The Research And Design Of One Cell Lithium-ion Battery Protection Circuit

With the increasing popularity of portable electronic devices in the world,the market of the batteries which are used as power supply of electronic devices is increasing hot.Compared with other rechargeable batteries like nickel cadmium batteries,nickel metal hydride batteries and so on,lithium batteries have the huge advantage of high energy density,and do not pollute the environment;they are much smaller and lighter;they can also adapt different environment temperatures.However,Lithium batteries will be damaged by entering the abnormal states when they are charging or discharging.We must put up the protection circuit to prevent the batteries from break-downing.In the meantime,the protection circuit should have the functions not only protect the batteries but also have the property of higher precision and lower power consumption.Therefore,a lower power consumption and higher precision Lithium battery protection chip that uses one MOSFET to control the charging and discharging circuits is designed in this paper.The chip brings much convenience for the work by integrating the MOSFET with the protection circuits together.It just need an external capacitance when it works.So the integration of the chip is much higher than other protection chips.In the meantime,the chip uses the trimming resistors network to make the precision of band-gap reference voltage much higher.In order to make the power consumption much lower,the chip has two kind of sleeping mode.On the normal working state,the current value is 6uA;On the sleeping working mode,the current value is 0.1 uA.There are band-gap-reference-voltage circuit,over-charge-voltage-protection circuit,over-discharge-voltage-protection circuit,over-charge-current-protection circuit,over-discharge-current-protection circuit,oscillator circuit and frequency-dividing circuit in the chip.At the same time,One over-temperature-protection circuit is also designed in the chip to prevent the chip from damaging by the high temperature.The chip uses 0.5um BCD manufacturing process of CSMC,and the Spectre software is used to simulate the circuit.All simulation of the basic function conform to the design requests.