Primary-Side Peak Current Measurement Strategy for High-Precision Constant Output Current Control

The objective of this paper is to propose the primary-side peak current measurement strategy (PCMS) for the high-precision constant output current converter. The primary-side regulator (PSR) is widely used for low-cost and low-power light-emitted diode (LED) lighting application with universal input voltage range. However, the conventional PSR suffers from the drawback of current inaccuracy so that the LED may be damaged easily. Therefore, the PCMS method for PSR to achieve high-precision constant output current control is proposed. In this paper, the real causes of the output current inaccuracy by using PSR are discussed. The mathematical expression of the output current measurement error is derived. Then, the operation principle of the proposed PCMS is presented. Hardware experimental measurements are presented to verify the performance of the proposed PCMS. The measured data show that by using the PSR with the proposed PCMS, the LED output current error can be limited within ±2% under different operation conditions.