Thermal Design of Automotive Power Electronics

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Dr. Kovácsházy Tamás
Department of Measurement and Information Systems

The purpose of this diploma thesis is to create a thermal design for a specific automotive power electronics system, on which I worked at Robert Bosch Ltd., GS-TC department in Budapest. Our department is developing and testing automatic transmission control units as well as electric oil pumps for gasoline systems. The team I am working in is developing the control electronics of a brushless DC motor (BLDC motor) for an electric oil pump. We are responsible for both the power and control electronics.

Since this application is part of the automatic transmission, our module takes placeis located inside the gearbox. The highly aggressive transmission fluid is floating around our electronics, thus all the submodules has to be hermetically sealed. The resistance to excessive heat is also required, the ambient temperature can be over 130°C during lifetime.

Nowadays there is a rising need for BLDC applications with higher power and temperature tolerance. These needs affect both the power and control electronics, therefore new solutions are required. In order to serve these needs we can either turn to the continuously improving passive and semiconductor devices or to new thermal management techniques and concepts.

During this thesis my tasks are to present the current half-bridge construction and the different possibilities for improvement in the near future. I need to redesign the classic half-bridge motor control circuit and to make necessary calculations and simulations for the dissipation of the components. My upmost priority is to design for minimized dissipation in three different ambient temperatures, with a pre-defined load. I have to build both the old and the new design, then I can validate my calculations with measurements. After drawing the right conclusions I will be able to compare the thermal performance of the two systems with each other.


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