A cell voltage differential sampling circuit

Abstract

This invention discloses a battery cell voltage differential sampling circuit, comprising a front-end integrated operational amplifier, a back-end integrated operational amplifier, a first auxiliary reference voltage input terminal, a second auxiliary reference voltage input terminal, a positive terminal of the battery cell, and a negative terminal of the battery cell. The first auxiliary reference voltage input terminal is used to receive a positive voltage, and the second auxiliary reference voltage input terminal is used to receive a negative voltage. The voltage signals from the first auxiliary reference voltage input terminal and the negative terminal of the battery cell are both transmitted to the inverting input of the front-end integrated operational amplifier, and the voltage signals from the second auxiliary reference voltage input terminal and the positive terminal of the battery cell are both transmitted to the non-inverting input of the front-end integrated operational amplifier. The voltage signal from the output terminal of the front-end integrated operational amplifier is transmitted to the non-inverting input of the back-end integrated operational amplifier, and the inverting input of the back-end integrated operational amplifier is connected to its output terminal. This invention helps to quickly identify fault signals such as poor voltage sampling contact or detachment during battery cell formation and capacity testing, thereby improving the safety of equipment use.

Description

Technical Field

[0001] This invention relates to differential sampling circuits, and more particularly to a battery cell voltage differential sampling circuit. Background Technology

[0002] Differential amplifier circuits utilize the symmetry of circuit parameters and negative feedback to effectively stabilize the quiescent operating point. They are characterized by amplifying differential signals and suppressing common-mode signals, and are widely used in the input stages of directly coupled circuits and measurement circuits. Differential amplifier circuits have two basic input states: differential and common-mode. When an external signal is applied between the two input terminals, making the two input signals Vi1 and Vi2 equal in magnitude and opposite in polarity, it is called a differential input signal. When an external signal is applied between the two input terminals and ground, making Vi1 and Vi2 equal in magnitude and same in polarity, it is called a common-mode input signal.

[0003] In practical applications, an integrated operational amplifier U1 and some peripherals are typically used to form a conventional differential amplifier circuit. Please refer to the instruction manual for details. Figure 1 The negative feedback differential amplifier circuit, composed of an integrated operational amplifier U1 and some external resistors, can be analyzed using the concepts of "virtual open circuit" and "virtual short circuit." Virtual short circuit refers to the situation where, under ideal conditions, the potentials at the two input terminals of the integrated operational amplifier are equal, as if the two input terminals were short-circuited together (i.e., U1). N =U P However, there is no actual short circuit, which is called a "virtual short." A necessary condition for a virtual short is the introduction of deep negative feedback in the integrated operational amplifier. A virtual short refers to the fact that, ideally, the current flowing into the input of the integrated operational amplifier is zero (i.e., I0). + =I - =0A). This is because the input resistance of an ideal operational amplifier is infinitely large, as if there were an open circuit between the two input terminals of the op-amp. But in reality, there is no open circuit, which is called "virtual open circuit".

[0004] according to Figure 1 The formula for the output voltage Vout1 of a conventional differential amplifier circuit is derived as follows:

[0005] Based on the concept of "virtual shortness", U is obtained. P =U N (1);

[0006] The voltage at the positive input terminal of the integrated operational amplifier U1 is obtained using the "resistor voltage divider principle":

[0007]

[0008] Based on the concept of "virtual disconnection" and equivalent feedback loop, we get:

[0009] I2 = If;

[0010]

[0011] Based on the combination of formulas (1), (2), and (3), the output voltage magnitude Vout1 is derived as follows:

[0012]

[0013] Generally, if we take R1 = R2 and R3 = R4, then:

[0014]

[0015] In practical applications: The back end of battery cell production needs to be tested for capacity, that is, the battery cells need to be charged and discharged. The battery cell voltage is the most important indicator for measuring the charge and discharge cutoff conditions, and its sampling method is particularly important. Usually, a four-wire sampling method is used, that is, the battery cell voltage and the current line voltage are sampled separately. The voltage range of the battery cell is usually 0-4.3V. The voltage sampling is a differential sampling circuit. In order to prevent the lower-level machine from recognizing the reverse connection of the battery cell, the voltage range of differential sampling is usually -5V to 5V.

[0016] A standard differential amplifier circuit for sampling battery cell voltage is shown in the attached manual. Figure 2 As shown. According to the "superposition principle", we get

[0017]

[0018] Based on the characteristics of a voltage follower, we have:

[0019] U P1 =Vout2 (6);

[0020] Based on the combination of formulas (4), (5), and (6), the output voltage magnitude Vout2 is derived as follows:

[0021]

[0022] To ensure the ADC converter can sample voltage, the value input to the MCU chip is generally positive. To sample a cell voltage within the range of -5V to 5V, the following must be met: Only under certain conditions can we guarantee that a positive value is sampled to identify the actual sampled value.

[0023] A schematic diagram of the connection between probe voltage sampling and power cabinet system sampling (i.e., voltage and current line voltage sampling) is attached. Figure 3As shown, I+ and I- are the current lines for charging and discharging the battery cell, V+ and V- are the main voltage samples of the battery cell, and DV+ and DV- are the voltage samples of the current lines. In actual battery cell production testing, loose sampling probes on the battery cell voltage and current lines can cause sampling deviations. Especially when the negative electrode sampling probe has poor contact or the sampling line falls off, the characteristics of the conventional voltage differential amplification sampling circuit will lead to the sampled value being lower than the actual voltage value of the battery cell. During subsequent charging, this can cause overcharging of the battery cell, resulting in bulging, explosion, or even fire and other serious safety accidents.

[0024] Specifically, the analysis of the normal connection of the positive terminal and the negative terminal of the battery cell is as follows:

[0025] When the negative sampling probe of the battery cell has poor contact or the sampling line falls off (i.e., Vi1 is disconnected), the negative terminal of the battery cell will be connected to the power ground PGND through the negative terminal of the current line (i.e., I-) and the digital ground GND through the 0R resistor, ensuring that the input voltage at point Vi2 is still equal to the battery cell voltage (i.e., Vi2 = battery voltage, Vi1 = 0V). Because the input voltage of Vi1 is disconnected, the conventional differential amplifier circuit composed of the integrated operational amplifier U1 becomes a voltage follower (i.e., Up = Vout1). The battery cell sampling circuit when the negative terminal Vi1 is disconnected is shown in the attached diagram. Figure 4 As shown.

[0026] according to Figure 4 The formula for the output voltage Vout2 of the battery cell sampling circuit when the negative terminal Vi1 of the battery cell is disconnected is derived as follows:

[0027] According to the "resistance voltage divider principle":

[0028] Based on the concept of "virtual short" and the characteristics of "voltage follower", we get:

[0029]

[0030] When the negative terminal Vi1 of the battery cell is disconnected from the positive terminal Vi2 and the input is normal, according to the "superposition principle" and the characteristics of the "voltage follower", the output voltage Vout2 is:

[0031]

[0032] When the negative terminal Vi1 of the battery cell is disconnected and the positive terminal Vi2 is input normally, the simulation test results of the battery cell voltage sampling circuit using Multisim are shown in the attached figure. Figure 5 As shown.

[0033] Furthermore, the analysis of the normal situation where both the positive and negative terminals of the battery cell are connected is as follows:

[0034] When the positive and negative electrodes of the battery cell (Vi 1 and Vi2) are both properly connected, according to the "superposition principle" and the characteristics of the "voltage follower", referring to Figure 1 the derivation process of the formula, the output voltage Vout2 is obtained as follows:

[0035]

[0036] When the positive and negative electrodes of the battery cell (Vi 1 and Vi2) are both properly connected, the simulation test results of the battery cell voltage sampling circuit using Multisim are as shown in the appendix Figure 6 as follows.

[0037] Since R1 = R2, R3 = R4, and Vi 1 = 0, then Therefore, Vout2 < Vout3. That is, when the sampling probe of the negative electrode of the battery cell has poor contact, the sampling value Vout2 is lower than the sampling value when the positive and negative electrodes of the battery cell are properly connected. Through the simulation test using Multisim (as shown in the above Figure 5 and Figure 6 figures), the situation where the sampling value is low when the sampling line of the negative electrode of the battery cell is broken can be visually observed. Summary of the Invention

[0038] The technical problem to be solved by the present invention is to provide a battery cell voltage differential sampling circuit that helps to quickly identify fault signals such as poor contact or detachment of voltage sampling during the formation and grading of battery cells, thereby improving the safety of equipment use, in view of the deficiencies of the prior art.

[0039] To solve the above technical problem, the present invention adopts the following technical solutions.

[0040] A battery cell voltage differential sampling circuit includes a front-end integrated operational amplifier, a rear-end integrated operational amplifier, a first auxiliary reference voltage input terminal, a second auxiliary reference voltage input terminal, a positive electrode of the battery cell, and a negative electrode of the battery cell. The first auxiliary reference voltage input terminal is used to access a positive voltage, and the second auxiliary reference voltage input terminal is used to access a negative voltage. The voltage signals of the first auxiliary reference voltage input terminal and the negative electrode of the battery cell are both transmitted to the inverting terminal of the front-end integrated operational amplifier, and the voltage signals of the second auxiliary reference voltage input terminal and the positive electrode of the battery cell are both transmitted to the non-inverting terminal of the front-end integrated operational amplifier. The voltage signal at the output terminal of the front-end integrated operational amplifier is transmitted to the non-inverting terminal of the rear-end integrated operational amplifier. The inverting terminal and the output terminal of the rear-end integrated operational amplifier are connected to form a voltage follower circuit, and the output terminal of the rear-end integrated operational amplifier serves as the output terminal of the battery cell voltage differential sampling circuit.

[0041] Preferably, a first resistor is connected between the negative terminal of the battery cell and the inverting input of the front-end integrated operational amplifier, and a second resistor is connected between the positive terminal of the battery cell and the non-inverting input of the front-end integrated operational amplifier.

[0042] Preferably, a third resistor is connected between the first auxiliary reference voltage input terminal and the negative terminal of the battery cell, and a fourth resistor is connected between the second auxiliary reference voltage input terminal and the positive terminal of the battery cell.

[0043] Preferably, a fifth resistor is connected between the non-inverting input of the front-end integrated operational amplifier and ground.

[0044] Preferably, a sixth resistor is connected between the inverting input and the output input of the front-end integrated operational amplifier.

[0045] Preferably, a seventh resistor is connected between the output terminal of the front-end integrated operational amplifier and the non-inverting terminal of the back-end integrated operational amplifier.

[0046] Preferably, an eighth resistor is included, one end of which is connected to the non-inverting input of the back-end integrated operational amplifier, and the other end of which serves as a reference voltage terminal and is used to connect to a reference voltage.

[0047] The differential voltage sampling circuit for battery cells disclosed in this invention offers several advantages over existing technologies. Firstly, it utilizes a conventional differential amplifier circuit that, when malfunctioning, achieves a negative output voltage by inputting a certain negative voltage. This, combined with software-triggered reverse connection protection, proactively mitigates risks and prevents serious safety incidents such as cell bulging, explosion, or even fire caused by overcharging. Secondly, compared to existing technologies, this invention can quickly identify conditions such as poor voltage sampling contact or detached sampling lines during cell formation and capacity testing, facilitating the effective control of potential safety hazards in advance. Attached Figure Description

[0048] Figure 1 This is a typical differential amplifier circuit diagram;

[0049] Figure 2 A typical differential amplifier circuit diagram for battery cell voltage sampling;

[0050] Figure 3 This is a schematic diagram showing the connection between probe voltage sampling and power cabinet system sampling.

[0051] Figure 4 This is a battery cell sampling circuit when the negative terminal Vi 1 of a conventional battery cell is disconnected.

[0052] Figure 5 This is a schematic diagram of a conventional battery cell voltage sampling circuit simulated using Multisim simulation when the negative terminal Vi1 of the battery cell is disconnected.

[0053] Figure 6 This is a schematic diagram of using Multisim simulation to test the cell voltage sampling circuit when both the positive and negative terminals of the cell are properly connected.

[0054] Figure 7 This is a circuit diagram of the improved battery cell voltage sampling differential amplifier of the present invention;

[0055] Figure 8 This is a schematic diagram of the current flow direction in the improved cell voltage sampling differential amplifier circuit of the present invention;

[0056] Figure 9 A schematic diagram of the simulation test of the battery cell voltage sampling circuit of this invention using Multisim simulation when both the positive and negative terminals of the battery cell are properly connected.

[0057] Figure 10 The diagram shows the cell voltage sampling circuit of this invention when neither the positive nor negative terminal of the cell is connected, or when the negative terminal of the cell is disconnected and the positive terminal is connected.

[0058] Figure 11 A schematic diagram of the simulation test of the cell voltage sampling circuit of the present invention using Multisim simulation when neither the positive nor negative terminals of the cell are connected.

[0059] Figure 12 A schematic diagram of the simulation test of the cell voltage sampling circuit of the present invention using Multisim simulation with the positive terminal of the cell disconnected and the negative terminal connected.

[0060] Figure 13 Diagram of a battery cell voltage sampling circuit when the negative terminal of the battery cell is disconnected and the positive terminal is normally connected;

[0061] Figure 14 A schematic diagram of the simulation test of the cell voltage sampling circuit of the present invention using Multisim simulation when the negative terminal of the cell is disconnected and the positive terminal is connected;

[0062] Figure 15 This diagram illustrates the simulation test of the cell voltage sampling circuit using Multisim when the negative terminal of the cell is disconnected and the positive terminal is connected. Detailed Implementation

[0063] The present invention will now be described in more detail with reference to the accompanying drawings and embodiments.

[0064] This invention discloses a cell voltage differential sampling circuit; please refer to the appendix. Figure 7It includes a front-end integrated operational amplifier U1, a back-end integrated operational amplifier U2, a first auxiliary reference voltage input terminal Vin1_ref, a second auxiliary reference voltage input terminal Vin2_ref, a positive terminal Vin2 of the battery cell, and a negative terminal Vin1 of the battery cell. The first auxiliary reference voltage input terminal Vin1_ref is used to connect to a positive voltage, and the second auxiliary reference voltage input terminal Vin2_ref is used to connect to a negative voltage. The voltage signals of the first auxiliary reference voltage input terminal Vin1_ref and the negative terminal Vin1 of the battery cell are both transmitted to the inverting input of the front-end integrated operational amplifier U1, and the voltage signals of the second auxiliary reference voltage input terminal Vin2_ref and the positive terminal Vin2 of the battery cell are both transmitted to the non-inverting input of the front-end integrated operational amplifier U1. The voltage signal at the output terminal of the front-end integrated operational amplifier U1 is transmitted to the non-inverting input of the back-end integrated operational amplifier U2. The inverting input and the output terminal of the back-end integrated operational amplifier U2 are connected to form a voltage follower circuit. The output terminal of the back-end integrated operational amplifier U2 serves as the output terminal of the battery cell voltage differential sampling circuit.

[0065] Regarding the peripheral circuit structure of the above circuit, in this embodiment, a first resistor R1 is connected between the negative terminal Vin1 of the battery cell and the inverting terminal of the front-end integrated operational amplifier U1, and a second resistor R2 is connected between the positive terminal Vin2 of the battery cell and the non-inverting terminal of the front-end integrated operational amplifier U1. A third resistor R7 is connected between the first auxiliary reference voltage input terminal Vin1_ref and the negative terminal Vin1 of the battery cell, and a fourth resistor R8 is connected between the second auxiliary reference voltage input terminal Vin2_ref and the positive terminal Vin2 of the battery cell. A fifth resistor R4 is connected between the non-inverting terminal of the front-end integrated operational amplifier U1 and ground. A sixth resistor R3 is connected between the inverting terminal and the output terminal of the front-end integrated operational amplifier U1. A seventh resistor R5 is connected between the output terminal of the front-end integrated operational amplifier U1 and the non-inverting terminal of the back-end integrated operational amplifier U2. In addition, this embodiment also includes an eighth resistor R6, one end of which is connected to the non-inverting input of the back-end integrated operational amplifier U2, and the other end of which serves as a reference voltage terminal Vref and is used to connect to a reference voltage.

[0066] Please refer to the appendix for the principle of the battery cell voltage differential sampling circuit of this invention. Figure 8 In this embodiment, the battery cell is connected between the potentials of Vin2 and Vin1, with Vin2 being the positive terminal of the battery cell and Vin1 being the negative terminal. Vin2_ref and Vin1_ref are used to ensure that the output voltage Vout1 is negative when the battery cell is not connected. Generally, Vin2_ref is a negative voltage and Vin1_ref is a positive voltage.

[0067] Working principle: When no battery cell is connected between Vin2 and Vin1, Vin2_ref and Vin1_ref serve as the input terminals of the differential amplifier circuit. When the positive terminal Vi2 of the battery cell is connected between Vin2 and Vin1, and the negative terminal Vi1 is disconnected (where the disconnection of the negative terminal Vi1 will pass through the negative terminal PGND of the current line and be connected to GND through a 0R resistor to ensure that the potential at point Vi2 is equal to the battery cell voltage), Vin2 and Vin1_ref serve as the input terminals of the differential amplifier circuit. When the battery cell is normally connected between Vin2 and Vin1, Vin2 and Vin1 serve as the input terminals of the differential amplifier circuit. The subsequent integrated operational amplifier U2 forms a voltage follower to ensure that the ADC converter can sample a positive value. The battery cell voltage sampling is analyzed and explained in three cases.

[0068] Based on the above principles, this invention achieves a negative output voltage when a conventional differential amplifier circuit malfunctions by inputting a certain negative voltage. Combined with software-triggered reverse connection protection for the battery cell, this proactively controls risks and prevents serious safety accidents such as battery cell bulging, explosion, or even fire caused by overcharging. Compared to existing technologies, this invention can quickly identify conditions such as poor voltage sampling contact or detached sampling lines during battery cell formation and capacity testing, helping to effectively control potential safety hazards in advance.

[0069] The invention will now be further explained in relation to specific circuit states.

[0070] 1. Analysis of the normal situation where both the positive and negative terminals of the battery cell are connected:

[0071] When the battery cell is normally connected between Vin2 and Vin1, the improved battery cell voltage sampling differential amplifier circuit becomes the same as the conventional battery cell voltage sampling circuit, so the formula for the output voltage Vout2 is as follows:

[0072]

[0073] When both Vin2 and Vin1 cells are properly connected, Multisim simulation is used to test the cell voltage sampling circuit, as shown in the attached figure. Figure 9 As shown in the figure. According to the results of Multisim simulation, when the cell voltage is normally connected, the output voltage of the improved cell voltage sampling differential amplifier circuit is the same as that of the conventional cell voltage sampling differential amplifier circuit.

[0074] 2. Analysis of situations where neither the positive nor negative terminals of the battery cell are connected, or the negative terminal of the battery cell is disconnected and the positive terminal is connected:

[0075] When no battery cell is connected between Vin2 and Vin1 (or the negative terminal of the battery cell is normally connected to the positive terminal but disconnected), the structure of the improved battery cell voltage sampling circuit becomes as shown in the attached figure. Figure 10As shown, the formula for the output voltage Vout2 of the battery cell sampling differential amplifier circuit structure is derived as follows:

[0076] Using the concept of "virtual short" to obtain U P =U N (1);

[0077] The voltage at the positive input terminal of the integrated operational amplifier U1 is obtained using the "resistor voltage divider principle":

[0078]

[0079] Based on the concept of "virtual disconnection" and equivalent feedback loop, we get:

[0080] I2 = If;

[0081] Right now

[0082] Based on the combination of formulas (1), (2), and (3), the output voltage magnitude Vout1 is derived as follows:

[0083]

[0084] Generally, if we take R1 = R2, R3 = R4, and R7 = R8, then:

[0085]

[0086] According to the "superposition principle", we have:

[0087]

[0088] Based on the characteristics of a voltage follower, we have: U P1 =Vout2 (6);

[0089] Based on the combination of formulas (4), (5), and (6), the output voltage magnitude Vout2 is derived as follows:

[0090]

[0091] When no battery cell is connected between Vin2 and Vin1 (or the negative terminal of the battery cell is normally connected to the positive terminal and disconnected), Multisim simulation is used to simulate and test the battery cell voltage sampling circuit. The results are shown in the attached figure. Figure 11 As shown.

[0092] When Vin2 and Vin1 are connected to the negative terminal of the battery cell and then disconnected from the positive terminal, the battery cell voltage sampling circuit is simulated and tested using Multisim simulation, as shown in the attached figure. Figure 12As shown in the figure. According to the Multisim simulation results, the output voltage when the cell voltage is not connected is the same as the output voltage when the negative terminal of the cell voltage is connected to the positive terminal and disconnected. To ensure that a negative value is sampled when the input cell voltage is not connected or when the negative terminal of the cell voltage is normally connected to the positive terminal and disconnected, the condition (Vi2_ref - Vi1_ref) < 0V must be met. Generally, Vin_ref2 and Vin_ref1 are voltage values ​​with equal positive and negative values.

[0093] 3. Analysis of the situation where the negative terminal of the battery cell is disconnected and the positive terminal is normally connected:

[0094] When the negative terminal of the cell voltage connected between Vin2 and Vin1 is disconnected and the positive terminal is normally connected, the structure of the improved cell voltage sampling circuit becomes as shown in the attached figure. Figure 13 As shown. When the negative terminal of the main voltage sampling of the battery cell is disconnected, the current line through the probe will connect the negative power ground PGND to the digital ground GND through the 0R resistor. At this time, the potential of point Vi2 is equal to the battery cell voltage.

[0095] The formula for the output voltage Vout2 of the differential amplifier circuit for cell sampling at this time is derived as follows:

[0096] Based on the concept of "virtual shortness", U is obtained. P =U N (1);

[0097] The voltage at the positive input terminal of the integrated operational amplifier U1 is obtained using the "resistor voltage divider principle":

[0098]

[0099] Based on the concept of "virtual disconnection" and equivalent feedback loop, we get:

[0100] I2 = If;

[0101] Right now

[0102] Based on the combination of formulas (1), (2), and (3), the output voltage magnitude Vout1 is derived as follows:

[0103]

[0104] According to the "superposition principle", we have:

[0105]

[0106] Based on the characteristics of a voltage follower, we have: U P1 =Vout2 (6);

[0107] Based on the combination of formulas (4), (5), and (6), the output voltage magnitude Vout2 is derived as follows:

[0108]

[0109] When the negative terminal of the cell voltage between Vin2 and Vin1 is disconnected and the positive terminal is normally connected, Multisim simulation is used to simulate and test the cell voltage sampling circuit. The results are attached. Figure 14 As shown, to ensure the ADC converter can sample a voltage, the value must be positive. To sample a cell voltage within the range of -5V to 5V, the following must be met: Only under certain conditions can we guarantee that a positive value is sampled.

[0110] According to the Multisim simulation results, to ensure a negative value is sampled when the negative terminal of the battery cell is disconnected and the positive terminal is normally connected, the condition Vout1 < 0V must be met. Therefore, the resistance value of resistor R7 must be selected appropriately. To ensure Vout1 < 0V, the following conditions must be met: condition.

[0111] When the parameters of the improved cell voltage sampling differential amplifier circuit are R1=R2=100K, R3=R4=27K, R7=R8=150K, Vi2=5V, Vin1_ref=12V, then

[0112]

[0113]

[0114] Since Vout1 is negative when 1.1778V < 1.296V, it can be concluded that a negative value can be sampled when the cell voltage is equal to 5V, with the negative terminal disconnected and the positive terminal normally connected. Multisim simulation was used to test the cell voltage sampling circuit, and the results are attached. Figure 15 As shown.

[0115] According to the appendix Figure 14 and attached Figure 15 The results of Multisim simulation show that selecting appropriate R7 parameters is necessary to ensure that the sampling circuit outputs a negative voltage when the negative or positive terminal of the battery cell is disconnected at any stage. This, combined with software-triggered reverse connection protection, controls the risk in advance and prevents serious safety accidents such as battery cell bulging and explosion or even fire caused by overcharging.

[0116] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the technical scope of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cell voltage differential sampling circuit, characterized in that, This includes a front-end integrated operational amplifier (U1), a back-end integrated operational amplifier (U2), a first auxiliary reference voltage input terminal (Vin1_ref), a second auxiliary reference voltage input terminal (Vin2_ref), a positive terminal (Vin2) of the battery cell, and a negative terminal (Vin1) of the battery cell. The first auxiliary reference voltage input terminal (Vin1_ref) is used to connect a positive voltage, and the second auxiliary reference voltage input terminal (Vin2_ref) is used to connect a negative voltage. The voltage signals from the first auxiliary reference voltage input terminal (Vin1_ref) and the negative terminal (Vin1) of the battery cell are both transmitted to the... The inverting input of the front-end integrated operational amplifier (U1), the voltage signals of the second auxiliary reference voltage input (Vin2_ref) and the positive terminal (Vin2) of the battery cell are all transmitted to the non-inverting input of the front-end integrated operational amplifier (U1). The voltage signal at the output of the front-end integrated operational amplifier (U1) is transmitted to the non-inverting input of the back-end integrated operational amplifier (U2). The inverting input and output of the back-end integrated operational amplifier (U2) are connected to form a voltage follower circuit. The output of the back-end integrated operational amplifier (U2) serves as the output of the battery cell voltage differential sampling circuit. A first resistor (R1) is connected between the negative terminal (Vin1) of the battery cell and the inverting terminal of the front-end integrated operational amplifier (U1), and a second resistor (R2) is connected between the positive terminal (Vin2) of the battery cell and the non-inverting terminal of the front-end integrated operational amplifier (U1). A third resistor (R7) is connected between the first auxiliary reference voltage input terminal (Vin1_ref) and the negative terminal (Vin1) of the battery cell, and a fourth resistor (R8) is connected between the second auxiliary reference voltage input terminal (Vin2_ref) and the positive terminal (Vin2) of the battery cell. A fifth resistor (R4) is connected between the non-inverting input of the front-end integrated operational amplifier (U1) and ground.

2. The cell voltage differential sampling circuit as described in claim 1, characterized in that, A sixth resistor (R3) is connected between the inverting input and the output of the front-end integrated operational amplifier (U1).

3. The cell voltage differential sampling circuit as described in claim 1, characterized in that, A seventh resistor (R5) is connected between the output terminal of the front-end integrated operational amplifier (U1) and the non-inverting terminal of the back-end integrated operational amplifier (U2).

4. The cell voltage differential sampling circuit as described in claim 1, characterized in that, It includes an eighth resistor (R6), one end of which is connected to the non-inverting input of the back-end integrated operational amplifier (U2), and the other end of which serves as a reference voltage terminal (Vref) and is used to connect to a reference voltage.

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