High frequency planar power transformers for resonant converters

The authors present an alternative to the problem of high-frequency transformer design via the transmission line transformer (TLT). Utilizing transmission line circuit theory, they present the characteristics of the TLT for different turns ratios and discuss its advantages, including its wideband nature. TLT prototypes with ratios 2:1, 3:1, and 5:1 were designed and fabricated. The prototype test results verify the theoretical analysis and also point out the further advantages of compact size and high efficiency, making the TLT ideally suited for high-frequency converters