Single magnetic, unity power factor, isolated power converter with ripple free input current

The discontinuous conduction mode (DCM) boost or flyback circuit is a low cost solution to meet power factor correction (PFC) requirements. However, large ripple current in the input side requires a large differential mode (DM) filter inductor. For an offline application, a complete power supply design may also need an isolation transformer, increasing size, weight, cost and power loss. This paper proposes a single magnetic, isolated PFC circuit with ripple free input current. The need for a DM filter inductor is therefore eliminated. By using constant duty cycle and constant frequency control, the conventional PWM chip can be adopted for PFC application. The operation principle of the proposed circuit and the design considerations are given in detail. The simulation and experimental results are provided for verification