Research And Design Of A New Protection Circuit For Single Lithium Battery

In recent years,In terms of power supply options for electronic products,when it comes to other types of batteries,the advantages of lithium batteries are more obvious and the applications of lithium batteries are more extensive.However,in the actual application process of lithium batteries,excessive charging voltage,excessive discharge voltage,excessive discharge current,or short circuit may occur.At this time,the lithium battery may be damaged,and serious explosion may occur.In this way,the protection circuit of the lithium battery came into being.This article is designed for a single-cell lithium battery protection chip.Under normal circumstances,you can connect a charger to charge the battery or connect a load to discharge the battery.The chip has over-charge voltage protection,over-discharge voltage protection and discharge current Over-protection and short-circuit protection functions,each protection is set with an accurate protection voltage and corresponding protection delay time,and each protection has a corresponding recovery condition.At the same time,a resistor trimming network is used to improve the voltage accuracy,and a band gap reference circuit is used to reduce the influence of the power supply voltage and temperature on the circuit.Moreover,in practical applications,we only need a simple external circuit structure to achieve the charge and discharge protection function of lithium batteries.Compared with other lithium battery protection chips,this chip has a very simple internal structure,which is using integrated current and voltage detection module,the two pulse signals of the digital module control the voltage and current detection,the voltage and current detection are performed alternately,thereby reducing the size of the circuit and greatly improving the efficiency of the circuit.In the design of the voltage comparator,we did not use a general two-input comparator,but made a clever use of the relationship between the resistor divider module and the band gap reference to design a simple voltage comparator,and in the case of different reference voltages,only one comparator is required to complete the requirements of different voltage comparisons,which is not available in other lithium battery protection chips.The design of digital module is the most important part of the whole chip.It can generate the enable signals and delay signals needed by other modules in the chip.We use simple nand gate,or non gate,inverter,various triggers and oscillators to form these enable and delay signals.In the design of the oscillator,we verify the feasibility of the circuit oscillation according to the relationship between the baud diagram of the feedback system and the Barkhausen criterion.As for the recovery of over charging voltage,we can use not only the way of load discharge,but also the way of lithium battery self discharge,this design increases the diversity of the circuit.The design of this chip adopts 0.25um BCD process of China Resources Shanghua Company.In the cadence environment,the circuit is designed with virtuoso software,and the circuit is simulated with spectre simulator.In the end,the results of the circuit simulation are in line with expectations and reach design standards.