Optimum Phase Shift in the Self-Oscillating Loop for Piezoelectric-Transformer-Based Power Converters

Abstract

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A New Non-Isolated Low-Power Inductorless Piezoelectric DC–DC Converter

“…To find the maximum efficiency ηmax, the efficiency is expressed as a function of ∆I. Finally, the maximum output power is calculated using ( 19) by finding first the power that leads to the maximum efficiency (20). At the end, this leads to a very simple expression (21) for the maximum efficiency, which depends of the main piezoelectric parameters (C0, ω, R) and of the desired output gain G. This simple formula makes the pre-designing fast and reliable.…”

“…The consequence is a drop of efficiency for some operating points since the efficiency is decreasing severely when the driving frequency moves away from the converter resonance frequency [1] . Some control strategies, like those discussed in [19], [20] enable to operate at the optimum frequency but quantum control solution [19] is not inductorless and needs a bulky output capacitor. Moreover, the self-oscillating loop method [20] requires digital control and a piezoelectric current estimation.…”

“…Some control strategies, like those discussed in [19], [20] enable to operate at the optimum frequency but quantum control solution [19] is not inductorless and needs a bulky output capacitor. Moreover, the self-oscillating loop method [20] requires digital control and a piezoelectric current estimation. A control scheme using a tunable piezoelectric transformer (TPT) was described in [21].…”

Equivalent circuit parameter extraction of low‐capacitance high‐damping PTs

“…It is difficult to measure R accurately independent of our approach; therefore, it is beneficial to initially remove it from (7) and (8). At resonance (v 0 ), the RLC reduces to R, and the input impedance (output shorted) is equal to the input capacitance and damping resistance in parallel [see (1)]. Substituting (2) into (1) and rearranging for R yields…”

“…Introduction: Piezoelectric transformers (PTs), which can replace multiple passive components in low-power resonant converters, offer high-power density and efficiency due to their inherent, high-quality mechanical resonance. While presently unable to compete on cost with traditional designs, PTs are non-magnetic and can be designed to operate at high temperature, leading to use in several important applications [1,2].…”