Since LEDs are a solid state component and require electronic circuits to emit light, a driver that transforms AC to DC current will be utilized in the light fixture and this will drive the need to look for a power supply with sufficient power and output characteristics. Most light designers have purchased an off-the-shelf AC to DC power supply based on these requirements and, for initial testing, it works well. Light comes on and the fixture works. Next step in the process is to take the fixture for regulatory testing. At this point, the marketing collateral is getting ready and the sales people are anxious to take the new fixture to market. A call from the regulatory testing house with news of the product not passing the standards however, sends everyone looking for a solution. Add an EMI filter, one would suggest, put EMI cores on the input wires another person would say. Meanwhile, the cost of the fixture starts climbing and what seemed to be a nice-off-the shelf inexpensive power supply requires add-ons to perform.
The longer life of LEDs of over 50,000 hours is very attractive to customers. However, the life of the LED driver also needs to be considered. Many think this is about mean time between failure (MTBF); however, this is not life expectancy. In most cases, MTBF is calculated based on component count and provides just one part of information on reliability and life expectancy. When selecting the optimum power supply for LED lighting, look for a power supply that is specifically designed for the demands of the LED and meets power and output voltage. Make sure it lists EN55015 for Electromagnetic Interference (EMI) compliance (Figure 1), has adequate life expectancy to match the life of the LEDs in the fixture and then move on to other requirements such as low leakage current for Canada, and meets IEC61000-3-2 class C for the European