This paper introduces a new Tunable PiezoelectricTransformer (TPT) and demonstrates its operation in a dc-dcconverter application. Piezoelectric Transformers (PTs) havebeen conventionally used in high voltage, low power applicationssuch as electronic ballasts. Recently, radial type PTs have beendeveloped for higher power ac-dc and dc-dc step downapplications. Based on the latter, a new TPT has been developedfeaturing an auxiliary secondary terminal to control the voltagegain of the transformer. This results in some excitingcharacteristics from a dc-dc converter standpoint, like anadjustable frequency response of the TPT, and fixed frequencycontrol of the converter with no-cross talk between the primaryand secondary in the control circuit. This paper introduces thedesign concept behind TPT-based dc-dc converters, and proposesa control scheme for their implementation. Experimental resultswith a 30 W 220:55 V converter unit are shown to validate theseconcepts.
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