Self-Oscillating LED Driver With Bus Voltage Regulation

Abstract

This paper proposes a two stage LED driver topology with bus voltage regulation and self-oscillating command circuit. The first stage, responsible for the power factor correction, is composed of a SEPIC converter operating in the discontinuous conduction mode of current. The second stage, responsible for supply the LEDs consists of a half-bridge inverter with a LC resonant filter. It is used a voltage regulation circuit to compensate an input voltage variation of 86 to 105% of the nominal value, keeping the bus voltage almost constant. In this way, the switching frequency is kept stable as well as the output current. A laboratory prototype with a rated power of 26 W was built in order to show the feasibility of the idea.