Capacitorless Notch Resonant Converters for Miniaturized LLCLC Resonant Converters in Electric Vehicle Charging Applications

This paper aims to establish the foundation for miniaturizing EV chargers by integrating stray capacitances into the LLC-LC converter operation. Capacitors are an indispensable part of power electronics converters that are widely employed in electric vehicle (EV) chargers. They are, however, particularly prone to wear-out mechanisms and failure modes, contributing to increased monitoring and replacement costs for these systems. Traditionally, stray capacitance in power electronics has been perceived as unavoidable and undesirable. However, this paper challenges this conventional view by advocating for the integration of stray capacitance as intrinsic components within the system's topology, particularly in LLC resonant converters utilizing the notch resonant converter on their secondary side. By employing alternative materials with high dielectric constants, such as calcium copper titanate (CCTO), specific parasitic components, notably intra-capacitance, are intentionally enhanced. This innovative approach reduces the dependence on external discrete capacitors and facilitates the development of highly reliable converters for electric vehicles (EVs). A comparison between the conventional LLC resonant converter and LLC-LC resonant converter is established. Using the proposed concept, the LLC-LC converter requires fewer passive components and demonstrates advantages in protection against short circuit and heavy load conditions. To validate the proposed concepts, we have conducted Ansys Maxwell and Ansys Simplorer co-simulations, supported by both simulation results and theoretical analysis. The proposed LC notch resonant converter, with L<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> = 539.97 uH and C<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</inf> = 9.09 uF, showed good agreement between simulation data and the mathematical model detailed in the paper, thus validating the proposed design.