AC signal DC component detection circuit and inverter
The proposed circuit for DC component detection in AC signals uses a differential amplifier and RC low-pass filter to isolate and amplify the DC component, addressing precision issues in existing methods by simplifying the computational process and enhancing measurement accuracy.
Patent Information
- Application Number
- CN202421339828.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-12
- Publication Date
- 2025-07-15
- Estimated Expiration
- 2034-06-12
AI Technical Summary
In the prior art, the detection method of AC signal DC component is sampled by analog-to-digital converter and calculated by digital signal, resulting in low detection accuracy, complex operation and large errors.
Differential sampling and amplification circuit, second-order RC low-pass filtering circuit and subtraction circuit are used to directly extract the DC components in the AC signal through differential amplification, filtering and reference signal removal to avoid complex digital signal processing.
The detection accuracy of DC components is improved, data processing errors are reduced, and the accurate extraction of DC components in AC signals is achieved.
Smart Images
Figure CN223107908U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power electronics technology, and in particular, to an AC signal DC component detection circuit and an inverter. Background Art
[0002] In an application circuit, an AC signal is composed of sine waves. However, in some special cases, the AC signal may contain a certain DC component. The DC component is the "background value" below the AC power signal, that is, the offset value of the electrical signal at the zero point, which may be caused by factors such as bias voltage, non-linear elements, and capacitors and inductors. In the application scenario of a grid-connected photovoltaic inverter, if the DC component is too large, it will cause a series of adverse consequences such as transformer saturation in the substation, for example, energy consumption waste, circuit instability, etc. There are also requirements for the DC current output content in the industry. For example, the G83 regulation requires that the DC current output content be less than 20 mA, the AS4777 requires that the DC current output content be less than 5‰ of the output current, and the DK5940 requires less than 5‰ of the output current. Therefore, it is very necessary to detect the DC component of the AC signal.
[0003] The existing DC component detection method samples and converts the AC signal through an analog-to-digital converter, and calculates the DC component in the AC signal based on the converted digital signal. However, the sampling accuracy of this method is low, and the software operation in the DC component calculation process is complex, further increasing the error, resulting in a low detection accuracy of the DC component. Summary of the Utility Model
[0004] In view of this, the present utility model provides an AC signal DC component detection circuit, mainly aiming to solve the technical problem that in the existing detection of the DC component in the AC signal, the calculation of the DC component in the AC signal based on the digital signal is complex and has a large error, resulting in a low detection accuracy of the DC component.
[0005] To achieve the above object, according to one aspect of the present utility model, an AC signal DC component detection circuit is provided, including: a differential sampling and amplifying circuit, a second-order RC low-pass filter circuit, and a subtraction circuit;
[0006] The differential sampling and amplifying circuit is configured to receive the AC signal to be measured, superimpose a reference signal on the AC signal to be measured, and amplify the AC signal to be measured on which the reference signal is superimposed. The AC signal to be measured includes an AC component and a DC component;
[0007] The input end of the second-order RC low-pass filter circuit is connected to the output end of the differential sampling and amplifying circuit, and is configured to filter the AC component in the amplified AC signal to be measured and output the DC component;
[0008] The input end of the subtraction circuit is connected to the output end of the second-order RC low-pass filter circuit, and is used to remove the reference signal superimposed on the DC component and perform secondary amplification on the DC component after removing the reference signal, so as to determine the detection value of the DC component in the AC signal to be measured according to the DC component after secondary amplification.
[0009] Preferably, the differential sampling and amplifying circuit includes: a current limiting module, a first operational amplifier, a first RC parallel circuit and a second RC parallel circuit; the input end of the current limiting module is connected to the output end of the AC signal to be measured, the first output end is connected to the non-inverting input end of the first operational amplifier, and the second output end is connected to the inverting input end of the first operational amplifier; the first end of the first RC parallel circuit is connected to the reference signal, and the second end is connected to the non-inverting input end of the first operational amplifier; the first end of the second RC parallel circuit is connected to the inverting input end of the first operational amplifier, and the second end is connected to the output end of the first operational amplifier.
[0010] Preferably, the current limiting module includes a first current limiting resistor and a second current limiting resistor; the first end of the first current limiting resistor is connected to the first output end of the AC signal to be measured, and the second end is connected to the non-inverting input end of the first operational amplifier; the first end of the second current limiting resistor is connected to the second output end of the AC signal to be measured, and the second end is connected to the inverting input end of the first operational amplifier.
[0011] Preferably, the first RC parallel circuit includes a first filter resistor and a first filter capacitor connected in parallel, the first end of the first filter resistor and the first filter capacitor connected in parallel is connected to the reference signal, and the second end is connected to the non-inverting input end of the first operational amplifier; the second RC parallel circuit includes a second filter resistor and a second filter capacitor connected in parallel, the first end of the second filter resistor and the second filter capacitor connected in parallel is connected to the inverting input end of the first operational amplifier, and the second end is connected to the output end of the first operational amplifier.
[0012] Preferably, the second-order RC low-pass filter circuit includes a first low-pass filter module and a second low-pass filter module; the first low-pass filter module is connected in series with the second low-pass filter module; the input end of the first low-pass filter module is connected to the output end of the differential sampling and amplifying circuit, the output end is connected to the input end of the second low-pass filter module, and the output end of the second low-pass filter module is connected to the input end of the subtraction circuit.
[0013] Preferably, the first low-pass filtering module includes a first low-pass filtering resistor and a first low-pass filtering capacitor. The first end of the first low-pass filtering resistor is connected to the output end of the differential sampling and amplifying circuit, the second end is connected to the first end of the first low-pass filtering capacitor and the input end of the second low-pass filtering module, and the second end of the first low-pass filtering capacitor is grounded.
[0014] The second low-pass filtering module includes a second low-pass filtering resistor and a second low-pass filtering capacitor. The first end of the second low-pass filtering resistor is connected to the output end of the first low-pass filtering module, the second end is connected to the first end of the second low-pass filtering capacitor and the input end of the subtraction circuit, and the second end of the second low-pass filtering capacitor is grounded.
[0015] Preferably, the subtraction circuit includes: a second operational amplifier, a first subtraction resistor, and a second subtraction resistor; the non-inverting input end of the second operational amplifier is connected to the output end of the second-order RC low-pass filtering circuit, and the inverting input end is respectively connected to the first end of the first subtraction resistor and the first end of the second subtraction resistor; the second end of the first subtraction resistor is connected to a reference signal; the second end of the second subtraction resistor is connected to the output end of the second operational amplifier.
[0016] Preferably, the circuit further includes an attenuation circuit; the input end of the attenuation circuit is connected to the output end of the original AC signal, and the output end is connected to the input end of the differential sampling and amplifying circuit, for receiving the original AC signal and performing proportional attenuation on the original AC signal to obtain a to-be-detected AC signal that meets the signal detection range.
[0017] Preferably, the circuit further includes an analog-to-digital conversion module; the input end of the analog-to-digital conversion module is connected to the output end of the subtraction circuit, for receiving the DC component after secondary amplification and determining the detection value of the DC component in the to-be-detected AC signal based on the DC component after secondary amplification.
[0018] According to another aspect of the present invention, an inverter is provided, and the inverter includes the above AC signal DC component detection circuit.
[0019] An AC signal DC component detection circuit and an inverter provided by the present utility model can amplify the AC signal to be detected through a differential sampling and amplification circuit, and filter out the AC component in the AC signal based on a second-order RC low-pass filter circuit, only retaining the DC component part in the AC signal. At the same time, the reference signal superimposed on the DC component is removed through a subtraction circuit and amplified again, so that the output DC component meets the signal detection range to determine the detection value of the DC component in the AC signal to be detected. Through the above circuit, the extraction of the DC component in the AC signal is realized, avoiding complex processing and operations on digital signals containing DC components and AC components, reducing data processing errors, and thus improving the accuracy of DC component extraction.
[0020] The above description is only an overview of the technical solution of the present utility model. In order to be able to understand the technical means of the present utility model more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present utility model more obvious and understandable, the following specific embodiments of the present utility model are specifically given. Brief Description of the Drawings
[0021] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present utility model. And throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:
[0022] Figure 1 Shows a block diagram of the structure composition of an AC signal DC component detection circuit provided by an embodiment of the present utility model;
[0023] Figure 2 Shows a schematic diagram of the structure of an AC signal DC component detection circuit provided by an embodiment of the present utility model;
[0024] Figure 3 Shows a block diagram of the structure composition of another AC signal DC component detection circuit provided by an embodiment of the present utility model. Detailed Description of the Embodiments
[0025] The present utility model will be described in detail below with reference to the drawings and in combination with the embodiments. It should be noted that, without conflict, the embodiments in the present utility model and the features in the embodiments can be combined with each other.
[0026] To further elaborate on the technical means and effects adopted by the present utility model to achieve the intended utility model purpose, the following will, in conjunction with the accompanying drawings and preferred embodiments, elaborate in detail on the specific implementation manners, structures, features and their effects of the application according to the present utility model. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.
[0027] The following will be described in conjunction with Figure 1 , Figure 2 and Figure 3 an AC signal DC component detection circuit according to some embodiments of the present utility model.
[0028] In one embodiment, as Figure 1 shown, an AC signal DC component detection circuit is provided. The circuit includes a differential sampling and amplifying circuit 10, a second-order RC low-pass filter circuit 20, and a subtraction circuit 30. Among them, the differential sampling and amplifying circuit 10 can be used to receive the AC signal to be measured, superimpose a reference signal on the AC signal to be measured, and amplify the AC signal to be measured superimposed with the reference signal. Among them, the AC signal to be measured includes an AC component and a DC component. The input end of the second-order RC low-pass filter circuit 20 is connected to the output end of the differential sampling and amplifying circuit 10, and is used to filter the AC component in the amplified AC signal to be measured and output the DC component. The input end of the subtraction circuit 30 is connected to the output end of the second-order RC low-pass filter circuit 20, and is used to remove the reference signal superimposed on the DC component, and perform secondary amplification on the DC component after removing the reference signal, so as to determine the detection value of the DC component in the AC signal to be measured based on the DC component after secondary amplification.
[0029] In the above embodiments, the input end of the differential sampling and amplifying circuit is connected to the output end of the AC signal to be measured, the output end of the differential sampling and amplifying circuit is connected to the input end of the second-order RC low-pass filter circuit, the output end of the second-order RC low-pass filter circuit is connected to the input end of the subtraction circuit, and the final DC component is output through the output end of the subtraction circuit to realize the extraction of the DC component in the AC signal. Among them, the differential sampling and amplifying circuit can be used to superimpose a reference signal on the AC signal to be measured and amplify the AC signal to be measured superimposed with the reference signal. The second-order RC low-pass filter circuit can be used to filter the AC component in the amplified AC signal to be measured and output the DC component. Among them, the reference signal can be a 1.5V reference voltage or can be customized according to the actual application scenario. The operational amplifier is powered by a single power supply, and the input differential signal may be positive or negative. By superimposing a 1.5V voltage, the output distortion of the operational amplifier can be avoided, ensuring that the subsequent second-order RC low-pass filter circuit can effectively extract the DC component in the AC signal. The subtraction circuit can be used to remove the reference signal superimposed on the DC component and amplify the DC component after removing the reference signal. Removing the reference signal superimposed in the differential sampling and amplifying circuit can ensure the accuracy of the DC component. Further, amplifying the DC component after removing the reference signal can make the output DC component meet the sampling range of the subsequent analog-to-digital converter to determine the magnitude of the DC component, so as to accurately determine the detection value of the DC component in the AC signal to be measured.
[0030] Working principle: When the circuit is working normally, after receiving the AC signal to be measured, the differential sampling and amplifying circuit superimposes the reference signal and differentially amplifies the AC signal after superimposing the reference signal, and then performs low-pass filtering on the amplified AC signal through the second-order RC low-pass filter circuit. By superimposing the reference signal, the output distortion of the operational amplifier can be avoided, ensuring that the subsequent second-order RC low-pass filter circuit can effectively extract the DC component in the AC signal terminal. In addition, since the AC signal to be measured contains a DC component and an AC component, the AC component in the AC signal can be filtered out through low-pass filtering, and only the DC component part is retained, completing the extraction of the DC component in the AC signal, and then outputting the DC component. Further, since a reference signal is superimposed on the AC signal to be measured in the differential sampling and amplifying circuit, the DC component output by the second-order RC low-pass filter circuit is not equal to the DC component in the AC signal to be measured. Therefore, the subtraction current is used to subtract the reference signal superimposed on the DC component to restore the DC component in the AC signal to be measured. The above circuit can reduce the computational workload of digital signal processing to a certain extent, avoid the error problem of calculating the DC component from the digital signal containing the AC component and the DC component, directly filter out the AC component in the AC signal to be measured from the analog level, extract the DC component, thereby effectively reducing the data processing volume of extracting the DC component from the AC signal and improving the accuracy of DC component extraction.
[0031] It should be noted that the circuit function of the AC signal DC component detection circuit provided in this embodiment is mainly realized through the circuit connection relationship between each circuit module, rather than relying on the program module in a certain circuit module. In addition, each circuit module in the AC signal DC component detection circuit can be implemented by an analog circuit or a digital circuit. For the circuit module that can implant a program module, the implementation of its module function can be achieved through the program module provided by the prior art.
[0032] The AC signal DC component detection circuit proposed by the present invention can amplify the AC signal to be detected through a differential sampling and amplification circuit, and filter out the AC component in the AC signal based on a second-order RC low-pass filter circuit, only retaining the DC component part in the AC signal. At the same time, the reference signal superimposed on the DC component is removed through a subtraction circuit and amplified twice to make the output DC component meet the signal detection range, so as to determine the detection value of the DC component in the AC signal to be measured. Through the above circuit, the extraction of the DC component in the AC signal is realized, avoiding complex processing and operations on the digital signal containing DC and AC components, reducing the data processing error, and thus improving the accuracy of DC component extraction.
[0033] In one embodiment, the differential sampling and amplification circuit in the above AC signal DC component detection circuit includes: a current limiting module, a first operational amplifier, a first RC parallel circuit, and a second RC parallel circuit; the input end of the current limiting module is connected to the output end of the AC signal to be measured, the first output end is connected to the non-inverting input end of the first operational amplifier, and the second output end is connected to the inverting input end of the first operational amplifier; the first end of the first RC parallel circuit is connected to the reference signal, and the second end is connected to the non-inverting input end of the first operational amplifier; the first end of the second RC parallel circuit is connected to the inverting input end of the first operational amplifier, and the second end is connected to the output end of the first operational amplifier.
[0034] Specifically, the current limiting module can be used to limit the current magnitude of the input signal, preventing problems such as damage to the operational amplifier or circuit instability caused by excessive signal current. At the same time, the current limiting module can also be used to improve the anti-interference ability, reduce the noise interference in the circuit, and improve the purity of the signal. The first RC parallel circuit and the second RC parallel circuit can be used to filter out high-frequency noise and clutter in the input signal, ensuring the accuracy and stability of the signal. The first operational amplifier can amplify the alternating current signal to be measured that does not meet the sampling range of the analog-to-digital converter and improve the accuracy of subsequent low-frequency filtering. By introducing the current limiting module, the first operational amplifier, the first RC parallel circuit, and the second RC parallel circuit in this embodiment, the stability and reliability of the input of the alternating current signal to be measured can be effectively improved, thereby optimizing the performance of the alternating current signal DC component detection circuit.
[0035] In one embodiment, as Figure 2 shown, the above-mentioned current limiting module includes a first current limiting resistor R15 and a second current limiting resistor R16; the first end of the first current limiting resistor R15 is connected to the first output end of the alternating current signal to be measured, and the second end is connected to the non-inverting input terminal of the first operational amplifier U1; the first end of the second current limiting resistor R16 is connected to the second output end of the alternating current signal to be measured, and the second end is connected to the inverting input terminal of the first operational amplifier U1.
[0036] Specifically, when the alternating current signal to be measured is input into the alternating current signal DC component detection circuit, the first current limiting resistor R15 and the second current limiting resistor R16 can effectively limit the current magnitude passing through the first operational amplifier U1, preventing damage to the operational amplifier or other circuit components due to excessive signal current. At the same time, by selecting appropriate resistance values, the first current limiting resistor R15 and the second current limiting resistor R16 can also reduce the common-mode noise signal and improve the purity of the signal. In practical applications, in order to obtain the best current limiting effect, the resistance values of R1 and R2 are usually set to be equal. For example, 7.5 Kohms. Such a design can simplify the circuit design and reduce the manufacturing cost while ensuring current stability.
[0037] In one embodiment, as Figure 2 shown, the first RC parallel circuit includes a first filter resistor R17 and a first filter capacitor C8 connected in parallel. The first end of the first filter resistor R17 and the first filter capacitor C68 connected in parallel is connected to the reference signal, and the second end is connected to the non-inverting input terminal of the first operational amplifier U1; the second RC parallel circuit includes a second filter resistor R18 and a second filter capacitor C7 connected in parallel. The first end of the second filter resistor R18 and the second filter capacitor C7 connected in parallel is connected to the inverting input terminal of the first operational amplifier U1, and the second end is connected to the output terminal of the first operational amplifier U1.
[0038] Specifically, the first filtering resistor R17 and the first filtering capacitor C6 can be used to filter out high-frequency noise and clutter in the input AC signal to be measured, ensuring the accuracy and stability of the signal input to the non-inverting input terminal of the first operational amplifier U1. The second filtering resistor R18 and the second filtering capacitor C7 can be used to filter out high-frequency noise and clutter in the input AC signal to be measured, ensuring the accuracy and stability of the signal input to the inverting input terminal of the first operational amplifier U1. The above circuit can ensure the purity of the AC signal to be measured before amplification processing, thereby improving the accuracy of signal amplification. In practical applications, to make the filtering effects of the signals input to the first operational amplifier U1 the same, the resistance values of the first filtering resistor R17 and the second filtering resistor R18 are equal, and the capacitance values of the first filtering capacitor C6 and the second filtering capacitor C7 are equal.
[0039] In one embodiment, the second-order RC low-pass filtering circuit in the AC signal DC component detection circuit includes a first low-pass filtering module and a second low-pass filtering module; the first low-pass filtering module is connected in series with the second low-pass filtering module; the input terminal of the first low-pass filtering module is connected to the output terminal of the differential sampling and amplification circuit, the output terminal is connected to the input terminal of the second low-pass filtering module, and the output terminal of the second low-pass filtering module is connected to the input terminal of the subtraction circuit.
[0040] Specifically, the first low-pass filtering module can be used to perform a first-order filtering on the AC component in the amplified AC signal to be measured; the second low-pass filtering module can be used to perform a second-order filtering on the AC component in the AC signal after the first-order filtering, so as to completely filter out the AC component in the AC signal to be measured and only retain the DC component to obtain a pure DC component. In this embodiment, by introducing the first low-pass filtering module and the second low-pass filtering module, the accuracy of AC component filtering is ensured, the accuracy of the DC component is improved, and thus the accuracy of determining the detection value of the DC component in the AC signal to be measured is improved.
[0041] In one embodiment, as Figure 2 shown, the above-mentioned first low-pass filtering module includes a first low-pass filtering resistor R19 and a first low-pass filtering capacitor C8. The first end of the first low-pass filtering resistor R19 is connected to the output terminal of the differential sampling and amplification circuit, the second end is connected to the first end of the first low-pass filtering capacitor C8 and the input terminal of the second low-pass filtering module, and the second end of the first low-pass filtering capacitor C8 is grounded; the second low-pass filtering module includes a second low-pass filtering resistor R20 and a second low-pass filtering capacitor C9. The first end of the second low-pass filtering resistor R20 is connected to the output terminal of the first low-pass filtering module, the second end is connected to the first end of the second low-pass filtering capacitor C9 and the input terminal of the subtraction circuit, and the second end of the second low-pass filtering capacitor is grounded.
[0042] Specifically, the first low-pass filter resistor R19 and the first low-pass filter capacitor C8 can be used to perform a first-order filtering on the AC component in the amplified AC signal to be measured; the second low-pass filter resistor R20 and the second low-pass filter capacitor C9 can be used to perform a second-order filtering on the AC component in the AC signal after the first-order filtering, so as to completely filter out the AC component in the AC signal to be measured and retain the pure DC component, ensuring that only the DC component can be sampled in the subsequent DC component sampling, thereby improving the accuracy of DC component detection. In practical applications, in order to obtain the best low-pass filtering effect, the resistance value of the first filter resistor R19 is less than that of the second filter resistor R20; the capacitances of the first filter capacitor C8 and the second filter capacitor C9 are equal.
[0043] In one embodiment, as Figure 2 shown, the subtraction circuit includes: a second operational amplifier U2, a first subtraction resistor R21, and a second subtraction resistor R22; the non-inverting input terminal of the second operational amplifier U2 is connected to the output terminal of the second-order RC low-pass filter circuit, and the inverting input terminal is respectively connected to the first end of the first subtraction resistor R21 and the first end of the second subtraction resistor R22; the second end of the first subtraction resistor R21 is connected to the reference signal, and the second end of the second subtraction resistor R22 is connected to the output terminal of the second operational amplifier U2.
[0044] Specifically, the second operational amplifier U2 can be used to perform a subtraction operation on the DC component to remove the 1.5V reference voltage superimposed on the DC component previously, and at the same time, perform a secondary amplification on the DC component to make the DC component meet the subsequent signal sampling range, ensuring the accuracy of sampling. By configuring reasonable resistance values for the first subtraction resistor R21 and the second subtraction resistor R22, the signal amplitude difference between the inverting input terminal and the non-inverting input terminal of the second operational amplifier U2 can be adjusted, realizing flexible adjustment of the voltage magnitude of the DC component output by the second operational amplifier U2.
[0045] In one embodiment, as Figure 3 shown, the AC signal DC component detection circuit further includes an attenuation circuit 40; the input terminal of the attenuation circuit 40 is connected to the output terminal of the original AC signal, and the output terminal is connected to the input terminal of the differential sampling and amplification circuit, and is used to receive the original AC signal and perform a proportional attenuation on the original AC signal to obtain the AC signal to be measured that meets the signal detection range.
[0046] Specifically, in practical application scenarios, the attenuation circuit can be an attenuator or an attenuation circuit built by an operational amplifier, which can attenuate or amplify the original AC signal to meet the requirements of the subsequent circuit for the signal detection range. For example, when the original AC signal is a large current signal, it can be used to perform a proportional attenuation on the original AC signal; when the original AC signal is a signal collected by a sensor, it can be used to perform a proportional amplification on the original AC signal.
[0047] In one embodiment, as Figure 3 shown, the AC signal DC component detection circuit further includes an analog-to-digital conversion module 50; the input end of the analog-to-digital conversion module 50 is connected to the output end of the subtraction circuit, and is used to receive the DC component after secondary amplification, and determine the detection value of the DC component in the AC signal to be measured based on the DC component after secondary amplification.
[0048] Specifically, the analog-to-digital conversion module can be used to receive the DC component, convert the DC component into a digital signal, and calculate how much the DC component in the actual AC signal (voltage or current signal) is through a sampling transfer function. Among them, the sampling transfer function is a common function known to those skilled in the art and is not a unique technical feature of the present invention. In practical applications, in order to ensure the effect of DC component acquisition, the analog-to-digital conversion module can include a digital signal processor (DSP: digital singnal processor). The AD interface of the DSP is connected to the output end of the subtraction circuit to complete the acquisition of the DC component.
[0049] The AC signal DC component detection circuit proposed by the present invention can amplify the AC signal to be detected through a differential sampling and amplification circuit, and filter out the AC component in the AC signal based on a second-order RC low-pass filter circuit, leaving only the DC component part in the AC signal. At the same time, the reference signal superimposed on the DC component is removed through a subtraction circuit and amplified twice to make the output DC component meet the signal detection range, so as to determine the detection value of the DC component in the AC signal to be measured. Through the above circuit, the extraction of the DC component in the AC signal is realized, the complex processing and operation of the digital signal containing the DC component and the AC component are avoided, the data processing error is reduced, and thus the accuracy of the DC component extraction is improved. Specific embodiments:
[0051] As Figure 1As shown, an AC signal DC component detection circuit is provided. The circuit includes a differential sampling and amplification circuit 10, a second-order RC low-pass filter circuit 20, and a subtraction circuit 30. Among them, the differential sampling and amplification circuit 10 can be used to receive the AC signal to be measured, superimpose a reference signal on the AC signal to be measured, and amplify the AC signal to be measured superimposed with the reference signal. Among them, the AC signal to be measured includes an AC component and a DC component. The input end of the second-order RC low-pass filter circuit 20 is connected to the output end of the differential sampling and amplification circuit 10, and is used to filter the AC component in the amplified AC signal to be measured and output the DC component. The input end of the subtraction circuit 30 is connected to the output end of the second-order RC low-pass filter circuit 20, and is used to remove the reference signal superimposed on the DC component and amplify the DC component after removing the reference signal twice, so as to determine the detection value of the DC component in the AC signal to be measured according to the DC component amplified twice.
[0052] In one embodiment, the differential sampling and amplification circuit in the above AC signal DC component detection circuit includes: a current limiting module, a first operational amplifier, a first RC parallel circuit, and a second RC parallel circuit; as Figure 2 shown, the above current limiting module includes a first current limiting resistor R15 and a second current limiting resistor R16; the first end of the first current limiting resistor R15 is connected to the first output end of the AC signal to be measured, and the second end is connected to the non-inverting input end of the first operational amplifier U1; the first end of the second current limiting resistor R16 is connected to the second output end of the AC signal to be measured, and the second end is connected to the inverting input end of the first operational amplifier U1. The first RC parallel circuit includes a first filter resistor R17 and a first filter capacitor C8 connected in parallel. The first end of the first filter resistor R17 and the first filter capacitor C68 connected in parallel is connected to the reference signal, and the second end is connected to the non-inverting input end of the first operational amplifier U1; the second RC parallel circuit includes a second filter resistor R18 and a second filter capacitor C7. The first end of the second filter resistor R18 and the second filter capacitor C7 connected in parallel is connected to the inverting input end of the first operational amplifier U1, and the second end is connected to the output end of the first operational amplifier U1.
[0053] In this embodiment, the second-order RC low-pass filter circuit in the AC signal DC component detection circuit includes a first low-pass filter module and a second low-pass filter module. As Figure 2As shown in the figure, the first low-pass filtering module includes a first low-pass filtering resistor R19 and a first low-pass filtering capacitor C8. The first end of the first low-pass filtering resistor R19 is connected to the output end of the differential sampling and amplifying circuit, and the second end is connected to the first end of the first low-pass filtering capacitor C8 and the input end of the second low-pass filtering module. The second end of the first low-pass filtering capacitor C8 is grounded. The second low-pass filtering module includes a second low-pass filtering resistor R20 and a second low-pass filtering capacitor C9. The first end of the second low-pass filtering resistor R20 is connected to the output end of the first low-pass filtering module, and the second end is connected to the first end of the second low-pass filtering capacitor C9 and the input end of the subtraction circuit. The second end of the second low-pass filtering capacitor is grounded.
[0054] In this embodiment, as Figure 2 shown, the subtraction circuit includes: a second operational amplifier U2, a first subtraction resistor R21, and a second subtraction resistor R22. The non-inverting input end of the second operational amplifier U2 is connected to the output end of the second-order RC low-pass filtering circuit, and the inverting input end is respectively connected to the first end of the first subtraction resistor R21 and the first end of the second subtraction resistor R22. The second end of the first subtraction resistor R21 is connected to a reference signal, and the second end of the second subtraction resistor R22 is connected to the output end of the second operational amplifier U2.
[0055] In this embodiment, as Figure 3 shown, the AC signal DC component detection circuit further includes an attenuation circuit 40. The input end of the attenuation circuit 40 is connected to the output end of the original AC signal, and the output end is connected to the input end of the differential sampling and amplifying circuit, and is used to receive the original AC signal and perform proportional attenuation on the original AC signal to obtain a to-be-detected AC signal that meets the signal detection interval.
[0056] In this embodiment, as Figure 3 shown, the AC signal DC component detection circuit further includes an analog-to-digital conversion module 50. The input end of the analog-to-digital conversion module 50 is connected to the output end of the subtraction circuit, and is used to receive the DC component after secondary amplification and determine the detection value of the DC component in the to-be-detected AC signal based on the DC component after secondary amplification.
[0057] According to another aspect of the present invention, an inverter is provided, and the inverter includes the above-mentioned AC signal DC component detection circuit.
[0058] An inverter provided by the present utility model. The DC component detection circuit of the AC signal therein can amplify the AC signal to be detected through a differential sampling and amplification circuit, and filter out the AC component in the AC signal based on a second-order RC low-pass filter circuit, only retaining the DC component part in the AC signal. At the same time, the reference signal superimposed in the DC component is removed through a subtraction circuit and amplified twice, so that the output DC component meets the signal detection range to determine the detection value of the DC component in the AC signal to be measured. Through the above circuit, the extraction of the DC component in the AC signal is realized, avoiding complex processing and operations on digital signals containing DC components and AC components, reducing data processing errors, and thus improving the accuracy of DC component extraction.
[0059] The above are only the preferred embodiments of the present utility model and are not used to limit the present utility model. For those skilled in the art, the present utility model can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.
Claims
1. A DC component detection circuit for AC signals, characterized in that, Comprising: A differential sampling amplifier circuit, a second-order RC low-pass filter circuit, and a subtraction circuit; The differential sampling amplifier circuit is configured to receive a to-be-detected AC signal, superimpose a reference signal on the to-be-detected AC signal, and amplify the to-be-detected AC signal superimposed with the reference signal, wherein the to-be-detected AC signal includes an AC component and a DC component; The input end of the second-order RC low-pass filter circuit is connected to the output end of the differential sampling amplifier circuit, and is configured to filter the AC component in the amplified to-be-detected AC signal and output a DC component; The input end of the subtraction circuit is connected to the output end of the second-order RC low-pass filter circuit, and is configured to remove the reference signal superimposed on the DC component, and perform secondary amplification on the DC component after removing the reference signal, so as to determine a detection value of the DC component in the to-be-detected AC signal according to the DC component after secondary amplification.
2. The AC signal DC component detection circuit according to claim 1, wherein The differential sampling amplifier circuit includes: a current-limiting module, a first operational amplifier, a first RC parallel circuit, and a second RC parallel circuit; The input end of the current-limiting module is connected to the output end of the to-be-detected AC signal, the first output end is connected to the non-inverting input end of the first operational amplifier, and the second output end is connected to the inverting input end of the first operational amplifier; The first end of the first RC parallel circuit is connected to the reference signal, and the second end is connected to the non-inverting input end of the first operational amplifier; The first end of the second RC parallel circuit is connected to the inverting input end of the first operational amplifier, and the second end is connected to the output end of the first operational amplifier.
3. The AC signal DC component detection circuit according to claim 2, wherein The current-limiting module includes a first current-limiting resistor and a second current-limiting resistor; The first end of the first current-limiting resistor is connected to the first output end of the to-be-detected AC signal, and the second end is connected to the non-inverting input end of the first operational amplifier; The first end of the second current-limiting resistor is connected to the second output end of the to-be-detected AC signal, and the second end is connected to the inverting input end of the first operational amplifier.
4. The AC signal DC component detection circuit according to claim 2 or 3, wherein The first RC parallel circuit includes a first filter resistor and a first filter capacitor connected in parallel, and the first end of the parallel connection of the first filter resistor and the first filter capacitor is connected to the reference signal, and the second end is connected to the non-inverting input end of the first operational amplifier; The second RC parallel circuit includes a second filter resistor and a second filter capacitor connected in parallel, and the first end of the parallel connection of the second filter resistor and the second filter capacitor is connected to the inverting input end of the first operational amplifier, and the second end is connected to the output end of the first operational amplifier.
5. The AC signal DC component detection circuit according to claim 1, characterized in that The second-order RC low-pass filter circuit includes a first low-pass filter module and a second low-pass filter module; The first low-pass filter module is connected in series with the second low-pass filter module; The input end of the first low-pass filter module is connected to the output end of the differential sampling amplifier circuit, the output end is connected to the input end of the second low-pass filter module, and the output end of the second low-pass filter module is connected to the input end of the subtraction circuit.
6. The AC signal DC component detection circuit according to claim 5, wherein the first low-pass filter module includes a first low-pass filter resistor and a first low-pass filter capacitor. The first end of the first low-pass filter resistor is connected to the output end of the differential sampling and amplifying circuit, the second end is connected to the first end of the first low-pass filter capacitor and the input end of the second low-pass filter module, and the second end of the first low-pass filter capacitor is grounded; the second low-pass filter module includes a second low-pass filter resistor and a second low-pass filter capacitor. The first end of the second low-pass filter resistor is connected to the output end of the first low-pass filter module, the second end is connected to the first end of the second low-pass filter capacitor and the input end of the subtraction circuit, and the second end of the second low-pass filter capacitor is grounded.
7. The AC signal DC component detection circuit according to claim 1, characterized in that, The subtraction circuit includes: a second operational amplifier, a first subtraction resistor and a second subtraction resistor; the non-inverting input end of the second operational amplifier is connected to the output end of the second-order RC low-pass filter circuit, and the inverting input end is respectively connected to the first end of the first subtraction resistor and the first end of the second subtraction resistor; the second end of the first subtraction resistor is connected to a reference signal, and the second end of the second subtraction resistor is connected to the output end of the second operational amplifier.
8. The AC signal DC component detection circuit according to claim 1, characterized in that, The circuit further includes an attenuation circuit; the input end of the attenuation circuit is connected to the output end of the original AC signal, and the output end is connected to the input end of the differential sampling and amplifying circuit, for receiving the original AC signal and performing proportional attenuation on the original AC signal to obtain a to-be-detected AC signal that meets the signal detection range.
9. The AC signal DC component detection circuit according to claim 1, wherein The circuit further includes an analog-to-digital conversion module; the input end of the analog-to-digital conversion module is connected to the output end of the subtraction circuit, for receiving the DC component after secondary amplification and determining the detection value of the DC component in the to-be-detected AC signal according to the DC component after secondary amplification.
10. An inverter, characterized in that, The inverter includes the AC signal DC component detection circuit according to any one of claims 1-9.