Battery voltage detection circuit

Abstract

The utility model relates to the technical field of battery voltage detection, and discloses a battery voltage detection circuit. The circuit comprises a partial pressure detection module, an operational amplifier following module and a single-chip microcomputer. A first input end of the voltage division detection module is connected with a battery voltage end of a battery to be detected, a second input end of the voltage division detection module is connected with the single-chip microcomputer, an output end of the voltage division detection module is connected with a first end of the operational amplifier following module, and a second end of the operational amplifier following module is grounded. The third end of the operational amplifier following module is connected with the fourth end of the operational amplifier following module, and the fourth end of the operational amplifier following module is connected with the single-chip microcomputer. According to the utility model, the operational amplifier following module is added to the detection end of the voltage division detection module, the voltage consistency is ensured, the impedance detected before and after is not influenced, the voltage detection is carried out on the battery to be detected through the output level of the single-chip microcomputer according to the actual situation, and the single-chip microcomputer closes the battery voltage detection circuit when the detection is not needed, so that the power consumption is reduced to zero; and the storage time and the service life of a battery product are effectively prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of battery voltage detection, in particular to a battery voltage detection circuit. Background Art

[0002] At present, when batteries are used for charging on POS devices, fast charging of batteries greatly increases the safety test of the batteries themselves. Therefore, more designs are needed to ensure battery safety. A more effective way is to monitor the voltage, that is, through uninterrupted voltage monitoring, timely processing is carried out when abnormalities are found.

[0003] Due to the existence of the voltage detection circuit, the circuit power consumption of the POS device increases, causing the rapid overflow of battery energy, reducing the effective use of the battery and reducing its performance. More seriously, it may cause other safety problems due to over-discharge of the mobile battery. Utility Model Content

[0004] The main purpose of the utility model is to provide a battery voltage detection circuit, aiming to solve the problems of high power consumption of battery voltage detection technology of existing POS equipment, resulting in reduced battery efficiency and safety.

[0005] To achieve the above purpose, the utility model provides a battery voltage detection circuit, including: a voltage division detection module, an operational amplifier follower module and a single chip microcomputer; wherein,

[0006] The first input end of the voltage division detection module is connected to the battery voltage end of the battery to be tested, the second input end of the voltage division detection module is connected to the single-chip microcomputer, the output end of the voltage division detection module is connected to the first end of the operational amplifier follower module, the second end of the operational amplifier follower module is grounded, the third end of the operational amplifier follower module is connected to the fourth end of the operational amplifier follower module, and the fourth end of the operational amplifier follower module is connected to the single-chip microcomputer.

[0007] In some embodiments, the voltage division detection module includes: a switch unit and a resistor voltage division unit; wherein,

[0008] The input end of the switch unit is connected to the enable end of the single chip microcomputer and the battery voltage end respectively, the output end of the switch unit is connected to the resistor voltage divider unit, and the resistor voltage divider unit is also connected to the operational amplifier follower module.

[0009] In some embodiments, when detecting the voltage of the battery to be tested, the enable terminal of the microcontroller outputs a high level to the switch unit to turn on the battery voltage detection circuit; when stopping detecting the voltage of the battery to be tested, the enable terminal of the microcontroller is grounded and outputs a low level to the switch unit to turn off the switch unit and the resistor divider unit.

[0010] In some embodiments, the switch unit includes: a first MOS tube and a second MOS tube; wherein,

[0011] The first end of the first MOS tube is connected to the battery voltage end, the second end of the first MOS tube is connected to the resistance voltage dividing unit, the third end of the first MOS tube is connected to the first end of the second MOS tube, the second end of the second MOS tube is grounded, and the third end of the second MOS tube is connected to the enable end of the single-chip computer.

[0012] In some embodiments, the first MOS transistor is a P-channel MOS transistor, and the second MOS transistor is an N-channel MOS transistor.

[0013] In some embodiments, the voltage division detection module further includes a first resistor; wherein a first end of the first resistor is connected to the battery voltage end, and a second end of the first resistor is respectively connected to a third end of the first MOS tube and a first end of the second MOS tube.

[0014] In some embodiments, the resistor voltage dividing unit includes a second resistor, a third resistor and a fourth resistor; wherein,

[0015] The first end of the second resistor is connected to the second end of the first MOS tube, the second end of the second resistor is respectively connected to the first end of the third resistor and the first end of the operational amplifier follower module, the second end of the third resistor is connected to the first end of the fourth resistor, and the second end of the fourth resistor is grounded.

[0016] In some embodiments, the op amp follower module includes an operational amplifier.

[0017] In some embodiments, the battery voltage detection circuit further includes a first capacitor, a second capacitor and a third capacitor; wherein,

[0018] The first end of the first capacitor is connected to the first end of the operational amplifier, the second end of the first capacitor is grounded, the first end of the second capacitor is connected to the fifth end of the operational amplifier, the second end of the second capacitor is grounded, the first end of the third capacitor is connected to the fourth end of the operational amplifier, and the second end of the third capacitor is grounded.

[0019] The utility model proposes a battery voltage detection circuit, including: a voltage division detection module, an operational amplifier follower module and a single chip microcomputer; wherein, the first input end of the voltage division detection module is connected to the battery voltage end of the battery to be tested, the second input end of the voltage division detection module is connected to the single chip microcomputer, the output end of the voltage division detection module is connected to the first end of the operational amplifier follower module, the second end of the operational amplifier follower module is grounded, the third end of the operational amplifier follower module is connected to the fourth end of the operational amplifier follower module, and the fourth end of the operational amplifier follower module is connected to the single chip microcomputer. In the utility model, an operational amplifier follower module is added to the detection end of the voltage division detection module to ensure that the voltage is consistent while the impedance of the front and rear detections is not affected. According to the actual situation, the voltage of the battery to be tested can be detected by the output level of the single chip microcomputer, so that the single chip microcomputer turns off the battery voltage detection circuit when the detection is not needed, so that the power consumption is reduced to 0, which can effectively extend the storage time and service life of the battery product, and solve the problems of the battery voltage detection technology of the existing POS equipment having a large power consumption, resulting in a decrease in battery efficiency and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a module of a battery voltage detection circuit according to an embodiment of the present utility model;

[0021] Figure 2 The present invention is a schematic diagram of a circuit structure of a battery voltage detection circuit according to an embodiment of the present invention.

[0022] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0024] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0025] In addition, the descriptions of "first", "second", etc. in the present utility model are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present utility model. It should be understood that the specific embodiments described here are only used to explain the present utility model and are not used to limit the present utility model.

[0026] The utility model provides a battery voltage detection circuit.

[0027] Reference Figure 1 , Figure 1 The present invention is a schematic diagram of a module of a battery voltage detection circuit according to an embodiment of the present invention.

[0028] like Figure 1 As shown, the battery voltage detection circuit includes: a voltage division detection module 100, an operational amplifier follower module 200 and a single-chip microcomputer MCU; wherein,

[0029] The first input end of the voltage division detection module 100 is connected to the battery voltage terminal LI_BAT of the battery to be tested, the second input end of the voltage division detection module 100 is connected to the single-chip microcomputer MCU, the output end of the voltage division detection module 100 is connected to the first end of the operational amplifier follower module 200, the second end of the operational amplifier follower module 200 is grounded, the third end of the operational amplifier follower module 200 is connected to the fourth end of the operational amplifier follower module 200, and the fourth end of the operational amplifier follower module 200 is connected to the single-chip microcomputer MCU.

[0030] It should be noted that the POS device can be charged by a rechargeable battery and / or an external power supply. This embodiment is described by taking the battery voltage detection of the rechargeable battery of the POS device as an example. The battery voltage detection circuit proposed in this embodiment is a low-power battery voltage detection circuit, which reduces power consumption to avoid battery energy overflow and improves the effective use of the battery.

[0031] In one embodiment, reference Figure 1 and Figure 2 The voltage division detection module 100 includes: a switch unit 101 and a resistor voltage division unit 102; wherein,

[0032] The input end of the switch unit 101 is connected to the enable end of the single-chip microcomputer MCU and the battery voltage end LI_BAT respectively, the output end of the switch unit 101 is connected to the resistor voltage divider unit 102, and the resistor voltage divider unit 102 is also connected to the operational amplifier follower module 200.

[0033] Specifically, the battery voltage detection circuit of this embodiment is improved on the basis of the resistance voltage division method. While dividing the voltage through the voltage division detection module 100, an operational amplifier follower (operational amplifier follower module 200) is added to ensure that the voltage is consistent while the impedance of the front and rear detections is not affected. In addition, the voltage detection of the battery to be tested can be started or shut down by the single-chip microcomputer MCU according to actual conditions.

[0034] In one embodiment, reference Figure 1 and Figure 2 When detecting the voltage of the battery to be tested, the enable end of the single-chip microcomputer MCU outputs a high level to the switch unit 101 to turn on the battery voltage detection circuit; when stopping detecting the voltage of the battery to be tested, the enable end of the single-chip microcomputer MCU is grounded and outputs a low level to the switch unit 101 to turn off the switch unit 101 and the resistor divider unit 102.

[0035] Specifically, in this embodiment, the output level of the single-chip microcomputer is used to control the battery voltage detection circuit to detect the voltage of the battery to be tested. In one example, when the voltage of the battery to be tested needs to be detected, the single-chip microcomputer outputs a high level, turns on the switch unit 101, and turns on the battery voltage detection circuit. In another example, when the voltage of the battery to be tested does not need to be detected, the single-chip microcomputer outputs a low level to the ground, turns off the switch unit 101, and thus turns off the voltage divider network resistor voltage divider unit 102, so that the power consumption is reduced to 0, which can effectively extend the storage time and service life of the battery product.

[0036] In one embodiment, reference Figure 2 The switch unit 101 includes: a first MOS transistor Q1 and a second MOS transistor Q2; wherein,

[0037] A first end of the first MOS transistor Q1 is connected to the battery voltage terminal LI_BAT, a second end of the first MOS transistor Q1 is connected to the resistance voltage dividing unit 102, a third end of the first MOS transistor Q1 is connected to a first end of the second MOS transistor Q2, a second end of the second MOS transistor Q2 is grounded, and a third end of the second MOS transistor Q2 is connected to an enable end of the single-chip computer MCU.

[0038] Specifically, Figure 2As shown, the first end of the first MOS tube Q1 is connected to the battery voltage terminal LI_BAT, that is, the switch unit 101 is connected to the battery to be tested, and the VBAT_ADC voltage can be obtained by dividing the battery voltage of LI_BAT. The enable terminal SYSPW_EN of the microcontroller MCU controls the switch of the second MOS tube Q2 to control the power on and off.

[0039] Exemplarily, when the voltage of the battery to be tested needs to be detected, the enable terminal SYSPW_EN of the single-chip microcomputer MCU is pulled high (output high level), and the first MOS tube Q1 and the second MOS tube Q2 are turned on to turn on the battery voltage detection circuit. When the voltage of the battery to be tested does not need to be detected, the enable terminal SYSPW_EN of the single-chip microcomputer MCU is pulled low (output low level), the first MOS tube Q1 and the second MOS tube Q2 are not turned on, so that VBAT_ADC has no voltage, and there is almost no power loss here.

[0040] In one embodiment, reference Figure 2 , the first MOS transistor Q1 is a P-channel type MOS transistor, and the second MOS transistor Q2 is an N-channel type MOS transistor.

[0041] Specifically, this embodiment is described by taking the first MOS transistor Q1 as a P-channel type MOS transistor and the second MOS transistor Q2 as an N-channel type MOS transistor as an example. In this embodiment, by using MOS transistors for circuit switching, it is realized whether to perform voltage detection on the battery to be tested according to actual conditions, with low loss and high stability.

[0042] For example, the model of the first MOS transistor Q1 may be GP3139 (P channel), and the model of the second MOS transistor Q2 may be JMTL3134KT5 (N channel). It is understandable that the specific types of the first MOS transistor Q1 and the second MOS transistor Q2 may be set according to actual conditions, and this embodiment does not limit this.

[0043] In one embodiment, reference Figure 2 The voltage division detection module 100 further includes a first resistor R1; wherein a first end of the first resistor R1 is connected to the battery voltage terminal LI_BAT, and a second end of the first resistor R1 is respectively connected to a third end of the first MOS tube Q1 and a first end of the second MOS tube Q2.

[0044] In one embodiment, reference Figure 2 , the resistor voltage dividing unit 102 includes a second resistor R2, a third resistor R3 and a fourth resistor R4; wherein,

[0045] The first end of the second resistor R2 is connected to the second end of the first MOS tube Q1, the second end of the second resistor R2 is respectively connected to the first end of the third resistor R3 and the first end of the operational amplifier follower module 200, the second end of the third resistor R3 is connected to the first end of the fourth resistor R4, and the second end of the fourth resistor R4 is grounded.

[0046] Specifically, the output end of the battery voltage detection circuit, namely the VBAT_SNS detection pin, is connected to the detection end of the single-chip computer MCU, the second resistor R2, the third resistor R3 and the fourth resistor R4 constitute a resistor voltage divider unit 102, and the VBAT_ADC voltage is obtained by dividing the voltage LI_BAT of the battery to be tested.

[0047] Exemplarily, the VBAT_ADC voltage is obtained by collecting the sampled voltage of the connection node between the two voltage-dividing resistors, the voltage-dividing resistors include a second resistor R2, a third resistor R3, and a fourth resistor R4, and the first switch, i.e., the first MOS tube Q1, is connected in series between the battery voltage terminal LI_BAT of the battery to be tested and the first voltage-dividing resistor, i.e., the second resistor R2. It should be emphasized that the connection method of the switch (the first MOS tube Q1 and the second MOS tube Q2) includes multiple connection methods and is not limited to Figure 2 In this embodiment, the test voltage of the connection node between the second resistor R2 and the third resistor R3 is taken as the VBAT_ADC voltage for illustration. It should be noted that the connection node includes but is not limited to the connection node between the second resistor R2 and the third resistor R3 or the connection node between the second resistor R2 and the third resistor R3, and this embodiment does not limit this.

[0048] For example, the resistance of the first resistor R1 can be 20K / F (ohm), the resistance of the second resistor R2 can be 150K / F (ohm), the resistance of the third resistor R3 can be 0R (ohm), and the resistance of the fourth resistor R4 can be 150K / F (ohm), wherein the third resistor R3 can be a jumper resistor, and the resistance value is very small and close to zero; the resistance value error precision is usually represented by characters: F represents 1%. It can be understood that the specific resistance values ​​of the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 can be set according to actual conditions, and this embodiment does not limit this.

[0049] In one embodiment, the operational amplifier follower module 200 includes an operational amplifier U.

[0050] It can be understood that the output end of the battery voltage detection circuit, i.e., the VBAT_SNS detection pin, is connected to the detection end of the single-chip microcomputer MCU, the second resistor R2, the third resistor R3, and the fourth resistor R4 form a voltage divider, and the VBAT_ADC voltage is obtained by the voltage divider of the battery voltage LI_BAT to be tested. The output voltage VBAT_SNS of the battery voltage detection circuit is consistent with the VBAT_ADC voltage due to the op amp follower (op amp follower module 200), and when the LI_BAT impedance changes, due to the op amp effect of the operational amplifier U in the op amp follower module 200, the sampling voltage of the VBAT_SNS detection pin does not change much, making the voltage detection of the battery to be tested more accurate. When it is necessary to detect the voltage of the battery to be tested, the enable end SYSPW_EN of the single-chip microcomputer MCU is pulled high (output high level), and the first MOS tube Q1 and the second MOS tube Q2 are turned on to connect the battery voltage detection circuit. When there is no need to detect the voltage of the battery to be tested, the enable terminal SYSPW_EN of the microcontroller MCU is pulled low (output low level), the first MOS tube Q1 and the second MOS tube Q2 are not turned on, so that VBAT_ADC has no voltage, and there is almost no power loss here.

[0051] Exemplarily, the 133rd pin of the single-chip microcomputer MCU is connected to the output end (i.e., the fourth end) of the operational amplifier U, the drain (D pole) of the second MOS tube Q2 is connected to the gate (G pole) of the first MOS tube Q1, and the source (S pole) of the first MOS tube Q1 is connected to the battery to be tested. In this embodiment, the output level of the single-chip microcomputer is used to control the detection of the battery voltage by the battery voltage detection circuit. When the battery voltage needs to be detected, the single-chip microcomputer outputs a high level, turns on the MOS tube, and turns on the battery voltage detection circuit. When detection is not required, the single-chip microcomputer is grounded, outputs a low level, turns off the MOS tube, and thus turns off the voltage divider network, so that the power consumption is reduced to 0, which can effectively extend the storage time and service life of the battery product. The circuit structure of the utility model is simple and easy to use.

[0052] In one embodiment, the battery voltage detection circuit further includes a first capacitor C1, a second capacitor C2 and a third capacitor C3; wherein,

[0053] A first end of the first capacitor C1 is connected to a first end of the operational amplifier U, a second end of the first capacitor C1 is grounded, a first end of the second capacitor C2 is connected to a fifth end of the operational amplifier U, a second end of the second capacitor C2 is grounded, a first end of the third capacitor C3 is connected to a fourth end of the operational amplifier U, and a second end of the third capacitor C3 is grounded.

[0054] Specifically, the first terminal (1) of the operational amplifier U is the positive input terminal (+), the second terminal (2) of the operational amplifier U is the negative input terminal (V-) of the power supply, the second terminal of the operational amplifier U is grounded, the third terminal (3) of the operational amplifier U is the negative input terminal (-), the fourth terminal (4) of the operational amplifier U is the output terminal (OUT), and the fifth terminal (5) of the operational amplifier U is the positive input terminal (V+) of the power supply.

[0055] For example, Figure 2 As shown, the first capacitor C1 is connected to the positive input terminal (+) of the operational amplifier U, and can be used for filtering to filter out high-frequency interference signals; the second capacitor C2 is connected to the positive power input terminal V+ of the operational amplifier U, and can be used for filtering to suppress interference signals; the third capacitor C3 is connected to the output terminal OUT of the operational amplifier U, and can be used to stabilize the circuit.

[0056] It is understandable that multiple capacitors are arranged around the operational amplifier U for anti-interference and filtering, so that the operational amplifier U can operate more stably. The specific number and connection method of the capacitors can be set according to actual conditions, and this embodiment does not limit this.

[0057] According to the above analysis, this embodiment proposes a low-power battery voltage detection circuit, which may include: a single-chip microcomputer MCU, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first MOS tube Q1, a second MOS tube Q2, a first capacitor C1, a second capacitor C2, and a third capacitor C3 and an operational amplifier U. The model of the single-chip microcomputer MCU includes but is not limited to ZX400-H3, the VBAT_SNS detection pin of the single-chip microcomputer MCU (for example, the 133rd pin of ZX400-H3) is connected to the output end of the operational amplifier U, the drain of the second MOS tube Q2 is connected to the gate of the first MOS tube Q1, and the source of the first MOS tube Q1 is connected to the battery.

[0058] This embodiment uses the output level of the single-chip computer MCU to control the battery voltage detection circuit to detect the battery voltage: when the battery voltage needs to be detected, the single-chip computer outputs a high level, turns on the MOS tube, and connects the battery voltage detection circuit; when detection is not required, the single-chip computer is grounded and outputs a low level, turns off the MOS tube, thereby turning off the voltage divider network, reducing the power consumption to 0, which can effectively extend the storage time and service life of the battery product. The battery voltage detection circuit in this embodiment has a simple circuit structure and is easy to use.

[0059] It should be understood that the above is only an example and does not constitute any limitation on the technical solution of the present invention. In specific applications, technicians in this field can make settings as needed, and the present invention does not impose any limitation on this.

[0060] It should be noted that the workflow described above is merely illustrative and does not limit the scope of protection of the present utility model. In practical applications, technicians in this field can select part or all of them according to actual needs to achieve the purpose of the present embodiment, and no limitation is made here.

[0061] In addition, it should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, article or system. In the absence of more restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, article or system including the element.

[0062] The serial numbers of the above-mentioned embodiments of the present invention are only for description and do not represent the advantages or disadvantages of the embodiments.

[0063] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A battery voltage detection circuit, characterized in that: include: Voltage division detection module, operational amplifier follower module and single chip microcomputer; among them, The first input end of the voltage division detection module is connected to the battery voltage end of the battery to be tested, the second input end of the voltage division detection module is connected to the single-chip microcomputer, the output end of the voltage division detection module is connected to the first end of the operational amplifier follower module, the second end of the operational amplifier follower module is grounded, the third end of the operational amplifier follower module is connected to the fourth end of the operational amplifier follower module, and the fourth end of the operational amplifier follower module is connected to the single-chip microcomputer.

2. The circuit according to claim 1, characterized in that The voltage division detection module includes: a switch unit and a resistor voltage division unit; wherein, The input end of the switch unit is connected to the enable end of the single chip microcomputer and the battery voltage end respectively, the output end of the switch unit is connected to the resistor voltage divider unit, and the resistor voltage divider unit is also connected to the operational amplifier follower module.

3. The circuit according to claim 2, characterized in that When detecting the voltage of the battery to be tested, the enable terminal of the single-chip microcomputer outputs a high level to the switch unit to turn on the battery voltage detection circuit; when stopping detecting the voltage of the battery to be tested, the enable terminal of the single-chip microcomputer is grounded and outputs a low level to the switch unit to turn off the switch unit and the resistor divider unit.

4. The circuit according to claim 2, characterized in that The switch unit includes: a first MOS tube and a second MOS tube; wherein, The first end of the first MOS tube is connected to the battery voltage end, the second end of the first MOS tube is connected to the resistance voltage dividing unit, the third end of the first MOS tube is connected to the first end of the second MOS tube, the second end of the second MOS tube is grounded, and the third end of the second MOS tube is connected to the enable end of the single-chip computer.

5. The circuit according to claim 4, characterized in that The first MOS transistor is a P-channel MOS transistor, and the second MOS transistor is an N-channel MOS transistor.

6. The circuit according to claim 4, characterized in that The voltage division detection module also includes a first resistor; wherein a first end of the first resistor is connected to the battery voltage end, and a second end of the first resistor is respectively connected to a third end of the first MOS tube and a first end of the second MOS tube.

7. The circuit according to claim 4, characterized in that The resistor voltage dividing unit includes a second resistor, a third resistor and a fourth resistor; wherein, The first end of the second resistor is connected to the second end of the first MOS tube, the second end of the second resistor is respectively connected to the first end of the third resistor and the first end of the operational amplifier follower module, the second end of the third resistor is connected to the first end of the fourth resistor, and the second end of the fourth resistor is grounded.

8. The circuit according to claim 1, characterized in that The operational amplifier follower module includes an operational amplifier.

9. The circuit according to claim 8, characterized in that The battery voltage detection circuit also includes a first capacitor, a second capacitor and a third capacitor; wherein, The first end of the first capacitor is connected to the first end of the operational amplifier, the second end of the first capacitor is grounded, the first end of the second capacitor is connected to the fifth end of the operational amplifier, the second end of the second capacitor is grounded, the first end of the third capacitor is connected to the fourth end of the operational amplifier, and the second end of the third capacitor is grounded.

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