In the circuit design with lithium battery as the power supply, it is required to integrate more and more complex mixed signal system into a chip with small area, which inevitably puts forward the problem of low voltage and low power consumption for digital and analog circuits.Therefore, lithium battery charging circuit and protection circuit design is very important.
Due to the high energy density of lithium batteries, in the state of overcharging, the battery temperature will increase energy surplus, so electrolyte decomposition and gas, easy to increase the internal pressure and the risk of spontaneous combustion or rupture;On the contrary, in the state of excessive discharge, electrolyte decomposition leads to deterioration of battery characteristics and durability, reducing the number of rechargeable times and shortening battery life.Therefore, the protection of lithium battery is very important, lithium battery applications must have battery protection chip, to prevent the battery over charge, over discharge and over current.
Lithium battery protection circuit needs to have the following functions:
(1) if the charging voltage exceeds the maximum allowable value of the battery, the battery discharge circuit can be provided.
(2) if the discharge voltage is lower than the minimum allowable value of the battery, the battery charging circuit can be provided. The connection between the battery and the external circuit is cut off, and the connection between the battery and the external circuit is cut off.
(3) if the charging and discharging current of lithium battery is greater than the limit value, cut off the connection between the battery and the external circuit.
(4) when the lithium battery returns to the normal state, the protection circuit should be able to corresponding release the protection state, so that the battery can continue to work normally.
Attention problems of lithium battery circuit design:
▲ lithium battery overcharge, overdischarge will affect the battery life.
▲ pay attention to the charging voltage and current of lithium batteries. Then select the appropriate charging chip.
▲ pay attention to prevent lithium battery overcharge, overdischarge, short circuit protection and other problems.
▲ the design goes through a lot of testing.