Self-oscillating H bridge lights white LED from one cell
Date: Nov 26, 2009 | Author: Luca Bruno, ITIS Hensemberger Monza, Lissone, Italy; Edited by Martin Rowe and Fran Granville | EDN
You can build a self-oscillating H bridge by replacing the pullup collector resistors of a classical BJT (bipolar-junction-transistor) astable multivibrator with PNP BJTs (Figure 1). Because this circuit oscillates at supply voltages as low as 0. + read more.
Gadget Freak Case #153: Accent Lights Are a Crowning Achievement
Date: Nov 23, 2009 | Author: Design News Staff | Design News
As a way to set the mood in his family room, when he remodeled Joe Peck put multi-color LEDs behind the crown molding. + read more.
Power-converter IC targets dimmable LEDs, needs no optoisolator
Date: Nov 12, 2009 | Author: By Margery Conner, Technical Editor | EDN
The large installed base of dimmable-lighting switches dictates that most new lighting technologies, including LED lights, should support dimming, and the myriad disparate specifications for dimming switches requires these lights to meet a wide range of characteristics. + read more.
Fader switch uses inexpensive controller
Date: Nov 12, 2009 | Author: William Grill, Lenexa, KS; Edited by Martin Rowe and Fran Granville | EDN
Customizing a model or a simulator with a bit of illumination is a nice touch. Rather than a simple on or off, you can add a touch of both refinement and control to your display with fading light. + read more.
Why LED replacement bulbs for incandescents (may) need isolation
Nov 24 2009 11:14AM | Comments (7)
Last week a reader posted a question on the article, Power-converter IC targets dimmable LEDs, needs no optoisolator, asking, “Can anyone explain why LED lighting needs isolation from the AC line? Incandescents require no such isolation; why burden LEDs with this?” My understanding was that it was aUL rule, but before I pushed the “submit” button on my reply, I decided to ask the folks at iWatt. Here’s iWatt’s reply:
"The US Department of Energy's Energy Star program does not mandate the use of isolated or non-isolated LED drivers for offline LED lamps. The LED lamp manufacturers are free to use isolated or non-isolated LED driver designs. [However, a] heat sink is often used to take away heat from the LEDs. The heat sink is generally made of metal and i... + read more
Ceramic caps promise long lifetimes for smaller LED lights
Nov 23 2009 10:11AM | Comments (2)
After seeing the role played by electrolytic capacitors in the lifetime of solar inverters and the importance of accurately derating them,, I asked the technical folks at AVX to talk about ceramic capacitors appropriate for another application that requires long lifetimes: LED lighting. Ron Demcko, application engineering manager at AVX, got back to me. Here’s Ron’s reply.
The perceived disparity between the life of LEDs (60,000 hours) and that of capacitors (perceived as 8000 hours) is a hot topic within the Solid State Lighting (SSL) world.
Many different types of capacitor technologies already exist that yield very reliable capacitors. Power film capacitors for example, have internal fuses with... + read more
Power supplies for new LED applications fit in higher-margin markets
Nov 18 2009 7:51PM | Comments (1)
There’s an emerging market for power supplies in LED lighting and signage. IC vendors are salivating over the huge market for LED bulbs to replace incandescent and CFL bulbs, which will all need their own ac/dc power ICs. But the largest bulb replacement market of all, replacing the 60W light bulb, will have razor-thin profit margins and most likely go straight to Asian manufacturers. A more promising market for US technology companies focusing on high-power LEDs is signage, displays, and industrial lighting.
You may have seen the Mitsubishi screen at the Dallas Cowboys’ stadium which is billed as the world’s largest LED video display.
This display uses 22,000 Lambda-TDK power supplies,... + read more
E-BOOK: Designing with LEDs Workshop
EDN’s recent Designing with LEDs workshop, held in Chicago, addressed topics such as power control, thermal management, optics and the impact of lighting control and communication on system cost and usability. To make this educational material available to those unable to attend, we have published workshop materials as an e-book. + view resource.
WEBCAST: LED Manufacturers' Panel
The Designing with LEDs workshop (4/30/09) had some of the foremost experts in these fields giving keynotes, papers, and workshops. This webcast allows you to hear the LED Manufacturers' Panel presentation as from the workshop. + view resource.
REFERENCE GUIDE: LED Design Library
Inductive LED driver reference designs are available for powering a wide variety of white LED types of multiple colors and configurations with high power efficiency. Many designs offer high output current, for multiple LEDs in series, LED flash, or high-power LEDs. + view resource.
