In order to save energy

efficient totem pole power factor correction (PFC) converters are becoming more and more important in distributed power systems. The traditional control method has a high switching frequency at light load

which limits the improvement of its light load efficiency. Based on the traditional fixed turn-off time control method

this paper proposes a variable turn-off time control method

which can extend the switching period by adjusting the turn-off time of the main switch under light load conditions. Compared with the existing fixed turn-off time control and critical conduction mode control

the proposed method can adaptively adjust the switching frequency according to the input power

so as to optimize the efficiency under different load conditions. At light load

the light load efficiency of the converter is improved by reducing the switching frequency. In the case of heavy load

the switching frequency only decreases near the zero-crossing point of the half-cycle of the power frequency

which does not affect the power factor (PF) in the entire voltage range while ensuring high efficiency. Finally

a 350 W totem pole PFC converter prototype is built in this paper. The experimental results show that compared with the fixed turn-off time control method

the efficiency of the proposed control strategy is improved by 2% under light load conditions

reaching 96%.