Modeling and Characterization of Series Connected Hybrid Transformers for Low-Profile Power Converters

Abstract

Compact and low profile power converters are the main business of today's power industry. A significant volume of a power converter is occupied by the power transformer. This article proposes a unique solution that would make the power converters low profile. Instead of designing a power converter by using a single bulky transformer, the solution proposed is to split the main bulky transformer into a number of low profile transformers. This not only reduces the total weight and volume of the converter but also the total transformer losses. The use of more than one transformer in series reduces the applied voltage on the transformers, which minimizes the required turns ratio and decreases the stress on the secondary rectifiers and filter elements. Moreover, the decrease in the applied voltage reduces the proportional loss per transformer and makes it possible to design a hybrid transformer by combining Litz wire and traces of a printed circuit board. The reduced copper loss and lower heat dissipation per transformer simplify thermal management. An analytical comparison is made between the utilization of a single transformer or a number of transformers. The procedure of splitting a volume of a single transformer into a number of small transformers has been comprehensively discussed. The idea is investigated both experimentally and in computer simulation for an example application of a phase shifted full bridge dc-dc converter. The converter is characterized up to a load power of 2.2 kW at V in = 400 V dc and V out = 48 V dc .To make the approach more practical, the transformers are modeled using the traditional analytical method. The design of the example application using the split transformer approach reduces the total transformer weight by 45%, compared to the traditional approach with a single transformer. The converter also shows good performance with a maximum efficiency of 96%. INDEX TERMS Series transformers, modeling of transformers, transformer design, isolated converter, medium power converter, low profile converter, ZVS converter, PSFB converter, lightweight converter.

Simulation optimal and design of 3-kW DC-DC converter for pure electric vehicles

“…Many scientific papers have studied power converters, 1–22 which include different circuit topologies, soft switching control methods, and transformer optimization methods. However, the output powers of power converters in these scientific papers were not large, and there have been no in-depth studies on the input voltage range.…”

“…The experimental results showed that the transformer could isolate an extra-high voltage and the scheme was feasible. Abu Bakar et al 13 proposed a flattening method to optimize the volume of power converters by connecting multiple transformers in series. The experimental results showed that their method optimized the weight of the transformer by 45% and that the converter efficiency was high.…”

Electromagnetic Characterization of Hyperconducting Aluminum Litz Wires at Cryogenic Temperatures

“…A Litz wire, comprising multiple insulated metal strands twisted or braided together, effectively mitigates highfrequency losses attributed to skin and proximity effects. As a result, Litz wires have gained traction in various power electronic applications, including power converters [18][19], wireless power transfer systems [20][21], electric motors, and generators [22][23]. Given the high-frequency environment in the AC windings of CEMs and electric aircraft drives, Al Litz wires have the potential to address the persistent challenge of AC losses encountered with HTS tapes, while exhibiting relatively lower DC loss compared to Cu Litz wires at cryo-temperatures.…”

LTCC-Based DC-DC Converter for Reduction of Switching Noise and Radiated Emissions

“…Additionally, the demand for flat and thin electronic devices such as laptops and televisions has been growing [4][5][6]. To small-volume, lightweight, and flat electronic devices, researchers have focused on developing a suitable power-conversion system [7][8][9]. Wide bandgap (WBG) semiconductors, such as gallium nitride (GaN) and silicon carbide (SiC), can be used in such power conversion systems.…”