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

A novel family of loss-adaptive self-oscillating converters is developed for high-efficiency and low-cost LED driving. They consist of BJT-type self-oscillating units, loss-adaptive BJT driving units, and low-loss current sensing units. In this paper, a self-oscillating buck converter, one of the family members, is chosen to be introduced in detail. The contents include the operation principle, a loss-adaptive BJT-driving scheme, and a low-loss peak-current sensing method. For experimental verification, a practical self-oscillating buck converter was implemented by using some appropriate but cheap components and devices for a 24-V lighting system to drive up to 6 LEDs. The test results show that the prototype buck LED driver could start up successfully itself and operate highly efficiently in steady state.