A Driver Design for Retrofit LED Lamp

Abstract

LED lamp tubes are becoming more and more popular in recent light fixture market, especially fluorescent lamp tube replacement market. To replace a LED lamp tube directly with fluorescent lamp tube, a special design for LED driver compatible with the supply sources output by electronic ballast needs to be proposed. In this project, under the guidance of Professor Henry Chung and the help of his research group in Power Lab of CityU, a design of LED driver which can be embedded in LED lamp tube that can operate with electronic ballasts without rewiring the existing circuitry inside the fluorescent lamp holder is presented. Another feature of this LED driver is the function of dimming control. The kernel technology of this driver design to achieve the power conversion is the adjustment of the input impedance of AC-to-DC converter. Through this adjustment, the active and reactive power drawn from the electronic ballast to the LED lamp can be controlled. The concept of this retrofit design allows convenient replacement of fluorescent lamps with LED lamp tubes without removal or replacement of existing electronic ballasts. Once the prototype is commercialized and finally becomes real product, the market potential will be huge, since customers who could afford this kind of retrofit LED lamp must have used electronic ballasts before. A 20W retrofit LED lamp prototype is built, and the performance of it is evaluated in this project.