Charging method and portable electronic device using the same

A portable electronic device, comprising:

• a function module;
• a battery module coupled to the function module, configured to charge the function module;
• and
• a charging control module coupled to the battery module, configured to charge the battery module, wherein the charging control module detects a battery voltage and a charging current of the battery module and determines whether the portable electronic device operates at a constant current mode according to the battery voltage,
• while the portable electronic device operates at the constant current mode, the charging control module enters an over voltage protection charging loop and allows the battery module to be charged up at a maximum charging voltage, the charging control module leaves the over voltage protection charging loop while the charging current is smaller than a predetermined current, and the maximum charging voltage is set as a full charge voltage while leaving the over voltage protection charging loop,
• wherein in the over voltage protection charging loop, the charging control module gradually decreases the maximum charging voltage according to a comparison result between the battery voltage and an overcharging protection voltage.