Abstract: High frequency induction welding power supply has the advantages of small size, high efficiency and quick heating rate.The traditional equipment which has rectification voltage regulation is low control precision and slow dynamic response and has also great switching power loss and low electrical efficiency.In the paper, a soft-switching technique for high frequency induction welding power supply in PWM PFM mixed control is proposed, its control principle and operating mode are briefly introduced, and the design of control circuit with phase lock loop is described.Experiment results show that this control is able to make all switches achieve softly work and has the advantages of wide power regulation and adjustment range of soft-switching.