Abstract
This paper presents the design and analysis of a high-density two-stage battery charger for mid-power applications like small electric vehicles and high-performance laptops utilizing gallium nitride (GaN) power devices. In addition to adherence of maximum junction temperatures, a thermal analysis is carried out for in-housing operation, which is particularly critical for fanless wall chargers. Design measures include calorimetric semiconductor selection, half-bridge miniaturization, thermally conductive epoxy resin and reference-based convection modeling for thermally optimized component placement using 3D-stacking. Furthermore, the remaining optimization potential of the charger is estimated by virtual prototyping. A 170 W hardware prototype is developed and tested, achieving a two-stage power section efficiency of 95.4% with a maximum switching frequency of 550 kHz. This results in a power density in open-housing operation of 1.6 kW/dm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{3}$</tex-math></inline-formula> . Using epoxy resin, copper and graphite heat spreaders, an in-housing operation power density of 1.1 kW/dm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{3}$</tex-math></inline-formula> is achieved with minor reduction of output power due to surface temperature constraints.
Highlights
W ITH the increasing acceptance and use of electric vehicles, the demand for compact, resource-saving battery chargers is growing [1], [2]
Corresponding applicationspecific integrated circuit (ASIC) controllers do not allow the optimization of the control system implemented in this work, but are significantly lower in loss overall
The results presented show that with additional measures such as thermally conductive epoxy resin and pyrolytic graphite sheets (PGS), the critical temperature limits of the standards can be met
Summary
W ITH the increasing acceptance and use of electric vehicles, the demand for compact, resource-saving battery chargers is growing [1], [2]. The influence of housing and component placement on the surface temperature is generally not considered when optimizing chargers in terms of power density [3]–[8]. It is not clear how much high-density charger designs are affected by these standards and to what extend packing density can be increased by measures such as potting and optimized component positioning. In contrast to prior research, this work demonstrates the charger operation in a plastic housing and points out the influence of surface temperature standards. Compared to optimization approaches of prior research [9]– [11], the temperature of the housing is identified as the limiting factor
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