An electrolytic-capacitorless and inductorless AC direct LED driver with power compensation

In this paper, a novel system for driving LEDs directly from AC supply without the use of electrolytic capacitors and inductors is proposed. The system includes a power compensation module, enabling the output power of LED approximately constant if there is a fluctuation in input voltage. Unlike the conventional LED drivers, the proposed LED driver only employs one rectifier, one controller IC, four LED strings and a few chip resistors and capacitors. The four LED strings will automatically conduct according to the level of input voltage, thus creating a step-shaped input current proportional to the sinusoidal voltage waveform. By this means, high power factor is achieved. The controller IC is designed by using CSMC´s 0.8-μm 650V process. Simulation results show that the LED driver has a high power factor of 97.46% and efficiency of 90.64% under the 220V|rms utility input voltage.