Isolated Soft Switched Resonant Led Driver with Constant Output Current and Wide Input Voltage Range

This paper proposes an isolated LCC resonant converter (LCC-RC) designed to deliver a constant output current for LED drivers across a wide range of input voltages by integrating a boost front-end stage with an LCC resonant converter. This topology leverages an LCC network to deliver numerous advantages. It integrates the boost filter inductor and transformer magnetizing inductance, ensuring that the primary switches achieve full Zero Voltage Switching (ZVS) and the secondary rectifier diodes experience Zero Current Switching (ZCS) across a wide range of duty cycles. Notably, the output current remains load-independent, making this configuration well-suited for LED applications. In addition, efficiency is improved by functioning near the resonant frequency. The hybrid structure of the proposed converter facilitates the use of a straightforward constant-frequency asymmetrical pulsewidth modulation (APWM) scheme to control the output current. To confirm the theoretical analysis and validate the LED driver functionality, a 50 W experimental prototype of the proposed driver was successfully created in the laboratory. This prototype supports an extensive input voltage range spanning from 18 V to 40 V, enabling it to supply a 500 mA output current to a series of 1 to 30 LEDs. This corresponds to an extensive output voltage capability spanning 3.3-100 V.