Dim-to-Warm LED Driver Based on a Quasi-Resonant Boost Converter in Combination With a Low-Dropout Current Regulator for Integrative Lighting Systems

This article presents a cost-effective postregulator designed for dim-to-warm (D2W) solid-state lighting applications, where conventional pulse-width modulation (PWM) dimming may be inadequate. D2W lamps aim to replicate the natural shift in sunlight’s color temperature throughout the day, enhancing visual comfort and well-being. The proposed solution combines a dc–dc quasi-resonant boost (QRB) converter with a low-dropout current source (LDOCS), enabling precise current control and eliminating flicker. This architecture ensures zero-voltage switching (ZVS) on the main transistor and zero-current switching (ZCS) on the output diode, thereby improving efficiency and reducing electromagnetic interference. To analyze the converter’s behavior, a simplified energy-balance model is employed, avoiding the complexity of full harmonic analysis while maintaining accuracy. The control strategy ( $\text{ZC-}t_{\textsc{on}}$ ) uses general-purpose op-amps and a low-cost IC originally intended for power factor correction to regulate the on-time of the main switch, triggered at the zero crossing of the resonant capacitor voltage. To facilitate the design of the converter, a complete methodology is presented and validated through a prototype implementation. Experimental results demonstrate 93.5% peak efficiency, consistent ZVS/ZCS operation across the entire dimming range, and compliance with CIE S 026:2018 standard. This solution offers a practical and scalable approach for high-quality, human-centric lighting systems.