Integrated EMI/Thermal Design for
Switching Power Supplies
Wei Zhang
Thesis submitted to the Faculty of the
Virginia Polytechnic Institute and State University
in partial fulfillment of the requirements for the degree of

Integrated EMI/Thermal Design for
Switching Power Supplies
Wei Zhang
(ABSTRACT)
This work presents the modeling and analysis of EMI and thermal performance
for switch power supply by using the CAD tools. The methodology and design guidelines
are developed.
By using a boost PFC circuit as an example, an equivalent circuit model is built
for EMI noise prediction and analysis. The parasitic elements of circuit layout and
components are extracted analytically or by using CAD tools. Based on the model, circuit
layout and magnetic component design are modified to minimize circuit EMI. EMI filter
can be designed at an early stage without prototype implementation.
In the second part, thermal analyses are conducted for the circuit by using the
software Flotherm, which includes the mechanism of conduction, convection and
radiation. Thermal models are built for the components. Thermal performance of the
circuit and the temperature profile of components are predicted. Improved thermal
management and winding arrangement are investigated to reduce temperature.
In the third part, several circuit layouts and inductor design examples are checked
from both the EMI and thermal point of view. Insightful information is obtained.