Light-emitting diodes are being widely used due to their efficient use of power. The applications for power LEDs include traffic lights, street lamps, automotive lighting, architectural lights, household light replacements, signage lighting (replacing neon strip lights and fluorescent tubes), and many more. Powering (driving) these LED's is not always simple. Linear driving is inefficient and generates far too much heat. With a switching supply, the main issues are EMI and efficiency, and of course cost. The problem is to get a design that meets legal requirements and is efficient, while costing the least. This book covers the design trade-offs involved in LED driving applications, from low-power to UB-LEDs and beyond.