A 97.1%-Efficient Buck–Boost Battery Charger With Constant Current Extension and Precision-Adjustable Current Monitoring for 2× Faster Battery Charging

This paper presents a buck-boost battery charger incorporating the Constant Current Extension (CCE) technique for fast and accurate charging. By integrating the Precision Adjustable Charging Current Monitor (PACCM), the CCE technique significantly improves charging current sensing accuracy. The Adaptive Transistor Sizing (ATS) technique dynamically adjusts the power MOSFET size, effectively enhancing current gain and enabling the insertion of multiple constant current (CC) –like phases during constant voltage (CV) mode. This approach, combined with an enhanced built-in resistance detector, continuously minimizes CV charging time— achieving a 50.5% reduction—while ensuring precise charge termination. Thanks to ATS, the charger maintains high efficiency across a wide load range by optimizing MOSFET sizing and enabling accurate current regulation. The proposed design sustains over 90% efficiency from 50 mA to 5 A charging current, reaches a peak efficiency of 97.1%, and reduces output current and voltage ripple by 84%.