Self-Oscillating Electronic Ballast with Dimming Control

High-frequency electronic ballasts for gas discharge lamps are used widely in lighting systems today because of their merits of small size, light weight, high light luminous efficacy, long life, and no flicker no audible noise. In addition to numerous benefits over magnetic ballasts, electronic ballasts can provide dimming control, which is crucial nowadays in the energy-saving lighting systems.  Study shows that more than fifty percent energy savings can be achieved with dimming systems.  Besides the energy savings, dimming systems increase company's productivity by means of providing employees with personal control of workspace lighting and reducing glare at computer workstations.  Also the dimming system can provide flexibility and aesthetics such as changing the light levels for different activities, adding versatility to dining rooms, living rooms, home theaters, adapting the lighting in conference rooms, partitioning spaces for multiple purposes, dimming to create the perfect mood, and adding drama to your home, works of art and landscape. One big problem associated with the dimmable electronic ballast is the high cost.  Self-oscillating drive is usually employed to reduce the control complexity and the cost.  Disadvantageously, however, the operating of self-oscillating circuit is, by the nature of its operation, load dependent, and thus is hard to control and very sensitive to the variations of components.  Therefore, controlling circuit operation and reducing sensitivity poses a big challenge for the self-oscillating circuit.The invention proposes a novel self-oscillating scheme to solve above-mentioned problem.  It features high efficiency, good lamp current crest factor, constant and adjustable lamp power regulation, simple structure, and low cost.T he present invention is rather a very general concept, and could be applied to any type of self-oscillating switched-mode power supplies, such as buck, boost, buck-boost, fly-back or forward converters, push-pull converters, symmetrical or asymmetrical half-bridge converters or full-bridge converters to improve their performances.

Patent Information:
App Type Country Serial No. Patent No. File Date Issued Date Patent Status
US Utility *United States 10/014,800 6,696,803 12/14/2001 2/24/2004 Issued
Foreign Taiwan 092103464 228944 2/19/2003 3/1/2005 Issued
For Information, Contact:
Li Chen
Licensing Associate
Virginia Tech Intellectual Properties, Inc.
(540) 443-9217
Fengfeng Tao
Fred Lee