Modern power electronics typically operate with switching frequencies in the tens of kilohertz to a few megahertz. SiC and GaN power switches promise to enable increasing these frequencies by an order of magnitude or more. Doing so would allow reducing the energy storage requirements for passive components, particularly transformers and inductors, which typically take up the largest portion of the volume of a power converter, and which are also responsible for much of the power loss, cost, and design difficulty in the converter. In principle, a smaller energy storage requirement should make these components smaller and lower in loss and cost. However, material, fabrication, and design constraints make it hard to achieve such improvements. These issues are reviewed and new results on design optimization of low profile air-core inductors and loss characterization of high-performance magnetic materials for 10 to 100 MHz are presented.
A new, low-profile, low-loss resonant converter transformer is proposed. Its design allows the absorption of the series inductor of the resonant converter through its leakage inductance. The windings are concentric with ferrite between them to control the leakage inductance. This arrangement offers electromagnetic interference (EMI) reduction compared to similar designs. Design software which optimizes the transformer inclusive of all of the resonant converter's load conditions is described. A design optimization for a 550 W inverter with a 20 mm tall transformer is presented and the resulting prototype is discussed. The results of large-signal power loss experiments are provided and indicate that measured results match well with predictions. Under reactive load, the results indicate an expected transformer efficiency of at least 98.20% at a load condition similar in magnitude to an actual operating point of the converter.
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