Stabilising current driver for high-voltage light-emitting diodes

High-voltage light-emitting diodes (HV LEDs) possess higher cut-in voltages and works at a high supply voltage. As the specific feature, they can be directly driven via universal utility-line voltages after appropriate rectification. This significantly simplifies the circuit structure and reduces the manufacturing cost. While HV LEDs are driven directly by half-wave rectified DC power source, which is an impure form of DC, their lumen is easily affected by changing the AC voltage source, while only constant current control is insufficient for stable lumen, thus hindering their usefulness in practical applications. This study proposes a simple, however effective, HV LED driver via a proportional and integral current control accompanied with feedforward compensation which is capable of maintaining stable lumen under changing AC voltage sources. Experimental results have demonstrated satisfactory performance in lighting.