LED direct AC drive has only had limited use, Fairchild says, because of the issue flicker (at mains frequency). This product, the company says, can reduce the flicker effect and allow the concept to be applied to commercial and industrial lighting. The IC offers good power factor and total harmonic distortion of under 20%; it supports dimming by analogue and pulse width modulation and can scale from 10 to 120W lighting systems, by parallel connection.
Flicker is specified by the peak-to-average ratio of the light emitted. The IC can be operated without energy storage (that smooths the dips in the light level) in which case it delivers a flicker factor of around 0.3; by adding four, 100 µF capacitors, this can be reduced to under 0.15, as demanded by commercial applications.
The FL77944 has, Fairchild says, all the important dimming capabilities required for smart lighting products, including phase-cut dimming as well as analog and PWM dimming, which is also key for wirelessly connected lighting. The FL77944’s ability to scale to support higher power applications up to 120W by wiring products in parallel is a critical feature. This reduces the number of different ICs that manufacturers need to keep in inventory. The FL77944 can eliminate the need for electrolytic capacitorss, transformers and inductance coils. This reduces both the bill-of-materials (BOM) costs and the overall complexity compared to designs using SMPS. It enables designers to reduce their board space requirements by locating the controller IC on the same PCBs as the LEDs and by eliminating the need for many passives. Products based on the FL77944 should be more reliable and last longer than SMPS-based products as there are inherently fewer points of failure. In particular, eliminating the need for electrolytic capacitors should improve reliability as they are a common source of failures in SMPS-based products.
An evaluation board, the FEBFL77944, is available evaluation board can also be ordered.