Power supply circuit of battery pack string voltage acquisition circuit

Abstract

The embodiment of the utility model discloses a power supply circuit for a battery pack string voltage acquisition circuit, and the circuit comprises a plurality of batteries which are connected in series to form a battery pack string. The power supply module comprises a positive constant voltage output module and a negative constant voltage output module which are respectively used for outputting a positive power supply voltage and a negative power supply voltage, and the value of the positive power supply voltage is matched with the rated voltage value of the battery string group; the voltage acquisition circuit comprises a plurality of differential amplifiers, and the plurality of differential amplifiers are respectively connected with the plurality of batteries in a one-to-one correspondence manner; the power supply end of the differential amplifier is respectively connected with the positive power supply voltage and the negative power supply voltage, and the power supply module, the differential amplifier and the battery are in short circuit to a common ground. Therefore, the problem that the input common-mode voltage range of the battery pack string cannot meet the requirement in the voltage acquisition circuit in the prior art can be effectively solved.

Description

Technical Field

[0001] The utility model relates to the field of line sequence detection systems, in particular to a power supply circuit of a battery string voltage acquisition circuit. Background Art

[0002] With the rapid development of new energy vehicles, the demand for chemically divided capacity power supplies is increasing. Among them, a chemically divided capacity power supply is a battery that uses chemical reactions to store and release energy. Its working current and voltage will change with the change of the charge in the chemical component container. In order to maintain the stability of the divided capacity power supply, an auxiliary power supply is required to provide stable current and voltage to ensure that the chemically divided capacity power supply can continue to work stably. In the formation and capacity division process of traditional power batteries, some battery manufacturers use independent power channels to charge and discharge each battery separately.

[0003] Among them, lithium batteries have no electricity when they are assembled and must be charged and activated. The first charge is called "formation", which is used to activate the active materials in the battery. Formation, also known as "activation", is a very complicated process and also a very important process that affects battery performance, because during the first charge of the battery, a thin passivation layer covering the surface of the carbon electrode will inevitably form at the interface between the carbon negative electrode and the electrolyte, which is called the solid electrolyte interface film or SEI film.

[0004] Capacity division is to charge and discharge the battery, and detect the discharge capacity when the capacity division is full to determine the capacity of the battery. Only batteries whose tested capacity meets or exceeds the designed capacity are qualified. The process of selecting qualified batteries through capacity testing is called capacity division.

[0005] As the requirements for battery production efficiency and the cost of formation and capacity division equipment become higher and higher, many battery manufacturers and equipment manufacturers have jointly upgraded their equipment, and gradually used "battery strings" to replace "independent batteries" in the formation and capacity division processes. After the upgrade, 12 batteries are connected in series to form a "battery string", which is then connected to the power channel. Through a power system, 12 batteries can be charged and discharged at the same time, greatly improving production efficiency.

[0006] However, during the charging and discharging process, the battery voltage of each battery in the "battery string" needs to be accurately monitored in real time. Once the voltage of one of the batteries reaches the threshold in the process, the process needs to be stopped or protected. Battery manufacturers require the acquisition error of the battery voltage of each battery in the "battery string" to be within 3mV, which is a relatively high requirement in the industry. The design of the "battery string high-precision voltage acquisition circuit" (hereinafter referred to as the voltage acquisition circuit) needs to consider the coordination with the power system, cost, high precision and other performance, which is quite difficult.

[0007] In order to ensure the high real-time performance of battery voltage monitoring, the output of the acquisition circuit needs to be directly given to the analog-to-digital converter chip in the power system, and the common ground of the acquisition circuit needs to be short-circuited with the common ground of the power system (where the common ground refers to the reference point of all signals in the circuit system). Since the voltage of the single battery in the "battery string" is 0-5V, the common-mode voltage change of each battery relative to the common ground may be large. Because there are 12 batteries, the maximum input common-mode voltage of the batteries connected in series is 60V. At this time, the acquisition circuit needs to have a higher common-mode voltage rejection ratio, so 12 "differential amplifier" chips with built-in high-precision resistors and high common-mode rejection ratio must be used to collect the voltage of each battery separately. Considering the delivery time, cost and performance, the "differential amplifier" chip generally uses the INA592 chip.

[0008] refer to Figure 1 , the existing voltage acquisition circuits are often powered by traditional positive and negative balanced power supply voltages, that is, the absolute values ​​of the positive power supply voltage and the negative power supply voltage are equal. Since the gain of the INA592 chip differential amplifier is configured to 0.5 and the maximum power supply voltage is 36V, the traditional positive and negative power supply voltages are generally set to ±18V. Due to the internal resistance configuration of the chip, the INA592 input voltage range is three times the positive and negative power supply voltages, so the input common-mode voltage range of the voltage acquisition circuit is -54.3V to +54V, which cannot meet the 60V common-mode voltage requirement. Summary of the invention

[0009] In view of the problems existing in the above-mentioned prior art, the utility model provides a power supply circuit for a battery string voltage acquisition circuit, which can effectively solve the problem existing in the above-mentioned prior art that the input common-mode voltage range of the battery string in the voltage acquisition circuit does not meet the requirements.

[0010] The power supply circuit of the battery string voltage acquisition circuit of the utility model comprises:

[0011] A plurality of batteries, wherein a plurality of the batteries are connected in series to form a battery string;

[0012] A power supply module, the power supply module comprising a positive constant voltage output module and a negative constant voltage output module, which are used to output a positive supply voltage and a negative supply voltage respectively, and the value of the positive supply voltage matches the rated voltage value of the battery string group;

[0013] A voltage collection circuit, the voltage collection circuit comprising a plurality of differential amplifiers, the plurality of differential amplifiers being connected to the plurality of batteries in a one-to-one correspondence, and power supply ends of the differential amplifiers being connected to a positive power supply end and a negative power supply end, respectively;

[0014] The power module, the differential amplifier and the battery are short-circuited to a common ground.

[0015] Furthermore, the positive supply voltage is connected to the positive supply terminal of the differential amplifier, the negative supply voltage is connected to the negative supply terminal of the differential amplifier, and the input terminals of the plurality of differential amplifiers are respectively connected to the positive and negative poles of the plurality of batteries.

[0016] Furthermore, the voltage difference between the positive power supply voltage and the negative power supply voltage is smaller than the maximum power supply voltage of the chip of the differential amplifier, and the voltage sum between the positive power supply voltage and the negative power supply voltage is larger than the minimum power supply voltage of the chip of the differential amplifier.

[0017] Furthermore, a value of the negative supply voltage is within a rated negative voltage range of the chip of the differential amplifier.

[0018] Furthermore, the differential amplifier chip adopts INA592 chip.

[0019] Further, a plurality of differential amplifiers are respectively used to adopt voltages of a plurality of batteries.

[0020] Furthermore, the differential amplifier chip is used to determine the common mode rejection ratio of the voltage acquisition circuit according to the maximum common mode input voltage after a plurality of the batteries are connected in series.

[0021] Furthermore, the differential amplifier chip is used to determine the input voltage of the differential amplifier according to the gain configuration of the chip.

[0022] Furthermore, the input voltage of the differential amplifier is determined according to the negative supply voltage, the voltage of the reference pin and the gain configuration.

[0023] Further, the gain configuration of the chip is determined according to the resistance configuration of the chip.

[0024] The above technical solution has the following advantages or beneficial effects:

[0025] This application uses a conventional constant voltage output module to output positive supply voltage and negative supply voltage respectively, and then distributes them to the required differential amplifier, thereby realizing unbalanced power supply to the differential amplifier. The value of the positive supply voltage matches the rated voltage value of the battery string group, thereby meeting the input voltage range requirements of the voltage acquisition circuit.

[0026] Therefore, the present application uses an unbalanced power supply method for the chip so that the voltage acquisition circuit composed of the chip meets the input voltage range requirements required for high real-time battery voltage monitoring. The circuit of the present application uses the differential amplifier chip INA592, which has high common-mode rejection ratio, wide bandwidth, and high precision, which improves the reliability of the circuit. The positive and negative power supply voltages of the circuit of the present application are uniformly powered by a conventional constant voltage output module, which is more organized in circuit layout and convenient for subsequent circuit maintenance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0028] Figure 1 It is a schematic diagram of the power supply circuit structure of a battery string voltage acquisition circuit provided by the prior art;

[0029] Figure 2 This is a schematic diagram of the design idea of ​​a battery string voltage acquisition circuit provided in an embodiment of the present application;

[0030] Figure 3 It is a schematic diagram of the power supply circuit structure of a battery string voltage acquisition circuit provided in an embodiment of the present application.

[0031] In the figure: 1. power module; 11. positive supply voltage; 12. negative supply voltage; 2. voltage acquisition circuit; 21. differential amplifier; 3. battery. Specific embodiments

[0032] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0033] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first" and "second" are used only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0034] In this application, the word "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described in this application as "exemplary" is not necessarily to be construed as being preferred or advantageous over other embodiments. The following description is given to enable any technician in the field to implement and use the present application. In the following description, details are listed for the purpose of explanation. It should be understood that a person of ordinary skill in the art can recognize that the present application can be implemented without using these specific details. In other instances, well-known structures and processes will not be elaborated in detail to avoid obscuring the description of the present application with unnecessary details. Therefore, the present application is not intended to be limited to the embodiments shown, but is consistent with the widest scope consistent with the principles and features disclosed in the present application.

[0035] refer to Figure 2 , Figure 3 The power supply circuit of the battery string voltage acquisition circuit 2 of the utility model includes: a plurality of batteries 3, wherein the plurality of batteries 3 are connected in series to form a battery string; a power module 1, wherein the power module 1 includes a positive constant voltage output module and a negative constant voltage output module, which are respectively used to output a positive power supply voltage 11 and a negative power supply voltage 12, wherein the value of the positive power supply voltage 11 matches the rated voltage value of the battery string 3; a voltage acquisition circuit 2, wherein the voltage acquisition circuit 2 includes a plurality of differential amplifiers 21, wherein the plurality of differential amplifiers 21 are respectively connected to the plurality of batteries 3 in a one-to-one correspondence, wherein the differential amplifiers are respectively connected to the positive power supply voltage 11 and the negative power supply voltage 12; the power module 1, the differential amplifier 21 and the battery 3 are short-circuited to a common ground.

[0036] The present application adopts a conventional constant voltage output module to output the positive power supply voltage 11 and the negative power supply voltage 12 respectively, and then distributes them to the required differential amplifier 21, thereby realizing unbalanced power supply to the differential amplifier 21. The value of the positive power supply voltage 11 matches the rated voltage value of the battery 3 string group, thereby meeting the input voltage range requirement of the voltage acquisition circuit 2.

[0037] Further, the positive power supply voltage is connected to the positive power supply terminal of the differential amplifier 21, the negative power supply voltage 12 is connected to the negative power supply terminal of the differential amplifier 21, and the output terminals of the plurality of differential amplifiers 21 are respectively connected to the positive and negative poles of the plurality of batteries 3. Further, the positive power supply voltage is connected to the positive power supply terminal of the differential amplifier, the negative power supply voltage is connected to the negative power supply terminal of the differential amplifier, and the input terminals of the plurality of differential amplifiers are respectively connected to the positive and negative poles of the plurality of batteries. Further, the voltage difference between the positive power supply voltage and the negative power supply voltage is less than the maximum power supply voltage of the chip of the differential amplifier, and the voltage sum between the positive power supply voltage and the negative power supply voltage is greater than the minimum power supply voltage of the chip of the differential amplifier. Further, the value of the negative power supply voltage is within the rated negative voltage range of the chip of the differential amplifier. Further, the chip of the differential amplifier adopts the INA592 chip. Further, the plurality of differential amplifiers are respectively used to adopt the voltages of the plurality of batteries. Further, the chip of the differential amplifier is used to determine the common mode rejection ratio of the voltage acquisition circuit according to the maximum common mode input voltage after the plurality of batteries are connected in series. Further, the chip of the differential amplifier is used to determine the input voltage of the differential amplifier according to the gain configuration of the chip. Further, the input voltage of the differential amplifier is determined according to the negative supply voltage, the voltage of the reference pin and the gain configuration. Further, the gain configuration of the chip is determined according to the resistance configuration of the chip.

[0038] Among them, the common ground refers to the reference potential of all signals in the circuit system. The mode of common grounding is a common mode. In order to ensure the high real-time performance of battery 3 voltage monitoring, the output of the acquisition circuit needs to be directly given to the ADC (Analog-to-Digital Converter) analog-to-digital converter chip in the power supply system, and the common ground of the acquisition circuit needs to be short-circuited with the common ground of the power supply system. Specifically, the ground wire of the power module 1, the negative input terminal of the differential amplifier 21, and the negative pole of the battery 3 are tied together and grounded together.

[0039] Among them, a battery string refers to connecting 12 batteries 3 in series to form a "battery string" and then connecting it to a power channel. Through a power system, 12 batteries 3 can be charged and discharged at the same time, greatly improving production efficiency. Chemically-compounded battery series connection is a technology that connects multiple batteries with the same chemical composition in a certain way. Under normal circumstances, the capacity of a battery is difficult to directly meet some specific needs, and chemically-compounded battery series connection can obtain the required higher capacity by combining multiple batteries.

[0040] There are many ways to connect the batteries in series. The following are three common ways:

[0041] Inline series connection: Inline series connection is to connect the positive and negative electrodes of multiple batteries in sequence to form a battery series link. This method can increase the total voltage of the battery pack, but the current capacity remains unchanged;

[0042] Parallel series connection: connecting the positive poles of multiple batteries to each other, and the negative poles to each other. This method can increase the total current capacity of the battery pack without changing the voltage.

[0043] Hybrid series connection combines in-line series connection and parallel series connection to increase voltage and current capacity at the same time. This method can meet different needs more flexibly.

[0044] Among them, the present application adopts a battery string obtained by connecting the batteries in series in an in-line manner.

[0045] Among them, the battery sampling circuit usually consists of the following parts:

[0046] Sampling circuit: used to collect the voltage or current signal of the battery and convert it into an electrical signal that can be used for measurement and calculation. The sampling circuit usually uses a dedicated analog-to-digital converter (ADC) and uses components such as suitable amplifiers, filters, and voltage reference sources.

[0047] Control circuit: used to control the operation of the sampling circuit and data processing, usually including functions such as timing control, data conversion and data storage. The control circuit is usually implemented by a microcontroller (MCU) or other logic circuits.

[0048] Power management circuit: used to manage the power supply of the battery, including battery charging, discharge control, low power mode switching and other functions. Including power switch, power regulator, charging circuit and battery protection circuit, etc.

[0049] Communication interface: used for data communication with other devices, such as transferring sampled data to a host computer or other devices. The communication interface usually uses a serial interface, such as UART, SPI or I2C.

[0050] The present application mainly improves the power management circuit and improves the power supply circuit of the voltage acquisition circuit.

[0051] Among them, there are many voltage measurement schemes. This application adopts the common mode measurement method. Common mode measurement is to measure the voltage of each point relative to the same reference point with precision resistors attenuating proportionally, and then subtract them in sequence to obtain the voltage of each battery. This method is suitable for occasions where the number of batteries in series is small or the measurement accuracy requirement is not high.

[0052] The differential amplifier 21 is a generalization of a common single-ended input amplifier. As long as one input terminal of the differential amplifier 21 is grounded, a single-ended input amplifier can be obtained. In the present application, the voltage acquisition circuit 2 where the differential amplifier 21 is located is connected to a common ground, so the differential amplifier 21 can be regarded as a single-ended input amplifier.

[0053] The differential amplifier 21 is an electronic amplifier that amplifies the difference between the voltages of the two input terminals with a fixed gain. The ability of the differential amplifier 21 to eliminate the common-mode signal is usually measured by the common-mode rejection ratio (CMRR), which is the ratio of the differential-mode gain to the common-mode gain. The smaller the common-mode gain, the larger the common-mode rejection ratio.

[0054] Among them, the common mode voltage, that is, the average voltage at the measurement input is close to zero. This makes it easier to design the power supply circuit and select devices suitable for this measurement. The voltage measured by the low-side current sensing circuit is close to ground. When dealing with very high voltages or in applications where the power supply voltage may be prone to spikes or surges, this method is preferred to measure current. This application uses the common mode voltage method to collect the battery voltage.

[0055] Among them, the voltage difference between the positive power supply voltage 11 and the negative power supply voltage 12 is less than the maximum power supply voltage of the chip of the differential amplifier 21, and the voltage sum between the positive power supply voltage 11 and the negative power supply voltage 12 is greater than the minimum power supply voltage of the chip of the differential amplifier 21.

[0056] In a specific embodiment, the gain of the INA592 chip used in this application needs to be configured to 0.5, and the gain configuration of the chip is determined according to the resistance configuration of the chip. This application uses a fixed gain chip. Of course, it can be understood that the gain value of the chip can also be determined according to the resistance configuration of the chip.

[0057] The input voltage of the differential amplifier 21 is determined according to the gain configuration of the chip. According to the gain configuration of the chip and the positive supply voltage 11, it can be calculated that the maximum input voltage of the differential amplifier 21 is 60V, which matches the maximum common mode voltage of the battery string.

[0058] In the present application, a certain voltage is also given to the reference pin, so that the battery 3 voltage can also collect a certain negative voltage range. The maximum power supply voltage of the chip is 36 V. The voltage difference between the positive power supply voltage 11 and the negative power supply voltage 12 is less than the maximum power supply voltage of the chip of the differential amplifier 21.

[0059] In one embodiment, the positive power supply voltage is 1120V and the negative power supply voltage is 12-15V. The voltage between the positive power supply voltage 11 and the negative power supply voltage 12 is greater than the minimum power supply voltage of the chip of the differential amplifier 21. The difference between the positive and negative power supply voltages 12 of this power supply mode meets the requirement of the chip INA592 power supply voltage of 4.5V to 36V.

[0060] It is understandable that within a certain range, the positive power supply voltage 11 can be selected to be a higher value, and the negative power supply voltage 12 can be selected to be a higher or lower value. No matter which option is selected, it is necessary to meet the normal power supply of the chip INA592. It can be reasonably selected according to the actual signal receiving and sending conditions and the cost, power consumption and other related factors that need to be considered when designing the circuit. It only needs to meet the matching of the sampling input voltage and the maximum common mode voltage of the battery string.

[0061] Furthermore, the value of the negative supply voltage 12 is within the rated negative voltage range of the chip of the differential amplifier 21 .

[0062] In order to meet the high timeliness of the battery 3 voltage monitoring, the common ground of the acquisition circuit is short-circuited with the common ground of the power system, so the lowest voltage of the negative input terminal of the acquisition circuit will only be around 0V. From the chip INA592 specification, it can be seen that the voltage of the reference pin is about 0.3V, and the input voltage of the differential amplifier 21 is determined according to the negative power supply voltage 12, the voltage of the reference pin and the gain configuration. The lowest value of the input voltage range is -45.3V, which has sufficient margin, so the negative power supply voltage 12 also meets the input requirements.

[0063] In one embodiment, since the voltage of the single battery 3 in the "battery string" is between 0 and 5V, the common mode voltage of each battery 3 relative to the common ground may vary greatly. Since there are 12 batteries 3, the maximum input common mode voltage of the batteries 3 connected in series is 60V. At this time, the acquisition circuit needs to have a higher common mode voltage rejection ratio, so 12 "differential amplifier 21" chips with built-in high-precision resistors and high common mode rejection ratio must be used to collect the voltage of each battery 3 respectively.

[0064] Since the gain of the INA592 chip differential amplifier is configured to 0.5 and the maximum power supply voltage is 36V, the reference Figure 1, the positive and negative supply voltages are generally set to ±18V. Due to the internal resistance configuration of the chip, the input voltage range of INA592 is three times the positive and negative supply voltages, so the input common-mode voltage range of the voltage acquisition circuit is -54.3V to +54V, which does not meet the 60V common-mode voltage requirement. The prior art does not consider the connection and coordination with the power supply system, so the input common-mode voltage range of the voltage acquisition circuit does not meet the requirements. The present application designs a new power supply method, that is, a positive supply voltage of 20V and a negative supply voltage of -15V. The difference between the positive and negative supply voltages of this power supply method meets the chip INA592 supply voltage requirement of 4.5V to 36V.

[0065] Therefore, the present application uses an unbalanced power supply method for the chip so that the voltage acquisition circuit 2 composed of the chip meets the input voltage range requirements required for high real-time battery 3 voltage monitoring. The circuit of the present application uses a differential amplifier 21 chip INA592, which has high common mode rejection ratio, wide bandwidth, and high precision, which improves the reliability of the circuit. The positive and negative power supply voltages 12 of the circuit of the present application are uniformly powered by a conventional constant voltage output module, which is more organized in circuit layout and convenient for subsequent circuit maintenance.

[0066] The power supply circuit of a battery string voltage acquisition circuit 2 provided in an embodiment of the present application is introduced in detail above. Specific examples are used in this article to illustrate the principles and embodiments of the present application. The description of the above embodiments is only used to help understand the method of the present application and its core idea; at the same time, for technical personnel in this field, according to the idea of ​​the present application, there will be changes in the specific embodiments and application scope. In summary, the content of this specification should not be understood as a limitation on the present application.

Claims

1. A power supply circuit for a battery string voltage acquisition circuit, characterized in that: include; A plurality of batteries (3), wherein the plurality of batteries (3) are connected in series to form a battery string; A power module (1), the power module (1) comprising a positive constant voltage output module and a negative constant voltage output module, respectively used to output a positive power supply voltage (11) and a negative power supply voltage (12), the value of the positive power supply voltage (11) matching the rated voltage value of the battery (3) string group; A voltage acquisition circuit (2), the voltage acquisition circuit (2) comprising a plurality of differential amplifiers (21), the plurality of differential amplifiers (21) being connected to the plurality of batteries (3) in a one-to-one correspondence, respectively, and power supply ends of the differential amplifiers (21) being connected to the positive power supply voltage (11) and the negative power supply voltage (12) respectively; The power module (1), the differential amplifier (21) and the battery (3) are short-circuited to a common ground.

2. A power supply circuit for a battery string voltage acquisition circuit (2) according to claim 1, characterized in that: The positive power supply voltage is connected to the positive power supply terminal of the differential amplifier (21), the negative power supply voltage (12) is connected to the negative power supply terminal of the differential amplifier (21), and the input terminals of the plurality of differential amplifiers (21) are respectively connected to the positive and negative poles of the plurality of batteries (3).

3. A power supply circuit for a battery string voltage acquisition circuit (2) according to claim 2, characterized in that: The voltage difference between the positive power supply voltage (11) and the negative power supply voltage (12) is smaller than the maximum power supply voltage of the chip of the differential amplifier (21), and the voltage sum between the positive power supply voltage (11) and the negative power supply voltage (12) is larger than the minimum power supply voltage of the chip of the differential amplifier (21).

4. A power supply circuit for a battery string voltage acquisition circuit (2) according to claim 3, characterized in that: The value of the negative power supply voltage (12) is within the rated negative voltage range of the chip of the differential amplifier (21).

5. The power supply circuit of a battery string voltage acquisition circuit (2) according to claim 1, characterized in that: The chip of the differential amplifier (21) is an INA592 chip.

6. A power supply circuit for a battery string voltage acquisition circuit (2) according to claim 5, characterized in that: The plurality of differential amplifiers (21) are respectively used to adopt the voltages of the plurality of batteries (3).

7. A power supply circuit for a battery string voltage acquisition circuit (2) according to claim 6, characterized in that: The chip of the differential amplifier (21) is used to determine the common mode rejection ratio of the voltage acquisition circuit (2) according to the maximum common mode input voltage after a plurality of batteries (3) are connected in series.

8. A power supply circuit for a battery string voltage acquisition circuit (2) according to claim 7, characterized in that: The chip of the differential amplifier (21) is used to determine the input voltage of the differential amplifier (21) according to the gain configuration of the chip.

9. A power supply circuit for a battery string voltage acquisition circuit (2) according to claim 8, characterized in that: The input voltage of the differential amplifier (21) is determined according to the negative power supply voltage (12), the voltage of the reference pin and the gain configuration.

10. A power supply circuit for a battery string voltage acquisition circuit (2) according to claim 9, characterized in that: The gain configuration of the chip is determined according to the resistance configuration of the chip.

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