An Auto-Zero-Voltage-Switching Quasi-Resonant LED Driver With GaN FETs and Fully Integrated LED Shunt Protectors

An auto-zero-voltage-switching (ZVS) quasiresonant LED driver with gallium nitride (GaN) FETs for general lighting applications is presented. The proposed LED driver switches at high frequency to minimize the inductors to microhenry range. ZVS can be automatically achieved with the proposed controller to eliminate switching loss. The GaN FETs enable high-frequency operation and improve the power efficiency. A fully integrated LED shunt protector is proposed to bypass the failed LEDs in series-connected LED strings. The overall lifetime of the LED strings can be improved, and the maintenance cost can be reduced. The characteristics of the ZVS quasi-resonant LED driver with small inductors and the conditions for ZVS are also discussed in detail. The LED driver is fabricated with a 0.35-μm 120-V high-voltage process. It can provide up to 25-W power to the LED with 2 × 3.3 μH inductors and achieves 91.4% peak efficiency and a 0.973 peak power factor from 60-Hz 100to 120-Vacinput.