Circuit and method for automatically calibrating zero drift during cell voltage sampling
Through the circuit composed of MCU, charge pump, multiplexer and operational amplifier, the zero-point drift of the battery cell voltage in the battery management system is automatically calibrated, solving the problem of inaccurate measurement in the prior art, and achieving the accuracy and cost-effectiveness of voltage measurement.
Patent Information
- Application Number
- CN202510334452.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-20
- Publication Date
- 2025-06-27
AI Technical Summary
When sampling the battery voltage, existing battery management systems are difficult to effectively calibrate zero-point drift, resulting in inaccurate measurements and require an increase in negative voltage conversion chips, increasing circuit complexity and cost.
The circuit consisting of an MCU, a charge pump, a multiplexer and an operational amplifier is used to boost the main supply voltage or the total voltage of the battery pack through the charge pump, and voltage comparison and calibration are used by the multiplexer and an operational amplifier to automatically calibrate zero point drift.
It realizes automatic calibration of zero point drift while collecting the voltage of the battery cell, improves the accuracy and speed of measurement, and reduces circuit complexity and cost.
Smart Images
Figure CN120214573A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of battery management, and particularly relates to a circuit and method for automatically calibrating zero drift when sampling the voltage of battery cells. Background Art
[0002] Currently, with the development of new energy vehicles, the control of their batteries has become an important task. New energy vehicles mainly use a Battery Management System (BMS) to manage and control the batteries, aiming to ensure that the batteries can operate safely, stably, and efficiently throughout their entire life cycle. And the most core part is to sample the battery cells of the battery pack, which involves the accurate measurement of the voltage of each battery cell. This is crucial for the safety management and performance optimization of the batteries. To improve the measurement accuracy, it is necessary to consider the influence of the zero-drift voltage in the sampling circuit on the sampling voltage. However, currently, the sampling of battery cells mainly only measures the entire string. Therefore, the zero drift of the system voltage needs to be calibrated after sampling. Generally, the supply power of the operational amplifier is grounded and the positive power supply Vdd, and the output range is [0, Vdd]. And the zero-drift voltage of the operational amplifier may be a negative voltage. When the zero-drift voltage is a negative voltage, the system will consider the zero-drift voltage of the operational amplifier as 0V, which will lead to inaccurate measurement. To solve the above problems, it is necessary to add a conversion chip that provides a negative voltage, and the overall circuit is complex and the implementation cost is high. Summary of the Invention
[0003] The purpose of the present invention is to solve the problems existing in the prior art, and provide a circuit and method for automatically calibrating zero drift when sampling the voltage of battery cells, which uses a discrete device combination circuit to calibrate the zero drift while sampling the voltage.
[0004] The technical solution is as follows:
[0005] A circuit for automatically calibrating zero drift when sampling the voltage of battery cells includes an MCU, a charge pump, a multiplexer, and an operational amplifier; wherein the charge pump is respectively connected to the MCU, the multiplexer, and the operational amplifier, and boosts the main power supply voltage provided by the vehicle system or the total voltage of the battery cell group to supply power to the multiplexer and the operational amplifier; there are two multiplexers, whose address terminals are connected to the MCU, and the data terminals are respectively connected to the positive or negative electrodes of each battery cell in the battery cell group to collect voltage data, and the voltage data is input to the operational amplifier through the output terminals for comparison; after the operational amplifier accesses the reference voltage Uref provided by the vehicle system, it is connected to the MCU, and the comparison result is input to the MCU to obtain the sampled voltage data of the battery cells for calibrating zero drift.
[0006] Further, the charge pump consists of a P-channel MOS transistor, an N-channel MOS transistor, a capacitor, and three diodes. The gates of the two MOS transistors are connected to each other and connected to the MCU waveform output terminal. The sources are connected to each other and are respectively connected to the main supply voltage in series with a diode and the total voltage of the battery cell group through a capacitor, and then connected to an operational amplifier. A diode is also connected between the supply voltage and the total voltage of the battery cell group, so that the higher one of the main supply voltage and the total voltage of the battery cell group is input to the multiplexer and the operational amplifier.
[0007] Further, the charge pump boosts the higher one of the main supply voltage or the total voltage of the battery cell group, and the boosting amplitude is controlled by PWM.
[0008] Further, the number of data terminals of the multiplexer is the number of battery cells plus one.
[0009] A method for automatically calibrating zero drift when sampling the voltage of a battery cell uses the above circuit and performs the following steps:
[0010] Step 1: The MCU sends a PWM signal to the charge pump. The charge pump boosts the higher one of the main supply voltage provided by the vehicle system or the total voltage of the battery cell group and delivers it to the multiplexer and the operational amplifier.
[0011] Step 2: The MCU selects the data terminals connected to the same battery cell for the two multiplexers and reads the AD sampling value CELL_DETEC0 at this time, which is the zero drift voltage of the system.
[0012] Step 3: The MCU controls one multiplexer to collect the positive voltage U of the target battery cell in the battery cell group + and one multiplexer to collect the negative voltage U of the target battery cell in the battery cell group - , and reads the AD sampling value CELL_DETEC1 at this time.
[0013] Step 4: Subtracting the voltage CELL_DETEC0 in Step 2 from the voltage CELL_DETEC1 in Step 3 gives the voltage of a single battery cell with zero drift of the voltage calibrated.
[0014] Step 5: Repeat Steps 2 - 4 in sequence to obtain the voltage of each battery cell, and adding them up gives the voltage of the battery cell group with zero drift of the voltage calibrated.
[0015] Beneficial effects:
[0016] 1) The present invention automatically calibrates the zero drift of the voltage while sampling the voltage of the battery cell, and the obtained result is accurate and fast.
[0017] 2) The circuit is mainly composed of discrete devices, with a simple structure, low cost, and convenient maintenance. Description of the Drawings
[0018] Figure 1 is the logic circuit diagram of the present invention;
[0019] Figure 2 is the method flow chart of the present invention;
[0020] Figure 3 is the schematic diagram of the wiring points of the battery cell group composed of six battery cells in the sixth embodiment of the present invention. Detailed implementation manners
[0021] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The orientation or positional relationships indicated by the terms "upper", "lower", "front", "rear", "left", "right", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present invention.
[0022] As Figure 1 shown, a circuit and method for automatically calibrating zero drift when sampling the voltage of a battery cell include an MCU, a charge pump, a multiplexer and an operational amplifier; wherein the charge pump is respectively connected to the MCU, the multiplexer and the operational amplifier, and boosts the main power supply voltage provided by the vehicle system or the total voltage of the battery cell group to supply power to the multiplexer and the operational amplifier; there are two multiplexers, whose address terminals are connected to the MCU, and the data terminals are respectively connected to the positive or negative poles of each battery cell in the battery cell group to collect voltage data, and the voltage data is input to the operational amplifier through the output terminal for comparison; after the operational amplifier accesses the reference voltage Uref provided by the vehicle system, it is connected to the MCU, and the comparison result is input to the MCU to obtain the battery cell voltage sampling data for calibrating zero drift.
[0023] The charge pump is composed of a P-channel MOS transistor, an N-channel MOS transistor, a capacitor and three diodes. The gates of the two MOS transistors are connected to each other and connected to the waveform output terminal of the MCU, and the sources are connected to each other and then respectively connected to the main power supply voltage and the total voltage of the battery cell group in series with a diode through a capacitor, and then connected to the operational amplifier. A diode is also connected between the power supply voltage and the total voltage of the battery cell group.
[0024] The charge pump boosts the higher one of the main power supply voltage or the total voltage of the battery cell group, and the boosting amplitude is controlled by PWM.
[0025] The number of data terminals of the multiplexer is one more than the number of battery cells.
[0026] AsFigure 2 As shown in the figure, a method for automatically calibrating zero drift when sampling the voltage of a battery cell uses the above circuit and performs the following steps:
[0027] Step 1: The MCU sends a PWM signal to the charge pump, and the charge pump boosts the higher of the main power supply voltage provided by the vehicle system or the total voltage of the battery cell group, and delivers it to the multiplexer and the operational amplifier.
[0028] Step 2: The MCU connects the data terminals of the same battery cell selected by the two multiplexers, and reads the AD sampling value CELL_DETEC0 at this time, which is the zero drift voltage of the system.
[0029] Step 3: The MCU controls one multiplexer to collect the positive voltage U + of the target battery cell in the battery cell group, and one multiplexer collects the negative voltage U - of the target battery cell in the battery cell group, and reads the AD sampling value CELL_DETEC1 at this time.
[0030] Step 4: Subtract the voltage CELL_DETEC0 in Step 2 from the voltage CELL_DETEC1 in Step 3 to obtain the voltage of a single battery cell with zero drift of the voltage calibrated.
[0031] Step 5: Repeat Steps 2-4 in sequence to obtain the voltage of each battery cell, and add them up to obtain the voltage of the battery cell group with zero drift of the voltage calibrated.
[0032] Embodiment: As Figure 3 shown, a battery cell group composed of six battery cells needs to collect the voltage of a single battery cell, and seven collection points need to be collected to obtain the voltage of the six battery cells; when the voltage of the first battery cell is required, the potentials of points cell0 and cell1 are collected, and the potential of cell1 is subtracted from the potential of cell0 to obtain the voltage of the first battery cell; when the total voltage of the battery cell group is required, the potentials of cell0 and cell6 are collected, and the potential of cell6 is subtracted from the potential of cell0 to obtain the voltage of the assembled battery cells.
[0033] Therefore, first the MCU sends a PWM signal to the charge pump, and the charge pump boosts the higher of the main power supply voltage provided by the vehicle system or the total voltage of the battery cell group, and delivers it to the multiplexer and the operational amplifier for power supply, avoiding problems such as interference in the system, and the boost amplitude is controlled by PWM.
[0034] Since the output voltage of the operational amplifier is the zero-drift voltage within the system when the input voltages at both ends of the operational amplifier are zero, and two multiplexers select the bottommost CELL0 of the battery cells simultaneously, the output voltage at this time is the zero-drift voltage CELL_DETEC0 of the system. The MCU stores this zero-drift voltage CELL_DETEC0. The MCU controls one multiplexer to collect the positive voltage U+ of the target battery cell in the battery cell group, and one multiplexer to collect the negative voltage U- of the target battery cell in the battery cell group, reads the AD sampling value CELL_DETEC1 at this time, and subtracts the zero-drift voltage CELL_DETEC0, thus achieving the automatic calibration of the voltage zero drift of a single battery cell. Measure the voltages of six battery cells in sequence and then add them up to obtain the voltage of the battery cell group with the voltage zero drift calibrated.
[0035] By adding a reference voltage Uref to the positive input terminal of the operational amplifier, the output voltage Uout of the summing circuit is Uout=(U + +Uref)-U - . When the zero-drift voltage is less than 0V, it will not cause Uout to be less than 0V, avoiding the problem that the zero-drift voltage is regarded as 0V.
[0036] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, and improvements made within the principle and spirit of the present invention shall be included within the protection scope of the present invention.
Claims
1. A circuit for automatically calibrating zero drift when sampling a cell voltage, comprising an MCU, a charge pump, a multiplexer and an operational amplifier; wherein the charge pump is connected to the MCU, the multiplexer and the operational amplifier respectively, and the main power supply voltage provided by the vehicle system or the total voltage of the cell group is boosted to power the multiplexer and the operational amplifier; there are two multiplexers, whose address terminals are connected to the MCU, and whose data terminals are respectively connected to the positive or negative pole of each cell in the cell group to collect voltage data, and the data is input to the operational amplifier through the output terminal for comparison; the operational amplifier is connected to the MCU after being connected to a reference voltage Uref provided by the vehicle system, and the comparison result is input to the MCU to obtain the cell voltage sampling data for calibrating zero drift.
2. The circuit and method for automatically calibrating zero drift when sampling a cell voltage as claimed in claim 1, characterized in that: The charge pump is composed of a P-channel MOS tube, an N-channel MOS tube, a capacitor and three diodes, wherein the gates of the two MOS tubes are connected to each other and connected to the waveform output end of the MCU, the sources are connected to each other and connected to the main power supply voltage and the total voltage of the battery cell group through a capacitor, and then connected to the operational amplifier, and a diode is also connected between the power supply voltage and the total voltage of the battery cell group.
3. The circuit and method for automatically calibrating zero drift when sampling a cell voltage as claimed in claim 1, characterized in that: The charge pump boosts the higher one of the main power supply voltage and the total voltage of the battery cell group, and the boost amplitude is controlled by PWM.
4. The circuit and method for automatically calibrating zero drift when sampling cell voltage as claimed in claim 1, characterized in that: The number of data terminals of the multiplexer is the number of battery cells plus one.
5. A method for automatically calibrating zero drift when sampling a cell voltage, using the circuit as described in claims 1-4, and performing the following steps: Step 1: The MCU sends a PWM signal to the charge pump, which boosts the higher voltage of the main power supply voltage provided by the vehicle system or the total voltage of the battery pack and transmits it to the multiplexer and operational amplifier; Step 2: The MCU selects the data end of the same battery cell for the two multiplexers, and reads the AD sampling value CELL_DETEC0 at this time, which is the zero drift voltage of the system; Step 3: The MCU controls a multiplexer to collect the positive voltage U of the target cell in the cell group + , a multiplexer collects the negative voltage U of the target cell in the cell group - , read the AD sampling value CELL_DETEC1 at this time; Step 4: Subtract the voltage CELL_DETEC0 in step 2 from the voltage CELL_DETEC1 in step 3 to obtain the single cell voltage with the voltage zero drift calibrated; Step 5: Repeat steps 2-4 in sequence to obtain the voltage of each battery cell, and add them together to obtain the battery cell group voltage after calibrating the voltage zero drift.