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38. A family of single‐phase boost AC‐AC converters based on impedance network cells with symmetric bipolar operation.

Author

Fathipour, Babak, Mousavi, Seyyed Mohammad Javad, and Babaei, Ebrahim

Subjects
*PASSIVE components, *BIPOLAR cells, *METAL oxide semiconductor field-effect transistors, *VOLTAGE, *DIODES, *ELECTRIC current rectifiers
Abstract

Summary: In this paper, a family of single‐phase boost AC‐AC converters based on impedance network cells with symmetric bipolar operation is proposed. The proposed converters exhibit a range of voltage gains as a result of non‐inverting and inverting boost operations, which are influenced by the input voltage and various impedance source cells. The converters leverage inherent commutation to address the commutation problem without requiring snubber circuits and safe commutation strategy. Additionally, high‐speed switching is achieved by preventing power MOSFETs' body diode conduction and related poor reverse recovery issues. The design incorporates a simple and flexible switching strategy to produce step‐change frequency at the output, using only four switches to achieve both step‐changed frequency operation and output voltage regulation. Furthermore, by reducing the total stored energy of passive components, the proposed converters effectively decrease volume, weight, and cost. The operational modes of the converters are elucidated, and their key relationships are summarized in tabular format. Finally, experimental validation through a laboratory prototype confirms the performance accuracy of the proposed converters at frequencies 25, 50, and 100 Hz. [ABSTRACT FROM AUTHOR]

Published
2025
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39. Evaluation of a New Patellar Tendon Bearing Brace With Offloading Monitoring and Adjustability: A Pilot Study.

Author

Chamani, Vahid, Bahramizadeh, Mahmood, Khosravi, Mobina, Biglarian, Akbar, Amjad, Gholamreza Ghorbani, Mousavi, Seyyed Mohammad Ebrahim, and Arazpour, Mokhtar

Subjects
PATELLAR tendon, TIBIA, CALVES, PILOT projects, ORTHOPEDIC braces, MEDICAL personnel
Abstract

Background and Aims: The patellar tendon‐bearing (PTB) brace is a crucial device designed to lessen axial forces on the tibia. The newly designed PTB brace allows clinicians to measure offloading amount in the realtime. This study aimed to explore the relationship between a rise in displacement between the foot plate and calf shells of this new PTB brace and changes in the amount of offloading on the tibia. Methods: This pilot study used a sample of five individuals with midshaft tibia fractures to investigate the effectiveness of the PTB brace under different conditions. The PTB brace was tested in six different conditions, with the displacement between the foot plate and calf shells varying in increments of 0.5 cm, from 1 cm to 3.5 cm. Results: The new PTB brace provided varying levels of offloading, ranging from 22% to 38%. As the vertical distance between the calf shells and foot plate increased, the offloading levels also increased significantly. The study observed significant differences in weight reduction (p = 0.02) and offloading percentages (p = 0.048) when comparing 1 cm and 1.5 cm displacement. Conclusion: The findings suggest that maintaining a distance of 1.5 cm or more between the calf shells and foot plate is effective in reducing weight and offloading on the tibia. These results have important implications for clinicians using PTB braces to treat tibia fractures, highlighting the importance of adjusting the displacement of the PTB brace to optimize patient outcomes. [ABSTRACT FROM AUTHOR]

Published
2024
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48. A Five-Switch Single-Phase Buck–Boost AC–AC Converter With Inherent Commutation and Continuous Input Current

Author

Zargariafshar, Deniz, Mousavi, Seyyed Mohammad Javad, and Babaei, Ebrahim

Abstract

In this article, a five-switch single-phase buck–boost ac–ac converter with inherent commutation and continuous input current is proposed. The proposed converter only requires five switches, which sets it apart from other nonisolated ac–ac buck–boost converters that have been presented so far. In addition, the number of energy storage elements in this converter has been reduced. Also, the output frequency can be changed as a multiple or fraction of the input frequency by symmetric noninverting and inverting operations of the proposed converter. The converter solves the commutation problem without the need for snubber circuits or safe commutation methods. It achieves inherent commutation without dividing the circuit structure into positive and negative switching cells. Another advantage of this converter is that it maintains a continuous input current and does not require an input LC filter. Comparing and analyzing the total switching devices power index and component volume, it can be concluded that this converter improves power density while reducing switching losses, size, and cost. The operating principle of the converter is explained through various operational modes, and the relevant relationships are calculated. The article provides a theoretical analysis and includes experimental validations conducted on a laboratory prototype with Po = 260 W and fs = 50 kHz.

Published
2025
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