A Peak Current Controlled Flicker-Free AC-DC LED Driver With Dimming Function

Dimming function is an attractive feature for light-emitting diode (LED) drivers since it can adjust the lighting levels for consumer comfort. This article proposes a simple but effective peak current control strategy to achieve dimming operation. Unlike the traditional dimming techniques, no extra switch, pulsewidth modulation controller, or linear current regulator in series with the LED strings is used in the proposed method, resulting in easy implementation and low cost. A 33 W ac-dc Sepic LED driver prototype, both with power factor correction (PFC) and without PFC, is constructed and tested to validate the proposed peak current control method. Moreover, flicker-free operation of LEDs is necessary for human eye comfort. Therefore, this article also introduces a ripple remover circuit (RRC) to remove low-frequency LED current ripple in ac-dc LED drivers. At the same time, the output capacitor can be greatly reduced by the critical design of the RRC. Unlike the existing methods, the inclusion of RRC into a driver circuit is straightforward and RRC has no complex structure. The proposed solution is generally suitable for all single-phase ac-dc LED drivers. Experimental results are presented to validate flicker-free operation by RRC.