A ZCS/ZVS DC–DC Partial Power Converter With Reconfigurable H-Bridge and Variable Turns Ratio for an Integrated On-Board Charger
Niwton Gabriel Feliciani dos Santos, Jonatan Rafael Rakoski Zientarski, Mário Lúcio da Silva Martins
Abstract
Series-connected partial power converters (S-PPCs) present the advantage of reduced losses due to part of the load power be delivered without any processing, i.e., losslessly. The remaining amount of processed power is required to offer load voltage or current regulation and it is subject of switching and conduction losses. Hence, the efficiency of an S-PPC is quite dependent on keeping its voltage regulation range (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \Delta {v}$</tex-math></inline-formula>) as narrow as possible. For electric vehicles battery chargers, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \Delta {v}$</tex-math></inline-formula> must cover from discharged to full charged traction battery pack voltage values, which often cover a wide voltage range and, thus, may minimize the benefits in employing S-PPC. To maintain the S-PPC advantages for such a wider voltage regulation range, this article proposes a step-up/down S-PPC with a reconfigurable H-bridge and variable turns ratio for the dc–dc stage of an integrated on-board charger (OBC). This way, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \Delta {v}$</tex-math></inline-formula> is split into multiple regions, covering from narrow to wider portions that allows the design of the S-PPC to be optimized for the narrow <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \Delta {v}$</tex-math></inline-formula> during most of the constant current charging mode. This feature provides a significant efficiency improvement and it is achieved by using a tapped primary winding that allows the PWM switching pattern to be exchanged among the three primary-side H-bridge legs yielding in a set of three distinct transformer turns ratios specially designed to cover each region of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \Delta {v}$</tex-math></inline-formula> and reducing the current through the S-PPC. In addition, zero-current switching is achieved for the primary switches and zero-voltage switching for the secondary switches, which are ensured via two fixed-frequency modulation strategies, i.e., without any additional circuit component to suppress the high-voltage spikes across the primary switches. To validate the analyzes, a scale-down prototype was built for an OBC application example (2.2 kW), reaching a peak efficiency of 98.7% during charging.