Fundamentals of Offline LED Drivers
While there have been tremendous advances in individual high-brightness LEDs, many applications such as area lighting, backlighting, or digital signage inherently require an array of multiple LEDs, where number of LEDs can be low (in single digits), or in the hundreds. The designer of such arrays must decide on a configuration topology--serial, parallel, or serial/parallel strings; and number of LEDs per string--which optimizes the balance among many conflicting technical issues for powering the LEDs efficiently and reliably.
This fundamentals course looks at the design issues and trade-offs associated with each configuration. It also examines options for powering the array and its configurations, including use of single, larger supply versus multiple smaller ones, choosing switching supplies versus LDOs, and thermal implications (basic efficiency as well as heat-source concentration). Finally, it looks at LED failure modes and what can be done to minimize their overall impact.