Positive-negative pulse type high frequency switching power supply unit

摘要

The invention provides a positive-negative type high frequency switching power supply unit which provides a high frequency output of an ideal sine waveform to allow reliable switching with very low switching loss without being influenced by a leakage inductance of the load side, a parasitic capacitance and a parasitic inductance produced by a wiring line or the like, and a load condition. The positive-negative type high frequency switching power supply unit includes an H-bridge switching circuit including four semiconductor switching elements connected in an H- bridge connection, a resonance circuit which resonates with a positive- negative pulse wave outputted from the H-bridge switching circuit, and a PWM control circuit for detecting a voltage and current of the resonance circuit by means of a pulse transformer and a current detector, respectively, and feeding back the voltage and current to the H-bridge switching circuit so that the four semiconductor switching elements may perform switching operations in a switching frequency higher than the resonance frequency of the resonance circuit in a fixed switching pattern of on/off states.