Mitigating Duty Cycle Limitation and Maximizing DC Voltage Gain in Switch Mode Power Supplies Utilizing Tapped-Inductor Topology: A Case Study with Buck Converter Analysis

Abstract

This paper presents a comparative analysis of tapped inductor (TI) buck converters versus conventional buck converter topologies, highlighting the advantages of TI buck converters. The primary motivations for using TI DC-DC converters in step-down applications, such as battery charging and photovoltaic emulator design, include significant input-to-output voltage differences resulting in low converter duty cycles, favorable peak-to-average current ratios, and overall conversion efficiency. In conventional buck converters, the DC voltage gain is determined solely by the duty cycle, leading to linear output voltage variation with the duty cycle for a given input voltage. In contrast, the DC voltage gain of TI buck converters depends on both the duty cycle and the turns ratio. While the operating principles of conventional and TI buck converters are similar, the TI topology offers a wider range of voltage step-down options based on the TI turns ratio. System characteristics are analyzed using the transfer function model for ease of use and pole-zero detection. The state-space averaging method, known for its simplicity, is applied with AC small signal analysis to derive transfer functions for both converter types. The results show that the use of a tapped rather than a conventional inductor does not alter the step-down characteristics of the conventional buck converter. Moreover, any DC voltage gain consistent with the conventional buck converter condition can be achieved at any duty cycle value by appropriate selection of the turn’s ratio, increasing flexibility in converter design.

Keywords

• DC-DC power conversion
• buck converter-based emulator
• tapped inductor
• photovoltaic emulator
• duty cycle limitation
• DC voltage gain

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