SSL LED driver solves dimmer compatibility issues

6th February 2015

Siobhan O'Gorman

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An SSL LED driver, designed to solve dimmer compatibility issues in challenging, low-voltage lighting applications, has been released by Dialog Semiconductor. The iW3688 single-stage LED driver is designed for applications up to 20W, including A-style, BR, candle, GU10 and PAR bulbs and T8 LED tubes, as well as external lighting ballast drivers.

To provide compatibility with challenging TRIAC and digital dimmers, the device utilises the company’s patented intelligent digital dimming control technology. The driver also utilises Dialog’s patented digital algorithms, which enables high performance dimming at a lower cost compared to conventional external bleeder circuits.

Many low-power LED bulbs fail to draw enough current through the TRIAC to clear the holding current threshold, resulting in flicker and shimmer in dimmable LED bulbs. To solve this issue, many low-power bulb designs use an external bleeder circuit to draw extra current through the TRIAC while it is conducting. However, these bleeder circuits shorten the operating life of LED bulbs as they require additional external components which dissipate more power inside the bulb.

The iW3688 uses the company’s digital algorithms to modulate primary FET switching and draw extra current during dimming, eliminating the cost of up to 20 external components in the bulb design, including as many as 10 required for the external bleeder. By simplifying the EMI filter circuit and integrating the current sink, switching and V_^CC charging circuits, the device further reduces BOM costs. The driver’s advanced IC power management and voltage sensing allow for the use of low-cost, off-the-shelf inductors, providing additional savings.

To address LED bulb lifetime issues caused by excessive heat, the iW3688 integrates Dialog’s patented over-temperature protection de-rating technology. This monitors the temperature inside the sealed SSL bulb and seamlessly dims light output if the temperature rises above a safe operating threshold, then restores brightness as temperature falls.

“Dialog invented digital adaptive control LED driver ICs to optimise SSL luminaire performance and drive the cost of LED lighting down to an affordable price point for mass consumer adoption,” commented Davin Lee, Senior Vice President and General Manager, Power Conversion Business Group, Dialog Semiconductor. “Our iW3688 LED driver platform extends our lead in wide dimmer compatibility, dimming performance and low BOM cost.”