Electrical and Thermal Design of High Efficiency and High Power Density Power Converters

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Yurek, Andrew
Power Electronics , High Power Density , Thermal Design , High Efficiency , Electrical Design
This thesis investigates high power density power converters from two approaches: electrical circuit and module design, and thermal management and mitigation. Three specific topics are studied in this thesis: Point-of-Load (POL) power module packaging, thermomechanical structures for high power density power converters, and single-stage resonant converters with Power Factor Correction (PFC) for the Electric Vehicle (EV) On-Board Charging (OBC) application. A new POL power module packaging structure called Power-System-in-Inductor (PSI2) is analyzed against traditional plastic packaging. PSI2 promises lower loss and higher package thermal conductivity by replacing a traditional plastic casing with the magnetic inductor core. Thermal analysis and FEA thermal simulation are conducted to verify the new packaging technology. Identical buck power modules are developed and tested experimentally. Simulation and experimentation show the PSI2 package achieves 2.68% greater efficiency, 0.51W less loss, and 26˚C lower top temperature compared to the traditionally plastic packaged module. Thermal conductivity of the PSI2 package accounts for about 33% of the improved thermal performance. A new thermomechanical structure is proposed named Integrated Multi-Layer Cooling (IMLC). The IMLC structure uses multiple-PCB layers, integrated active liquid cooling, and component sorting to achieve increased power density while maintaining thermal performance compared to a traditional single-PCB liquid cooled structure. FEA thermal simulation and experimentation with an EV Low-Voltage DC converter (LDC) show the IMLC structure achieves a 46°C peak temperature rise decrease and 0.6% improved efficiency over air cooled designs. Additionally, power density is improved by 31% compared to a single-PCB liquid cooled design. A single-stage LLC converter with PFC is designed for use in the EV OBC application. This topology promises improved power density, lower loss, and less complexity compared to traditional two-stage PFC designs by removing one switching converter stage. The circuit schematic and PCB layout are designed to achieve maximum power density and minimum loss. Simulation and experimental verification are conducted to verify the electrical performance and high-power density of 2.3kW/L of this topology. A high-power density, 1.65kW single-stage LLC OBC experimental prototype is designed which achieves 99.1% power factor and 96.9% efficiency at 1.47kW operation.
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