Battery capacity detection circuit

Abstract

The present application relates to a battery capacity detection circuit. The battery capacity detection circuit can detect the output current of the battery to be detected through the detection circuit, and convert the output current into an output voltage and send it to the voltage control circuit. The voltage control circuit receives the output voltage and determines whether the output voltage is less than the preset voltage. If the output voltage is less than the preset voltage, a boost control signal is generated and sent to the boost circuit. The boost circuit increases the output voltage of the battery to be detected according to the boost control signal to keep the output current of the battery to be detected constant. The capacity measurement circuit calculates the discharge time of the battery to be detected, and calculates the capacity of the battery to be detected based on the output current and the discharge time. The battery capacity detection circuit provided in the present application can realize the direct measurement of the chemical energy of the battery. At the same time, the voltage control circuit has a wide adaptability range for the input voltage and a strong control capability for the discharge current, which can adapt to various battery discharge requirements.

Description

Technical Field

[0001] The present application relates to the technical field of battery capacity detection, and in particular to a battery capacity detection circuit. Background Art

[0002] As the operation time of permanent magnetic circuit breakers increases, the capacity of the batteries in the permanent magnetic circuit breakers will inevitably decay or the battery will be insufficient after a power outage, which will cause the permanent magnetic circuit breakers to fail to operate. At the same time, since the battery can only be inspected from the outside, it is difficult to predict the battery status in advance. Capacity detection is the best method to determine the discharge capacity and life of the battery. In the existing technology, the battery discharge detection is usually carried out by the verification discharge method, conductivity method, internal resistance method and ampere-hour meter method.

[0003] Among them, the verification discharge method uses a constant current to completely discharge the battery, which is the most direct, accurate and reliable method for detecting the battery capacity. Existing verification discharge equipment uses a variable resistor and a step-down circuit for discharge, which requires manual adjustment of the resistance, has the problems of poor control accuracy and a small scope of application. Summary of the invention

[0004] Based on this, it is necessary to provide a battery capacity detection circuit to address the problems of poor control accuracy and small application range of existing discharge verification equipment.

[0005] The present application provides a battery capacity detection circuit, comprising:

[0006] A boost circuit, a first end of which is electrically connected to the positive electrode of the battery to be tested, and is used to increase the output voltage of the battery to be tested;

[0007] a detection circuit, a first end of which is electrically connected to the second end of the boost circuit, and a second end of which is electrically connected to the negative electrode of the battery to be detected, for detecting the output current of the battery to be detected and converting the output current into an output voltage;

[0008] a voltage control circuit, whose input end is electrically connected to the third end of the detection circuit, and whose first output end is electrically connected to the third end of the boost circuit, wherein the voltage control circuit is used to receive the output voltage and determine whether the output voltage is less than a preset voltage, and if the output voltage is less than the preset voltage, generate a boost control signal and send it to the boost circuit, wherein the boost circuit increases the output voltage of the battery to be detected according to the boost control signal, so as to keep the output current of the battery to be detected constant; and

[0009] The capacity measurement circuit has an input terminal electrically connected to the second output terminal of the voltage control circuit, and is used to calculate the discharge time of the battery to be detected, and calculate the capacity of the battery to be detected according to the output current and the discharge time.

[0010] In one embodiment, the boost circuit comprises:

[0011] an inductor, a first end of which forms a first end of the boost circuit;

[0012] A switch tube, a first end of which is electrically connected to the second end of the inductor, a second end of which serves as the second end of the boost circuit, and a third end of which serves as the third end of the boost circuit;

[0013] a first diode, a first end of which is electrically connected to the second end of the inductor;

[0014] a first capacitor, a first end of which is electrically connected to the second end of the first diode, and a second end of which is electrically connected to the second end of the switch tube; and

[0015] A first resistor is connected in parallel with the first capacitor.

[0016] In one embodiment, the boost circuit further includes:

[0017] The voltage absorption branch is connected in parallel to the first end and the second end of the switch tube, and is used to absorb the voltage spike generated when the switch tube is disconnected.

[0018] In one embodiment, the voltage absorption branch includes:

[0019] A second diode, an input end of which is electrically connected to the first end of the switch tube;

[0020] a second capacitor, a first end of which is electrically connected to the output end of the second diode, and a second end of which is electrically connected to the second end of the switch tube; and

[0021] A second resistor is connected in parallel with the second diode.

[0022] In one embodiment, the detection circuit includes a Hall device, a first end of the Hall device is electrically connected to the second end of the boost circuit, a second end of the Hall device is electrically connected to the negative electrode of the battery to be detected, and a third end of the Hall device is electrically connected to the input end of the voltage control circuit.

[0023] In one embodiment, the voltage control circuit includes:

[0024] a filter branch, whose input end is electrically connected to the third end of the detection circuit, and is used to filter the output voltage;

[0025] a voltage comparison branch, whose input end is electrically connected to the first output end of the filtering branch, and is used to compare whether the output voltage is less than the preset voltage;

[0026] a control branch, whose input end is electrically connected to the output end of the voltage comparison branch, and is used to output a pulse width modulation signal when the output voltage is less than the preset voltage; and

[0027] A driving branch, whose first input end is electrically connected to the control branch and whose output end is electrically connected to the third end of the boost circuit, is used to generate the boost control signal according to the pulse width modulation signal and send it to the boost circuit.

[0028] In one embodiment, the voltage control circuit further includes:

[0029] The amplifying branch has an input end electrically connected to the first output end of the filtering branch, and an output end electrically connected to the input end of the voltage comparing branch, and is used to amplify the output voltage.

[0030] In one embodiment, the capacity measurement circuit includes:

[0031] a sampling branch, whose input end is electrically connected to the second output end of the filtering branch, and is used to convert the output voltage from an analog signal into a digital signal; and

[0032] A capacity calculation branch, whose input end is electrically connected to the output end of the sampling branch, is used to calculate the discharge time of the battery to be detected, and calculate the capacity of the battery to be detected according to the output voltage, the resistance value of the first resistor and the discharge time.

[0033] In one embodiment, the battery capacity detection circuit further includes an isolation circuit, a first end of which is electrically connected to the second input end of the driving branch, for isolating the influence of other circuits on the driving branch.

[0034] In one embodiment, the control branch includes:

[0035] a proportional-integral controller, whose input terminal is electrically connected to the output terminal of the voltage comparison branch; and

[0036] A pulse width modulation controller has an input end electrically connected to the output end of the proportional integral controller, and an output end electrically connected to the first input end of the driving branch.

[0037] In one embodiment, the battery capacity detection circuit further includes a display circuit, an input end of which is electrically connected to an output end of the capacity measurement circuit, and is used to display the capacity of the battery to be detected.

[0038] The battery capacity detection circuit provided in the above embodiment can detect the output current of the battery to be detected through the detection circuit, and convert the output current into an output voltage and send it to the voltage control circuit. The voltage control circuit receives the output voltage and determines whether the output voltage is less than the preset voltage. If the output voltage is less than the preset voltage, a boost control signal is generated and sent to the boost circuit. The boost circuit increases the output voltage of the battery to be detected according to the boost control signal to keep the output current of the battery to be detected constant. The capacity measurement circuit calculates the discharge time of the battery to be detected, and calculates the capacity of the battery to be detected based on the output current and the discharge time. The battery capacity detection circuit provided in the present application can realize the direct measurement of the chemical energy of the battery, and at the same time, the voltage control circuit can have a wide adaptability range to the input voltage and a strong control ability to the discharge current, which can adapt to various battery discharge requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A battery capacity detection circuit is provided in an embodiment of the present application.

[0040] Description of Figure Numbers

[0041] 100 Battery capacity detection circuit

[0042] 10 Boost Circuit

[0043] 110 Inductor

[0044] 120 Switching tube

[0045] 130 First diode

[0046] 140 First Capacitor

[0047] 150 First resistor

[0048] 160 Voltage absorption branch

[0049] 161 Second diode

[0050] 162 Second capacitor

[0051] 163 Second resistor

[0052] 20 Detection circuit

[0053] 210 Hall Device

[0054] 30 Voltage Control Circuit

[0055] 310 filter branch

[0056] 320 Voltage comparison branch

[0057] 330 Control branch

[0058] 331 Proportional Integral Controller

[0059] 332 Pulse Width Modulation Controller

[0060] 340 drive branch

[0061] 350 Amplification Branch

[0062] 40 Capacitance measurement circuit

[0063] 410 Sampling branch

[0064] 420 Capacity calculation branch

[0065] 50 Isolation circuit

[0066] 60 Display Circuit DETAILED DESCRIPTION

[0067] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific implementation disclosed below.

[0068] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be an intermediate element at the same time.

[0069] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0070] See also Figure 1The present application provides a battery capacity detection circuit 100. The battery capacity detection circuit 100 includes a boost circuit 10, a detection circuit 20, a voltage control circuit 30 and a capacity measurement circuit 40. The boost circuit 10, whose first end is electrically connected to the positive electrode of the battery to be detected, is used to increase the output voltage of the battery to be detected. The detection circuit 20, whose first end is electrically connected to the second end of the boost circuit 10, and whose second end is electrically connected to the negative electrode of the battery to be detected, is used to detect the output current of the battery to be detected and convert the output current into an output voltage. The voltage control circuit 30, whose input end is electrically connected to the third end of the detection circuit 20, and whose first output end is electrically connected to the third end of the boost circuit 10, is used to receive the output voltage and determine whether the output voltage is less than a preset voltage. If the output voltage is less than the preset voltage, a boost control signal is generated and sent to the boost circuit 10. The boost circuit 10 increases the output voltage of the battery to be detected according to the boost control signal to keep the output current of the battery to be detected constant. The capacity measurement circuit 40 has an input terminal electrically connected to the second output terminal of the voltage control circuit 30 and is used to calculate the discharge time of the battery to be detected and calculate the capacity of the battery to be detected according to the output current and the discharge time.

[0071] The battery capacity detection circuit 100 provided in the present application can detect the output current of the battery to be detected through the detection circuit 20, and convert the output current into an output voltage and send it to the voltage control circuit 30. The voltage control circuit 30 receives the output voltage and determines whether the output voltage is less than the preset voltage. If the output voltage is less than the preset voltage, a boost control signal is generated and sent to the boost circuit 10. The boost circuit 10 increases the output voltage of the battery to be detected according to the boost control signal to keep the output current of the battery to be detected constant. The capacity measurement circuit 40 calculates the discharge time of the battery to be detected, and calculates the capacity of the battery to be detected based on the output current and the discharge time. The battery capacity detection circuit 100 provided in the present application can realize the direct measurement of the chemical energy of the battery, and at the same time, the voltage control circuit 30 has a wide adaptability range for the input voltage and a strong control capability for the discharge current, which can adapt to various battery discharge requirements.

[0072] In one embodiment, the boost circuit 10 includes an inductor 110, a switch tube 120, a first diode 130, a first capacitor 140 and a first resistor 150. The inductor 110, whose first end forms the first end of the boost circuit 10. The switch tube 120, whose first end is electrically connected to the second end of the inductor 110, whose second end serves as the second end of the boost circuit 10, and whose third end serves as the third end of the boost circuit 10. The first diode 130, whose first end is electrically connected to the second end of the inductor 110. The first capacitor 140, whose first end is electrically connected to the second end of the first diode 130, and whose second end is electrically connected to the second end of the switch tube 120. The first resistor 150 is connected in parallel with the first capacitor 140. It is understandable that the operating frequency of the boost circuit 10 can be 50HZ, and the main power device switch tube 120 can be a metal oxide semiconductor (Metal-Oxide-Semiconductor, MOS) tube or an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor, IGBT), and the specific type can be selected according to actual needs. The boost circuit 10 can be a boost chopper circuit. It is understandable that as the capacity of the battery to be detected decreases during the amplification process, the output voltage continues to decrease. By setting the boost circuit 10, the output voltage of the battery to be detected can be controlled to remain constant according to the relationship between the output voltage of the battery to be detected and the preset voltage, so as to calculate the capacity of the battery to be detected according to the stable output current and time. It is understandable that the preset voltage can be the size of the output voltage of the battery to be detected during the initial discharge.

[0073] In one embodiment, the boost circuit 10 further includes a voltage absorption branch 160. The voltage absorption branch 160 is connected in parallel to the first end and the second end of the switch tube 120, and is used to absorb the voltage spike generated when the switch tube 120 is disconnected. In one embodiment, the voltage absorption branch 160 includes a second diode 161, a second capacitor 162, and a second resistor 163. The second diode 161, whose input end is electrically connected to the first end of the switch tube 120. The second capacitor 162, whose first end is electrically connected to the output end of the second diode 161, and whose second end is electrically connected to the second end of the switch tube 120. The second resistor 163 is connected in parallel with the second diode 161. It can be understood that when the main power device in the boost circuit 10 is the switch tube 120, the switch tube will generate a voltage spike at the C pole when it is disconnected, and the voltage spike will cause the output to increase instantly, so that the current will also increase instantly. Therefore, this process cannot ensure that the battery to be detected maintains a constant current output, which in turn causes a deviation in the battery capacity detection. Therefore, by providing the voltage absorption branch 160 , the accuracy of the battery capacity detection circuit 100 in detecting the battery capacity can be improved.

[0074] In one embodiment, the detection circuit 20 includes a Hall device 210, a first end of the Hall device 210 is electrically connected to the second end of the boost circuit 10, a second end thereof is electrically connected to the negative electrode of the battery to be detected, and a third end thereof is electrically connected to the input end of the voltage control circuit 30. In one embodiment, the Hall device 210 may be a Hall sensor, and the primary rated input current of the Hall sensor may be 60A, and the secondary rated output voltage may be 5V. The selection of the primary rated input current and the secondary rated output voltage of the above-mentioned model can ensure that the Hall sensor is suitable for the detection of batteries of different capacities and ensure that the Hall sensor will not be burned.

[0075] In one embodiment, the voltage control circuit 30 includes a filter branch 310, a voltage comparison branch 320, a control branch 330 and a drive branch 340. The filter branch 310, whose input end is electrically connected to the third end of the detection circuit 20, is used to filter the output voltage. The voltage comparison branch 320, whose input end is electrically connected to the first output end of the filter branch 310, is used to compare whether the output voltage is less than a preset voltage. The control branch 330, whose input end is electrically connected to the output end of the voltage comparison branch 320, is used to output a pulse width modulation signal when the output voltage is less than the preset voltage. The drive branch 340, whose first input end is electrically connected to the control branch 330, and whose output end is electrically connected to the third end of the boost circuit 10, is used to generate a boost control signal according to the pulse width modulation signal and send it to the boost circuit 10. In one embodiment, the voltage control circuit 30 further includes an amplifying branch 350 , whose input end is electrically connected to the first output end of the filtering branch 310 , and whose output end is electrically connected to the input end of the voltage comparison branch 320 , for amplifying the output voltage.

[0076] The voltage control circuit 30 may include a filter branch 310 and an amplifier branch 350. This is because the detected current signal is a non-constant value and contains the switching operating frequency interference. Therefore, it is necessary to amplify and filter the voltage signal output by the detection circuit 20. The amplified and filtered circuit can be input into the voltage comparison branch 320, and the voltage comparison branch 320 can compare the output voltage with the preset voltage, that is, the reference given voltage. The control branch 330 can control the pulse width modulation controller 332 to output the corresponding duty cycle according to the difference between the output voltage and the preset voltage, that is, the error between the two, after closed-loop control and adjustment using the proportional integral controller 331, and the driving branch 340 drives the boost circuit 10, thereby increasing the voltage across the first resistor 150, and then adjusting the discharge current of the battery to be detected to keep it constant. Among them, the bias voltage can ensure that the pulse width modulation controller 332 has a stable initial state when there is no reference given signal. It can be understood that by setting the control branch 330, the battery capacity detection circuit 100 can have a wider adaptability range for the input voltage, have a stronger control capability for the discharge current, and can adapt to the discharge requirements of different batteries to be detected.

[0077] In one embodiment, the capacity measurement circuit 40 includes a sampling branch 410 and a capacity calculation branch 420. The sampling branch 410, whose input end is electrically connected to the second output end of the filter branch 310, is used to convert the output voltage from an analog signal to a digital signal. The capacity calculation branch 420, whose input end is electrically connected to the output end of the sampling branch 410, is used to calculate the discharge time of the battery to be detected, and calculate the capacity of the battery to be detected according to the output voltage, the resistance value of the first resistor 150 and the discharge time. It can be understood that the voltage signal output by the detection circuit 20 is amplified and filtered by the filter branch 310 and the amplifier branch 350. The filtered voltage value can be sampled by the sampling branch 410, that is, the analog signal is converted into a digital signal and then sent to the capacity calculation branch 420. In one embodiment, the capacity calculation branch 420 can include a single-chip microcomputer, which can calculate the stable output current according to Ohm's law based on the stable output voltage collected by the detection circuit 20 and the known resistance value of the first resistor 150 as a load in the boost circuit 10. The single chip microcomputer can also obtain the capacity of the battery to be tested by calculating the product of the output current and the discharge time according to the output current and the calculated discharge time of the battery.

[0078] In one embodiment, the battery capacity detection circuit further includes an isolation circuit 50, a first end of which is electrically connected to the second input end of the driving branch 340, for isolating the influence of other circuits on the driving branch 340. It can be understood that the isolation circuit 50 can prevent other circuits from affecting the driving branch 340, thereby ensuring the stable operation of the entire battery capacity detection circuit 100.

[0079] In one embodiment, the control branch 330 includes a proportional integral controller 331 and a pulse width modulation controller 332. The proportional integral controller 331 has an input end electrically connected to the output end of the voltage comparison branch 320. The pulse width modulation controller 332 has an input end electrically connected to the output end of the proportional integral controller 331, and an output end electrically connected to the first input end of the driving branch 340. The battery capacity detection circuit 100 provided in the present application is based on the boost circuit 10 as the main circuit, and the control branch 330 using the pulse width modulation technology and the proportional integral closed-loop control technology can meet the requirements of various types of battery capacity detection to be detected. In this embodiment, the Hall device can detect the discharge current signal of the battery to be detected, and compare it with the reference given voltage after amplification and filtering. According to the error between the two, the proportional integral controller 331 is used for closed-loop control and adjustment, and the pulse width modulation controller 332 is controlled to output the corresponding duty cycle, and the driving branch 340 drives the boost circuit 10, thereby increasing the voltage across the first resistor 150, and then keeping the discharge current of the battery to be detected constant.

[0080] In one embodiment, the battery capacity detection circuit further includes a display circuit 60, whose input end is electrically connected to the output end of the capacity measurement circuit 40, for displaying the capacity of the battery to be detected. It is understood that the final battery capacity information can be sent to the display circuit 60 via serial communication. The display circuit 60 may include a display screen, which can display the capacity of the battery to be detected, so as to facilitate the staff to check the capacity of the battery to be detected, so as to ensure the normal operation of the permanent magnetic circuit breaker.

[0081] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0082] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A battery capacity detection circuit, characterized in that: include: A boost circuit (10), a first end of which is electrically connected to the positive electrode of the battery to be tested, and is used to boost the output voltage of the battery to be tested; a detection circuit (20), a first end of which is electrically connected to the second end of the boost circuit (10), and a second end of which is electrically connected to the negative electrode of the battery to be detected, and is used to detect the output current of the battery to be detected and convert the output current into an output voltage; a voltage control circuit (30), wherein an input end thereof is electrically connected to a third end of the detection circuit (20), and a first output end thereof is electrically connected to a third end of the boost circuit (10); the voltage control circuit (30) is used to receive the output voltage and determine whether the output voltage is less than a preset voltage; if the output voltage is less than the preset voltage, a boost control signal is generated and sent to the boost circuit (10); the boost circuit (10) increases the output voltage of the battery to be detected according to the boost control signal, so that the output current of the battery to be detected remains constant; and a capacity measurement circuit (40), whose input end is electrically connected to the second output end of the voltage control circuit (30), and is used to calculate the discharge time of the battery to be detected, and calculate the capacity of the battery to be detected according to the output current and the discharge time; The boost circuit (10) comprises: an inductor (110), a first end of which forms the first end of the boost circuit (10); a switch tube (120), a first end of which is electrically connected to the second end of the inductor (110), a second end of which serves as the second end of the boost circuit (10), and a third end of which serves as the third end of the boost circuit (10); a first diode (130), a first end of which is electrically connected to the second end of the inductor (110); a first capacitor (140), a first end of which is electrically connected to the second end of the first diode (130), and a second end of which is electrically connected to the second end of the switch tube (120); and a first resistor (150), connected in parallel with the first capacitor (140); The voltage control circuit (30) comprises: a filter branch (310), whose input end is electrically connected to the third end of the detection circuit (20) and is used to filter the output voltage; a voltage comparison branch (320), whose input end is electrically connected to the first output end of the filter branch (310) and is used to compare whether the output voltage is less than the preset voltage; a control branch (330), whose input end is electrically connected to the output end of the voltage comparison branch (320) and is used to output a pulse width modulation signal when the output voltage is less than the preset voltage; and a drive branch (340), whose first input end is electrically connected to the control branch (330) and whose output end is electrically connected to the third end of the boost circuit (10) and is used to generate the boost control signal according to the pulse width modulation signal and send it to the boost circuit (10).

2. The battery capacity detection circuit according to claim 1, characterized in that: The boost circuit (10) further includes: The voltage absorption branch (160) is connected in parallel to the first end and the second end of the switch tube (120), and is used to absorb a voltage spike generated when the switch tube (120) is disconnected.

3. The battery capacity detection circuit according to claim 2, characterized in that: The voltage absorption branch (160) comprises: A second diode (161), an input end of which is electrically connected to the first end of the switch tube (120); a second capacitor (162), a first end of which is electrically connected to the output end of the second diode (161), and a second end of which is electrically connected to the second end of the switch tube (120); and The second resistor (163) is connected in parallel with the second diode (161).

4. The battery capacity detection circuit according to claim 1, characterized in that: The detection circuit (20) comprises a Hall device (210), a first end of the Hall device (210) being electrically connected to a second end of the boost circuit (10), a second end of the Hall device (210) being electrically connected to a negative electrode of the battery to be detected, and a third end of the Hall device (210) being electrically connected to an input end of the voltage control circuit (30).

5. The battery capacity detection circuit according to claim 4, characterized in that: The Hall device (210) is a Hall sensor, the primary rated input current of the Hall sensor is 60A, and the secondary rated output voltage of the Hall sensor is 5V.

6. The battery capacity detection circuit according to claim 1, characterized in that: The voltage control circuit (30) further includes: An amplifying branch (350) has an input end electrically connected to the first output end of the filtering branch (310), and an output end electrically connected to the input end of the voltage comparison branch (320), and is used to amplify the output voltage.

7. The battery capacity detection circuit according to claim 1, characterized in that: The capacity measurement circuit (40) comprises: a sampling branch (410), whose input end is electrically connected to the second output end of the filtering branch (310), and is used to convert the output voltage from an analog signal into a digital signal; and A capacity calculation branch (420), whose input end is electrically connected to the output end of the sampling branch (410), is used to calculate the discharge time of the battery to be detected, and calculate the capacity of the battery to be detected based on the output voltage, the resistance value of the first resistor (150) and the discharge time.

8. The battery capacity detection circuit according to claim 1, characterized in that: It also includes an isolation circuit (50), a first end of which is electrically connected to the second input end of the driving branch (340) and is used to isolate the influence of other circuits on the driving branch (340).

9. The battery capacity detection circuit according to claim 1, characterized in that: The control branch (330) comprises: A proportional-integral controller (331), an input end of which is electrically connected to the output end of the voltage comparison branch (320); and A pulse width modulation controller (332) has an input end electrically connected to the output end of the proportional integral controller (331), and an output end electrically connected to the first input end of the driving branch (340).

10. The battery capacity detection circuit according to claim 1, characterized in that: It also includes a display circuit (60), whose input end is electrically connected to the output end of the capacity measurement circuit (40) and is used to display the capacity of the battery to be tested.

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