Inductance type active and passive equalization circuit and battery management system

Abstract

The invention provides an inductance type active and passive equalization circuit and a battery management system, and relates to the technical field of battery equalization, the inductance type active and passive equalization circuit comprises an inductor, the first end of the inductor is respectively connected with the positive electrode of a single battery in a battery module and one end of a passive equalization switch corresponding to the single battery through a first switch device; the second end of the inductor is connected with the negative electrode of the single battery and the other end of the passive equalization switch through the second switching device. The inductor is also connected in parallel with a charging loop and a load loop; when the passive equalization switch is turned on, the first switching device and the second switching device are turned on, the single battery charges the inductor, when the passive equalization switch is turned off, the first switching device and the second switching device are turned off, and the inductor selectively discharges through the charging loop to achieve active equalization or discharges through the load loop to achieve passive equalization. The beneficial effects are that the same circuit can realize both passive equalization and active equalization, and the equalization mode is more flexible.

Description

Technical Field

[0001] The present invention relates to the technical field of battery balancing, and in particular to an inductive active and passive balancing circuit and a battery management system. Background Art

[0002] Lithium-ion battery cells (or battery units) must operate within a specified voltage range. Beyond their voltage limits, the battery may be damaged, resulting in a risk of loss of control. This is because the cells will be damaged if they are not operated within the specified voltage range. This means that when a cell reaches the upper or lower voltage limit, the charging or discharging of the entire battery pack must be stopped, even if other cells still have power remaining. Therefore, the SOC of all series-connected cells needs to be adjusted to the same value.

[0003] One of the existing SOC adjustment methods is passive balancing, which consumes excess energy through resistors, such as Figure 1 As shown, the energy balance of each battery is achieved. Currently, the commonly used passive balancing methods are as follows: Figure 2 As shown in the figure, when the battery management chip controls the internal passive balancing switch to turn on, the corresponding passive balancing loop is turned on, and the single battery B1 and the single battery B3 consume battery energy through the two balancing resistors R in the loop, thereby achieving the effect of consuming energy. When multiple batteries turn on passive balancing at the same time, the battery management chip and multiple balancing resistors R will generate a lot of heat, making the thermal control of the system board complicated.

[0004] Another existing SOC adjustment method is active balancing, which redistributes energy and transfers the energy of high-energy cells to low-energy cells, such as Figure 3 Currently, the commonly used active balancing methods are as follows: Figure 4 As shown, if the battery B1 is too charged, the main control chip controls the MOS tube Q1d and MOS tube Q1c to open, discharge to the inductor L1, and then closes the MOS tube Q1d and MOS tube Q1c, opens the MOS tube Q2d and MOS tube Q2c, and charges the single battery B2 to achieve energy transfer. However, it requires an additional main control circuit and more MOS switches. Each battery MOS switch also requires a pre-drive circuit, and the circuit logic is complex. In the existing mass-produced passive balancing BMS products, the implementation is complex, and even after the active balancing function is realized, there is no passive balancing function.

[0005] Therefore, there is an urgent need to improve the existing balancing methods. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides an inductive active and passive balancing circuit, comprising:

[0007] An inductor, wherein a first end of the inductor is respectively connected to a positive electrode of a single battery in the battery module and one end of a passive balancing switch corresponding to the single battery through a first switching device, and a second end of the inductor is respectively connected to a negative electrode of the single battery and the other end of the passive balancing switch through a second switching device;

[0008] The inductor is also connected in parallel with a charging circuit and a load circuit;

[0009] When the passive balancing switch is turned on, the first switch device and the second switch device are turned on, and the single battery charges the inductor. When the passive balancing switch is turned off, the first switch device and the second switch device are turned off, and the inductor can be selectively discharged through the charging circuit to achieve active balancing or discharged through the load circuit to achieve passive balancing.

[0010] Preferably, the first switch device is a P-type transistor, the emitter of the P-type transistor is connected to the positive electrode of the single battery and one end of the passive balancing switch, the collector is connected to the first end of the inductor, and the base is connected to one end of the passive balancing switch;

[0011] The second switch device is an N-type transistor, the emitter of which is connected to the negative electrode of the single battery and the other end of the passive balancing switch, the collector is connected to the second end of the inductor, and the base is connected to the other end of the passive balancing switch.

[0012] Preferably, the emitter of the P-type transistor is connected to one end of the passive balancing switch via a first resistor, and / or the emitter of the N-type transistor is connected to the other end of the passive balancing switch via a second resistor.

[0013] Preferably, the base of the P-type transistor is connected to one end of the passive balancing switch via a third resistor or a first capacitor;

[0014] and / or

[0015] The emitter of the N-type transistor is connected to the other end of the passive balancing switch via a fourth resistor or a second capacitor.

[0016] Preferably, the charging circuit includes a charged device and a charging control switch connected in series. When the charging control switch is turned on, the inductor discharges through the charging circuit to achieve active balancing. When the charging control switch is turned off, the inductor discharges through the load circuit to achieve passive balancing.

[0017] Preferably, the negative electrode of the power supply of the charged device is connected to the anode of the first diode, the cathode of the first diode is connected to the first end of the inductor, the positive electrode of the power supply of the charged device is connected to the cathode of the second diode, and the anode of the second diode is connected to the second end of the inductor;

[0018] The two ends of the charging control switch are respectively connected to the negative electrode of the power supply of the charged device and the anode of the first diode;

[0019] Or two ends of the charging control switch are respectively connected to the positive pole of the power supply of the charged device and the cathode of the second diode.

[0020] Preferably, the charged device is the battery module or an external charging power source.

[0021] Preferably, the load circuit includes a fifth resistor, one end of the fifth resistor is connected to the anode of the first diode, the other end is connected to the positive electrode of the voltage regulator diode, and the negative electrode of the voltage regulator diode is connected to the cathode of the second diode.

[0022] Preferably, one end of the fifth resistor is connected to the anode of the first diode through a third diode, and the anode of the third diode is connected to one end of the fifth resistor.

[0023] The present invention also provides a battery management system, comprising:

[0024] A battery management chip, wherein the battery management chip is provided with a plurality of pin groups corresponding to each single battery in the battery module, and the passive balancing switch is provided between two pins in each pin group;

[0025] The above-mentioned inductive active and passive balancing circuit is arranged between each of the single batteries and the corresponding pin group.

[0026] The above technical solution has the following advantages or beneficial effects:

[0027] 1) The same circuit can achieve both passive and active balancing, and the balancing method is more flexible;

[0028] 2) It is possible to add a small amount of circuits to the existing passive equalization to realize the active equalization function and reduce the development cycle;

[0029] 3) Compared with the existing active balancing circuit, the number of logic switches is reduced, and active balancing is achieved with fewer components, saving costs;

[0030] 4) The power consumption in passive balancing is realized through the load circuit, and centralized heat dissipation is achieved, which solves the problems of decentralized thermal management and difficult thermal management in existing passive balancing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the principle of passive equalization;

[0032] Figure 2 This is a diagram of an existing passive equalization circuit;

[0033] Figure 3 This is a schematic diagram of the principle of active equalization;

[0034] Figure 4 This is a diagram of an existing active equalization circuit;

[0035] Figure 5 A circuit diagram of an inductive active and passive balancing circuit in a preferred embodiment of the present invention;

[0036] Figure 6 A circuit diagram of an inductive active and passive balancing circuit in a preferred embodiment of the present invention;

[0037] Figure 7 In a preferred embodiment of the present invention, the charged device is an equivalent circuit diagram of an external charging power source and adopts a high-side drive;

[0038] Figure 8 In a preferred embodiment of the present invention, the charged device is an external charging power source and adopts an equivalent circuit diagram of a low-side driver;

[0039] Fig. 9 This is a schematic diagram of the structure of a battery management system in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. The present invention is not limited to this embodiment, and other embodiments may also fall within the scope of the present invention as long as they conform to the gist of the present invention.

[0041] In a preferred embodiment of the present invention, based on the above problems existing in the prior art, an inductive active and passive balancing circuit is provided. Figure 5 As shown, including:

[0042] An inductor L, wherein a first end of the inductor L is respectively connected to a positive electrode of a single battery 21 in the battery module 2 and one end of a passive balancing switch 3 corresponding to the single battery 21 through a first switch device 1, and a second end of the inductor L is respectively connected to a negative electrode of the single battery 21 and the other end of the passive balancing switch 3 through a second switch device 4;

[0043] The inductor L is also connected in parallel with a charging circuit 5 and a load circuit 6;

[0044] When the passive balancing switch 3 is turned on, the first switch device 1 and the second switch device 4 are turned on, and the single battery 21 charges the inductor L. When the passive balancing switch 3 is turned off, the first switch device 1 and the second switch device 4 are turned off, and the inductor L can be selectively discharged through the charging circuit 5 to achieve active balancing or discharged through the load circuit 6 to achieve passive balancing.

[0045] Specifically, in a common battery BMS management system, the battery management chip is responsible for voltage detection, temperature detection, balancing management, and corresponding detection and control work of the single cells in the battery pack. Currently, most battery management chips have passive balancing functions. The passive balancing switch 3 in this embodiment is the original battery management system with passive balancing function, which is usually integrated inside the battery management chip.

[0046] Furthermore, the inductive active and passive balancing circuit of the present invention comprises two modules, namely Figure 5 The active and passive balancing control circuit and the load circuit 6 in the dotted box. Among them, the active and passive balancing control circuit can exist in the form of an integrated chip, with 6 pins, namely Pin1, Pin2, Pin3, Pin4, Pin5, and Pin6. In actual use, Pin2 and Pin3 are respectively connected to the positive and negative poles of the single battery 21, Pin1 and Pin4 are respectively connected to the charge and discharge circuit 5, and Pin5 and Pin6 are respectively connected to the two ends of the passive balancing switch 3 corresponding to the single battery 21. The load circuit 6 connects Pin1 and Pin4 of each active and passive balancing control circuit, so that each single battery 21 with excessive energy consumes electrical energy through a unified load circuit 6, thereby realizing centralized heat dissipation of the load circuit, solving the problem of decentralized thermal management and difficult thermal management of existing passive balancing.

[0047] When the battery management chip detects that the cell voltage of one or more cells 21 is higher than that of other cells 21, the corresponding passive balancing switch 3 can be controlled to turn on. At this time, the first switch device 1 and the second switch device 4 are turned on, the cell 21 charges the inductor L, and the inductor L stores energy. When the passive balancing switch 3 is subsequently turned off, the first switch device 1 and the second switch device 4 are turned off, and the cell 21 stops charging the inductor L. According to the inductor characteristics, the current cannot change suddenly, and the energy in the inductor needs to be released. At this time, if the charging circuit 5 is turned on, the inductor L can charge other cells through the charging circuit to achieve active balancing. If the charging circuit 5 is not turned on, the inductor can consume energy through the load circuit 6 to achieve passive balancing.

[0048] It can be seen that the inductive active and passive balancing circuit of the present invention can realize the switching between active balancing and passive balancing, and the balancing has no overvoltage safety risk. In addition, the inductive active and passive balancing circuit of the present invention can be applied in the existing battery management system with passive balancing function, and specifically, a switch such as Figure 5 The active and passive balancing control circuit shown can realize the active balancing function by adding a small amount of circuits on the basis of the existing passive balancing circuit, thereby reducing the development cycle.

[0049] In a preferred embodiment of the present invention, the first switch device 1 is a P-type transistor, the emitter of the P-type transistor is connected to the positive electrode of the single battery 21 and one end of the passive balancing switch 3, the collector is connected to the first end of the inductor L, and the base is connected to one end of the passive balancing switch 3;

[0050] The second switch device 4 is an N-type transistor, the emitter of which is connected to the negative electrode of the single battery 21 and the other end of the passive balancing switch 3 , the collector is connected to the second end of the inductor L, and the base is connected to the other end of the passive balancing switch 3 .

[0051] Specifically, in this embodiment, when the passive balancing switch 3 is turned on, Pin5 and Pin6 are equivalent to a short circuit. At this time, the emitter voltage of the P-type transistor is higher than the base voltage, the base is at a low level, and the P-type transistor is turned on; the emitter voltage of the N-type transistor is lower than the base voltage, the base is at a high level, the N-type transistor is turned on, and the single battery 21 charges the inductor L through the loop formed by Pin2 and Pin3 and the inductor L. When the passive balancing switch 3 is turned off, the P-type transistor and the N-type transistor are turned off, and the inductor L is discharged through Pin1 and Pin4.

[0052] In a preferred embodiment of the present invention, the emitter of the P-type transistor is connected to one end of the passive balancing switch 3 via the first resistor R1, and / or the emitter of the N-type transistor is connected to the other end of the passive balancing switch 3 via the second resistor R2.

[0053] Specifically, in this embodiment, the first resistor R1 and the second resistor R3 are equivalent to the balancing resistors of the existing passive balancing circuit, and can be retained or deleted. When retained, there is no need to select a large resistor, and the resistance value can be 1KΩ, which plays a role in assisting energy consumption. The main energy consumption is still through the load circuit 6.

[0054] In a preferred embodiment of the present invention, Figure 5 As shown, the base of the P-type transistor is connected to one end of the passive balancing switch 3 through the third resistor R3, and / or the emitter of the N-type transistor is connected to the other end of the passive balancing switch 3 through the fourth resistor R4.

[0055] In a preferred embodiment of the present invention, Figure 6 As shown, the base of the P-type transistor is connected to one end of the passive balancing switch 3 through the first capacitor C1, and / or the emitter of the N-type transistor is connected to the other end of the passive balancing switch 3 through the second capacitor C2.

[0056] Specifically, in this embodiment, Figure 6 As shown, by setting the first capacitor C1 and the second capacitor C2, the equalization establishment time can be effectively improved, wherein the first capacitor C1 and the second capacitor C2 can also be replaced by Figure 5The third resistor R3 and the fourth resistor R4 shown increase safety.

[0057] In a preferred embodiment of the present invention, the charging circuit 5 includes a charged device 51 and a charging control switch 52 connected in series. When the charging control switch 52 is turned on, the inductor L discharges through the charging circuit 5 to achieve active balancing. When the charging control switch 52 is turned off, the inductor L discharges through the load circuit 6 to achieve passive balancing.

[0058] In a preferred embodiment of the present invention, the negative electrode of the power supply of the charged device 51 is connected to the anode of the first diode D1, the cathode of the first diode D1 is connected to the first end of the inductor L, the positive electrode of the power supply of the charged device 51 is connected to the cathode of the second diode D2, and the anode of the second diode D2 is connected to the second end of the inductor L;

[0059] Two ends of the charging control switch 52 are respectively connected to the negative electrode of the power supply of the charged device 51 and the anode of the first diode D1;

[0060] Or the two ends of the charging control switch 52 are connected to the positive pole of the power supply of the charged device 51 and the cathode of the second diode D2 respectively.

[0061] In a preferred embodiment of the present invention, the charged device 51 is a battery module or an external charging power source.

[0062] Specifically, in this embodiment, when the charged device 51 is a battery module, active and passive balancing of the discharge process of each single battery 21 during the use of the battery module is effectively achieved. When the charged device 51 is an external charging power source, active and passive balancing of the charging process of each single battery 21 during the charging process of the battery module is effectively achieved.

[0063] Further, taking the charged device 51 as an external charging power source as an example, the present invention can be applied to a BMS high-side drive scenario, such as Figure 7As shown, at this time, Pin1 of the active and passive balancing control circuit is connected to the positive pole of the external charging power supply Bat through the charging control switch 52, and Pin4 is connected to the negative pole of the external charging power supply Bat, that is, the two ends of the charging control switch 52 are respectively connected to the positive pole of the power supply of the charged device 51 and the cathode of the second diode D2. It can be seen that when the charging control switch 52 is turned on, the charging circuit formed by the active and passive balancing control circuit, the charging control switch 52, and the external charging power supply Bat is turned on, and the inductor L in the active and passive balancing control circuit charges the external charging power supply Bat to achieve active balancing. When the charging control switch 52 is turned off, the charging circuit formed by the active and passive balancing control circuit, the charging control switch 52, and the external charging power supply Bat is disconnected, and the active and passive balancing control circuit is connected to the load circuit 6 to achieve passive balancing. Active balancing and passive balancing can be selected by turning on and off the charging control switch 52. Thereby, active and passive balancing switching is achieved, and balancing has no overvoltage safety risk.

[0064] Taking the charged device 51 as an external charging power source as an example, the present invention can be applied to BMS low-side driving scenarios, such as Figure 8 As shown, at this time, Pin4 of the active and passive balancing control circuit is connected to the negative pole of the power supply of the external charging power supply Bat through the charging control switch 52, and Pin1 is connected to the positive pole of the power supply of the external charging power supply Bat, that is, the two ends of the charging control switch 52 are respectively connected to the negative pole of the power supply of the charged device 51 and the anode of the first diode D1. It can be seen that when the charging control switch 52 is turned on, the charging circuit formed by the active and passive balancing control circuit, the charging control switch 52, and the external charging power supply Bat is turned on, and the inductor L in the active and passive balancing control circuit charges the external charging power supply Bat to achieve active balancing. When the charging control switch 52 is turned off, the charging circuit formed by the active and passive balancing control circuit, the charging control switch 52, and the external charging power supply Bat is disconnected, and the active and passive balancing control circuit is connected to the load circuit 6 to achieve passive balancing. Active balancing and passive balancing can be selected by turning on and off the charging control switch 52. Thereby, active and passive balancing switching is achieved, and balancing has no overvoltage safety risk.

[0065] In a preferred embodiment of the present invention, the load circuit 6 includes a fifth resistor R5, one end of the fifth resistor R5 is connected to the anode of the first diode D1, the other end is connected to the positive electrode of the Zener diode ZD, and the negative electrode of the Zener diode ZD is connected to the cathode of the second diode D2.

[0066] Specifically, in this embodiment, when discharging through the load circuit 6, by setting the Zener diode ZD, when the discharge voltage is lower than the reverse breakdown voltage of the Zener diode ZD, the load circuit 6 is not turned on, achieving automatic passive balancing stop and avoiding unlimited discharge.

[0067] In a preferred embodiment of the present invention, one end of the fifth resistor R5 is connected to the anode of the first diode D1 through the third diode D3, and the anode of the third diode D3 is connected to one end of the fifth resistor R5.

[0068] The present invention also provides a battery management system, such as Fig. 9 As shown, including:

[0069] A battery management chip 100 is provided with a plurality of pin groups corresponding to each battery cell 21 in the battery module 2, and a passive balancing switch 3 is provided between two pins in each pin group;

[0070] The above-mentioned inductive active and passive balancing circuit is disposed between each single battery 21 and the corresponding pin group.

[0071] The above description is only a preferred embodiment of the present invention, and does not limit the implementation mode and protection scope of the present invention. For those skilled in the art, it should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the contents of this specification and illustrations should be included in the protection scope of the present invention.

Claims

1. An inductive active and passive balancing circuit, characterized in that: include: An inductor, wherein a first end of the inductor is respectively connected to a positive electrode of a single battery in the battery module and one end of a passive balancing switch corresponding to the single battery through a first switching device, and a second end of the inductor is respectively connected to a negative electrode of the single battery and the other end of the passive balancing switch through a second switching device; The inductor is also connected in parallel with a charging circuit and a load circuit; When the passive balancing switch is turned on, the first switch device and the second switch device are turned on, and the single battery charges the inductor. When the passive balancing switch is turned off, the first switch device and the second switch device are turned off, and the inductor can be selectively discharged through the charging circuit to achieve active balancing or discharged through the load circuit to achieve passive balancing.

2. The inductive active and passive balancing circuit according to claim 1, characterized in that: The first switch device is a P-type transistor, the emitter of the P-type transistor is connected to the positive electrode of the single battery and one end of the passive balancing switch, the collector is connected to the first end of the inductor, and the base is connected to one end of the passive balancing switch; The second switch device is an N-type transistor, the emitter of which is connected to the negative electrode of the single battery and the other end of the passive balancing switch, the collector is connected to the second end of the inductor, and the base is connected to the other end of the passive balancing switch.

3. The inductive active and passive balancing circuit according to claim 2, characterized in that: The emitter of the P-type transistor is connected to one end of the passive balancing switch via a first resistor, and / or the emitter of the N-type transistor is connected to the other end of the passive balancing switch via a second resistor.

4. The inductive active and passive balancing circuit according to claim 2, characterized in that: The base of the P-type transistor is connected to one end of the passive balancing switch via a third resistor or a first capacitor; and / or The emitter of the N-type transistor is connected to the other end of the passive balancing switch via a fourth resistor or a second capacitor.

5. The inductive active and passive balancing circuit according to claim 1, characterized in that: The charging circuit includes a charged device and a charging control switch connected in series. When the charging control switch is turned on, the inductor discharges through the charging circuit to achieve active balancing. When the charging control switch is turned off, the inductor discharges through the load circuit to achieve passive balancing.

6. The inductive active and passive balancing circuit according to claim 5, characterized in that: The negative electrode of the power supply of the charged device is connected to the anode of the first diode, the cathode of the first diode is connected to the first end of the inductor, the positive electrode of the power supply of the charged device is connected to the cathode of the second diode, and the anode of the second diode is connected to the second end of the inductor; The two ends of the charging control switch are respectively connected to the negative electrode of the power supply of the charged device and the anode of the first diode; Or two ends of the charging control switch are respectively connected to the positive pole of the power supply of the charged device and the cathode of the second diode.

7. The inductive active and passive balancing circuit according to claim 5, characterized in that: The charged device is the battery module or an external charging power source.

8. The inductive active and passive balancing circuit according to claim 6, characterized in that: The load loop includes a fifth resistor, one end of the fifth resistor is connected to the anode of the first diode, the other end of the fifth resistor is connected to the positive electrode of the voltage regulator diode, and the negative electrode of the voltage regulator diode is connected to the cathode of the second diode.

9. The inductive active and passive balancing circuit according to claim 8, characterized in that: One end of the fifth resistor is connected to the anode of the first diode through a third diode, and the anode of the third diode is connected to one end of the fifth resistor.

10. A battery management system, characterized in that: include: A battery management chip, wherein the battery management chip is provided with a plurality of pin groups corresponding to each single battery in the battery module, and the passive balancing switch is provided between two pins in each pin group; An inductive active and passive balancing circuit as described in any one of claims 1 to 9 is provided between each of the single batteries and the corresponding pin group.

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