Practical Switching Frequency Control for Improved Efficiency in CCM Boost PFC Converters at Light Load

Existing control methods in continuous conduction mode (CCM) boost PFC topologies employ a fixed switching frequency over the whole range of operation. Besides a simple implementation, retaining the switching frequency unchanged, places front stage converters at a suboptimal level during light load operating conditions. In particular, the dominant switching loss can often lead to an adverse impact on the systems efficiency. This paper proposes a novel control approach to both optimize the light load efficiency and improve input current regulation issues associated with a switching frequency adjustment. The control method is verified using a 3kW bridgeless totem-pole PFC prototype delivering a substantial switching loss reduction enabling 99% power conversion efficiency even with diode rectification.