A Dimmable and Power-compensated AC Direct LED Driver with High Efficiency

A dimmable and power-compensated AC direct LED driver with high efficiency for lighting applications is presented. A Source-Coupled Pair (SCP) is adopted to realize the soft self commutating. There is no additional sensing or control circuitry, which lower the system power dissipation. A pulse-width modulation (PWM) dimming technique is applied in regulating the LED's brightness. Furthermore, the driver includes a Power Compensation module which enables the output power of LEDs approximately constant under various line voltage. The LED driver IC is designed and implemented in CSMC's 700 V 1 urn BCD process. The post-layout simulation results show that under 220 V vertical bar rms AC voltage, the driver has a high efficiency of 90.28% and realizes dimming with a 90% duty ratio, 10 KHz dimming signal. The output power compensated only changes 4% under a 10% variation in input voltage.