Design Of Li-Ion Battery Charger IC Based On CC/CV Approach

The development and prevalence of portable applications require better performance of rechargeable batteries, while the Li-Ion battery becomes the best choice of portable electronic products because of its unique advantages, such as high energy density, long circle life, high voltage and absence of memory effects. However, the comparative fragility of Li-Ion battery, for example, to overcharging and high temperature, imposes stringent charge requirements on chargers. As portable applications, the chargers should be compact, high efficient and accurate.In order to manage the charge process of Li-Ion battery, the design and implementation of a Li-Ion battery charge protection integrated circuit (IC) based on constant-current/constant-voltage (CC/CV) approach was presented. Controlling the gate voltage of PMOS power transistor through the competence of multiple control loops, the circuit realizes the constant-current, constant-voltage and thermal regulation charge mode, and automatic transitions between them, and, especially, fulfills the smooth transition from CC to CV mode through the gradual current draw method. To decrease the power loss and money cost, the IC was design using standard CMOS technique while the power transistor was integrated into the chip, and few external components are needed in application. The chip was implemented using CSMC 0.6μm 2p2m CMOS mix process. The simulation and test results verify the functions of the circuit to realize the required charge modes and the smooth transitions between them, and the voltages of batteries after charging are 4.14～4.22 V, fulfilling the accuracy of±1.5%.Chap I reviews the development of Li-Ion battery and its charger, and describes the content of this design. Chap II introduces the design flow and the tools used during the design, and some special points of the CSMC 0.6μm technique. The concrete circuit design is presented in Chap III, including the principle analysis of the charge modes, the realizations of circuit blocks and some special aspects to consider during the design of the IC. The simulation and test results of the IC are presented in Chap IV, and Chap V discusses some possible improvement to the charge management IC.