A Fast and Highly Accurate Battery Charger With Accurate Built-In Resistance Detection

This letter proposes a fast and highly accurate battery charger for mobile applications. The proposed battery charger accurately detects the built-in resistance (BIR) and determines the transition point from the constant-current (CC) to constant-voltage (CV) modes. It then maximizes and minimizes the durations of the CC and CV modes, respectively, thus reducing the battery charging time. In addition, the proposed charger accurately controls the charging current (
$I_{{\text{BAT}}}$
) by employing an adaptive
off
-time-controlled switching charger. The proposed battery charger was fabricated using a 0.18-μm standard CMOS process. The measurement results showed that with the use of the accurate BIR detection and adaptive
off
-time-control methods, the proposed charger reduced the total charging time by up to 41.2% and achieved
$I_{{\text{BAT}}}$
ripple of 52 mA
_p-p
.