College of Engineering
Electrical Engineering Department
BS in Electrical Engineering
This project explores the rapidly-expanding area of AC direct drive for LED lighting. AC LED driving does not use typical DC-DC converter-based driving but uses semiconductor switches and a linear regulator to activate a number of LEDs proportional to the input voltage at any given time. This allows bulky, expensive magnetics to be eliminated from the system. The goal of this project was to develop a flexible simulation of a common AC LED system to find areas of significant power loss and attempt to improve them. This allows future versions of an AC LED system to start with major loss areas in mind, reducing development time and increasing performance. Systems tested included a three-stack binary switching system, a four-stack step-up switching system, a four-stack binary switching system, and a five-stack binary switching system. Through each simulation, the common theme was that the loss of the linear regulator was the dominant loss of the system. It was found that as the number of switches (and therefore switch states) increased, the loss of the MOSFET could be reduced significantly by reducing the voltage dropped across it. With three stacks using binary switching, MOSFET loss was 22.4W, or 29% of input power. With five switches, the MOSFET loss was reduced to 333mW, or less than 1% of input power.