Analog acquisition calibration circuit without calibration power supply

Abstract

The utility model discloses an analog quantity acquisition and calibration circuit without a calibration power supply. The analog quantity acquisition and calibration circuit comprises a sampling voltage division unit, an input superposed voltage unit and an analog-to-digital conversion metering unit which are directly or indirectly electrically connected together, wherein the input superposed voltage unit is connected with a preset sampling input end and is used for superposing a voltage with a preset amplitude to the preset sampling input end; the sampling and voltage dividing unit is used for sampling the measurement voltage superposed with the preset amplitude; and the analog-to-digital conversion metering unit is used for calibrating the sampled measurement voltage. According to the technical scheme provided by the utility model, calibration can be carried out through circuit parameters of the analog quantity acquisition circuit under the condition that a calibration power supply is not input, the problem of inconsistent circuit parameters in the AD sampling circuit can be solved, and the analog quantity acquisition precision and the consistency of batch products are ensured.

Description

Technical Field

[0001] The utility model relates to the technical field of charging piles, in particular to an analog quantity acquisition calibration circuit without a calibration power supply. Background Art

[0002] In the AD sampling circuit that samples analog quantities, in order to obtain more accurate collection accuracy and ensure the consistency of batch products, the traditional method is to input a calibrated power supply with relatively high voltage accuracy as the reference voltage. The MCU samples the voltage at this time to form a calibrated voltage or current coefficient value, and then calculates the measured value and the voltage or current coefficient value to obtain an accurate sampling value; thereby overcoming the problem of inconsistent circuit parameters in the AD sampling circuit and ensuring the accuracy and consistency of analog circuit sampling.

[0003] According to the traditional calibration method, during the production test process, the acquisition circuit input calibration power supply of each product needs to be calibrated, which increases the high-precision calibration power supply equipment, production processes and costs required for production; moreover, in products that are operated on site or returned for repair, once the sampling circuit fails or some electronic components are replaced, high-precision calibration power supply equipment is required to recalibrate it in order to achieve accurate acquisition accuracy requirements. The calibration process is cumbersome and inefficient. Utility Model Content

[0004] In order to overcome the shortcomings of the existing technology, an analog quantity acquisition calibration circuit without a calibration power supply is proposed. The circuit parameters of the analog quantity acquisition circuit itself can be calibrated without inputting a calibration power supply. The problem of inconsistent circuit parameters in the AD sampling circuit can also be solved, thereby ensuring the accuracy of analog quantity acquisition and the consistency of batch products.

[0005] An analog quantity acquisition and calibration circuit without a calibration power supply comprises: a sampling voltage divider unit, an input superimposed voltage unit and an analog-to-digital conversion and measurement unit which are directly or indirectly electrically connected together; wherein the input superimposed voltage unit is connected to a preset sampling input terminal and is used to superimpose a voltage of a preset amplitude onto the preset sampling input terminal; the sampling voltage divider unit is used to sample the measurement voltage after superimposing the preset amplitude; and the analog-to-digital conversion and measurement unit is used to calibrate the sampled measurement voltage.

[0006] Preferably, the preset sampling input terminal includes a non-inverting input terminal of an operational amplifier circuit or an inverting input terminal of an operational amplifier circuit;

[0007] Preferably, the analog-to-digital conversion metering unit includes a metering chip, and the metering chip communicates with the sampling voltage dividing unit via a serial port;

[0008] Preferably, the reference voltage of the metering chip is 1.25V;

[0009] Preferably, the sampling voltage-dividing unit comprises a DC voltage input terminal, after which a plurality of voltage-dividing resistors are first connected in parallel, and then connected to the input terminal of the analog-to-digital conversion and metering unit;

[0010] Preferably, the input voltage range after voltage division by the sampling voltage division unit is 0 to 0.064V;

[0011] Preferably, the input superposition voltage unit comprises a reference power supply for superposition, an operational amplifier connected to the reference power supply, and a negative input terminal of the reference power supply connected to the output of the operational amplifier;

[0012] Preferably, the input superposition voltage unit further includes an input voltage filter group and an output voltage filter group; the input voltage filter group includes a plurality of capacitors and input resistors, and the output voltage filter group includes a plurality of capacitors and output resistors.

[0013] The analog quantity acquisition calibration circuit without calibration power supply provided by the utility model has the following advantages:

[0014] 1) High-precision analog acquisition accuracy can be obtained without calibrating the power supply; in the absence of power supply calibration, the consistency of acquisition accuracy of batch products can also be guaranteed through self-calibration.

[0015] 2) There is no need to calibrate the power supply equipment during the production process, making production simple and convenient.

[0016] 3) There is no accuracy requirement for the voltage superimposed on the input end of the AD acquisition circuit.

[0017] 4) The calibration method is simple, and calibration is fast and convenient through MCU instructions, which solves the problem of being unable to calibrate without a reference power supply when installed on site.

[0018] 5) It is not only suitable for sampling positive voltage analog quantities, but also for sampling negative voltage analog quantities. At the same time, it can also solve the input zero drift problem of AD op amp circuit.

[0019] 6) This analog quantity acquisition calibration circuit cooperates with input operational amplifier, metering chip and CPU processor to adapt to the calibration of analog quantity acquisition circuits that convert all AC and DC analog quantities into digital quantities. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a sampling voltage divider unit in an embodiment of the utility model;

[0021] Figure 2 The schematic diagram of the input superposition voltage unit in the embodiment of the utility model;

[0022] Figure 3It is a schematic diagram of the analog-to-digital conversion metering unit in the embodiment of the utility model. DETAILED DESCRIPTION

[0023] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] In one embodiment, an analog quantity acquisition calibration circuit without a calibration power supply is provided, which mainly includes three modules: a sampling voltage division unit, an input superposition voltage unit, and an analog-to-digital conversion measurement unit. The schematic diagram of each module is respectively referred to Figures 1 to 3 The three modules are electrically connected together directly or indirectly, wherein the input superposition voltage unit is connected to the preset sampling input terminal and is used to superimpose a voltage of a preset amplitude on the preset sampling input terminal; the sampling voltage divider unit is used to sample the measured voltage after superimposing the preset amplitude; and the analog-to-digital conversion metering unit is used to calibrate the sampled measured voltage.

[0025] Specifically, in Figure 1 In the sampling voltage divider unit shown, BAT+ and BAT- are DC input voltages with a voltage range of 0-1000 V. After voltage division through voltage divider resistors R175, R176, R177, R178, R179, R180, R181, R182, R183, R184, and R185, they are input to the positive input terminal of the metering chip U22V3P through R174. After voltage division, the input voltage range is: 0-0.064 V.

[0026] B_GND_DC2 is the negative input of analog quantity, W_GND is the ground signal, and W_V3P is the positive input of analog quantity. C189, C189, C1990, and C191 are anti-interference filter capacitors.

[0027] In such Figure 2 In the input superposition voltage unit shown, N_VREFV2 (analog reference voltage of the metering chip, value is 1.25V) is the reference power supply of the superposition power supply, which is divided into the required superposition voltage (i.e. 1.25*1 / (10+1)=0.1126V) by resistors R190 and R193 and input to the positive input of the operational amplifier U25, and amplified by the operational amplifier in a one-to-one ratio to output the same voltage as the input voltage. Its main function is to increase the driving capability of the superposition power supply, and to connect to the negative input of the analog quantity through the R192 current limiting resistor to increase the input voltage of the metering chip, so that the input voltage of the metering chip is in a non-zero state when there is no external DC input voltage, so as to eliminate the input zero drift problem of the AD operational amplifier circuit.

[0028] In addition, capacitors C205, C206 and input resistor R190 form an input voltage filter to eliminate high-frequency signals; R192, C201, C202, and C204 form an output voltage filter to eliminate high-frequency signals.

[0029] In such Figure 3 In the analog-to-digital conversion metering unit shown, the metering chip uses RN8209, W_DVCC is powered by the digital power supply, C170 and C171 are digital power filter capacitors of the metering chip, R166, C167, C172, and C174 constitute the analog power filter of the metering chip, N_REFV2 is the reference voltage of the metering chip (the value is 1.25V), and B_RN_TX and BB_RN_RX communicate with the serial port of the MCU processor through optocoupler isolation.

[0030] The working principle of the analog quantity acquisition calibration circuit based on the non-calibrated power supply is as follows: a voltage of a certain amplitude is superimposed on the input end of the analog quantity acquisition circuit (which can be the in-phase input end or the inverting input end of the operational amplifier circuit), so that when there is no measurement voltage input, the voltage collected by the analog quantity acquisition circuit is the superimposed voltage amplitude, and the AD acquisition circuit or the metering chip converts this voltage value into a digital quantity and transmits it to the MCU processor, and the MCU processor stores this voltage amplitude as the initial value of the AD analog quantity acquisition U0. When the input measurement voltage is a positive voltage, the AD analog quantity acquisition value at this time is Ui, and the AD analog quantity acquisition value U=Ui-U0; when the input measurement voltage is a negative voltage, the AD analog quantity acquisition value at this time is Ui, and the AD analog quantity acquisition value U=-(U0-Ui); at this time, it should be noted that the absolute value of the input negative voltage cannot be greater than the superimposed voltage amplitude.

[0031] It can be understood that the analog quantity acquisition and calibration circuit without a calibration power supply provided by the utility model is not limited to the specific implementation method in the above circuit schematic diagram, and the replacement of the sampling voltage divider unit, the input superposition voltage unit and the analog-to-digital conversion measurement unit in the same manner does not affect the implementation of the present technical solution.

[0032] The above is an explanation of the analog quantity acquisition and calibration circuit without a calibration power supply of the present invention, which is used to help understand the present invention; however, the implementation method of the present invention is not limited to the above-mentioned embodiments, and any changes, modifications, substitutions, combinations, and simplifications made without departing from the principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An analog quantity acquisition calibration circuit without a calibration power supply, characterized in that: It includes a sampling voltage divider unit, an input superimposed voltage unit and an analog-to-digital conversion metering unit which are directly or indirectly electrically connected together; wherein the input superimposed voltage unit is connected to a preset sampling input terminal and is used to superimpose a voltage of a preset amplitude to the preset sampling input terminal; the sampling voltage divider unit is used to sample the measurement voltage after superimposing the preset amplitude; and the analog-to-digital conversion metering unit is used to calibrate the sampled measurement voltage.

2. The analog quantity acquisition calibration circuit without calibration power supply as claimed in claim 1, characterized in that: The preset sampling input terminal includes a non-inverting input terminal of an operational amplifier circuit or an inverting input terminal of an operational amplifier circuit.

3. The analog quantity acquisition calibration circuit without calibration power supply as claimed in claim 1, characterized in that: The analog-to-digital conversion metering unit includes a metering chip, and the metering chip communicates with the sampling voltage dividing unit through a serial port.

4. The analog quantity acquisition calibration circuit without calibration power supply as claimed in claim 3, characterized in that: The reference voltage of the metering chip is 1.25V.

5. The analog quantity acquisition calibration circuit without calibration power supply according to any one of claims 1 to 4, characterized in that: The sampling voltage-dividing unit comprises a direct current voltage input terminal, after which a plurality of voltage-dividing resistors are first connected in parallel, and then connected to the input terminal of the analog-to-digital conversion and metering unit.

6. The analog quantity acquisition calibration circuit without calibration power supply as claimed in claim 5, characterized in that: The input voltage range after voltage division by the sampling voltage division unit is 0 to 0.064V.

7. The analog quantity acquisition calibration circuit without calibration power supply as claimed in claim 5, characterized in that: The input superimposed voltage unit includes a reference power supply for superimposition, an operational amplifier connected to the reference power supply, and a negative input terminal of the reference power supply connected to an output of the operational amplifier.

8. The analog quantity acquisition calibration circuit without calibration power supply as claimed in claim 7, characterized in that: The input superposition voltage unit further includes an input voltage filter group and an output voltage filter group; the input voltage filter group includes a plurality of capacitors and an input resistor, and the output voltage filter group includes a plurality of capacitors and an output resistor.

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