Evaluating Piezoelectric Materials and Vibration Modes for Power Conversion

Abstract

Piezoelectric components offer several potential advantages to power conversion including high power density and efficiency capabilities compared to magnetics at small scales. Converter architectures have been developed for efficient utilization of piezoelectrics, but without fundamental criteria for designing the piezoelectric components themselves. In this paper, we derive figures of merit for the achievable efficiencies and power handling densities of piezoelectric materials and vibration modes based on realistic utilization in a power converter. These figures of merit are likewise accompanied by geometry conditions that serve as guidelines for high-efficiency, high-power-density piezoelectric resonator design. We demonstrate use of these metrics to evaluate commercially-available PZT and lithium niobate materials across seven vibration modes, and we validate the figures of merit and geometry conditions with numerical solutions of converter operation and experimental results. The proposed figures of merit are concluded to be highly representative metrics for the capabilities of piezoelectrics in power conversion, and these capabilities are shown to have favorable scaling properties for converter miniaturization.

A Stacked Piezoelectric Converter Using a Segmented IDT Lithium Niobate Resonator

“…The converter in this paper uses a thickness-shear mode resonator realized by interdigitated (IDT) metal electrodes on Y+163 • cut lithium niobate, a high performing material for piezoelectric power conversion [20]. Compared to thickness extensional mode resonators fabricated on lithium niobate, the shear mode has a higher piezoelectric coupling coefficient and lower wave velocity while achieving a similar mechanical quality factor.…”

Inductorless Step-Up Piezoelectric Resonator (SUPR) Converter: A Describing Function Analysis

“…Finally, by subtracting ( 16) from ( 17), and using (19) gives the first simultaneous equation 𝐽 1 in terms of circuit components and mode angles…”

“…A Python script for generating 𝑣 𝐶 p <1> using the SymPy library [28] is provided in the Appendix. The signal-based impedance can then be calculated using (19)…”

“…Based on the calculated mode angles and operating frequency, the output voltage and resonant current amplitude can be found, after which the 𝑣 𝐶 p waveform can be plotted. To find 𝑉 out , (19) is substituted in to (17)…”

“…Other work by Boles et al and Touhami et al focuses on optimal material choice for high power and high efficiency PRs [18], [19]. Authors have subsequently presented control schemes for the proposed PR converters, Piel et al [20] presented a simple feedback controller for a step-down converter topology presented in [14], based on either sensing the PR voltage or by using fixed time durations for each of the switching modes.…”