A High-Efficiency Quasi-Two-Stage LED Driver With Multichannel Outputs

In this paper, a new active current balancing method for a light-emitting diode (LED) driver with multichannel outputs is proposed. In the proposed structure, a low-power nonisolated dc-dc converter in series with each LED string is used to regulate the LED string current. Different from conventional active current balancing methods, in the proposed method, the nonisolated dc-dc converters only process a small portion of the total output power. Thus, the cost and size can be greatly reduced. An adaptive bus voltage control method is also proposed to minimize the output power of the nonisolated dc-dc converters. The proposed method features good modularity, expandability, and individual current control capability. Performance of the proposed method is validated by the experimental results from an 80-W prototype with four channel outputs.