A high isolation and withstand voltage AC voltage sensor

Abstract

The present invention relates to the field of automated detection technology, and in particular to a high-isolation withstand voltage type AC voltage sensor. It includes an isolation conversion circuit, a power supply circuit, a rectifier filter circuit, and an output conversion circuit. The isolation conversion circuit is used to convert the high-voltage AC voltage signal to be measured into an AC current signal of 1mA and transmit it to the rectifier filter circuit. The rectifier filter circuit is used to rectify and filter the 1mA AC current signal output by the isolation conversion circuit, and then convert it into a 1V DC voltage signal and transmit it to the output conversion circuit. The output conversion circuit is used to linearly convert the 1V DC voltage signal output by the rectifier filter circuit into a 4-20mA standard DC signal for output, and the power supply circuit is used to provide working power for the rectifier filter circuit and the output conversion circuit. The present invention has high insulation isolation withstand voltage, can directly measure high-voltage AC voltage signals, and has good detection linearity and high precision.

Description

Technical Field

[0001] The invention relates to the technical field of automated detection, and in particular to a high-isolation and withstand-voltage type AC voltage sensor. Background Art

[0002] As we all know, in the field of automated detection and control, various types of signals are complex and diverse. In particular, the upgrade of various power equipment has spawned a large number of high-voltage applications. The demand for real-time monitoring and control of high-voltage signals by automated systems is increasing. Many traditional monitoring methods and devices also need to be further upgraded to meet the monitoring needs of automated systems for high-voltage signals. Voltage sensors are sensors that can sense the measured voltage and convert it into a usable output signal. In various automatic detection and control systems, it is often necessary to track and collect high-speed changing AC and DC voltage signals, and perform spectrum analysis on more complex voltage waveforms. Such signals may be strong electricity such as high voltage and high current, or weak electricity with poor load capacity or signals with very small amplitude. In these cases, it is necessary to use appropriate voltage sensors to collect voltage signals that cannot be directly measured or are not matched, so as to obtain standardized and electrically isolated voltage signals.

[0003] For AC voltage measurement, a voltage transformer can be used as a sensing element, that is, a voltage transformer is used to reduce the measured voltage to a usable low voltage, and then converted into a DC voltage that is linearly related to the measured voltage through a related circuit and sent to the data acquisition system and A / D converter. The function of the voltage sensor is to automatically detect the voltage, so that we can control and display the voltage of the equipment or system, and take automatic protection measures such as overvoltage and undervoltage when necessary. The more commonly used voltage sensors include voltage transformers and Hall voltage sensors:

[0004] (1) Voltage transformer

[0005] With the increasing capacity of power systems and the continuous improvement of grid voltage operating levels, voltage transformers have become one of the important devices for power metering and relay protection in power systems. Their measurement accuracy and reliability have an important impact on the safety, stability and economic operation of power systems. Voltage transformers are installed between the primary and secondary electrical circuits in power systems. Their main function is to reduce the high voltage on the transmission line to a standard value that can be directly measured by instruments according to a certain ratio, so that voltage measuring instruments can directly measure it. In addition to being used for measurement, voltage transformers can also cooperate with relay protection and automatic devices to perform electrical protection and automatic control of various faults in the power grid. Voltage transformers achieve electrical isolation between primary and secondary systems. However, existing voltage transformers have the disadvantages of being bulky, having high power consumption, and insufficient insulation isolation and withstand voltage.

[0006] (2) Hall voltage sensor.

[0007] Hall voltage sensor is one of the most widely used sensor devices in the field of electronic measurement today. It can be widely used in many fields such as electricity, electronics, AC variable frequency speed regulation, inverter, electronic measurement and switching power supply. Hall voltage sensor is a voltage detection element that can isolate the main current loop from the electronic control circuit. It has excellent electrical performance. The same detection element can detect both AC and DC, and even transient voltage peaks. It is a new generation of products that are expected to replace traditional transformers. Hall voltage sensors can be divided into: magnetic balance voltage sensor, magnetic modulation voltage sensor, photoelectric isolation voltage sensor, high resistance isolation voltage sensor according to different working principles. However, the existing Hall voltage sensors have the disadvantages of large drift, high power consumption, low accuracy and insufficient insulation isolation withstand voltage.

[0008] Therefore, from the perspective of technology and use effect, in the field of automatic detection of AC high-voltage AC signals, most of the existing commonly used voltage sensors have the disadvantages of insufficient insulation isolation and withstand voltage, and low accuracy, which deserves further improvement. Summary of the invention

[0009] In view of the deficiencies in the prior art, the present invention provides a high isolation and withstand voltage type AC voltage sensor, which, when used, has high insulation isolation and withstand voltage, can directly measure high voltage AC voltage signals, and has high detection accuracy.

[0010] The technical solution adopted by the present invention is:

[0011] A high-isolation and withstand-voltage AC voltage sensor comprises a high-voltage side circuit and a low-voltage side circuit, wherein the high-voltage side circuit comprises an isolation conversion circuit, and the low-voltage side circuit comprises a power supply circuit, a rectifier filter circuit and an output conversion circuit. The input end of the isolation conversion circuit is connected to a high-voltage AC voltage signal to be measured, and the output end is connected to the rectifier filter circuit, which is used to convert the high-voltage AC voltage signal to be measured into an AC current signal of 1 mA and transmit it to the rectifier filter circuit. The input end of the rectifier filter circuit is connected to the isolation conversion circuit, and the output end is connected to the output conversion circuit, which is used to rectify and filter the 1 mA AC current signal output by the isolation conversion circuit, and then convert it into a 1 V DC voltage signal and transmit it to the output conversion circuit. The input end of the output conversion circuit is connected to the rectifier filter circuit, which is used to linearly convert the 1 V DC voltage signal output by the rectifier filter circuit into a 4-20 mA standard DC signal for output. The power supply circuit is used to provide working power for the rectifier filter circuit and the output conversion circuit.

[0012] As a preferred embodiment of the above technical solution, a high-voltage resistor is provided at the input end of the isolation conversion circuit, and the high-voltage resistor limits the passing current to 1 mA, and the high-voltage resistor is an aluminum oxide high-voltage resistor.

[0013] As a preferred embodiment of the above technical solution, the isolation conversion circuit includes four cascaded voltage transformers, and the voltage transformer adopts a TV31B02-2mA / 2mA type voltage transformer with an isolation withstand voltage of 2500VAC / min. After the four voltage transformers are cascaded, the isolation withstand voltage reaches 10000VAC / min.

[0014] As a preferred embodiment of the above technical solution, the rectification and filtering circuit includes a closed-loop current sampling circuit that converts a 1mA AC current signal into a 1V AC voltage signal, and a second-order low-pass filtering circuit that converts a 1V AC voltage signal into a 1V DC voltage signal.

[0015] As a preferred embodiment of the above technical solution, both the closed-loop current sampling circuit and the second-order low-pass filter circuit are provided with a LM2092 single-power supply operational amplifier.

[0016] As a preferred embodiment of the above technical solution, the output conversion circuit includes a current calibration conversion circuit and a bias circuit. The current calibration conversion circuit can output a 20mA DC signal at full-scale input, and the bias circuit can output a 4mA DC signal at 0 input.

[0017] As a preferred embodiment of the above technical solution, both the current calibration conversion circuit and the bias circuit are provided with a LM2092 single-power supply operational amplifier.

[0018] As a preferred embodiment of the above technical solution, the power supply circuit is provided with a three-terminal voltage regulator, the input end of the three-terminal voltage regulator is connected to an external 24V power supply, the output end outputs a 12V stable voltage, and the ground end is grounded.

[0019] The beneficial effects of the present invention are:

[0020] The present invention realizes direct measurement and collection of high-voltage AC signals through a circuit setting with high insulation isolation and voltage resistance, completes insulation isolation, linear conversion and transmission between high and low voltage signals, has the characteristics of small size, compact structure, safety and reliability, strong anti-interference ability, high detection accuracy, low cost, and is conducive to batch replication, and has high practical value and promotion significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a structural schematic diagram of the present invention;

[0023] Figure 2 The circuit diagram of the isolation conversion circuit is shown in FIG.

[0024] Figure 3 is the circuit diagram of the rectifier and filter circuit;

[0025] Figure 4 is a circuit diagram of an output conversion circuit;

[0026] Figure 5 This is a circuit diagram of the power supply circuit. DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. The specific structures and functional details disclosed herein are only used to describe the exemplary embodiments of the present invention. However, the present invention can be embodied in many alternative forms, and it should not be understood that the present invention is limited to the embodiments set forth herein.

[0028] It should be understood that the terms first, second, etc. are only used to distinguish descriptions and should not be understood as indicating or implying relative importance. Although the terms first, second, etc. may be used herein to describe various units, these units should not be limited by these terms. These terms are only used to distinguish one unit from another unit. For example, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit without departing from the scope of the exemplary embodiments of the present invention.

[0029] It should be understood that the term "and / or" in this article is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, B exists alone, and A and B exist at the same time. The term " / and" in this article describes another relationship between associated objects, indicating that two relationships may exist. For example, A / and B can represent two situations: A exists alone, and A and B exist alone. In addition, the character " / " in this article generally indicates that the previous and next associated objects are in an "or" relationship.

[0030] It should be understood that in the description of the present invention, the terms "upper", "vertical", "inside", "outside" and the like indicate orientations or positional relationships that are customarily placed when the product of the invention is used, or are orientations or positional relationships that are customarily understood by those skilled in the art. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0031] It should be understood that when an element is referred to as being "connected," "connected," or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements. Other words used to describe the relationship between elements should be interpreted in a similar manner (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

[0032] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "setting", "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] The terms used herein are only used to describe specific embodiments and are not intended to limit the exemplary embodiments of the present invention. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates the opposite meaning. It should also be understood that the terms "include", "comprise", "include", and / or "comprising" when used herein specify the existence of the claimed features, integers, steps, operations, units and / or components, and do not exclude the existence or increase of one or more other features, quantities, steps, operations, units, components and / or their combinations.

[0034] It should also be noted that in some alternative embodiments, the functions / acts that appear may be different from the order in which the figures appear. For example, depending on the functions / acts involved, they may actually be performed substantially concurrently, or two figures shown in succession may sometimes be performed in the reverse order.

[0035] In the following description, specific details are provided to facilitate a complete understanding of the example embodiments. However, it should be understood by those of ordinary skill in the art that the example embodiments may be implemented without these specific details. For example, the system may be shown in a block diagram to avoid obscuring the example with unnecessary details. In other embodiments, well-known processes, structures, and techniques may not be shown in unnecessary detail to avoid obscuring the example embodiments.

[0036] Embodiment 1:

[0037] This embodiment provides a high isolation and withstand voltage type AC voltage sensor, such as Figure 1 As shown:

[0038] It includes a high-voltage side circuit and a low-voltage side circuit. The high-voltage side circuit includes an isolation conversion circuit, and the low-voltage side circuit includes a power supply circuit, a rectifier and filter circuit, and an output conversion circuit. The input end of the isolation conversion circuit is connected to the high-voltage AC voltage signal to be measured, and the output end is connected to the rectifier and filter circuit, which is used to convert the high-voltage AC voltage signal to be measured into a 1mA AC current signal and transmit it to the rectifier and filter circuit. The input end of the rectifier and filter circuit is connected to the isolation conversion circuit, and the output end is connected to the output conversion circuit, which is used to rectify and filter the 1mA AC current signal output by the isolation conversion circuit, and then convert it into a 1V DC voltage signal and transmit it to the output conversion circuit. The input end of the output conversion circuit is connected to the rectifier and filter circuit, which is used to linearly convert the 1V DC voltage signal output by the rectifier and filter circuit into a 4-20mA standard DC signal for output. The power supply circuit is used to provide working power for the rectifier and filter circuit and the output conversion circuit.

[0039] During specific implementation, the high-voltage AC voltage signal to be measured can be directly connected through the isolation conversion circuit, and the high-voltage AC voltage signal can be converted into a 1mA AC current signal for subsequent processing, thereby achieving high insulation isolation and withstand voltage between the high-voltage side circuit and the low-voltage side circuit. The high-voltage AC voltage signal can be directly measured and collected, and the processed signal can be linearly converted into a 4-20mA standard DC signal for output through the output conversion circuit, thereby improving the detection accuracy and facilitating the intelligent monitoring and control of the subsequent system.

[0040] Embodiment 2:

[0041] As an optimization of the above embodiment, Figure 2 As shown, the input end of the isolation conversion circuit is provided with a high-voltage resistor, which limits the current to 1mA, that is, the resistance of the high-voltage resistor is equal to the voltage of the high-voltage AC voltage signal to be measured divided by 1mA, and the isolation conversion circuit includes four cascaded voltage transformers. The high-voltage resistors RV1 and RV2 use thick film process aluminum oxide high-voltage resistors for current limiting, and their model is EBGC1 series. When the input voltage is 2000V, the high-voltage resistor is an EBGC1-1MΩ aluminum oxide high-voltage resistor, and two 1M ohm resistors are used to limit the current to 1mA. The four cascaded voltage transformers TR1~TR4 use four universal current type voltage transformers, the model of which can be selected is TV31B02-2mA / 2mA, with an isolation withstand voltage of 2500VAC / min. After the four voltage transformers are cascaded, the isolation withstand voltage can reach 10000VAC / min. F3-F6 are TVS, which can effectively protect the transformer from damage when there is a surge signal or lightning intrusion port at the input end. The above circuit completes the safe isolation conversion from high voltage to low voltage, providing highly reliable low voltage signals for back-end circuit processing.

[0042] Embodiment 3:

[0043] As an optimization of the above embodiment, Figure 3 As shown, the rectifier and filter circuit rectifies and filters the 1mA AC current signal output by the isolation conversion circuit. Since the circuit is powered by a single power supply, a single-power amplifier should be selected, such as LM2092. In order to ensure the integrity of the AC signal sampling, resistors R1 and R3 raise the signal. A closed-loop current sampling circuit is formed by the single-power amplifier U1A and R2. The two input ends of U1A are connected to the output end of the isolation conversion circuit and converted into a 1V AC low voltage signal. After passing through the C2 DC blocking capacitor, it is rectified by the full-wave rectifier circuit composed of the single-power amplifier U1B, R6, R7, D2, and D1, and then filtered by the second-order low-pass filter composed of the single-power amplifier U2A, R8, R17, R14, R15, C5, and C7. It is converted into a stable 1V DC voltage signal. The output end of U2A is connected to the output conversion circuit.

[0044] Embodiment 4:

[0045] As an optimization of the above embodiment, Figure 4 As shown, the output conversion circuit linearly converts the rectified and filtered DC signal into a standard 4-20mA DC signal, which is convenient for providing measurement control signals for the automation system. The output conversion circuit is also powered by a single power supply, so D3 and D4 are added mainly to reduce the voltage, so that the conversion output is lower than the working power supply of the op amp, ensuring the high linearity of the circuit. The single-power op amp U2B, the single-power op amp U2C and related separation components (resistors, transistors, etc.) constitute the current calibration conversion circuit. By adjusting the potentiometer W1, the full scale can be calibrated so that the output is 20mA when the full-scale input is input. The voltage drop of R20 and R21 is equal. By adjusting the corresponding resistance value, a proportionally converted current signal can be obtained. The positive input end of U2B is connected to the rectifier and filter circuit. The single-power op amp U2D and related separation components and U3 (U3 is the reference TL431, providing a stable bias voltage of 2.5V) constitute the bias circuit. When 0 is input, the potentiometer W2 is adjusted to output a stable bias current of 4mA.

[0046] In order to ensure the performance in specific use, this embodiment provides a set of parameter test data for verification, the input rated value is 2000VAC, the output is externally connected to a 250 ohm standard resistor, and the test data is as follows:

[0047] Input(V) 2000 1600 1200 800 600 400 200 100 20 0 Output(V) 4.998 4.198 3.402 2.601 2.203 1.802 1.396 1.198 1.038 0.999 Theoretical value (V) 5 4.2 3.4 2.6 2.2 1.8 1.4 1.2 1.04 1

[0048] Embodiment 5:

[0049] As an optimization of the above embodiment, Figure 5As shown, the power supply circuit adopts a simple solution, with a +24V input power supply. YM1 is a varistor, F2 is a TVS, and its main function is to protect the input port. D5 is an anti-reverse diode to prevent the power supply from being connected in reverse. DW1 is a voltage regulator, and U4 is a three-terminal voltage regulator, which generates a +12V stable voltage for use in the rectifier filter circuit and the output conversion circuit.

[0050] The present invention is not limited to the above optional implementations, and anyone can derive other various forms of products under the enlightenment of the present invention. The above specific implementations should not be understood as limiting the scope of protection of the present invention. The scope of protection of the present invention should be based on the definition in the claims, and the description can be used to interpret the claims.

Claims

1. A high isolation and withstand voltage AC voltage sensor, characterized in that: The invention comprises a high-voltage side circuit and a low-voltage side circuit, wherein the high-voltage side circuit comprises an isolation conversion circuit, and the low-voltage side circuit comprises a power supply circuit, a rectifier filter circuit and an output conversion circuit. The input end of the isolation conversion circuit is connected to the high-voltage AC voltage signal to be measured, and the output end is connected to the rectifier filter circuit, which is used to convert the high-voltage AC voltage signal to be measured into an AC current signal of 1 mA and transmit it to the rectifier filter circuit. The input end of the rectifier filter circuit is connected to the isolation conversion circuit, and the output end is connected to the output conversion circuit, which is used to rectify and filter the 1 mA AC current signal output by the isolation conversion circuit, and then convert it into a 1 V DC voltage signal and transmit it to the output conversion circuit. The output end of the output conversion circuit is connected to the isolation conversion circuit, and the output end of the output conversion circuit is connected to the output conversion circuit. The input end is connected to the rectifier and filter circuit, which is used to linearly convert the 1V DC voltage signal output by the rectifier and filter circuit into a 4-20mA standard DC signal for output. The power supply circuit is used to provide working power for the rectifier and filter circuit and the output conversion circuit; the input end of the isolation conversion circuit is provided with a high-voltage resistor, which limits the passing current to 1mA, and the high-voltage resistor is an aluminum oxide high-voltage resistor; the isolation conversion circuit includes four cascaded voltage transformers, and the voltage transformer adopts a TV31B02-2mA / 2mA type voltage transformer with an isolation withstand voltage of 2500VAC / min. After the four voltage transformers are cascaded, the isolation withstand voltage reaches 10000VAC / min.

2. The high isolation and withstand voltage AC voltage sensor according to claim 1, characterized in that: The rectification and filtering circuit includes a closed-loop current sampling circuit that converts a 1mA AC current signal into a 1V AC voltage signal, and a second-order low-pass filtering circuit that converts a 1V AC voltage signal into a 1V DC voltage signal.

3. The high isolation and withstand voltage AC voltage sensor according to claim 2, characterized in that: The closed-loop current sampling circuit and the second-order low-pass filter circuit are both provided with an LM2092 single-power supply operational amplifier.

4. The high isolation and withstand voltage AC voltage sensor according to claim 1, characterized in that: The output conversion circuit includes a current calibration conversion circuit and a bias circuit. The current calibration conversion circuit can output a 20mA DC signal when the input is full-scale, and the bias circuit can output a 4mA DC signal when the input is zero.

5. The high isolation and withstand voltage AC voltage sensor according to claim 4, characterized in that: The current calibration conversion circuit and the bias circuit are both provided with a LM2092 type single power supply operational amplifier.

6. The high isolation and withstand voltage AC voltage sensor according to claim 1, characterized in that: The power supply circuit is provided with a three-terminal voltage stabilizer, the input end of the three-terminal voltage stabilizer is connected to an external 24V power supply, the output end outputs a 12V stable voltage, and the ground end is grounded.

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