Abstract: A novel zero-voltage and zero-current switching (ZVZCS) three-level converter,and the drive circuit of the transistor were analyzed.The feasibility in application of welding power supply was investigated.And the circuit was simulated using software PSPICE 9.2.The results show that ZVZCS three level converter has not only the merit of convertional soft-switching pulse width modulation converter,but also other merit.Therefore,it fits for occasion of active power factor correction or high input voltage.