Continuous Input Current Isolated Resonant LED Driver With Wide Input Voltage Range

In this article, an isolated resonant light-emitting diode (LED) driver featuring inherent constant output current characteristic at fixed frequency operation is presented. The LED current is regulated using the main switches operating duty cycle within a wide input voltage range variation while the integrated step-up structure brings continuous input current with low current ripple suitable for battery operation. The proposed isolated CLLC resonant network incorporates the transformer magnetizing and leakage inductances as the main resonant components leading to a lower number of magnetic components while improving the power density. Also, the zero-voltage-switching operation for the main switches and zero-current switching of the rectifier diodes are realized in the entire input voltage range. A detailed theoretical analysis of the proposed LED driver is presented. To verify the analysis and effectiveness of the proposed topology, a 100-W laboratory prototype with input voltage range of 35–60 V dc is designed and implemented for 48-V dc automotive applications which delivers 1 A current to a high brightness light emitting diode string including 30 series LEDs.