Power adapter for dynamically adjusting output voltage and power supply system with the same

摘要

A power adapter (10) includes a power converting circuit (100), a current detecting circuit (101), and a controlling unit (102). A charging voltage (V c ) with a constant voltage level is provided by the hub (12) through the connecting ports (120). The current detecting circuit (101) is used for detecting a load current (I load ) and outputting a corresponding current detecting signal (V i ). The load current (I load ) is transmitted from the power converting circuit (100) to the hub (12) through the power cable (11). A look-up table is stored in the controlling unit (102) for recording a relationship between the load current (I load ) and a voltage drop across an impedance (R r ) of the power cable (11). According to the current detecting signal (V i ) and the look-up table, the controlling unit (102) issues a feedback signal (V f ) to the power converting circuit (100). According to the feedback signal (V f ), a level of the output voltage (V out ) is dynamically adjusted to be equal to the sum of the voltage drop and the charging voltage (V c ).