Inductor Current Measurement Strategy for High-Precision Output Current Control

Recently, high brightness white light-emitted diodes (LEDs) have become the best lighting sources. A primary-side regulator (PSR) is widely used for the LED lighting application. However, the PSR often experiences the drawback of output current inaccuracy which will shorten the LED's life-time. The objective of this paper is to propose the inductor current measurement strategy (ICMS) which can be adopted for different circuit topologies to achieve high-precision output current control under no output current feedback condition. The proposed ICMS senses the slope of inductor current to obtain the correct peak and valley values of inductor current. With the correct value and conduction time of the inductor current, the proposed ICMS can achieve high-precision output current regulation. The operation principle and mathematic derivations of the proposed ICMS are developed thoroughly. Two ICMS-based prototypes with different circuit topology for LED lighting application are built and tested. Computer simulations and experimental results are presented to confirm the theoretical results.