阅读说明：本技术 改善锂电池保护电流电路 (Circuit for improving lithium battery protection current ) 是由 王友伟 邢国华 于 2020-04-29 设计创作，主要内容包括：本发明公开了一种改善锂电池保护电流电路,其包括印刷电路板、控制单元和侦测支路,控制单元和侦测支路分别设于印刷电路板,侦测支路包括依次串接的第一导电件、第一开关电路、第二开关电路和第二导电件,第一导电件和第二导电件分别印刷于印刷电路板,且第一导电件的自由端接控制单元的第一采集端,第一开关电路的触发端接控制单元的第一控制端,第二导电件的自由端接控制单元的第二采集端,第二开关电路的触发端接控制单元的第二控制端,控制单元监测侦测支路的电压或电流,并控制第一开关电路和第二开关电路的通断；本发明的结构简单、适用性强,无需增加元器件数量及占用产品空间,即可将保护阻抗设置为一合理值,以有效发挥保护电流的作用。(The invention discloses a circuit for improving the protection current of a lithium battery, which comprises a printed circuit board, a control unit and a detection branch circuit, wherein the control unit and the detection branch circuit are respectively arranged on the printed circuit board; the invention has simple structure and strong applicability, and can set the protection impedance to a reasonable value without increasing the number of components and occupying the product space so as to effectively play the role of protecting the current.)

1. The utility model provides an improve lithium cell protection current circuit which characterized in that: the control unit and the detection branch circuit are respectively arranged on the printed circuit board, the detection branch circuit comprises a first conductive piece, a first switch circuit, a second switch circuit and a second conductive piece which are sequentially connected in series, the first conductive piece and the second conductive piece are respectively printed on the printed circuit board, the free end of the first conductive piece is connected with the first acquisition end of the control unit, the trigger end of the first switch circuit is connected with the first control end of the control unit, the free end of the second conductive piece is connected with the second acquisition end of the control unit, the trigger end of the second switch circuit is connected with the second control end of the control unit, and the control unit monitors the voltage or current of the detection branch circuit and controls the on-off of the first switch circuit and the second switch circuit.

2. The improved lithium battery protection current circuit as claimed in claim 1, wherein: the detection branch circuit is provided with a detection resistor R, the first conductive piece is provided with a first resistor R1, the second conductive piece is provided with a second resistor R2, the first switch circuit is provided with a third resistor R3, the second switch circuit is provided with a fourth resistor R4, and the resistance value of the detection resistor R is the sum of the resistance values of the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4.

3. The improved lithium battery protection current circuit as claimed in claim 2, wherein the first resistance R1 (first conductive element length L1 × resistivity e)/(first conductive element width W1 × first conductive element thickness T1), and the second resistance R2 (second conductive element length L2 × resistivity e)/(second conductive element width W2 × second conductive element thickness T2), wherein the resistivity e is constant.

4. An improved lithium battery protection current circuit as claimed in claim 2, wherein: the control unit detects the current I flowing through the detection branch circuit and compares the current I with a preset protection current I_AAnd controlling the on-off of the first switch circuit and the second switch circuit according to the comparison result.

5. An improved lithium battery protection current circuit as claimed in claim 4, wherein: if the current I is less than the protection current I_A，The control unit controls the first switch circuit and the second switch circuit to be kept on;

if the present current I is greater than or equal to the protection current I_A，The control unit controls the first and second switching circuits to be turned off.

6. An improved lithium battery protection current circuit as claimed in claim 4, wherein: the control unit is preset with an overcurrent protection threshold voltage V_AProtection current I_AThreshold voltage of overcurrent protection V_AA/detection resistance R.

7. An improved lithium battery protection current circuit as claimed in claim 1, wherein: the printed circuit board is further printed with a plurality of wires, the free end of the first conductive piece is electrically connected with the first acquisition end of the control unit through the corresponding wire, and the free end of the second conductive piece is electrically connected with the second acquisition end of the control unit through the corresponding wire.

8. An improved lithium battery protection current circuit as claimed in claim 1, wherein: the first switch circuit and the second switch circuit are both field effect transistors.

9. An improved lithium battery protection current circuit as defined in claim 8, wherein: the first switching circuit and the second switching circuit are both AON7422 in type.

10. An improved lithium battery protection current circuit as claimed in claim 1, wherein: the first conductive piece and the second conductive piece are both copper foil pieces.

Technical Field

The invention relates to the field of lithium battery current protection, in particular to a circuit for improving the protection current of a lithium battery.

Background

With the progress of science and technology, lithium batteries are widely used in different types of electronics, electrical appliances and equipment, and in order to effectively protect the lithium batteries, protection circuits are generally required to be equipped for the lithium batteries so as to protect the lithium batteries from damage caused by overcharge, overdischarge, overcurrent, short circuit and ultrahigh-temperature charge and discharge.

Fig. 1 shows a protection circuit of a conventional lithium battery in the prior art, wherein overcurrent protection is implemented by detecting voltages of a charging MOSFET Q1 and a discharging MOSFET Q2, wherein a specific calculation formula of a protection current I is as follows: protection current I is overcurrent voltage protection threshold V/(R)_{Charging MOSFET Q1}+R_{Discharge MOSFET Q2}) From the above formula, it can be seen that, under the condition that the over-current voltage protection threshold V is fixed, the current value of the protection current I is completely represented by R_{Charging MOSFET Q1}+R_{Discharge MOSFET Q2}To decide. Because the existing protection circuit needs to protect lithium batteries with different capacities and parameters, and the types of the charging MOSFET Q1 and the discharging MOSFET Q2 are relatively few, the charging MOSFET Q1 and the discharging MOSFET Q2 cannot be found properly, so that R is caused_{Charging MOSFET Q1}And R_{Discharge MOSFET Q2}The impedance required by the theoretical protection current I cannot be accurately corresponded, the design of the protection current value I is easy to be unreasonable, and the lithium battery cannot be protected.

FIG. 2 is a protection circuit of still another conventional lithium battery in the prior art, which is different from FIG. 1 in that R is compensated for_{Charging MOSFET Q1}And R_{Discharge MOSFET Q2}The problem that the impedance required by theoretical protection current I cannot be accurately corresponded is solved, a power resistor r is additionally arranged on a protection circuit, so that the impedance is not sufficient by adjusting the resistance value of the power resistor r, and the specific calculation formula of the protection current I at the moment is as follows: protection current I is overcurrent voltage protection threshold V/(R)_{Charging MOSFET Q1}+R_{Discharge MOSFET Q2}+r_{Power resistor}) Although the scheme can well adjust the protection current I to realize effective protection of the lithium battery, the solution can not be applied to a printed circuit board with a small space and has a small application range because the power resistor r needs to be additionally arranged, which causes increase of product space and cost.

Therefore, there is a need for an improved lithium battery protection current circuit to solve the above problems.

Disclosure of Invention

The invention aims to provide a circuit for improving the protection current of a lithium battery, which has a simple structure and strong applicability, can effectively set the protection impedance required by the protection circuit to a reasonable value without increasing the number of electronic components and occupying the product space so as to effectively play a role of protecting the current, and is particularly suitable for being applied to a printed circuit board with a small space.

In order to achieve the purpose, the invention discloses a circuit for improving the protection current of a lithium battery, which comprises a printed circuit board, a control unit and a detection branch circuit, wherein the control unit and the detection branch circuit are respectively arranged on the printed circuit board, the detection branch circuit comprises a first conductive piece, a first switch circuit, a second switch circuit and a second conductive piece which are sequentially connected in series, the first conductive piece and the second conductive piece are respectively printed on the printed circuit board, the free end of the first conductive piece is connected with a first acquisition end of the control unit, the trigger end of the first switch circuit is connected with a first control end of the control unit, the free end of the second conductive piece is connected with a second acquisition end of the control unit, the trigger end of the second switch circuit is connected with a second control end of the control unit, and the control unit monitors the voltage or the current of the detection branch circuit, and controlling the on-off of the first switch circuit and the second switch circuit.

Compared with the prior art, the detection branch circuit comprises a first conductive piece, a first switch circuit, a second switch circuit and a second conductive piece which are sequentially connected in series, wherein the first conductive piece and the second conductive piece are respectively printed on a printed circuit board; on the other hand, the first conductive piece and the second conductive piece are respectively printed on the printed circuit board, so that space resources on the printed circuit board do not need to be occupied, other electronic components do not need to be introduced, product space is avoided to be occupied, product cost is not increased, the protection circuit is suitable for being directly transformed into an existing protection circuit, the required protection impedance of the protection circuit can be set to be a reasonable value, and the applicability is high.

Preferably, the detection branch has a detection resistor R, the first conductive member has a first resistor R1, the second conductive member has a second resistor R2, the first switch circuit has a third resistor R3, the second switch circuit has a fourth resistor R4, and a resistance value of the detection resistor R is a sum of resistance values of the first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4.

Specifically, the first resistance R1 ═ is (first conductor length L1 × resistivity e)/(first conductor width W1 × first conductor thickness T1), and the second resistance R2 ═ is (second conductor length L2 × resistivity e)/(second conductor width W2 × second conductor thickness T2), where the resistivity e is constant.

Specifically, the control unit detects a current I flowing through the detection branch and compares the current I with a preset protection current I_AAnd controlling the on-off of the first switch circuit and the second switch circuit according to the comparison result.

More specifically, if the present current I is smaller than the protection current I_A，The control unit controls the first switch circuit and the second switch circuit to be kept on;

if the present current I is greater than or equal to the protection current I_A，The control unit controls the first and second switching circuits to be turned off.

Specifically, the control unit is preset with an overcurrent protection threshold voltage V_AProtection current I_AThreshold voltage of overcurrent protection V_AA/detection resistance R.

Preferably, the printed circuit board is further printed with a plurality of wires, the free end of the first conductive piece is electrically connected to the first collecting end of the control unit through the corresponding wire, and the free end of the second conductive piece is electrically connected to the second collecting end of the control unit through the corresponding wire.

Preferably, the first switch circuit and the second switch circuit are both field effect transistors.

Specifically, the first switch circuit and the second switch circuit are both AON7422 in model.

Preferably, the first conductive member and the second conductive member are both copper foil members.

Drawings

Fig. 1 is a protection circuit of a conventional lithium battery in the prior art.

Fig. 2 is a protection circuit of yet another conventional lithium battery in the prior art.

Fig. 3 is a schematic structural diagram of an improved lithium battery protection current circuit according to the present invention.

Detailed Description

In order to explain technical contents, structural features, and objects and effects of the present invention in detail, the following detailed description is given with reference to the accompanying drawings in conjunction with the embodiments.

Referring to fig. 1-3, the improved lithium battery protection current circuit 100 of the present embodiment can adjust the impedance of the protection circuit based on the protection circuit of the existing conventional lithium battery, such as fig. 1 and 2, to set the protection impedance required by the protection circuit to a reasonable value, thereby effectively playing a role of protecting the current. This improve lithium battery protection current circuit 100 includes printed circuit board 10, the control unit 20 and detects branch circuit 30, detects branch circuit 30 and has detection resistance R, and on printed circuit board 10 was located respectively with detecting branch circuit 30 to the control unit 20, printed circuit board 10 printed according to the circuit layout of predetermineeing has a plurality of materials to be the wire of copper foil, and the electric connection between the electronic components that this embodiment relates is realized through the wire that corresponds.

It should be noted that the technical focus of the present invention is how to use the existing structure of the printed circuit board 10 to perform the configuration to obtain a better current protection effect, and the current protection circuit is based on the existing protection circuit, and the related other electronic components and the connection relationship thereof are well known in the prior art and will not be described herein again.

Referring to fig. 3, the detecting branch circuit 30 of the present embodiment includes a first conductive member 31, a first switch circuit 32, a second switch circuit 33 and a second conductive member 34 connected in series in sequence, the first conductive member 31 and the second conductive member 34 are printed on the printed circuit board 10 respectively, and a free end of the first conductive member 31 is connected to the first collecting terminal 21 of the control unit 20, a trigger terminal 321 of the first switch circuit 32 is connected to the first control terminal 22 of the control unit 20, a free end of the second conductive member 34 is connected to the second collecting terminal 23 of the control unit 20, a trigger terminal 331 of the second switch circuit 33 is connected to the second control terminal 24 of the control unit 20, and the control unit 20 monitors a voltage or a current of the detecting branch circuit 30 and controls on/off of the first switch circuit 32 and the second switch circuit 33.

Preferably, the first switch circuit 32 and the second switch circuit 33 are field effect transistors of type AON7422, which implement switching operation, and have high reliability and low cost. Of course, the first switch circuit 32 and the second switch circuit 33 may also be switches such as chip control switches, switch circuits built by hardware, and the like, and are not limited herein.

Referring to fig. 3, in order to make the first and second conductive members 31 and 34 have a rectangular shape so as to calculate impedance, the free end of the first conductive member 31 is electrically connected to the first collecting terminal 21 of the control unit 20 through a corresponding conductive wire, and the free end of the second conductive member 34 is electrically connected to the second collecting terminal 23 of the control unit 20 through a corresponding conductive wire, thereby preventing a non-rectangular shape from being formed due to the direct electrical connection of the first and second conductive members 31 and 34 to the control unit 20.

The first conductive device 31 has a first resistance R1, the second conductive device 34 has a second resistance R2, the first switching circuit 32 has a third resistance R3, the second switching circuit 33 has a fourth resistance R4, and the resistance value of the detection resistance R is the sum of the resistance values of the first resistance R1, the second resistance R2, the third resistance R3, and the fourth resistance R4. in this embodiment, the first conductive device 31 and the second conductive device 34 have specific lengths, widths, and thicknesses with respect to the conductive wires, and when the size and the material of the first conductive device 31/the second conductive device 34 are determined, they have a fixed impedance that can be intuitively calculated.

Preferably, the first conductive member 31 and the second conductive member 34 are made of copper foils, which are the same as the conductive wires of the printed circuit board 10, and are made of copper foils commonly used in the printed circuit board 10, so as to facilitate printing on existing printing equipment. Since the first conductive member 31, the second conductive member 34 and the conductive wire of the present embodiment are made of the same material, the first conductive member 31, the second conductive member 34 and the conductive wire can be manufactured on the printed circuit board 10 by one-time printing. In another preferred embodiment, if the first conductive member 31, the second conductive member 34 and the conductive wires are made of different materials, the conductive wires may be printed on the printed circuit board 10, and then the first conductive member 31 and the second conductive member 34 may be assembled on the printed circuit board 10 by welding, fitting, screwing, and the like, which is not limited herein. It should be noted that, when the first conductive member 31 and the second conductive member 34 are assembled on the printed circuit board 10 by welding, fitting, screwing, etc., it is necessary to ensure that the height of the first conductive member 31 and the second conductive member 34 protruding from the surface of the printed circuit board 10 is within a reasonable range, so as to prevent the protruding portions of the first conductive member 31 and the second conductive member 34 from affecting other electronic components.

Referring to fig. 3, the control unit 20 detects a current I flowing through the detecting branch 30, and compares the current I with a predetermined protection current I_AThe on/off of the first switch circuit 32 and the second switch circuit 33 is controlled according to the comparison result. The specific judgment process is as follows: if the current I is less than the protection current I_A，The control unit 20 controls the first switching circuit 32 and the second switching circuit 33 to remain on; if the present current I is greater than or equal to the protection current I_A，The control unit 20 controls the first switching circuit 32 and the second switching circuit 33 to be turned off. Specifically, the control unit 20 is preset with an overcurrent protection threshold voltage V_AProtection current I_AThreshold voltage of overcurrent protection V_AA detection resistor R, so that the required impedance of the detection resistor R can be calculated by the above formula to design the first switch circuit 32 and the second switch circuit33, in the same size. The judgment process related to the control unit 20 of this embodiment may be implemented by an algorithm, or may be implemented by building a hardware circuit, and the circuits implemented by the algorithm and judged by the hardware circuit are commonly used by those skilled in the art, and are not described here.

Referring to fig. 3, the detecting branch circuit 30 of the present invention includes a first conductive member 31, a first switch circuit 32, a second switch circuit 33 and a second conductive member 34 connected in series in sequence, wherein the first conductive member 31 and the second conductive member 34 are printed on the printed circuit board 10, on one hand, the first conductive member 31 and the second conductive member 34 are introduced to match with the impedances of the first switch circuit 32 and the second switch circuit 33 to a reasonable value through the impedances of the first conductive member 31 and the second conductive member 34, so as to satisfy the protection impedance matching required by the protection circuit; on the other hand, the first conductive member 31 and the second conductive member 34 are printed on the printed circuit board 10 respectively, so that space resources on the printed circuit board 10 do not need to be occupied, other electronic components do not need to be introduced, product space is not occupied, product cost is not increased, the protection circuit is suitable for directly transforming the existing protection circuit, the required protection impedance of the protection circuit can be set to be a reasonable value, and the applicability is high.

The above disclosure is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the scope of the present invention, therefore, the present invention is not limited by the appended claims.