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

摘要

A power adapter includes a power converting circuit, a current detecting circuit, and a controlling unit. A charging voltage with a constant voltage level is provided by the hub through the connecting ports. The current detecting circuit is used for detecting a load current and outputting a corresponding current detecting signal. The load current is transmitted from the power converting circuit to the hub through the power cable. A look-up table is stored in the controlling unit for recording a relationship between the load current and a voltage drop across an impedance of the power cable. According to the current detecting signal and the look-up table, the controlling unit issues a feedback signal to the power converting circuit. According to the feedback signal, a level of the output voltage is dynamically adjusted to be equal to the sum of the voltage drop and the charging voltage.

主权项

1. A power adapter connectable with a hub through a power cable, said hub having plural connecting ports, said power adapter comprising:
a power converting circuit for receiving an input voltage and converting said input voltage into an output voltage, wherein said output voltage is outputted from an output terminal of said power adapter, and electric energy of said output voltage is transmitted to said hub through said power cable, so that a charging voltage with a constant voltage level is provided by said hub through said connecting ports; a current detecting circuit connected with said power converting circuit for detecting a load current and outputting a corresponding current detecting signal, wherein said load current is transmitted from said power converting circuit to said hub through said power cable; and a controlling unit connected with said current detecting circuit and said power converting circuit for receiving said current detecting signal, wherein a look-up table is stored in said controlling unit for recording a relationship between said load current and a voltage drop across an impedance of said power cable, wherein according to said current detecting signal and said look-up table, said controlling unit issues a feedback signal to said power converting circuit, wherein according to said feedback signal, said power converting circuit is driven to dynamically adjust a level of said output voltage to be equal to the sum of said voltage drop and said charging voltage; wherein said current detecting circuit comprises: a detecting resistor connected between said power converting circuit and said output terminal of said power adapter; an error amplifier comprising an inverting input terminal, a non-inverting input terminal and an output terminal, wherein said inverting input terminal of said error amplifier is connected with a first end of said detecting resistor and said power converting circuit through a first resistor, said non-inverting input terminal of said error amplifier is connected with a second end of said detecting resistor through a second resistor, and said output terminal of said error amplifier is connected with said controlling unit for outputting said current detecting signal.