Radial mode piezoelectric transformer design for fluorescent lamp ballast applications

In a ballast circuit, the piezoelectric transformer (PT) is used to replace the conventional inductor-capacitor resonant tank saving valuable space and cost. During circuit operation, a very high voltage is required to initially ignite the lamp while during sustained operation the voltage requirements are significantly reduced. With ballast in mind, a design process has been developed to optimize a radial mode piezoelectric transformer or Transoner^® to fit a specific application while simultaneously providing highly efficient performance and the capability to provide ZVS to the switches. The design procedure was verified by a custom-designed PT operating in a 32-W ballast.