SMPS Based 48V/8A Battery Charger (CV Mode) Constant Voltage

Abstract

This paper presents the design and implementation of a switch- mode power supply (SMPS) based battery charger delivering 48 V at 8 A with precise constant- voltage regulation. The charger employs a high- frequency, pulse- width- modulated (PWM) buck converter topology optimized for efficiency and compactness. Key features include a digital control loop using a microcontroller- based PID algorithm to maintain output voltage within ±0.5% under varying load and input conditions, and a programmable soft- start sequence to limit inrush current during connection. Input power factor correction (PFC) ensures compliance with international grid- compatibility standards, while synchronous rectification in the output stage achieves efficiencies exceeding 94%. Protection mechanisms, overvoltage, overcurrent, and thermal shutdown are integrated to ensure safe operation and battery longevity. Experimental results on a laboratory prototype demonstrate stable 48 V output with rapid response to load transients and an overall efficiency of 92.5% at full load. The modular design allows scalability to higher power levels, making it suitable for modern energy storage systems in telecommunications, electric vehicles, and renewable- energy applications.

Introduction

The text discusses the increasing demand for compact, efficient, and reliable battery chargers driven by the growth of high-power battery-powered systems like telecom backups, EV auxiliary packs, and renewable energy storage. Switch-mode power supplies (SMPS) have become the preferred technology due to their high efficiency, power density, and thermal performance. The paper focuses on designing a 48 V, 8 A SMPS-based battery charger using a high-frequency PWM buck converter controlled by a digital PID loop for precise voltage regulation. Features include programmable soft-start to limit inrush current, active power factor correction (PFC), synchronous rectification for efficiency above 94%, and robust protection mechanisms. Experimental results show 92.5% efficiency at full load and stable operation.

The literature review covers various SMPS topologies used in 48 V battery chargers—buck, two-stage PFC buck, and single-stage PFC converters—along with control strategies like digital PID, model predictive control, and machine learning-assisted control. Efficiency improvements through synchronous rectification and soft-switching, as well as protection and thermal management techniques, are also surveyed.

The existing methods section outlines common SMPS charger topologies: flyback (low power, isolated), buck (non-isolated, efficient step-down), boost/buck-boost (for varying input voltages), forward (medium-to-high power isolated), half/full-bridge (high power with advanced control), and resonant LLC converters (high efficiency, low EMI). Two-stage architectures combining AC-DC PFC and DC-DC converters provide modularity and improved performance. Control strategies center on constant current/constant voltage (CC/CV) methods, increasingly augmented by advanced digital controls for safety and battery longevity.

Finally, the methodology section briefly introduces the systematic development of the 48 V/8 A constant-voltage SMPS charger, from requirements through design and testing.

Conclusion

In conclusion, the developed SMPS- based 48 V/8 A constant- voltage battery charger successfully meets the rigorous demands of modern high- power energy- storage applications. By employing an interleaved boost PFC front end and a GaN- enhanced synchronous- rectified buck output stage, the design achieves a peak efficiency of 94% and maintains an input power factor above0.95. The microcontroller- driven digital control loops, comprising a voltage- mode PFC algorithm and a discrete- time PID for output regulation ensure tight voltage accuracy (±0.5%) and rapid transient response (<1 ms for 50% load steps). Programmable soft- start, comprehensive overvoltage/overcurrent protections, and thermal shutdown safeguards further enhance reliability and battery longevity. Experimentally validated on a compact, four layer PCB prototype, the charger demonstrates consistent performance across its full operating range, making it well- suited for telecommunications back-up systems, electric vehicle auxiliary packs, and renewable energy storage. The modular architecture also facilitates future scalability and multi- output configurations, providing a versatile blueprint for next- generation battery charging solutions.

References

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Copyright

Copyright © 2025 R. Valarmathi, K. Kamalesh, R. Karthi, M. Kishore, K. Lokeshwaran. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.