Light-emitting diodes (LEDs) are widely used in biomedical devices, automotive lighting, and general illumination, due to their high luminous efficiency, low power consumption, and long lifetime. However, their nonlinear load characteristics require constant-current driving for reliable and safe operation. To solve this problem, a fixed-frequency class-E resonant DC-DC converter operating at 175 kHz is proposed and experimentally validated as a LED driver. The proposed class-E resonant DC-DC converter employs a Variable Inductor (VI) method in combination with an adaptive perturb-and-observe algorithm to regulate the output current against input voltage variations within the 28–48 V range. A 50 W prototype has been implemented and tested. Experimental results shows that the proposed system keep output current at 1.3 A while provide Zero-Voltage Switching (ZVS) condition across all operating conditions. Proposed VI-based control principle and Variable Frequency (VF) control was experimentally compared. As a result of the comparison, the VI-based fixed-frequency class-E converter achieved efficiency improvements of 2.86% and 3.69% at 45 V and 48 V, respectively. The average efficiency of the proposed system at all operating points is 0.88% higher. Consequently, the VI-based fixed-frequency class-E converter minimizes the switching losses observed in VF control.
Kenan Ünal (Thu,) studied this question.