Monolithic Linear Lithium Ion Battery Charger Ic Research And Design Of Intelligent Thermal Regulation

Li-ion battery is widely used in the portable application for its light weight, small size, high energy density and long life. Because the method of charging affects the Li-ion battery's life, charger must have the qualities of safety, reliability, fast speed and high efficiency. The chemic theory of Li-ion battery is studied in this paper. Based on the analysis of impacts on the performance of Li-ion battery with different charging methods and the consideration of cost, a monolithic linear Li-ion battery charger IC with intelligent thermal regulation is designed by CMOS process.The trickle charge mode and intelligent thermal regulation are added in the constant- current/constant-voltage charge mode in this paper. At the beginning of charge cycle, if the battery voltage is low (below 2.485V), the IC goes into trickle charge mode to bring the cell voltage up to a safe level for charging. The IC goes into the fast charge constant-current mode once the battery voltage rises above 2.485V. When the battery approaches the final float voltage, the charge current begins to decrease and the charge cycle switches to constant-voltage mode. The constant-voltage mode guarantees that the battery is fully charged. In the constant-current mode, the junction temperature rises rapidly for the excessive power dissipation when the input voltage is high and the battery voltage is low. When the temperature rises to about 105℃, the charge cycle goes into the intelligent thermal regulation mode. The IC can be protected in the charge proceeding because thermal regulation decreases the charge current and maintains the charger's temperature. Besides, the battery under and over temperature protection block, the battery status detection module, and the power supply status detection module are also added to the IC to ascertain that the IC works correctly. The methods above realize the intelligent control of the charging process. As to the charge current, the total charge time and the final float voltage design adopts programmable form to realize interactive management with users.The HSPICE tolerance simulation results prove that the IC can work correctly and its work is not sensitive to the change of process corner, power supply voltage in the range of 4.5V to 6V, temperature in the range of -40℃to 125℃. The final floating voltage of battery in the worst case is 4.1/4.2V±0.4% when the voltage reference is trimmed and 4.1/4.2V±0.8% when the voltage reference is not trimmed.