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Conventional topologies for high-power LED drivers with high power factors (PFs) require large capacitances to limit the low frequency (100 or 120 Hz) LED current ripples. Electrolytic capacitors are commonly used because they are the only capacitors with sufficient energy density to accommodate high-power applications. However, the short life span of electrolytic capacitors significantly reduces the life span of the entire LED lighting fixture, which is undesirable. This paper proposes a bipolar (ac) ripple cancellation method with two different full-bridge power structures to cancel the low-frequency ac ripple in the LED current and minimize the output capacitance requirement, enabling the use of long-life film capacitors. Compared with the existing technologies, the proposed circuit achieves zero double-line-frequency current ripple through LED lamps and achieves a high PF and high efficiency. A 100-W (150 V/0.7 A) LED driver prototype was built which demonstrates that the proposed method can achieve the same double-line-frequency LED current ripple with only 44-μF film capacitors, compared with the 4700-μF electrolytic capacitors required in the conventional single-stage LED drivers. Meanwhile, the proposed prototype has achieved a peak power efficiency of 92.5%, benefiting from active clamp technology.

A conventional offline single-stage light-emitting diode (LED) driver with a high power factor usually produces a significant twice-line-frequency ripple LED current, where the ripple LED current is presented as flickering to human eye. This paper introduces a ripple cancellation method to remove the twice-line-frequency voltage ripple for an offline single-stage LED driver with a power factor correction. Consequently, a dc LED current can be produced to achieve flicker-free LED driving performance. At the same time, the required storage capacitor for the proposed LED driver can be greatly reduced, and the circuit implementation to achieve ripple cancellation is simple. Thus, the overall cost of the proposed LED driver is low. The proposed LED driver also features high efficiency because of its power structure. A 35-W Flyback experimental prototype and a 10-W Buck-Boost experimental prototype have been built to validate the proposed design and demonstrate its optimal performance.