CN113834961A - Alternating current front end detection circuit - Google Patents
Alternating current front end detection circuit Download PDFInfo
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- CN113834961A CN113834961A CN202110916489.7A CN202110916489A CN113834961A CN 113834961 A CN113834961 A CN 113834961A CN 202110916489 A CN202110916489 A CN 202110916489A CN 113834961 A CN113834961 A CN 113834961A
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- 238000001514 detection method Methods 0.000 title claims description 8
- 238000005070 sampling Methods 0.000 claims abstract description 18
- 239000003990 capacitor Substances 0.000 claims abstract description 16
- 102100039435 C-X-C motif chemokine 17 Human genes 0.000 claims description 8
- 101000889048 Homo sapiens C-X-C motif chemokine 17 Proteins 0.000 claims description 8
- 238000005259 measurement Methods 0.000 abstract description 7
- 238000012544 monitoring process Methods 0.000 abstract description 4
- 238000010586 diagram Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R15/00—Details of measuring arrangements of the types provided for in groups G01R17/00 - G01R29/00, G01R33/00 - G01R33/26 or G01R35/00
- G01R15/14—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks
- G01R15/18—Adaptations providing voltage or current isolation, e.g. for high-voltage or high-current networks using inductive devices, e.g. transformers
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- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Measurement Of Current Or Voltage (AREA)
Abstract
The invention belongs to the field of industrial measurement and control, and relates to a front-end circuit for sampling alternating current, which is suitable for various application occasions requiring monitoring, fault wave recording, long-time wave recording and harmonic wave analysis on current. The circuit comprises a precision current transformer CS1, an operational amplifier IC1, input resistors R4 and R5, a bias resistor R1, filter capacitors C1 and C2, a sampling resistor R3, an output MOS tube V1 and a clamping diode V1. The circuit converts alternating current into biased direct voltage, and avoids negative power supply. The device is suitable for high-precision measurement circuits, simple in circuit, low in cost, good in reliability and easy to produce.
Description
Technical Field
The invention belongs to the field of industrial measurement and control, relates to a circuit, in particular to a front-end circuit for sampling alternating current, and is suitable for various application occasions needing to carry out monitoring, fault wave recording, long-time wave recording and harmonic analysis on current.
Background
In systems for intelligent power distribution, it is desirable to monitor the ac current signal. The current common method is based on a scheme of a special power quality monitoring chip, and voltage and current are directly converted into digital signals. The scheme is limited by the capability of the power quality monitoring chip, generally has no wave recording function, has few types of measurable power parameters, and cannot provide high-end signal analysis capability. Therefore, how to design a current sampling front-end circuit scheme based on high precision has good application prospect in a high-end intelligent power distribution system.
Disclosure of Invention
The invention provides an alternating current detection front-end circuit, and aims to provide a current detection circuit which converts alternating current into biased direct current voltage and avoids using a negative power supply.
In order to achieve the above purpose, the invention adopts the following technical scheme:
an alternating current detection front-end circuit comprises a precision current transformer CS1, an operational amplifier IC1, input resistors R4 and R5, a bias resistor R1, filter capacitors C1 and C2, a sampling resistor R3, an output MOS tube V1 and a clamping diode V1. One output end of the precision current transformer CS1 is connected with the input resistor R4; the other end of the input resistor R4 is connected with the negative input end of the operational amplifier IC1, one end of the bias resistor R1 and the source electrode of the output MOS transistor V1; the other output end of the precision current transformer CS1 is connected with an input resistor R5; the other end of the input resistor R5 is connected with the positive input end of the operational amplifier IC1, one end of the filter capacitor C2 and the VCC2 power supply; the other end of the filter capacitor C2 is grounded; the other end of the bias resistor is connected with a VCC1 power supply; the gate of the output MOS transistor V1 is connected with the output end of the operational amplifier IC 1; the drain electrode of the output MOS tube V1 is connected with one end of a sampling resistor R3 and one end of a clamping diode V1; the other end of the sampling resistor R3 is grounded; the other end of the clamping diode V1 is connected with a VCC2 power supply; a positive power supply of the operational amplifier IC1 is connected with one end of a filter capacitor C1 and a VCC1 power supply; the negative power supply of the operational amplifier IC1 is grounded; the other end of the filter capacitor C1 is grounded.
The invention has the following beneficial effects:
the alternating current is converted into a biased direct voltage, and a negative power supply is avoided. The power supply voltage error only affects the bias voltage value, and has no influence on the alternating current measurement precision. The precision of the circuit output only depends on the precision of the precision current transformer and the precision of the resistor R3, and the circuit is suitable for high-precision measuring circuits. The circuit is simple, the cost is low, the reliability is good, and the product is easy to realize.
Drawings
FIG. 1 is a schematic diagram of a circuit structure according to the present invention.
Detailed Description
The embodiments of the present invention will be further described with reference to the accompanying drawings, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. The components of the present invention, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present invention, presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
FIG. 1 is a schematic diagram of a circuit structure according to the present invention.
An alternating current detection front-end circuit comprises a precision current transformer CS1, an operational amplifier IC1, input resistors R4 and R5, a bias resistor R1, filter capacitors C1 and C2, a sampling resistor R3, an output MOS tube V1 and a clamping diode V1. One output end of the precision current transformer CS1 is connected with the input resistor R4; the other end of the input resistor R4 is connected with the negative input end of the operational amplifier IC1, one end of the bias resistor R1 and the source electrode of the output MOS transistor V1; the other output end of the precision current transformer CS1 is connected with an input resistor R5; the other end of the input resistor R5 is connected with the positive input end of the operational amplifier IC1, one end of the filter capacitor C2 and the VCC2 power supply; the other end of the filter capacitor C2 is grounded; the other end of the bias resistor is connected with a VCC1 power supply; the gate of the output MOS transistor V1 is connected with the output end of the operational amplifier IC 1; the drain of the output MOV1 is connected with one end of a sampling resistor R3 and one end of a clamping diode V1; the other end of the sampling resistor R3 is grounded; the other end of the clamping diode V1 is connected with a VCC2 power supply; a positive power supply of the operational amplifier IC1 is connected with one end of a filter capacitor C1 and a VCC1 power supply; the negative power supply of the operational amplifier IC1 is grounded; the other end of the filter capacitor C1 is grounded. The voltage across the sampling resistor R3 is the output signal of the new model.
The main circuit parameters of the invention are matched as follows:
when no current flows through the precision current transformer CS1, the output of the circuit is:
when there is alternating current
When the current flows through the precision current transformer CS1, the output of the circuit is as follows:
the current to be measured is:
wherein B is the transformation ratio of the precision current transformer CS 1. V1 is the voltage of VCC1 power supply, V2 is the voltage of VCC2 power supply, R1 is the resistance of bias resistor R1, R3 is the resistance of sampling resistor R3,
is the output voltage of the circuit and is,
is the current to be measured.
The working process of the invention is as follows:
the bias resistor R1 and the power supply +5V form a bias current source, when no current flows through the precision current transformer CS1, the current flowing through the input resistor R4 and the input resistor R5 is 0, the current flowing through the sampling resistor R3 only biases the current of the current source, and the current forms the voltage of the formula (1) in the sampling resistor R3. The current is far larger than the offset current of the operational amplifier, so the offset current index of the operational amplifier has no influence on the measurement precision.
When there is alternating current
When the current flows through the precision current transformer CS1, the output of the circuit is a voltage of equation (2). As can be seen from equation (2), the power supply voltage error affects only the bias voltage value, and has no effect on the ac measurement accuracy, and the accuracy of the circuit output depends only on the accuracy of the precision current transformer and the accuracy of the resistor R3. Therefore, the invention is suitable for high-precision alternating current measurement occasions.
Claims (2)
1. An alternating current detection front-end circuit is characterized by comprising a precision current transformer CS1, an operational amplifier IC1, input resistors R4 and R5, a bias resistor R1, filter capacitors C1 and C2, a sampling resistor R3, an output MOS transistor V1 and a clamping diode V1; one output end of the precision current transformer CS1 is connected with the input resistor R4; the other end of the input resistor R4 is connected with the negative input end of the operational amplifier IC1, one end of the bias resistor R1 and the source electrode of the output MOS transistor V1; the other output end of the precision current transformer CS1 is connected with an input resistor R5; the other end of the input resistor R5 is connected with the positive input end of the operational amplifier IC1, one end of the filter capacitor C2 and the VCC2 power supply; the other end of the filter capacitor C2 is grounded; the other end of the bias resistor is connected with a VCC1 power supply; the gate of the output MOS transistor V1 is connected with the output end of the operational amplifier IC 1; the drain electrode of the output MOS tube V1 is connected with one end of a sampling resistor R3 and one end of a clamping diode V1; the other end of the sampling resistor R3 is grounded; the other end of the clamping diode V1 is connected with a VCC2 power supply; a positive power supply of the operational amplifier IC1 is connected with one end of a filter capacitor C1 and a VCC1 power supply; the negative power supply of the operational amplifier IC1 is grounded; the other end of the filter capacitor C1 is grounded.
2. An ac current detection front-end circuit according to claim 1, wherein the parameters of the circuit are related as follows:
when no current flows through the precision current transformer CS1, the output of the circuit is:
when an alternating current I flows through the precision current transformer CS1, the output of the circuit is:
in the formula, B is a precise current transformer CS 1; v1 is the voltage of VCC1 power supply, V2 is the voltage of VCC2 power supply, R1 is the resistance of bias resistor R1, R3 is the resistance of sampling resistor R3,
is the output voltage of the circuit and is,
is the current to be measured.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110916489.7A CN113834961A (en) | 2021-08-11 | 2021-08-11 | Alternating current front end detection circuit |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110916489.7A CN113834961A (en) | 2021-08-11 | 2021-08-11 | Alternating current front end detection circuit |
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| Publication Number | Publication Date |
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| CN113834961A true CN113834961A (en) | 2021-12-24 |
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| CN202110916489.7A Pending CN113834961A (en) | 2021-08-11 | 2021-08-11 | Alternating current front end detection circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024065625A1 (en) * | 2022-09-30 | 2024-04-04 | Innoscience (suzhou) Semiconductor Co., Ltd. | Semiconductor system and method for manufacturing and operating thereof |
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2021
- 2021-08-11 CN CN202110916489.7A patent/CN113834961A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2024065625A1 (en) * | 2022-09-30 | 2024-04-04 | Innoscience (suzhou) Semiconductor Co., Ltd. | Semiconductor system and method for manufacturing and operating thereof |
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Application publication date: 20211224 |