A family of capacitive current balancing methods for multi-output LED drivers

This paper proposes a family of simple, precise and lossless current balancing methods based on charge balancing for multi-output LED strings application. A capacitor is in series with the transformer secondary side to block the output DC voltage difference, and the output current balancing can be achieved by capacitor charge balancing. Compared to the conventional active current sharing technique using switching converter or linear switch, the proposed method can achieve high efficiency and excellent balancing performance. Compared to the previous passive current balancing methods, such as coupled inductor or capacitive mechanism, this one declines the cost and circuit complexity as well as increasing the balancing accuracy. A brief operation principle and design considerations of Halfbridge (HB) converter with proposed technique are presented. Experimental results from a 60W HB converter are in good agreement with the theoretical predictions.