A High-Efficiency Linear LED Driver With Concave Current Control for Low-Power Application

This paper presents a linear light-emitting diode (LED) driver with concave current control method for low-power applications. In order to achieve a high efficiency of the linear LED driver, control methods with three different current shapes, namely, traditional flat current shape, convex current shape, and the proposed concave current shape, have been discussed and compared via theoretical analyses, numerical simulations, and experiments in this paper. It is concluded that the proposed concave current control method has the highest efficiency among these three methods for universal input voltage conditions. The operation principles and design considerations of the control method have been provided. It is verified by the experimental results that the proposed concave current control method has a 10% efficiency improvement when compared with the flat and convex current control methods. Furthermore in order to limit the peak current of the concave current for practical considerations, a revised cut-top current control method is presented by adding a limited current. Both simulation and experimental results show that a 37% reduction of the peak current is obtained for the cut-top current control method. On the other hand, a 5% improvement of the efficiency can be achieved by the revised cut-top current than flat and convex current control methods.