The MR16-centric driver ICs offer compatibility with electronic and magnetic 12-VAC transformers while Dialog's newest driver for line-powered retrofit lamps minimizes the external component count.
Dialog Semiconductor has announced two new LED driver ICs headed into next week's Strategies in Light trade show. The iW3662 is the company's first IC targeted specifically at compact MR16 lamps that are designed to work from a transformed 12-VAC input. The iW3688 is a next-generation driver for A- lamps and other lamps powered directly from the AC line, and Dialog says the new design further reduces the bill of materials (BOM) in solid-state lighting (SSL) lamp development projects.
As the product models imply, the driver ICs are a continuation of the technologies originating at iWatt, a company Dialog acquired back in mid-2013. Both of the new platforms rely on the company's digital-control technology to enable features such as compatibility with a broad variety of triac or other phase-controlled dimmers.
The iW3688 is the first product based on the company's latest driver technology platform. Functionally, the IC is an improved version of the company's W3606/08 driver ICs that rely on a single-stage power conversion architecture and that support phase-cut dimming. In a single-stage design, power factor correction and constant-current power conversion are performed by the same circuitry. The result is fewer external components and lower cost, although some single-stage designs exhibit flicker while dimming and higher noise or distortion levels.
Dialog says the new iW3688 eliminates more than 20 external components required in drivers that use competitive single-stage ICs. The design does not require an external bleeder circuit to ensure that triac dimmers remain active. Instead, the primary FET is modulated during dimming to keep current draw at a level that will power the triac. Other components are eliminated via integrating the current sink, switching, and operational-voltage-charging circuits.
The new IC can deliver 20W of output power, up 25% from prior levels. Dialog will target A-lamps, BR lamps, LED T8 tubes, PAR38 lamps, and decorative products including candle-style bulbs. The new driver IC includes the protection features the company has introduced previously and supports power factor greater than 0.95.
MR16 driver IC
Meanwhile, the iW3662 marks the first time that Dialog has designed a driver IC just for the low-voltage market. The MR16 lamp has presented a considerable challenge to the SSL industry both because of the small lamp size that further limits space for driver electronics relative to larger lamps, and the fact that there are a mix of magnetic and electronic transformer types used to deliver the low-voltage input. We covered the challenges in detail back in early 2012, and while the situation has improved LED MR16s remain problematic.
Dialog used digital sensing and control circuits similar to those it uses for adaptive dimming to solve the MR16 dilemma. The driver IC can detect the transformer type and adapt operation for electronic or magnetic transformers. The driver IC can dynamically load the transformer at the appropriate times to ensure continuous operation of the transformer. With many other LED MR16 lamps, the transformer will stop conducting when an LED lamp draws too little power. With 50W-halogen-replacement LED lamps drawing 8W or so, SSL retrofits of MR16 sockets have been difficult.
"Dialog is the definitive leader in digital control technology for SSL lighting, with LED driver solutions for applications ranging from small form-factor retrofit bulbs to commercial lighting ballasts," said Davin Lee, senior vice president and general manager of the Power Conversion Business Group at Dialog Semiconductor. "The one remaining portion of the market we had not addressed was the low-voltage, dimmable MR16 segment, where our customers experience transformer and dimmer compatibility issues with existing LED driver solutions. Our innovative iW3662 builds on our digital control expertise with new intellectual property developed specifically for the low-voltage SSL lighting market."
The company has already won one customer in Sengled Lighting. "The challenge with low-voltage, dimmable MR16 lighting is compatibility with the existing infrastructure of transformers and dimmers," said Johnson Shen, founder and president at Sengled. "Dialog’s new iW3662 LED driver enabled us to easily, elegantly, and cost effectively solve these issues and enabled us to deliver the highest-quality dimmable MR16 LED bulbs that allow consumers to seamlessly replace halogen bulbs today."
The driver IC can support one- or two-stage driver designs. Dimming to 5% of full output, the IC works with triac and electronic phase-controlled dimmers, both leading- and trailing-edge varieties. And it includes the Dialog suite of circuit protection functions.
