Patent ID: 7567443

Claim:
A power converter comprising: at least two main switching elements connected in series to a DC power source; an oscillator which has at least two capacitors or at least two subsidiary switching elements connected in parallel to said main switching elements and in series to said DC power source; a primary winding of a transformer connected between a junction of said two main switching elements and a junction of said two capacitors or of said two subsidiary switching elements; an output circuit which comprises first and second regulatory switching elements connected between respectively one and the other ends of a secondary winding of said transformer and an electric load; a polarity detector for detecting the polarity of AC voltage produced on said secondary winding of transformer by the on and off operation of said switching elements in said oscillator to generate detection signals; a drive circuit for receiving detection signals from said polarity detector to control the on and off operation of said first and second regulatory switching elements; a choke coil connected in said output circuit; a filtering circuit connected in parallel to said load; a pulse modulator for forming pulse-modulated signals having the varying pulse width or pulse density by potential difference between voltage from external input signals and applied voltage to the load; and a changeover circuit for turning said first regulatory switching element on when both of voltage levels of pulse-modulated signals from said pulse modulator and of detection signals from said polarity detector are simultaneously on a first level, and turning said second regulatory switching element on when both of voltage levels of pulse-modulated signals from said pulse modulator and of detection signals from said polarity detector are simultaneously on a second level; wherein AC power of voltage waveform similar to that of external input signals is supplied from said second secondary winding of said transformer through said choke coil and filtering capacitor to said load by alternately turning said first and second regulatory switching elements on and off.