Joon-Hyun Yang

Symmetric current balancing circuit for multiple DC loads

One of the key challenges in driving multiple parallel loads using a single circuit is to ensure that each load share the same current. Current imbalance occurs because these loads have varying individual characteristics, which surface due to inevitable deviations in mass production. Lighting is one representative application where multiple lamps such as LED (light-emitting diode) arrays need some sort of current balancing mechanism. While resistive balancing technique can be highly inefficient, current balancing using dedicated control IC for each channel significantly increases the cost and circuit complexity. In this paper, a novel current balancing circuit for multiple DC loads is proposed. A smart combination of an inherent symmetry of circuit and capacitive balancing mechanism enables an efficient and cost-effective current balancing. The operating principle of the proposed balancing method is analyzed in detail and an appealing generalization is made. The feasibility of the proposed balancing scheme is verified by developing a hardware prototype to drive a 100W system, having six LED arrays.

A low cost multiple Current-Voltage concurrent control for smart lighting applications

This paper focuses on the Current-Voltage concurrent control method devoted to the multiple LED (light-emitting diode) string driver. Isolated DC to DC converter with cascaded chopping switch is proposed for smart lighting system such as light with sensor or back light unit of display, which need to control the current of parallel connected multiple LED stings and regulate DC voltage for micro controller for brightness control. The proposed circuit regulates the current of parallel connected multiple LED strings and additional DC voltage output simultaneously. To verify the performance, experimental results are presented based on the prototype board. 5V, 1A DC voltage and two LED strings with different forward voltages are used for output loads. 23W output power is achieved and measured efficiency is in the range of 85%-87%