Switching-frequency control for regulated discontinuous conduction mode boost rectifiers

A novel switching-frequency control method for regulated 1-switch boost rectifiers operating at the boundary of the discontinuous and continuous conduction modes is presented in this paper. To obtain a source current with least amount of low-order harmonics, the duty cycle within a switching period is proportional to the ratio of the instantaneous value of the source voltage to the output voltage. According to the large signal analysis, the output voltage can be regulated by adjusting the switching frequency. Small signal modelling is performed to facilitate the design process. The proposed control scheme features advantages such as a higher input power factor and a higher regulated output voltage compared to the traditional discontinuous conduction control with a fixed switching frequency and a constant duty cycle. Any well-developed commercial PWM control IC can be adopted with only a minor modification. Experimental results show good conformation with the theoretical analysis.