Resonant Switched-capacitor Auxiliary Circuit for Active Power Decoupling in Electrolytic Capacitor-less AC/DC LED Drivers

This paper introduces an auxiliary circuit that is used to buffer double-line-frequency ripple power and form electrolytic capacitor-less single-phase AC/DC LED drivers. The proposed auxiliary circuit is implemented by a resonant switched capacitor circuit behaving as a gyrator circuit, namely a voltage-dependent current source. The output current of the auxiliary circuit is regulated with constant on-time and hysteresis control schemes. Comparing with other alternative methods, the proposed auxiliary circuit has less power loss due to its zero-current switching (ZCS) operation, and includes smaller passive components because of its higher operating frequency (about 3 MHz). An LED driver prototype with the proposed auxiliary circuit is built, and the experimental results are given to verify the proposed topology and the parameter design.