{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/141229"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/141229","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"GaN Device Characterization, Converter Optimization and Development for Enhanced Aviation Systems","abstract":"GaN device is one of the most promising candidates in high-efficiency and high-density power conversion applications. Due to the low ON-Resistance GaN devices are widely adopted in various soft-switching converters. Based on superior Baliga's Figure of Merit, GaN devices also have advantages over SiC and Si devices in hard switching conditions. However, the existence of dynamic $R_{DS(on)}$ weakens the advantage on the low conduction loss. The small footprint limits the heat dissipation ability hence the maximum switching frequency.Further improvement of power density may have constraints from passive components, which requires systematic optimization of GaN-based high-density converters.\\\\ By designing a multi-purpose testing platform, the dynamic $R_{DS(on)}$ of one GaN device is characterized under both DPT and soft-switching continuous tests, with different junction temperatures . Normalized $R_{DS(on)}$ is quantified and compared. The data can then be used to estimate extra loss from the dynamic $R_{DS(on)}$ under realistic power converter operating conditions.\\\\ The advantage of lower $R_{DS(on)}$ is especially prominent on low-Voltage rated GaN devices, which makes multi-level topology more preferable for GaN-based converters. A three-level Totem pole PFC converter for aircraft in-seat power supply is designed and optimized. The three-level topology enables the selection of the 200 V GaN device, leading to smaller conduction loss and a 98.4\\% peak efficiency. With the help of the PR compensator and input voltage feedforward, the phase-leading problem caused by the digital delay is greatly reduced and proven in 800Hz line frequency. The THD can meet the standard by doubling the sampling frequency and improving sensing. The EMI performance also meets the requirement with a one-stage filter at ac side and a common-mode inductor on the DC bus.\\\\ For inverter design of unmanned aerial vehicle applications where there's a lower voltage DC-link, two-level gains advantage over three level after systematic optimization and evaluation on the weight and loss. Paralleling up to four GaN devices effectively balanced the switching and conduction loss. By designing the power loop inductance to 0.11 nH, 100V GaN devices were safely operated under a 70 V DC bus with only a maximum 9.8 V overshoot. To prevent the inverter from short-circuit faults, the short-circuit protection based on the measurement of the voltage on the power loop inductor with a low-pass filter is successfully applied with only 115 ns protection time. The designed prototype shows expected thermal performance under rated 3.3 kVA power and survives a two-second 5.1 kVA transient power.","abstract_html":"GaN device is one of the most promising candidates in high-efficiency and high-density power conversion applications. Due to the low ON-Resistance GaN devices are widely adopted in various soft-switching converters. Based on superior Baliga&#x27;s Figure of Merit, GaN devices also have advantages over SiC and Si devices in hard switching conditions. However, the existence of dynamic <span class=\"etd-inline-math\">R<sub>DS(on)</sub></span> weakens the advantage on the low conduction loss. The small footprint limits the heat dissipation ability hence the maximum switching frequency.Further improvement of power density may have constraints from passive components, which requires systematic optimization of GaN-based high-density converters.\\\\ By designing a multi-purpose testing platform, the dynamic <span class=\"etd-inline-math\">R<sub>DS(on)</sub></span> of one GaN device is characterized under both DPT and soft-switching continuous tests, with different junction temperatures . Normalized <span class=\"etd-inline-math\">R<sub>DS(on)</sub></span> is quantified and compared. The data can then be used to estimate extra loss from the dynamic <span class=\"etd-inline-math\">R<sub>DS(on)</sub></span> under realistic power converter operating conditions.\\\\ The advantage of lower <span class=\"etd-inline-math\">R<sub>DS(on)</sub></span> is especially prominent on low-Voltage rated GaN devices, which makes multi-level topology more preferable for GaN-based converters. A three-level Totem pole PFC converter for aircraft in-seat power supply is designed and optimized. The three-level topology enables the selection of the 200 V GaN device, leading to smaller conduction loss and a 98.4\\% peak efficiency. With the help of the PR compensator and input voltage feedforward, the phase-leading problem caused by the digital delay is greatly reduced and proven in 800Hz line frequency. The THD can meet the standard by doubling the sampling frequency and improving sensing. The EMI performance also meets the requirement with a one-stage filter at ac side and a common-mode inductor on the DC bus.\\\\ For inverter design of unmanned aerial vehicle applications where there&#x27;s a lower voltage DC-link, two-level gains advantage over three level after systematic optimization and evaluation on the weight and loss. Paralleling up to four GaN devices effectively balanced the switching and conduction loss. By designing the power loop inductance to 0.11 nH, 100V GaN devices were safely operated under a 70 V DC bus with only a maximum 9.8 V overshoot. To prevent the inverter from short-circuit faults, the short-circuit protection based on the measurement of the voltage on the power loop inductor with a low-pass filter is successfully applied with only 115 ns protection time. The designed prototype shows expected thermal performance under rated 3.3 kVA power and survives a two-second 5.1 kVA transient power.","abstract_has_math":true,"creators":["Zhao, Tianyu"],"institution":"Virginia Tech","degree_name":"Doctor of Philosophy","degree_level":"doctoral","degree_discipline":"Electrical Engineering","degree_department":"Electrical Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":["Burgos, Rolando"],"committee_members":["Lu, Guo Quan","Zhang, Yuhao","Mehrizi-Sani, Ali","Dong, Dong"],"year":2026,"date_issued":"2026-02-10","date_published":"2026-02-10","updated_at":"2026-07-22T22:19:35Z","subjects":["GaN","Device Characterization","Optimization","AC-DC","DC-AC"],"languages":["en"],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45563"],"render_values":[{"text":"vt_gsexam:45563","href":null,"code":true}]}]},"links":{"outbound_url":"https://hdl.handle.net/10919/141229","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Burgos, Rolando"]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Lu, Guo Quan","Zhang, Yuhao","Mehrizi-Sani, Ali","Dong, Dong"]},{"key":"dc:contributor.department","label":"Department","values":["Electrical Engineering"]},{"key":"dc:creator","label":"Author","values":["Zhao, Tianyu"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-02-11T09:00:22Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2026-02-11T09:00:22Z"]},{"key":"dc:date.issued","label":"Date","values":["2026-02-10"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Electrical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Virginia Polytechnic Institute and State University"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["GaN","Device Characterization","Optimization","AC-DC","DC-AC"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["In Copyright"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://rightsstatements.org/vocab/InC/1.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["vt_gsexam:45563"]},{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/10919/141229"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["GaN device is one of the most promising candidates in high-efficiency and high-density power conversion applications. Due to the low ON-Resistance GaN devices are widely adopted in various soft-switching converters. Based on superior Baliga's Figure of Merit, GaN devices also have advantages over SiC and Si devices in hard switching conditions. However, the existence of dynamic $R_{DS(on)}$ weakens the advantage on the low conduction loss. The small footprint limits the heat dissipation ability hence the maximum switching frequency.Further improvement of power density may have constraints from passive components, which requires systematic optimization of GaN-based high-density converters.\\\\ By designing a multi-purpose testing platform, the dynamic $R_{DS(on)}$ of one GaN device is characterized under both DPT and soft-switching continuous tests, with different junction temperatures . Normalized $R_{DS(on)}$ is quantified and compared. The data can then be used to estimate extra loss from the dynamic $R_{DS(on)}$ under realistic power converter operating conditions.\\\\ The advantage of lower $R_{DS(on)}$ is especially prominent on low-Voltage rated GaN devices, which makes multi-level topology more preferable for GaN-based converters. A three-level Totem pole PFC converter for aircraft in-seat power supply is designed and optimized. The three-level topology enables the selection of the 200 V GaN device, leading to smaller conduction loss and a 98.4\\% peak efficiency. With the help of the PR compensator and input voltage feedforward, the phase-leading problem caused by the digital delay is greatly reduced and proven in 800Hz line frequency. The THD can meet the standard by doubling the sampling frequency and improving sensing. The EMI performance also meets the requirement with a one-stage filter at ac side and a common-mode inductor on the DC bus.\\\\ For inverter design of unmanned aerial vehicle applications where there's a lower voltage DC-link, two-level gains advantage over three level after systematic optimization and evaluation on the weight and loss. Paralleling up to four GaN devices effectively balanced the switching and conduction loss. By designing the power loop inductance to 0.11 nH, 100V GaN devices were safely operated under a 70 V DC bus with only a maximum 9.8 V overshoot. To prevent the inverter from short-circuit faults, the short-circuit protection based on the measurement of the voltage on the power loop inductor with a low-pass filter is successfully applied with only 115 ns protection time. The designed prototype shows expected thermal performance under rated 3.3 kVA power and survives a two-second 5.1 kVA transient power."]},{"key":"dc:description.abstractgeneral","label":"General Abstract","values":["Gallium nitride (GaN) power devices are emerging as a leading technology for making power converters smaller, lighter, and more energy efficient. Compared with traditional silicon and silicon carbide devices, GaN can switch faster and conduct electricity with lower losses, which enables higher power density and improved overall system performance. However, practical limitations—such as changes in device resistance during operation, limited heat dissipation due to small device size, and constraints from passive components—can reduce these benefits and limit further improvements in switching frequency and power density.\\\\ In this work, a flexible experimental platform is developed to accurately measure how GaN device resistance changes under realistic operating conditions and different temperatures. These measurements are used to quantify additional losses that occur in real power converters, providing designers with more accurate data for predicting performance and optimizing system efficiency.\\\\ The study also demonstrates how converter topology and system-level design choices can maximize the benefits of GaN devices. For an aircraft in-seat power supply, a three-level power factor correction (PFC) converter is designed to enable the use of lower-voltage GaN devices with very low resistance. This approach achieves a peak efficiency of 98.4\\% while meeting stringent requirements for power quality and electromagnetic interference at high line frequencies.\\\\ For unmanned aerial vehicle (UAV) inverter applications with lower operating voltages, a systematic comparison shows that a two-level topology is more advantageous in terms of weight and efficiency. By paralleling multiple GaN devices and carefully minimizing circuit inductance, the inverter achieves safe, reliable operation with fast protection against short-circuit faults. The prototype demonstrates strong thermal performance at rated power and successfully handles short-term overload conditions.\\\\ Overall, this work shows that combining accurate device characterization with careful system-level optimization is essential to fully realize the potential of GaN technology for next-generation high-density, high-efficiency power conversion systems."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Doctor of Philosophy"]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["ETD"]},{"key":"dc:title","label":"Title","values":["GaN Device Characterization, Converter Optimization and Development for Enhanced Aviation Systems"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Burgos, Rolando"],"dc:contributor.committeemember":["Lu, Guo Quan","Zhang, Yuhao","Mehrizi-Sani, Ali","Dong, Dong"],"dc:contributor.department":["Electrical Engineering"],"dc:creator":["Zhao, Tianyu"],"dc:date.accessioned":["2026-02-11T09:00:22Z"],"dc:date.available":["2026-02-11T09:00:22Z"],"dc:date.issued":["2026-02-10"],"dc:description.abstract":["GaN device is one of the most promising candidates in high-efficiency and high-density power conversion applications. Due to the low ON-Resistance GaN devices are widely adopted in various soft-switching converters. Based on superior Baliga's Figure of Merit, GaN devices also have advantages over SiC and Si devices in hard switching conditions. However, the existence of dynamic $R_{DS(on)}$ weakens the advantage on the low conduction loss. The small footprint limits the heat dissipation ability hence the maximum switching frequency.Further improvement of power density may have constraints from passive components, which requires systematic optimization of GaN-based high-density converters.\\\\ By designing a multi-purpose testing platform, the dynamic $R_{DS(on)}$ of one GaN device is characterized under both DPT and soft-switching continuous tests, with different junction temperatures . Normalized $R_{DS(on)}$ is quantified and compared. The data can then be used to estimate extra loss from the dynamic $R_{DS(on)}$ under realistic power converter operating conditions.\\\\ The advantage of lower $R_{DS(on)}$ is especially prominent on low-Voltage rated GaN devices, which makes multi-level topology more preferable for GaN-based converters. A three-level Totem pole PFC converter for aircraft in-seat power supply is designed and optimized. The three-level topology enables the selection of the 200 V GaN device, leading to smaller conduction loss and a 98.4\\% peak efficiency. With the help of the PR compensator and input voltage feedforward, the phase-leading problem caused by the digital delay is greatly reduced and proven in 800Hz line frequency. The THD can meet the standard by doubling the sampling frequency and improving sensing. The EMI performance also meets the requirement with a one-stage filter at ac side and a common-mode inductor on the DC bus.\\\\ For inverter design of unmanned aerial vehicle applications where there's a lower voltage DC-link, two-level gains advantage over three level after systematic optimization and evaluation on the weight and loss. Paralleling up to four GaN devices effectively balanced the switching and conduction loss. By designing the power loop inductance to 0.11 nH, 100V GaN devices were safely operated under a 70 V DC bus with only a maximum 9.8 V overshoot. To prevent the inverter from short-circuit faults, the short-circuit protection based on the measurement of the voltage on the power loop inductor with a low-pass filter is successfully applied with only 115 ns protection time. The designed prototype shows expected thermal performance under rated 3.3 kVA power and survives a two-second 5.1 kVA transient power."],"dc:description.abstractgeneral":["Gallium nitride (GaN) power devices are emerging as a leading technology for making power converters smaller, lighter, and more energy efficient. Compared with traditional silicon and silicon carbide devices, GaN can switch faster and conduct electricity with lower losses, which enables higher power density and improved overall system performance. However, practical limitations—such as changes in device resistance during operation, limited heat dissipation due to small device size, and constraints from passive components—can reduce these benefits and limit further improvements in switching frequency and power density.\\\\ In this work, a flexible experimental platform is developed to accurately measure how GaN device resistance changes under realistic operating conditions and different temperatures. These measurements are used to quantify additional losses that occur in real power converters, providing designers with more accurate data for predicting performance and optimizing system efficiency.\\\\ The study also demonstrates how converter topology and system-level design choices can maximize the benefits of GaN devices. For an aircraft in-seat power supply, a three-level power factor correction (PFC) converter is designed to enable the use of lower-voltage GaN devices with very low resistance. This approach achieves a peak efficiency of 98.4\\% while meeting stringent requirements for power quality and electromagnetic interference at high line frequencies.\\\\ For unmanned aerial vehicle (UAV) inverter applications with lower operating voltages, a systematic comparison shows that a two-level topology is more advantageous in terms of weight and efficiency. By paralleling multiple GaN devices and carefully minimizing circuit inductance, the inverter achieves safe, reliable operation with fast protection against short-circuit faults. The prototype demonstrates strong thermal performance at rated power and successfully handles short-term overload conditions.\\\\ Overall, this work shows that combining accurate device characterization with careful system-level optimization is essential to fully realize the potential of GaN technology for next-generation high-density, high-efficiency power conversion systems."],"dc:description.degree":["Doctor of Philosophy"],"dc:format.medium":["ETD"],"dc:identifier.other":["vt_gsexam:45563"],"dc:identifier.uri":["https://hdl.handle.net/10919/141229"],"dc:language.iso":["en"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["GaN","Device Characterization","Optimization","AC-DC","DC-AC"],"dc:title":["GaN Device Characterization, Converter Optimization and Development for Enhanced Aviation Systems"],"dc:type":["Dissertation"],"thesis:degree_discipline":["Electrical Engineering"],"thesis:degree_level":["doctoral"],"thesis:degree_name":["Doctor of Philosophy"],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:19:35Z"}