A critical-mode (CRM) operation has recently been used for low-to-medium power-level power factor correction (PFC) boost converter circuit. In theory, this circuit provides very good power factor and little distortion. However, in a real circuit, the input current of such operation suffers from significant input current distortion. In this paper, the phenomenon of input current distortion was analyzed, and the cause was traced to the parasitic capacitance of the MOSFET switch. An on-time adjustment control scheme, based on rigorous mathematical analysis, was proposed to overcome this problem. In addition, zero voltage switching (ZVS) operation was incorporated into this new scheme. An implementation of the proposed strategy was also presented. Simulations were conducted to verify the validity of the proposed scheme.