US Patent 7701737 DC-AC converter

A DC-AC converter includes a signal generating module, a first switch, a first capacitor, a transformer, and a trigger signal generating module. The signal generating module generates a pulse width modulation (PWM) signal according to a trigger signal. The first switch has a control terminal receiving the PWM signal, and a first terminal and a second terminal coupled to a first terminal and a second terminal of the first capacitor respectively. The transformer has a primary winding coupled to the second terminal of the first switch, and a secondary winding coupled to a load. The transformer generates a driving signal to the load according to a signal variation of the primary winding. The trigger signal generating module compares a first signal outputted from the second terminal of the first switch with a phase delay signal thereof and thereby generates the trigger signal for controlling the frequency of the PWM signal.