P-71: Cold Cathode Fluorescent Lamp Power Supply Based on Piezoelectric Transformers

This paper presents the design and test of a half bridge resonant power supply for low power cold cathode fluorescent lamps (CCFLs) that is based on piezoelectric transformers. The use of piezoelectric, instead of conventional magnetic, transformers allows a significant reduction of the converter's size and component count. The piezoelectric transformer allows the designer to directly connect the lamp to the secondary side of the device without the need for the typical ballast capacitor. Moreover, start up over-voltage is automatically generated without the need for input voltage amplitude or frequency modulation. On the other hand, high voltage, low current operation call for particular care in the implementation of the closed loop controller. The paper describes the different components and presents experimental results from a laboratory prototype of the converter.