Design of Radial Mode Piezoelectric Transformers for Lamp Ballast Applications

In the past, radial-mode piezoelectric transformer (Transoner) design has been difficult due to the complex interaction between the physical and electrical circuit characteristics. Prior to a design procedure, experimental design by Face Electronics, LC led to a sample that could fit a ballast application enabling zero voltage switching (ZVS) for the semiconductors without the use of any external inductance.

In the ballast circuit, the piezoelectric transformer is used to replace the conventional inductor-capacitor resonant tank saving valuable space and expense. With ballast in mind, a design process has been developed in this thesis to optimize radial mode transformers to fit specifically tailored applications. The graphical process described, allows the engineer to design in the capability of zero voltage switching for a half-bridge drive while simultaneously providing highly efficient performance.

The problem of mounting a piezoelectric transformer to a circuit board has also been addressed in this thesis. A thermally conductive mounting technique has been developed which can enhance both the power capability and reliability of circuits utilizing these devices.