Quasi-Resonant LED driver with capacitive power transfer

You are invited to attend a lecture

By

Isar Reichman

(MSC student under the supervision of Dr. Alexander Abramovitz

and Prof. Doron Shmilovitz)

School of Electrical Engineering, Tel-Aviv University, Tel-Aviv 69978, Israel

Quasi-Resonant LED driver with capacitive power transfer

With the first red LED emerging in 1962 and green LED in 1972  LED technology have been around for the last 6 decades replacing the incandescent and neon lamps as indicator lamps and seven-segment displays. The invention of the blue LED lightning in Japan in the early 1990s triggered a fundamental transformation of lightning technology, and awarded the inventers with the Nobel prize in 2014. LED technology is about 5 times more energy efficient than the incandescent lighting and can offer longer service life. Hence, LEDs can reduce maintenance cost, help energy conservation and dramatically cut the COx polluting emissions. LEDs are durable, shock resistant, flicker free, emit directional light and can be dimed.

To operate a LED lighting fixture a specialized power converter, referred to as LED driver, is required. Offline LED lighting system presents several challenges. In these applications the LED driver has to perform ac dc conversion with large voltage step down, attain low distortion of the line current, and, for safety reasons, provide isolation. High efficiency alleviates heat management, helps minimizing the driver’s size and allows it to be fitted into congested spaces. LEDs prefer constant current operating conditions as thy usually connected in series. LED driver with current control can also provide precise dimming function. For these reasons some LED drivers are rather complex and are a major contributor to the cost of LED lighting systems. High performance and small size at acceptable cost can promote widespread use of LED lighting. However, lower cost usually requires compromises on performance .

This work will suggest a new LED driver topology that incorporate single active switch, zero voltage and current switching that decries losses on the switch, high frequency operation that enable the use of smaller components, inherent resistive input port characteristic that result with high power factor and by that eliminating the need for external power factor correction circuit and a simple dimming by Ton or duty cycle control. Full mathematical analysis was preform, delivering design equation and optimization verified with simulation and measurement, with full correlation.

Thursday, July 2, 2015, at 14:00

Room 011, kitot building