Study and implementation of a SEPIC LED driver with adjustable output voltage

This paper presents the study and implementation of an LED driver of which the topology is a SEPIC operated under boundary conduction mode (BCM). The output diode features zero-current switching (ZCS). An Inverse-Buck converter is cascaded at the output for the design of an adjustable output voltage. The stability, efficiency and output ripple of a traditional single-stage converter with wide range of output voltage can be improved. For the dimming circuit, the light sensor and IR sensor are additionally used to detect the brightness and presence of human beings. The studied LED driver can be applied for different numbers of LEDs in a string. And the intelligent dimming system can save the energy and extend the applications. Finally, a 126-W laboratory prototype is implemented and verified with the simulations and theoretical analysis. The input voltage ranges from 90Vac to 130Vac and the output voltage can be changed from 25 V to 45 V. The efficiency can achieve 87% at full load condition.