Power control system and method for controlling power adapter to input power to portable electronic device

A power control method, applicable for controlling a power adapter to input a power to a portable electronic device, wherein the power adapter comprises a first switch directly coupled to a power for controlling the power according to a plurality of logic states and a power circuit, and the portable electronic device comprises a latch coupled to the first switch, for latching the first switch according to the plurality of logic states and a controller for generating the plurality of logic states, and transmitting the plurality of logic states to the latch, the method comprising:

• a. receiving a power-off signal by the controller;
• b. detecting whether a battery is connected to the portable electronic device or not by the controller;
• c. if the battery is connected, further detecting whether an electric quantity of the battery has reached a reference value or not by the controller;
• d. if the electric quantity of the battery has not yet reached the reference value, enabling the latch to turn on the first switch, such that the power is provided to the power circuit for charging the battery;
• e. if the battery is not detected or the electric quantity of the battery has already reached the reference value, disabling the latch to turn off the first switch, so as to stop providing the power to the power circuit;
• and
• f. continuously detecting whether the battery is connected or not,
• if the battery is installed and connected, returning to Step c to continuously detect whether the electric quantity of the battery has reached the reference value or not, so as to turn on/off the first switch, and thus controlling the power circuit to provide the power.