Abstract
A primary-side regulation AC-DC constant voltage control chip is designed, which employs a novel cable compensation technique to improve the precision of the output voltage and pursue a wider load range for regulation. In the proposed controller, constant voltage (CV) is achieved by OSC charging current and current-limiting point adjustment. Meantime, according to different cable lengths, the sampled voltage is regulated by injecting current to pull-down resistance of the system to obtain an accurate output voltage. The proposed chip is implemented in TSMC 0.35 mu m 5V/40V BCD process, and a 12V/1A circuit prototype has been built to verify the proposed control method. Experimental results show that the maximum cable compensation current reaches 43 mu A, and the precision of the output voltage is within +/- 3% in a wide range of output current from 0 to 1 A.