A weak signal acquisition circuit applied to a single-channel lead salt photodetector

Abstract

The present invention belongs to the technical field of infrared optoelectronic signal acquisition, and mainly relates to a weak signal acquisition circuit system applied to a single-channel lead salt photodetector for acquiring signals of the lead salt infrared photodetector. It includes: a voltage-dividing matching resistor unit module, a direct-current blocking and filtering circuit unit module, a signal amplification circuit unit module, an analog-to-digital conversion unit module, and a digital signal acquisition and processing unit module. Based on the existing technology, the present invention proposes a low-noise and weak signal acquisition circuit applicable to a single-channel infrared photodetector. After filtering the weak optoelectronic signal and amplifying the signal, it avoids the optoelectronic signal being interfered by various large noises and even being submerged. Therefore, using this signal acquisition circuit system can better acquire and analyze the optoelectronic signal, and ultimately improve the accuracy and signal-to-noise ratio of the signal.

Description

Technical Field

[0001] The present invention belongs to the technical field of infrared optoelectronic signal acquisition, and mainly relates to a weak signal acquisition circuit system applied to a single-channel lead salt photodetector for acquiring signals of the lead salt infrared photodetector. Background Art

[0002] With the continuous development of modern industrial technologies, especially the advent of the Industry 4.0 era, more and more fields are beyond the reach of the human senses. Therefore, people urgently need a device to make these fields accessible, and thus detectors came into being. Currently, infrared photodetectors have been gradually widely used in civilian and military applications, etc. However, the infrared photodetector outputs an analog signal, so a signal acquisition system is needed to convert the analog signal into a digital signal. The signal acquisition circuit proposed by the present invention can achieve the conversion between analog and digital signals and is more convenient for collecting and analyzing such signals.

[0003] The signal output by the infrared photodetector is very weak, and there are various noises in the surrounding environment, such as thermal noise, etc. Then these noises will interfere with the weak signal we need and even submerge it. Therefore, it is very important to process these weak signals. Most of the existing lead salt infrared photodetectors and signal acquisition and processing circuits on the market are imported and can only be adapted to some infrared photodetectors to achieve better effects. At the same time, purchasing such products is relatively cumbersome, the price is extremely high, and there are many inconveniences in the later maintenance of the products. Summary of the Invention

[0004] In view of the above problems, after overcoming some deficiencies in the existing technology, the present invention proposes a low-noise and weak signal acquisition circuit applicable to a single-channel infrared photodetector on the basis of the original technology. After filtering the weak optoelectronic signal and amplifying the signal, the optoelectronic signal is prevented from being interfered by various large noises and even submerged. Therefore, using this signal acquisition circuit system can better collect and analyze optoelectronic signals, and ultimately improve the accuracy and signal-to-noise ratio of the signals.

[0005] The technical solution of the present invention is as follows:

[0006] A weak signal acquisition circuit system applied to a single-channel infrared photodetector, comprising: a voltage division and matching resistor unit module, a DC blocking and filtering circuit unit module, a signal amplification circuit unit module, an analog-to-digital conversion unit module, and a digital signal acquisition and processing unit module.

[0007] The voltage dividing and matching resistor unit module is used for signal voltage matching; the DC blocking and filtering circuit unit module is used for primary filtering of the generated signal; the signal amplification circuit unit module is used for amplifying the collected signal; the analog-to-digital conversion unit module is used for converting the analog signal amplified by the amplification circuit into a digital signal; the digital signal acquisition and processing unit module is used for acquiring and processing the converted digital signal.

[0008] By using the above technical solutions, firstly, the circuit structure can be simplified and the cost can be reduced; secondly, the weak signal generated by the infrared photodetector can be collected and processed, and finally the circuit system can be optimized.

[0009] This technical solution can be further optimized as follows: the DC blocking and filtering circuit unit module includes a DC blocking capacitor C1 and a resistor R3, forming an RC filtering circuit, and its output terminal is electrically connected to the positive input terminal of the amplifier OP chip.

[0010] This technical solution can be further optimized as follows: the signal amplification circuit unit module includes an amplifier OP chip, a feedback resistor R1, a capacitor C2, and a resistor R2. Among them:

[0011] The positive input terminal of the amplifier OP chip is connected in series with the RC circuit in the DC blocking and filtering circuit, and the negative input terminal is connected in series with the resistor R2 and then grounded to GND;

[0012] The feedback resistor R1 and the capacitor C2 are connected in parallel to form an RC parallel circuit; one end of the parallel RC is connected to the negative input terminal of the amplifier OP chip, and the other end is connected to the signal output terminal OUT of the amplifier OP chip;

[0013] The positive voltage terminal of the amplifier OP chip is connected in series with the resistor R0 and then connected to the power supply VCC, and the negative voltage terminal is grounded to GND; the signal output terminal OUT of the amplifier OP chip is electrically connected to the 1st pin of U2 in the analog-to-digital conversion unit module.

[0014] This technical solution can be further optimized as follows: the analog-to-digital conversion unit module includes a processor U2, a capacitor C7, a resistor R6, and a resistor R7. Among them:

[0015] The 1st pin of the processor U2 is connected to the signal output terminal OUT of the amplifier OP chip, and the 5th, 6th, 7th, and 8th pins are grounded together;

[0016] One end of the capacitor C7 is connected to the 14th and 16th pins of the processor U2 and then connected to the 5V power supply, and the other end is connected to the 12th and 13th pins of the processor U2 and then connected to GND;

[0017] One end of the resistor R6 is connected to the 9th pin of the processor U2 and is connected in parallel with the 17th pin of U1 in the digital signal acquisition and processing unit module, and the other end is connected to the 5V power supply;

[0018] One end of the resistor R7 is connected to the 10th pin of the processor U2 and is connected in parallel with the 16th pin of U1 in the digital signal acquisition and processing unit module, and the other end is connected to the 5V power supply;

[0019] This technical solution can be further optimized as follows: The processor U2 in the analog-to-digital conversion unit module is a PCF8591 chip.

[0020] This technical solution can be further optimized as follows: The digital signal acquisition and processing unit module includes a processor U1, a reset circuit unit, and a crystal oscillator circuit unit. Among them:

[0021] The reset circuit unit is electrically connected to the 9th pin of the processor U1; the crystal oscillator circuit unit is electrically connected to the 18th and 19th pins of the processor U1 respectively.

[0022] This technical solution can be further optimized as follows: The processor U1 in the digital signal acquisition and processing unit module is an STC89C52 chip.

[0023] In summary, the beneficial effects of this application are as follows: Compared with the circuits in the prior art, this application adopts a modular design, which improves the reliability of the circuit, optimizes the circuit structure, and the selected components and chips have high cost performance, greatly reducing the use cost. At the same time, compared with the expensive imported signal acquisition circuits, the modular design in this application is convenient for interchange, reducing the later circuit maintenance cost. Finally, the circuit in this application is more suitable for short-wavelength and low-frequency infrared photodetectors, reducing the noise impact and improving the signal accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the schematic diagram of the RC filter circuit for the photodetector;

[0025] Figure 2 It is the schematic diagram of the signal amplification unit circuit for the photodetector;

[0026] Figure 3 It is the schematic diagram of the analog-to-digital conversion unit circuit for the photodetector;

[0027] Figure 4 It is the schematic diagram of the main control circuit for digital signal acquisition and processing of the photodetector; DETAILED DESCRIPTION OF THE INVENTION

[0028] The technical solutions in the embodiments of the present application will be further introduced below in combination with the accompanying drawings in the specification and specific implementation manners. The following are only some embodiments of the present application. Based on the embodiments in the present application, any technical solution variations made by other technicians fall within the scope of the embodiments of the present application.

[0029] The present invention is a weak signal acquisition circuit system applied to a single-channel lead salt photodetector, mainly used for short-wave infrared lead salt detectors such as PbSe and PbS, to realize the conversion of target infrared signals into electrical signals. The system mainly includes: a voltage division and matching resistor unit module, a DC blocking and filtering circuit unit module, a signal amplification circuit unit module, an analog-to-digital conversion unit module, and a digital signal acquisition and processing unit module.

[0030] The signal acquisition process is mainly as follows: The analog signal output by the lead salt photodetector passes through the voltage division and matching resistor unit module, the DC blocking and filtering circuit unit module, the signal amplification circuit unit module, and the analog-to-digital conversion unit module, and then enters the digital signal acquisition and processing unit module, where the microcontroller performs digital filtering processing on the converted digital signal.

[0031] The voltage division and matching resistor unit module includes two parts: a detector chip and a matching resistor; the DC blocking and filtering circuit unit module is mainly a parallel resistor R and capacitor C, forming a filtering RC circuit; the amplifier OP chip in the signal amplification circuit unit module uses an OPA333 chip; the processor U2 in the analog-to-digital conversion unit module uses a PCF8591 chip; the processor U1 in the digital signal acquisition and processing unit module uses an STC89C52 chip;

[0032] The voltage division and matching resistor unit module includes: detector r, matching resistor RL;

[0033] The detector r in the voltage division and matching resistor unit module uses a lead salt photodetector as a signal source to generate the required analog signal. The D terminal of detector r is connected to a 5V power supply, the S terminal is connected to the matching resistor RL, and the GND terminal is grounded after being connected to the other end of RL; among them, a resistor RL with a precision of 5% and a resistance value matching the dark resistance of detector r is used to make the signal more stable.

[0034] As Figure 1 shown, the capacitor C1 in the DC blocking and filtering circuit unit module is a chip capacitor with a precision of ±20%, used to block the DC voltage part in the signal; the resistor R3 is a chip resistor with a precision of 5%, and is connected in parallel with the capacitor C1 to form an RC circuit, aiming to filter out some noise in the 5V bias voltage.

[0035] One end of the capacitor C1 is connected to the S terminal of the detector r as the signal input end, receiving the signal generated by the detector r and filtering out the DC part and part of the noise in the signal. The other end of the capacitor C1 is connected to the resistor R3 and the IN+ positive input terminal of the OPA333 chip; the other end of the resistor R3 is connected to GND.

[0036] The signal amplification circuit unit module includes an OPA333 amplifier chip, a feedback resistor R1, a capacitor C2, and a resistor R2.

[0037] Specifically, as Figure 2 shown, the amplifier OP chip in the signal amplification circuit unit module uses the low-power, precision operational amplifier OPA333 chip of Texas Instruments, which can provide an extremely low offset voltage and can achieve almost zero drift over time and with changes in ambient temperature; the IN- negative input terminal of the OPA333 chip is electrically connected to the feedback resistor R1, the resistor R2, and the capacitor C2, and the OUT is connected to the feedback resistor R1, the capacitor C2, and the AIN0 terminal of the signal input end of the PCF8591 chip in the analog-to-digital conversion unit module as the signal output terminal of the precision operational amplifier, sending the analog signal into the PCF8591 chip to be converted into a digital signal; the positive electrode V+ is connected to the resistor R0, and the negative electrode V- is connected to GND; the other end of the resistor R0 is connected to the power supply VCC.

[0038] The feedback resistor R1 is a surface mount resistor with a precision of 5%, connected between the reverse input terminal IN- and the signal output terminal OUT of the OPA333 chip; the resistor R2 is a surface mount resistor with a precision of 5%, one end is connected to the resistor R1 and the reverse input terminal IN- of the OPA333 chip, and the other end is connected to GND.

[0039] The analog-to-digital conversion unit module includes: a PCF8591 chip, a resistor R6, a resistor R7, and a capacitor C7;

[0040] Specifically, as Figure 3 shown, the PCF8591 chip is a typical analog-to-digital conversion chip, having 4 input ports, 8-bit, a total of 16 pins, AIN0~AIN3 are 4 analog signal input ports, A0~A2 are 3 pin address ports, grounded after being connected to VSS in this circuit, and SCL and SDA are the I2C bus serial input / output and the I2C clock line respectively;

[0041] The AIN0 terminal (pin 1) of the PCF8591 chip is connected to the OUT terminal of the OPA333 chip in the amplifier circuit unit module as the input terminal of the analog signal, and then converted into a digital signal; the A0 terminal (pin 5) is connected to A1 (pin 6), A2 (pin 7) and the VSS terminal (pin 8), and then connected to GND; the SDA terminal (pin 9) is connected to the resistor R6 and the connected to the STC89C52 chip, and the SCL terminal (pin 10) is connected to the resistor R7 and the connected to the STC89C52 chip. The two ports of SCL and SDA establish communication with the STC89C52 chip of the microcontroller in the digital signal acquisition and processing unit through the I2C bus to realize signal intercommunication; the EXT terminal (pin 12) and the AGND terminal (pin 13) are connected and then connected to GND, and the VDD terminal (pin 16), the VREF terminal (pin 14) are connected to the capacitor C7 and the 5V voltage; the other end of the capacitor C7 is connected to GND; among them, the resistor R6 is a surface mount resistor with an accuracy of 5%, and the capacitor C7 is a surface mount capacitor with an accuracy of ±20%.

[0042] As Figure 4 shown, the digital signal acquisition and processing unit module includes a processor U1, a reset circuit unit, a crystal oscillator circuit unit and a switching power supply unit. Among them:

[0043] The reset circuit unit is electrically connected to the 9th pin of the processor U1; the crystal oscillator circuit unit is electrically connected to the 18th and 19th pins of the processor U1 respectively; in the switching power supply unit, the polarized capacitor C6 and the surface mount capacitor C12 are connected in parallel, one end is connected to the VCC (40th pin) of the processor U1 and connected to the switch S2, and the other end is connected to the GND (20th pin) of the processor U1; the other end of the switch S2 is connected to the 5V power supply. The processor U1 in the digital signal acquisition and processing unit module uses the STC89C52 chip, and relevant control programs are written using Keil software and C language to control the circuit and collect, process and digitally filter the signals.

Claims

1. A weak signal acquisition circuit applied to a single-channel lead salt photodetector, which is used for a short-wave infrared lead salt detector to realize the conversion of the target infrared signal and the electrical signal. Characterized in that, The weak signal acquisition circuit includes a voltage-dividing matching resistor unit module, a DC-blocking and filtering circuit unit module, a signal amplification circuit unit module, an analog-to-digital conversion unit module, and a digital signal acquisition and processing unit module; the voltage-dividing matching resistor unit module is used for signal voltage matching; the DC-blocking and filtering circuit unit module is used for the primary filtering process of the generated signal; the signal amplification circuit unit module is used for amplifying the acquired signal; the analog-to-digital conversion unit module is used for converting the analog signal amplified by the amplification circuit into a digital signal; the digital signal acquisition and processing unit module is used for acquiring and processing the converted digital signal. The DC-blocking and filtering circuit unit module includes a DC-blocking capacitor C1 and a resistor R3, which form an RC filtering circuit, and its output end is electrically connected to the positive input terminal of the amplifier OP chip. The signal amplification circuit unit module includes an amplifier OP chip, a feedback resistor R1, a capacitor C2, and a resistor R2, where: The positive input terminal of the amplifier OP chip is connected in series with the RC circuit in the DC-blocking and filtering circuit, and the negative input terminal is connected in series with the resistor R2 and then grounded to GND. The feedback resistor R1 and the capacitor C2 are connected in parallel to form an RC parallel circuit; one end of the parallel RC is connected to the negative input terminal of the amplifier OP chip, and the other end is connected to the signal output terminal OUT of the amplifier OP chip. The positive voltage terminal of the amplifier OP chip is connected in series with the resistor R0 and then connected to the power supply VCC, and the negative voltage terminal is grounded to GND; the signal output terminal OUT of the amplifier OP chip is electrically connected to the 1st pin of U2 in the analog-to-digital conversion unit module. The analog-to-digital conversion unit module includes a processor U2, a capacitor C7, a resistor R6, and a resistor R7, where: The 1st pin of the processor U2 is connected to the signal output terminal OUT of the amplifier OP chip, and the 5th, 6th, 7th, and 8th pins are grounded together. One end of the capacitor C7 is connected to the 14th and 16th pins of the processor U2 and then connected to the 5V power supply, and the other end is connected to the 12th and 13th pins of the processor U2 and then grounded to GND. One end of the resistor R6 is connected to the 9th pin of the processor U2 and then connected in parallel with the 17th pin of the processor U1 in the digital signal acquisition and processing unit module, and the other end is connected to the 5V power supply. One end of the resistor R7 is connected to the 10th pin of the processor U2 and then connected in parallel with the 16th pin of the processor U1 in the digital signal acquisition and processing unit module, and the other end is connected to the 5V power supply. The digital signal acquisition and processing unit module includes a processor U1, a reset circuit unit, and a crystal oscillator circuit unit, where: The reset circuit unit is electrically connected to the 9th pin of the processor U1; the crystal oscillator circuit unit is electrically connected to the 18th and 19th pins of the processor U1 respectively.

2. A weak signal acquisition circuit applied to a single-channel lead salt photodetector as described in claim 1, Characterized in that, The processor U2 in the analog-to-digital conversion unit module is a PCF8591 chip.

3. A weak signal acquisition circuit applied to a single-channel lead salt photodetector as described in claim 1, characterized in that, the processor U1 in the digital signal acquisition and processing unit module is an STC89C52 chip.

4. A weak signal acquisition circuit applied to a single-channel lead salt photodetector as described in claim 1, characterized in that, the voltage division and matching resistor unit module includes: a detector r, a matching resistor RL; the detector r in the voltage division and matching resistor unit module is a lead salt photodetector, which is used as a signal source to generate the required analog signal; the D end of the detector r is connected to a 5V power supply, the S end is connected to the matching resistor RL, and the GND end is grounded after being connected to the other end of RL; among them, a resistor RL with an accuracy of 5% and a resistance value matching the dark resistance of the detector r is used to make the signal more stable.

5. A weak signal acquisition circuit applied to a single-channel lead salt photodetector as described in claim 1, characterized in that, the capacitor C1 in the DC blocking and filtering circuit unit module is a chip capacitor with an accuracy of ±20%, which is used to block the DC voltage part in the signal; the resistor R3 is a chip resistor with an accuracy of 5%, and is connected in parallel with the capacitor C1 to form an RC circuit, the purpose of which is to filter out part of the noise in the 5V bias voltage.

6. A weak signal acquisition circuit applied to a single-channel lead salt photodetector as described in claim 1, characterized in that, the feedback resistor R1 in the signal amplification circuit unit module is a chip resistor with an accuracy of 5%, which is connected between the inverting input terminal IN- and the signal output terminal OUT of the amplifier OP chip; the resistor R2 is a chip resistor with an accuracy of 5%, one end of which is connected to the resistor R1 and the inverting input terminal IN- of the amplifier OP chip, and the other end is connected to GND.

7. A weak signal acquisition circuit applied to a single-channel lead salt photodetector as described in claim 1, characterized in that, the resistor R6 in the analog-to-digital conversion unit module is a chip resistor with an accuracy of 5%, and the capacitor C7 is a chip capacitor with an accuracy of ±20%.

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