conductive state of said load, and a current sensing signal indicating current amplitude of said load; a driving circuit coupled to the control terminal of the first switch and the control terminal of the second switch for transmitting a first driving signal to the control terminal of the first switch, and a second driving signal to the control terminal of the second switch according to a reference clock and a pulse width modulation signal; a pulse width modulator comprising: an error amplifier having an inverting terminal for receiving the current sensing signal, a non-inverting terminal for receiving a reference voltage, and an output terminal for outputting an error signal according to a comparison result of the current sensing signal and the reference voltage; and a comparator having an inverting terminal for receiving a modulation signal, a non-inverting terminal for receiving the error signal, and an output terminal for outputting the pulse width modulation signal according to the modulation signal and the error signal; and a frequency generator electrically coupled to the pulse width modulator and the driving circuit, said frequency generator for outputting the modulation signal to the comparator; wherein an operation frequency of said frequency generator is converted from a first frequency to a second frequency according to said conduction sensing signal.