Sampling circuit based on electronic voltage transformer and electronic device

Abstract

A kind of sampling circuit based on electronic voltage transformer and electronic equipment, belong to power electronics field, by electronic voltage transformer to the AC to be measured is detected, to output first AC detection signal;Impedance conversion circuit carries out impedance conversion to first AC detection signal, to output second AC detection signal;AC-DC conversion circuit converts second AC detection signal, to output first DC detection signal;High resistance isolation circuit carries out high resistance isolation to first DC detection signal, to output second DC detection signal;Single-ended conversion circuit converts the second DC detection signal, to output single-ended sampling signal;Follower carries out following to sampling signal, to output following sampling signal;To enhance the load capacity, and simplify circuit, reduce cost.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to a sampling circuit and electronic device based on an electronic voltage transformer. Background Technology

[0002] With the continuous development of smart grids, electronic voltage transformers, due to their small size, low cost, resistance to external magnetic interference, and core saturation, are gradually becoming more common in new smart grid equipment. Currently, the most common type of electronic voltage transformer is the "resistive-capacitive voltage divider" type. Through continuous technological updates, this type of electronic voltage transformer has basically met application requirements in terms of size and accuracy. However, its resistive-capacitive voltage divider topology determines its non-isolation and weak load-carrying capacity.

[0003] The relevant sampling circuit based on electronic voltage transformers uses isolation amplifier chips for isolation. However, the isolation amplifier chip circuit is complex and expensive, and the relevant sampling circuit based on electronic voltage transformers cannot solve the problem of weak load-carrying capacity.

[0004] Therefore, the related sampling circuits based on electronic voltage transformers have weak load-carrying capacity, complex circuitry, and high cost. Utility Model Content

[0005] The purpose of this application is to provide a sampling circuit and image sensor based on an electronic voltage transformer, aiming to solve the problems of weak load capacity, complex circuit and high cost of related sampling circuits based on electronic voltage transformers.

[0006] This application provides a sampling circuit based on an electronic voltage transformer, including:

[0007] An electronic voltage transformer is used to detect the AC current under test and output a first AC detection signal.

[0008] An impedance transformation circuit, connected to the electronic voltage transformer, is used to perform impedance transformation on the first AC detection signal to output a second AC detection signal.

[0009] An AC / DC conversion circuit, connected to the impedance transformation circuit, is used to convert the second AC detection signal to output a first DC detection signal;

[0010] A high-impedance isolation circuit, connected to the AC / DC conversion circuit, is used to provide high-impedance isolation for the first DC detection signal so as to output a second DC detection signal;

[0011] A single-ended conversion circuit, connected to the high-impedance isolation circuit, is used to convert the double-ended second DC detection signal to output a single-ended sampling signal;

[0012] A follower, connected to the single-ended conversion circuit, is used to follow the sampled signal to output the followed sampled signal.

[0013] This utility model embodiment also provides an electronic device, which includes the above-described sampling circuit based on an electronic voltage transformer.

[0014] The beneficial effects of this utility model embodiment compared with the prior art are: since a high-impedance isolation circuit is used for isolation, there is no need to configure an isolation amplifier chip, the circuit is simple and the cost is low; the use of a follower to follow the sampled signal enhances the load capacity. Attached Figure Description

[0015] To more clearly illustrate the technical utility model in the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A schematic diagram of a sampling circuit based on an electronic voltage transformer provided in an embodiment of this application;

[0017] Figure 2 A schematic diagram of another structure of a sampling circuit based on an electronic voltage transformer provided in an embodiment of this application;

[0018] Figure 3 A schematic diagram of another structure of a sampling circuit based on an electronic voltage transformer provided in an embodiment of this application;

[0019] Figure 4 A schematic diagram of another structure of a sampling circuit based on an electronic voltage transformer provided in an embodiment of this application;

[0020] Figure 5 A schematic diagram of another structure of a sampling circuit based on an electronic voltage transformer provided in an embodiment of this application;

[0021] Figure 6 This is a partial example circuit diagram of a sampling circuit based on an electronic voltage transformer provided in an embodiment of this application. Detailed Implementation

[0022] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0023] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0024] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0026] Figure 1 A schematic diagram of a sampling circuit based on an electronic voltage transformer according to a preferred embodiment of this application is shown. For ease of explanation, only the parts relevant to this embodiment are shown, and are described in detail below:

[0027] The above-mentioned sampling circuit based on electronic voltage transformer includes electronic voltage transformer 00, impedance transformation circuit 10, AC / DC conversion circuit 20, high-impedance isolation circuit 30, single-ended conversion circuit 40, and follower 50.

[0028] The electronic voltage transformer 00 is used to detect the AC current under test and output a first AC detection signal.

[0029] Impedance transformation circuit 10 is connected to electronic voltage transformer 00 and is used to perform impedance transformation on the first AC detection signal to output the second AC detection signal.

[0030] The AC / DC conversion circuit 20 is connected to the impedance transformation circuit 10 and is used to convert the second AC detection signal to output the first DC detection signal.

[0031] The high-impedance isolation circuit 30 is connected to the AC-DC conversion circuit 20 and is used to provide high-impedance isolation for the first DC detection signal so as to output the second DC detection signal.

[0032] The single-ended conversion circuit 40 is connected to the high-impedance isolation circuit 30 and is used to convert the double-ended second DC detection signal to output a single-ended sampling signal.

[0033] Follower 50, connected to single-ended conversion circuit 40, is used to follow the sampled signal to output the followed sampled signal.

[0034] It should be noted that the negative terminal of the AC power under test, the negative terminal of the first DC detection signal, the negative terminal of the first AC detection signal, and the negative terminal of the second AC detection signal can be connected to the signal ground, and the negative terminal of the sampling signal can be connected to the power supply ground.

[0035] like Figure 2 As shown, the sampling circuit based on the electronic voltage transformer also includes a bandpass filter circuit 60.

[0036] A bandpass filter circuit 60 is connected between the impedance transformation circuit 10 and the AC-DC conversion circuit 20. It is used to perform bandpass filtering on the second AC detection signal to output the bandpass filtered second AC detection signal.

[0037] The AC / DC conversion circuit 20 is specifically used to convert the second AC detection signal after bandpass filtering to output the first DC detection signal.

[0038] The above technical solution filters out the DC component of the second AC detection signal and the AC interference signal of the second AC detection signal, thereby improving the sampling accuracy of the sampling circuit based on the electronic voltage transformer.

[0039] like Figure 3 As shown, the sampling circuit based on the electronic voltage transformer also includes a low-pass filter circuit 70.

[0040] The low-pass filter circuit 70 is connected to the follower 50 and is used to perform low-pass filtering on the sampled signal after following, so as to output the low-pass filtered sampled signal.

[0041] The above technical solution filters out interference signals in the sampled signal and improves the sampling accuracy of the sampling circuit based on the electronic voltage transformer.

[0042] like Figure 4 As shown, the sampling circuit based on the electronic voltage transformer also includes a protection circuit 80.

[0043] The protection circuit 80 is connected between the electronic voltage transformer 00 and the impedance transformation circuit 10. It is used to perform electromagnetic compatibility (EMC) protection on the first AC detection signal so as to output the first AC detection signal after EMC protection.

[0044] The impedance transformation circuit 10 is specifically used to transform the impedance of the first AC detection signal after EMC protection in order to output the second AC detection signal.

[0045] The above technical solution provides EMC protection for the first AC detection signal, resisting interference from the external electromagnetic environment.

[0046] like Figure 5 As shown, the sampling circuit based on the electronic voltage transformer also includes a control circuit 90, an isolation module 100, and a switching circuit 110.

[0047] The control circuit 90, connected to the conversion circuit, is used to receive the sampling signal, compare the voltage of the sampling signal with at least one reference voltage, determine the target voltage range of the sampling signal based on the comparison result, and output a control signal based on the target voltage range.

[0048] The isolation module 100 is connected to the control circuit 90 and is used to isolate the control signal so as to output the isolated control signal.

[0049] The switching circuit 110 is connected to the isolation module 100 and is used to adjust the gain of the AC-DC conversion circuit 20 in response to the access of the isolated control signal, so that the adjusted AC-DC conversion circuit 20 converts the second AC detection signal to output the adjusted first DC detection signal.

[0050] The high-impedance isolation circuit 30 is also used to provide high-impedance isolation for the regulated first DC detection signal so as to output the regulated second DC detection signal.

[0051] The single-ended conversion circuit 40 is also used to convert the adjusted double-ended second DC detection signal to output the adjusted single-ended sampling signal;

[0052] Follower 50, connected to single-ended conversion circuit 40, is used to follow the regulated sampling signal and output the followed sampling signal to control circuit 90.

[0053] The above technical solution allows for adjustment of the gain of the AC / DC conversion circuit 20 to select a suitable range for sampling, thereby improving the accuracy and flexibility of the sampling circuit based on the electronic voltage transformer and enriching the product's functionality.

[0054] Figure 6The illustration shows a partial example circuit structure of a sampling circuit based on an electronic voltage transformer provided by an embodiment of the present invention. For ease of explanation, only the parts related to the embodiment of the present invention are shown, and are described in detail below:

[0055] The control circuit 90 includes a microprocessor U1;

[0056] The analog-to-digital converter (ADC) terminal of the microprocessor U1 forms the input terminal of the control circuit 90 and is connected to the conversion circuit to receive the sampling signal; the first general-purpose input / output terminal P1.0 and the second general-purpose input / output terminal P1.1 of the microprocessor U1 form the output terminal of the control circuit 90 and are connected to the isolation module 100 to output the control signal.

[0057] The AC / DC conversion circuit 20 includes a first operational amplifier U2, a first capacitor C1, a first resistor R1, a second resistor R2, and a third resistor R3;

[0058] The positive power supply terminal V+ of the first operational amplifier U2 is connected to the positive power supply V1+, and the negative power supply terminal V- of the first operational amplifier U2 is connected to the negative power supply V1-. The inverting input terminal of the first operational amplifier U2 and the first end of the third resistor R3 are connected to form the input terminal of the AC-DC conversion circuit 20, which is connected to the first common terminal and the second common terminal of the impedance transformation circuit 10 and the switching circuit 110 to receive the second AC detection signal. The non-inverting input terminal of the first operational amplifier U2 and the first end of the first capacitor C1 are connected to form the reference voltage terminal of the AC-DC conversion circuit 20 to receive the reference voltage. The first end of the first resistor R1 is connected to the first normally closed terminal of the switching circuit 110, and the first end of the second resistor R2 is connected to the second normally closed terminal of the switching circuit 110. The output terminal of the first operational amplifier U2, the second end of the first resistor R1, the second end of the second resistor R2, and the second end of the third resistor R3 are connected to form the output terminal of the AC-DC conversion circuit 20, which is connected to the high-impedance isolation circuit 30 to output the first DC detection signal.

[0059] Impedance transformation circuit 10 includes a second operational amplifier U3 and a fourth resistor R4;

[0060] The first end of the fourth resistor R4 forms the input terminal of the impedance transformation circuit 10 and is connected to the electronic voltage transformer 00 to receive the first AC detection signal; the second end of the fourth resistor R4 is connected to the non-inverting input terminal of the second operational amplifier U3, the positive power supply terminal V+ of the second operational amplifier U3 is connected to the positive power supply V1+, and the negative power supply terminal V- of the second operational amplifier U3 is connected to the negative power supply V1-; the inverting input terminal and the output terminal of the second operational amplifier U3 are connected and together form the output terminal of the impedance transformation circuit, which is connected to the AC / DC conversion circuit 20 to output the second AC detection signal.

[0061] The second DC detection signal includes a positive second DC detection signal and a negative second DC detection signal; the single-ended conversion circuit 40 includes a third operational amplifier U4, a fifth resistor R5 and a sixth resistor R6;

[0062] The positive power supply terminal V+ of the third operational amplifier U4 is connected to the first power supply VDD, and the negative power supply terminal V- of the third operational amplifier U3 is connected to the power ground. The non-inverting input terminal of the third operational amplifier U4 and the first terminal of the fifth resistor R5 are connected to form the first input terminal of the single-ended conversion circuit 40, which is connected to the high-impedance isolation circuit 30 to receive the positive second DC detection signal. The negative input terminal of the third operational amplifier U4 and the first terminal of the sixth resistor R6 are connected to form the second input terminal of the single-ended conversion circuit 40, which is connected to the high-impedance isolation circuit 30 to receive the negative second DC detection signal. The output terminal of the third operational amplifier U4 and the second terminal of the sixth resistor R6 are connected to form the output terminal of the single-ended conversion circuit 40 to output the sampling signal.

[0063] Follower 50 includes a fourth operational amplifier U5 and a seventh resistor R7;

[0064] The first end of the seventh resistor R7 forms the input terminal of the follower 50 and is connected to the single-ended conversion circuit 40 to receive the sampling signal; the second end of the seventh resistor R7 is connected to the non-inverting input terminal of the fourth operational amplifier U5, the positive power supply terminal V+ of the fourth operational amplifier U5 is connected to the first power supply VDD, and the negative power supply terminal V- of the fourth operational amplifier U5 is connected to the power ground; the inverting input terminal and the output terminal of the fourth operational amplifier U5 are connected and together form the output terminal of the follower 50 to output the sampled signal after following.

[0065] The electronic voltage transformer 00 includes a second capacitor C2, a third capacitor C3, a fourth capacitor C4, an eighth resistor R8, a ninth resistor R9, and a tenth resistor R10.

[0066] The first terminal of the second capacitor C2 and the first terminal of the eighth resistor R8 are connected and together form the input terminal of the electronic voltage transformer 00 to connect the AC power to be measured; the second terminal of the second capacitor C2 is connected to the second terminal of the eighth resistor R8, the first terminal of the ninth resistor R9 and the first terminal of the third capacitor C3; the second terminal of the ninth resistor R9, the second terminal of the third capacitor C3, the first terminal of the tenth resistor R10 and the first terminal of the fourth capacitor C4 are connected and together form the output terminal of the electronic voltage transformer 00, which is connected to the impedance transformation circuit 10 to output the first AC detection signal; the second terminal of the tenth resistor R10 and the second terminal of the fourth capacitor C4 are connected to the signal ground.

[0067] It is understandable that the input terminal of the electronic voltage transformer 00 is connected to the positive AC power to be measured, and the signal ground is connected to the negative AC power to be measured.

[0068] The protection circuit 80 includes a discharge tube DS1, a varistor FV1, and a transient voltage suppression diode TVS1;

[0069] The first end of the discharge tube DS1, the first end of the varistor FV1, and the first end of the transient voltage suppressor diode TVS1 are connected together to form the input and output terminals of the protection circuit 80, which are connected to the electronic voltage transformer 00 and the impedance transformation circuit 10 to receive the first AC detection signal and output the first AC detection signal after EMC protection; the second end of the discharge tube DS1, the second end of the varistor FV1, and the second end of the transient voltage suppressor diode TVS1 are connected to the signal ground.

[0070] The high-impedance isolation circuit 30 includes an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, and a fourteenth resistor R14;

[0071] The first end of the thirteenth resistor R13 forms the negative input terminal of the high-impedance isolation circuit 30 and is connected to the signal ground; the first end of the eleventh resistor R11 forms the positive input terminal of the high-impedance isolation circuit 30 and is connected to the AC / DC conversion circuit 20 to receive the first DC detection signal; the second end of the thirteenth resistor R13 is connected to the first end of the fourteenth resistor R14, and the second end of the eleventh resistor R11 is connected to the first end of the twelfth resistor R12; the second end of the twelfth resistor R12 forms the positive output terminal of the high-impedance isolation circuit 30 and is connected to the single-ended conversion circuit 40 to receive the positive second DC detection signal; the second end of the fourteenth resistor R14 forms the negative output terminal of the high-impedance isolation circuit 30 and is connected to the single-ended conversion circuit 40 to receive the negative second DC detection signal.

[0072] The bandpass filter circuit 60 includes a fifth capacitor C5 and a fifteenth resistor R15;

[0073] The first end of the fifth capacitor C5 forms the input terminal of the bandpass filter circuit 60 and is connected to the impedance transformation circuit 10 to receive the second AC detection signal; the second end of the fifth capacitor C5 is connected to the first end of the fifteenth resistor R15; the second end of the fifteenth resistor R15 forms the output terminal of the bandpass filter circuit 60 and is connected to the AC-DC conversion circuit 20 to output the second AC detection signal after bandpass filtering.

[0074] The low-pass filter circuit 70 includes a sixth capacitor C6 and a fifteenth resistor R15;

[0075] The first end of the fifteenth resistor R15 forms the input terminal of the low-pass filter circuit 70, which is connected to the follower 50 to receive the sampled signal after following; the first end of the sixth capacitor C6 and the second end of the fifteenth resistor R15 are connected and together form the output terminal of the low-pass filter circuit 70, which is connected to the control circuit 90 to output the sampled signal after low-pass filtering; the second end of the sixth capacitor C6 is connected to the power supply ground.

[0076] The switching circuit 110 includes an analog switch chip U6;

[0077] The first common terminal COM1 of the analog switch chip U6 constitutes the first common terminal of the switch circuit 110; the normally closed terminal NC1 of the first channel of the analog switch chip U6 constitutes the first normally closed terminal of the switch circuit 110; the second common terminal COM2 of the analog switch chip U6 constitutes the second common terminal of the switch circuit 110; the normally closed terminal NC2 of the second channel of the analog switch chip U6 constitutes the second normally closed terminal of the switch circuit 110; the normally open terminals NO1 and NO2 of the first and second channels of the analog switch chip U6 are both left floating; the first control terminal IN1 of the analog switch chip U6 constitutes the first control terminal of the switch circuit 110 and is connected to the isolation module 100 to receive the isolated first sub-control signal; the second control terminal IN2 of the analog switch chip U6 constitutes the second control terminal of the switch circuit 110 and is connected to the isolation module 100 to receive the isolated second sub-control signal; wherein, the isolated control signal includes the isolated first sub-control signal and the isolated second sub-control signal.

[0078] The isolation module 100 includes a first optocoupler U7, a second optocoupler U8, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, and a twenty-first resistor R21.

[0079] The first terminal of the seventeenth resistor R17 is connected to the negative terminal of the input-side diode of the first optocoupler U7, forming the first input terminal of the isolation module 100, which is connected to the control circuit 90 to receive the first sub-control signal. The first terminal of the twentieth resistor R20 is connected to the negative terminal of the input-side diode of the second optocoupler U8, forming the second input terminal of the isolation module 100, which is connected to the control circuit 90 to receive the second sub-control signal. The first terminal of the eighteenth resistor R18 is connected to the emitter of the first optocoupler U7, forming the first output terminal of the isolation module 100, which is connected to the switching circuit 110 to output the isolated first sub-control signal. The first terminal of the twenty-first resistor R21 is connected to the emitter of the second optocoupler U8, forming the second output terminal of the isolation module 100, which is connected to the switching circuit 110 to output the isolated first sub-control signal. The circuit 110 is connected to output the isolated second sub-control signal; the collectors of the first optocoupler U7 and the second optocoupler U8 are connected and together serve as the reference voltage input terminal of the isolation module 100 to connect to the reference voltage; the first end of the sixteenth resistor R16, the second end of the seventeenth resistor R17, the first end of the nineteenth resistor R19, and the second end of the twentieth resistor R20 are all connected to the first power supply VDD; the second end of the sixteenth resistor R16 is connected to the anode of the input-side diode of the first optocoupler U7, the second end of the nineteenth resistor R19 is connected to the anode of the input-side diode of the second optocoupler U8, and the second end of the eighteenth resistor R18 and the second end of the twenty-first resistor R21 are all connected to the power supply ground; wherein, the control signal includes the first sub-control signal and the second sub-control signal.

[0080] The following is based on the working principle. Figure 6 Further explanation is provided below:

[0081] The RC network in the electronic voltage transformer 00 detects the AC current under test and outputs a first AC detection signal to the first terminal of the discharge tube DS1, the first terminal of the varistor FV1, and the first terminal of the transient voltage suppressor diode TVS1. The discharge tube DS1, varistor FV1, and transient voltage suppressor diode TVS1 release surges, static electricity, and electrical fast transient pulses for EMC protection. The first AC detection signal after EMC protection is sent to the non-inverting input terminal of the second operational amplifier U3 through the fourth resistor R4. The second operational amplifier U3 acts as a follower, therefore the first... Operational amplifier U3 performs impedance transformation on the first AC detection signal after EMC protection, so that the second AC detection signal is output from the output terminal of the second operational amplifier U3 to the bandpass filter circuit 60 containing the fifth capacitor C5 and the fifteenth resistor R15. The fifth capacitor C5 and the fifteenth resistor R15 bandpass filter the second AC detection signal, so that the bandpass-filtered second AC detection signal is output to the inverting input terminal of the first operational amplifier U2. Since the non-inverting input terminal of the first operational amplifier U2 is connected to the reference voltage, the first DC detection signal V output from the output terminal of the first operational amplifier U2 is... ADIN =1 / 2*(Us) max *K+Vref); where Us max Let Vref be the voltage of the second AC current signal, K be the quotient of the equivalent resistance between the output terminal and the inverting input terminal of the first operational amplifier U2 and the resistance of the fifteenth resistor R15, and Vref be the reference voltage. It can be understood that at this time, the analog switch chip U6 has not yet been connected to the isolated control signal. The first channel common terminal COM1 of the analog switch chip U6 is connected to the normally closed terminal NC1 of the first channel of the analog switch chip U6, and the second channel common terminal COM2 of the analog switch chip U6 is connected to the normally closed terminal NC2 of the second channel of the analog switch chip U6. Therefore, the equivalent resistance between the output terminal and the inverting input terminal of the first operational amplifier U2 is the resistance value of the first resistor R1 to the third resistor R3 connected in parallel. That is, the AC / DC conversion circuit 20 has the most... A small scaling factor and maximum range, including a resistor network from the eleventh resistor R11 to the fourteenth resistor R14, provides high-impedance isolation for the first DC detection signal to output a second DC detection signal to the input of the third operational amplifier U4. The third operational amplifier U4 converts the dual-ended second DC detection signal to output a single-ended sampling signal via the seventh resistor R7 to the non-inverting input of the fourth operational amplifier U5. A follower 50, including the seventh resistor R7 and the fourth operational amplifier U5, follows the sampling signal to output the followed sampling signal to the first end of the fifteenth resistor R15. A low-pass filter, including the fifteenth resistor R15 and the sixth capacitor C6, performs low-pass filtering on the followed sampling signal to output the low-pass filtered sampling signal to the analog-to-digital converter (ADC) of the microprocessor U9.

[0082] Microprocessor U9 compares the voltage of the sampled signal with at least one reference voltage, determines the target voltage range of the sampled signal based on the comparison result, and outputs a first sub-control signal from the first general-purpose input / output terminal P1.0 of microprocessor U9 to the negative terminal of the input diode of the first optocoupler U7 based on the target voltage range. It also outputs a second sub-control signal from the second general-purpose input / output terminal P1.1 of microprocessor U9 to the negative terminal of the input diode of the second optocoupler U8 based on the target voltage range. The first optocoupler U7 isolates the first sub-control signal, and the second optocoupler U8 isolates the second sub-control signal. The isolated first sub-control signal is then transmitted from the first optocoupler U7 to the input diode of the second optocoupler U8. The emitter output of the second optocoupler U7 is sent to the first channel control terminal IN1 of the analog switch chip U6. The isolated second sub-control signal is sent from the emitter of the second optocoupler U8 to the second channel control terminal IN2 of the analog switch chip U6. It should be noted that the analog switch chip U6 controls whether the second resistor R2 is connected to the inverting input terminal of the first operational amplifier U2 according to the first sub-control signal, and controls whether the first resistor R1 is connected to the inverting input terminal of the first operational amplifier U2 according to the second sub-control signal, thereby adjusting the equivalent resistance between the output terminal and the inverting input terminal of the first operational amplifier U2, and thus selecting an appropriate range.

[0083] Understandably, after adjusting the equivalent resistance between the output terminal and the inverting input terminal of the first operational amplifier U2, the gain of the AC-DC conversion circuit 20 is adjusted. This adjusted AC-DC conversion circuit 20 then converts the second AC detection signal to output the adjusted first DC detection signal. The high-impedance isolation circuit 30 is also used to provide high-impedance isolation for the adjusted first DC detection signal to output the adjusted second DC detection signal. The single-ended conversion circuit 40 is also used to convert the adjusted double-ended second DC detection signal to output the adjusted single-ended sampling signal. The follower 50, connected to the single-ended conversion circuit 40, is used to follow the adjusted sampling signal to output the followed sampling signal to the control circuit 90.

[0084] This utility model embodiment also provides an electronic device, which includes the above-described sampling circuit based on an electronic voltage transformer.

[0085] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0086] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A sampling circuit based on an electronic voltage transformer, characterized in that, include: An electronic voltage transformer is used to detect the AC current under test and output a first AC detection signal. An impedance transformation circuit, connected to the electronic voltage transformer, is used to perform impedance transformation on the first AC detection signal to output a second AC detection signal. An AC / DC conversion circuit, connected to the impedance transformation circuit, is used to convert the second AC detection signal to output a first DC detection signal; A high-impedance isolation circuit, connected to the AC / DC conversion circuit, is used to provide high-impedance isolation for the first DC detection signal so as to output a second DC detection signal; A single-ended conversion circuit, connected to the high-impedance isolation circuit, is used to convert the double-ended second DC detection signal to output a single-ended sampling signal; A follower, connected to the single-ended conversion circuit, is used to follow the sampled signal to output the followed sampled signal.

2. The sampling circuit based on an electronic voltage transformer as described in claim 1, characterized in that, Also includes: A bandpass filter circuit is connected between the impedance transformation circuit and the AC / DC conversion circuit, and is used for; The AC / DC conversion circuit is specifically used to convert the second AC detection signal after bandpass filtering to output the first DC detection signal.

3. The sampling circuit based on an electronic voltage transformer as described in claim 1, characterized in that, Also includes: A low-pass filter circuit, connected to the follower, is used to perform low-pass filtering on the sampled signal after following, so as to output the low-pass filtered sampled signal.

4. The sampling circuit based on an electronic voltage transformer as described in claim 1, characterized in that, Also includes: A protection circuit is connected between the electronic voltage transformer and the impedance transformation circuit to perform EMC protection on the first AC detection signal, so as to output the first AC detection signal after EMC protection. The impedance transformation circuit is specifically used to transform the impedance of the first AC detection signal after EMC protection in order to output the second AC detection signal.

5. The sampling circuit based on an electronic voltage transformer as described in claim 1, characterized in that, Also includes: A control circuit, connected to the conversion circuit, is used to receive the sampling signal, compare the voltage of the sampling signal with at least one reference voltage, determine the target voltage range where the sampling signal is located based on the comparison result, and output a control signal based on the target voltage range. An isolation module, connected to the control circuit, is used to isolate the control signal so as to output the isolated control signal; A switching circuit, connected to the isolation module, is used to adjust the gain of the AC-DC conversion circuit in response to the access of the isolated control signal, so that the adjusted AC-DC conversion circuit converts the second AC detection signal to output the adjusted first DC detection signal. The high-impedance isolation circuit is also used to perform high-impedance isolation on the regulated first DC detection signal so as to output the regulated second DC detection signal. The single-ended conversion circuit is also used to convert the adjusted double-ended second DC detection signal to output the adjusted single-ended sampling signal. The follower is connected to the single-ended conversion circuit and is used to follow the adjusted sampling signal so as to output the followed sampling signal to the control circuit.

6. The sampling circuit based on an electronic voltage transformer as described in claim 5, characterized in that, The control circuit includes a microprocessor; The analog-to-digital converter of the microprocessor forms the input terminal of the control circuit and is connected to the conversion circuit to receive the sampling signal; The first general-purpose input / output terminal and the second general-purpose input / output terminal of the microprocessor constitute the output terminal of the control circuit, which is connected to the isolation module to output the control signal.

7. The sampling circuit based on an electronic voltage transformer as described in claim 1, characterized in that, The AC / DC conversion circuit includes a first operational amplifier, a first capacitor, a first resistor, a second resistor, and a third resistor; The positive power supply terminal of the first operational amplifier is connected to a positive power supply, and the negative power supply terminal of the first operational amplifier is connected to a negative power supply. The inverting input terminal of the first operational amplifier and the first terminal of the third resistor are connected to form the input terminal of the AC-DC conversion circuit, which is connected to the first common terminal of the impedance transformation circuit and the switching circuit and the second common terminal of the switching circuit to receive the second AC detection signal; The non-inverting input terminal of the first operational amplifier and the first terminal of the first capacitor are connected and together form the reference voltage terminal of the AC-DC conversion circuit to be connected to the reference voltage; The first end of the first resistor is connected to the first normally closed terminal of the switching circuit, and the first end of the second resistor is connected to the second normally closed terminal of the switching circuit. The output terminal of the first operational amplifier, the second terminal of the first resistor, the second terminal of the second resistor, and the second terminal of the third resistor are connected and together form the output terminal of the AC-DC conversion circuit, which is connected to the high-impedance isolation circuit to output the first DC detection signal.

8. The sampling circuit based on an electronic voltage transformer as described in claim 1, characterized in that, The impedance transformation circuit includes a second operational amplifier and a fourth resistor; The first end of the fourth resistor constitutes the input terminal of the impedance transformation circuit and is connected to the electronic voltage transformer to receive the first AC detection signal. The second end of the fourth resistor is connected to the non-inverting input terminal of the second operational amplifier, the positive power supply terminal of the second operational amplifier is connected to a positive power supply, and the negative power supply terminal of the second operational amplifier is connected to a negative power supply. The inverting input terminal and the output terminal of the second operational amplifier are connected and together form the output terminal of the impedance change circuit, which is connected to the AC-DC conversion circuit to output the second AC detection signal.

9. The sampling circuit based on an electronic voltage transformer as described in claim 1, characterized in that, The second DC detection signal includes a positive second DC detection signal and a negative second DC detection signal; the single-ended conversion circuit includes a third operational amplifier, a fifth resistor, and a sixth resistor; The positive power supply terminal of the third operational amplifier is connected to the first power supply, and the negative power supply terminal of the third operational amplifier is connected to the power ground. The non-inverting input terminal of the third operational amplifier and the first terminal of the fifth resistor are connected to form the first input terminal of the single-ended conversion circuit, which is connected to the high-impedance isolation circuit to receive the positive second DC detection signal. The negative phase input terminal of the third operational amplifier and the first terminal of the sixth resistor are connected to form the second input terminal of the single-ended conversion circuit, which is connected to the high-impedance isolation circuit to receive the negative second DC detection signal; The output terminal of the third operational amplifier and the second terminal of the sixth resistor are connected to form the output terminal of the single-ended conversion circuit to output the sampled signal.

10. An electronic device, characterized in that, The electronic device includes a sampling circuit based on an electronic voltage transformer as described in any one of claims 1 to 9.

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