Power Adjustment Device and Charging System

A charging system includes a first device; a second device; and a power adjustment device including a DC-to-DC conversion unit; and a micro-control unit for receiving a charging instruction, a first power information of the first device and a second power information of the second device and performing the following steps: controlling the DC-to-DC conversion unit to convert a first supply current received by the first device into a first charging current according to the first power information and the second power information when the charging instruction instructs the first device to charge the second device; and controlling the DC-to-DC conversion unit to convert a second supply current received by the second device into a second charging current according to the first power information and the second power information when the charging instruction instructs the second device to charge the first device.