A charging system comprises an electronic device and a power adapter for charging the electronic device. The electronic device has a bi-directional communication with the power adapter; and the electronic device is arranged to send a health check command to the power adapter, and the power adapter performs a self-health check operation and reports a checking result to the electronic device. In addition, the electronic device may calculate a cable impedance, and control a compensation function of the power adapter by referring to the calculated cable impedance.