BMS communication circuit based on daisy chain

Abstract

The utility model discloses a BMS communication circuit based on a daisy chain. Comprising a communication switching module and a plurality of AFE chips U1. The communication switching module is connected with the MCU, and an IP end and an IM end of the communication switching module are connected with a network transformer L4 together; the SCK end, the CSB end, the IPB end and the IMB end of the AFE chip U1 are connected with a network transformer L1 together. The adjacent AFE chips U1 are mutually connected and communicated through the network transformer L1, and the network transformer L1 of the first AFE chip U1 is in communication connection with the network transformer L4; impedance matching modules are respectively arranged between the SCK end and the CSB end of the AFE chip U1 and between the IPB end and the IMB end of the AFE chip U1. According to the utility model, the communication between a plurality of AFE chips and the MCU can be realized, and the circuit has the advantages of strong flexibility and high stability.

Description

TECHNICAL FIELD

[0001] The utility model relates to BMS communication technical field, concretely is a kind of BMS communication circuit based on daisy chain. BACKGROUND

[0002] BMS (Battery Management System) is battery management system, for monitoring the state of battery, prevent battery from overcharge and overdischarge, to prolong the service life of battery.BMS cannot do without communication, in BMS communication application, existing communication type mainly takes CAN bus as main, CAN bus topology is often used between main control and numerous slave devices, one reason is that CAN bus application range is wide, technology is relatively mature and reliable, and it is relatively easy to realize technology, another reason is that interface is less and line is simple, it is very convenient for field construction installation.Therefore, CAN communication is the first choice of most BMS manufacturers.However, CAN bus also has its shortcomings, first of all, its bus utilization rate is low, before each main control and slave device communication, it must broadcast addressing, then one-to-one communication, when network node number is more, this repeated addressing and one-to-one communication is cumbersome, a large number of data on bus need to be filtered, bus resource is occupied, and bus utilization rate is reduced.Secondly, slave quantity expansion is more difficult, when using field increases a slave device, it needs to increase a group of bus, invisibly, bus length is lengthened, although it does not exceed bus effective length, but the part of bus lengthened increases the uncertainty of interference, and, if the bus node of a slave device appears short-circuit fault, it will lead to the communication paralysis of entire bus network, and it is also unable to find fault point in one step, and only can check one by one.Thirdly, there is certain limitation to slave device quantity, although theoretically, bus node number can be more than 250, but in actual application, it will be found that bus is influenced by various factors, the more node number, the more obvious signal distortion, the worse communication quality, and node number too much leads to the decline of bus utilization rate, and also brings data packet loss, communication delay and disconnection etc.unpredictable fault.Communication bandwidth of CAN bus is also influenced by bus length and node number, in actual application, if bus is longer, and device is more, often need to reduce baud rate to realize communication reliability.

[0003] If the daisy chain communication is used, the number of nodes can not be controlled and can be expanded according to the requirement. The data is transmitted from the previous node to the next node, each node is independently driven to output, and the signal weakening phenomenon does not exist in a long distance, since the communication is always between two nodes, the abnormality of a single node does not affect the communication quality of the previous level, the communication fault positioning and searching are convenient, and in the field construction and installation, only the communication ports of the front and rear two devices are connected. In the BMS system, communication isolation is also a necessary requirement, and the daisy chain communication can realize the electrical isolation more easily, and if the electrical isolation of each node fails, the damage point only occurs at the node position and does not affect other nodes. Content of the utility model

[0004] The utility model discloses a kind of BMS communication circuits based on daisy chain, which can realize the communication between multiple AFE chips and MCU, with the advantages of strong flexibility and high stability.

[0005] The technical scheme of the utility model discloses a kind of BMS communication circuits based on daisy chain, for connecting MCU to communicate;Including communication switching module and multiple AFE chips U1;The communication switching module is connected with MCU, and network transformer L4 is connected with the IP end and the IM end of communication switching module;The SCK end, CSB end, IPB end and IMB end of the AFE chip U1 are connected with network transformer L1;Adjacent AFE chip U1 is connected with each other by network transformer L1 and communicates, and the network transformer L1 of first AFE chip U1 is connected with network transformer L4 and communicates;Impedance matching module is respectively arranged between the SCK end and the CSB end of the AFE chip U1 and between the IPB end and the IMB end.

[0006] The above-mentioned BMS communication circuit based on daisy chain, the impedance matching module includes resistance R3, resistance R4, capacitor C3, capacitor C4 and capacitor C6;One end of the resistance R3 is connected with one end of capacitor C4, AFE chip U1 and network transformer L1;The other end of the resistance R3 is connected with one end of resistance R4, one end of capacitor C3, the other end of capacitor C4 and the other end of capacitor C6;The other end of capacitor C6 is grounded;The other end of the resistance R4 is connected with the other end of capacitor C3, AFE chip U1 and network transformer L1.

[0007] The daisy chain-based BMS communication circuit, the communication switching module comprises a chip U3, a resistor R37, a resistor R54, a resistor R56, a capacitor C15 and a network transformer L4;The EN pin of the chip U3 is connected with one end of the capacitor C15 and grounded;The VDDS pin of the chip U3 is connected with the other end of the capacitor C15 and one end of the resistor R37, and is connected with a voltage source;The MISO pin of the chip U3 is connected with the other end of the resistor R37 and MCU;The IBIAS pin of the chip U3 is connected with one end of the resistor R54;The other end of the resistor R54 is connected with one end of the resistor R56 and the ICMP pin of the chip U3;The other end of the resistor R56 is grounded;The GND pin of the chip U3 is connected with the SLOW pin of the chip U3 and grounded;The IM pin of the chip U3 and the IP pin of the chip U3 are connected with the network transformer L4.

[0008] The daisy chain-based BMS communication circuit, the type of the AFE chip U1 is ADBMS1818.

[0009] The daisy chain-based BMS communication circuit, the type of the chip U3 is LTC6820.

[0010] The daisy chain-based BMS communication circuit, the type of the network transformer L1 and the network transformer L4 is BT16B03.

[0011] Compared with the prior art, when the utility model is in use, the MCU and the AFE chip U1 communicate through the daisy chain, the signal is stable, the packet loss rate is low, the number of AFE chip U1 is reduced or the expansion operation is flexible;The signal transmission of the utility model is cut and distributed between every two AFE chips U1, and the signal strength is driven by each AFE chip U1 alone and can reach the maximum, thereby greatly reducing the risk of signal interference, the signal is not easy to distort, and the error rate is reduced. The impedance matching module can effectively reduce or eliminate the reflection of the signal in the transmission process, improve the stability and reliability of the signal;By reducing signal reflection and distortion, the transmission quality and efficiency of the signal can be improved, and system instability or failure caused by signal distortion and performance degradation can be avoided;The impedance matching module can also reduce the impact of reflected waves on equipment, reduce energy dissipation, and protect equipment from damage. In addition, the utility model is also relatively efficient and flexible in software implementation, whether it is verification in the development stage or stable testing after the finished product, it is easy to quickly locate and modify on the software code. The utility model can realize communication between multiple AFE chips and MCU, and has the advantages of high flexibility and stability. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is the circuit connection structure schematic diagram of the utility model;

[0013] Figure 2 is a circuit connection schematic diagram of the AFE chip U1;

[0014] Figure 3 is an internal principle schematic diagram of the AFE chip U1;

[0015] Figure 4 is a circuit schematic diagram of the communication switching module;

[0016] Figure 5 is an internal principle schematic diagram of the chip U3. DETAILED DESCRIPTION

[0017] The utility model will be further explained in connection with the drawings and examples, but not as the basis for limiting the utility model.

[0018] Example: BMS communication circuit based on daisy chain, structure like Figure 1 and Figure 2As shown, this is used for communication with an MCU; it includes a communication adapter module and multiple AFE chips U1; the communication adapter module is connected to the MCU, and its IP and IM terminals are connected to a network transformer L4; the SCK, CSB, IPB, and IMB terminals of each AFE chip U1 are connected to the network transformer L1; adjacent AFE chips U1 are interconnected via the network transformer L1, and the network transformer L1 of the first AFE chip U1 is communicatively connected to the network transformer L4; impedance matching modules are respectively provided between the SCK and CSB terminals and between the IPB and IMB terminals of each AFE chip U1. The network transformer L1 is a BT16B03 model. The network transformer L1 is used to couple differential communication signals, and also provides electrical isolation. The impedance matching modules can suppress noise interference. The impedance matching module includes resistors R3 and R4, capacitors C3, C4, and C6. One end of resistor R3 is connected to one end of capacitor C4, AFE chip U1, and network transformer L1. The other end of resistor R3 is connected to one end of resistor R4, one end of capacitor C3, the other end of capacitor C4, and the other end of capacitor C6. The other end of capacitor C6 is grounded. The other end of resistor R4 is connected to the other end of capacitor C3, AFE chip U1, and network transformer L1. The AFE chip U1 is model ADBMS1818. This chip has stable performance, is flexible in use, and can simultaneously acquire up to 18 battery voltages. It has a fast AD conversion rate and high accuracy. Additionally, this chip has multiple I / O interfaces, which can be programmed for analog input, digital input / output, etc. It has IIC and SPI communication interfaces, as well as an interface specifically designed for daisy-chain communication. In this embodiment, the communication strategy between the slave device AFE and the master MCU is implemented through this daisy-chain interface. In SPI communication, the SCK pin is the clock signal, and the CSB pin is used to select or activate a specific slave device for communication. When the CSB pin is pulled low (usually active low), the ADBMS1818 is selected as the current slave device for communication. In isoSPI communication, the SCK and CSB pins serve as the IPA and IPB pins, respectively. The IPB and IMB pins can be either differential signal inputs or outputs. Figure 3 As shown, the ADBMS1818 chip internally converts the SPI communication signal into a differential signal for output, and uses external voltage divider resistors to set the threshold voltage of the communication signal. Each ADBMS1818 acts as a node in a daisy chain, acting as an SPI communication slave when communicating with the previous node, and as an SPI master when communicating with the next node, identifying the data transmitted from the master MCU, responding, or transmitting to the next level.

[0019] The utility model discloses when using, the communication of MCU and AFE chip U1 is carried out through daisy chain, and signal is stable, and the packet loss rate is low, and AFE chip U1 quantity reduces or the expansion operation is flexible, the signal transmission of the utility model is cut and is distributed between every two AFE chip U1, and signal strength is driven individually by every AFE chip U1 and can reach maximum, thereby greatly reduce the risk of signal interference, and signal is not easy to distort, and the error rate reduces. Impedance matching module can effectively reduce or eliminate the reflection of signal in the transmission process, improve the stability and reliability of signal, through reducing signal reflection and distortion, can improve the transmission quality and efficiency of signal, can avoid the system instability or failure caused by signal distortion and performance decline, impedance matching module can also reduce the impact of reflected wave on equipment, reduce energy dissipation, protect equipment from damage. The utility model discloses on the software realization is also relatively efficient and flexible, whether it is the verification of development stage or the stable test after finished product, on the software code, it is easy to quickly locate and modify. The utility model can realize the communication between multiple AFE chips and MCU, has the advantages of high flexibility and stability.

[0020] The communication switching module is shown in Figure 4 The chip U3 is of LTC6820 type. The network transformer L4 is of BT16B03 type. One end of the EN pin of the chip U3 is connected with one end of the capacitor C15 and grounded. The VDDS pin of the chip U3 is connected with the other end of the capacitor C15 and one end of the resistor R37, and connected with a voltage source. The MISO pin of the chip U3 is connected with the other end of the resistor R37 and the MCU. The IBIAS pin of the chip U3 is connected with one end of the resistor R54. The other end of the resistor R54 is connected with one end of the resistor R56 and the ICMP pin of the chip U3. The other end of the resistor R56 is grounded. The GND pin of the chip U3 is connected with the SLOW pin of the chip U3 and grounded. The IM pin of the chip U3 is connected with the IP pin of the chip U3 and the network transformer L4. The IM pin of the chip U3 is the IM end of the communication switching module, and the IP pin of the chip U3 is the IP end of the communication switching module. In addition, the IP end and the IM end of the communication switching module are also connected with the impedance matching module. In the communication between the MCU master control end and the AFE slave control, the communication switching module is built by the LTC6820 chip, and communicates with the master MCU. The LTC6820 chip is a chip for converting SPI interface into differential signal, and is similar to the communication interface of the ADBMS1818 chip. It can realize electrical isolation and signal conversion, and the internal structure diagram is as shown in Figure 5The isoSPI isolation communication interface of the LTC6820 can provide a reliable isolation communication scheme and support a data transmission rate of 1Mbps. The communication between the master MCU and the LTC6820 uses the SPI interface inherent to the chip, and the other end of the communication interface of the LTC6820 is also coupled to the signal interface end of the master through the network transformer L4. The SPI communication mode between the master and the slave is realized, and the daisy chain communication structure is completed.

[0021] Each AFE slave device uses two RJ45 network interfaces for external communication, the RJ45 network interface is convenient to plug and stable and pressure-resistant, and the RJ45 is convenient to use in combination with the network transformer L1 and meets the SPI differential signal communication structure of the ABMS1818 chip. Figure 2 The CON1 and CON2 are two RJ45 interfaces, one RJ45 is connected to an AFE slave device or a master MCU, and the other RJ45 is connected to the next AFE slave device. All the RJ45s between the master and the slave are connected in series through a plurality of network lines, forming a series communication network similar to a daisy petal.

[0022] Principle: In use, the MCU communicates with the AFE chip U1 through a daisy chain, the signal is stable and the packet loss rate is low, the number of AFE chips U1 is reduced or expanded flexibly; the signal transmission of the utility model is cut and distributed between every two AFE chips U1, and the signal strength is driven by each AFE chip U1 individually to the maximum, thereby greatly reducing the risk of signal interference, the signal is not easy to distort, and the error rate is reduced. The impedance matching module can effectively reduce or eliminate signal reflection in the transmission process, improve the stability and reliability of the signal; by reducing signal reflection and distortion, the transmission quality and efficiency of the signal can be improved, and system instability or failure caused by signal distortion and performance degradation can be avoided; the impedance matching module can also reduce the impact of reflected waves on the equipment, reduce energy dissipation, and protect the equipment from damage. In addition, the utility model is relatively efficient and flexible in software implementation, whether it is verification in the development stage or stable testing after the finished product, it is easy to quickly locate and modify on the software code. The utility model can realize communication between multiple AFE chips and MCUs, and has the advantages of high flexibility and stability.

[0023] The above embodiment only expresses the implementation mode of the utility model, and the description is relatively specific and detailed, but cannot be understood as the limitation of the utility model patent range, and in the embodiment, up, down, left, right, front and back only represent relative positions and do not represent absolute positions. It should be pointed out that for ordinary skilled persons in the art, without departing from the concept of the utility model, a number of modifications and improvements can be made, which belong to the protection range of the utility model. Therefore, the protection range of the utility model patent should be subject to the appended claims.

Claims

1. A daisy chain based BMS communication circuit for connecting MCUs for communication; characterized in that: The communication switching module is connected with the MCU, and an IP end and an IM end of the communication switching module are connected with a network transformer L4; an SCK end, a CSB end, an IPB end and an IMB end of the AFE chip U1 are connected with a network transformer L1; adjacent AFE chips U1 are connected with each other in communication through the network transformer L1, and the network transformer L1 of the first AFE chip U1 is connected in communication with the network transformer L4; and impedance matching modules are arranged between the SCK end and the CSB end and between the IPB end and the IMB end of the AFE chip U1. The impedance matching module comprises a resistor R3, a resistor R4, a capacitor C3, a capacitor C4 and a capacitor C6; one end of the resistor R3 is connected with one end of the capacitor C4, the AFE chip U1 and the network transformer L1; the other end of the resistor R3 is connected with one end of the resistor R4, one end of the capacitor C3, the other end of the capacitor C4 and the other end of the capacitor C6; the other end of the capacitor C6 is grounded; and the other end of the resistor R4 is connected with the other end of the capacitor C3, the AFE chip U1 and the network transformer L1.

2. The daisy chain-based BMS communication circuit of claim 1, wherein: The communication switching module comprises a chip U3, a resistor R37, a resistor R54, a resistor R56, a capacitor C15 and a network transformer L4; an EN pin of the chip U3 is connected with one end of the capacitor C15 and grounded; a VDDS pin of the chip U3 is connected with the other end of the capacitor C15 and one end of the resistor R37 and connected with a voltage source; a MISO pin of the chip U3 is connected with the other end of the resistor R37 and the MCU; an IBIAS pin of the chip U3 is connected with one end of the resistor R54; the other end of the resistor R54 is connected with one end of the resistor R56 and an ICMP pin of the chip U3; the other end of the resistor R56 is grounded; a GND pin of the chip U3 is connected with a SLOW pin of the chip U3 and grounded; an IM pin of the chip U3 and an IP pin of the chip U3 are connected with the network transformer L4.

3. The daisy chain-based BMS communication circuit of claim 1, wherein: The AFE chip U1 is of a model ADBMS1818.

4. The daisy chain based BMS communication circuit of claim 1, wherein: The chip U3 is of a model LTC6820.

5. The daisy chain based BMS communication circuit of claim 3, wherein: The network transformer L1 and the network transformer L4 are both of a model BT16B03.

6. The daisy chain based BMS communication circuit of claim 1, wherein: ​

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