Method and apparatus for detecting current using operational amplifier

1. A current detecting apparatus of a conductor comprising:

a shunt resistor connected to the conductor;

an operational amplifier connected to the shunt resistor;

a first resistor connected between the shunt resistor and a first input terminal of the operational amplifier;

a second resistor connected between the shunt resistor and a second input terminal of the operational amplifier;

a third resistor connected between a ground and the first input terminal of the operational amplifier; and

a fourth resistor connected between the ground and the second input terminal of the operational amplifier.

2. The current detecting apparatus of claim 1 , wherein the operational amplifier is a ground line operational amplifier.

3. The current detecting apparatus of claim 1 , wherein a resistance of the first resistor and a resistance of the second resistor are the same, and a resistance of the third resistor and a resistance of the fourth resistor are the same.

4. The current detecting apparatus of claim 1 , wherein a ratio of a resistance of the third resistor to a resistance of the first resistor is equal to a ratio of a resistance of the fourth resistor to a resistance of the second resistor.

5. The current detecting apparatus of claim 4 , wherein the ratio of the resistance of the third resistor to the resistance of the first resistor is set to be equal to or less than a predetermined threshold ratio value.

6. The current detecting apparatus of claim 5 , wherein the threshold ratio value is determined based on the maximum input possible voltage value of the operational amplifier.

7. A current detecting method of a conductor comprising:

applying a current to a shunt resistor connected to the conductor;

applying a voltage of a first end of the shunt resistor to a first input terminal of an operational amplifier by being voltage-divided through a first resistor and a third resistor, and applying a voltage of a second end of the shunt resistor to a second input terminal of the operational amplifier by being voltage-divided through a second resistor and a fourth resistor; and

determining the current of the conductor based on the voltage of an output terminal of the operational amplifier,

wherein the first resistor is connected between the shunt resistor and the first input terminal of the operational amplifier, the second resistor is connected between the shunt resistor and the second input terminal of the operational amplifier, the third resistor is connected between a ground and the first input terminal of the operational amplifier, and the fourth resistor is connected between the ground and the second input terminal of the operational amplifier.

8. The current detecting method of claim 7 , wherein the operational amplifier is a ground line operational amplifier.

9. The current detecting method of claim 7 , wherein a resistance of the first resistor and a resistance of the second resistor are the same, and a resistance of the third resistor and a resistance of the fourth resistor are the same.

10. The current detecting method of claim 7 , wherein a ratio of a resistance of the third resistor to a resistance of the first resistor is equal to a ratio of a resistance of the fourth resistor to a resistance of the second resistor.

11. The current detecting method of claim 10 , wherein the ratio of the resistance of the third resistor to the resistance of the first resistor is set to be equal to or less than a predetermined threshold ratio value.

12. The current detecting method of claim 11 , wherein the threshold ratio value is determined based on the maximum input possible voltage value of the operational amplifier.