KR20160043543A

KR20160043543A - Protection circuit for battery

Info

Publication number: KR20160043543A
Application number: KR1020140137241A
Authority: KR
Inventors: 송윤귀; 정용재; 손상우; 이승형; 이주완; 이용섭
Original assignee: (주)샌버드
Priority date: 2014-10-13
Filing date: 2014-10-13
Publication date: 2016-04-22

Abstract

Provided is a protection circuit for a battery, capable of detecting a charging overcurrent and detecting a discharging overcurrent and a short circuit when overcharged. The protection circuit for the battery for controlling charging and discharging of the battery includes: a reference voltage circuit for generating a first reference voltage; an overcurrent detection unit for detecting an overcurrent state or a short circuit state of the battery; a charging control switch and a discharging control switch for breaking the overcurrent according to an output signal of the overcurrent detection unit; a parasitic diode turned on to allow a discharging current or a charging current to flow when the charging control switch or the discharging control switch is turned off to stop charging or discharging in case of the generation of the overcurrent; and a diode voltage detection unit for detecting a forward voltage of the parasitic diode and forming a second reference voltage by dividing the first reference voltage, wherein the overcurrent detection unit detects a state of the battery using a voltage of an overcurrent detection terminal and either the first reference voltage or the second reference voltage depending on the overcurrent state.

Description

[0001] The present invention relates to a protection circuit for a battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery protection circuit, and more particularly, to a battery protection circuit capable of detecting a discharge overcurrent and a short-circuit current even when overcharging and charging overcurrent are detected.

2. Description of the Related Art Portable electronic devices such as mobile phones, digital cameras, notebooks, and the like are widely used. Accordingly, batteries for supplying power for operating these portable electronic devices have been developed.

The battery may be provided in the form of a battery pack including a battery cell and a protection circuit for controlling charging and discharging of the battery cell. The battery can be classified into any one of a lithium ion (Li-ion) battery, a nickel cadmium (Ni-Cd) battery, and the like depending on the type of the battery cell. Such a battery cell can be recharged as a rechargeable secondary battery.

However, as the secondary battery has high energy density and high capacity, the characteristics of the battery become very sensitive and it is necessary to maximize the safety and reliability of the battery. That is, a secondary battery such as a lithium ion battery has a drawback in that its performance can not be exhibited unless a precise voltage current is managed, because there is a danger of ignition by overcharging and deterioration of characteristics due to overdischarge.

Therefore, in general, the battery is equipped with a protection circuit for preventing overcharging, overdischarging and overcurrent, and the protection circuit is attached to the rechargeable battery.

As described above, the protection circuit of the battery pack is provided with an overcharge protection function, an over discharge protection function, an over current protection function, and a normal charge / discharge function.

1 is a circuit diagram for explaining an overcurrent detection of a conventional battery protection circuit.

1, the overcurrent detection is generally divided into charge overcurrent detection 13, discharge overcurrent detection 14 and shortcircuit detection 15. The shortcircuit detection 15 operates like the discharge overcurrent detection 14 Consists of.

The charging overcurrent detection 13 detects the voltage drop of the current flowing through the charge and discharge control FETs M1 and M2 between the negative voltage 12 of the charger 17 and the negative voltage of the battery 10 to the VM terminal 22). When the voltage of the VM terminal 22 becomes lower than a predetermined charging overcurrent detection voltage, the charge control FET M1 is turned off by the signal of the logic circuit 16 to shut off the charging.

The discharge overcurrent detection 14 and the short detection 15 detect the voltage drop of the current in the charge and discharge control FETs M1 and M2 between the negative voltage 12 of the charger 17 and the negative voltage of the battery 10 to the VM terminal 22). When the voltage of the VM terminal 22 becomes higher than each preset detection voltage, the discharge control FET M2 is turned off by the signal of the logic circuit 16 to prevent the discharge and short circuit current from flowing to the battery 10 .

However, when the charging overcurrent or the overcharge is detected, the charge control FET M1 is turned off, and the parasitic diode D1 of the charge control FET M1 is turned on to make the discharge current to make the discharge current. In this case, the VM node rises by the forward voltage of the parasitic diode D1 and generally has a voltage of 0.6 V or more. Therefore, discharge overcurrent and short-circuit detection are usually excluded when charging over-current and over-discharge are detected.

Korean Patent Publication No. 10-2002-0068295

The present invention relates to a protection circuit capable of detecting a discharge overcurrent and a short circuit even when charging overcurrent or overcharge is detected. That is, it is an object of the present invention to provide a battery protection circuit capable of detecting discharge overcurrent and short circuit by detecting a parasitic diode which is turned on at the time of overcharging and raising a reference voltage of the discharge overcurrent and short circuit detecting circuit.

According to an aspect of the present invention, there is provided a battery protection circuit for controlling charging and discharging of a battery, the battery protection circuit comprising: a reference voltage circuit for generating a first reference voltage; An overcurrent detecting unit for detecting an overcurrent state or a shortcircuit state of the battery; A charge control switch and a discharge control switch for interrupting an overcurrent by an output signal of the overcurrent detection unit; A parasitic diode that is turned on to allow a discharge current or a charge current to flow when the charge control switch or the discharge control switch is turned off to interrupt charging or discharging when the overcurrent is generated; And a diode voltage detecting unit detecting a forward voltage of the parasitic diode and dividing the first reference voltage to form a second reference voltage, wherein the overcurrent detecting unit detects the first reference voltage and the second reference voltage according to the overcurrent state, Wherein the state of the battery is detected using one of the reference voltages and the voltage of the overcurrent detection terminal.

According to the present invention, by detecting a parasitic diode generated during charging over-current and over-charging, the reference voltage of the discharge over-current and short-circuit detecting circuit is raised, so that discharge over-current and short circuit can be detected even in overcharge and overcharge.

1 is a circuit diagram for explaining an overcurrent detection of a conventional battery protection circuit.
2 is a block diagram illustrating a battery protection circuit according to an embodiment of the present invention.
3 is a circuit diagram for explaining discharge overcurrent detection and short circuit detection according to an embodiment of the present invention.
4 is a circuit diagram for explaining discharge overcurrent detection and short circuit detection according to the first embodiment of the present invention.
5 is a circuit diagram for explaining discharge overcurrent detection and short circuit detection according to a second embodiment of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is capable of various modifications and various embodiments, and specific embodiments are illustrated in the drawings and described in detail in the detailed description. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Referring to the accompanying drawings, the same or corresponding components are denoted by the same reference numerals, .

2 is a block diagram illustrating a battery protection circuit according to an embodiment of the present invention.

Referring to FIG. 2, the battery 101 supplies power stored in the electronic device in which the battery pack 100 is mounted. Also, when the charger is connected to the battery pack 100, the battery 101 can be charged with external power. The battery 101 cell may be a rechargeable secondary battery such as a nickel-cadmium battery, a lead acid battery, a nickel-hydrogen battery, a lithium ion battery, and a lithium polymer battery.

The battery 101 is connected in parallel with a resistor R11 and a capacitor C11 connected in series and the positive electrode is connected to the external positive electrode terminal 102 by wiring and the negative electrode is connected to a charge control And is connected to the external negative electrode terminal 103 using a switch and a discharge control switch.

The charge control switch includes a first field effect transistor M11 and a first parasitic diode D11 and supplies a current flow from the external positive terminal 102 to the battery 101 or from the battery 101 to the external negative terminal 103 Respectively. That is, the first field effect transistor M11 is used to block the charging current from flowing. At this time, a first field effect transistor M11 is formed so that a discharge current can flow through the first parasitic diode D11.

The discharge control switch includes a second field effect transistor M12 and a second parasitic diode D12 and supplies a current flow from the external negative electrode terminal 103 to the external positive electrode terminal 102 from the battery 101 or the battery 101. [ Respectively. That is, the second field effect transistor M12 is used to block the discharge current from flowing. At this time, the second field effect transistor M12 is formed so that the charging current can flow through the second parasitic diode D12.

The first field effect transistor M11 and the second field effect transistor M12 are connected in common to the drain electrode and the source terminal of the first field effect transistor M11 is connected to the external negative electrode terminal 103, The source terminal of the second field effect transistor M12 is connected to the cathode of the battery 101. [

The protection circuit 104 includes an overcharge detection circuit 110, an over discharge detection circuit 111, a discharge over current detection circuit 112, a charge over current detection circuit 113 and a short detection circuit 114.

Overcharge detection of the battery 101 is detected by the overcharge detection circuit 110. [ The voltage of the battery 101 is input through the VDD terminal 105, and when the overcharge detection voltage is higher than the preset overcharge detection voltage, the overcharge is detected. The detected overcharge signal is transmitted to the logic circuit 118 and the oscillator 116 and the frequency divider 117 are operated to change the output of the COUT terminal 108 from a high level to a low level after a predetermined delay time, The effect transistor M11 is turned off to shut off the charging of the battery 101. [

The discharge current continues to flow through the first parasitic diode D11 of the first field effect transistor M11 even when overcharging is detected and charging is interrupted.

When the voltage of the VDD terminal 105 becomes lower than the overcharge release voltage, the output of the COUT terminal 108 is changed from the low level to the high level and the first field effect transistor M11 is turned on to charge the battery 101 .

The overdischarge detection of the battery 101 is detected by the overdischarge detection circuit 111. [ The voltage of the battery 101 is input through the VDD terminal 105, and when the overdischarge detection voltage is lower than a predetermined overdischarge detection voltage, overdischarge is detected. The detected overdrive signal is transmitted to the logic circuit 118 and the oscillator 116 and the frequency divider 117 are operated to change the output of the DOUT terminal 107 from the high level to the low level after a predetermined delay time, The field effect transistor M12 is turned off to shut off the discharge of the battery 101. [

The charging current flows through the second parasitic diode D12 of the second field effect transistor M12 even when over discharge is detected and the discharge is blocked.

When the voltage of the VDD terminal 105 is higher than the overdischarge detection voltage, the output of the DOUT terminal 107 is changed to the high level and the second field effect transistor M12 is turned on to discharge the battery 101. [

The discharge overcurrent detection detects the discharge overcurrent when the discharge overcurrent detection circuit 112 detects the voltage of the V- terminal 109 and becomes higher than a preset discharge overcurrent detection voltage. The detected discharge overcurrent signal is transmitted to the logic circuit 118, and the output of the DOUT terminal 107 is changed from the high level to the low level to turn off the second field effect transistor M12 to shut off the discharge.

The discharging overcurrent cancellation resistance R12 maintains the off state by the second field effect transistor M12 when the battery 101 operates in the steady state and when the discharge overcurrent or short circuit current is detected, the second field effect transistor M12 Is turned on and the VSS terminal 106 and the V- terminal 109 are connected through the resistor R12. At this time, if the load is not connected, the voltage of the V- terminal 109 is lowered and the discharging overcurrent state or the short-circuit current state is automatically canceled.

The charging over-current detection detects the charging over-current when the charging over-current detection circuit 113 detects the voltage of the V- terminal 109 and becomes lower than a preset discharge over-current detection voltage. The detected charge overcurrent signal is transmitted to the logic circuit 118 and changes the output of the COUT terminal 108 from a high level to a low level to turn off the first field effect transistor M11 to shut off charging.

The short-circuit current detection detects the voltage of the V- terminal 109 when the battery 101 is charged or discharged in the short-circuit current circuit. When a large current flows instantaneously due to the short-circuit of the external load, the voltage of the V- terminal 109 becomes higher than the short-circuit detection voltage, and the short-circuit detection signal is transmitted to the logic circuit 118. At this time, the output of the DOUT terminal 107 changes from a high level to a low level to turn off the second field effect transistor M12 to block the short-circuit current from flowing.

Although the discharge overcurrent detection, charge overcurrent detection and shortcurrent detection both have a delay time due to the signal transmitted from the distributor 117 to the logic circuit 118, the shortcircuit current is much shorter than the discharge overcurrent, And has a delay time.

The operation of the general protection circuit 104 described above is such that it can not detect discharge overcurrent and short-circuit current when overcharge or over-charge is detected. However, since discharging overcurrent and short circuit detection seriously affect the safety of the battery when discharging proceeds, discharge overcurrent and short-circuit current detection are required even when overcharge or charging overcurrent is detected.

3 is a circuit diagram for explaining discharge overcurrent detection and short circuit detection according to an embodiment of the present invention.

3, the first voltage dividing circuit 201 for dividing the reference voltage of the over-discharge detecting circuit 203 and the short-circuit detecting circuit 202 includes first changing means M21, The discharge overcurrent detection 203 and the short circuit detection 202 are possible at the time of overcharge or charge overcurrent detection by changing the value of the resistance R25.

That is, in a state in which overcharge or charge overcurrent is not detected in a normal state, a high level, which is the same as the control signal of the first field effect transistor M11, is input to the gate of the first changing means M21, And performs a normal operation that does not occur.

However, if overcharge or charge overcurrent is detected and a signal for turning off the first field effect transistor M11 is outputted, the gate voltage of the first changing means M21 is changed to the low level and the resistor R25 is activated to turn on the discharge overcurrent detection value And short-circuit detection value. Therefore, by raising the overall reference voltage using the resistor R25, the discharge overcurrent detection 203 and the short circuit detection 202 can be performed even when the parasitic diode D11 is turned on.

The forward voltage of the parasitic diode D11 must be accurately reflected in order to accurately compensate the rising value of the parasitic diode D11 by the first changing means M21 described above.

In order to accurately reflect the forward voltage of the parasitic diode D11, the first field effect transistor M11 must be turned off to turn on the parasitic diode D11, as in the overcharging or charging overcurrent state. Therefore, the VDD voltage 105 is set to the overcharge detection voltage To detect overcharging and to maintain it.

However, since the overcharge is detected at a relatively high value, there is a difference of about 1 V from the value of about 3.5 V, which is a VDD voltage for detecting a discharge overcurrent or a short circuit. This difference makes it possible to make a difference of the output value of the reference voltage generator. Therefore, in order to compensate the difference of the voltage, a method of changing the value of COUT using the test mode while maintaining a constant value of about 3.5 V is used .

Hereinafter, a battery protection circuit according to an embodiment of the present invention for accurately reflecting a forward voltage of a parasitic diode will be described with reference to the accompanying drawings.

First Embodiment

4 is a circuit diagram for explaining discharge overcurrent detection and short circuit detection according to the first embodiment of the present invention.

4, the discharge overcurrent and short circuit detecting circuit 300 according to the present invention includes an overcurrent detecting unit 301A for detecting a discharge overcurrent and a short circuit, a first diode voltage detecting unit 301A for accurately detecting a forward voltage of the parasitic diode D11, And a detection unit 310.

The overcurrent detecting unit 301A is composed of a first voltage dividing circuit 302A, a first comparing circuit 303A, and a second comparing circuit 304A.

The first voltage dividing circuit 302A is constituted by connecting resistors R31, R32, R33 and R34 in series, and divides the first reference voltage of the reference voltage circuit 320A. One end of the resistor R31 is connected to the reference voltage circuit 320A and the resistor R34 is constituted of a variable resistor capable of fusing the resistor and connected to the VSS terminal through the first diode voltage detector 310 Respectively.

In the first comparison circuit 303A, the first input terminal is connected to the first node A, and the second input terminal is connected to the V- terminal 330A. The first comparing circuit 303A detects a short circuit and supplies a detection signal to the logic circuit 118. [

The second comparison circuit 304A has the first input terminal connected to the second node B and the second input terminal connected to the V- terminal 330A. The second comparison circuit 304A detects the discharge overcurrent and supplies the detection signal to the logic circuit 118. [

The first diode voltage detecting unit 310 includes a second voltage dividing circuit 311, a first changing unit 312, a first controlling unit 313, a memory 314, and a third comparing circuit 315.

The second voltage dividing circuit 311 is constituted by connecting resistors R35, R36, R37 and R38 in series, and divides the second reference voltage of the reference voltage circuit 320A. One end of the resistor R35 is connected to the reference voltage circuit 320A via the overcurrent detecting unit 301A and the resistor R38 is connected to the VSS terminal.

The first changing means 312 is constituted by field effect transistors M31, M32, M33 and M34 and the field effect transistors M31, M32, M33 and M34 change the partial pressure ratio of the second voltage dividing circuit 311 . The gates of the field effect transistors M31, M32, M33, and M34 are connected to the resistors R35, R36, R37, and R38 connected in series, and the gates of the field effect transistors M31, M32, M33, And is connected to the control unit 313 and controls the field effect transistors M31, M32, M33, and M34 by the first control unit 313 signal to change the resistance value.

The first control unit 313 controls the field effect transistors M31, M32, M33 and M34 of the first changing means 312 to accurately compensate the rising value of the parasitic diode D11. The table values necessary for on / off control of the respective field effect transistors M31, M32, M33 and M34 are inputted through the memory 314 in order to compensate for the rising value of the parasitic diode D11.

In the normal state, that is, when overcharge or charge overcurrent is not detected, the first control unit 313 outputs the same high level as that of the first field effect transistor M11 to the field effect transistors M31, M32, M33, and M34), and performs a normal operation in which the resistance is not affected.

When a low level signal that overcharging or charging overcurrent is detected and the first field effect transistor M11 is turned off is output to the first control section 313, the third comparison circuit 315 is inputted through the V- terminal 330 The forward voltage of the parasitic diode D11 and the forward voltage of the third node C formed by on / off control of the field effect transistors M31, M32, M33, and M34 of the first changing means 312 by the first control unit 313 ) Are compared with each other.

The third comparison circuit 315 raises the table value stored in the memory 314 and when the value of the third node C reaches the same value as the forward voltage value of the parasitic diode D11, The output of the circuit 315 is changed. When the changed signal is input to the memory 314, the discharge overcurrent detection value and the short circuit detection value are raised by the voltages of the second voltage dividing circuit 311 and the first voltage dividing circuit 302A, Discharge overcurrent detection and short-circuit detection can be performed even in a state where the discharge current D11 is turned on.

According to the first embodiment described above, in order to accurately detect the forward voltage of the parasitic diode D11, the first diode voltage detector 310 is provided to detect the forward voltage of the parasitic diode D11 input through the V- And the value of the third node C formed by raising the value of the table stored in the memory 314 is compared with the value of the third node C through the comparator 315 to raise the voltage value of the discharge overcurrent and the short circuit, Discharge overcurrent detection and short-circuit detection can be performed.

Second Embodiment

5 is a circuit diagram for explaining discharge overcurrent detection and short circuit detection according to a second embodiment of the present invention.

5, the discharge overcurrent and short circuit detecting circuit 400 according to the present invention includes an overcurrent detecting unit 301B for detecting a discharge overcurrent and a short circuit, a second diode voltage detecting unit 301B for accurately detecting a forward voltage of the parasitic diode D11, And a detection unit 410.

The overcurrent detecting section 301B is composed of a first voltage dividing circuit 302B, a first comparing circuit 303B and a second comparing circuit 304B.

The first voltage dividing circuit 302B is constituted by connecting resistors R41, R42, R43 and R44 in series, and divides the first reference voltage of the reference voltage circuit 320B. One end of the resistor R41 is connected to the reference voltage circuit 320B and the resistor R44 is constituted by a variable resistor capable of fusing the resistor and is connected to the VSS terminal through the second diode voltage detector 410 Respectively.

In the first comparison circuit 303B, the first input terminal is connected to the fourth node D, and the second input terminal is connected to the V- terminal 330B. The first comparison circuit 303B detects a short circuit and supplies a detection signal to the logic circuit 118. [

The second comparison circuit 304B has the first input terminal connected to the fifth node E and the second input terminal connected to the V- terminal 330B. The second comparison circuit 304B detects the discharge overcurrent and supplies the detection signal to the logic circuit 118. [

The second diode voltage detector 410 includes a third voltage divider circuit 411, a second changing unit 412, a second controller 413 and an analog to digital converter 414.

The third voltage dividing circuit 411 is constituted by connecting resistors R45, R46, R47 and R48 in series, and divides the second reference voltage of the reference voltage circuit 320B. One end of the resistor R45 is connected to the reference voltage circuit 320B via the overcurrent detecting unit 301B and the resistor R48 is connected to the VSS terminal.

The field effect transistors M41, M42, M43, and M44 are configured to change the voltage division ratio of the second voltage dividing circuit 411. The second voltage dividing circuit 411 includes a field effect transistor M41, M42, M43, . The gates of the field effect transistors M41, M42, M43 and M44 are connected to the resistors R45, R46, R47 and R48 connected in series, respectively, and the gates of the field effect transistors M41, M42, The resistance value is changed by controlling the field effect transistors M41, M42, M43, and M44 by the second control unit 413 signal in connection with the control unit 413.

The analog-to-digital converter 414 receives the forward voltage of the parasitic diode D11 through the V- terminal 330B and changes the output digital code according to the value, and the second control unit 413 converts the forward digital voltage of the analog- 414 of the second changing means 412 and on / off control of the field effect transistors M41, M42, M43, M44 of the second changing means 412 to accurately compensate the rising value of the parasitic diode D11.

In the normal state, that is, when overcharge or overcharge is not detected, the second control unit 413 outputs the same high level as that of the first field effect transistor M11 to the field effect transistors M41, M42, M43, and M44), and performs a normal operation in which the resistance is not affected.

When an overcharge or charge overcurrent is detected and a low level signal for turning off the first field effect transistor M11 is output to the second control section 413, the analog-to-digital converter 414 outputs a parasitic The forward voltage of the diode D11 is input, and the output digital code of the analog-to-digital converter 414 changes according to the value. The second control unit 413 receives the changed digital code and controls on / off the field effect transistors M41, M42, M43, and M44 with the changed values to control the third voltage dividing circuit 411 and the first voltage dividing circuit 302B ), The discharge overcurrent detection value and the short circuit detection value are raised.

According to the second embodiment described above, the second diode voltage detector 410 is provided to accurately detect the forward voltage of the parasitic diode D11 and inputs the forward voltage of the parasitic diode D11 through the V- terminal 330B The output digital code of the analog-to-digital converter 414 is changed in accordance with the value to turn on / off the field effect transistors M41, M42, M43 and M44 by the second control unit 413, The discharge overcurrent detection and the short circuit detection can be performed at the time of overcharge or charge overcurrent detection.

The battery protection circuit according to the present invention is provided with a diode voltage detection unit in the overcurrent detection circuit and the short circuit detection circuit to enable discharge overcurrent detection and short circuit detection at the time of overcharge or charging overcurrent detection, The present invention provides a battery protection circuit capable of safely performing discharge overcurrent detection and short circuit detection at the time of overcharge or charging overcurrent detection by accurately detecting the forward voltage of the parasitic diode and raising the discharge overcurrent detection and short circuit detection voltage values.

It should be noted that the embodiments of the present invention disclosed in the present specification and drawings are only illustrative of specific examples for the purpose of understanding and are not intended to limit the scope of the present invention. It will be apparent to those skilled in the art that other modifications based on the technical idea of the present invention are possible in addition to the embodiments disclosed herein.

300: Discharge overcurrent detection and short circuit detection circuit
301A, 301B: overcurrent detecting units 302A, 302B: first voltage dividing circuit
303A, 303B: first comparison circuit 304A, 304B: second comparison circuit
320A, 320B: reference voltage circuit 330A, 330B: overcurrent detection terminal
310: first diode voltage detecting unit 311: second voltage dividing circuit
312: first changing means 313: first controlling means
314: memory 315: third comparing circuit
R31, R32, R33, R35, R36, R37, R38: Resistor R34:
M31, M32, M33, M34: Field effect transistor

Claims

A battery protection circuit for controlling charging and discharging of a battery,
A reference voltage circuit for generating a first reference voltage;
An overcurrent detecting unit for detecting an overcurrent state or a shortcircuit state of the battery;
A charge control switch and a discharge control switch for interrupting an overcurrent by an output signal of the overcurrent detection unit;
A parasitic diode that is turned on to allow a discharge current or a charge current to flow when the charge control switch or the discharge control switch is turned off to interrupt charging or discharging when the overcurrent is generated; And
And a diode voltage detector for detecting a forward voltage of the parasitic diode and dividing the first reference voltage to form a second reference voltage,
Wherein the overcurrent detection unit detects the state of the battery using either the first reference voltage or the second reference voltage and the voltage of the overcurrent detection terminal according to the overcurrent state.

The battery protection circuit according to claim 1, wherein the overcurrent detection unit detects the state of the battery using the first reference voltage and the voltage of the overcurrent detection terminal if the overcurrent state is not detected.

The battery protection circuit according to claim 1, wherein the overcurrent detection unit detects the state of the battery using the second reference voltage and the voltage of the overcurrent detection terminal when the overcurrent state is detected.

2. The overcurrent detecting apparatus according to claim 1,
A first voltage dividing circuit for dividing the first reference voltage;
A first comparison circuit for comparing the output signal of the first voltage division circuit with the voltage of the overcurrent detection terminal to detect a discharge overcurrent of the battery; And
And a second comparing circuit for comparing the output signal of the first voltage dividing circuit with the voltage of the overcurrent detecting terminal to detect a short circuit of the battery.

The apparatus of claim 1, wherein the diode voltage detector comprises:
A second voltage dividing circuit for dividing the second reference voltage;
First changing means for changing a voltage of the second voltage dividing circuit;
A first control unit for controlling the first changing means;
A third comparing circuit for comparing a voltage changed by the first changing means and a forward voltage of the parasitic diode inputted through the overcurrent detecting terminal; And
And a memory storing a table value for receiving the output signal of the third comparison circuit and the signal of the first control unit and detecting a forward voltage of the parasitic diode.

The apparatus of claim 1, wherein the diode voltage detector comprises:
A third voltage dividing circuit for dividing the second reference voltage;
Second changing means for changing the voltage of the third voltage dividing circuit;
A second control unit for controlling the second changing unit; And
And an analog-to-digital converter for receiving a forward voltage of the parasitic diode inputted through the overcurrent detection terminal and outputting a digital code.

The method according to claim 5 or 6,
Wherein the first changing means or the second changing means comprises a field effect transistor.

The method according to claim 5 or 6,
Wherein the first control unit and the second control unit receive a control signal of the charge control switch.