A high-power-LED driver with power-efficient LED-current sensing circuit

For lighting application, high-power LED nowadays is driven at 350mA and a sensing resistor is used to provide feedback for LED-current regulation. This method adds an IR drop at the output branch, and limits power efficiency as LED-current is large and keeps increasing. In this paper, a power-efficient LED-current sensing circuit is proposed. The circuit does not use any sensing resistor but extracts LED-current information from the output capacitor of the driver. The sensing circuit is implemented in a Buck-boost LED driver and has been fabricated in AMS 0.35μm CMOS technology. Measurement results indicate a power-conversion efficiency of 92% and at least 90 times power reduction in sensing compared to existing approach.