University of California San Diego and CEA-Leti scientists have developed a ground-breaking piezoelectric-based DC-DC converter that unifies all power switches onto a single chip to increase power density. This new power topology, which extends beyond existing topologies, blends the advantages of piezoelectric converters with capacitive-based DC-DC converters.

The power converters the team developed are much smaller than the huge, bulky inductors currently used for this role. The devices could eventually be used for any type of DC-DC conversation, in everything from smart phones, to computers, to server farms and AR/VR headsets.ย 

The results were presented in the paper, โ€œAn Integrated Dual-side Series/Parallel Piezoelectric Resonator-based 20-to-2.2V DC-DC Converter Achieving a 310% Loss Reductionโ€, Feb. 20 at ISSCC 2024 in San Francisco.

โ€œThe Dual-side Series/Parallel Piezoelectric Resonator (DSPPR) is the first IC used for PR-based power conversion, and achieves up to 310% loss reduction over prior-art published and co-designed discrete designs for VCRs<0.125,โ€ the paper reports.

โ€œThis innovative approach enhances performance, especially at low voltage conversion ratiosโ€”an area where prior works struggled to sustain both high efficiency and optimal utilization of piezoelectric materials,โ€ said Patrick Mercier, a professor in the Department of Electrical and Computer Engineering at UC San Diego and a senior author of the paper.

The paper explains that a hybrid DSPPR converter exploits integrated circuitsโ€™ ability to offer sophisticated power stages in a small area compared to discrete designs, and enables efficient device operation at voltage conversion ratios (VCR) of less than 0.1.ย 

โ€œThe IC provides a distinct opportunity to consolidate all power switches onto a single chip, significantly diminishing the PCB footprint and enhancing phase-control precision,โ€ said Gael Pillonnet, scientific director of CEA-Letiโ€™s Silicon Component Division.

In addition, incorporating additional capacitive-based converter stages, both pre- and post- the piezoelectric DC-DC converter, contributes to performance improvement.ย 

โ€œThis strategic integration reduces the demand on piezoelectric material, resulting in a more compact converter with a notably smaller total volume. The marginal increase in additional capacitors, which is less than 10 percent, pales in comparison to the substantial gains facilitated by the proposed topology,โ€ Pillonnet said.

โ€œThe DC-DC converter, particularly in the low VCR range, which was a focus of our work, has widespread applications in various sectors, such as high-power computing servers, automotive systems, USB chargers, and battery-powered devices,โ€ said Wen-Chin Brian Liu, a Ph.D. student in Mercierโ€™s research group and the lead author of the paper.

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