Battery equalization circuit of vehicle, battery management system and vehicle

Abstract

The utility model provides a battery equalization circuit of a vehicle, a battery management system and the vehicle, the battery equalization circuit is connected with a battery cell unit, the battery cell unit at least comprises two battery cells which are connected in series, and the battery equalization circuit comprises equalization starting branches which are in one-to-one correspondence with the battery cells; the equalization starting branch starts equalization under the condition that the voltage difference between the battery cells meets an equalization starting condition; the equalization starting branch comprises an equalization resistor, a current-limiting resistor, a control end resistor and an equalization switch, and the equalization switch controls whether to enter a passive equalization mode or not. According to the battery equalization circuit, only the control end resistor is arranged on the conduction loop of the equalization switch, branch voltage division is avoided, the actual current and equalization starting voltage of the control end of the equalization switch are improved, and the battery equalization circuit has good equalization efficiency.

Description

Technical Field

[0001] The utility model relates to the technical field of vehicles, and in particular to a battery equalization circuit of a vehicle, a battery management system and a vehicle. Background Art

[0002] Under the advocacy of green energy, power batteries, as the main power source of new energy electric vehicles, play an irreplaceable role in the whole vehicle system. Power battery packs (cell units) are usually composed of multiple batteries (cells). When each battery is produced, due to different manufacturing materials and production processes, the internal resistance and capacity of the battery itself will have certain differences. In addition, the environment during use, such as installation location, heat dissipation conditions, etc., will cause the performance of each battery in the battery pack to be inconsistent after long-term use, resulting in high-energy batteries being easily overcharged and low-energy batteries being easily over-discharged, reducing the battery's use time and shortening the battery's service life. To address this problem, the battery management system (BMS) must be equipped with a balancing function to ensure safety and stability. In order to enable the battery pack to achieve its ideal use time, the battery pack needs to be balanced.

[0003] There are two main balancing technologies at this stage: passive balancing and active balancing. Active balancing is to transfer the energy of high-energy batteries to low-energy batteries, but the active balancing circuit is more complicated, uses more original components, and has a higher cost, so it is only used in fewer occasions. Passive balancing is to release the energy of high-energy batteries to achieve energy balance in the entire battery pack. It is small in size and low in cost. However, when the existing technology uses passive balancing, there is a voltage divider branch in the conduction circuit of the balancing switch, which causes the actual current at the control end of the balancing switch to be too small, affecting the balancing efficiency. Utility Model Content

[0004] The utility model provides a battery balancing circuit, a battery management system and a vehicle for a vehicle, which are used to solve the defect in the prior art that the actual current of the balancing switch control end is too small, which affects the balancing efficiency. The battery balancing circuit of the utility model has only a control end resistor in the conduction loop of the balancing switch, which avoids branch voltage division, improves the actual current and the balancing start voltage of the balancing switch control end, and has good balancing efficiency.

[0005] The utility model provides a battery balancing circuit for a vehicle, wherein the battery balancing circuit is connected to a battery cell unit, wherein the battery cell unit includes at least two battery cells connected in series, and the battery balancing circuit includes a balancing start branch corresponding to each of the battery cells one by one; the balancing start branch is used to start balancing when the voltage difference between the battery cells meets a balancing start condition; the balancing start branch includes a balancing resistor, a current limiting resistor, a control end resistor and a balancing switch, and the balancing switch is used to control whether to enter a passive balancing mode; the first end of the balancing resistor is connected to the positive electrode of the battery cell, the second end of the balancing resistor is connected to the first end of the balancing switch, the first end of the current limiting resistor is respectively connected to the control end of the balancing switch and the first end of the control end resistor, the second end of the balancing switch and the second end of the current limiting resistor are both connected to the negative electrode of the battery cell, and the second end of the control end resistor of the balancing start branch of the current battery cell is connected to the second end of the control end resistor corresponding to the balancing start branch of another battery cell when balancing is started.

[0006] According to a battery balancing circuit of a vehicle provided by the utility model, it also includes a balancing condition detection branch, which is used to determine the voltage difference between the battery cells; the balancing condition detection branch includes a detection terminal resistor and a voltage stabilizing capacitor; the first end of the detection terminal resistor is connected to the positive electrode of the battery cell, the second end of the detection terminal resistor is connected to the first end of the voltage stabilizing capacitor, and the second end of the voltage stabilizing capacitor is grounded.

[0007] According to a battery balancing circuit for a vehicle provided by the utility model, the balancing switch is a triode, the collector of the triode serves as the first end of the balancing switch, the emitter of the triode serves as the second end of the balancing switch, and the base of the triode serves as the control end of the balancing switch.

[0008] According to a battery balancing circuit of a vehicle provided by the utility model, it also includes a diode, the cathode of the diode is connected to the first common end, the first common end is an end where the control end of the balancing switch, the first end of the current limiting resistor and the first end of the control end resistor are connected, the anode of the diode is connected to the second common end, and the second common end is an end where the second end of the balancing switch and the negative electrode of the battery cell are connected.

[0009] According to a battery equalization circuit for a vehicle provided by the utility model, the diode is a Schottky diode.

[0010] According to a battery balancing circuit for a vehicle provided by the utility model, when the voltage difference between the battery cells is greater than a preset voltage difference threshold, the second end of the control terminal resistor of the current battery cell is connected to the second end of the control terminal resistor of another battery cell through a controllable conductive element.

[0011] According to a battery equalization circuit for a vehicle provided by the utility model, the controllable conductive element is a controllable switch.

[0012] The utility model also provides a battery management system, comprising the above-mentioned battery equalization circuit of the vehicle.

[0013] According to a battery management system provided by the utility model, it also includes the battery cell unit and a control chip; the control chip is used to control the equalization start branch to start equalization according to the voltage difference between the battery cells.

[0014] The utility model also provides a vehicle, comprising the above-mentioned battery management system.

[0015] The utility model provides a battery balancing circuit, a battery management system and a vehicle for a vehicle, wherein the battery balancing circuit is connected to a battery cell unit, the battery cell unit includes at least two battery cells connected in series, and the battery balancing circuit includes a balancing start branch corresponding to each battery cell one by one; the balancing start branch starts balancing when the voltage difference between the battery cells meets the balancing start condition; the balancing start branch includes a balancing resistor, a current limiting resistor, a control end resistor and a balancing switch, and the balancing switch controls whether to enter a passive balancing mode. The battery balancing circuit of the utility model has only a control end resistor in the conduction loop of the balancing switch, which avoids branch voltage division, improves the actual current and balancing start voltage of the balancing switch control end, and has good balancing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0017] Figure 1 The utility model is a structural schematic diagram of a balancing start branch in a battery balancing circuit of a vehicle provided by the utility model.

[0018] Figure 2 It is a principle schematic diagram of a battery equalization circuit for a vehicle provided by the utility model.

[0019] Figure 3 The utility model is a schematic diagram of the principle of the equalization start branch in the battery equalization circuit of the vehicle provided by the utility model.

[0020] Figure 4 It is a schematic diagram of the principle of the battery management system provided by the utility model.

[0021] Reference numerals:

[0022] 1: Balancing resistor; 2: Current limiting resistor; 3: Control end resistor; 4: Balancing switch. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the utility model clearer, the technical solution of the utility model will be described clearly and completely in conjunction with the drawings in the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0024] Power batteries are a new type of energy-saving and environmentally friendly battery, which is widely used in various fields, such as new energy vehicles. However, there are differences in the production process of the battery cells, and in the service process of the battery pack, its initial differences are continuously accumulated, thereby accelerating the imbalance of the single SOC (System On Chip) in the power battery pack, which will not only affect the discharge capacity and discharge power of the entire battery pack, but also significantly affect the usable life of the battery pack. Therefore, the balancing technology of battery packs has attracted more and more attention from domestic and foreign research institutions and electric vehicle manufacturers. At present, the battery pack balancing method is mainly divided into active balancing and passive balancing. The basic principle of active balancing is to transfer the charge of the high-power single cell to the low-power single cell; while the basic principle of passive balancing is to dissipate the high-power single cell through resistance discharge. However, when the prior art adopts passive balancing, there is a voltage divider branch in the conduction circuit of the balancing switch, which causes the actual current at the control end of the balancing switch to be small, affecting the balancing efficiency.

[0025] Please refer to Figure 1 , Figure 1 The utility model provides a schematic diagram of the structure of the equalization start branch in the battery equalization circuit of the vehicle.

[0026] In order to solve the technical problems existing in the prior art, the utility model provides a battery balancing circuit for a vehicle, the battery balancing circuit is connected to a battery cell unit, the battery cell unit includes at least two battery cells connected in series, and the battery balancing circuit includes a balancing start branch corresponding to each battery cell one by one; the balancing start branch is used to start balancing when the voltage difference between the battery cells meets the balancing start condition; the balancing start branch includes a balancing resistor 1, a current limiting resistor 2, a control end resistor 3 and a balancing switch 4, and the balancing switch 4 is used to control whether to enter a passive balancing mode; the first end of the balancing resistor 1 is connected to the positive electrode of the battery cell, the second end of the balancing resistor 1 is connected to the first end of the balancing switch 4, the first end of the current limiting resistor 2 is respectively connected to the control end of the balancing switch 4 and the first end of the control end resistor 3, the second end of the balancing switch 4 and the second end of the current limiting resistor 2 are both connected to the negative electrode of the battery cell, and the second end of the control end resistor 3 of the balancing start branch of the current battery cell is connected to the second end of the control end resistor 3 corresponding to the balancing start branch of another battery cell when balancing is started.

[0027] In this embodiment, when the voltage difference between the cells reaches the preset balancing start voltage (balancing start condition), the control terminal resistor 3 of the current cell is connected to the control terminal resistor 3 of another cell, and the control terminal current of the current cell is pulled up to the conduction current, and then the balancing switch 4 of the current cell is turned on to enter the passive balancing mode. The battery balancing circuit of the utility model has only the control terminal resistor 3 in the conduction loop of the balancing switch 4, which avoids branch voltage division, improves the actual current and the balancing start voltage of the control terminal of the balancing switch 4, and has good balancing efficiency.

[0028] In addition, when balancing is started, the connection control between the control terminal resistor 3 of the current battery cell and the control terminal resistor 3 of another battery cell can be controlled by the control chip, and the present invention does not make any special limitation here.

[0029] The balancing resistor 1 is the resistor for balancing the current in the path between the cells; the current limiting resistor 2 is the resistor for limiting the current in the path between the second end of the balancing switch 4 and the control end of the balancing switch 4; and the control end resistor 3 is the resistor for determining the current in the control end path of the balancing switch 4.

[0030] Of course, in order to prevent the balancing switch 4 from being damaged by excessive current during the start-up balancing process, corresponding protection elements may also be provided, and the present invention does not make any special limitation thereto.

[0031] Based on the above embodiments:

[0032] Please refer to Figure 2 , Figure 2 This is a schematic diagram of the principle of a battery equalization circuit for a vehicle provided by the utility model.

[0033] Please refer to Figure 3, Figure 3 The utility model provides a schematic diagram of the principle of the equalization start branch in the battery equalization circuit of the vehicle.

[0034] As a preferred embodiment, it also includes an equilibrium condition detection branch, which is used to determine the voltage difference between the battery cells; the equilibrium condition detection branch includes a detection end resistor and a voltage stabilizing capacitor; the first end of the detection end resistor is connected to the positive electrode of the battery cell, the second end of the detection end resistor is connected to the first end of the voltage stabilizing capacitor, and the second end of the voltage stabilizing capacitor is grounded.

[0035] In this embodiment, the battery balancing circuit further includes a balancing condition detection branch. The voltage difference between the battery cells determined by the balancing condition detection branch can be collected by the control chip, and when the start-up balancing condition is met, the control chip controls the connection of the balancing start-up branches of the two battery cells. The present invention does not make any special limitation here.

[0036] As a preferred embodiment, the balancing switch 4 is a transistor, the collector of the transistor serves as the first end of the balancing switch 4 , the emitter of the transistor serves as the second end of the balancing switch 4 , and the base of the transistor serves as the control end of the balancing switch 4 .

[0037] Of course, the balancing switch 4 can also be a MOS tube, the drain of the MOS tube serves as the first end of the balancing switch 4, the source of the MOS tube serves as the second end of the balancing switch 4, and the gate of the MOS tube serves as the control end of the balancing switch 4. The utility model does not make any special limitation here.

[0038] As a preferred embodiment, it also includes a diode, the cathode of the diode is connected to the first common end, the first common end is an end where the control end of the balancing switch 4, the first end of the current limiting resistor 2 and the first end of the control end resistor 3 are connected, and the anode of the diode is connected to the second common end, the second common end is an end where the second end of the balancing switch 4 and the negative electrode of the battery cell are connected.

[0039] As a preferred embodiment, the diode is a Schottky diode.

[0040] As a preferred embodiment, when the voltage difference between the battery cells is greater than a preset voltage difference threshold, the second end of the control terminal resistor 3 of the current battery cell is connected to the second end of the control terminal resistor 3 of another battery cell through a controllable conductive element.

[0041] As a preferred embodiment, the controllable conductive element is a controllable switch.

[0042] In this embodiment, the battery cell unit includes B1, ..., Bn-1, and Bn battery cells connected in series. The balancing circuits of battery cells Bn and battery cell Bn-1 are used as examples for description. The balancing circuits corresponding to other battery cells can be deduced by analogy, and the utility model will not be described in detail here.

[0043] The first balanced start-up branch corresponding to the battery cell Bn includes a first balanced resistor R1, a first current limiting resistor R4, a first control terminal resistor R3 and a first transistor (balance switch 4) Q1; the first balanced condition detection circuit includes a first detection terminal resistor R2 and a first voltage stabilizing capacitor C1. The second balanced start-up branch corresponding to the battery cell Bn-1 includes a second balanced resistor R5, a second current limiting resistor R8, a second control terminal resistor R7 and a second transistor (balance switch 4) Q2; the second balanced condition detection circuit includes a second detection terminal resistor R6 and a second voltage stabilizing capacitor C2.

[0044] Among them, the first end of the first balancing resistor R1 is connected to the positive electrode of the battery cell Bn, the second end of the first balancing resistor R1 is connected to the first end of the first triode Q1, the first end of the first current limiting resistor R4 is respectively connected to the control end of the first triode Q1 and the first end of the first control end resistor R3, the second end of the first triode Q1 and the second end of the first current limiting resistor R4 are both connected to the negative electrode of the battery cell Bn, and the second end of the first control end resistor R3 is connected to the second end of the second control end resistor R7 when the balancing is started; the first end of the first detection end resistor R3 is connected to the positive electrode of the battery cell Bn, the second end of the first detection end resistor R2 is connected to the first end of the first voltage stabilizing capacitor C1, and the first voltage stabilizing capacitor C 1 is grounded; a first end of the second balancing resistor R5 is connected to the positive electrode of the battery cell Bn-1, the emitter of the first triode Q1, the second end of the first current limiting resistor R4, the first end of the first detection terminal resistor R3 and the negative electrode of the battery cell Bn, a second end of the second balancing resistor R5 is connected to the first end of the second triode Q2, a first end of the second current limiting resistor R8 is respectively connected to the control end of the second triode Q2 and the first end of the second control end resistor R7, a second end of the second triode Q2 and a second end of the second current limiting resistor R8 are both connected to the negative electrode of the battery cell Bn-1; a second end of the second detection terminal resistor R6 is connected to the first end of the second voltage stabilizing capacitor C2, and a second end of the second voltage stabilizing capacitor C2 is grounded.

[0045] Of course, in order to protect the first transistor Q1 and the second transistor Q2, a diode, such as a Schottky diode, can also be set. The first balanced startup branch corresponding to the battery cell Bn also includes a first diode D1, and the second balanced startup branch corresponding to the battery cell Bn-1 also includes a second diode D2.

[0046] Among them, the cathode of the first diode D1 is respectively connected to the base of the first triode Q1, the first end of the first current limiting resistor R4, and the first end of the first control terminal resistor R3, and the anode of the first diode D1 is respectively connected to the negative electrode of the battery cell Bn, the emitter of the first triode Q1, the second end of the first current limiting resistor R4, the positive electrode of the battery cell Bn-1, the first end of the second balancing resistor R5, and the first end of the second detection terminal resistor R6. The cathode of the second diode D2 is respectively connected to the base of the second triode Q2, the first end of the second current limiting resistor R8, and the first end of the second control terminal resistor R7, and the anode of the second diode D2 is respectively connected to the negative electrode of the battery cell Bn-1, the emitter of the second triode Q2, and the second end of the second current limiting resistor R8.

[0047] Schottky diodes have extremely fast switching speeds and very low reverse recovery time, and can minimize switching losses. Schottky diodes are different from ordinary PN junction diodes. They use N-type semiconductor materials combined with metals to form a metal-semiconductor junction. Schottky diodes have advantages over ordinary diodes such as lower forward voltage drop and shorter reverse charge recovery time (within 10ns).

[0048] The principle of the battery balancing circuit of this embodiment is as follows:

[0049] At time t0, the voltage difference between cells Bn, Bn-1…B1 cannot reach the equilibrium condition, the internal switch Kn-1 of the chip is disconnected, the equilibrium is not turned on, and the current on the equilibrium resistor 1 is:

[0050]

[0051] At t1, the chip detects that the voltage difference between Bn and Bn-1 reaches the balanced start condition, closes switch Kn-1, the base voltage of Q2 is pulled up, the current reaches the threshold current Ib, the collector and emitter of Q2 are turned on, and passive balance is performed between Bn and Bn-1 through R5. The balanced current is:

[0052]

[0053] Among them, U is the voltage difference between the cells, Vce is the voltage difference between the collector and emitter of the transistor, and R is the resistance value of the balancing resistor 1.

[0054] For ease of understanding, at the initial moment of closing switch Kn-1, the current path is: positive electrode of cell Bn-1 - first diode D1 - first control terminal resistor R3 - second control terminal resistor R7 - second transistor Q2. When the second transistor Q2 is turned on, the current path is positive electrode of cell Bn-1 - second balancing resistor R5 - negative electrode of cell Bn-1.

[0055] The control chip may be but is not limited to an AFE chip.

[0056] The battery management system provided by the present invention is described below. The battery management system described below and the battery balancing circuit described above can be referred to each other.

[0057] Please refer to Figure 4 , Figure 4 This is a schematic diagram of the principle of the battery management system provided by the utility model.

[0058] The utility model also provides a battery management system, comprising the above-mentioned battery equalization circuit of the vehicle.

[0059] As a preferred embodiment, it also includes a battery cell unit and a control chip; the control chip is used to control the equalization start branch to start the equalization according to the voltage difference between the battery cells.

[0060] When the control chip detects that the voltage difference between the cells meets the start-up balancing condition, the control circuit inside the control chip is turned on to start the balancing loop between the cells. The specific circuit structure inside the chip can be adjusted according to actual control, and the utility model does not make any special restrictions here.

[0061] The vehicle provided by the present invention is described below. The vehicle described below and the battery equalization circuit described above can be referred to each other.

[0062] The utility model also provides a vehicle, comprising the above-mentioned battery management system.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the utility model.

Claims

1. A battery equalization circuit for a vehicle, characterized in that: The battery balancing circuit is connected to a battery cell unit, the battery cell unit includes at least two battery cells connected in series, and the battery balancing circuit includes a balancing start branch corresponding to each of the battery cells; the balancing start branch is used to start balancing when the voltage difference between the battery cells meets the balancing start condition; the balancing start branch includes a balancing resistor, a current limiting resistor, a control terminal resistor and a balancing switch, and the balancing switch is used to control whether to enter a passive balancing mode; The first end of the balancing resistor is connected to the positive electrode of the battery cell, the second end of the balancing resistor is connected to the first end of the balancing switch, the first end of the current limiting resistor is respectively connected to the control end of the balancing switch and the first end of the control end resistor, the second end of the balancing switch and the second end of the current limiting resistor are both connected to the negative electrode of the battery cell, and the second end of the control end resistor of the balancing start branch of the current battery cell is connected to the second end of the control end resistor corresponding to the balancing start branch of another battery cell when balancing is started.

2. The battery equalization circuit for a vehicle according to claim 1, characterized in that: It also includes a balanced condition detection branch, wherein the balanced condition detection branch is used to determine the voltage difference between the battery cells; The equilibrium condition detection branch includes a detection end resistor and a voltage-stabilizing capacitor; the first end of the detection end resistor is connected to the positive electrode of the battery cell, the second end of the detection end resistor is connected to the first end of the voltage-stabilizing capacitor, and the second end of the voltage-stabilizing capacitor is grounded.

3. The battery equalization circuit for a vehicle according to claim 1, characterized in that: The balancing switch is a triode, the collector of the triode serves as the first end of the balancing switch, the emitter of the triode serves as the second end of the balancing switch, and the base of the triode serves as the control end of the balancing switch.

4. The battery equalization circuit for a vehicle according to claim 3, characterized in that: It also includes a diode, the cathode of the diode is connected to the first common end, the first common end is an end where the control end of the balancing switch, the first end of the current limiting resistor and the first end of the control end resistor are connected, the anode of the diode is connected to the second common end, and the second common end is an end where the second end of the balancing switch and the negative electrode of the battery cell are connected.

5. The battery equalization circuit for a vehicle according to claim 4, characterized in that: The diode is a Schottky diode.

6. The battery equalization circuit for a vehicle according to claim 1, characterized in that: When the voltage difference between the battery cells is greater than a preset voltage difference threshold, the second end of the control terminal resistor of the current battery cell is connected to the second end of the control terminal resistor of another battery cell through a controllable conduction element.

7. The battery equalization circuit for a vehicle according to claim 6, characterized in that: The controllable conductive element is a controllable switch.

8. A battery management system, characterized in that: A battery balancing circuit for a vehicle comprising any one of claims 1 to 7.

9. The battery management system according to claim 8, characterized in that: It also includes the battery cell unit and a control chip, and the control chip is used to control the equalization start branch to start equalization according to the voltage difference between the battery cells.

10. A vehicle, characterized in that: Includes the battery management system described in claim 8 or 9.

Images