Design and Implementation of a Two-Stage Resonant Converter for Wide Output Range Operation
Nicola Zanatta, Tommaso Caldognetto, Davide Biadene, G. Spiazzi, Paolo Mattavelli
Abstract
This article proposes and analyzes a two-stage isolated dc–dc converter for electric vehicle charging applications, where high efficiency over a wide range of battery voltages is required. It employs a first preregulation stage and a second half-bridge LLC stage, integrated with the first. The second stage is always operated at resonance, ensuring high efficiency. The first preregulation stage is responsible for the desired input-to-output voltage conversion ratio and the zero-voltage switching operation of all the switches. This allows low conversion losses even with voltages that may vary over a wide range. The article presents the conversion structure, the converter analysis, the design of the magnetic elements, and demonstrates the converter operation considering an experimental prototype interfacing a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${750\text{-}} \mathrm{V}$</tex-math></inline-formula> dc-link with an output bus with nominal voltage range <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${250} \mathrm{}$</tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${500}\, \mathrm{V}$</tex-math></inline-formula> . The implemented module is rated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${5}\,\text{kW}$</tex-math></inline-formula> and achieves a peak efficiency of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\boldsymbol{98.0\%}$</tex-math></inline-formula> at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${3\text{-}} \text{kW}$</tex-math></inline-formula> output power.