Analysis, modeling and controller design of CRM PFC boost ac/dc converter with constant on-time control IC FAN7530

In this paper, a boost ac/dc converter is controlled by an on-time control IC FAN7530 to operate in critical conduction mode (CRM) and exhibits the capability of high power factor correction (PFC). In order to simplify the steady-state analysis, the operating principle is analyzed by a functional-block-diagram (FBD) method. The component considerations are also presented herein. Additionally, the small-signal model of a CRM PFC boost ac/dc converter with variable switching frequencies is derived. Based on the derived mathematical model, a voltage controller is thus well designed to make the proposed boost ac/dc converter have the performances of high power factor and output voltage regulation. Finally, a 300 W prototype of the CRM PFC boost ac/dc converter with IC FAN7530 is implemented. Its performance of high power factor is thus validated by experimental results. Furthermore, the regulation of output voltage despite the variations of the peak line voltage and load resistance is demonstrated.