Current sensor of operational amplifier biasing circuit

Abstract

The invention relates to the technical field of current detection, in particular to a current sensor of an operational amplifier biasing circuit, which comprises a precision resistor module used for being connected in series between an output end of a frequency converter and a load end of the frequency converter and acquiring a voltage signal corresponding to current flowing through a load through an isolation acquisition chip, and a core element of the precision resistor module is a precision resistor; and the precision resistor needs to be welded with a copper bar to connect the output end and the load end of the frequency converter. Precision resistance sampling is combined with temperature compensation, the current detection precision can be within + / -0.5% and is far better than 3% deviation of a Hall sensor, and the requirement of a high-precision control system is met; and through the isolation operational amplifier circuit and the multi-stage filtering design, high-frequency clutter and external interference are effectively suppressed, and fault misinformation is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current detection, and particularly relates to a current sensor of an operational amplifier bias circuit. BACKGROUND

[0002] At present, the current sensor mostly used is based on the Hall induction principle, an actual current value is calculated through induced current, and an analog voltage is output to a control unit ADC sampling unit for calculation. However, the current deviation value of the Hall sensor is generally more than 3%, which cannot meet the accurate demand of the control system on the control effect. The current deviation not only affects the control effect of the control algorithm, but also may cause a small probability of false alarm and false report in fault judgment and protection in some scenarios, which will have an adverse effect on actual control.

[0003] To solve the above problems, the present application provides a current sensor of an operational amplifier bias circuit, which adopts a new detection principle and circuit structure to improve the current detection precision, optimizes the structural design, and reduces the cost and space requirement. SUMMARY

[0004] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and achieved by the structure particularly pointed out in the description and the accompanying drawings.

[0005] The present application aims to overcome the above-mentioned deficiencies, and provides a current sensor of an operational amplifier bias circuit.

[0006] To achieve the above-mentioned purpose, the technical solution of the present application is as follows: a current sensor of an operational amplifier bias circuit, comprising: A precision resistance module is used to be connected in series between the output end of a frequency converter and the load end of the frequency converter, and a voltage signal corresponding to the current flowing through the load is collected by an isolation collection chip. The core element of the precision resistance module is a precision resistance R9, and the precision resistance R9 needs to be welded with a copper bar to connect the output end of the frequency converter and the load end. An operational amplifier circuit is divided into an isolation operational amplifier circuit and a precision operational amplifier circuit. The isolation operational amplifier circuit is connected with the output end of the precision resistance module, and is used to receive the voltage signal and output a differential voltage signal after filtering out high-frequency noise. The isolation operational amplifier circuit comprises an isolation chip U3, the input voltage V in of the isolation chip U3 is equal to the output voltage V out1 , and the output interface is Pin7 V out+ , Pin6 V out- . The precision operational amplifier circuit is connected with the output end of the isolation operational amplifier circuit, and is used for receiving the differential voltage signal , and outputs a voltage signal after proportional amplification The precision operational amplifier circuit comprises an operational amplifier chip U2, a current-limiting resistor R8, a resistor R12, a resistor R1 and a resistor R10 The calculation formula of the voltage signal is The output range of Vout2 can be adjusted by adjusting the resistance values of the resistors R1 and R10 The bias circuit is connected with the output end of the precision operational amplifier circuit, and is used for receiving the voltage signal , and outputs a sampling voltage to the ADC sampling port of the single-chip microcomputer after lifting the reference voltage to 2 times V ref The bias circuit comprises a chip U1, a current-limiting resistor R7, a resistor R2 and a resistor R3, the resistance values of the resistors R2 and R3 are the same, and the calculation formula of the sampling voltage is ; The single-chip microcomputer is connected with the output end of the bias circuit, and is used for receiving , and calculates an actual current value in combination with the compensation coefficient S of the precision resistor R9 at different temperatures, and the corresponding relationship between the actual current value and the current value is , wherein .

[0007] In some embodiments, the isolation operational amplifier circuit further comprises a low-pass filter unit composed of a resistor R6 and a capacitor C3.

[0008] In some embodiments, the precision operational amplifier circuit further comprises a single-pole low-pass filter composed of a capacitor C1 and a capacitor C6.

[0009] In some embodiments, a temperature sampling circuit is further included, which is used for collecting the temperature of a copper bar connected with the precision resistor, and outputs a temperature sampling voltage to the ADC sampling port of the single-chip microcomputer, and the temperature sampling circuit comprises an NTC thermistor, a resistor R16, a power supply +5V and an RC filter unit composed of a resistor R14 and a capacitor C7, and the calculation formula of the temperature sampling voltage is . .

[0010] In some embodiments, the single-chip microcomputer is connected with the output end of the temperature sampling circuit, and is used for receiving , in combination with the compensation coefficient S of the precision resistor R9 at different temperatures.

[0011] ​​​In some embodiments, the isolation acquisition chip is connected with the precision resistor R9 through welding for outputting analog voltage of the current sampling circuit ( 、 、 ) and analog voltage of the temperature sampling circuit ( ), and transmitting power supply signals (+5V, GND), U-phase resistance temperature signals (TEMP-U) and current signals (I-U) to the control board through the connector CN1.

[0012] In some embodiments, the current sensor adopts a single injection molding structure, that is, the single injection molding structure is integrally injection molded with the single-phase current sensor, and a bolt fixing point is reserved to ensure the overall strength and reliability, or adopts a three-phase integrated injection molding structure, and outputs the resistance temperature signals and the current signals of the three phases through a single connector.

[0013] By adopting the above technical solutions, the application has the following advantages: 1. Precision is significantly improved: the precision resistor sampling is combined with temperature compensation, the current detection precision can reach within ±0.5%, which is much better than the 3% deviation of the Hall sensor, and meets the demand of high-precision control system; 2. Strong anti-interference ability: through the isolation operational amplifier circuit and multi-stage filter design, high-frequency noise and external interference are effectively suppressed, and fault misreporting is avoided; 3. Space and cost optimization: the sensor can replace the independent copper bar and Hall sensor of the traditional frequency converter, reducing the types of accessories; the copper bar is flexibly arranged, and the single-phase / three-phase integrated injection molding structure reduces the space occupation by more than 30% and the production cost by 20%; 4. Good compatibility: by adjusting the resistance values of R1 and R10, different ADC sampling ranges can be adapted, and the application is suitable for various frequency converters and power electronic devices.

[0014] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the present disclosure.

[0015] It is obvious that the above purposes and other purposes of the present application will become more apparent after the description of the preferred embodiments with various drawings and drawings.

[0016] In order to make the above-mentioned advantages and other purposes, features and advantages of the present application more obvious, one or more preferred embodiments are described below, and the drawings are shown as follows. BRIEF DESCRIPTION OF DRAWINGS

[0017] The drawings are used to provide a further understanding of the present application, and constitute a part of the specification. The drawings are used together with the embodiments of the present application to explain the present application, and do not constitute a limitation on the present application.

[0018] In the drawings, like reference numerals refer to same components, and the drawings are schematic and not necessarily to scale.

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description only constitute one or more embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0020] Main figure mark explanation: Figure 1 The circuit flow block diagram of the current sensor of the operational amplifier addition circuit of the present application; Figure 2 The current sampling circuit diagram of the current sensor of the operational amplifier addition circuit of the present application; Figure 3 The temperature sampling circuit diagram of the current sensor of the operational amplifier addition circuit of the present application; Figure 4 The interface circuit diagram of the current sensor of the operational amplifier addition circuit of the present application; Figure 5 The power supply circuit diagram of the current sensor of the operational amplifier addition circuit of the present application; Figure 6 The structural schematic diagram of the single-phase current sensor of the present application; Figure 7 The first perspective structural schematic diagram of the three-phase current sensor of the present application; Figure 8 The second perspective structural schematic diagram of the three-phase current sensor of the present application. DETAILED DESCRIPTION

[0021] The embodiments of the present application will be described in detail below with reference to the drawings and embodiments, so that the application of technical means to solve technical problems and achieve technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, each embodiment in the present application and each feature in each embodiment can be combined with each other, and the technical solutions formed thereby are within the protection scope of the present application.

[0022] Meanwhile, in the following description, many specific details are set forth in order to provide a thorough understanding of the embodiments of the present application. However, it is apparent to those skilled in the art that the present application can be implemented without the specific details or in a manner other than the specific manner described.

[0023] Please refer to Figures 1-8The present invention provides a current sensor for an operational amplifier bias circuit, comprising: a precision resistor module for being connected in series between the output terminal and the load terminal of the frequency converter, and for acquiring the voltage signal corresponding to the current flowing through the load through an isolation acquisition chip. The core component of the precision resistor module is a precision resistor R9, and the precision resistor R9 needs to be soldered with a copper busbar to connect the output terminal and the load terminal of the frequency converter. Operational amplifier circuits: divided into isolation operational amplifier circuits and precision operational amplifier circuits; Isolated operational amplifier circuit: connected to the output of the precision resistor module, used to receive the voltage signal, filter out high-frequency noise, and output a differential voltage signal. The isolation operational amplifier circuit includes an isolation chip U3, and the input voltage V of the isolation chip U3 is... in With output voltage V out1 Equal, output interface is Pin 7 V out+ Pin6 V out- ; Precision operational amplifier circuit: connected to the output of the isolation operational amplifier circuit, used to receive the differential voltage signal. The output voltage signal is amplified proportionally. The precision operational amplifier circuit includes operational amplifier chip U2, current-limiting resistor R8, resistor R12, resistor R1, and resistor R10, wherein the voltage signal The calculation formula is: The output range of Vout2 can be adjusted by adjusting the resistance values ​​of resistors R1 and R10. Bias circuit: Connected to the output of the precision operational amplifier circuit, used to receive the voltage signal. Raise its reference voltage to twice V ref Post-output sampling voltage The bias circuit to the microcontroller's ADC sampling port includes chip U1, current-limiting resistor R7, resistor R2, and resistor R3. Resistors R2 and R3 have the same resistance value. The sampling voltage... The calculation formula is: ; Microcontroller: Connected to the output of the bias circuit, used to receive... By combining the compensation coefficient S of the precision resistor R9 at different temperatures, the actual current value is calculated, and the actual current value is compared with... The correspondence is as follows: ,in, G is a constant, with units of mV / A, and the unit of resistance is KΩ.

[0024] Example 1, Single-phase current sensor: Element selection: precision resistor R9 selects 0.01Ω / ±0.1% precision alloy resistor; isolation chip U3 selects ADUM1200; operational amplifier chip U2 selects OPA2340; chip U1 selects LM358; NTC thermistor R15 selects 10kΩ(25℃) MF52 type; resistors R1=R10=10kΩ, R6=1kΩ, C3=0.1μF, C1=C6=10μF, VREF=1.25V.

[0025] Assembly steps: Step 1: precision resistor R9 is welded by copper bar at the output end of the frequency converter U phase and the load end, and the length of the copper bar is cut to 5cm according to the internal space of the frequency converter; Step 2: the isolation acquisition chip is welded at both ends of R9, and the integrated isolation operational amplifier circuit, precision operational amplifier circuit, bias circuit and temperature sampling circuit are connected through the isolation acquisition chip; Step 3: connect the +5V, GND, TEMP-U, I-U signals of the acquisition board to the control board (integrated STM32F103 single-chip microcomputer) through the connector CN1.

[0026] Working process: The temperature compensation coefficient S of precision resistor R9 satisfies the relationship: y=-0.000000403T+0.000110834T+0.997527582, where y is the compensation coefficient S, T is the environmental temperature (unit: ℃), and the temperature range is-40℃~100℃.

[0027] When the frequency converter output U phase current =100A, the environmental temperature T=25℃, the temperature compensation coefficient S of precision resistor R9=0.997527582 (calculated from the relationship of S); The voltage across R9: =100A×0.01Ω×0.9975≈0.9975V, which is filtered by R6 and C3 and input to U3, and the output =0.9975V; After being divided by R8(1kΩ) and R12(1kΩ), and then being amplified by U2 ( =2), The output = =0.9975V×1kΩ / (1kΩ+1kΩ)×2≈0.9975V; Input to U1, and output by the bias circuit, = =0.9975V+2×1.25V≈3.4975V; NTC thermistor collects temperature and outputs =1.65V (25℃) Single-chip microcomputer receives and , through can be calculated = ( - ) / G, wherein, =0.01Ω×0.9975×1kΩ / (1kΩ+1kΩ) ×2≈0.009975Ω=9.975mV / A, finally ≈ (3.4975V-2×1.25) / 0.009975≈100A, detection error <0.2%.

[0028] According to some embodiments of the application, optionally, the isolation operational amplifier circuit further comprises a low-pass filter unit composed of resistor R6 and capacitor C3. Through the low-pass filter circuit, it has the effect of suppressing high-frequency noise, making the calculation data more accurate.

[0029] According to some embodiments of the application, optionally, the precision operational amplifier circuit further comprises a single-pole low-pass filter composed of capacitor C1 and capacitor C6. Through the single-pole low-pass filter, it has the effect of allowing the bandwidth of the amplifier to be adjusted independently of the gain, and helps to reduce the output noise of the isolation amplifier.

[0030] According to some embodiments of the application, optionally, it further comprises a temperature sampling circuit for collecting the temperature of the copper bar connected to the precision resistor and outputting a temperature sampling voltage to the ADC sampling port of the single-chip microcomputer, the temperature sampling circuit comprises an NTC thermistor, a resistor R16, a power supply +5V and an RC filter unit composed of a resistor R14 and a capacitor C7, and the calculation formula of the temperature sampling voltage is: Through the temperature sampling circuit, it has the effect of ensuring the output accuracy.

[0031] According to some embodiments of the application, optionally, the single-chip microcomputer is connected to the output end of the temperature sampling circuit for receiving in combination with the compensation coefficient S of the precision resistor R9 at different temperatures.

[0032] According to some embodiments of the application, optionally, the isolation sampling chip is connected to the precision resistor R9 through welding for outputting the analog voltage of the current sampling circuit ( , , ) and the analog voltage of the temperature sampling circuit ( The power supply signal (+5V, GND), U-phase resistance temperature signal (TEMP-U), and current signal (IU) are transmitted to the control board via connector CN1. The control board integrates a microcontroller and serves to facilitate sampling by the microcontroller's ADC port.

[0033] According to some embodiments of this application, optionally, the current sensor adopts a single injection-molded structure, wherein the single injection-molded structure is a single phase current sensor unit injection-molded as a whole, with reserved bolt fixing points 1 to ensure overall strength and reliability; or a three-phase integrated injection-molded structure is adopted, which outputs three-phase resistance, temperature and current signals through a single plug-in. This improves integration while ensuring overall strength and reliability, and makes installation more convenient and stable.

[0034] Example 2: Three-phase integrated current sensor: Structural adjustment: Based on the first embodiment, precision resistor modules and corresponding circuits for phase V and phase W are added. A three-phase integrated injection molding structure is adopted, and three-phase TEMP-V, TEMP-W, IV, IW signals and common power supply signal are output through a single connector.

[0035] Advantages: Reduces the number of connectors, simplifies internal wiring of the frequency converter, further reduces space occupation, and is suitable for three-phase motor drive scenarios.

[0036] It should be understood that the embodiments disclosed herein are not limited to the specific processing steps or materials disclosed herein, but should be extended to equivalent substitutions of such features as understood by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0037] The term "embodiment" in this specification refers to a specific feature or characteristic described in connection with an embodiment that is included in at least one embodiment of the invention. Therefore, phrases or "embodiments" appearing in various places throughout the specification do not necessarily refer to the same embodiment.

[0038] Furthermore, the described features or characteristics can be incorporated into one or more embodiments in any other suitable manner. In the above description, specific details, such as thickness, quantity, etc., are provided to provide a comprehensive understanding of embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented without the aforementioned specific details or may be implemented using other methods, components, materials, etc.

Claims

1. A current sensor with an operational amplifier bias circuit, characterized in that, include: Precision resistor module: used to be connected in series between the inverter output terminal and the inverter load terminal. It acquires the voltage signal corresponding to the current flowing through the load through an isolation acquisition chip. The core component of the precision resistor module is the precision resistor R9, and the precision resistor R9 needs to be soldered with a copper busbar to connect the inverter output terminal and the load terminal. Operational amplifier circuits: divided into isolation operational amplifier circuits and precision operational amplifier circuits; Isolated operational amplifier circuit: connected to the output of the precision resistor module, used to receive the voltage signal, filter out high-frequency noise, and output a differential voltage signal. The isolation operational amplifier circuit includes an isolation chip U3, and the input voltage V of the isolation chip U3 is... in With output voltage V out1 Equal, output interface is Pin 7 V out+ Pin6 V out- ; Precision operational amplifier circuit: connected to the output of the isolation operational amplifier circuit, used to receive the differential voltage signal. The voltage signal is amplified proportionally and then output as a voltage signal. The precision operational amplifier circuit includes operational amplifier chip U2, current-limiting resistor R8, resistor R12, resistor R1, and resistor R10. The calculation formula is: The output range of Vout2 can be adjusted by adjusting the resistance values ​​of resistors R1 and R10. Bias circuit: Connected to the output of the precision operational amplifier circuit, used to receive the voltage signal and boost its reference voltage to twice V. ref Post-output sampling voltage The bias circuit to the microcontroller's ADC sampling port includes chip U1, current-limiting resistor R7, resistor R2, and resistor R3. Resistors R2 and R3 have the same resistance value. The sampling voltage... The calculation formula is: ; Microcontroller: Connected to the output of the bias circuit, used to receive... By combining the compensation coefficient S of the precision resistor R9 at different temperatures, the actual current value is calculated, and the actual current value is compared with... The correspondence is as follows: ,in, .

2. The current sensor of the operational amplifier bias circuit according to claim 1, characterized in that, The isolation operational amplifier circuit also includes a low-pass filter unit, which consists of a resistor R6 and a capacitor C3.

3. A current sensor with an operational amplifier bias circuit according to claim 1, characterized in that, The precision operational amplifier circuit also includes a single-pole low-pass filter, which consists of capacitors C1 and C6.

4. A current sensor with an operational amplifier bias circuit according to claim 1, characterized in that, It also includes a temperature sampling circuit for acquiring the temperature of the copper busbar connected to the precision resistor and outputting a temperature sampling voltage. The temperature sampling circuit, connected to the microcontroller's ADC sampling port, includes an NTC thermistor, resistor R16, a +5V power supply, and an RC filter unit. The RC filter unit consists of resistor R14 and capacitor C7. The temperature sampling voltage... The calculation formula is: .

5. A current sensor for an operational amplifier bias circuit according to claim 4, characterized in that, The microcontroller is connected to the output of the temperature sampling circuit to receive... Combined with the compensation coefficient S of the precision resistor R9 at different temperatures.

6. A current sensor for an operational amplifier bias circuit according to claim 5, characterized in that, The isolation acquisition chip is connected to a precision resistor R9 via soldering and is used to output the analog voltage (, ) of the current sampling circuit. , ) and the analog voltage of the temperature sampling circuit ( The power supply signal (+5V, GND), U-phase resistance temperature signal (TEMP-U), and current signal (IU) are transmitted to the control board via connector CN1. The control board integrates a microcontroller.

7. A current sensor for an operational amplifier bias circuit according to claim 1, characterized in that, The current sensor adopts a single injection molding structure, which is a single injection molding of the phase current sensor. The bolt fixing points are reserved to ensure the overall strength and reliability. Alternatively, a three-phase integrated injection molding structure can be adopted, which outputs three-phase resistance, temperature and current signals through a single plug-in.

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