A high voltage battery charger with smooth charge mode transition in BCD process

A 60 V battery charger implemented using TSMC 0.25 μm Bipolar-CMOS-DMOS (BCD) 60 V process is presented in this work. A novel transition method is proposed to ensure smooth transitions between constant current (CC) and constant voltage (CV) modes. Since the proposed approach would require only additional diodes, power consumption and chip area are conserved in comparison with other sophisticated methods proposed in prior works. The charger sources a current of 50 mA in CC mode and has an efficiency of 75% ~ 80% throughout the charging sequence. The supply voltage is kept at 3 volts higher than the battery voltage throughout the charging sequence to maintain charging efficiency. A thermal protection circuit is included in this design to prevent the charger from operating at a temperature over the maximum allowed temperature.