Design of piezoelectric transformer for PFC electronic ballast

In the ballast circuit, the piezoelectric transformer is used to replace the conventional inductor-capacitor resonant tank saving valuable space and cost. In the past, design of the piezoelectric transformer (PT) or Transoner^reg for the ballast circuit has been difficult due to the complex interaction between the physical and electrical equivalent circuit characteristics. Previous ballast design using the PT requires selecting available PT models normally not matched to the specific application and therefore, resulting in poor efficiency. In this paper, a design procedure was established for a PT tailored to a 32 W 120 V PFC electronic ballast. A prototype Transoner based on this design was fabricated by Face Electronics and tested experimentally. The experimental results showed that the ballast using the designed PT can achieve unit power factor, zero voltage switching and a 83 % overall efficiency