Switching Li-ion Battery Charging Chip Design Based On Constant Current/Constant Voltage

Development of computer and communication technology has greatly promoted the research, design and popularization of portable electronic products, which makes the market share occupied by portable electronic devices grow bigger and bigger. Especially in recent years, benefit from the convenience brought by the Internet, the smart phone market has developped persistently and rapidly. How to make portable devices work longer without increasing the battery size has become a widely concerned problem. Compared to other batteries, Li-ion battery has become the best choice of energy source for portable devices with its advantages in many aspects. However, except the manufacturing process but also battery charging method and the environment affected the cycle life of Li-ion battery. Therefore, using reasonable charging method and the charger with excellent performance is very important.A switching Li-ion battery charger based on constant current(CC)/constant voltage(CV) mode with novel structure presented by this thesis made the use of symmetry transconductance operational amplifier as charging current sampling signal amplifier and battery voltage sampling signal amplifier and shifted the mode from constant current to constant voltage smoothly in standard CMOS process. After the introduction of the lithium-ion battery performance and comparing the several different charging methods,the thesis analyzed the working principle of the chip, and according to the characteristics of the constant current charging loop and the constant voltage charging loop, the type III compensation network was adopted to compensate frequency characteristics of the two charging loop. In this thesis,the frequency characteristics of the two charging loops were simulated in Matlab and the constant current charging circuit and the constant voltage charging circuit system models with the voltage feedforward technology were built in Simulink.In this way, the stability of this system and the improvement of the dynamic response brougut by the voltage feedforward technology were verificated. After the design of the relevant sub-modules, the whole system circuit was built and simulated with other sub-modules which have been designed.The Li-ion battery charger presented by this thesis is a voltage-controlled switching regulator based on Buck type topology with the standard 0.5μm CMOS process. The charger is designed to be powered by the standard input voltage of 5V. The switching frequency is 1.5MHz. The charger could realize charge management of a single Li-ion battery and support charge models of trickle current, constant current, constant voltage and recharge. The trickle current is 0.12A; the constant current is 1.2A; the floating charge voltage is 4.2V; the recharge voltage is 4.05 V. The simulation results show that the Li-ion battery charger described in this thesis reaches the design targets.