Cell charging and discharging circuit and lithium ion battery pack

Abstract

The utility model provides a battery cell charging and discharging circuit and a lithium ion battery pack, the battery cell charging and discharging circuit comprises a first battery cell, a second battery cell, a charging and discharging protection circuit, connecting wires and an output wire, the connecting wires comprise a first wire, a second wire and a third wire, the third wire is connected between the negative end of the second battery cell and the battery cell negative end control end of the charging and discharging protection circuit, so that when the battery cells are charged and discharged, the current passing through the first battery cell needs to overcome the impedance of the second wire and the third wire, and the current passing through the second battery cell needs to overcome the impedance of the first wire and the third wire; the impedance of the current loop corresponding to the first battery cell is increased, so that the voltage difference between the voltage of the first battery cell and the voltage of the second battery cell is reduced, thereby achieving the purpose of balancing impedance and ensuring the performance of the battery pack.

Description

Technical Field

[0001] The present disclosure relates to the technical field of battery charging and discharging, and particularly to a core charging and discharging circuit and a lithium-ion battery pack. Background Art

[0002] In the design of a 1S2P (one series and two parallel) battery pack of cores, two cores are stacked or placed in parallel, and are connected in the layout circuit on a circuit board. After the two cores are connected in parallel, the overall impedance difference is small during the charging or discharging process, which does not affect the battery performance. However, in some special applications, such as head-mounted Bluetooth headsets, the two cores are placed separately, which is beneficial to requirements such as the utilization of the machine space at the battery application end and the balance of the machine weight.

[0003] Currently, conventional core charging and discharging circuits are as Figure 1 and Figure 2 shown. Among them, two cores (denoted as the first core Cell 1 and the second core Cell 2) are separately arranged through wires. After the positive terminals of the two cores are connected together through wire Line A, they are connected to one end of a protection circuit module (PCM) for charging and discharging. And after the negative terminals of the two cores are connected together through wire Line B, they are connected to the other end of the PCM circuit.

[0004] Since the wires arranged between the two cores have impedance due to their own lengths, when the two cores are in either the charging state or the discharging state, when the current passes through the first core Cell 1, it can enter the PCM circuit without passing through the wire. However, when the current passes through the second core Cell 2, it needs to pass through wire Line A and wire Line B to overcome the impedance caused by the wire length. This makes the voltage of the second core Cell 2 lower than that of the first core Cell 1, and there is a situation where the voltages of the two are inconsistent. If the charging and discharging cycles are continued in the presence of the above situation, the first core Cell 1 will be more likely to be fully charged or enter the low-voltage mode compared to the second core Cell 2, affecting the performance of the core with lower impedance (i.e., the first core Cell 1), and thus affecting the performance of the entire battery pack. Summary of the Utility Model

[0005] The purpose of the present disclosure is to overcome the deficiencies in the prior art, and to provide a core charging and discharging circuit and a lithium-ion battery pack that can balance the impedance in a parallel battery pack and ensure the performance of the battery pack.

[0006] The purpose of the present disclosure is achieved through the following technical solutions:

[0007] A charging and discharging circuit for an electric cell includes a first electric cell, a second electric cell, a charging and discharging protection circuit, a connecting wire, and an output wire. The power supply terminal of the charging and discharging protection circuit is used to output the electric cell current through the output wire. The connecting wire includes a first wire, a second wire, and a third wire. The positive terminal of the second electric cell is electrically connected to the positive terminal of the first electric cell through the first wire. The positive electrode of the first electric cell is electrically connected to the positive terminal control end of the charging and discharging protection circuit. The negative terminal of the second electric cell is electrically connected to the negative terminal of the first electric cell through the second wire. The negative terminal of the second electric cell is also electrically connected to the negative terminal control end of the charging and discharging protection circuit through the third wire to balance the voltages of the first electric cell and the second electric cell. Among them, the resistance value of the first wire is equal to the resistance value of the second wire.

[0008] In one embodiment, the length range of the first wire is 81 mm to 87 mm.

[0009] In one embodiment, the length range of the second wire is 81 mm to 87 mm.

[0010] In one embodiment, the length range of the third wire is 81 mm to 87 mm.

[0011] In one embodiment, the first wire, the second wire, and the third wire have the same length.

[0012] In one embodiment, the charging and discharging protection circuit includes a battery protection unit, a bidirectional switch, a first resistor, and a first capacitor. The positive terminal of the first electric cell is connected to the first end of the first resistor. The first end of the first resistor is connected to the positive power supply. The second end of the first resistor is connected to the upper half end of the first capacitor and the working voltage terminal of the battery protection unit respectively. The lower half end of the first capacitor is connected to the grounding terminal of the battery protection unit, the third wire, and the first end of the bidirectional switch respectively. The control terminal of the bidirectional switch is connected to the charging and discharging control enabling terminal of the battery protection unit. The second end of the bidirectional switch is connected to the negative power supply.

[0013] In one embodiment, the bidirectional switch includes a first field-effect transistor and a second field-effect transistor. The first end of the first field-effect transistor is connected to the third wire. The second end of the first field-effect transistor is connected to the first end of the second field-effect transistor. The control terminal of the first field-effect transistor is connected to the discharge control enabling terminal of the battery protection unit. The control terminal of the second field-effect transistor is connected to the charge control enabling terminal of the battery protection unit. The second end of the second field-effect transistor is connected to the negative power supply.

[0014] In one embodiment, the charge and discharge protection circuit further includes a second resistor and a third resistor. The first end of the second resistor is connected to the voltage detection end of the battery protection unit. The second end of the second resistor is respectively connected to the second end of the bidirectional switch and the first end of the third resistor. The second end of the third resistor is connected to the battery usage detection end.

[0015] In one embodiment, the third resistor is an NTC thermistor.

[0016] A lithium-ion battery pack includes the cell charge and discharge circuit according to any one of the above embodiments.

[0017] Compared with the prior art, the present disclosure has at least the following advantages:

[0018] In the above cell charge and discharge circuit, a connecting wire is provided between the first cell and the second cell, which includes a first wire, a second wire, and a third wire. Among them, the third wire is connected between the negative end of the second cell and the cell negative end control end of the charge and discharge protection circuit. When the cell is charged and discharged, the current passing through the first cell needs to overcome the impedance of the second wire and the third wire, and the current passing through the second cell needs to overcome the impedance of the first wire and the third wire. Furthermore, the current loop corresponding to the first cell increases the impedance amount, so that the voltage difference between its voltage and the voltage of the second cell is reduced, achieving the purpose of balancing the impedance and ensuring the performance of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present disclosure, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0020] Figure 1 is a schematic diagram of a conventional cell charge and discharge circuit in the prior art;

[0021] Figure 2 is Figure 1 the circuit diagram of the conventional cell charge and discharge circuit shown;

[0022] Figure 3 is a schematic diagram of a cell charge and discharge circuit in one embodiment;

[0023] Figure 4 is Figure 3 the circuit diagram of the cell charge and discharge circuit shown.

[0024] Reference numerals: 10, battery cell charging and discharging circuit; 100, first battery cell; 200, second battery cell; 300, charging and discharging protection circuit; 400, connecting wire; 410, first wire; 420, second wire; 430, third wire; 500, output wire; U1, battery protection unit; U2, bidirectional switch; R1, first resistor; R2, second resistor; RT, third resistor; C1, first capacitor; M1, first field effect transistor; M2, second field effect transistor. Detailed implementation manners

[0025] To facilitate the understanding of the present disclosure, the present disclosure will be described more comprehensively below with reference to the relevant drawings. The preferred embodiments of the present disclosure are shown in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the understanding of the disclosure content of the present disclosure more thorough and comprehensive.

[0026] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only embodiments.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present disclosure belongs. The terms used in the description of the present disclosure in this specification are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0028] To better understand the technical solutions and beneficial effects of the present disclosure, the present disclosure will be further described in detail below with specific embodiments:

[0029] Please refer to Figure 3 and Figure 4, which is the charging and discharging circuit 10 of a cell according to an embodiment of the present invention, includes a first cell 100, a second cell 200, a charging and discharging protection circuit 300, a connecting wire 400, and an output wire 500. The power supply terminal of the charging and discharging protection circuit 300 is used to output the cell current through the output wire 500. The connecting wire 400 includes a first wire 410, a second wire 420, and a third wire 430. The positive terminal of the second cell 200 is electrically connected to the positive terminal of the first cell 100 through the first wire 410. The positive electrode of the first cell 100 is electrically connected to the cell positive terminal control terminal of the charging and discharging protection circuit 300. The negative terminal of the second cell 200 is electrically connected to the negative terminal of the first cell 100 through the second wire 420. The negative terminal of the second cell 200 is also electrically connected to the cell negative terminal control terminal of the charging and discharging protection circuit 300 through the third wire 430 to balance the voltages of the first cell 100 and the second cell 200. Among them, the resistance value of the first wire 410 is equal to the resistance value of the second wire 420.

[0030] In this embodiment, a connecting wire 400 is provided between the first cell 100 and the second cell 200 in the cell charging and discharging circuit 10, which includes a first wire 410, a second wire 420, and a third wire 430. Among them, the third wire 430 is connected between the negative terminal of the second cell 200 and the cell negative terminal control terminal of the charging and discharging protection circuit 300. When the cell is charged and discharged, the current passing through the first cell 100 needs to overcome the impedance of the second wire 420 and the third wire 430, and the current passing through the second cell 200 needs to overcome the impedance of the first wire 410 and the third wire 430. Furthermore, the impedance amount of the current loop corresponding to the first cell 100 increases, so that the voltage difference between its voltage and the voltage corresponding to the second cell 200 decreases, achieving the purpose of balancing the impedance and ensuring the performance of the battery pack. Moreover, since the resistance value of the first wire 410 is equal to the resistance value of the second wire 420, the increased impedance in the charging and discharging loop corresponding to the first cell 100 is the resistance values of the second wire 420 and the third wire 430, and the increased impedance in the charging and discharging loop corresponding to the second cell 200 is the resistance values of the first wire 410 and the third wire 430, so that the increased amount of the charging and discharging equivalent impedance of the first cell 100 is equal to the increased amount of the charging and discharging equivalent impedance of the second cell 200, thereby enabling the charging and discharging currents of the first cell 100 and the second cell 200 to be kept consistent, achieving the effect of balancing the charging and discharging impedance.

[0031] Further, the charge and discharge protection circuit 300 includes a battery protection unit U1, a bidirectional switch U2, a first resistor R1, and a first capacitor C1. The positive terminal of the first battery cell 100 is connected to the first end of the first resistor R1. The first end of the first resistor R1 is connected to the positive power supply. The second end of the first resistor R1 is respectively connected to the upper half end of the first capacitor C1 and the operating voltage terminal of the battery protection unit U1. The lower half end of the first capacitor C1 is respectively connected to the grounding terminal of the battery protection unit U1, the third wire 430, and the first end of the bidirectional switch U2. The control terminal of the bidirectional switch U2 is connected to the charge and discharge control enable terminal of the battery protection unit U1. The second end of the bidirectional switch U2 is connected to the negative power supply.

[0032] It can be understood that after the third wire 430 is used to connect between the negative terminal of the second battery cell 200 and the first end of the bidirectional switch U2, in the case of charging the battery pack, the current flowing through the first battery cell 100 needs to overcome the impedance of the second wire 420 and the third wire 430 before it can reach the bidirectional switch U2 and finally output from the negative power supply terminal. That is, the current direction is "positive terminal of the battery cell B+ → negative terminal of the battery cell B- → second wire 420 → negative terminal of the battery cell B1- → third wire 430 → bidirectional switch U2". The current flowing through the second battery cell 200 needs to overcome the impedance of the first wire 410 and the third wire 430 before it can reach the bidirectional switch U2. That is, the current direction is "positive terminal of the battery cell B+ → first wire 410 → positive terminal of the battery cell B1+ → negative terminal of the battery cell B1- → third wire 430 → bidirectional switch U2". Similarly, in the case of discharging the battery pack, the current flowing through the first battery cell 100 is in the direction of "bidirectional switch U2 → third wire 430 → negative terminal of the battery cell B1- → second wire 420 → negative terminal of the battery cell B- → positive terminal of the battery cell B+". The current flowing through the second battery cell 200 is in the direction of "bidirectional switch U2 → third wire 430 → negative terminal of the battery cell B1- → positive terminal of the battery cell B1+ → first wire 410 → positive terminal of the battery cell B+". In this way, when the charging current or the discharging current passes through the first battery cell 100 and the second battery cell 200, the third wire 430 plays a role in offsetting the line impedance of the second wire 420. As a result, the current flowing through the first battery cell 100 and the second battery cell 200 needs to overcome the impedance of the wire, so that the PCM detection voltage point is located on the second battery cell 200, achieving the effect of balancing the impedance existing between the first battery cell 100 and the second battery cell 200. Thus, the voltage difference between the two battery cells can be reduced, and the normal performance of the battery cells can be exerted. Of course, the first battery cell 100 and the second battery cell 200 can also be connected through a flexible printed circuit board (FPC).

[0033] Furthermore, the bidirectional switch U2 includes a first field-effect transistor M1 and a second field-effect transistor M2. The first end of the first field-effect transistor M1 is connected to the third wire 430. The second end of the first field-effect transistor M1 is connected to the first end of the second field-effect transistor M2. The control end of the first field-effect transistor M1 is connected to the discharge control enable end of the battery protection unit U1. The control end of the second field-effect transistor M2 is connected to the charge control enable end of the battery protection unit U1. The second end of the second field-effect transistor M2 is connected to the negative power supply terminal. Specifically, the first field-effect transistor M1 is a discharge MOS transistor, and the second field-effect transistor M2 is a charge MOS transistor.

[0034] It can be understood that when the battery pack is charging, the battery protection unit U1 enables a high-level signal to the charge MOS transistor. After the charge MOS transistor is turned on, the current outputs from the positive power supply terminal through the first battery cell 100 and the second battery cell 200 respectively to the negative power supply terminal to perform the charging operation. When the battery pack is discharging, the battery protection unit U1 enables a high-level signal to the discharge MOS transistor. After the discharge MOS transistor is turned on, the current outputs from the negative power supply terminal through the first battery cell 100 and the second battery cell 200 to the positive power supply terminal to perform the discharging operation.

[0035] In this embodiment, both the first field-effect transistor M1 and the second field-effect transistor M2 are NMOS transistors. The first end of the first field-effect transistor M1 is the source electrode, the second end is the drain electrode, and the control end is the gate electrode. The first end of the second field-effect transistor M2 is the drain electrode, the second end is the source electrode, and the control end is the gate electrode.

[0036] In one of the embodiments, the length range of the first wire 410 is 81 mm to 87 mm. In this embodiment, the length of the first wire 410 is 84 mm.

[0037] In one of the embodiments, the length range of the second wire 420 is 81 mm to 87 mm. In this embodiment, the length of the second wire 420 is 84 mm.

[0038] In one of the embodiments, the length range of the third wire 430 is 81 mm to 87 mm. In this embodiment, the length of the third wire 430 is 84 mm.

[0039] In one embodiment, the first wire 410, the second wire 420, and the third wire 430 have equal lengths. It can be understood that the impedance of the first wire 410, the second wire 420, and the third wire 430 is related to their own lengths. Generally, the longer the wire, the greater the impedance. To better balance the wire impedance existing in the first battery cell 100 and the second battery cell 200, the first wire 410, the second wire 420, and the third wire 430 are set to have equal lengths, so that the wire impedance that needs to be overcome when passing through the first battery cell 100 is equal to the wire impedance that needs to be overcome when passing through the second battery cell 200, better ensuring that the voltage difference between the first battery cell 100 and the second battery cell 200 is effectively reduced, thereby ensuring the normal performance of the battery cells. In this embodiment, the lengths of the first wire 410, the second wire 420, and the third wire 430 are all 84 mm.

[0040] In one embodiment, the charge and discharge protection circuit 300 further includes a second resistor R2 and a third resistor RT. The first end of the second resistor R2 is connected to the voltage detection terminal of the battery protection unit U1. The second end of the second resistor R2 is respectively connected to the second end of the bidirectional switch U2 and the first end of the third resistor RT. The second end of the third resistor RT is connected to the battery usage detection terminal. It can be understood that when charging or discharging the battery pack, the voltage detection terminal of the battery protection unit U1 is used to detect the overcharge / overdischarge protection state of the battery cell. When the over-discharge / overcharge protection condition of the battery cell is reached, the discharge control enable terminal / charge control enable terminal of the battery protection unit U1 becomes low level, and then the discharge MOS transistor / charge MOS transistor is turned off to prevent the battery cell from further discharging / charging.

[0041] In one embodiment, the third resistor RT is an NTC thermistor. It can be understood that the NTC thermistor is a negative temperature coefficient (Negative Temperature Coefficient) thermistor, and its resistance value decreases with the increase of temperature. It can be applied to the charge and discharge protection circuit 300. The device main board can monitor the temperature inside the battery in real time through this thermistor. When the battery temperature rises, the temperature of the NTC thermistor also rises, and its resistance value decreases. On the contrary, when the battery temperature drops, the temperature of the NTC thermistor also drops, and its resistance value rises, and the current decreases. When the device main board detects that the resistance value of the NTC thermistor exceeds the resistance values corresponding to the set high and low temperatures, it will issue an instruction to stop charging and discharging, ensuring that the battery is not prone to abnormal states.

[0042] The present disclosure also provides a lithium-ion battery pack, including the battery cell charge and discharge circuit 10 of any one of the above embodiments.

[0043] Compared with the prior art, the present disclosure has at least the following advantages:

[0044] For the above-mentioned battery cell charge and discharge circuit 10, a connecting wire 400 is arranged between the first battery cell 100 and the second battery cell 200, which includes a first wire 410, a second wire 420 and a third wire 430. Among them, the third wire 430 is connected between the negative terminal of the second battery cell 200 and the battery cell negative terminal control end of the charge and discharge protection circuit 300. When the battery cell is charged and discharged, the current passing through the first battery cell 100 needs to overcome the impedance of the second wire 420 and the third wire 430, and the current passing through the second battery cell 200 needs to overcome the impedance of the first wire 410 and the third wire 430. Furthermore, the current loop corresponding to the first battery cell 100 increases the impedance amount, so that the voltage difference between its voltage and the voltage of the second battery cell 200 decreases, achieving the purpose of balancing the impedance and ensuring the performance of the battery pack.

[0045] The above embodiments only represent several implementation manners of the present disclosure, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the disclosed patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present disclosure, several deformations and improvements can still be made, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure patent shall be subject to the appended claims.

Claims

1. A cell charge and discharge circuit, comprising a first cell, a second cell, a charge and discharge protection circuit, a connecting wire and an output wire. The power supply end of the charge and discharge protection circuit is used to output cell current through the output wire. It is characterized in that, the connecting wire includes a first wire, a second wire and a third wire. The positive end of the second cell is electrically connected to the positive end of the first cell through the first wire. The positive electrode of the first cell is electrically connected to the cell positive end control terminal of the charge and discharge protection circuit. The negative end of the second cell is electrically connected to the negative end of the first cell through the second wire. The negative end of the second cell is also electrically connected to the cell negative end control terminal of the charge and discharge protection circuit through the third wire to balance the voltages of the first cell and the second cell; wherein, the resistance value of the first wire is equal to the resistance value of the second wire.

2. The battery cell charging and discharging circuit according to claim 1, wherein The length range of the first wire is 81 mm to 87 mm.

3. The cell charging and discharging circuit according to claim 2, wherein, The length range of the second wire is 81 mm to 87 mm.

4. The cell charging and discharging circuit according to claim 3, characterized in that, The length range of the third wire is 81 mm to 87 mm.

5. The cell charging and discharging circuit according to claim 4, wherein The first wire, the second wire and the third wire have the same length.

6. The charging and discharging circuit of the battery cell according to claim 1, wherein The charge and discharge protection circuit includes a battery protection unit, a bidirectional switch, a first resistor and a first capacitor. The positive end of the first cell is connected to the first end of the first resistor. The first end of the first resistor is connected to the positive power supply. The second end of the first resistor is respectively connected to the upper half end of the first capacitor and the working voltage terminal of the battery protection unit. The lower half end of the first capacitor is respectively connected to the grounding terminal of the battery protection unit, the third wire and the first end of the bidirectional switch. The control terminal of the bidirectional switch is connected to the charge and discharge control enable terminal of the battery protection unit. The second end of the bidirectional switch is connected to the negative power supply.

7. The cell charging and discharging circuit according to claim 6, wherein The bidirectional switch includes a first field effect transistor and a second field effect transistor. The first end of the first field effect transistor is connected to the third wire. The second end of the first field effect transistor is connected to the first end of the second field effect transistor. The control terminal of the first field effect transistor is connected to the discharge control enable terminal of the battery protection unit. The control terminal of the second field effect transistor is connected to the charge control enable terminal of the battery protection unit. The second end of the second field effect transistor is connected to the negative power supply.

8. The battery cell charging and discharging circuit according to claim 6, wherein The charge and discharge protection circuit further includes a second resistor and a third resistor. The first end of the second resistor is connected to the voltage detection terminal of the battery protection unit. The second end of the second resistor is respectively connected to the second end of the bidirectional switch and the first end of the third resistor. The second end of the third resistor is connected to the battery usage detection terminal.

9. The cell charge and discharge circuit according to claim 8, wherein The third resistor is an NTC thermistor.

10. A lithium-ion battery pack, characterized in that, A cell charge and discharge circuit according to any one of claims 1-9.

Images