Control circuit, connection line and control method thereof

1. A control circuit disposed in a connection line comprising a first power pin and a second power pin, comprising:

a native N-type transistor comprising a first gate, a first drain and a first source, wherein the first drain is coupled to the first power pin;

a first impedance unit coupled between the first source and the second power pin;

a second impedance unit coupled between the first drain and the first gate, wherein when the voltage level of the first power pin is equal to a first pre-determined level, the first gate of the native N-type transistor receives an adjusting signal to adjust an equivalent impedance of the native N-type transistor, wherein when the voltage level of the first power pin is increased to a second pre-determined level, the adjusting signal is changed from a first level to a second level such that the native N-type transistor increases the equivalent impedance to reduce a current passing through the native N-type transistor, and wherein the second pre-determined level is higher than the first pre-determined level;

a logic unit generating and adjusting a control signal according to the level of the first power pin; and

an adjustment unit generating the adjusting signal according to the control signal to adjust the equivalent impedance, wherein when a duration during which the voltage level of the first power pin is equal to the first pre-determined level is equal to a pre-determined period, the adjustment unit adjusts the equivalent impedance according to the control signal, and

wherein when the voltage level of the first power pin is unequal to the first pre-determined level or the duration during which the voltage level of the first power pin is equal to the first pre-determined level is unequal to the pre-determined period, the adjustment unit does not adjust the equivalent impedance according to the control signal.

2. The control circuit as claimed in claim 1 , wherein the adjustment unit comprises:

a N-type transistor comprising a second gate, a second drain and a second source, wherein the second gate receives the control signal, the second drain is coupled to the first gate, and the second source is coupled to the second power pin; and

a third impedance unit coupled between the second gate and the second source.

3. The control circuit as claimed in claim 1 , wherein the native N-type transistor has a threshold voltage less than 0 and the connection between the native N-type transistor and the second impedance unit forms a diode connection type.

4. A connection line comprising:

a connection port configured to couple to a host device and comprising a first power pin and a second power pin;

a native N-type transistor comprising a first gate, a first drain and a first source, wherein the first drain is coupled to the first power pin;

a first impedance unit coupled between the first source and the second power pin;

a second impedance unit coupled between the first drain and the first gate, wherein when the voltage level of the first power pin is equal to a first pre-determined level, the first gate of the native N-type transistor receives an adjusting signal to adjust an equivalent impedance of the native N-type transistor, wherein when the voltage level of the first power pin is increased to a second pre-determined level, the adjusting signal is changed from a first level to a second level such that the native N-type transistor increases the equivalent impedance to reduce a current passing through the native N-type transistor, and wherein the second pre-determined level is higher than the first pre-determined level;

a logic unit generating a control signal according to the voltage level of the first power pin; and

an adjustment unit generating the adjusting signal according to the control signal to adjust the equivalent impedance, wherein when a duration during which the voltage level of the first power pin is equal to the first pre-determined level is equal to a pre-determined period, the adjustment unit adjusts the equivalent impedance according to the control signal, and when the voltage level of the first power pin is unequal to the first pre-determined level or the duration during which the voltage level of the first power pin is equal to the first pre-determined level is unequal to the pre-determined period, the adjustment unit does not adjust the equivalent impedance according to the control signal.

5. The connection line as claimed in claim 4 , wherein the connection port is a USB Type-C port.

6. The connection line as claimed in claim 4 , wherein when the connection port is coupled to the host device, the host device provides a first voltage to the first power pin during a first period and provides a second voltage to the first power pin during a second period, and the equivalent impedance is adjusted during a third period, wherein the second voltage is greater than the first voltage.

7. The connection line as claimed in claim 4 , wherein the adjustment unit comprises:

a N-type transistor comprising a second gate, a second drain and a second source, wherein the second gate receives the control signal, the second drain is coupled to the first gate, and the second source is coupled to the second power line; and

a third impedance unit coupled between the second gate and the second source.

8. The connection line as claimed in claim 4 , wherein the native N-type transistor has a threshold voltage less than 0 and the connection between the native N-type transistor and the second impedance unit forms a diode connection type.