AC voltage divider circuit and calibration method

Abstract

The invention provides an alternating current voltage divider circuit and a calibration method, a voltage division circuit is provided with a reverse-phase amplification circuit formed by a first operational amplifier, a voltage divider high-end proportional arm and a voltage divider low-end proportional arm, the voltage divider high-end proportional arm is provided with a plurality of high-end resistors which are sequentially connected in series, the voltage divider low-end proportional arm is provided with a low-end resistor, and the low-end resistor is connected with the first operational amplifier. The compensating circuit is internally provided with an in-phase amplifying circuit formed by a second operational amplifier, the voltage division circuit is electrically connected with the compensating circuit, the voltage division circuit outputs divided voltage based on resistance values of a high-end proportional arm and a low-end proportional arm of the voltage divider, and the compensating circuit compensates input voltage of an inverted input end of the first operational amplifier. And the input voltage difference between the inverting input end and the non-inverting input end of the first operational amplifier is reduced, so that the precision of the voltage division proportion of the alternating-current voltage divider is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of precision electromagnetic measurement, and in particular relates to an AC voltage divider circuit and a calibration method. Background Art

[0002] When measuring AC power, an AC voltage divider is usually used to convert the high-value voltage output by the AC power source into a low-value voltage suitable for measurement. The resistive voltage divider composed of precision resistor elements has the advantages of high accuracy, good linearity, and a wide frequency range, so it is widely used in AC power measurement.

[0003] However, under the existing technology, the resistive voltage divider is affected by factors such as the consistency of the resistor elements, the time constant, the residual inductance in the voltage divider structure, the capacitive leakage between the high-end resistor elements and between the low-end resistor and the casing, which may cause voltage division errors. Conventional passive resistive voltage dividers are usually designed with two proportional arms. The main proportional arm is used to divide the measured voltage, and the auxiliary proportional arm is used to provide an equipotential protection voltage, reduce the capacitive leakage of the main proportional arm, and reduce the phase error of the resistive voltage divider. However, its output impedance is large. When it is connected to a load with a lower input impedance, the output voltage may be affected by the load and change, resulting in a large inaccurate measurement result. In order to further reduce the output impedance of the voltage divider and reduce the influence of the measured input impedance on the AC voltage, a precision voltage follower is usually required to be additionally provided at the output end of the resistive voltage divider for impedance transformation, resulting in a complex circuit structure design of the AC voltage divider and a high cost of use. Summary of the invention

[0004] The present invention provides an AC voltage divider circuit and a calibration method to solve the technical problems in the prior art that the conventional AC voltage divider has a large output voltage error and a complex circuit structure design.

[0005] To solve the above problems, the technical solution of the present invention is: an AC voltage divider circuit, comprising: a voltage divider circuit and a compensation circuit; The voltage divider circuit is provided with a first operational amplifier, a high-end proportional arm of a voltage divider and a low-end proportional arm of a voltage divider, wherein a first end of the high-end proportional arm of the voltage divider is connected to a voltage input end, a second end of the high-end proportional arm of the voltage divider is connected to an inverting input end of the first operational amplifier, a first end of the low-end proportional arm of the voltage divider is connected to an inverting input end of the first operational amplifier, a second end of the low-end proportional arm of the voltage divider is connected to an output end of the first operational amplifier, and a non-inverting input end of the first operational amplifier is connected to a ground end; A plurality of high-end resistors are arranged in series in the high-end proportional arm of the voltage divider, and a low-end resistor is arranged in the low-end proportional arm of the voltage divider; The compensation circuit is provided with a second operational amplifier, an inverting input terminal of the second operational amplifier is connected in series with a first input resistor and then connected to a ground terminal, a first branch of an output terminal of the second operational amplifier is connected in series with a first negative feedback resistor and then connected to an inverting input terminal of the second operational amplifier, a second branch of an output terminal of the second operational amplifier is connected in series with a compensation resistor and then connected to a non-inverting input terminal of the second operational amplifier, and a first node formed by connecting the compensation resistor and the non-inverting input terminal of the second operational amplifier is commonly connected to a second node formed by connecting a high-end proportional arm of the voltage divider and an inverting input terminal of the first operational amplifier; An AC voltage divider circuit is configured such that the voltage divider circuit outputs a divided voltage based on the resistance values ​​of a high-end proportional arm of the voltage divider and a low-end proportional arm of the voltage divider, and compensates the input voltage of the inverting input terminal of the first operational amplifier through the compensation circuit, so that the input voltage difference between the inverting input terminal and the non-inverting input terminal of the first operational amplifier is reduced.

[0006] Preferably, the voltage divider circuit is further provided with an auxiliary voltage branch, a first end of the auxiliary voltage branch is connected to the voltage input end, and a second end of the auxiliary voltage branch is connected to the ground end; The auxiliary voltage branch is provided with a plurality of equipotential protection resistors connected in series in sequence, and the total resistance of the auxiliary voltage branch is limited to twice the total resistance of the high-end proportional arm of the voltage divider. The auxiliary voltage branch is used to provide an equipotential protection voltage for the voltage divider circuit.

[0007] Preferably, copper foil is respectively provided on the outside of the high-end resistor, and a plurality of wires extend from the auxiliary voltage branch and are respectively electrically connected to the copper foil, so that a plurality of copper foils can form an equipotential shielding layer of the high-end proportional arm of the voltage divider, which is used to realize the equipotential electromagnetic shielding function of the high-end proportional arm of the voltage divider.

[0008] Preferably, a first bias resistor is connected in series between the non-inverting input terminal and the ground terminal of the first operational amplifier.

[0009] Preferably, the AC voltage divider circuit also includes a calibration circuit, which is provided with a third operational amplifier, the inverting input terminal of the third operational amplifier is connected to the second input resistor and the third input resistor arranged in parallel, and the output terminal of the third operational amplifier is connected in series with the second negative feedback resistor and then connected to the inverting input terminal of the third operational amplifier, and the non-inverting input terminal of the third operational amplifier is connected in series with the second bias resistor and then connected to the ground terminal.

[0010] Preferably, the third input resistor is an adjustable resistor.

[0011] Preferably, the output end of the calibration circuit is connected to a lock-in amplifier, and the lock-in amplifier is used to collect the difference voltage output by the calibration circuit.

[0012] Preferably, the calibration circuit can be selectively connected to a two-stage inductive voltage divider, the input end of the two-stage inductive voltage divider is connected to the voltage input end, the first stage output end of the two-stage inductive voltage divider is connected to the first end of the second input resistor, and the second stage output end of the two-stage inductive voltage divider is connected to the first end of the third input resistor. The two-stage inductive voltage divider is used to realize the self-calibration operation of the calibration circuit.

[0013] Preferably, the calibration circuit can also selectively connect to the voltage divider circuit, the compensation circuit and a multi-bit inductive voltage divider with a self-calibration function, the voltage divider circuit is electrically connected to the compensation circuit, and the input end of the voltage divider circuit is connected to the voltage input end, the output end of the voltage divider circuit is connected to the first end of the second input resistor, the input end of the multi-bit inductive voltage divider is connected to the voltage input end, and the output end of the multi-bit inductive voltage divider is connected to the first end of the third input resistor, and the calibration circuit after self-calibration is used to calculate the actual voltage divider ratio of the voltage divider circuit and the compensation circuit.

[0014] Based on the same concept, the present invention also provides an AC voltage divider circuit calibration method, which is applied to any of the AC voltage divider circuits described above, and sets the second input resistor, the second negative feedback resistor, and the third input resistor in the first state in the calibration circuit to have the same resistance value, including the following steps: S1: constructing a voltage divider circuit and a compensation circuit, and enabling the voltage divider circuit to be electrically connected to the compensation circuit; S2: a two-stage inductive voltage divider is connected to the calibration circuit, and a differential voltage output by the calibration circuit is measured based on a lock-in amplifier, and the resistance value of the third input resistor is adjusted to a second state, so that the in-phase component of the differential voltage measured by the lock-in amplifier is reduced; The calculation formula for the first reading △1 of the lock-in amplifier is as follows: Among them, α0 and β0 are the in-phase and quadrature components of the two-stage output voltage ratio error of the two-stage inductive voltage divider, respectively. A and β A They are respectively the in-phase and quadrature components of the error caused by the inconsistency of the voltage input branches of the calibration circuit; S3: self-calibrate the voltage ratio of the multi-bit inductive voltage divider to obtain the voltage ratio error k of the multi-bit inductive voltage divider IVD , in-phase component α1 and quadrature component β1; S4: Connect the voltage divider circuit, the compensation circuit and the calibrated multi-bit inductive voltage divider to the calibration circuit, keep the resistance of the third input resistor in the second state, obtain the differential voltage output by the lock-in amplifier to measure the calibration circuit, and the calculation formula of the second reading △2 of the lock-in amplifier is as follows: Then, the voltage division ratio k between the voltage division circuit and the compensation circuit is d The calculation formula is as follows: The actual voltage division ratio of the voltage division circuit and the compensation circuit is obtained by calculation.

[0015] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art: The present invention provides an AC voltage divider circuit and calibration method. A voltage divider circuit is constructed by a first operational amplifier, a high-end proportional arm of a voltage divider and a low-end proportional arm of a voltage divider to realize a voltage divider measurement function. At the same time, in order to overcome the offset voltage existing at the inverting input terminal of the first operational amplifier under non-ideal conditions, a compensation circuit is provided to compensate for the input voltage of the inverting input terminal of the first operational amplifier, so that the input voltage difference between the inverting input terminal and the non-inverting input terminal of the first operational amplifier can be reduced, thereby improving the accuracy of the voltage divider ratio of the AC voltage divider. At the same time, in order to further clarify the actual voltage divider ratio value of the AC voltage divider, a calibration circuit is also provided. First, the calibration circuit itself is self-calibrated, and then the voltage divider circuit and the compensation circuit are connected to the calibration circuit. The actual value calculation of the voltage divider ratio of the AC voltage divider is realized by means of the calibration circuit after self-calibration, thereby improving the accuracy of the actual voltage divider ratio of the AC voltage divider. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram of the circuit structure of the voltage divider circuit and the compensation circuit provided by the present invention; Figure 2 A schematic diagram of the circuit structure of a two-stage inductive voltage divider provided by the present invention connected to a calibration circuit; Figure 3 A schematic diagram of a circuit structure in which a multi-bit inductive voltage divider and an AC voltage divider are connected to a calibration circuit provided by the present invention. DETAILED DESCRIPTION

[0017] The following is a further detailed description of an AC voltage divider circuit and calibration method proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims.

[0018] First embodiment See also Figures 1 to 3This embodiment provides an AC voltage divider circuit to realize the voltage division function of the AC voltage divider and the calibration calculation function of its voltage division ratio value.

[0019] The main body of the AC voltage divider circuit includes a voltage divider circuit and a compensation circuit. The voltage divider circuit and the compensation circuit are used together to construct the main circuit of the AC voltage divider, which is used to realize the voltage dividing function of the AC voltage divider, that is, to convert the input high-voltage AC signal into a low-voltage AC signal output.

[0020] Specifically, the voltage divider circuit is provided with a first operational amplifier A1, a high-end proportional arm of a voltage divider and a low-end proportional arm of a voltage divider, the first end of the high-end proportional arm of the voltage divider is connected to the voltage input terminal U1, the second end of the high-end proportional arm of the voltage divider is connected to the inverting input terminal of the first operational amplifier A1, the first end of the low-end proportional arm of the voltage divider is connected to the inverting input terminal of the first operational amplifier A1, the second end of the low-end proportional arm of the voltage divider is connected to the output terminal U2 of the first operational amplifier, and the non-inverting input terminal of the first operational amplifier A1 is connected to the ground terminal. It can be understood that the first operational amplifier A1, the high-end proportional arm of the voltage divider and the low-end proportional arm of the voltage divider form an inverting amplifier circuit.

[0021] Among them, a number of high-end resistors R1-R1 are connected in series in the high-end proportional arm of the voltage divider. n , a low-end resistor R is provided in the low-end proportional arm of the voltage divider. low .

[0022] The compensation circuit is provided with a second operational amplifier A2, and the inverting input terminal of the second operational amplifier A2 is connected in series with a first input resistor R c The first branch of the output terminal of the second operational amplifier A2 is connected in series with the first negative feedback resistor R f1 Then connected to the inverting input terminal of the second operational amplifier A2, it can be understood that the second operational amplifier A2, the first negative feedback resistor R f1 With the first input resistor R c A common-phase amplifier circuit is formed, and in this embodiment, the first input resistor R is set c The first negative feedback resistor R f1 The resistance values ​​are the same, so that the output voltage amplification gain of the second operational amplifier A2 is twice.

[0023] The second branch at the output end of the second operational amplifier A2 is connected in series with a compensation resistor R m Then connected to the non-inverting input terminal of the second operational amplifier A2, and the compensation resistor R m A first node formed by connecting the non-inverting input terminal of the second operational amplifier A2 is commonly connected to a second node formed by connecting the high-end proportional arm of the voltage divider and the inverting input terminal of the first operational amplifier A1.

[0024] Set the high-end resistors R1-R in series in the high-end proportional arm of the voltage divider. n The overall admittance is y1, and the low-end resistor R low The admittance of is y2, then Assume that the power input terminal of the voltage divider circuit is U1, the output terminal of the voltage divider circuit is U2, and the input voltage of the inverting input terminal of the first operational amplifier A1 is U0. For the inverting input terminal of the first operational amplifier A1, according to Kirchhoff's law, it can be known that Where y0 is the input admittance of the first operational amplifier A1, y p is the compensation resistor R in the compensation circuit m admittance, k is the amplification gain multiple of the compensation circuit.

[0025] Under non-ideal conditions, due to hardware conditions, the first operational amplifier A1 will have a certain amount of tiny current flowing in or out, that is, there is an input offset voltage, which causes a difference between the input voltages of the in-phase input terminal and the inverting input terminal of the first operational amplifier A1, resulting in an error in the voltage divider output by the voltage divider circuit, and poor accuracy. In order to eliminate the influence of the input voltage of the inverting input terminal of the first operational amplifier A1 on the AC voltage divider, it should be made If the compensation resistor R m The resistance value makes but It can be seen that after eliminating the influence of the input voltage of the inverting input terminal of the first operational amplifier A1 on the AC voltage divider, the voltage division ratio k of the AC voltage divider is d It is only related to the resistance of the high-end proportional arm and the low-end proportional arm of the voltage divider. The theoretical voltage divider ratio k of the AC voltage divider is d The value can be calculated by the resistance of the high-side proportional arm of the voltage divider and the low-side proportional arm of the voltage divider.

[0026] In summary, this embodiment provides an AC voltage divider circuit, which can output a divided voltage based on the resistance of the high-end proportional arm of the voltage divider and the low-end proportional arm of the voltage divider. At the same time, the input voltage of the inverting input terminal of the first operational amplifier A1 is compensated by the compensation circuit, so that the input voltage difference between the inverting input terminal and the non-inverting input terminal of the first operational amplifier A1 is reduced, thereby effectively reducing the influence of non-ideal factors such as the input offset voltage or input bias current of the inverting input terminal of the first operational amplifier A1 on the voltage dividing ratio of the AC voltage divider, thereby improving the voltage ratio accuracy of the AC voltage divider.

[0027] The specific structural design of an AC voltage divider circuit provided in this embodiment will be further described in detail below: Preferably, in this embodiment, the voltage divider circuit is further provided with an auxiliary voltage branch, the first end of the auxiliary voltage branch is connected to the voltage input terminal U1, and the second end of the auxiliary voltage branch is connected to the ground terminal. Specifically, a plurality of equipotential protection resistors R connected in series are provided in the auxiliary voltage branch. 10 -R n0 In this embodiment, if a high-end resistor R1 is provided in the high-end proportional arm of the voltage divider, two equipotential protection resistors R 10 , and two equipotential protection resistors R 10 The resistance of the auxiliary voltage branch is equal to the resistance of the high-end resistor R1, and so on, so that the total resistance of the auxiliary voltage branch is twice the total resistance of the high-end proportional arm of the voltage divider. In this embodiment, by setting the auxiliary voltage branch, when the power supply at the power input end or output end of the voltage divider circuit fluctuates or the load changes, an equipotential protection voltage is provided for the voltage divider circuit, so that the voltage in the high-end proportional arm of the voltage divider can be kept stable, thereby improving the stability of the voltage divider function of the AC voltage divider.

[0028] Furthermore, in this embodiment, a copper foil is respectively sheathed on the outside of any high-end resistor in the high-end proportional arm of the voltage divider, and a plurality of wires are extended from the auxiliary voltage branch and are respectively electrically connected to the copper foil, so that the copper foil is conductive, and a plurality of copper foils form an equipotential shielding layer S1-S2 of the high-end proportional arm of the voltage divider. n , copper foil can effectively reflect and absorb electromagnetic waves, thereby reducing the impact of external electromagnetic fields on high-end resistors and their surrounding circuits, and improving the stability of the voltage division function of the AC voltage divider.

[0029] Preferably, in this embodiment, a first bias resistor R is connected in series between the non-inverting input terminal of the first operational amplifier A1 and the ground terminal. bias1 , the first bias resistor R bias1The bias current of the non-inverting input terminal of the first operational amplifier A1 can be reduced, thereby optimizing the input voltages of the non-inverting input terminal and the inverting input terminal of the first operational amplifier A1 to maintain the same level, thereby reducing the error caused by the difference in input bias current.

[0030] Preferably, in this embodiment, the AC voltage divider circuit further includes a calibration circuit. It is worth noting that the voltage divider circuit and the compensation circuit provided in this embodiment can fully realize the accurate voltage divider function of the AC voltage divider, and the calibration circuit is only used to calibrate and calculate the actual voltage divider ratio k of the AC voltage divider. d The numerical value of .

[0031] Specifically, the calibration circuit is provided with a third operational amplifier A3, and the inverting input terminal of the third operational amplifier A3 is connected in parallel with the second input resistor R a With the third input resistor R b The output terminal of the third operational amplifier A3 is connected in series with a second negative feedback resistor R f2 The inverting input terminal of the third operational amplifier A3 is then connected to the inverting input terminal of the third operational amplifier A3, and the non-inverting input terminal of the third operational amplifier A3 is connected in series with the second bias resistor R bias2 Then connected to the ground terminal, it can be understood that the third operational amplifier A3 and the second input resistor R a , the third input resistor R b The second negative feedback resistor R f2 An adder circuit is constructed.

[0032] Among them, the third input resistor R b An adjustable resistor.

[0033] The output end of the calibration circuit is connected to a lock-in amplifier LIA, and the lock-in amplifier LIA is used to collect the difference voltage output by the calibration circuit.

[0034] It should be known that the third operational amplifier A3 is limited by the performance of the hardware, which will cause a certain input error in the two input branches of the adder. Therefore, in this embodiment, the calibration circuit can firstly select to connect a two-stage inductive voltage divider 1:-1IVD, and the input end of the two-stage inductive voltage divider 1:-1IVD is connected to the voltage input end U in Connect the first stage output of the two-stage inductive voltage divider 1:-1IVD to the second input resistor R a The first end of the two-stage inductive voltage divider 1:-1IVD is connected to the second stage output end and the third input resistor R b The first end is connected to, ideally, the second input resistor R a , the third input resistor R b The second negative feedback resistor R f2The resistance values ​​are the same, and the two-stage inductive voltage divider 1:-1IVD outputs two corresponding sets of voltage signals to the two input branches of the adder respectively. Then the final differential voltage reading collected by the phase-locked amplifier LIA should be 0. However, in reality, the differential voltage collected by the phase-locked amplifier LIA will have a certain value, where The calculation formula for the first reading △1 of the lock-in amplifier LIA is as follows: Among them, α0 and β0 are the in-phase and quadrature components of the proportional error of the two-stage output voltage of the two-stage inductive voltage divider 1:-1IVD, respectively. A and β A They are respectively the in-phase and quadrature components of the error caused by the inconsistency of the voltage input branches of the calibration circuit.

[0035] At this time, the third input resistor R can be manually adjusted b , so that the lock-in amplifier LIA reading is adjusted to be as small as possible, ideally to 0 value, by b The resistance value is adjusted to the second state, the calibration operation of the adder and the calibration circuit itself is completed, and the errors existing in the adder and the calibration circuit itself are eliminated.

[0036] Furthermore, after the adder and the calibration circuit complete the self-calibration operation, the calibration circuit can be selectively connected to the voltage divider circuit, the compensation circuit and the multi-bit inductive voltage divider IVD with a self-calibration function. The voltage divider circuit and the compensation circuit are electrically connected as described above, and the input end of the voltage divider circuit is connected to the voltage input end U in Connect the output end of the voltage divider circuit to the second input resistor R a The first end of the multi-bit inductive voltage divider IVD is connected to the voltage input terminal U in Connect the output of the multi-bit inductive voltage divider IVD to the third input resistor R b It is worth noting that the voltage ratio of the multi-bit inductive voltage divider IVD provided in this embodiment can be self-calibrated based on the product function design, that is, the voltage ratio error k of the multi-bit inductive voltage divider IVD can be directly obtained. IVD And parameters such as the in-phase component α1 and the orthogonal component β1. The multi-bit inductive voltage divider IVD in this embodiment only provides a reference voltage, so how to implement the self-calibration process is not specifically limited in this embodiment.

[0037] Then the third input resistor R b The resistance value remains in the second state, and the calculation formula for the second reading △2 of the phase-locked amplifier LIA is as follows: It can be obtained that the voltage divider ratio k of the AC voltage divider formed by the voltage divider circuit and the compensation circuit isd The calculation formula is as follows: In summary, due to the voltage ratio error k of the multi-bit inductive voltage divider IVD IVD If the parameters such as the in-phase component α1 and the orthogonal component β1 are known, the actual voltage divider ratio k of the AC voltage divider can be obtained by solving d The numerical value of .

[0038] Second embodiment Based on the same concept, the present invention also provides an AC voltage divider circuit calibration method, which is applied to the AC voltage divider circuit described in any one of the first embodiments above, and sets the second input resistor R in the calibration circuit. a , the second negative feedback resistor R f2 And the third input resistance R in the first state b The resistance value is the same, including the following steps: S1: constructing a voltage divider circuit and a compensation circuit, and enabling the voltage divider circuit and the compensation circuit to be electrically connected to form a main circuit of the AC voltage divider.

[0039] S2: Connect a two-stage inductive voltage divider 1:-1IVD to the calibration circuit, measure the differential voltage output by the calibration circuit based on the lock-in amplifier LIA, and adjust the third input resistor R in the first state. b The resistance value of the calibration circuit is changed to the second state, so that the in-phase component of the difference voltage measured by the lock-in amplifier LIA decreases and tends to 0, thereby completing the self-calibration operation of the calibration circuit.

[0040] The calculation formula for the first reading △1 of the lock-in amplifier LIA is as follows: Among them, α0 and β0 are the in-phase and quadrature components of the proportional error of the two-stage output voltage of the two-stage inductive voltage divider 1:-1IVD, respectively. A and β A They are respectively the in-phase and quadrature components of the error caused by the inconsistency of the voltage input branches of the calibration circuit.

[0041] S3: self-calibrate the voltage ratio of the multi-bit inductive voltage divider IVD to obtain the voltage ratio error k of the multi-bit inductive voltage divider IVD IVD and the parameters of the in-phase component α1 and the quadrature component β1; S4: Connect the voltage divider circuit, the compensation circuit and the calibrated multi-bit inductive voltage divider IVD to the calibration circuit that completes the self-calibration operation, and keep the third input resistance R b The resistance value is in the second state, and the differential voltage output by the lock-in amplifier LIA is read. The calculation formula of the second reading △2 of the lock-in amplifier LIA is as follows: Then, the voltage division ratio k of the AC voltage divider formed by the voltage division circuit and the compensation circuit is d The calculation formula is as follows: .

[0042] From this, the actual voltage division ratio k of the AC voltage divider formed by the voltage division circuit and the compensation circuit can be calculated d The numerical value of .

[0043] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they still fall within the protection scope of the present invention.

Claims

1. An AC voltage divider circuit, characterized in that: include: Voltage divider circuit and compensation circuit; The voltage divider circuit is provided with a first operational amplifier, a high-end proportional arm of a voltage divider and a low-end proportional arm of a voltage divider, wherein a first end of the high-end proportional arm of the voltage divider is connected to a voltage input end, a second end of the high-end proportional arm of the voltage divider is connected to an inverting input end of the first operational amplifier, a first end of the low-end proportional arm of the voltage divider is connected to an inverting input end of the first operational amplifier, a second end of the low-end proportional arm of the voltage divider is connected to an output end of the first operational amplifier, and a non-inverting input end of the first operational amplifier is connected to a ground end; A plurality of high-end resistors are arranged in series in the high-end proportional arm of the voltage divider, and a low-end resistor is arranged in the low-end proportional arm of the voltage divider; The compensation circuit is provided with a second operational amplifier, an inverting input terminal of the second operational amplifier is connected in series with a first input resistor and then connected to a ground terminal, a first branch of an output terminal of the second operational amplifier is connected in series with a first negative feedback resistor and then connected to an inverting input terminal of the second operational amplifier, a second branch of an output terminal of the second operational amplifier is connected in series with a compensation resistor and then connected to a non-inverting input terminal of the second operational amplifier, and a first node formed by connecting the compensation resistor and the non-inverting input terminal of the second operational amplifier is commonly connected to a second node formed by connecting a high-end proportional arm of the voltage divider and an inverting input terminal of the first operational amplifier; An AC voltage divider circuit is configured such that the voltage divider circuit outputs a divided voltage based on the resistance values ​​of a high-end proportional arm of the voltage divider and a low-end proportional arm of the voltage divider, and compensates the input voltage of the inverting input terminal of the first operational amplifier through the compensation circuit, so that the input voltage difference between the inverting input terminal and the non-inverting input terminal of the first operational amplifier is reduced.

2. The AC voltage divider circuit according to claim 1, characterized in that: The voltage divider circuit is further provided with an auxiliary voltage branch, a first end of the auxiliary voltage branch is connected to the voltage input end, and a second end of the auxiliary voltage branch is connected to the ground end; The auxiliary voltage branch is provided with a plurality of equipotential protection resistors connected in series in sequence, and the total resistance of the auxiliary voltage branch is limited to twice the total resistance of the high-end proportional arm of the voltage divider. The auxiliary voltage branch is used to provide an equipotential protection voltage for the voltage divider circuit.

3. The AC voltage divider circuit according to claim 2, characterized in that: Copper foil is respectively sleeved on the outside of the high-end resistor, and a number of wires extend from the auxiliary voltage branch and are electrically connected to the copper foil, so that a number of copper foils can form an equipotential shielding layer of the high-end proportional arm of the voltage divider, which is used to realize the equipotential electromagnetic shielding function of the high-end proportional arm of the voltage divider.

4. The AC voltage divider circuit according to claim 1, characterized in that: A first bias resistor is connected in series between the non-inverting input terminal of the first operational amplifier and the ground terminal.

5. The AC voltage divider circuit according to claim 1, characterized in that: It also includes a calibration circuit, which is provided with a third operational amplifier, wherein the inverting input terminal of the third operational amplifier is connected to the second input resistor and the third input resistor arranged in parallel, and the output terminal of the third operational amplifier is connected in series with the second negative feedback resistor and then connected to the inverting input terminal of the third operational amplifier, and the non-inverting input terminal of the third operational amplifier is connected in series with the second bias resistor and then connected to the ground terminal.

6. The AC voltage divider circuit according to claim 5, characterized in that: The third input resistor is an adjustable resistor.

7. The AC voltage divider circuit according to claim 5, characterized in that: The output end of the calibration circuit is connected to a lock-in amplifier, and the lock-in amplifier is used to collect the difference voltage output by the calibration circuit.

8. The AC voltage divider circuit according to claim 5, characterized in that: The calibration circuit can be selectively connected to a two-stage inductive voltage divider, the input end of the two-stage inductive voltage divider is connected to the voltage input end, the first-stage output end of the two-stage inductive voltage divider is connected to the first end of the second input resistor, and the second-stage output end of the two-stage inductive voltage divider is connected to the first end of the third input resistor. The two-stage inductive voltage divider is used to realize the self-calibration operation of the calibration circuit.

9. The AC voltage divider circuit according to claim 8, characterized in that: The calibration circuit can also selectively connect to the voltage divider circuit, the compensation circuit and a multi-bit inductive voltage divider with a self-calibration function. The voltage divider circuit is electrically connected to the compensation circuit, and the input end of the voltage divider circuit is connected to the voltage input end, the output end of the voltage divider circuit is connected to the first end of the second input resistor, the input end of the multi-bit inductive voltage divider is connected to the voltage input end, and the output end of the multi-bit inductive voltage divider is connected to the first end of the third input resistor. The calibration circuit after self-calibration is used to calculate the actual voltage divider ratio of the voltage divider circuit and the compensation circuit.

10. A method for calibrating an AC voltage divider circuit, characterized in that: The AC voltage divider circuit according to any one of claims 1 to 9 is applied to setting the second input resistor, the second negative feedback resistor and the third input resistor in the calibration circuit to have the same resistance value, comprising the following steps: S1: constructing a voltage divider circuit and a compensation circuit, and enabling the voltage divider circuit to be electrically connected to the compensation circuit; S2: a two-stage inductive voltage divider is connected to the calibration circuit, and a differential voltage output by the calibration circuit is measured based on a lock-in amplifier, and the resistance value of the third input resistor is adjusted to a second state, so that the in-phase component of the differential voltage measured by the lock-in amplifier is reduced; The calculation formula for the first reading △1 of the lock-in amplifier is as follows: Among them, α0 and β0 are the in-phase and quadrature components of the two-stage output voltage ratio error of the two-stage inductive voltage divider, respectively. A and β A They are respectively the in-phase and quadrature components of the error caused by the inconsistency of the voltage input branches of the calibration circuit; S3: self-calibrate the voltage ratio of the multi-bit inductive voltage divider to obtain the voltage ratio error k of the multi-bit inductive voltage divider IVD , in-phase component α1 and quadrature component β1; S4: Connect the voltage divider circuit, the compensation circuit and the calibrated multi-bit inductive voltage divider to the calibration circuit, keep the resistance of the third input resistor in the second state, obtain the differential voltage output by the lock-in amplifier to measure the calibration circuit, and the calculation formula of the second reading △2 of the lock-in amplifier is as follows: Then, the voltage division ratio k between the voltage division circuit and the compensation circuit is d The calculation formula is as follows: The actual voltage division ratio of the voltage division circuit and the compensation circuit is obtained by calculation.

Images