Research And Design Of A Switching And Linear Mixed Mode Battery Charger

In this paper, the related theory of battery charger and its circuit principles areresearched in detail. Firstly, the methods of charging a battery are discussed, and thenseveral traditional topological structures of battery charger are introduced. Based on thetraditional topological structures, a novel frame of battery charger named XD1367isdesigned. The structure of the XD1367includes several loops. Each loop is theoreticallyanalyzed and the AC simulation is verified to ensure that all the loops are stable. Theelectrical characteristics of the XD1367are set in the paper. The whole functions of thechip are verified by transient simulation, all the simulation results comply with thedesign requirements.The XD1367uses a mixed structure which includes both a voltage mode buckDC-DC and a linear battery charger. The XD1367has the advantages in charging largecurrent and high efficiency, which is similar to the switching circuit. At the same time,the XD1367avoids the disadvantage of complex chip peripheral circuit. The XD1367can produce up to2.5A charge current and implement the efficiency as high as90%. Onthe other hand, similar to a linear charger，it has the benefit of high precision without thedrawback of generating great heat. It achieves1%charge voltage accuracy and5%charge current accuracy. In the XD1367, an N type MOSFET is used as the powerdevice, which reduces the chip area and increases the charge efficiency in low voltageeffectively. To drive the gate of the power MOSFET, a charge pump circuit is usedinnovatively.