An Improved High-Frequency Single-Stage AC LED Driver with Soft Switching Operation and No Input Electrolytic Capacitor

This paper presents a new single-stage soft-switched light emitting diode (LED) driver that directly connects to the AC input using a high-frequency bidirectional switch. The absence of an electrolytic capacitor enhances the LED driver's lifespan. The proposed driver achieves Zero Voltage Switching (ZVS) for power switches across the entire AC input voltage range, recovering/removing switching energy (E_oss, E_on, and E_off) through a resonant circuit. Inspired by the AC-DC Cuk topology, the proposed resonant circuit design achieves soft switching condition without any additional passive or active components. This distinctive advantage enables the LED driver to operate at MHz frequencies, addresses thermal concerns, and achieves a more compact and lightweight LED driver, even when utilizing a Gallium Nitride (GaN) transistor as the high-frequency bidirectional switch. The paper includes an analysis of the proposed converter's operation, simulation results, and a comparative study with existing Cuk-based AC LED drivers.