A Variable Turn-Off Time Control Method for Light Load Efficiency Improvement in Totem Pole PFC

Nowadays, the efficient totem pole power factor correction (PFC) converter is increasingly needed in various distributed power system applications to save energy. For the totem pole PFC converter, the traditional fixed switching frequency control method is inefficient at light load, because of the high switching frequency. The fixed turn-off time control method can reduce the switching frequency at light load; thus, the light-load efficiency can be improved. However, for fixed turn-off time control method, the average switching frequency is still high, resulting in the light load efficiency of PFC converter needs to be further improved. Thus, a variable turn-off time control method based on the fixed turn-off time control method is proposed to further improve the light load efficiency. The performance of this control method is verified by simulation. Compared with the fixed turn-off time control method, the switching frequency is reduced by 75% on average when the power is 50W. Through theoretical calculation of the loss of each part of the converter, the efficiency of the proposed control method can be increased by about 2% at light load.