Planar LTCC Transformers for High-Voltage Flyback Converters

Copyright © 2010 IEEE. Reprinted with permission from IEEE Transactions on Components and Packaging Technologies, Vol 33 No 2, June 2010.

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   Alexander W. Roesler, Member, IEEE, Joshua M. Schare, S. Jill Glass, Kevin G. Ewsuk, 
   George Slama, David Abel and Daryl Schofield
   IEEE Transactions on Components and Packaging Technologies, Vol 33 No 2, June 2010
This paper discusses the design and use of low temperature (850 ° to 950 °C) co-fired ceramic (LTCC) planar magnetic flyback transformers for applications that require conversion of a low-voltage to high-voltage (>100-V) with significant volumetric constraints. Measured performance and modeling results for multiple designs show that the LTCC flyback transformer design and construction impose serious limitations on the achievable coupling, and significantly impacts the transformer performance and output voltage. This paper discusses the impact of various design factors that can provide improved performance by increasing transformer coupling and output voltage. The experiments performed on prototype units demonstrate LTCC transformer designs capable of greater than 2-kV output. Finally, the paper investigates the effect of the LTCC microstructure on transformer insulation. Although this paper focuses on generating voltages in the kV range, the experimental characterization, and discussion presented in this paper apply to designs requiring lower voltage.