A compensation method for measurement error of an AFE chip

Abstract

The application relates to a compensation method for measurement errors of an AFE chip, comprising the following steps: obtaining a measurement result of corresponding battery data provided by a highest-in-use measurement channel and a measurement result of corresponding battery data provided by a lowest-serial-number measurement channel; determining a working state of the AFE chip and a corresponding offset scaling parameter; calculating an error-compensated measurement result of the highest-in-use measurement channel and an error-compensated measurement result of the lowest-serial-number measurement channel based on the offset scaling parameter; wherein the calculation of the error-compensated measurement result of the highest-in-use measurement channel comprises calculating the sum of the measurement result of the highest-in-use measurement channel and the product of the offset scaling parameter and a first difference value; and wherein the calculation of the error-compensated measurement result of the lowest-serial-number measurement channel comprises calculating the sum of the measurement result of the lowest-serial-number measurement channel and the product of the offset scaling parameter and a second difference value.

Description

Technical Field

[0001] This application relates to analog front-end chips for battery management systems, and more particularly to a method for compensating for measurement errors in AFE chips. Background Technology

[0002] The analog front-end (AFE) chip is the core chip of the battery management system (BMS). It is used to accurately acquire and measure data such as voltage provided by individual cells connected in series. This is the foundation for the battery management system to achieve cell balancing, state estimation (such as SOC and SOH), and overvoltage / undervoltage protection. In addition, the battery management system also needs to synchronously acquire and measure data such as cell current, cell voltage, and cell temperature of individual cells.

[0003] In existing solutions, the AFE chip uses a multiplexer to sequentially switch the measurement channels electrically connected to each individual battery cell to acquire individual cell data, and then uses an analog-to-digital converter (ADC) to quantize the individual cell data. Alternatively, the AFE chip uses an independent ADC to simultaneously acquire and quantize each individual cell. To ensure measurement accuracy and suppress common-mode noise, an external RC filter network is typically added between the AFE chip's measurement port and the individual battery cell to form a low-pass filter. However, while the RC filter network improves the system's anti-interference capability, it also introduces a significant measurement error. This measurement error includes offset error and gain error. Offset error causes a fixed offset in the measurement results provided by the AFE chip, while gain error causes the measurement results to be proportionally distorted depending on the magnitude of the cell voltage applied to the measurement port.

[0004] Battery management systems (BMS) require synchronous sampling and measurement of cell data. However, existing BMS solutions utilize a controller, such as an MCU, to read the individual cell data collected by the AFE (Automatic Feeder) and perform additional compensation calculations. Because the controller cannot promptly detect the real-time operating current of the AFE, the compensation for offset and gain errors fails to meet accuracy requirements.

[0005] Therefore, there is an urgent need to provide a method for real-time, high-precision compensation of offset and gain errors introduced by the RC filter network based on the power consumption state of the AFE chip, which is built into the AFE chip. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this application proposes a method for compensating measurement errors of an AFE chip, comprising: acquiring the measurement results of the corresponding cell data provided by the highest-numbered measurement channel and the measurement results of the corresponding cell data provided by the lowest-numbered measurement channel; determining the operating state of the AFE chip and the corresponding offset scaling parameters; and calculating the error-compensated measurement results of the highest-numbered measurement channel and the lowest-numbered measurement channel based on the offset scaling parameters; wherein, calculating the error-compensated measurement results of the highest-numbered measurement channel includes calculating the product of the offset scaling parameters and a first difference and the measurement result of the highest-numbered measurement channel. The sum of measurement results; wherein, calculating the measurement result after error compensation for the lowest sequence measurement channel includes calculating the sum of the product of the offset scaling parameter and the second difference with the measurement result of the lowest sequence measurement channel; the first difference is the difference between the measurement result of the highest in-use measurement channel in the first working state and the measurement result in the second working state; the second difference is the difference between the measurement result of the lowest sequence measurement channel in the first working state and the measurement result in the second working state; wherein, the first working state is the state when all measurement channels in the AFE chip are in the on state; the second working state is the state when at least two measurement channels in the AFE chip are on.

[0007] Specifically, the compensation method further includes a method for determining the highest-used measurement channel, comprising: in the first operating state, starting from the measurement channel with the highest serial number in the AFE chip, acquiring the measurement results of the corresponding cells provided by each measurement channel in descending order; when the measurement result of the measurement channel is greater than a first threshold voltage, marking the measurement channel as the highest-used measurement channel.

[0008] Specifically, in the compensation method described above, in the second operating state, the AFE chip only has the highest-numbered and lowest-numbered measurement channels enabled.

[0009] Specifically, in the compensation method, the calculation of the offset scaling parameter includes the ratio of the difference between the operating current of the AFE chip in the preset operating state and the operating current in the second operating state to the difference between the operating current in the first operating state and the operating current in the second operating state.

[0010] Specifically, in the compensation method, when the value of the operating current in the second operating state is less than 100 mA, the value of the offset scaling parameter is the ratio of the operating current in the preset operating state to the operating current in the first operating state.

[0011] Specifically, in the compensation method, the calculation of the offset scaling parameter includes obtaining the total current required for other functions of the AFE chip besides cell data measurement under a preset operating state and obtaining an equivalent value of the corresponding number of measurement channels based on it; the ratio of the difference between the sum of the number of measurement channels activated under the preset operating state of the AFE chip and the equivalent value and the number of measurement channels activated under the second operating state, to the difference between the number of measurement channels activated under the first operating state and the number of measurement channels activated under the second operating state.

[0012] In particular, in the compensation method, the first threshold voltage is a value greater than 0.5V and less than 1V.

[0013] Specifically, the compensation method further includes: obtaining the gain error compensation value of the highest-numbered measurement channel and the gain error compensation value of the lowest-numbered measurement channel, respectively; obtaining the gain scaling factor of the AFE chip; calculating the product of the gain scaling factor and the gain error compensation value of the highest-numbered measurement channel, and multiplying the result by the offset error compensation result of the highest-numbered measurement channel to obtain the error-compensated measurement result of the highest-numbered measurement channel; calculating the product of the gain scaling factor and the gain error compensation value of the lowest-numbered measurement channel, and multiplying the result by the offset error compensation result of the lowest-numbered measurement channel to obtain the error-compensated measurement result of the lowest-numbered measurement channel.

[0014] Specifically, in the compensation method, the gain scaling factor is related to the input internal resistance of the AFE chip, the resistance value of the RC filter network when the AFE chip is calibrated at the factory, and the actual resistance value of the RC filter network when the AFE chip is in operation.

[0015] This application also relates to an AFE chip that performs the compensation method as described in any of the preceding applications.

[0016] This application also relates to an apparatus comprising a battery cell and an AFE chip as described above.

[0017] The AFE chip measurement error compensation method proposed in this application is built into the AFE chip. It can adaptively calculate and apply offset error and gain error compensation based on the chip's real-time operating current and the resistance value of the external RC network, so as to eliminate the offset error and gain error introduced by the RC filter network, thereby significantly improving the voltage acquisition accuracy of the BMS cell and the overall reliability of the BMS. Attached Figure Description

[0018] The preferred embodiments of this application will now be described in further detail with reference to the accompanying drawings, wherein: Figure 1This is a schematic diagram of the partial electrical connection structure between the battery cell assembly and the AFE chip.

[0019] Figure 2 This is a flowchart illustrating an error compensation method according to an embodiment of this application; and Figure 3 This is a flowchart illustrating an error compensation method according to another embodiment of this application. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the following detailed description, reference can be made to the accompanying drawings, which form part of this application and illustrate specific embodiments of the present application. In the drawings, similar reference numerals describe substantially similar components in different figures. Specific embodiments of the present application are described in sufficient detail below to enable those skilled in the art to implement the technical solutions of the present application. It should be understood that other embodiments may also be utilized, or structural, logical, or electrical changes may be made to the embodiments of the present application.

[0022] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. The lines connecting the units in the accompanying drawings are merely for illustrative purposes, indicating that at least the units at both ends of the line are communicating with each other, and are not intended to prevent unconnected units from communicating. Furthermore, the number of lines between two units is intended to indicate at least the number of signals involved in communication between the two units or at least the number of output terminals, and is not intended to limit communication between the two units to only the signals shown in the figures.

[0023] This application proposes a method for compensating measurement errors of an AFE chip. Without the involvement of a controller such as an MCU, the method compensates for the measurement errors of the AFE chip in real time and with high precision through offline calibration and real-time compensation, thereby eliminating the measurement errors introduced by the external RC filter network under different operating currents of the AFE chip.

[0024] Figure 1 This is a schematic diagram of the partial electrical connection structure between the battery cell assembly and the AFE chip.

[0025] In the local electrical connection structure between the battery pack and the AFE chip, the most common is... Figure 1 The circuit structure is shown. The cell group consists of m individual cells connected in series. Individual cells can include lithium manganese oxide, lithium cobalt oxide, etc. Here, m is a positive integer greater than or equal to 1. In the cell group, the first cell, Bat1, is the lowest-numbered cell, and the m-th cell, Batm, is the highest-numbered cell.

[0026] The AFE chip can include m+1 measurement ports. The first measurement port V1 is the lowest-numbered measurement port, and the (m+1)th measurement port Vm+1 is the highest-numbered measurement port. The positive and negative terminals of the lowest-numbered cell bat1 in the cell group are electrically connected to the lowest-numbered measurement port V1 and measurement port V2 of the AFE chip, respectively. Starting from measurement port V1, the measurement ports are connected to the m cells in the cell group one by one according to their measurement port numbers. The highest-numbered cell Batm is electrically connected to the measurement port Vm and the highest-numbered measurement port Vm+1 of the AFE chip. In this case, measurement port Vm+1 is also the highest-numbered measurement port in use, i.e., the most frequently used measurement channel. Each measurement port corresponds to a measurement channel within the AFE chip, used to measure the input voltage applied to the measurement port. In addition, the AFE chip may also include ports for other functions such as communication or control.

[0027] When the AFE chip provides more than m+1 measurement ports, measurement channels V1 to Vm+1, which are electrically connected to the battery pack, are active measurement channels. Measurement port Vm+1 is the most frequently used measurement port, while other unused measurement channels are electrically connected to adjacent channels. The lowest-numbered measurement port V1 corresponds to the lowest-numbered measurement channel within the AFE chip. The most frequently used measurement port Vm+1 corresponds to the most frequently used measurement channel within the AFE chip.

[0028] In the battery cell assembly, the positive and negative terminals of a single battery cell are electrically connected to two adjacent measurement ports in the AFE chip via acquisition lines. Two adjacent series-connected single battery cells can share the acquisition lines for either the positive or negative terminals. The m battery cells are electrically connected to the m+1 measurement channels inside the AFE chip.

[0029] Each acquisition line is equipped with a resistor R; that is, resistors R of the same value are respectively placed between the positive and negative terminals of each battery cell and the corresponding measurement port. A capacitor C is placed across two adjacent acquisition lines, thus forming the external RC filter network of the AFE chip together with the resistors R. Through the RC filter network, the individual battery cells connected in series in the battery cell group are electrically connected sequentially to the measurement ports V1 to Vm+1 of the AFE chip.

[0030] The AFE chip monitors the cell data provided by each individual cell in real time. This data is acquired through the AFE chip's measurement port and transmitted to the corresponding measurement channel within the chip for processing. During operation, the AFE chip's operating current is provided by the cell assembly. This operating current creates a voltage drop across the resistor R in the RC filter network, resulting in an offset error between the measurement results provided by the AFE chip and the actual cell data. Under the same operating state, i.e., at the same operating current, the offset error is a fixed deviation. Under different operating states, the number of measurement channels activated in the AFE chip varies, the operating current changes with the operating state, and the voltage drop across the resistor in the RC filter network changes with the operating current, thus altering the offset error. Furthermore, the input voltage of the AFE chip's measurement port is related to the cell data. During operation, in the acquisition circuit and its corresponding measurement channel, the resistor R in the external RC filter network and the AFE's input impedance Ri form a series voltage divider network, causing a proportional distortion in the measurement results provided by the AFE relative to the actual cell data, i.e., a gain error. This gain error changes proportionally with the cell data. Furthermore, changes in the resistance value R of the RC network will also lead to changes in the gain error.

[0031] When measuring cell data, these errors do not exist in every measurement channel. The positive and negative terminals of each cell in the cell assembly are electrically connected to the RC filter network. Except for the highest-numbered and lowest-numbered measurement channels, the connection nodes of adjacent series-connected cells share a single acquisition line. The measurement errors in the corresponding measurement channels of this acquisition line cancel each other out, so that offset errors and gain errors only exist in the highest-numbered and lowest-numbered measurement channels.

[0032] In the following description, the method for compensating for measurement errors of the AFE chip proposed in this application is explained with the assumption that the number of cells in the cell pack is m and the number of measurement ports provided by the AFE chip is greater than m+1. In this case, measurement port V1 is the lowest-numbered measurement port, and measurement port Vm+1 is the highest-numbered measurement port in use.

[0033] In one embodiment of this application, in order to ensure that the offset error and gain error of the measurement results provided by the designated measurement channel are compensated, the AFE chip needs to automatically determine the position of the highest active measurement channel electrically connected to the cell assembly.

[0034] According to one embodiment, the AFE chip provides n preset operating states for the user to select. The operating current corresponding to each preset operating state can be obtained before the chip leaves the factory. Here, n is a positive integer greater than or equal to 1, representing the type of operating current of the AFE chip.

[0035] According to one embodiment, before the AFE chip is woken up to perform cell data measurement, a wake-up command from the controller can be received, and the AFE chip can be initialized under the control of the wake-up command to determine the highest number of measurement channels in use.

[0036] Offset errors vary under different operating currents. Therefore, for the same tested cell, the AFE chip provides different measurement results under different operating currents. According to one embodiment, during initialization, the difference between the measurement result of the highest-used measurement channel under the operating current of the first operating state and the measurement result of the highest-used measurement channel under the operating current of the second operating state can also be obtained, and this difference is used as the first difference. The first difference represents the sum of offset errors caused by the resistor in the RC filter network on the measurement result of the highest-used measurement channel when the operating current switches from the operating current of the first operating state to the operating current of the second operating state. The first operating state is the state when all measurement channels in the AFE chip are turned on. The second operating state is the state when at least two measurement channels in the AFE chip are turned on. The operating current of the first operating state is greater than the operating current of the second operating state.

[0037] In another embodiment, the first operating state may correspond to the operating state of the AFE chip at maximum power consumption. At maximum power consumption, all internal measurement channels and communication modules of the AFE chip are enabled.

[0038] In one embodiment, the second operating state can also be the operating state when the AFE chip operates at minimum power consumption. When the AFE chip operates at minimum power consumption, only two measurement channels may be active. In one embodiment of this application, when the AFE chip operates at minimum power consumption, only the highest-numbered measurement channel and the lowest-numbered measurement channel are active.

[0039] In another embodiment, the initialization process can also be completed under the control of the controller when the AFE chip is powered on. The AFE chip stores the highest active measurement channel determined during the initialization process and the corresponding first difference value obtained, for later use by the AFE chip.

[0040] According to one embodiment, before measuring cell data, the AFE chip determines the usage status of other functional modules besides the cell measurement function and determines the number of measurement channels to be turned on based on the highest number of measurement channels in use, thereby determining the working state of the AFE chip and the corresponding operating current.

[0041] According to one embodiment, when the AFE chip is operating, its operating current is obtained based on its operating state. A corresponding offset scaling parameter is obtained based on the AFE chip's operating current, and this offset scaling parameter is applied to a first difference value to obtain the offset error compensation value for the highest-performing measurement channel. The offset scaling parameter is, during factory calibration, the ratio of the difference between the operating current in a preset operating state and the operating current in a second operating state to the maximum operating current change. The maximum operating current change is the difference between the operating current in the first operating state and the operating current in the second operating state. The offset scaling parameter represents the proportion of the current change between the operating current corresponding to the preset operating state and the operating current in the second operating state to the maximum operating current change. The AFE chip can have n preset operating states, and correspondingly, it has n offset scaling parameters, each corresponding to a specific operating current of the AFE chip. When the offset scaling parameter is applied to the first difference value, the total offset error is calculated based on the proportion of the operating current change to the maximum operating current change to obtain the offset error compensation value for the highest-performing measurement channel.

[0042] In one embodiment, when the operating current in the second operating state is less than 100 microamps, the offset scaling parameter can also be the ratio of the operating current in the preset operating state to the operating current in the first operating state. For example, the AFE chip has 20 measurement channels. In its maximum power consumption state, the AFE chip's operating current is 100A. In one operating state provided by the AFE chip, 11 measurement channels are used to measure cell assembly data, and the remaining 9 measurement channels are used to measure other data or for other purposes. In this state, the AFE chip's operating current is 50A. Under this operating current, the offset scaling parameter OFC_scale_1 is calculated as 50 / 100, which is 0.5.

[0043] In another embodiment, the offset scaling parameter can also be obtained during factory calibration based on the change in the number of measurement channels activated during the change of the AFE chip's operating current. Under different preset operating states, the AFE activates different numbers of measurement channels and enables corresponding other non-measurement function modules. During factory calibration, the number of measurement channels activated by the AFE chip in the preset operating state is obtained, and the total current required by other non-measurement functions in that preset operating state is obtained and equivalently converted to the corresponding number of measurement channels. That is, the non-measurement function modules are equivalently converted to measurement channels by using the ratio of the total current consumed by functions other than cell data measurement (i.e., non-measurement functions) to the standard current of a single measurement channel (the operating current when not actually operating). The number of measurement channels when the non-measurement function modules are equivalent to measurement channels is calculated. The change in the number of activated channels, Num1, is the sum of the number of measurement channels in the preset operating state and the equivalent number of measurement channels after converting the total current consumed by non-measurement functions. The sum is then subtracted from the number of measurement channels activated in the second operating state. The change in the number of activated channels, Num1, represents the change in the number of measurement channels activated when the AFE chip switches from the operating current of the preset operating state to the operating current of the second operating state. The total change in the number of activated measurement channels, Num2, is the difference between the number of activated measurement channels in the first operating state and the number of activated measurement channels in the second operating state. This difference represents the total change in the number of activated measurement channels when the operating current changes. In this case, the offset scaling parameter can be calculated as the ratio of the change in the number of activated measurement channels, Num1, to the total change in the number of activated measurement channels, Num2, which is Num1 / Num2. By calculating the proportion of the change in the number of activated measurement channels in the total change in the number of activated measurement channels, it reflects the proportion of the change in current between the operating current in the preset operating state and the operating current in the second operating state in the maximum change in operating current.

[0044] For example, an AFE chip includes 20 measurement channels. In the first operating state, all measurement channels of the AFE chip are turned on; in the second operating state, 4 measurement channels are turned on, and the operating current of each measurement channel is 1A. In a preset operating state of the AFE chip, the number of measurement channels turned on is 8, and the total current consumed by the non-measurement function modules is 2A. In this case, the non-measurement function modules in the AFE chip are considered as 2 measurement channels. The offset scaling parameter can be calculated as (8+2-4) / (20-4) = 0.375.

[0045] According to one embodiment, the offset scaling parameter of the highest-used measurement channel is multiplied by a first difference of the highest-used measurement channel, and the result is added to the measurement result of the corresponding cell data provided by the highest-used measurement channel, thereby performing offset error compensation on the measurement result of the highest-used measurement channel to obtain the offset error compensation result of the highest-used measurement channel.

[0046] Understandably, during the AFE chip initialization process, the difference between the measurement results of the lowest-order measurement channel under different operating currents is obtained, and this difference is used as the second difference. The second difference represents the sum of the offset errors caused by the resistance in the RC filter network at different operating currents in the measurement results of the lowest-order measurement channel. According to one embodiment, when the AFE chip is operating, the offset scaling parameter is applied to the second difference, and the obtained result is added to the measurement result of the corresponding cell data provided by the lowest-order measurement channel to obtain the offset error compensation result of the lowest-order measurement channel.

[0047] According to one embodiment, during the factory calibration of the AFE chip, the operating current in the first operating state and the operating current in the second operating state are obtained, and the values ​​of both are stored in the non-volatile memory of the AFE chip.

[0048] According to one embodiment, during factory calibration, the operating current corresponding to the preset operating state and the corresponding offset scaling parameters are stored in the non-volatile memory of the AFE chip for the AFE chip to call in actual use.

[0049] Furthermore, according to one embodiment, gain error compensation can be performed on the offset error compensation results of the highest-used measurement channel and the lowest-numbered measurement channel respectively, so as to obtain the error-compensated measurement results of the highest-used measurement channel and the lowest-numbered measurement channel respectively.

[0050] The analog chip measurement error compensation method proposed in this application enables the AFE chip to compensate for measurement errors based on its actual operating current, thereby reducing the lag in measurement error compensation and improving the accuracy of AFE chip error compensation.

[0051] Figure 2 This is a schematic flowchart of a measurement error compensation method according to an embodiment of this application.

[0052] Step 201: Receive the wake-up command sent by the controller. Under the control of the wake-up command, obtain the operating current in the first operating state, so that the AFE chip operates in the first operating state.

[0053] According to one embodiment, in the first operating state, the AFE chip activates all measurement channels, converts the input voltage received at the measurement port into a corresponding signal, and thus obtains the measurement result corresponding to the input voltage.

[0054] Step 202: Based on the operating current in the first operating state, determine the highest-performing measurement channel.

[0055] According to one embodiment, during the initialization phase, in a first operating state, the output of the measurement channel that is electrically connected to the battery cell and is in the on state is a value related to the corresponding battery cell data, while the output of other measurement channels is much smaller than the value of the battery cell data.

[0056] According to one embodiment, the method for determining the most active measurement channel may include: in a first operating state, starting with the measurement channel with the highest sequence number on the AFE chip, acquiring the measurement results provided by each measurement channel in descending order of their sequence numbers. The acquired measurement results of each measurement channel are compared with a first threshold voltage Vthr. If the measurement result provided by a measurement channel is greater than the first threshold voltage Vthr, that measurement channel is determined as the most active measurement channel, and the acquisition of measurement results from subsequent measurement channels is terminated. If the measurement result of that measurement channel is less than or equal to the first threshold voltage Vthr, it means that the measurement channel is idle, and the acquisition of the measurement result of the next measurement channel continues and is compared with the first threshold voltage Vthr. In this case, the AFE chip can quickly determine the most active measurement channel without relying on a controller and with only a minimal amount of storage.

[0057] In another embodiment, the method for determining the highest-used measurement channel may include: after receiving a measurement channel enable command from the controller, the AFE chip may obtain the measurement channel with the highest sequence number that needs to be in the enabled state from the measurement channel enable command as the highest-used measurement channel.

[0058] In one embodiment, the first threshold voltage Vthr is stored digitally in non-volatile memory. After the measurement result provided by the measurement channel is converted into digital form by the ADC, the measurement result is compared with the first threshold voltage inside the AFE chip.

[0059] In one embodiment, the first threshold voltage Vthr is a minimum value less than or equal to the cell data. In another embodiment, the first threshold voltage Vthr can be a value greater than 0.5V and less than 1V.

[0060] Step 203: In the first working state, obtain the measurement result of the corresponding cell data provided by the highest in-use measurement channel, and save the measurement result as the first working voltage reg_m_0.

[0061] Step 204: In the first working state, obtain the measurement result of the corresponding cell data provided by the lowest serial number measurement channel, and save the measurement result as the second working voltage reg_1_0.

[0062] In one embodiment, the first operating voltage and the second operating voltage can be in digital form.

[0063] Step 205: In the second working state, obtain the measurement result of the corresponding cell data provided by the highest in-use measurement channel, and save the measurement result as the third working voltage reg_m_1.

[0064] Step 206: In the second working state, obtain the measurement result of the corresponding cell data provided by the lowest serial number measurement channel, and save the measurement result as the fourth working voltage reg_1_1.

[0065] In one embodiment, the third and fourth operating voltages may be in digital form.

[0066] Step 207: Obtain the first difference OFC_m and the second difference OFC_1. The first difference OFC_m is the difference between the first operating voltage reg_m_0 and the third operating voltage reg_m_1 of the highest-numbered measurement channel. The second difference OFC_1 is the difference between the second operating voltage reg_1_0 and the fourth operating voltage reg_1_1 of the lowest-numbered measurement channel.

[0067] According to one embodiment, after initialization is completed, the AFE chip starts working under the control of the controller to collect and measure the data of individual cells in the battery pack in real time.

[0068] Step 208: Determine the operating state of the AFE chip, obtain the operating current of the AFE chip, and obtain the offset scaling parameter OFC_scale_n corresponding to the operating current.

[0069] According to one embodiment, based on the operating current of the AFE chip, a working current value stored in the AFE chip that is close to the working current under a preset operating state is selected, and the offset scaling parameter OFC_scale_n corresponding to the working current is obtained.

[0070] Step 209: Obtain the measurement result code_org_m of the corresponding cell data provided by the highest-numbered measurement channel and the measurement result code_org_1 of the corresponding cell data provided by the lowest-numbered measurement channel. Perform offset error compensation on both and obtain the offset error compensation result code_ofc_m of the highest-numbered measurement channel and the offset error compensation result code_ofc_1 of the lowest-numbered measurement channel, respectively.

[0071] According to one embodiment, the offset error compensation result code_ofc_m of the measurement result of the highest in-use measurement channel can be obtained by using formula (1) to perform offset error compensation on the measurement result code_org_m of the highest in-use measurement channel.

[0072] code_ofc_m = code_org_m + OFC_m OFC_scale_n (1) Here, OFC_scale_n represents the offset scaling parameter, which represents the nth operating current of the AFE chip.

[0073] In one embodiment, the offset error compensation result code_ofc_1 of the measurement result of the lowest serial number measurement channel can be obtained by using formula (2) to compensate for the measurement error of the corresponding cell data code_org_1 provided by the lowest serial number measurement channel.

[0074] code_ofc_1= code_org_1 + OFC_1 OFC_scale_n (2) According to one embodiment, after offset error compensation is performed on the measurement results of the highest-numbered and lowest-numbered measurement channels of the AFE chip, gain error compensation can be performed on both separately. In this case, the AFE chip can continue to perform the following steps.

[0075] Step 210: Obtain the gain error compensation value R_fsc_m of the highest-ranking measurement channel and the gain error compensation value R_fsc_1 of the lowest-ranking measurement channel. The gain error compensation value is the ratio of the precise reference voltage received by the measurement channel to its corresponding measurement result during the AFE chip's factory calibration. During factory calibration, the gain error compensation value for each measurement channel is obtained separately.

[0076] Step 211: Obtain the gain scaling factor fsc_scale.

[0077] In one embodiment, before the AFE chip leaves the factory, the resistance value Q of the resistor R in the RC network during factory calibration and the input internal resistance Ri of the AFE chip are obtained and stored in the non-volatile memory of the AFE chip. The user sets the actual resistance value Q' of the resistor in the RC filter network according to actual operating needs. Based on the resistance value Q of the resistor R in the RC network during factory calibration, the actual resistance value Q' of the resistor in the RC filter network under actual operating conditions, and the input internal resistance Ri of the AFE chip, the gain scaling factor fsc_scale of the AFE chip is obtained. (3) The gain scaling factor fsc_scale represents the deviation between the actual resistance value Q' of the resistor in the RC filter network under actual working conditions and the resistance value Q of the resistor in the RC filter network at the factory calibration. The gain scaling factor is used to adjust the gain error, eliminate the gain error introduced by the change of resistance in the RC filter network, and make the gain error compensation result more accurate.

[0078] In one embodiment, the actual resistance value Q' of the resistor in the RC filter network can be set by the user through the controller according to the actual situation, and the actual resistance value Q' of the resistor in the RC filter network can be stored in the AFE chip for subsequent use.

[0079] Step 212: Obtain the offset error compensation result code_ofc_m of the highest-numbered measurement channel and the offset error compensation result code_ofc_1 of the lowest-numbered measurement channel, and perform gain error compensation on both respectively to obtain the measurement results after error compensation for the highest-numbered measurement channel and the lowest-numbered measurement channel.

[0080] In one embodiment, gain error compensation can be performed on the offset error compensation result code_ofc_m of the highest in-use measurement channel using formula (4) to obtain the error-compensated measurement result code_cal_m of the corresponding cell data provided by the highest in-use measurement channel.

[0081] code_cal_m = code_ofc_m R_fsc_m fsc_scale (4) In one embodiment, gain error compensation can be performed on the offset error compensation result code_ofc_1 of the lowest sequence number measurement channel using formula (5) to obtain the error-compensated measurement result code_cal_1 of the corresponding cell data provided by the lowest sequence number measurement channel.

[0082] code_cal_1 = code_ofc_1 R_fsc_1 fsc_scale (5) Optionally, in addition to the offset error compensation and gain error compensation mentioned above, the compensation parameters of the ADC reference source and the ADC modulator itself can be applied to the offset error compensation results or the compensated measurement results of the highest-numbered measurement channel and the lowest-numbered measurement channel, respectively, in order to reduce the measurement error of the AFE chip and improve the measurement accuracy.

[0083] Figure 3 The diagram shown is a flowchart illustrating an error compensation method according to another embodiment of this application. Figure 3In the illustrated embodiment, gain error compensation can be performed first on the highest-numbered and lowest-numbered measurement channels in the AFE chip, followed by offset error compensation on both. The following steps are then performed in this case.

[0084] Step 301: Receive a wake-up command sent by the controller, and under the control of the wake-up command, obtain the operating current in the first working state so that the AFE chip works in the first working state.

[0085] Step 302: Based on the operating current of the first operating state, determine the highest-performing measurement channel in use.

[0086] Step 303: In the first working state, obtain the measurement result of the corresponding cell data provided by the highest in-use measurement channel, and save the measurement result as the first working voltage reg_m_0.

[0087] Step 304: In the first working state, obtain the measurement result of the corresponding cell data provided by the lowest serial number measurement channel, and save the measurement result as the second working voltage reg_1_0.

[0088] Step 305: In the second working state, obtain the measurement result of the corresponding cell data provided by the highest in-use measurement channel, and save the measurement result as the third working voltage reg_m_1.

[0089] Step 306: In the second working state, obtain the measurement result of the corresponding cell data provided by the lowest serial number measurement channel, and save the measurement result as the fourth working voltage reg_1_1.

[0090] Step 307: Obtain the first difference OFC_m and the second difference OFC_1.

[0091] According to one embodiment, after initialization is completed, the AFE chip begins to collect and measure the data of individual cells in the battery pack in real time under the control of the controller.

[0092] Step 308: Obtain the gain error compensation value R_fsc_m of the highest-numbered measurement channel and the gain error compensation value R_fsc_1 of the lowest-numbered measurement channel.

[0093] Step 309: Obtain the gain scaling factor fsc_scale.

[0094] Step 310: Obtain the measurement result code_org_m of the corresponding cell data provided by the highest-numbered measurement channel and the measurement result code_org_1 of the corresponding cell data provided by the lowest-numbered measurement channel. Perform gain error compensation on both and obtain the gain error compensation result code_fcs_m of the highest-numbered measurement channel and the gain error compensation result code_fcs_1 of the lowest-numbered measurement channel, respectively.

[0095] In one embodiment, gain error compensation for the measurement results of the highest-used measurement channel can be achieved by formula (6) to obtain the gain error compensation result code_fcs_m.

[0096] code_fcs_m = code_org_m R_fsc_m fsc_scale (6) In one embodiment, gain error compensation for the measurement result of the lowest sequence number measurement channel can be achieved by formula (7) to obtain the gain error compensation result code_fsc_1.

[0097] code_fcs_1= code_org_1 R_fsc_1 fsc_scale (7) Step 311: Determine the operating state of the AFE chip, obtain the operating current of the AFE chip, and obtain the offset scaling parameter OFC_scale_n corresponding to the operating current.

[0098] Step 312: Perform offset error compensation on the gain error compensation result code_fcs_m of the highest-numbered measurement channel and the gain error compensation result code_fcs_1 of the lowest-numbered measurement channel, and obtain the error-compensated measurement result code_cal_m of the highest-numbered measurement channel and the error-compensated measurement result code_cal_1 of the lowest-numbered measurement channel, respectively.

[0099] In one embodiment, the offset error of the highest-performing measurement channel can be compensated using formula (8) to obtain the measurement result code_cal_m after error compensation for the highest-performing measurement channel.

[0100] code_cal_m = code_fsc _m + OFC_m OFC_scale_n (8) In one embodiment, the offset error of the lowest sequence number measurement channel can be compensated by formula (9) to obtain the measurement result code_ofc_1 after error compensation of the lowest sequence number measurement channel.

[0101] code_cal_1= code_fsc_1 + OFC_1 OFC_scale_n (9) The method for compensating measurement errors of the analog front-end chip proposed in this application achieves dynamic compensation for offset and gain errors of actual measurement results within the AFE chip. Compared with external compensation methods for AFE, the compensation accuracy and efficiency are higher.

[0102] The above embodiments are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art can make various changes and modifications without departing from the scope of this application. Therefore, all equivalent technical solutions should also fall within the scope of this application.

Claims

1. A method for compensating for measurement errors in an AFE chip, characterized in that, include, Obtain the measurement results of the corresponding cell data provided by the highest-numbered measurement channel and the measurement results of the corresponding cell data provided by the lowest-numbered measurement channel; Determine the operating status of the AFE chip and the corresponding offset scaling parameters; Based on the offset scaling parameters, the measurement results after error compensation for the highest-ranking measurement channel and the measurement results after error compensation for the lowest-ranking measurement channel are calculated; wherein, calculating the measurement results after error compensation for the highest-ranking measurement channel includes summing the product of the offset scaling parameters and the first difference with the measurement results of the highest-ranking measurement channel; wherein, calculating the measurement results after error compensation for the lowest-ranking measurement channel includes summing the product of the offset scaling parameters and the second difference with the measurement results of the lowest-ranking measurement channel; The first difference is the difference between the measurement result of the highest-numbered measurement channel in the first working state and the measurement result in the second working state; the second difference is the difference between the measurement result of the lowest-numbered measurement channel in the first working state and the measurement result in the second working state; wherein, the first working state is the state when all measurement channels in the AFE chip are in the on state; the second working state is the state when at least two measurement channels in the AFE chip are on. The method for determining the highest-used measurement channel includes: in the first working state, starting from the measurement channel with the highest serial number in the AFE chip, acquiring the measurement results of the corresponding cells provided by each measurement channel in descending order; when the measurement result of the measurement channel is greater than a first threshold voltage, marking the measurement channel as the highest-used measurement channel; The offset scaling parameter is calculated as follows: the ratio of the difference between the operating current in the AFE chip's preset operating state and the operating current in the second operating state to the difference between the operating current in the first operating state and the operating current in the second operating state; or, Obtain the total current required for all functions of the AFE chip other than cell data measurement under the preset working state, and obtain the equivalent value of the corresponding number of measurement channels based on it; the ratio of the sum of the number of measurement channels opened under the preset working state of the AFE chip and the equivalent value to the number of measurement channels opened under the second working state, to the ratio of the number of measurement channels opened under the first working state to the number of measurement channels opened under the second working state.

2. The compensation method as described in claim 1, characterized in that, In the second operating state, only the highest-numbered measurement channel and the lowest-numbered measurement channel of the AFE chip are enabled.

3. The compensation method as described in claim 1, characterized in that, When the operating current value in the second operating state is less than 100 mA, the value of the offset scaling parameter is the ratio of the operating current in the preset operating state to the operating current in the first operating state.

4. The compensation method as described in claim 1, characterized in that, The first threshold voltage is a value greater than 0.5V and less than 1V.

5. The compensation method as described in claim 1, characterized in that, Also includes: Obtain the gain error compensation value of the highest-numbered measurement channel and the gain error compensation value of the lowest-numbered measurement channel, respectively. Obtain the gain scaling factor of the AFE chip; Calculate the product of the gain scaling factor and the gain error compensation value of the highest-used measurement channel, and multiply the result by the offset error compensation result of the highest-used measurement channel to obtain the measurement result after error compensation for the highest-used measurement channel. Calculate the product of the gain scaling factor and the gain error compensation value of the lowest sequence measurement channel, and multiply the result by the offset error compensation result of the lowest sequence measurement channel to obtain the measurement result after error compensation for the lowest sequence measurement channel.

6. The compensation method as described in claim 5, characterized in that, The gain scaling factor is related to the input internal resistance of the AFE chip, the resistance value of the RC filter network when the AFE chip is calibrated at the factory, and the actual resistance value of the RC filter network when the AFE chip is in operation.

7. An AFE chip, characterized in that, Perform the compensation method according to any one of claims 1-6.

8. A device, characterized in that, Includes the battery cell and the AFE chip as described in claim 7.

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