Researchers develop LED driver with multilevel PWM

Researchers from The Hong Kong Polytechnic University (HKPU) have developed a new LED driver that powers LED light bulbs with an innovative approach called multilevel PWM (pulse-width modulation). The PWM is said to deliver remarkable improvements in terms of light quality and energy efficiency, when compared to pulse width modulation and linear driver approaches currently used in LED products.

Using the traditional method of pulse-width modulation, LEDs are fed pulsed current instead of steady DC. The drive current is turned on and off at a rate faster than that perceptible by human eyes. Powering LEDs in pulses makes their light output easily controllable.

Researchers have given the PWM method a new twist. The pulsed operation has been redesigned in a way to maximise light output while minimising wasted energy in the form of heat. The result is higher lumens per watt.

When used in a large-scale application, it can save a lot of energy. The LED billboard on One Times Square in New York is a good example. The maths goes like this: the giant display uses 12 million bulbs and 250 KW of power. If the billboard is on for 16 hours a day, the energy bill comes to US$18,000 a month. A 12% drop in energy consumption means US$2160 in energy savings.

Furthermore, it has lowered cooling requirements and needs a smaller-size heat sink compared to conventional methods. That means LED systems can be made smaller. With excellent dimming capability, the new MPWM driver allows manufacturers to create fully dimmable LEDs, which can be dimmed down to 0 watt of power. These superior qualities pave the way for brighter, smarter and more versatile LED lighting solutions.

This innovative applied technology, developed by Dr Lai Yuk Ming, Dr Loo Ka Hong and Prof Michael Tse, has already won a Gold Award at the 41st International Exhibition of Inventions of Geneva in April of 2013.