A new charger system approach: The current and voltage control loops

This paper presents a lithium-ion battery recharging circuit with an improved charger system topology for portable devices and handheld gadgets. The proposed charger topology uses an operational amplifier with NMOS input for a smooth transition between current control loop and voltage control loop and to control a power pass element device. Using the above-mentioned abilities, a complete charging process, consisting of three sub-processes; automatically trickle charge, constant current and constant voltage mode are implemented. In the proposed new charger system topology, the charging behaviors of the Li-ion battery can achieve a better charging performance and terminated automatically when fully charged. Simulation results show that the power pass element channel width is 40,000 μm which is less 60% from others design, is able to carry out the output voltage of 4.2 V, the maximum charging current reaches 1 A and the trickle charge is 10% of constant current. The new charger topology has been implemented using 0.18 μm CMOS process. Experimental result shows that the new charger design topology agrees with the charging behaviors from simulation results.