The investigation of the reason is the overvoltage protection circuit voltage distribution capacitance C180, C280, C380, c480 capacity will change with the change of temperature. Cause the protection circuit mistakenly trigger.
The correct technological transformation plan (need to change the circuit diagram, such as Figure)
1) the voltage distribution capacitance C280, C380, C180, C480 in the overvoltage protection sampling circuit are changed to the capacity of the ceramic chip, which is the capacity of the capacitor is 2200pF.
2) the anti interference capacitor MSCl691 of the 14 pin of the C120 is also replaced by the ceramic chip capacitor.. Content increased from 2200pF to 220pF.