Unlike traditional lighting, LEDs require driver solutions that address the challenges of providing a constant current to a load whose output voltage can vary by ± 30% because of process and temperature effects. This application note and associated demo board will focus on driving multiple LEDs, at a regulated 350 mA, from low voltage DC or AC sources commonly used in lighting applications.
Due to the steep V/I curve of the LED and to achieve optimum performance, it is critical to drive LEDs with a constant current to achieve the specified brightness and color. For high brightness power LEDs, the specified current may be in the range 150 - 1500 mA, 350 mA being a common value. By combining LED manufacturer's data, taken from several product families, it is possible to come up with minimum and maximum forward voltage drops for a “generic” LED, operating at a specified current.