For some reason, the powers that be have decided to do roadworks on every major road leading out of my area of London. That means traffic has been diverted to two minor roads. Fair enough as the leaking Victorian water pipes need to be replaced. But what I don’t understand is why
- they all have to be done at the same time and
- the same exact section of the A4 that was dug up for the entire length of last summer is being dug up again — I’m not exaggerating… it literally is the same exact section.
Anyway, because this process has added an extra 20 minutes to my commute I’ve started to look past my fellow frustrated commuters to keep myself amused. While sitting through the third cycle of the light at Gillette Corner last night, I noticed that the red/green lights were really bright and then I realized that the old traffic lights at some point had been replaced with LEDs (light-emitting diodes). Normally I wouldn’t have taken a second look but recently I’ve taken to noticing lights and in particular LEDs.
- LED traffic light across the street from the Hampton Court train station. Image courtesy of me
- LED thermal analysis results — image courtesy of Voxdale.
Unless you’re designing LED lights you probably don’t notice them. But if you think about it they are everywhere: alarm clocks, TVs, car dashboards and lights … even the EXIT signs in buildings. They have slowly encroached on us because quite simply they are a good piece of kit. Besides being really efficient, LEDs offer a long operating life: depending on the manufacturer and type, useful life for white LEDs can range from approximately 6,000 hours to more than 50,000 hours in compare to 30,000 hours for fluorescent tubes and less than 2,000 hours for incandescent bulbs.
LEDs generate a fair amount of heat and if their diode junctions go above 120 deg C, then their lifetimes start to drop off rapidly and their output reduces ( in terms of lumens/Watt). Also, the internal operating temperature becomes an issue because even though LEDs are more efficient than incandescent lamps, they still give off 91% of the energy they consume as heat. Therefore, thermal management is critical to LED performance. Now from what I understand, the LED market is extremely competitive. LED manufacturers are devoting considerable resources to new devices and are making continual progress — in fact, some estimate that any new LED design is obsolete in 12 months. So progressive LED manufacturers have started using CFD software to manage these thermal issues.
If you’re involved with designing LEDs and would like to learn about solving their thermal challenges, then I’d like to recommend a couple of resources for you:
- Attend this free online seminar on July 7: Design for Longevity in Your Power LED Products. There are two sessions: 10 AM (London time) for Europe and 11:30 AM (US/Eastern time) for North America. This online presentation contains a lot of good advice. For additional information about this event or to register please click here.
- Download and read this free whitepaper from our TECHPUBS area: “Solving the System-Level Thermal Management Challenges of LEDs”
- And finally for all issues relating to thermal management, the best magazine IMHO is the Electronics Cooling magazine. Subscriptions are free and you can read archived issues at http://www.electronics-cooling.com. It really is a cool (I couldn’t resist the pun) source of information.
Until next time,