CN115173512B - Analog front-end circuit of battery management system and application method thereof - Google Patents

Analog front-end circuit of battery management system and application method thereof Download PDF

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Publication number
CN115173512B
CN115173512B CN202210802860.1A CN202210802860A CN115173512B CN 115173512 B CN115173512 B CN 115173512B CN 202210802860 A CN202210802860 A CN 202210802860A CN 115173512 B CN115173512 B CN 115173512B
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voltage
battery
signal
battery string
current
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CN115173512A (en
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张钰玫
钟昌斈
钟昌佑
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Beijing Shichangding Technology Co ltd
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Beijing Shichangding Technology Co ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/0013—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries acting upon several batteries simultaneously or sequentially
    • H02J7/0014—Circuits for equalisation of charge between batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M10/4257—Smart batteries, e.g. electronic circuits inside the housing of the cells or batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H01M10/441—Methods for charging or discharging for several batteries or cells simultaneously or sequentially
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/44—Methods for charging or discharging
    • H01M10/443—Methods for charging or discharging in response to temperature
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/00712—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters
    • H02J7/007182—Regulation of charging or discharging current or voltage the cycle being controlled or terminated in response to electric parameters in response to battery voltage
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/007—Regulation of charging or discharging current or voltage
    • H02J7/007188—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters
    • H02J7/007192—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters in response to temperature
    • H02J7/007194—Regulation of charging or discharging current or voltage the charge cycle being controlled or terminated in response to non-electric parameters in response to temperature of the battery
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4271—Battery management systems including electronic circuits, e.g. control of current or voltage to keep battery in healthy state, cell balancing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4278—Systems for data transfer from batteries, e.g. transfer of battery parameters to a controller, data transferred between battery controller and main controller
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Secondary Cells (AREA)

Abstract

The invention provides an analog front-end circuit of a battery management system and an application method thereof, relates to the technical field of integrated circuits, and solves the technical problem that the performance of the existing analog front-end circuit is poor. The analog front-end circuit is connected with the battery string and comprises a first data selector, a second data selector, a current acquisition unit, an SAR ADC, a Sigma-Delta ADC, a digital control logic unit, a charge-discharge unit, an operation metering unit and an equalization unit, the analog front-end circuit is integrated in the same chip and has higher consistency, the working state of the battery string is accurately determined by monitoring the current and the temperature of the connected battery string and the voltage of each battery in real time, the working state of the battery string is timely responded by setting two-stage monitoring alarm thresholds, and when the working voltage state of the battery string is abnormal, the voltage of each battery can be adjusted by an active equalization mode and/or a passive equalization mode.

Description

Analog front-end circuit of battery management system and application method thereof
Technical Field
The present application relates to the field of integrated circuits, and more particularly, to an analog front-end circuit of a battery management system and an application method thereof.
Background
The existing Battery management system (Battery MANAGEMENT SYSTEM, BMS) is composed of 5 modules such as Analog Front End (AFE), charge and discharge unit, temperature sensor, fuel gauge (coulometer) and micro control unit (Micro Controller Unit, MCU). For example, the values of the voltage, the current and the like of the battery are detected, the detected values are compared with preset alarm protection points, and finally the safety strategy of the battery is controlled by the MCU of the upper computer. When the number of battery strings is large, the MCU of the upper computer becomes a hierarchical processor, or else a high-performance processor is used. However, using a high performance processor in a BMS system may cause instability of the high performance processor due to voltage and current jitter, and there is a risk that an alarm response will not be timely if the MCU uses a hierarchical process.
Therefore, the prior art has the technical problem of poor performance of the analog front-end circuit.
Disclosure of Invention
The application aims to provide an analog front-end circuit of a battery management system and an application method thereof, so as to solve the technical problem of poor performance of the analog front-end circuit in the prior art.
In a first aspect, an embodiment of the present application provides an analog front-end circuit of a battery management system, where the analog front-end circuit is integrated in the same chip, and the analog front-end circuit is connected with a battery string; the analog front-end circuit includes:
The device comprises a first data selector, a second data selector, a current acquisition unit, a successive approximation analog-to-digital converter (Successive Approximation Register-Analog to Digital Converter, SAR ADC), a Sigma-Delta analog-to-digital converter (Sigma-Delta Analog to Digital Converter, sigma-Delta ADC), a digital control logic unit, a charging and discharging unit, an operation metering unit and an equalization unit;
the first data selector is connected with the SAR ADC, and is used for receiving a voltage signal of each battery in the battery string and sending the voltage signal to the SAR ADC;
The second data selector is connected with the Sigma-Delta ADC, and is used for receiving a temperature signal of the battery string and sending the temperature signal to the Sigma-Delta ADC; the current acquisition unit is connected with the Sigma-Delta ADC, and is used for acquiring a current signal of the battery string and sending the current signal to the Sigma-Delta ADC;
The digital control logic unit is respectively connected with the SAR ADC, the Sigma-Delta ADC, the operation metering unit and the charge-discharge unit, and the operation metering unit is respectively connected with the equalization unit and the charge-discharge unit; the SAR ADC is used for carrying out analog-to-digital conversion on the voltage signal and sending the voltage signal to the digital control logic unit; the Sigma-Delta ADC is used for carrying out analog-to-digital conversion on the temperature signal and the current signal and sending the temperature signal and the current signal to the digital control logic unit; the digital control logic unit and the operation metering unit are used for controlling the equalization unit and the charge and discharge unit;
the equalization unit is connected with the battery string and is used for carrying out active voltage equalization and passive voltage equalization on the battery string;
The charging and discharging unit is connected with an external power device and is used for adjusting the voltage of the battery string.
In a second aspect, an embodiment of the present application provides an application method of an analog front-end circuit of a battery management system, which is applied to the analog front-end circuit of the battery management system described in the first aspect, where the analog front-end circuit is connected with a battery string; comprising the following steps:
Collecting a voltage signal, a current signal and a temperature signal of the battery string;
comparing the voltage signal, the current signal and the temperature signal with the corresponding first-level detection threshold values respectively to obtain a first comparison result;
And if at least one of the voltage signal, the current signal and the temperature signal exceeds the corresponding primary detection threshold value as a result of the first comparison, sending a first alarm signal to the outside of the analog front-end circuit, wherein the first alarm signal comprises the voltage, the temperature and the current alarm indication state of each battery in the battery string.
In one possible implementation, the method further includes:
Collecting voltage signals of each battery in the battery string;
Judging whether the voltage signal of each battery exceeds a voltage primary detection threshold value or not;
And if the voltage signal of one battery in the battery string exceeds the voltage primary detection threshold, discharging the battery to realize passive voltage equalization of the battery string.
In one possible implementation, the method further includes:
Collecting a voltage signal, a current signal and a temperature signal of the battery string;
Comparing the voltage signal, the current signal and the temperature signal with the corresponding second-level detection threshold values respectively to obtain a second comparison result;
And if one or more of the voltage signal, the current signal and the temperature signal are lower than the corresponding second-level detection threshold value as a result of the second comparison, sending a second alarm signal to the outside of the analog front-end circuit, wherein the second alarm signal comprises the voltage, the temperature and the current alarm indication state of each battery in the battery string.
In one possible implementation, the method further includes:
Collecting voltage signals of each battery in the battery string;
judging whether the voltage signal of each battery is lower than a voltage secondary detection threshold value or not;
and if the voltage signal of one battery in the battery string is lower than the voltage secondary detection threshold, charging the battery to realize active voltage equalization of the battery string.
In one possible implementation, the method further includes:
collecting an output voltage value and an output current value of the battery string;
judging whether the output voltage value and the output current value accord with expected values or not;
And if the output voltage value and the output current value do not meet the expected value, adjusting the output duty ratio of the battery string so as to enable the output voltage value and the output current value to meet the expected value.
In one possible implementation, the method further includes:
acquiring temperature signals of the battery strings based on a preset acquisition frequency to obtain a plurality of groups of temperature signals;
determining a temperature change trend of the battery string based on the plurality of sets of temperature signals;
And determining a first working state of the battery string based on the temperature change trend.
In one possible implementation, the method further includes:
acquiring voltage signals of the battery strings based on a preset acquisition frequency to obtain a plurality of groups of voltage signals;
Determining a voltage variation trend of the battery string based on the plurality of sets of voltage signals;
and determining a second working state of the battery string based on the voltage change trend.
In one possible implementation, the method further includes:
collecting current signals of the battery strings based on preset collection frequency to obtain a plurality of groups of current signals;
And integrating the plurality of groups of current signals to determine the electric quantity information of the battery string.
In one possible implementation, the method further includes:
and dynamically adjusting the electric quantity information of the battery string based on the working state of the battery string.
The embodiment of the application has the following beneficial effects:
the embodiment of the application provides an analog front-end circuit of a battery management system and an application method thereof, wherein the analog front-end circuit is connected with a battery string, the analog front-end circuit comprises a first data selector, a second data selector, a current acquisition unit, an SAR ADC, a Sigma-Delta ADC, a digital control logic unit, a charging and discharging unit, an operation metering unit and an equalization unit, the analog front-end circuit is integrated in the same chip, has higher consistency, accurately determines the working state of the battery string by monitoring the current and the temperature of the connected battery string and the voltage of each battery in real time, ensures the timely response to the working state of the battery string by setting two-stage monitoring alarm thresholds, and can regulate the voltage of each battery in two ways of active equalization and passive equalization when the working voltage state of the battery string is abnormal. The scheme realizes multiple functions through the integrated circuit in one chip, and compared with the scheme of the whole system in the prior art, the scheme uses the device element relatively succinct; simplifying the power supply mode of the whole system; the peripheral circuit structure of the active equalization is the same as that of the passive equalization, and no extra pins are needed for the active equalization; the alarm response speed is faster than that of the prior art; the temperature rise rate can be detected; the pressure drop rate and pressure drop interval can be detected; the battery characteristic change and the battery aging phenomenon can be predicted; a power supply capable of supplying a large current to the BMS system board; the monitoring of the multipoint temperature is supported, and the monitoring chip and the battery are monitored; the method can respond to the information of the State-of-Charge (SoC) and the Health condition (SoH) of the battery in time, and the technical problem of poor performance of the analog front-end circuit in the prior art is solved.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present application, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of an analog front-end circuit of a battery management system according to an embodiment of the present application;
FIG. 2 is a schematic diagram of an analog front-end circuit of another battery management system according to an embodiment of the present application;
fig. 3 is a schematic structural diagram of a voltage detecting and equalizing circuit according to an embodiment of the present application;
Fig. 4 is a schematic diagram of another voltage detecting and equalizing circuit according to an embodiment of the present application.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The terms "comprising" and "having" and any variations thereof, as used in the embodiments of the present application, are intended to cover non-exclusive inclusion. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those listed but may optionally include other steps or elements not listed or inherent to such process, method, article, or apparatus.
The existing BMSAFE technology has the following problems: the alarm response is not timely, especially at the response speed of the secondary protection; the chip area is large, and the consistency is poor; high voltage devices are required for both equalizing and detecting voltage switching devices; active equalization of the existing BMS AFE technology requires 2 pins for each battery on the chip side; the temperature rise rate cannot be predicted; the voltage drop rate and the voltage drop interval cannot be detected; the device on the BMS system board cannot be supplied with power by a high-power supply; accurate electric quantity can not be obtained when the internal resistance of the battery changes; the calibration of the full temperature range of the analog circuit is based on pre-configured storage on-chip storage, but the method will have some differences between the analog parameter characteristics of the actual application environment and the pre-set parameters. Therefore, the prior art has the technical problem of poor performance of the analog front-end circuit.
Based on the above, the embodiment of the application provides an analog front-end circuit of a battery management system and an application method thereof, so as to relieve the technical problem of poor performance of the analog front-end circuit in the prior art or reduce the characteristics of high process and technical requirements.
The analog front-end circuit of the battery management system and the application method thereof provided by the embodiment of the application can be applied to but are not limited to the following scenes: the method can be applied to the scene of the electric bicycle; the method can be applied to energy storage scenes; can be applied to electric tools; the method can be applied to new energy automobiles;
Embodiments of the present application are further described below with reference to the accompanying drawings.
Fig. 1 is a schematic structural diagram of an analog front-end circuit of a battery management system according to an embodiment of the present application, wherein all the analog front-end circuits are integrated in the same chip, and the analog front-end circuit is connected to a battery string 101. As shown in fig. 1, the analog front-end circuit includes:
A first data selector 102, a second data selector 103, a current acquisition unit 104, a SAR ADC105, a Sigma-Delta ADC106, a digital control logic unit 107, a charge-discharge unit 108, an arithmetic metering unit 109, and an equalization unit 110;
The first data selector 102 is connected to the SAR ADC105, and the first data selector 102 is configured to receive a voltage signal of each battery in the battery string 101, and send the voltage signal to the SAR ADC105;
The second data selector 103 is connected to the Sigma-Delta ADC106, and the second data selector 103 is configured to receive the temperature signal of the battery string 101 and send the temperature signal to the Sigma-Delta ADC106; the current acquisition unit 104 is connected with the Sigma-Delta ADC106, and the current acquisition unit 104 is used for acquiring a current signal of the battery string 101 and sending the current signal to the Sigma-Delta ADC106;
The digital control logic unit 107 is respectively connected with the SAR ADC105, the Sigma-Delta ADC106, the operation metering unit 109 and the charge and discharge unit 108, and the operation metering unit 109 is respectively connected with the equalization unit 110 and the charge and discharge unit 108; the SAR ADC105 is configured to perform analog-to-digital conversion on the voltage signal and send the voltage signal to the digital control logic unit 107; the Sigma-Delta ADC106 is configured to perform analog-to-digital conversion on the temperature signal and the current signal, and send the temperature signal and the current signal to the digital control logic unit 107; the digital control logic unit 107 and the arithmetic metering unit 109 are used for controlling the equalization unit 110 and the charge/discharge unit 108;
the equalization unit 110 is connected with the battery string, and the equalization unit 110 is used for performing active voltage equalization and passive voltage equalization on the battery string;
The charge/discharge unit 108 is connected to an external power device, and the charge/discharge unit 108 is used for voltage adjustment of the battery string.
The circuit further comprises an equalization switch matrix 111 connected to the equalization unit 110, which is different from the prior art in that the negative electrode of the equalization switch of the embodiment of the present application is fixed to the ground terminal of the system, and the negative electrode of the equalization switch of the embodiment of the present application corresponds to the negative terminal of the battery to be equalized, that is, the negative terminal of the matrix switch is floating, which is to use the switching tube of low voltage for equalization.
The following describes an analog front-end circuit of a battery management system and an application method thereof in detail.
Fig. 2 is a schematic structural diagram of an analog front end circuit of another battery management system according to an embodiment of the present application, and as shown in fig. 2, the main function of the analog front end AFE is to equalize the current of each battery, collect the voltage and current of each battery, and the temperature of a specific point of a battery string. The equalization in the embodiment of the application supports active equalization and passive equalization, and the shared pins for active equalization and passive equalization do not need extra pins to support active equalization in the prior art. The acquisition of the battery voltage uses multiple SAR ADCs (through voltage detection switches C0-Cn), so that the information of each battery voltage can be obtained as soon as possible, and if the Sigma-Delta ADC is used for acquiring the battery voltage, the time required for obtaining all the battery voltages is tens of times longer than that required for using the SAR ADC, and a certain risk exists in judging the battery state. The temperature and current acquisition uses a Sigma-Delta ADC because both parts require higher accuracy than voltage and the current and temperature change unlike voltage, so the application uses a Sigma-Delta ADC in the current and temperature acquisition embodiment.
The switches used in the embodiment of the application are switches using low-voltage devices, and a differential mode is adopted without using high-voltage devices, so that the chip area can be saved, and the implementation difficulty of the ADC under the working of wide voltage and full temperature range can be reduced. The AFE has a corresponding circuit for each battery, and the method directly detects whether the battery is over-heated, over-voltage or over-current by simulating a preset threshold value. The AFE needs to balance which battery, need to detect which battery, or poll to detect battery strings all are done by the digital control logic unit. The numerical values of the SAR ADC and the Sigma-Delta ADC in the AFE are output to a digital control logic unit, the digital control logic unit judges the state of each battery, and if any battery has overvoltage, overtemperature or overcurrent, the digital circuit can generate an alarm signal and output the alarm signal to a pin to be processed by an upper computer; in addition, the digital control logic unit of the embodiment of the application can judge whether the behavior is abnormal or caused by transient load pulse according to the value and the speed of voltage and temperature change.
The embodiment of the application also provides a negative temperature coefficient thermistor (NTC Thermistor) externally connected with at least 4 paths, which can monitor the temperature of the chip of the embodiment of the application and the temperature of as many single batteries as possible. The temperature sensor adopts a Sigma-Delta ADC mode, and is internally matched with a chopper and current minor circuit, so that the mismatch phenomenon caused by different temperatures and voltages of an external circuit and a chip internal circuit can be eliminated greatly, and the accuracy of current and temperature acquisition is improved. The highest bits of the current and temperature values collected by Sigma-Delta represent signs. The 0 when measuring temperature represents positive temperature, and the direction when measuring current is from high potential to ground; the temperature 1 is a negative temperature, and the current is a high potential from the ground. The value of the Sigma-Delta ADC is output to the digital control logic unit, the digital control logic unit judges whether the temperature is over-high or not according to a preset threshold value, and meanwhile, the state is output to a ALERTN pin to inform an upper computer.
The electricity meter of the embodiment of the application is realized by using a Sigma-Delta ADC to fixedly collect current (one time of current, ten times of current and bias current) every second, and then accumulating (or integrating) the collected current to obtain the current electricity information of the battery. The digital control logic unit starts, stops and loads the value that will affect the accuracy of the power into the counter of the power meter.
The charging and discharging unit of the embodiment of the application can be used for charging and discharging the battery, but considering the situation of safety protection in practical application, the functional module is limited in that the embodiment of the application can provide a plurality of groups of digital DCDC power supply outputs with different voltages and currents for the whole system scheme of the BMS. This can greatly reduce the power module devices at the system board level and simplify the circuit design of the power module. In order to form a closed-loop control system, fig. 2 shows that the 4-way digital DCDC is provided in the embodiment of the present application, and whether the output voltage and current of the 4-way digital DCDC meet the expectations is obtained through the 4-way inputs of AIN0 to AIN3 of the first data selector. And if the output duty ratio does not meet the expectations, the output duty ratio of the digital DCDC is controlled according to the actual measured value to achieve the purpose of boosting or reducing.
The digital control logic unit is the whole core of the embodiment of the application, and the front-end analog circuit provided by the embodiment of the application comprises functions of warehouse management, power-up, first-stage detection alarm threshold setting (comprising voltage, current and temperature), balanced switch control, voltage detection channel switch control, fuel gauge, temperature and current channel distribution, second-stage detection alarm threshold setting, ALERTN alarm mode setting One-Shot and continuous mode, temperature rising rate calculation, voltage drop interval calculation and the like.
For warehouse management functions, the embodiment of the application provides a SHIP pin (thyristor for controlling the negative connection of the battery string in fig. 2), which pin is pulled down during transportation or when the battery string is not installed in the system, so that the whole battery string does not form a current path, that is, the battery string is dead to the ground and the current path, and the mechanism is mainly to confirm that the battery string ensures the safety of the battery as much as possible under the condition of not being used.
For the power-on function, the power supply of the embodiment of the application is the voltage required to drop from the highest voltage of the battery string to the inside of the chip via the internal power module. This power supply module is implemented in two ways, buck-no-inductance DCDC and Charge Pump (Charge Pump). Both of these approaches are to reduce current loss from a high voltage battery string down to a low voltage.
For the first-stage detection threshold setting, the embodiment of the application provides an analog circuit for directly comparing and outputting alarm signals, and the time from event occurrence to alarm response is ensured to be within 1us, so that the system safety is greatly improved. The simulated alarm threshold is determined by the first level detection threshold setting.
For the equalization switch control function, the equalization switch in the embodiment of the application determines which battery needs to be equalized according to the value obtained from the ADC by the digital control logic unit. The embodiment of the application provides passive equalization and active equalization. The passive equalization is that the digital control logic unit judges that one or more batteries are too high through the reading value of the ADC, and the digital control logic unit opens the corresponding equalization switch to enable the battery with too high voltage to achieve the discharging purpose. The active equalization is to provide a constant current source inside the chip, and the digital control logic unit judges that the voltage of one battery or a plurality of batteries in the battery string is lower through the reading value of the ADC, so that the digital control logic unit can open the corresponding equalization switch to charge the battery with relatively low voltage.
For the function of the voltage detection switch (C0-Cn), the voltage detection switch of the embodiment of the application can be related to the switching of the conversion channel of the SAR ADC. The embodiment of the application provides a software mode and a hardware automatic mode. The software mode is to switch the voltage detection switch and then open the corresponding ADC channel, and then read the reading value of the ADC, so as to achieve the purpose of detecting the voltage of each battery. The hardware automatic mode, namely, the software configures the number of channels required to be converted by the ADC, and then enables the SAR ADC, wherein the SAR ADC can convert values according to the ADC channels set by the digital control logic unit, the values can be stored in a register corresponding to each channel, and the voltage of a corresponding battery can be obtained only by reading the ADC value of each channel by the numerical control circuit.
For the function of the fuel gauge, the digital control logic unit of the embodiment of the application can dynamically adjust the parameters of the fuel gauge according to the measured changes of the internal resistance, the temperature and the voltage of the battery, and can start, stop and load the initial default parameters of the fuel gauge at any time. That is, the digital control logic unit may dynamically adjust the counter parameters and counts of the fuel gauge based on actual voltage, temperature, and internal resistance changes of the battery.
For the temperature and current channel distribution function, since the temperature and current detection share the Sigma-Delta ADC, the digital control logic unit provides the alarm threshold value for selecting whether the detection channel is current or temperature because the characteristics of the temperature and the current are different, so that the second-stage protection can be correspondingly adjusted.
For the second-stage detection alarm threshold setting function, the alarm detected by the second stage is judged by the conversion value of the ADC, and the digital control logic unit can set upper and lower limits on the temperature, the current and the voltage of each battery. The upper limit is that the temperature, current and voltage of the battery exceed the set upper limit and a ALERTN alarm of overflow will be generated. An underflow ALERTN alarm will be generated when the temperature, current and voltage of the battery are below the set lower limit.
For ALERTN alarm mode setting functions, the digital control logic unit implements two methods-One-Shot and continuous mode. The One-Shot mode is that the temperature, current and voltage of the battery will be valid at the position ALERTN until the corresponding status register is cleared by the digital control logic unit to deactivate ALERTN as long as a battery exceeds the upper limit or falls below the lower limit, and the state ALERTN remains valid or invalid as determined by the current battery state. When one of the conditions of over-temperature, over-pressure, over-current, low-temperature, low-pressure, under-current and the like occurs in the continuous mode, the ALERTN alarm signal in the continuous mode can be withdrawn after exceeding the lower limit of overflow and the upper limit threshold of underflow; for example, ALERTN will be set to be active when an over-temperature condition occurs, and will be active when the temperature is not below the previously preset overflow temperature lower threshold, until the temperature is below the threshold, the signal will be deactivated, as will the over-voltage and over-current determination mechanisms. If the detected temperature is lower than the preset low temperature alarm, the signal is set to be valid in a continuous mode until the temperature rises to the preset lower temperature upper limit; that is, the ALERTN alarms in continuous mode have hysteresis mechanisms to ensure that ALERTN alarms are deactivated after the over-temperature, over-pressure, over-current and low-temperature, low-pressure and under-current are below or above a preset threshold. ALERTN alarm pins are in an open-drain mode and can be better adapted to different voltages of the upper computer.
For the function of calculating the temperature rising rate, the digital control logic unit can compare the numerical value obtained by the ADC with the numerical values obtained before and after several times so as to obtain the rising or falling trend of the temperature of the battery string, and the upper computer can better judge the current use state of the battery string.
For the function of calculating the voltage drop rate and the voltage drop interval, the digital control logic unit can compare the value obtained by the ADC with the values obtained before and after several times so as to obtain the voltage drop rate and the voltage drop interval of the battery string, and therefore the upper computer can better judge the current use state of the battery string.
Fig. 3 is a schematic diagram of a voltage detection and equalization circuit according to an embodiment of the present application, corresponding to active equalization SW0-SWn is an equalization switch, corresponding to C0-Cn is a voltage detection switch, where ADC represents both SAR ADC and Sigma-Delta ADC. As shown in fig. 3, the voltage detecting and equalizing circuit according to the embodiment of the present application is a part of an analog front-end circuit of a battery management system shown in fig. 2, and includes a constant current source 301, where the constant current source 301 operates to supply power when active equalization is required, and does not operate when passive equalization is required. When the voltages of the batteries B2, B3 and B4 in the battery string are too low and active equalization is required, the active equalization circuit is shown as a dotted line box 302, and the corresponding switches are closed to charge the batteries B2, B3 and B4, so as to realize voltage equalization.
Fig. 4 is a schematic diagram of another voltage detection and equalization circuit according to an embodiment of the present application, corresponding to passive equalization, SW0-SWn are equalization switches, and C0-Cn are voltage detection switches, where ADC represents both SAR ADC and Sigma-Delta ADC. As shown in fig. 4, when the voltage of the battery B5 is too high and passive equalization is required, the voltage of the battery B5 can be released by using the resistors connected in series with the equalization switches through the corresponding switches, so that an equalization state is achieved. Line segment 401 and line segment 402 are passive equalization paths, and when the passive equalization is applied to a scene, the SWP and SWN are internally shorted to form a loop, so that the battery can achieve the effect of discharging.
In summary, the embodiments of the present application solve the following problems: the alarm response speed is increased, the first-stage alarm response is within 1uSec, and the second-stage alarm response is within 20uSec at the fastest; the BMS AFE intelligence is increased, and meanwhile, the total area of the chip is reduced; the voltage detection and equalization switch adopts a differential mode, and a high-voltage device is not needed; the equalization technology of the embodiment of the application does not need extra pins at the chip side, and the pins are the same as the voltage detection pins, so that the layout and wiring of the BMS board level system can be simplified; the paths of the equalization and the voltage detection are the same as those of the ADC using the detection, so that the voltage detection and the equalization measurement value are inconsistent due to the difference of path and device matching; the self-adaptive digital controller is added, so that the temperature rise rate, the pressure drop rate and the pressure drop interval can be detected intelligently; the embodiment of the application is embedded with a plurality of paths of digital DCDC, so that the power supply scheme of the BMS system is reduced; according to the embodiment of the application, the self-adaptive digital controller is added, so that the calculation of the fuel gauge can be dynamically adjusted according to the internal resistance of the battery cell due to the temperature change; the embodiment of the application can dynamically adjust the simulation parameters in a full temperature range (-40 DEG to 125 ℃); the embedded non-inductance BUCK circuit provided by the embodiment of the application supplies power to the chip, and the board level does not need additional DCDC or LDO.
It will be appreciated by those skilled in the art that in the above-described method of the specific embodiments, the written order of steps is not meant to imply a strict order of execution but rather should be construed according to the function and possibly inherent logic of the steps.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described system and apparatus may refer to corresponding procedures in the foregoing method embodiments, which are not described herein again. In the several embodiments provided in the present disclosure, it should be understood that the disclosed systems, devices, and methods may be implemented in other manners. The above-described apparatus embodiments are merely illustrative, for example, the division of the units is merely a logical function division, and there may be other manners of division in actual implementation, and for example, multiple units or components may be combined or integrated into another system, or some features may be omitted, or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be through some communication interface, device or unit indirect coupling or communication connection, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional unit in each embodiment of the present disclosure may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a non-volatile computer readable storage medium executable by a processor. Based on such understanding, the technical solution of the present disclosure may be embodied in essence or a part contributing to the prior art or a part of the technical solution, or in the form of a software product stored in a storage medium, including several instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in the embodiments of the present disclosure. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (Random Access Memory, RAM), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
Finally, it should be noted that: the foregoing examples are merely specific embodiments of the present disclosure, and are not intended to limit the scope of the disclosure, but the present disclosure is not limited thereto, and those skilled in the art will appreciate that while the foregoing examples are described in detail, it is not limited to the disclosure: any person skilled in the art, within the technical scope of the disclosure of the present disclosure, may modify or easily conceive changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features thereof; such modifications, changes or substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the disclosure, and are intended to be included within the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims (10)

1. An analog front-end circuit of a battery management system is characterized in that the analog front-end circuit is integrated in the same chip, and the analog front-end circuit is connected with a battery string; the analog front-end circuit includes:
The system comprises a first data selector, a second data selector, a current acquisition unit, an SAR ADC, a Sigma-Delta ADC, a digital control logic unit, a charge-discharge unit, an operation metering unit and an equalization unit;
the first data selector is connected with the SAR ADC, and is used for receiving a voltage signal of each battery in the battery string and sending the voltage signal to the SAR ADC;
The second data selector is connected with the Sigma-Delta ADC, and is used for receiving a temperature signal of the battery string and sending the temperature signal to the Sigma-Delta ADC; the current acquisition unit is connected with the Sigma-Delta ADC, and is used for acquiring a current signal of the battery string and sending the current signal to the Sigma-Delta ADC;
The digital control logic unit is respectively connected with the SAR ADC, the Sigma-Delta ADC, the operation metering unit and the charge-discharge unit, and the operation metering unit is respectively connected with the equalization unit and the charge-discharge unit; the SAR ADC is used for carrying out analog-to-digital conversion on the voltage signal and sending the voltage signal to the digital control logic unit; the Sigma-Delta ADC is used for carrying out analog-to-digital conversion on the temperature signal and the current signal and sending the temperature signal and the current signal to the digital control logic unit; the digital control logic unit and the operation metering unit are used for controlling the equalization unit and the charge and discharge unit;
The equalization unit is connected with the battery string and is used for carrying out active voltage equalization and/or passive voltage equalization on the battery string;
The charging and discharging unit is connected with an external power device and is used for adjusting the voltage of the battery string.
2. An application method of an analog front-end circuit of a battery management system, which is characterized in that the application method is applied to the analog front-end circuit of the battery management system as set forth in the above claim 1, and the analog front-end circuit is connected with a battery string; comprising the following steps:
Collecting a voltage signal, a current signal and a temperature signal of the battery string;
comparing the voltage signal, the current signal and the temperature signal with the corresponding first-level detection threshold values respectively to obtain a first comparison result;
And if at least one of the voltage signal, the current signal and the temperature signal exceeds the corresponding primary detection threshold value as a result of the first comparison, sending a first alarm signal to the outside of the analog front-end circuit, wherein the first alarm signal comprises the voltage, the temperature and the current alarm indication state of each battery in the battery string.
3. The method as recited in claim 2, further comprising:
Collecting voltage signals of each battery in the battery string;
Judging whether the voltage signal of each battery exceeds a voltage primary detection threshold value or not;
And if the voltage signal of one battery in the battery string exceeds the voltage primary detection threshold, discharging the battery to realize passive voltage equalization of the battery string.
4. The method as recited in claim 2, further comprising:
Collecting a voltage signal, a current signal and a temperature signal of the battery string;
Comparing the voltage signal, the current signal and the temperature signal with the corresponding second-level detection threshold values respectively to obtain a second comparison result;
And if one or more of the voltage signal, the current signal and the temperature signal are lower than the corresponding second-level detection threshold value as a result of the second comparison, sending a second alarm signal to the outside of the analog front-end circuit, wherein the second alarm signal comprises the voltage, the temperature and the current alarm indication state of each battery in the battery string.
5. The method as recited in claim 4, further comprising:
Collecting voltage signals of each battery in the battery string;
judging whether the voltage signal of each battery is lower than a voltage secondary detection threshold value or not;
and if the voltage signal of one battery in the battery string is lower than the voltage secondary detection threshold, charging the battery to realize active voltage equalization of the battery string.
6. The method as recited in claim 2, further comprising:
collecting an output voltage value and an output current value of the battery string;
judging whether the output voltage value and the output current value accord with expected values or not;
And if the output voltage value and the output current value do not meet the expected value, adjusting the output duty ratio of the battery string so as to enable the output voltage value and the output current value to meet the expected value.
7. The method as recited in claim 2, further comprising:
acquiring temperature signals of the battery strings based on a preset acquisition frequency to obtain a plurality of groups of temperature signals;
determining a temperature change trend of the battery string based on the plurality of sets of temperature signals;
And determining a first working state of the battery string based on the temperature change trend.
8. The method as recited in claim 2, further comprising:
acquiring voltage signals of the battery strings based on a preset acquisition frequency to obtain a plurality of groups of voltage signals;
Determining a voltage variation trend of the battery string based on the plurality of sets of voltage signals;
and determining a second working state of the battery string based on the voltage change trend.
9. The method as recited in claim 2, further comprising:
collecting current signals of the battery strings based on preset collection frequency to obtain a plurality of groups of current signals;
And integrating the plurality of groups of current signals to determine the electric quantity information of the battery string.
10. The method as recited in claim 6, further comprising:
and dynamically adjusting the electric quantity information of the battery string based on the working state of the battery string.
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