why protection circuit ?

Lithium battery protection circuit

The lithium-ion battery energy density, it is difficult to ensure the safety of battery.

In the over-charged state, the battery temperature rise after excess energy, so electrolyte decomposition and produce gas, and because of increased internal pressure

Have the risk of spontaneous combustion or broken;

Conversely, excessive discha ge in the state, the result of decomposition of electrolyte battery characteristics and durability led to deterioration, resulting in lower number of charge cycles.

Lithium-ion battery protection circuit is to ensure that the excessive charge and discharge state security, and to prevent the degradation characteristics.

Lithium-ion battery protection circuit is protected by the IC and the two posed by the power MOSFET, which monitor the battery voltage protection IC, when

Recharge and discharge of excessive state to switch to the external power MOSFET to protect the battery protection IC function of charging excessive security

Conservation, protection and excessive discharge overcurrent / short circuit protection.