Over-current protection device for expansion cards

1. An over-current protection device, comprising:

a voltage input terminal;

a voltage output terminal;

a first resistor with a first end coupled to the voltage input terminal;

a second resistor;

an electronic switch comprising a control terminal, a first terminal coupled to the voltage output terminal, and a second terminal coupled to a second end of the first resistor, wherein the electronic switch is an N channel MOSFET, the control terminal, the first terminal, and the second terminal are gate, drain, and source of the electronic switch;

third, fourth, and fifth resistors coupled in series between a first end of the first transistor and ground; and

a control chip comprising a control pin coupled to the control terminal of the electronic switch and grounded through the second resistor, an input pin coupled the first end of the first resistor, a detecting pin coupled to the second end of the first resistor;

wherein the control chip compares a preset current value saved therein with a detecting current passing through the first resistor, and when the detecting current is greater than or equal to the preset current value, the electronic switch is turned off and no voltage is output from the voltage output terminal; wherein a node between the third resistor and the fourth resistor is coupled to a first input/output terminal of the control chip, and a node between the fourth resistor and the fifth resistor is coupled to a second input/output terminal of the control chip.

2. The protection device of claim 1 , wherein a sixth resistor is coupled between the control terminal of the electronic switch and the control pin of the control chip.

3. The protection device of claim 2 , wherein a seventh resistor is coupled between the voltage output terminal and a third input/output pin of the control chip.

4. The protection device of claim 1 , wherein an output pin of the control chip is coupled to the voltage output terminal.