{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/88081"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/88081","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Differential power processing for series-stacked processors","abstract":"The series-stacked architecture provides a method to increase power delivery efficiency to multiple processors. With a series-stack, differential power processing (DPP) is needed to ensure that processor voltages remain within design limits as the individual loads vary. This work demonstrates a switched-capacitor (SC) converter to balance a stack of four ARM Cortex-A8 based embedded computers. A model of a series-stack with no DPP is first discussed for the case when loads can be controlled with no power electronics. We investigate hard-switched and resonant modes of operation in a ladder SC DPP converter, implemented with GaN transistors. Excellent 5 V regulation of each embedded computer is demonstrated in a 4-series-stack configuration, with realistic computational workloads. Moreover, we demonstrate hot-swapping of individual computers with maintained voltage regulation at all nodes. A peak stack power delivery of 99.8% is demonstrated, and DPP switching frequencies from 250 kHz to 2 MHz. Finally, the reliability of a series-stacked system is compared to an electrically parallel system.","abstract_html":"The series-stacked architecture provides a method to increase power delivery efficiency to multiple processors. With a series-stack, differential power processing (DPP) is needed to ensure that processor voltages remain within design limits as the individual loads vary. This work demonstrates a switched-capacitor (SC) converter to balance a stack of four ARM Cortex-A8 based embedded computers. A model of a series-stack with no DPP is first discussed for the case when loads can be controlled with no power electronics. We investigate hard-switched and resonant modes of operation in a ladder SC DPP converter, implemented with GaN transistors. Excellent 5 V regulation of each embedded computer is demonstrated in a 4-series-stack configuration, with realistic computational workloads. Moreover, we demonstrate hot-swapping of individual computers with maintained voltage regulation at all nodes. A peak stack power delivery of 99.8% is demonstrated, and DPP switching frequencies from 250 kHz to 2 MHz. Finally, the reliability of a series-stacked system is compared to an electrically parallel system.","abstract_has_math":false,"creators":["Stillwell, Andrew R"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Electrical & Computer Engineering","degree_department":null,"school":null,"contributors":["Pilawa, Robert"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-09-29T20:38:39Z","date_published":"2015-09-29T20:38:39Z","updated_at":"2026-07-22T22:26:31Z","subjects":["power","switched-capacitor"],"languages":["en"],"rights":["Copyright 2015 Andrew Stillwell"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/88081","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Pilawa, Robert"]},{"key":"dc:creator","label":"Author","values":["Stillwell, Andrew R"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-09-29T20:38:39Z","2015-08","2015-07-21","2015-8"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical & Computer Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["power","switched-capacitor"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2015 Andrew Stillwell"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/88081"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The series-stacked architecture provides a method to increase power delivery efficiency to multiple processors. With a series-stack, differential power processing (DPP) is needed to ensure that processor voltages remain within design limits as the individual loads vary. This work demonstrates a switched-capacitor (SC) converter to balance a stack of four ARM Cortex-A8 based embedded computers. A model of a series-stack with no DPP is first discussed for the case when loads can be controlled with no power electronics. We investigate hard-switched and resonant modes of operation in a ladder SC DPP converter, implemented with GaN transistors. Excellent 5 V regulation of each embedded computer is demonstrated in a 4-series-stack configuration, with realistic computational workloads. Moreover, we demonstrate hot-swapping of individual computers with maintained voltage regulation at all nodes. A peak stack power delivery of 99.8% is demonstrated, and DPP switching frequencies from 250 kHz to 2 MHz. Finally, the reliability of a series-stacked system is compared to an electrically parallel system.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2015-09-29 without embargo terms","The student, Andrew Stillwell, accepted the attached license on 2015-07-17 at 16:25.","The student, Andrew Stillwell, submitted this Thesis for approval on 2015-07-17 at 16:32.","This Thesis was approved for publication on 2015-07-21 at 13:39.","DSpace SAF Submission Ingestion Package generated from Vireo submission #8546 on 2015-09-29 at 13:23:10","Made available in DSpace on 2015-09-29T20:38:39Z (GMT). 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A model of a series-stack with no DPP is first discussed for the case when loads can be controlled with no power electronics. We investigate hard-switched and resonant modes of operation in a ladder SC DPP converter, implemented with GaN transistors. Excellent 5 V regulation of each embedded computer is demonstrated in a 4-series-stack configuration, with realistic computational workloads. Moreover, we demonstrate hot-swapping of individual computers with maintained voltage regulation at all nodes. A peak stack power delivery of 99.8% is demonstrated, and DPP switching frequencies from 250 kHz to 2 MHz. Finally, the reliability of a series-stacked system is compared to an electrically parallel system.","Submission original under an indefinite embargo labeled 'Open Access'. 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