Two-stage power conversion architecture for an LED driver circuit

This paper presents a merged-two-stage circuit topology suitable for efficient LED drivers operating from either wide-range dc input voltage or ac line voltage. This two-stage topology is based on a soft-charged switched-capacitor pre-regulator/transformation stage and a high-frequency magnetic regulator stage. Soft charging of the switched capacitor circuit, zero voltage switching of the high-frequency regulator circuit, and time-based indirect scale current control are used to maintain high efficiency, high power density, and high power factor. Two implementations of the proposed architecture are demonstrated: a wide input voltage range dc-dc converter and a line interfaced ac-dc converter. The dc-dc converter shows 85-95% efficiency at 20 W power across 25-200 V input voltage range, and the ac-dc converter achieves 88% efficiency with 0.93 power factor at 8.4 W average power.