A current ripple cancellation circuit for electrolytic capacitor-less AC-DC LED driver

This paper presents a bidirectional buck-boost current ripple cancellation circuit applied to electrolytic capacitor-less flyback LED driver with power factor correction (PFC). By operating the flyback converter in discontinuous conduction mode (DCM), high power factor can be obtained under universal input voltage range. The bidirectional buck-boost converter can minimize the twice-line-frequency output current ripple using simple open-loop pulse width modulation (PWM) control without complex control scheme, and modularization is possible for other types of converter at the PFC stage. The output current ripple can be significantly reduced without using electrolytic capacitors (E-Cap) and the power factor is near unity under universal input voltage. Finally, a 700 mA / 20 W hardware prototype is built to verify the feasibility of the proposed method.