High-power backlight inverter for LCD-TV using piezoelectric transformers

A new design of a high-voltage, high-power backlight inverter based on piezoelectric transformer technology for large size LCD-TV is presented in this paper. The major goals of the backlight inverter design are to provide high enough voltage and power while keeping the cost low enough to compete with conventional coil transformers based designs. In order to achieve these goals, two innovative design thoughts are introduced here. The first one is an innovative rigid support method that supports the piezoelectric transformer on nodal points of the designed 2nd mode so as to suppress odd mode vibrations and to achive higher driving efficiency. The metallic rigid support also replaces traditional input wiring to lower the contact resistance for higher efficiency and lower temperature raise. The second innovative design is switching on rectified voltage from power line voltage (110/220V) directly. Thus, a single layer Rosen-type piezoelectric transformer (PT) can have enough gain to generate high voltage for very long CCFLs (Cold Cathode Fluorescent Lamps) used on LCD-TV instead of using higher cost multi-layer piezoelectric transformers. An piezoelectric transformer based inverter based on the above design thought were built and verified in this paper.