In the field of switching power supplies, various Zero-Voltage-Switching (ZVS) circuits have recently been proposed for the reduction of EMI noise. The authors proposed a novel ZVS DC/DC converter of constant frequency PWM control with clamping the device voltage to a DC bus line. Moreover, we proposed a novel Power Factor Correction (PFC) circuit of ZVS operation that is synchronous with the DC/DC converter without using any auxiliary switches. The proposed converter realized high conversion efficiency, high power factor, and low conducted EMI noise.