Kicking the tires on high-brightness LEDs

Seeing is believing: I find that’s certainly true for high-brightness (HB) LEDs, the LEDs with current ratings between 350mA and 1A that are finding use in everything from Las Vegas venue lighting to Times Square display signs to street lighting in Raleigh, NC. Joe Tillison, technology director at Avnet, sent me their HB LED evaluation kit that contains HB LEDs from Osram and Avago. I turned it on* and immediately ‘bout burned out an eye – the tiny LED die are intensely bright. But due to some recessive moth gene, my eyes are drawn to them. How can anything so tiny put out so much light?

However, the evaluation kit isn’t really about the LEDs – it’s about the STMicro VIPer12A current driver on the eval board. The board takes as input voltage 90 to 264VAC at 50/60 Hz, and outputs a selectable 350mA, 700mA, or 1.05A. I tried the different currents driving two HB LEDs in series (a white and a green) but didn’t see much difference in intensity — probably because my retina was pretty much incinerated at that point.

*Note that the eval board runs right off the ac mains, a configuration I really don’t like. I like stuff under 5VDC. I hesitate to get all Gollum-like here, but 120VAC is nasty, bitey things. Fortunately, I had an old SpeedStream router that I no longer use (having recently switched to Wildblue satellite service rather than iDSL) and was able to pull out the guts of the router box, leaving only the ac power cord connected to a nice friendly power switch, and a pcb power connector that just happened to fit the eval board. So that is why in the picture above the LED eval board seems to be running off of an elderly DSL router. Btw, the inspiration for recycling an old electronics enclosure came from watching Mark Thoren’s excellent video on building your own lab power supply.

Avnet’s site tells about a very cool-sounding HB LED that runs directly off ofAC. It’s from Korea and is called Acriche (pdf).