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1. A Matrix Autotransformer Switched-Capacitor Converter for Data Center Application

   https://doi.org/10.1109/TPEL.2023.3308888  

   Qiu, Maohang; Wei, Mengxuan; Liu, Xiaoyan; Meng, Haoran; Cao, Dong (December 2023, IEEE Transactions on Power Electronics)

   This article proposes a matrix auto-transformer switched-capacitor dc–dc converter to achieve a high voltage conversion ratio, high efficiency, and high power density for 48-V data-center applications. On the high-voltage side, the proposed converter can fully leverage the benefits of high-performance low voltage stress devices similar to the multilevel modular switched-capacitor converter. Compared with the traditional isolated LLC converter with a matrix transformer, the proposed solution utilized a matrix autotransformer concept with merged primary and secondary side windings, thus leading to reduced transformer winding loss. The resonant inductor could be integrated into the transformer similar to the LLC converter. Because of the matrix autotransformer design, it can achieve a current doubler rectifier on the low voltage side. For less than 8-V low output voltage application, the current doubler rectifier design can fully utilize the best figure-of-merit 25-V device, which is more efficient than the full-bridge rectifier solution using two 25-V devices during the operation. All the devices can achieve zero voltage switching or zero current switching and can be naturally clamped without additional clamping circuits. A 500-W 48-V to 6-V dc–dc converter hardware prototype has been developed with optimized device selection and integrated matrix autotransformer design. Both simulation and experiment results have been provided to validate the features and benefits of the proposed converter. The maximum efficiency of the proposed converter can reach 98.33%. 

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2. Design and Experimental Study of a GaN-based Three-Port Multilevel Inverter

   https://doi.org/10.1109/IECON48115.2021.9589232  

   Tamasas Elrais, Mohamed; Batarseh, Issa. (October 2021, IECON 2021 – 47th Annual Conference of the IEEE Industrial Electronics Society)

   A three-port multilevel inverter with two DC ports and an AC port using Flying Capacitor Multilevel (FCML) design based on Gallium Nitride (GaN) switches is proposed in this paper. Recently, FCML inverter has shown a superior ability for power conversion with high power density, improved Total Harmonic Distortion (THD), and efficiency. The presented three-port multilevel inverter fits various applications such as battery and photovoltaic (PV) grid integration and standalone AC load. The proposed inverter is experimentally verified by building a 3-kW prototype using GaN switches which include two 4-level FCML converter paths, each share the same bus capacitor (C bus ), which links them together. One FCML path is 1 kW that incorporates an unfolder for the DC-to-AC conversion and has achieved a peak efficiency of 98.2% with AC voltage and current THDs of 1.26% and 1.23%, respectively. While the second FCML converter path is 2 kW used for the DC-to-DC conversion and has achieved a 99.43% peak efficiency. 

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3. A High Gain DC-DC Topology Based on Two-Winding Coupled Inductors Featuring Continuous Input Current

   https://doi.org/10.1109/ECCE44975.2020.9235400  

   Mahmoudi, Mohsen; Ajami, Ali; Babaei, Ebrahim; Abdolmaleki, Nima; Wang, Caisheng (October 2020, 2020 IEEE Energy Conversion Congress and Exposition (ECCE))

   null (Ed.)

   A high-voltage-gain dc-dc converter topology is proposed for renewable energy applications. The proposed coupled-inductor-based high-gain dc-dc converter features reduced input current ripple. The semiconductor elements voltage spikes due to the leakage inductance are prevented through the use of a clamping circuit. The Clamping circuit helps recover the leakage inductance stored energy, which causes voltage spikes on the switch. This results in the selection of elements with lower voltage ratings. Power switches with lower voltage ratings lead to lower conduction losses and improved system efficiency. The DC component of the inductor magnetizing current is zero. Consequently, no energy is stored in the inductor core, and the losses are further reduced. 

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4. A Comprehensive Analysis of Charge-Pump-Based Multi-Stage Multi-Output DC-DC Converters

   https://doi.org/10.1109/ISCAS51556.2021.9401129  

   Danesh, Ahmad Reza; Heydari, Payam (May 2021, IEEE International Symposium on Circuits and Systems)

   null (Ed.)

   This paper presents an analytical model for calculating the output voltage and the power efficiency of multi-stage multi-output (MSMO) DC-DC converters (DDC) that use charge pump cells for boosting the voltage. Various cases such as multi-output current consumption and its effects on the output voltage and the power efficiency are studied. Based on the model, a tapered design approach is proposed that can bolster the power efficiency and lower the output voltage drop of MSMO DDCs. Moreover, a charge-pump-based DDC is introduced and designed to verify the proposed model. Simulation results using a standard high-voltage 180-nm CMOS technology affirms the accuracy of the presented model. 

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5. A New High Step-Up DC-DC Topology with Zero DC Magnetizing Inductance Current and Continuous Input Current

   https://doi.org/10.1109/APEC39645.2020.9124151  

   Mahmoudi, Mohsen; Ajami, Ali; Babaei, Ebrahim; Abdolmaleki, Nima; Wang, Caisheng (March 2020, 2020 IEEE Applied Power Electronics Conference and Exposition (APEC))

   null (Ed.)

   A new high-voltage-gain non-isolated dc-dc topology for applications in renewable energies is proposed. A coupled inductor with three windings is used to increase the proposed topology voltage gain. In addition to increasing the voltage gain, the proposed topology also has other prominent features including continuous input current and zero dc magnetizing inductance current, which reduces the losses and size of coupled inductor core. Furthermore, the continuous input current guarantees a low-volume input filter, which is essential for renewable energy applications. The leakage inductor stored energy is recycled via the diode and capacitor and transferred to the converter output for increasing the efficiency and reducing voltage stresses on the converter components. 

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