Switching-frequency control for regulated discontinuous-conduction-mode boost rectifiers

A novel switching-frequency control method for regulated one-switch boost rectifiers operating at the boundary of discontinuous and continuous conduction modes is presented in this paper. To obtain a source current with the 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 voltage gain analysis, the output voltage can be regulated by adjusting the switching frequency. Small-signal modeling is performed to facilitate the design process. The proposed control scheme features advantages such as higher input power factor and 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 pulsewidth-modulation control integrated circuit can be adopted with only a minor modification. Experimental results show good conformation with the theoretical analysis.