1.1 Automotive BMS
1、 Overview of the plan:
BMS, the full English name is Battery Management System, which refers to the Battery management system. BMS can be said to be the "battery manager" of new energy vehicles, which can monitor battery status in real-time, manage on-board power batteries, enhance battery efficiency, prevent overcharging and discharging of batteries, and improve battery life.
BMS is a vast collection of software and hardware, including sensors, central processing units, execution mechanisms, and more. BMS obtains the status information of the battery cells through sensors distributed throughout the battery pack, and transmits this status information to the central processing unit for processing. The feedback information is then processed and executed by the executing mechanism, adjusting the battery status to ensure it is in a suitable working and safe environment, meeting the vehicle's power needs.
2、 Recommended products for automotive BMS:
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Chip includes modules |
Brand |
Product and product overview |
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AFE module |
The main suppliers include ADI, TI, ST, Panasonic, NXP, and Reza. Among them, ADI's product line mainly comes from the acquired Lingleite and Meixin (in 2019, after acquiring Lingleite, ADI collaborated with vehicle companies such as General Motors to develop wireless BMS, launched wireless BMS systems and platforms, and tested battery data and analyzed it throughout the entire cycle from battery production to recycling to maximize the value of power batteries), while Ruisa's products mainly come from the acquired Intersil. The suppliers of AFE products are mainly foreign enterprises, and currently there is no domestic manufacturer providing AFE chips. |
AFE (Analog Front End) Front End (Front End) is an integrated component that realizes functions such as battery information acquisition, status monitoring, etc., including sensor interface, analog signal conditioning, including impedance conversion, programmable gain amplification, filtering and Umpolung) circuit, analog multiplexer switch, sample holder, ADC, data buffer, control logic and other parts of memory and control logic. Some AFEs also come with MCU, DAC, and various driver circuits. |
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Battery equalization module
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At present, the main suppliers include TI, ADI, ST, Reza, etc., most of which are American manufacturers. Although ST has, its product series is relatively small. In China, there are mainly Shanghai Beiling, Siripu, Shengbang Co., Ltd., and Xinhai Technology.
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The equalization circuit module improves battery life and cycle life, mainly including active equalization and passive equalization. Active balancing is the process of transferring the excess energy from the battery cell with the highest battery capacity to the battery cell with the lowest battery capacity, or to the entire battery string, to achieve energy recovery. Passive equalization is the process of dissipating the excess energy generated by the battery cell with the highest amount of electricity through resistance heating Consume.Unbalanced battery can affect battery life Flight time and battery cycle life. The imbalance of batteries is manifested by the unequal voltage of each battery when multiple batteries are connected in series, especially at the charging and discharging ends. When batteries with different fully charged capacities are connected in series, the charging current in series is the same, but the battery with a smaller fully charged capacity will first charge to a higher voltage, resulting in unequal voltage across each cell. Even if the full charge capacity is the same, when different battery configurations with different SOC are connected in series, the voltage of the battery with higher SOC is higher, resulting in the voltage of each battery being out of phase Etc. Even if the full charge capacity and SOC are the same, but the internal resistance R of each battery is different, the difference in IR pressure during charging and discharging will also lead to different battery terminal voltages. In addition, some external factors (such as local temperature of the battery pack or thermal imbalance between individual batteries) can also lead to different aging rates of individual batteries, resulting in uneven internal resistance. Ultimately, it may manifest as unequal voltage across each battery section. |
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Computing unit (MCU, etc.) |
Suppliers mainly include TI, ST, NXP, Infineon, Reza, etc. At present, many MCU manufacturers in China are actively deploying car size products, such as Zhongying Electronics, Zhaoyi Innovation, Ingenic Semiconductor, Xinhai Technology, National Technology, Ziguang Guowei, Nasda, Lexin Technology, Broadcom Integration, Fudan Microelectronics, Shanghai Beiling, Jingfeng Mingyuan, etc. |
The computing unit (MCU, etc.) implements control, calculation, and other functions. As a computing platform, MCU needs to meet certifications such as AEC-Q100 and IS026262. Taking the ADI48V hybrid BMS system as an example, the MCU plays a role in relay control, SOC/SOH estimation, balance control, cell voltage, current, temperature data collection, data storage, and other functions. Compared to consumer grade and industrial grade MCUs, the industry barrier for automotive grade MCUs is higher. Vehicle grade semiconductors have relatively high requirements for product reliability, consistency, safety, stability, and long-term effectiveness High research and development difficulty: The external temperature difference during car driving is relatively large, which has high requirements for the wide temperature control performance of the chip; In terms of product life, the design life of the whole vehicle is usually 15 years or more, which is far higher than the life demand of Consumer electronics; In terms of Failure rate, the vehicle manufacturer's requirements for vehicle specification semiconductor are usually zero failure; In terms of safety, the high Functional safety standards of automotive electronics provide sufficient security for the mass production of electronic systems with increasing complexity. The supply cycle of automotive grade semiconductors needs to cover the entire lifecycle of the vehicle, and the supply needs to be reliable, consistent, and stable, which is crucial for enterprise supply chain routing and management High requirements have been put forward. |
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Isolation circuit |
In terms of digital isolation, it is mainly used for digital communication between high and low voltage, such as SPI communication between high voltage sampling and MCU on the BMS main control board, and SPI communication between sampling board AFE and MCU. The main suppliers include ADI, TI, Silicon Labs, etc. Of course, in addition to using digital isolators, optocouplers or transformer isolation schemes can also be used. |
The isolation circuit realizes Galvanic isolation between high and low voltage modules. The Technology roadmap includes optocoupler isolation and digital isolation. Isolation device is a safety device that can convert and output input signals to achieve Galvanic isolation at both input and output ends. Galvanic isolation can ensure the safety of signal transmission between strong current circuit and weak current circuit. If Galvanic isolation is not carried out, once a fault occurs, the current of strong current circuit will flow directly to weak current circuit, causing damage to circuit and equipment. In addition, Galvanic isolation removes the grounding loop between the two circuits, which can block the propagation of common mode, surge and other interference signals, making the electronic system more secure and reliable. Most equipment for signal transmission between high voltage (strong current) and low voltage (weak current Regulatory certification. Widely used in information and communication, power meters、Various fields such as industrial control and electric vehicles. |
3、 Representative BMS chips
（1） TI high-precision battery monitoring, balancing, and protector
The rapid development of automotive electrification is irreversible, and the BMS system has become the primary core issue. TI has made significant achievements in the field of electric vehicle BMS, and has successively released wired BMS and wireless BMS solutions that comply with ASILD standards, leading the industry.
BQ79614-Q1 Circuit Topology Map Source: TI
BQ79614-Q1 is a high-precision battery monitor, balancer, and protector that can be applied to hybrid and pure electric vehicle BMS modules. It can monitor the battery temperature in real-time, and can automatically pause and start operations to avoid overheating. The chip operates at a voltage of 12V and can operate at 128 μ Quickly perform high-precision voltage monitoring for 14 batteries within S.
The BQ79614-Q1 chip integrates a front-end filter and a post ADC low-pass filter internally. The front-end filter is designed to reduce costs by using a simple, low-voltage differential RC filter on the battery input circuit. The ADC low-pass filter is designed to monitor the filtered DC voltage and facilitate the calculation of the battery's charge state. The chip can be used for measuring external thermistors. BQ79614-Q1 can be connected to BQ7600 devices in communication or directly communicate with MCU through UART interface. In the event of abnormal communication lines, the MCU can communicate directly with the battery pack through an isolated differential daisy chain.
（2） STL9963E Battery Monitoring and Protection Chip
STMicroelectronics (ST) has led the semiconductor market for many years. Its chip applications span many fields, and it has also become a major supplier of automotive chips. In the automotive field, in order to meet the market and design needs, L9963E battery monitoring and protection chip was launched, aiming to solve the design problem of Battery management system faced by electric vehicles all over the world, including China. The new product adopts a unique architecture that can measure 4 to 14 series connected battery cells, and there is no delay in synchronizing sample signals. The test results show that although 31 L9963Es can be daisy-chained, the entire chain delay is still less than 4 seconds.
The voltage measurement accuracy of L9963E is very high, with a maximum error of ± 2mV. At the same time, it can also measure current and understand the actual capacity of each battery cell. In addition, the architecture of this product ensures that each battery cell has dedicated resources for processing the electrical data monitored by the chip, while similar products on the market usually share data processing resources between battery cells. By providing dedicated processing resources for each individual unit, we can provide synchronized readings and avoid delays caused by de synchronization. In the daisy chain network structure, the L9963E can also communicate through serial bus, with a bandwidth of 2.66Mbps, while the industry's bandwidth mostly hovers around 1Mbps. Therefore, reading and processing 434 battery cells takes 4 milliseconds to 16 milliseconds.
EVAL-L9963E-MCUAs
As electric vehicles become cheaper, cost constraints become increasingly important. Powerful but expensive chips will lose most of their appeal. What sets it apart is that the L9963E offers a wide range of features, but without increasing the bare chip size, it continues to maintain cost-effectiveness. In addition, traditional BMS chips require each battery cell to be connected in parallel with an external Zener diode. During the assembly process, the system cannot know which battery cell first contacts the connector, and this is always a random event. Therefore, the Zener diode on each battery cell needs to protect the battery management chip. The 19963E adopts a hot swappable and robust architecture, allowing engineers to eliminate these Zener diodes, simplifying the layout of printed circuit boards and reducing overall costs.
（3） AD112 battery monitor
According to the ADI official website, the first integrated high-voltage battery stack monitor was launched as early as 2008, and has been iteratively updated to the fourth generation. The fifth generation product is still in the research and development stage.
LTC6811-1 frame diagram source: ADI
LTC6811-1 is ADI's fourth generation BMS IC, which is a battery pack monitor that can detect voltage on up to 12 series batteries. The measurement accuracy is higher than STL9963, and the total measurement error is less than 1.2mV. It only takes 290 to complete 12 battery tests μ S. The LTC6811-1 can connect multiple batteries in series, so the chip can achieve real-time monitoring of battery status in high voltage battery strings. The chip also has an ISOSPI interface, which can achieve high-speed remote communication with devices. The LTC6811-1 can connect 12 sets of batteries through a daisy chain to achieve multi-channel communication, monitor battery status, and pause and start operations based on the current battery status. The chip uses an isolated power supply.
（4） Infineon multi-channel battery monitoring and balancing system 1C
Infineon's battery management IC includes two models, TLE9012DQU and TLE9015DQU, providing optimized solutions for battery monitoring and balancing. The new battery management IC can achieve higher measurement accuracy and excellent application robustness, provide system solutions for the battery topology of battery modules, modeless battery technology and battery chassis integration technology, and enable automotive Battery management system (BMS) solutions to meet the requirements of ASIL-D, the highest level of automotive Functional safety, and comply with IS026262 standard.
Infineon's IC products are suitable for industrial, consumer and automotive applications, such as mild hybrid electric vehicles (MHEV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV) and pure electric vehicles (BEV), as well as energy storage systems, Battery management system of two wheel and three wheel electric vehicles. The IC series products include TLE9012DQU and TLE9015DQU.
Among them, TLE9012DQU is a multi-channel battery monitoring and equalization system chip, which can conduct highly accurate voltage measurement to estimate the battery state of charge (SoC) and battery health (SoH), which is also a key requirement that all Battery management system must meet.
TLE9015DQU is a battery monitoring transceiver chip used to connect multiple TLE9012AQUs in lithium batteries in a daisy chain structure. Through two pairs of UART and iso UART interfaces, ring communication can be supported, reducing costs and improving system efficiency. By integrating a fault management unit, this module can also achieve bidirectional information flow.
