Battery protection circuit and protection method thereof

1 . A battery protection circuit for protecting a battery cell from abnormal situations including overcharge, overdischarge and overcurrent, the battery protection circuit comprising:

a current sensing unit connected in series on a current output path formed between one terminal of the battery cell and an output unit to an external system, and configured to sense a current of the battery cell flowing in the current output path;

a voltage sensing unit connected to a voltage sensing line connected to both ends of the battery cell, the voltage sensing unit being configured to sense a voltage of the battery cell;

a voltage information transmission unit configured to transmit the voltage of the battery cell sensed by the voltage sensing unit to the external system;

a control unit configured to:

determine whether an abnormal situation occurs in the battery cell using the current sensed by the current sensing unit and the voltage sensed by the voltage sensing unit, and

disconnect the voltage sensing line according to the determination result; and

a sensing line blocking field effect transistor (FET) provided on the voltage sensing line and configured to be turned off under control of the control unit to disconnect the voltage sensing line,

wherein the control unit is configured to determine whether the battery cell has an abnormal situation by comparing the voltage of the battery cell to a predetermined first reference value and a predetermined second reference value different than the predetermined first reference value and by comparing the current of the battery cell measured by the current sensing unit to a predetermined third reference value different than the predetermined first reference value and the predetermined second reference value,

wherein the predetermined third reference value is an over current protection (OCP) value that is set lower than an overcurrent current, and

wherein when the voltage information transmission unit transmits 0 volts (V) voltage of the battery cell to the external system after the voltage sensing line is disconnected, the external system senses that the battery cell is in a low voltage state and turns off system power of the external system.

2 . The battery protection circuit of claim 1 , wherein the control unit comprises:

a first determination unit configured to:

compare whether the voltage of the battery cell sensed by the voltage sensing unit is equal to or greater than the predetermined first reference value, and

determine that the battery cell is in an overcharge state and output an overcharge signal when the voltage of the battery cell is greater than or equal to the predetermined first reference value;

a second determination unit configured to:

compare whether the voltage of the battery cell sensed by the voltage sensing unit is less than or equal to the predetermined second reference value, and

determine that the battery cell is in an over-discharge state and output an overdischarge signal when the voltage of the battery cell is less than or equal to the predetermined second reference value;

a third determination unit configured to:

compare whether the current of the battery cell sensed by the current sensing unit is equal to or greater than the predetermined third reference value, and

determine that the battery cell is in an overcurrent state and output an overcurrent signal when the current of the battery cell is equal to or greater than the predetermined third reference value; and

a blocking FET control unit configured to disconnect the voltage sensing line by turning off the sensing line blocking FET when any one of the overcharge signal, the overdischarge signal and the overcurrent signal is output by a respective one of the first determination unit, the second determination unit and the third determination unit.

3 . The battery protection circuit of claim 2 , wherein when the voltage sensing line is disconnected by the blocking FET control unit, the voltage of the battery cell sensed by the voltage sensing unit is 0 volts (V).

4 . A battery pack comprising the battery protection circuit according to claim 1 .

5 . The battery protection circuit of claim 1 , wherein the predetermined first reference value is an over voltage protection (OVP) value that is set lower than an overcharging voltage.

6 . The battery protection circuit of claim 1 , wherein the predetermined second reference value is an under voltage protection (UVP) value that is set higher than an over-discharging voltage.

7 . A method of protecting a battery cell from abnormal situations including overcharge, overdischarge and overcurrent, the method comprising:

a cell state information measurement step of measuring a current and a voltage of the battery cell at predetermined periodic intervals through a sensing resistor provided on a current output path between the battery cell and an output unit to an external system and a voltage sensing unit connected to a voltage sensing line connected to both ends of the battery cell;

an abnormal situation occurrence determination step of determining whether an abnormal situation occurs in the battery cell using the current and the voltage of the battery cell measured in the cell state information measurement step;

a voltage sensing line disconnection step of disconnecting the voltage sensing line when it is determined that the abnormal situation occurs in the battery cell by the abnormal situation occurrence determination step;

a cell voltage information transmission step of transmitting the voltage of the battery cell measured by the voltage sensing unit when the voltage sensing line is disconnected by the voltage sensing line disconnection step to the external system; and

an external system power off step of automatically turning off system power in the external system receiving the voltage of the battery cell measured by the voltage sensing unit during the cell voltage information transmission step,

wherein the abnormal situation occurrence determination step comprises comparing the voltage of the battery cell to a predetermined first reference value and a predetermined second reference value different than the predetermined first reference value and comparing the current of the battery cell measured by the sensing resistor to a predetermined third reference value different than the predetermined first reference value and the predetermined second reference value,

wherein the predetermined third reference value is an over current protection (OCP) value that is set lower than an overcurrent current, and

wherein the external system power off step senses that the current of the battery cell is in a low voltage state and turns off the system power when 0 volts (V) voltage of the battery cell is transmitted by the cell voltage information transmission step in the external system.

8 . The method of claim 7 , wherein the abnormal situation occurrence determination step further comprises:

an overcharge determination step of comparing whether the voltage of the battery cell measured in the cell state information measurement step is equal to or greater than the predetermined first reference value, and determining that the battery cell is in an overcharge state when the voltage of the battery cell is equal to or greater than the predetermined first reference value;

an overdischarge determination step of comparing whether the voltage of the battery cell measured in the cell state information measurement step is less than or equal to the predetermined second reference value, and determining that the battery cell is in an overdischarge state when the voltage of the battery cell is less than or equal to the predetermined second reference value; and

an overcurrent determination step of comparing whether the current of the battery cell measured in the cell state information measurement step is equal to or greater than the predetermined third reference value, and determining that the battery cell is in an overcurrent state when the current of the battery cell is equal to or greater than the predetermined third reference value, and

wherein when any one of the overcharge, the overdischarge and the overcurrent is determined, it is determined that the abnormal situation occurs in the battery cell.

9 . The method of claim 7 , wherein the voltage sensing line disconnection step comprises turning off a sensing line blocking field effect transistor (FET) disposed on the voltage sensing line.

10 . The method of claim 7 , wherein in the cell voltage information transmission step, the voltage of the battery cell transmitted to the external system is 0 volts (V).