A Loss-Adaptive Self-Oscillating Buck Converter for LED Driving

A loss-adaptive self-oscillating buck converter is proposed for high-efficiency and low-cost LED driving. It consists of a self-oscillating unit composed of bipolar junction transistors (BJTs)-type self-oscillating unit, a loss-adaptive BJT driving unit, and a low-loss peak-current sensing unit. In this paper, its operation principle including a loss-adaptive BJT-driving scheme and a low-loss peak-current sensing method is introduced. For experimental verification, a prototype LED driver was implemented with some cheap components and devices for a 24-V lighting system to drive up to six LEDs. The test results show that the prototype LED driver could successfully start up itself and operate highly efficiently in steady state. In order to improve the performance of the proposed buck converter, a useful pulse-width modulation (PWM) LED dimming function is discussed for the future study.