The inside of the charger is a switching power supply structure type circuit, which can not hear its high-frequency noise when it is working normally. When the working state changes, the switching frequency is reduced to the auditory range of the human ear, and the \"chirping and sizzling\" sound can be heard. There are the following possible reasons:
1, the mains is unstable, the AC voltage is too high, the internal circuit parameters of the charger are affected, and the working state is not normal;
2, the charger itself has a problem, when the load is full (to charge the phone), the circuit working state changes greatly, the circuit working frequency decreases;
3, when the mobile phone device has a short-circuit fault, the charger load exceeds its output capacity, the circuit working state will also change;
4, in this case, in order to avoid accidents, should immediately stop charging. Check whether it's the phone or the charger. It can be replaced with a normal charger to test the mobile phone and verify the faulty equipment.