Two-switch BCM flyback single-stage PFC for HB LED lighting applications

This paper presents two-switch boundary conduction mode (BCM) flyback power factor correction (PFC) for high-brightness light-emitting-diode (HB LED) applications. The proposed two-switch flyback converter employs an energy regenerative reset circuit, which allows continuous energy conversion over entire line cycle even when the reflected output voltage of the transformer is larger than the instantaneous line voltage resulting in a duty cycle greater than 50%. The two switch configuration also recycles the energy of the transformer leakage inductance to the input allowing high efficiency. The operation and performance of the proposed circuit are verified on an experimental prototype converter with 20 V and 80 W output. The measured efficiency at full load remains above 89% across entire universal line range. The input current harmonics also meet the IEC61000-3-2 (class C) standard for lighting application.