Driver dims LED off a normal switch

July 19, 2012 // Christoph Hammerschmidt

O2Micro International Ltd, unveiled a new dimming architecture for the global LED lighting market. The company's patented Free Dimming technology enables LED bulbs to dim using any on/off switch, thus eliminating the burden of installing expensive dimmers. O2Micro claims the technology works with any on/off switch, including wall toggles, paddle switches, pull cords, rotary switches and other types of on/off switches commonly found on walls, extension cords and table/desk lamps.

According to industry estimates, there are roughly 150 million incandescent dimmers installed in the USA alone. In theory, LED bulbs are fully dimmable; however, designing them to be compatible with incandescent dimmers is challenging. Such designs add significant complexity and cost to the LED bulb, reduce efficiency, and often result in poor performance that leads to product returns and potential safety issues.

Chronic compatibility and performance issues include aesthetic problems such as flicker, audible hum, “jumpy” dimming, and poor turn-off performance. Others are various electrical issues such as inrush current, which stresses components in both the dimmer and LED bulb, shortening product lifetime and creating safety issues. Furthermore, support for legacy incandescent dimmers does not address the more than 85% of light bulbs that operate from non-dimming on/off switches. Although there are 150 million incandescent dimmers installed in the USA alone, according to the National Electrical Manufacturers Association (NEMA), there are over 4.4 billion medium, screw-based light sockets in the US, representing an enormous, untapped market opportunity.

Amidst these towering questions, O2Micro says it has the answer. The Free Dimming LED driver product family is inherently simple and works with any non-dimming on/off switch. It has broad appeal, working with the more than 85% of lights that are on non-dimming circuits. For consumers, eliminating dimmer cost and installation makes LED bulbs that incorporate O2Micro's Free Dimming LED driver easy to use and a great value.

For LED bulb manufacturers, O2Micro's Free Dimming LED drivers shift dimming from a cost burden to a profit enhancer by enabling them to expand their addressable market by capturing dimmer revenue that would normally be served by dimmer manufacturers. O2Micro's Free Dimming LED drivers offer the lowest BOM cost with the smallest footprint and have higher efficiency than incandescent dimming drivers by eliminating excess circuitry required to make LED bulbs work with incandescent dimmers. 

The products in O2Micro's Free Dimming LED driver product family, the pin-compatible OZ8022A and OZ8022B provide three-step dimming using any ordinary on/off switch. The LED drivers dim the LED bulb to one of three preset levels each time the on/off switch is toggled. For example, with each toggle action, the OZ8022A dims the LED bulb from 100% to 60% to 20% and then loops back to 100% full brightness, repeating the sequence.

The OZ8022B operates in reverse, starting at 20% then increases brightness to 60% then 100% with each flick of the wall switch; imitating the operation of a traditional three-way incandescent light bulb and providing even more energy savings by starting at the lowest level.

The OZ8022 series supports universal 85V to 265V operation, enabling one LED bulb to address the global marketplace. High efficiency greater than 89% reduces energy consumption and thermal management complexity. Integrated over-temperature, over-voltage, cycle-by-cycle current limiting, and LED short circuit protection provides safe and reliable operation. Excellent LED current regulation ensures consistent lumen output, regardless of varying line input conditions. 

The OZ8022A and OZ8022B are available in a SOT-23-6 package. All three products are in high volume production now. Samples and evaluation boards are available now for qualified customers.

For additional information, visit www.o2micro.com.

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December 15, 2011 | Texas instruments | 222901974

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