High-Gain AC-DC Step-Up Converter Using Hybrid Piezo/Magnetic Electromechanical Transformer

This paper presents a hybrid electromechanical transformer that passively transfers electrical power between galvanically isolated ports by coupling electrodynamic and piezoelectric transducers. The use of these two complementary electromechanical transduction methods along with a high-Q mechanical resonance affords very large transformations of voltage at particular electrical frequencies. A chip-size prototype is designed, simulated, fabricated and experimentally characterized. The 7.6 mm x 7.6 mm x 1.65 mm device achieves an open-circuit voltage gain of 31.4 and 48.7 when operating as a step-up transformer at 729.5 Hz and 1015 Hz resonance frequencies, respectively. In one operational mode, the system shows a minimum power dissipation of only 0.9 mu W corresponding to a power conversion efficiency of 11.8%. A practical application of the hybrid transformer is demonstrated through an AC-DC step-up converter. When using a 1015 Hz input signal of only 209 mV(rms) and 2.4 mA(rms), the step-up converter outputs 5.3 VDC.