KR101089833B1 - Soft start circuit for protecting battery and Battery pack having the same - Google Patents

Abstract

The present invention discloses a soft start circuit for battery protection and a battery pack having the same. A battery protection soft start circuit according to the present invention includes a battery protection circuit for controlling a discharge current according to a discharge circuit connected to a secondary battery, the battery protection circuit comprising: a discharge switching element configured to limit the discharge current to a constant current; And a switching element driver electrically connected in parallel between the discharge switching element and the secondary battery to control an operation of the discharge switching element, wherein the switching element driver outputs a sensed voltage according to the detection of the discharge current as an amplified voltage. Compared to the voltage, when the amplification voltage exceeds the reference voltage, the operation control so that the resistance of the discharge switching element is variable, it characterized in that the negative feedback of the output limited discharge current by the discharge switching element.

According to the present invention, the resistance value of the charge / discharge switching element is variably controlled, and the negative feedback of the charge / discharge current limited by the charge / discharge switching element is reduced so that the secondary battery and the charge / discharge circuit are softly connected without damaging the configuration circuit. Start control is possible.

Secondary Battery, Soft-Start, Charge / Discharge, Constant Current, Negative Feedback

Description

Soft start circuit for protecting battery and battery pack having same {Soft start circuit for protecting battery and Battery pack having the same}

The following drawings, which are attached to this specification, illustrate exemplary embodiments of the present invention, and together with the detailed description of the present invention, serve to further understand the technical spirit of the present invention. It should not be construed as limited to.

1 is a circuit diagram showing a battery protection circuit according to the prior art.

2 is a circuit diagram showing another battery protection circuit according to the prior art.

3 is a circuit diagram showing a soft start circuit according to a preferred embodiment of the present invention.

4 is a circuit diagram showing a switching element driver according to a preferred embodiment of the present invention.

5 is a flowchart illustrating a process of controlling the discharge current according to the discharge circuit connection in accordance with a preferred embodiment of the present invention.

6 is a graph showing the discharge current according to the discharge circuit connection according to a preferred embodiment of the present invention.

FIG. 7 is a graph showing the output voltage of the first operational amplifier measured at point A of FIG.

8 is a graph showing the output voltage of the second operational amplifier measured at point B of FIG.

9 is a flowchart illustrating a process of controlling a charging current according to a charging circuit connection according to a preferred embodiment of the present invention.

<Description of Major Reference Marks in Drawings>

100 secondary battery 200 control unit

300 ... soft start circuit 310 ... DFET

320 ... CFET 330 ... Switching Device Driver

331 The first operational amplifier 331a ... sensing resistor

332 Second Operational Amplifier 333 Drive Transistor

340 ... Charge and discharge interlock switch

The present invention relates to a soft start circuit for battery protection and a battery pack having the same. More particularly, a soft start circuit for battery protection capable of controlling an initial transient current according to connection of a charge / discharge circuit of a secondary battery, and a battery pack having the same. It is about.

In general, a secondary battery is a battery that can be repeatedly used through a discharge that converts chemical energy into electrical energy and a charging process reverse to the conversion thereof, and types thereof include nickel-cadmium batteries, nickel-hydrogen batteries, and lithium-ions. Batteries and lithium-ion polymer batteries.

Recently, the growth of secondary batteries is due to the rapid growth of new markets including digital home appliances, portable terminals and the like. Such secondary batteries are classified into lithium based batteries and nickel-hydrogen based batteries.

Lithium-based small secondary batteries are applied to products such as digital cameras, P-DVDs, MP3Ps, mobile phones, PDAs, portable game devices, power tools, and e-bikes. Nickel-hydrogen medium and large secondary batteries are HUV (Hybrid Electric). Applied to electric vehicles such as vehicles.

A medium-large secondary battery used as a power of an electric vehicle is composed of a plurality of unit battery cells connected in series and parallel, and the secondary battery module of such a configuration supplies a high voltage to a motor used to drive a vehicle.

On the other hand, the secondary battery is exploded and ignited in an abnormal situation, that is, overcharge, overcurrent or overdischarge. In particular, when the lithium-based secondary battery operates over a range of voltages, the secondary battery is greatly deteriorated or damaged, and thus the secondary battery is protected using a battery protection circuit.

Japanese Laid-Open Patent Publication No. 1997-117072 discloses a voltage difference detecting means for detecting a voltage difference of a secondary battery, a judging means for judging whether the detected voltage difference has exceeded a predetermined value, and a current cutoff according to the judging of the judging means. A secondary battery protection circuit having a current blocking means is disclosed, and Japanese Patent Laid-Open No. 2003-143751 discloses a pair of field effect transistors (hereinafter referred to as FETs) for blocking charge current and discharge current. And a protection circuit including a protection IC for controlling the FET ON / OFF (ON / OFF) and to protect the battery is disclosed, the battery protection circuit according to the prior art with reference to Figure 1 as follows.

As shown in FIG. 1, the battery protection circuit 20 is provided in an encapsulation part of a battery pack so as to be electrically connected between the secondary battery 10 and the load circuit 30, and a positive (+) line of the battery pack. A first and second FETs 22 and 23 connected in series with the phase, and a control unit 21 for controlling the first and second FETs 22 and 23.

Here, the controller 21 detects the voltage of the secondary battery 10 and, when a voltage equal to or greater than the charging voltage is detected, controls the first FET 22 to be in an OFF state to cut off the charging current and discharge voltage. When the above voltage is detected, the second FET 23 is controlled to the OFF state to cut off the discharge current.

The battery protection circuit 20 may protect the secondary battery 10 from overcharging or overdischarging, but it is difficult to control initial overcurrent due to the connection of the load circuit 30.

That is, when the load circuit 30 including the large-capacity capacitor 31, the inverter 32, and the driving motor 33 is connected to the battery pack, the secondary battery 20 may instantaneously charge the large-capacity capacitor 31. The discharge of a large amount of current, which acts as a negative factor damaging not only the battery protection circuit 20 but also the secondary battery 10 and the load circuit 30.

As shown in FIG. 2, the current limiting resistor 24 and the charge / discharge switch 25 are electrically connected to both ends of the first and second FETs 22 and 23 to control the initial overcurrent according to the related art. Pre-charging of the large capacity capacitor 31 is possible by connecting to, but when charging the large capacity capacitor 31 with a low current, it takes a lot of charging time, in order to shorten the charging time, the large current limiting resistor 24 is There is a problem that is required.

The present invention has been made to solve the above problems, the battery protection software that can control the initial transient current according to the connection of the secondary battery and the charge and discharge circuit with a constant current by variable control of the resistance of the charge and discharge FET It is an object of the present invention to provide a start circuit and a battery pack having the same.

In the battery protection soft start circuit according to the present invention for achieving the above object, the battery protection circuit for controlling the discharge current according to the discharge circuit is built in the secondary battery, the discharge to limit the discharge current to a constant current discharge Switching elements; And a switching element driver electrically connected in parallel between the discharge switching element and the secondary battery to control the operation of the discharge switching element, wherein the switching element driver converts the sensed voltage according to the detection of the discharge current into an amplification voltage. The output voltage is compared with a reference voltage, and when the amplification voltage exceeds the reference voltage, operation control of the resistance of the discharge switching element is variable, and negative feedback of the output limited discharge current is performed by the discharge switching element.

In the present invention, the switching element driver comprises: a first operational amplifier (OP AMP 1) for amplifying the voltage of both ends of the sensing resistor provided on the path of the discharge current to output as an amplified voltage; A second operational amplifier (OP AMP 2) for comparing the amplified voltage with a preset reference voltage and reducing the amplified voltage and outputting the reduced voltage when the amplified voltage exceeds the reference voltage; And a driving transistor (DTR) which is turned on by the reduction voltage and outputs an operation control voltage to the discharge switching element, and variably controls the resistance value of the discharge switching element.

Preferably, the discharge switching element is a MOS field effect transistor (MOSFET), the driving of the gate (G) of the MOS field effect transistor is made by the operation control voltage of the switching element driver, the MOS field effect transistor by the gate drive. The resistance value between the source S and the drain D is variably controlled.

More preferably, the MOS field effect transistor is provided with a parasitic diode therein, and the parasitic diode is connected between the source and the drain so as to be reverse to the discharge current.

According to the present invention, the discharge current is controlled to the constant current by the variable control of the resistance value.

According to the present invention, one end of the switching element driver is electrically connected to the current input terminal of the discharge switching element provided in the positive (+) line of the secondary battery, and the other end thereof is electrically connected to the negative (-) line of the secondary battery. Connected.

Preferably, the discharge circuit includes a large capacity capacitor.

According to another aspect of the invention, the battery protection circuit for controlling the charging current according to the connection of the charging circuit is built in the secondary battery, the charge switching device for output limiting the charging current to a constant current; And a switching element driver electrically connected in parallel between the charging switching element and the charging circuit to control an operation of the charging switching element, wherein the switching element driver converts the sensed voltage according to the sensing of the charging current into an amplification voltage. Outputs and compares it with a reference voltage, and when the amplification voltage exceeds the reference voltage, operates to control the resistance of the charging switching element to be variable, and negatively feedbacks the output limited charging current by the charging switching element. Provide a protective soft-start circuit.

According to the present invention, one end of the switching element driving unit is electrically connected to the current input terminal of the charging switching element provided in the positive electrode line of the secondary battery, and the other end thereof is electrically connected to the negative electrode line of the secondary battery.

According to the present invention, the reduction voltage is equal to or less than the reference voltage and is inversely proportional to the strength of the amplification voltage.

According to still another aspect of the present invention, a battery protection circuit for controlling a charge and discharge current according to a charge and discharge circuit connection built in a secondary battery, the charge and discharge switching element for limiting the output of the charge and discharge current to a constant current ; A switching element driver for controlling the operation of the charge / discharge switching element; And a charge / discharge interlock switch for selectively connecting one end of the switching element driver to a current input terminal of a charge or discharge switching element according to charging or discharging. The voltage is output as an amplification voltage and compared with a reference voltage. When the amplification voltage exceeds the reference voltage, operation control is performed so that the resistance of the charge / discharge switching element is varied, and the charge / discharge switching element limited by the charge / discharge switching element is controlled. Provided are a soft start circuit for battery protection, characterized by negative feedback of a discharge current.

Preferably, the charge / discharge switching element is connected in series to the positive line of the secondary battery.

According to the present invention, the charge / discharge interlock switch electrically connects one end of the switching element driver to a current input terminal of a charge switching element when the charging circuit is connected, and one end of the switching element driver when the discharge circuit is connected. Is electrically connected to the current input of the discharge switching element.

In the present invention, the other end of the switching element driver is electrically connected to the negative electrode line of the secondary battery.

According to still another aspect of the present invention, a battery pack provided in a secondary battery and having a battery protection circuit for controlling charging and discharging current due to connection of a charging and discharging circuit, the output limiting of the charging and discharging current to a constant current Charge / discharge switching elements; A switching element driver for controlling the operation of the charge / discharge switching element; A charge / discharge interlock switch for selectively connecting one end of the switching element driver to an input side of a charge or discharge switching element according to charge or discharge; And a controller for controlling on / off of the charge / discharge switching element and the charge / discharge interlock switch, wherein the switching element is configured to output a sensed voltage according to the detection of the charge / discharge current as an amplified voltage. In comparison with the above, when the amplification voltage exceeds the reference voltage, the control of the charge / discharge switching element is controlled to vary, and the negative feedback of the charge / discharge current limited by the charge / discharge switching element is output. A battery pack having a soft start circuit for protecting a battery is provided.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, which can be replaced at the time of the present application It should be understood that there may be various equivalents and variations.

The soft start circuit for protecting a battery according to the present invention has a structural feature of variably controlling the resistance value of a charge / discharge switching element through a switching element driver, and the charge / discharge switching element is a MOSFET. In the embodiment of the present invention, the charge switching device is defined as 'CFET' and the discharge switching device is defined as 'DFET'.

The soft start circuit according to the present invention will be described with reference to FIG. 3.

As shown in FIG. 3, the soft start circuit 300 provided in the encapsulation portion of the battery pack including the secondary battery 100 and the controller 200 is a DFET connected in series with the positive line (Pack +) of the battery pack. Switching device having one end electrically connected to the 310 and the CFET 320, the current input terminal of the DFET 310 or the CFET 320, and the other end of the battery pack to the cathode line Pack − of the battery pack. And a charge / discharge interlock switch 340 for selectively connecting one end of the switching element driver 330 to the current input terminal of the DFET 310 or the CFET 320.

The secondary battery 100 is a unit battery cell assembly in which a plurality of unit battery cells are connected in series or in parallel, and the controller 200 detects a voltage of the secondary battery 100 and charges and discharges the secondary battery 100. The DFET 310, the CFET 320, the switching element driver 330, and the charge / discharge interlock switch 340 are controlled accordingly.

When the battery pack is connected to the charging circuit, the controller 200 controls the charge / discharge interlock switch 340 so that one end of the switching element driver 330 is electrically connected to the charging current input terminal of the CFET 320. When the battery pack is connected to the discharge circuit, the charge / discharge interlock switch 340 is controlled so that one end of the switching element driver 330 is electrically connected to the discharge current input terminal of the DFET 310. .

The DFET 310 and the CFET 320 output an overcurrent instantaneously flowing between the battery pack and the charge / discharge circuit with a constant current, and the switching device driver 330 detects the overcurrent flowing in the battery pack to detect the DFET 310 and Operation control so that the resistance of the CFET 320 is variable.

In an embodiment of the present invention, when a charging circuit is electrically connected to the battery pack, an initial overcharge current flows in the battery pack, and the CFET 320 is driven by the switching element driver 330 according to the generation of the initial overcharge current. The resistance value is controlled to a half ON state in which the resistance is variable, and the initial overcharge current is limited under the control of the CFET 320.

On the other hand, when the discharge circuit is electrically connected to the battery pack, the initial over-discharge current flows in the battery pack, the resistance value of the DFET 310 is variable by the switching element driver 330 according to the generation of the initial over-discharge current It is controlled to a half ON state, the initial over-discharge current is limited by the control of the DFET 320.

After the initial overcurrent is limited and the current is stabilized, the controller 200 detects the charge / discharge current in the normal state on the positive and negative lines (Pack +, Pack −) of the battery pack. And the CFET 320 in an ON state to conduct charge and discharge currents.

As described above, the soft start circuit 300 limits the initial overcurrent according to the electrical connection between the battery pack and the charge / discharge circuit to a constant current, thereby enabling soft start, and the secondary battery and the charge / discharge circuit. The switching element driver 330 provided in the soft start circuit 300 senses an initial overcharge or an initial overdischarge current and outputs an operation control voltage to the DFET 310 or the CFET 320, and controls the operation. The DFET 310 or the CFET 320 whose resistance is changed by a voltage limits the initial overcharge or initial overdischarge current to a constant current and outputs the same.

The configuration of the switching element driver for outputting the operation control voltage to the above-described DFET or CFET will be described with reference to FIG. 4. 4 is a circuit diagram showing a switching device driver according to a preferred embodiment of the present invention, wherein the switching device driver controls the operation of the DFET according to the electrical connection of the discharge circuit.

As shown in FIG. 4, the switching element driver 330 is electrically connected in parallel with the DFET 310 and the CFET 320 connected in series to the positive line (Pack +) of the battery pack, that is, the positive line of the secondary battery. .

In the exemplary embodiment of the present invention, one end of the switching element driver 330 is electrically connected to the discharge current input terminal of the DFET 310 so as to limit the discharge current, and the other end thereof is a cathode line (Pack −) of the battery pack. When the charging circuit is connected to the battery pack, but is electrically connected to the negative electrode line of the secondary battery, one end of the switching element driver 330 is charged by the charge / discharge interlock switch controlled by the controller to charge the CFET 320. Obviously, it is electrically connected to the current input.

The switching device driver 330 may include a first operational amplifier (OP AMP 1) 331 that amplifies a sensed voltage according to the detection of a discharge current and outputs the amplified voltage, and an amplified voltage of the first operational amplifier 331. A second operational amplifier (OP AMP 2) 332 for comparing the reference voltage and outputting a conditional voltage, and a driving transistor for outputting an operation control voltage to the DFET 310 by the conditional voltage of the second operational amplifier 332. (DTR) 333.

The first operational amplifier 331 amplifies the voltage across the sensing resistor 331a connected in series on the negative line of the battery pack and outputs the amplified voltage. Here, the sensing resistor 331a is connected in parallel to the input terminal of the first operational amplifier 331.

The second operational amplifier 332 receives an amplified voltage output from the first operational amplifier 331 and a reference voltage output from the controller, and compares the amplified voltage and the reference voltage so that the amplified voltage is a reference voltage. If exceeded, the amplification voltage is decreased by the amount corresponding to the difference between the amplification voltage and the reference voltage. Hereinafter, for convenience of description, the reduced amplification voltage is referred to as a 'reduction voltage'.

When the voltage level output from the second operational amplifier 332 drops below the reference voltage, the driving transistor 333 is turned on to operate so that the amplified current flows from the emitter E toward the collector C. As a result, the gate G voltage of the DFET 310 is increased. The voltage rise causing the half-on of the DFET 310 may be defined as a gate driving voltage.

Half-on driving of the DFET 310 is performed by an increase in the gate voltage due to an operating current of the driving transistor 333, and is increased between the source S and the drain D of the DFET 310 by the increase in the gate voltage. The resistance is variably controlled, and the discharge current limited by the DFET 310 is negative feedbacked to the switching element driver 330.

That is, as the gate driving voltage of the DFET 310 increases, the resistance between the source and the drain increases, so that the discharge current flowing through the cathode line of the battery pack is reduced, and the reduced discharge current is the switching element driver 330. Negative feedback is repeatedly performed by the switching element driver 330.

Meanwhile, as the gate driving voltage of the DFET 310 decreases, the resistance between the source and the drain decreases, so that the amount of current flowing through the cathode line of the battery pack increases.

In the embodiment of the present invention, the driving transistor 333 is a PNP type transistor, the DFET 310 is a power MOSFET having a parasitic diode electrically connecting the source and the drain in the reverse direction to the discharge current, the drive Collector C and emitter E of transistor 333 are electrically connected to the gate and the drain of DFET 310, respectively.

The operation of the soft start circuit including the switching element driver having the above-described configuration will be described below with reference to FIGS. 3, 4, 6, 7, and 8 with reference to FIG. 5. Here, the soft start circuit limits the charging or discharging current to the constant current according to the connection of the charging or discharging circuit. An embodiment of the present invention describes a process of limiting the discharging current to the constant current.

Referring to the drawings, when the discharge circuit is connected to the battery pack including the secondary battery 100, the control unit 200 and the soft start circuit 300, the charge and discharge interworking at the same time as the connection time (t ₀ ) of the discharge circuit The switch 340 is discharge switched under the control of the controller 200 (S110 and S120).

In this case, the charge / discharge interlock switch 340 allows one end of the switching element driver 330 to be electrically connected to the discharge current input terminal of the DFET 310.

Next, when the discharge current flows inside the battery pack by the connection of the discharge circuit, the discharge current is sensed by the sensing resistor 331a provided on the negative line of the battery pack, and the sensing resistor 331a Both voltages are output as an amplified voltage by the first operational amplifier 331 (S130 and S140).

In this case, as shown in FIG. 6, the discharge current I _D is instantaneously flowed above the overdischarge current, that is, the normal start current I _SST at the beginning of discharge, and the amplification voltage in the W section at the beginning of the discharge. As shown in FIG. 7, V ₁ increases in proportion to the intensity of the discharge current I _D.

After the step S140, the amplified voltage output from the first operational amplifier 331 and the reference voltage output from the controller 200 are compared by the second operational amplifier 332, and the amplified voltage V ₁ is compared with the reference. Voltage (V _SST ) is V ₁ > V _SST The second operational amplifier 332 outputs a reduced voltage by decreasing the amplification voltage V ₁ in inverse proportion to the reference voltage or less as shown in FIG. 8 (S150 and S160).

After the operation S160, the driving transistor 333 is turned on, that is, energized by the reduced voltage output from the second operational amplifier 332, and the driving transistor 333 drives a gate to the gate of the DFET 310. A voltage is applied (S170).

After the step S170, the resistance between the source and the drain of the DFET 310 is increased by the gate driving voltage so that the DFET 310 is half-on and the discharge current is limited by the half-on operation (S180). And S190).

After the step S190, the discharge current limited by the DFET 310 is negatively fed back to the switching element driver 300 to be controlled to a constant current through the steps S130 to S190.

In an embodiment of the present invention, in the step S150, the amplification voltage (V ₁ ) and the reference voltage (V _SST ) is V ₁ ≤ V _SST In this case, the output of the second operational amplifier 332 becomes a source voltage of the DFET 310, and the controller 200 controls the DFET 310 to be turned on (S180 ′).

Meanwhile, a process of limiting the charging current to the constant current will be described with reference to FIGS. 3, 4, 6, 7, and 8 with reference to FIG. 9.

Referring to the drawings, when the charging circuit is connected to the battery pack, at the same time as the connection time (t ₀ ) of the charging circuit, the charge and discharge interlock switch 340 is charged and switched under the control of the control unit 200 (S210 and S220). ).

In this case, the charge / discharge interlock switch 340 allows one end of the switching element driver 330 to be electrically connected to the charge current input terminal of the CFET 320.

Next, when the charging current flows through the connection of the charging circuit, the charging current is sensed by the sensing resistor 331a provided on the negative electrode line of the battery pack, and the voltage across the sensing resistor 331a is zero. 1 is output as an amplified voltage by the operational amplifier 331 (S230 and S240).

After the step S240, the amplified voltage output from the first operational amplifier 331 and the reference voltage output from the controller 200 are compared by the second operational amplifier 332, and the amplified voltage V ₁ ′. When the reference voltage V _SST ′ is V ₁ ′> V _SST ′, the second operational amplifier 332 reduces the amplification voltage V ₁ ′ in inverse proportion to a reference voltage or less and outputs a reduced voltage (S250 and S260).

After the operation S260, the driving transistor 333 is turned on, that is, energized by the reduced voltage output from the second operational amplifier 332, and the driving transistor 333 drives a gate to the gate of the CFET 320. A voltage is applied (S270).

After the step S270, the resistance between the source and the drain of the CFET 320 is increased by the gate driving voltage so that the CFET 320 is half-on and the charging current is limited by the half-on operation (S280). And S290).

After the step S290, the charging current limited by the CFET 320 is negatively fed back to the switching element driver 300 to be controlled to a constant current through the steps S230 to S290.

In an exemplary embodiment of the present invention, when the amplification voltage V1 'and the reference voltage VSST' are V1'≤VSST ', the output of the second operational amplifier 332 is the output of the CFET 320. Becomes the source voltage, and the controller 200 controls the CFET 320 to be turned on (S280 ′).

As described above, the soft start circuit provided in the encapsulation part of the battery pack may implement soft start by limiting the initial overcurrent between the battery pack and the charge / discharge circuit to a constant current when the charge and discharge circuit is connected.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

As described above, the present invention is constructed by connecting the secondary battery and the charge / discharge circuit by negatively controlling the resistance value of the charge / discharge switching element and negative feedback of the charge / discharge current limited by the charge / discharge switching element. The advantage is that soft-start control is possible without damaging the circuit.

In addition, since it is possible to design and manufacture a soft start circuit at a low cost without installing a separate soft start circuit as compared with the related art, it is possible to miniaturize a battery pack and reduce manufacturing costs.

In addition, damage to the secondary battery and the load circuit can be efficiently suppressed by limiting the initial charge / discharge current due to the connection between the secondary battery and the charge / discharge circuit to a constant current.

Claims (26)

In the battery protection circuit for controlling the discharge current in accordance with the discharge circuit connected to the secondary battery, A discharge switching element for output limiting the discharge current to a constant current; And And a switching element driver electrically connected in parallel between the discharge switching element and the secondary battery to control an operation of the discharge switching element. The switching element driver outputs a sensed voltage according to the detection of the discharge current as an amplification voltage and compares it with a reference voltage. When the amplification voltage exceeds the reference voltage, operation control is performed such that the resistance of the discharge switching element is changed. A soft start circuit for battery protection, characterized by negative feedback of output limited discharge current by a switching element. The method of claim 1, wherein the switching element driver, A first operational amplifier (OP AMP 1) for amplifying a voltage across the sensing resistor provided on the path of the discharge current and outputting the amplified voltage; A second operational amplifier (OP AMP 2) for comparing the amplified voltage with a preset reference voltage and reducing the amplified voltage and outputting the reduced voltage when the amplified voltage exceeds the reference voltage; And And a driving transistor (DTR) which is turned on by the reduction voltage and outputs an operation control voltage to the discharge switching element to variably control the resistance value of the discharge switching element. . The method according to claim 1 or 2, And the discharge switching element is a MOS field effect transistor (MOSFET). The method of claim 3, The driving of the gate G of the MOS field effect transistor is performed by an operation control voltage of the switching element driver, and the resistance between the source S and the drain D of the MOS field effect transistor is variably controlled by the gate driving. A soft start circuit for battery protection. 5. The method of claim 4, And a parasitic diode therein, wherein the parasitic diode is connected between the source and the drain so as to be reverse to the discharge current. 5. The method of claim 4, And a discharge current is controlled to be a constant current by the variable control of the resistance value. The method of claim 1, One end of the switching element driving unit is electrically connected to the current input terminal of the discharge switching element provided in the positive (+) line of the secondary battery, the other end is electrically connected to the negative (-) line of the secondary battery Soft start circuit for battery protection. The method of claim 1, wherein the discharge circuit, A soft start circuit for battery protection, comprising a large capacity capacitor. In the battery protection circuit built in the secondary battery for controlling the charging current according to the charging circuit connection, A charge switching device configured to limit the charge current to a constant current; And And a switching element driver electrically connected in parallel between the charging switching element and the charging circuit to control an operation of the charging switching element. The switching element driver outputs a sensing voltage according to the detection of the charging current as an amplification voltage and compares it with a reference voltage. A soft start circuit for battery protection, characterized by negative feedback of output limited charging current by a switching element. The method of claim 9, wherein the switching element driver, A first operational amplifier (OP AMP 1) for amplifying a voltage across the sensing resistor provided on the path of the charging current and outputting the amplified voltage; A second operational amplifier (OP AMP 2) for comparing the amplified voltage with a preset reference voltage and reducing the amplified voltage and outputting the reduced voltage when the amplified voltage exceeds the reference voltage; And And a driving transistor (DTR) which is turned on by the reduction voltage and outputs an operation control voltage to the charging switching element to variably control the resistance value of the charging switching element. . 11. The method according to claim 9 or 10, And the charge switching element is a MOS field effect transistor (MOSFET). The method of claim 11, The gate driving of the MOS field effect transistor is performed by an operation control voltage of the switching element driver, and the gate-drive soft start for the battery protection, characterized in that the resistance between the source and drain of the MOS field effect transistor is variably controlled. Circuit. The method of claim 12, And a parasitic diode therein, wherein the parasitic diode is connected between the source and the drain so as to be reverse to the charging current. The method of claim 13, And a charging current is controlled to be a constant current by the variable control of the resistance value. 10. The method of claim 9, One end of the switching element driving unit is electrically connected to the current input terminal of the charge switching element provided in the positive line of the secondary battery, the other end thereof is electrically connected to the negative line of the secondary battery is a soft start circuit . The method of claim 2 or 10, And said reduction voltage is equal to or less than a reference voltage and inversely proportional to the strength of said amplification voltage. In a battery protection circuit built in a secondary battery for controlling the charge and discharge current according to the connection of the charge and discharge circuit, A charge / discharge switching element which limits the charge / discharge current to a constant current; A switching element driver for controlling the operation of the charge / discharge switching element; And A charge / discharge interlock switch for selectively connecting one end of the switching element driver to a current input terminal of a charge or discharge switching element according to a charge or discharge; The switching element driver outputs a sensed voltage according to the detection of the charge / discharge current as an amplification voltage and compares it with a reference voltage. And negative feedback of the charge / discharge current limited in output by the charge / discharge switching element. The method of claim 17, The charge / discharge switching element is a soft start circuit for battery protection, characterized in that connected to the positive line of the secondary battery in series. The method of claim 17, The charge / discharge interlock switch electrically connects one end of the switching element driver to a current input terminal of a charge switching element when the charging circuit is connected, and connects one end of the switching element driver to the current input terminal of the charge switching element. A soft start circuit for battery protection, which is electrically connected to a current input terminal. The method of claim 19, And the other end of the switching element driver is electrically connected to the negative line of the secondary battery. The method of claim 17, wherein the switching element driver, A first operational amplifier (OP AMP 1) for amplifying a voltage across the sensing resistor provided on the path of the charge / discharge current and outputting the amplified voltage; A second operational amplifier (OP AMP 2) for comparing the amplified voltage with a preset reference voltage and reducing the amplified voltage and outputting the reduced voltage when the amplified voltage exceeds the reference voltage; And A driving transistor (DTR) which is turned on by the reduction voltage and outputs an operation control voltage to the charging or discharging switching element to variably control the resistance of the charging or discharging switching element. Protective soft start circuit. The method of claim 17, And said charge / discharge switching element is a MOS field effect transistor. The method of claim 22, And gate driving of the MOS field effect transistor is performed by an operation control voltage of a switching element driver, and the resistance between the source and drain of the MOS field effect transistor is variably controlled by the gate driving. The method of claim 22, And a parasitic diode therein, wherein the parasitic diode is connected between the source and the drain so as to be reverse to the charging or discharging current. 24. The method of claim 23, A soft start circuit for battery protection, characterized in that charge and discharge current is controlled by constant current by variable control of the resistance value. A battery pack, which is built in a secondary battery and has a battery protection circuit for controlling the charge and discharge current according to the connection of the charge and discharge circuit, A charge / discharge switching element which limits the charge / discharge current to a constant current; A switching element driver for controlling the operation of the charge / discharge switching element; A charge / discharge interlock switch for selectively connecting one end of the switching element driver to an input side of a charge or discharge switching element according to charge or discharge; And And a controller configured to control on / off of the charge / discharge switching element and the charge / discharge interlock switch. The switching element driver outputs a sensed voltage according to the detection of the charge / discharge current as an amplification voltage and compares it with a reference voltage. And a negative feedback of the charge / discharge current limited in output by the charge / discharge switching element.

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