Protection Board is doing several things, fully automatic adjustment. We use such a metaphor, a person does not eat excessively hungry, and ate too much, is not good for your health. Therefore in order to ensure the mobile power batteries, not to the two extremes, so Protection Board on the design of a protection measure to avoid damage to the battery. Such as mobile power is full, you automatically turn off charge, and that protection is the same as the charger of mobile phone.
In addition protection Board also has an important function is the conversion rate. Such as charging batteries rated 5000mAh to user when not full 100% conversions. Your 1500mAh battery, mobile power 5000mAh rechargeable, filling three times more in theory, but in practice may not be able to fill. This is because the batteries, as well as in the charging process is the resistance of an object, it consumes a part. Protection Board acts as the roles, as far as possible to reduce internal resistance as well as optimization of IC circuit design can improve performance. Specific details of this IC or electronic knowledge.