Automotive LED driver based on high frequency zero voltage switching integrated magnetics Ćuk converter

Abstract

This paper presents a high-frequency zero voltage switching (ZVS) integrated-magnetics Cuk converter well-suited for automotive LED-driver applications. Input inductor, output inductor and the transformer are realized on a single magnetic structure, resulting in very low input and output current ripples, thus reducing EMI and the need for an output filter capacitor. Furthermore, the converter switching frequency is selected above the AM band to reduce radio frequency interference. Active-clamp snubbers are used to mitigate effects of the transformer leakage inductance. It is found that the active-clamp snubbers introduce substantial deviations in the steady-state operation of this converter when compared to a conventional Cuk converter. A numerical analysis technique is introduced to quickly evaluate the steady state behavior including the effects of non-linear transistor output capacitances on ZVS transitions. A prototype 1.8 MHz Cuk converter with integrated magnetics is designed, built and tested. The prototype converter supplies 0.5 A output current to a string of 1-to-10 LED's. It achieves 89.6% peak powerstage efficiency, and maintains greater than 80% overall efficiency across the wide output voltage range.