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What's The Difference Between High & Low Power LEDs?

Light emitting diodes have been familiar for a long time. They’re widely used in electrical appliances and, in the last few years, in TVs and computer monitors as well. LEDs have been used for displays, power and status indicators and much more. As small, robust light sources with low power consumption they were perfectly suited to those tasks. Recently they’ve branched out though, and started appearing as light sources in everything from pocket flashlights to car headlamps. That’s because as well as the standard low power variety, high power LEDs are now widely available and increasingly economical.

All LEDs are relatively efficient at turning electricity into light; watt for watt they release less heat than conventional bulbs or xenon lights. Because standard LEDs use very low current – usually measured in tens of milliamperes – almost no heat is released at all. That means they can be installed pretty much anywhere and no precautions have to be taken to avoid heat build-up. That’s a good thing, because one of the few flaws of LEDs is that they’re sensitive to heat. If the temperature rises much above 30°C performance can start to drop off sharply. At higher temperatures the lifespan of the LEDs is seriously reduced, and a sudden failure is more likely.

Heat sensitivity isn’t a problem with low power LEDs, but modern high power ones use a much higher current. Hundreds of milliamps is normal; some go over 1A. Even with their high efficiency that means a lot more heat is being produced, and unless it’s properly managed it’s likely the LEDs will fail pretty quickly – usually within seconds, in fact. High power LEDs will always be mounted on some kind of heat sink for this reason. Often it’s simply the casing of the device they’re in, like the body of a flashlight. LED light bulbs usually have a large heat sink built into the base.

Of course the most important difference between low and high power LEDs is the amount of light they put out. Low power ones emit a few lumens at most – usually in single figures - although newer white or blue ones can be slightly brighter. A typical 3W high power LED, on the other hand, will have a light flux of over 150 lumens and some very high end ones can exceed 1,000 lumens.

High power LEDs are also becoming much more efficient than low power ones. That’s mostly because the current drawn by low power ones is so small, and the heat problem so negligible, that it’s just not worth worrying about. A typical small LED uses about 50mW of power. When you’re running a lightbar with 60 high power LEDs in it you need to be a bit more concerned about efficiency, though. Better efficiency means less drain on your battery to provide the same level of light, so it’s a definite Good Thing.

Really, high power LEDs aren’t much different from the little ones in your car dashboard; they’re just a bit bigger. In the few years they’ve been about they’ve turned out to be a huge advance in lighting, though, and the technology keeps getting better. We think they’re going to be around for a while.