Sapd-oriented weak current and avalanche voltage pulse sampling system

Abstract

The application discloses a weak current and avalanche voltage pulse sampling system for SAPD, which comprises a power module, a detection sampling module and a control processing module. The power module provides working voltage for the detection sampling module and the control processing module. The control processing module receives control instructions from an upper computer, communicates with the detection sampling module through an I / O interface, switches the working mode of the SAPD sensor, receives the sampling signal output by a sampling processing circuit and returns the sampling information to the upper computer. The detection sampling module can control the peripheral circuit through the program control instruction of the upper computer, so that the SAPD can be switched between the linear mode and the Geiger mode, the connection between the SAPD sensor and the linear sampling processing circuit or the Geiger sampling processing circuit is switched through a mode conversion circuit, the SAPD sensor is scanned in the full voltage range, and the full working domain range sampling of the SAPD is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-precision measurement, and relates to sampling measurement of weak signals, in particular to a weak current and avalanche voltage pulse sampling system for SAPD. BACKGROUND

[0002] A silicon carbide avalanche diode (SAPD) is a high-performance photodetector. According to different working voltages, SAPD mostly works under reverse bias and can be divided into two working modes: (1) When the reverse bias voltage of SAPD is lower than its avalanche voltage, SAPD plays a linear amplification role on incident photoelectrons, that is, linear mode, which can generate a photoelectric current of nanoamperes to microamperes. (2) When the reverse bias voltage of SAPD reaches its avalanche voltage, its gain rapidly increases, which can reach 10 5 ~10 6 At this time, a single photon absorption can make the output current reach saturation, that is, Geiger mode. In Geiger mode, the pn junction electric field of SAPD is very high, and photoelectrons and holes collide and ionize, and the current of SAPD will continuously increase, and a self-sustaining avalanche multiplication process occurs. Therefore, SAPD working in Geiger mode can trigger a high avalanche current to generate a milliamperes-level voltage pulse as long as there are a few photo-generated carriers in the multiplication layer. Therefore, SAPD can realize weak light detection or even single-photon detection. Compared with traditional silicon-based avalanche photodiodes (APD), SAPD has a wider band gap and higher thermal stability, and can maintain excellent performance in extreme environments. In addition, SAPD also has a fast response time and low dark current, and is widely used in signal amplification and detection in optical communication systems, as well as high-precision photoelectric detection in the fields of biomedical imaging, environmental monitoring and space exploration.

[0003] In order to realize SAPD-based detection, it is necessary to sample the nanoampere or even picoampere weak signals generated by SAPD. Such signals are weak and difficult to detect, and need to be amplified. However, the weak signal and the leakage current, bias current and other parameters of the device are in the same order of magnitude or even more weak, and in the transmission and conditioning process, the noise such as electric field or magnetic field is coupled, so that the signal-to-noise ratio of the current signal is low, and even the signal is overwhelmed by the noise.

[0004] Prior art 1 (CN109782142A) discloses a GIS (gas insulated metal enclosed switchgear) partial discharge detection device and system, which uses SAPD as an optical sensor, applies reverse bias to SAPD to make it work in Geiger mode, generates avalanche current when detecting optical signal, and realizes high-sensitivity GIS partial discharge detection device. Prior art 2 (CN113720447B) discloses a gated silicon-based visible near-infrared single-photon detection device, which uses FPGA, high-speed CMOS driver and radio frequency transformer to adjust the width, frequency and amplitude of the pulse, generates a large voltage gating pulse with short rise and fall time, thereby improving single-photon detection efficiency, reducing dark count and after-pulse probability, filtering out the spike noise caused by the front and rear edges of the gating pulse, and realizing the counting of avalanche signals.

[0005] However, due to the problems in the preparation process, even the same batch of SAPD developed by the same manufacturer has differences in electrical performance, and the parameters such as avalanche voltage, responsivity and quantum efficiency are not the same. In addition, the normal working voltage range of SAPD is 0V~200V, but the working current range is very narrow, generally not more than 1mA, so the requirements for bias voltage power supply scheme and current limiting protection scheme are high. When using SAPD single tube as a detection sensor, the detection device needs to be recalibrated to adapt to SAPD, and even some detection devices can only adapt to SAPD of specific process and model. If a new SAPD is used for detection sampling, a whole new detection circuit system must be replaced or designed to adapt to SAPD. In addition, when the measured light power is strong, the detection personnel only need SAPD to work in the linear region to detect the photocurrent, and when the measured light power is weak, the detection personnel need SAPD to work in the Geiger region to detect the number of avalanche pulses. However, the prior art lacks a scheme that can switch the working mode of SAPD. SUMMARY

[0006] In view of the shortcomings of the prior art, the present application provides a weak current and avalanche voltage pulse sampling system for SAPD, which can control the peripheral circuit through the program control instruction of the upper computer, so that SAPD can be switched between linear mode and Geiger mode. At the same time, the SAPD in the system can be scanned in the full voltage range to realize the full working domain sampling of SAPD.

[0007] A weak current and avalanche voltage pulse sampling system for SAPD, comprising a power module, a detection sampling module and a control processing module.

[0008] The power module is connected with the alternating current power supply through the power adapter, charges the lithium battery pack or provides working voltage for the detection sampling module and the control processing module.

[0009] The detection sampling module comprises an anti-reverse connection circuit, a voltage conversion circuit, a SAPD sensor, a mode conversion circuit, a linear sampling processing circuit and a Geiger sampling processing circuit. The voltage conversion circuit is connected with the output of the power module through the anti-reverse connection circuit, converts the output voltage of the power module into different working voltages, and supplies power to the SAPD sensor, the linear sampling processing circuit and the Geiger sampling processing circuit. The mode conversion circuit switches the connection of the SAPD sensor with the linear sampling processing circuit or the Geiger sampling processing circuit according to the instruction of the control processing module. The linear sampling processing circuit and the Geiger sampling processing circuit receive the output signal of the SAPD sensor, process it and return it to the control processing module.

[0010] The linear sampling processing circuit adopts a two-stage amplification scheme. Firstly, the weak light-induced current output by the positive electrode of the SAPD sensor is converted into voltage and amplified through a transimpedance amplifier circuit. Then, the voltage is further amplified through a multiplexer and an operational amplifier circuit. The control end of the multiplexer is connected with the control processing module, and different resistance positions are selected according to the instruction of the control processing module to change the amplification multiple of the reverse proportional amplification circuit.

[0011] The Geiger sampling processing circuit comprises a DAC circuit, an amplifier circuit, a comparator circuit and a quenching circuit. The avalanche voltage pulse signal output by the positive electrode of the SAPD sensor is amplified through the amplifier circuit. The DAC circuit provides a reference voltage with adjustable amplitude for the comparator circuit according to the instruction of the control processing module. The comparator circuit compares the signal output by the amplifier circuit with the reference voltage and outputs the comparison result to the control processing module. The quenching circuit is used for current quenching and device resetting of the SAPD sensor in an excited state.

[0012] The control processing module uses an FPGA as a control chip, receives the control instruction from the host computer, communicates with the detection sampling module through an I / O interface, switches the working mode of the SAPD sensor, receives the sampling signal output by the sampling processing circuit, and returns the sampling information to the host computer.

[0013] As a preferred embodiment, the control processing module further comprises a hardware noise reduction module. The hardware noise reduction module filters out high-frequency burrs in the sampling signal output by the sampling processing circuit through the combination of RC low-pass filtering and second-order active filtering, sets a hysteresis threshold to shape the signal by using a Schmidt trigger, and discriminates the pulse width by using a monostable trigger.

[0014] As a preferred embodiment, the host computer removes isolated noise pulses in the sampling information returned by the control processing module by using a baseline detection dynamic threshold algorithm, combining median filtering and pulse correlation detection, and establishes a signal state model by using Kalman filtering to predict and correct noise interference.

[0015] In linear mode, the voltage conversion circuit provides a bias voltage less than the avalanche voltage for the SAPD sensor under the control of the control processing module, and samples the weak light-generated current signal output by the SAPD sensor through the linear sampling processing circuit. In the Geiger region mode, the voltage conversion circuit provides a bias voltage greater than the avalanche voltage for the SAPD sensor under the control of the control processing module, and uses the Geiger sampling processing circuit to sample the weak avalanche voltage pulse signal output by the SAPD sensor.

[0016] The present application has the following beneficial effects:

[0017] 1. It can provide 10V~200V non-polar adjustable bias voltage for SAPD: using a non-isolated Fly-back circuit in series with a high-voltage LDO combined with a digital positioner circuit scheme, it realizes the conversion from 8.1V~12.6V voltage of 3 series 2 parallel lithium battery pack to 10V~200V non-polar adjustable power supply voltage, and the power supply voltage ripple is as low as mV level, which can provide wide range of bias voltage power supply for most SAPD, and realize the switching of SAPD in linear mode and Geiger mode.

[0018] 2. It can automatically scan the full working voltage range of SAPD: using FPGA chip to control the digital positioner to scan the voltage from 10V~200V of SAPD, and the starting voltage, termination voltage and voltage step can be set.

[0019] 3. It can automatically select the amplification gain in linear region sampling mode: using a scheme of transimpedance amplifier circuit in series with program-controlled amplifier circuit to sample the weak current of SAPD in linear region, and the FPGA chip of the processing board can automatically select the amplification gain by controlling the channel selector of the program-controlled amplifier circuit.

[0020] 4. It can adjust the sampling sensitivity of single photon avalanche voltage pulse in Geiger region sampling mode: using a scheme of amplifier in series with comparator combined with digital-to-analog converter, when weak avalanche voltage pulse signal is generated on SAPD in Geiger region, the circuit will amplify and filter and output to the FPGA chip of the processing board for pulse counting, and the FPGA chip can adjust the sensitivity of the sampling circuit to the avalanche voltage pulse signal by controlling the digital-to-analog chip. Through the cooperation of hardware circuit and software algorithm, the pulse noise suppression rate under no light condition is more than 90%.

[0021] 5. In Geiger region sampling mode, SAPD can be actively quenched or passively quenched by selecting the circuit. Using a scheme of passive quenching resistor in parallel with active quenching circuit, when the system is in Geiger region sampling mode, the processing board module can select the active or passive quenching circuit to quench the SAPD through the selection circuit, which is efficient and suitable for multiple scenarios. Attached Figure Description

[0022] Figure 1 A schematic diagram of a weak current and avalanche voltage pulse sampling system architecture for SAPD;

[0023] Figure 2 A schematic diagram of a weak current and avalanche voltage pulse sampling system for SAPD;

[0024] Figure 3 This is a schematic diagram of a non-isolated Flyback circuit.

[0025] Figure 4 This is a schematic diagram of a high-voltage LDO circuit;

[0026] Figure 5 This is a schematic diagram of a linear sampling processing circuit;

[0027] Figure 6 This is a schematic diagram of the Geiger sampling processing circuit;

[0028] Figure 7 A schematic diagram of a passive quenching resistor connected in parallel with an active quenching circuit;

[0029] Figure 8 This is a diagram of the output signal of the linear sampling processing circuit when the SAPD is operating in the linear region. Detailed Implementation

[0030] The present invention will be further explained below with reference to the accompanying drawings;

[0031] like Figure 1 As shown, a weak current and avalanche voltage pulse sampling system for SAPD includes a power supply module, a detection and sampling module, and a control and processing module.

[0032] like Figure 2 As shown, the overall system structure adopts a modular design. The external structure consists of front and rear covers, a two-piece hatch cover, and a base, forming a complete protective frame. The internal structure integrates components such as raised columns, interface boards, and development board mounting bases. Through optimized layout based on structural mechanics, the system can effectively ensure safety and stability during operation.

[0033] The power module is a 3-series, 2-parallel 18650 lithium battery pack, providing an operating voltage of 8.1V~12.6V for the detection and sampling module and the control processing module. The power module has a DC-05 female input terminal, which can be connected to an AC power source via a power adapter to charge the lithium battery pack or directly power the detection and sampling module and the control processing module.

[0034] The detection sampling module comprises an anti-reverse connection circuit, a voltage conversion circuit, a SAPD sensor, a mode conversion circuit, a linear sampling processing circuit and a Geiger sampling processing circuit. The voltage conversion circuit is connected with the output of the power module through the anti-reverse connection circuit, converts the output voltage of the power module into different working voltages, and supplies power to the SAPD sensor, the linear sampling processing circuit and the Geiger sampling processing circuit. The mode conversion circuit switches the connection of the SAPD sensor with the linear sampling processing circuit or the Geiger sampling processing circuit according to the instruction of the control processing module. The linear sampling processing circuit and the Geiger sampling processing circuit receive the output signal of the SAPD sensor and return to the control processing module after processing.

[0035] The anti-reverse connection circuit is composed of a diode and a fuse. When the circuit is reversed, the fuse and the diode will cut off the circuit to prevent the reversed voltage from continuing to supply power to the circuit.

[0036] The voltage conversion circuit comprises an 8.1V-12.6V to +5V power supply circuit, an 8.1V-12.6V to -5V power supply circuit, an 8.1V-12.6V to 3.3V power supply circuit, an 8.1V-12.6V to 220V power supply circuit and a high-voltage LDO circuit, which can provide 220V, 20V-180V, ±5V and 3.3V power supply outputs.

[0037] The 8.1V-12.6V to +5V power supply circuit adopts a DCDC series LDO (low dropout linear regulator) circuit scheme. The DCDC circuit adopts a BUCK type voltage drop circuit to reduce the voltage output by the power module to 7.5V, and then the LDO circuit further reduces the +7.5V voltage to +5V. The output capacity of the 8.1V-12.6V to +5V power supply circuit reaches 5V / 1A level, and the output voltage ripple is as low as mV level, greatly filtering out the noise generated by the external power adapter or DCDC circuit.

[0038] The 8.1V-12.6V to 3.3V power supply circuit is similar to the 8.1V-12.6V to +5V power supply circuit. First, a BUCK type voltage drop circuit is used to reduce the voltage output by the power module to +4.5V, and then an LDO circuit is used to further reduce the +4.5V voltage to +3.3V. The output capacity of the 8.1V-12.6V to 3.3V power supply circuit reaches 3.3V / 1A level.

[0039] The 8.1V-12.6V to -5V power supply circuit adopts a DCDC series LDO circuit scheme. First, an Inverting type voltage boost and buck circuit is used to reduce the voltage output by the power module to -6.0V, and then an LDO circuit is used to further reduce the -6.0V voltage to -5.0V. The output capacity of the 8.1V-12.6V to -5V power supply circuit reaches -5.0V / 0.1A level.

[0040] The 8.1V~12.6V to 220V power supply circuit adopts the following... Figure 3 The non-isolated Flyback circuit topology shown increases the output voltage of the power module to 220V.

[0041] The high-voltage LDO circuit uses, for example Figure 4 The high-voltage output adjustable LDO scheme shown uses a 256-bit precision digital positioner AD5272BRMZ-50 as the feedback resistor, powered by an 8.1V~12.6V to 3.3V power supply circuit. It communicates with the control processing module through the IIC communication protocol, adjusts the resistance value, and outputs a voltage of 20~180V.

[0042] The SAPD sensor is a silicon carbide avalanche photodiode, which is plugged into the detection and sampling module via a TO-18 package. The negative terminal of the SAPD sensor is connected to the output of the high-voltage LDO circuit, and the positive terminal is connected to either the linear sampling processing circuit or the Geiger sampling processing circuit via a mode conversion circuit. The SAPD sensor can switch between linear mode and Geiger mode depending on the output voltage of the high-voltage LDO circuit.

[0043] The mode conversion circuit is a single-pole double-throw magnetic latching relay driven by an NMOS circuit, powered by an 8.1V~12.6V to +5V power supply circuit. The control terminal of the NMOS circuit is connected to the control processing module, and drives the single-pole double-throw magnetic latching relay according to the instructions of the control processing module, changing the connection relationship between the SAPD sensor and the linear sampling processing circuit and the Geiger sampling processing circuit.

[0044] When the SAPD sensor operates in linear mode, its output photocurrent is very weak, requiring current-to-voltage conversion and amplification via circuitry. For example... Figure 5As shown, the linear sampling processing circuit adopts a two-stage amplification scheme. The first stage amplification adopts a transimpedance amplifier circuit to convert the weak light-induced current output by the positive electrode of the SAPD sensor into a voltage and amplify it through an amplification resistor. Compared with the feedback integration method and the sampling resistor method, the transimpedance amplification method has higher detection accuracy and the output voltage will not produce integral drift, which can well adapt to the signal processing requirements of the SAPD sensor in linear mode. The second stage amplification adopts a multiplexer and an operational amplifier circuit. The multiplexer U26 is connected in parallel with the reverse proportional amplification circuit. The control terminals A0, A1, A2 and EN of the multiplexer U26 are connected to the control processing module. According to the instructions of the control processing module, different resistance positions are selected to change the amplification factor of the reverse proportional amplification circuit, and the voltage output by the transimpedance amplifier circuit is amplified twice, and then transmitted to the control processing module through the output port of the operational amplifier U28. By setting the resistors R157~R159, R161, R163, R165~R167, the amplification factor of the reverse proportional amplification circuit can be designed as 1 times, 1.5 times, 2 times, 5 times, 8 times, 10 times or 15 times. The operational amplifiers U27 and U28 are powered by the 8.1V~12.6V to +5V power supply circuit and the 8.1V~12.6V to -5V power supply circuit.

[0045] Under a very high bias voltage, the SAPD sensor works in Geiger mode and outputs avalanche pulses. After sampling, the SAPD sensor in the excited state needs to be current quenched and reset. This includes active quenching and passive quenching. The active quenching refers to the process of quickly suppressing the avalanche current after the SAPD sensor occurs avalanche multiplication effect, so that the SPAD returns to the initial state through an external circuit. Passive quenching is to achieve the quenching of the avalanche current and the reset of the SPAD sensor through the characteristics of the SAPD sensor itself or passive quenching resistor.

[0046] The Geiger sampling processing circuit includes a DAC circuit, an amplifier circuit, a comparator circuit, an active quenching circuit and a passive quenching resistor. As shown, Figure 6 First, the amplifier circuit composed of the operational amplifier U29 amplifies the avalanche voltage pulse signal output by the positive electrode of the SAPD sensor, and then inputs the positive input terminal of the comparator U30. The inverting input terminal of the comparator U30 is connected to the output of the DAC circuit. The amplified avalanche pulse signal and the reference voltage are compared, and the comparison result is output to the control processing module. The DAC circuit adopts a 16-bit high-precision DAC chip, which communicates with the control processing module through the IIC communication protocol. According to the instructions of the control processing module, the output voltage of the DAC chip is adjusted to provide a adjustable reference voltage in the range of 0V~2V for the comparator circuit, so as to realize the sensitivity adjustment of the Geiger sampling processing circuit to the avalanche pulse signal output by the SPAD sensor.Figure 7 As shown, the active quenching circuit is composed of a low-side NMOS tube and a high-side PMOS tube, and the low-side NMOS tube Q6 is responsible for driving the high-side PMOS tube Q8. After the avalanche multiplication of the SPAD sensor occurs, the avalanche voltage pulse signal output by the positive electrode of the SAPD sensor passes through the amplifier circuit and the comparator circuit, and the output signal drives the MOS tube of the active quenching circuit to drive the high-side PMOS tube Q8 of the active quenching circuit to discharge the SAPD anode voltage, thereby realizing the active quenching of the SPAD. The passive quenching resistor is a 10KΩ resistor R212 connected to the anode of the SAPD sensor. After the avalanche multiplication of the SAPD sensor occurs, the passive quenching resistor automatically realizes passive quenching.

[0047] The control processing module uses an FPGA as a control chip, is powered by a 8.1V~12.6V to +5V power supply circuit, communicates with the detection and sampling module through an I / O interface to realize the switching of the working mode of the SAPD sensor and the reading of the sampling signal. Moreover, the control processing module has multiple communication interfaces and can communicate with the host computer, receive control instructions from the host computer, and return sampling information to the host computer.

[0048] The sampling system can realize the detection and collection of weak current and avalanche voltage pulses of the SAPD sensor in linear mode and Geiger mode. After amplification and filtering, the pulse waveform read by the control processing module is as shown in Figure 8 In linear mode, the system can detect the weakest current signal level of 10nA, the adjustable gain range is 6dB~40dB, and the output signal ripple is less than 10mV. In Geiger mode, the system can detect the weakest voltage signal level of 10mV, the adjustable gain range is 6dB~30dB, and the output signal ripple is less than 10mV. Therefore, the application can effectively detect the photoelectric signal output by the SAPD sensor and realize weak current sampling.

Claims

1. A weak current and avalanche voltage pulse sampling system for SAPD, comprising a power supply module, a detection sampling module and a control processing module, the power supply module provides working voltage for the detection sampling module and the control processing module, the detection sampling module comprises a voltage conversion circuit for converting the output voltage of the power supply module into different working voltages, a SAPD sensor and a sampling processing circuit for sampling the output of the SAPD sensor and transmitting it to the control processing module, the control processing module is used for receiving the sampling signal output by the sampling processing circuit and returning the sampling information to the upper computer; characterized in that: the detection sampling module further comprises a mode conversion circuit, the sampling processing circuit comprises a linear sampling processing circuit and a Geiger sampling processing circuit; the voltage conversion circuit provides different sizes of bias voltage for the SAPD sensor according to the instruction of the control processing module, and switches the SAPD sensor to work in linear mode or Geiger mode; the mode conversion circuit switches the connection of the SAPD sensor with the linear sampling processing circuit or the Geiger sampling processing circuit according to the instruction of the control processing module; the linear sampling processing circuit is used for converting the current output by the positive electrode of the SAPD sensor into a voltage signal and amplifying it, and the Geiger sampling processing circuit is used for comparing the size of the positive electrode output signal of the SAPD sensor with the reference voltage and driving the quenching circuit to quench the current of the SAPD sensor in the excited state and reset the device; the control processing module receives the control instruction from the upper computer, communicates with the detection sampling module, and switches the working mode of the SAPD sensor. The control processing module further comprises a hardware noise reduction module.

2. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 1, wherein: The hardware noise reduction module is a combination of RC low-pass filter and second-order active filter, which filters out high-frequency burrs in the sampling signal output by the sampling processing circuit, and uses a Schmidt trigger to set a hysteresis threshold to shape the signal, and combines a monostable trigger to identify the pulse width.

3. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 2, wherein: Through the baseline detection dynamic threshold algorithm, combined with median filtering and pulse correlation detection, the isolated noise pulses in the sampling information returned by the control processing module are removed, and the Kalman filter is used to establish a signal state model to predict and correct noise interference.

4. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 1, wherein: In the linear mode, the voltage conversion circuit provides a bias voltage less than the avalanche voltage for the SAPD sensor under the control of the control processing module, and samples the weak light-induced current signal output by the SAPD sensor through the linear sampling processing circuit; in the Geiger region mode, the voltage conversion circuit provides a bias voltage greater than the avalanche voltage for the SAPD sensor under the control of the control processing module, and uses the Geiger sampling processing circuit to sample the weak avalanche voltage pulse signal output by the SAPD sensor.

5. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 1, wherein: The voltage conversion circuit comprises 8.1V~12.6V to +5V power supply circuit, 8.1V~12.6V to -5V power supply circuit, 8.1V~12.6V to 3.3V power supply circuit, 8.1V~12.6V to 220V power supply circuit and high-voltage LDO circuit, providing 220V, 20V~180V, ±5V, 3.3V multiple power output.

6. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 1 or 5, wherein: ​ 7. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 6, wherein: The high-voltage LDO circuit adopts a high-voltage output adjustable LDO scheme, uses a digital positioner as a feedback resistor, communicates with a control processing module through an IIC communication protocol, adjusts the resistance value of the digital positioner, and outputs a voltage varying from 20V to 180V; the output section of the high-voltage LDO circuit is connected to the negative electrode of the SAPD sensor, and provides a bias voltage for the SAPD sensor.

8. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 1, wherein: The linear sampling processing circuit adopts a two-stage amplification scheme, the first-stage amplification adopts a transimpedance amplifier circuit to convert the current signal output by the positive electrode of the SAPD sensor into a voltage signal and amplify it; the second-stage amplification adopts a reverse proportional amplification circuit in parallel with a multi-channel selector, wherein the control end of the multi-channel selector is connected to the control processing module, different resistance positions are selected according to the instruction of the control processing module, the amplification multiple of the reverse proportional amplification circuit is changed, and the output end of the reverse proportional amplification circuit is connected to the control processing module.

9. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 8, wherein: The amplification multiple of the reverse proportional amplification circuit is controlled by the multi-channel selector to be 1 times, 1.5 times, 2 times, 5 times, 8 times, 10 times or 15 times.

10. The SAPD oriented weak current and avalanche voltage pulse sampling system of claim 1, wherein: The Geiger sampling processing circuit includes a DAC circuit, an amplifier circuit, a comparator circuit, an active quenching circuit and a passive quenching resistor; the amplifier circuit amplifies the avalanche voltage pulse signal output by the positive electrode of the SAPD sensor, and then inputs the signal into the comparison end of the comparator circuit; the reference voltage end of the comparator circuit is connected to the output of the DAC circuit, the amplified avalanche pulse signal and the reference voltage are compared, and the comparison result is output to the control processing module; the DAC circuit adjusts the output voltage of the DAC chip according to the instruction of the control processing module, and provides a reference voltage with adjustable size for the comparator circuit; the active quenching circuit is composed of a low-side NMOS tube and a high-side PMOS tube, and the low-side NMOS tube Q6 is responsible for driving the high-side PMOS tube; after avalanche multiplication occurs in the SPAD sensor, the avalanche voltage pulse signal output by the positive electrode of the SAPD sensor passes through the amplifier circuit and the comparator circuit, and the output signal drives the MOS tube of the active quenching circuit to drive the high-side PMOS tube of the active quenching circuit to discharge the SAPD anode voltage, thereby realizing active quenching of the SPAD; the passive quenching resistor is connected to the anode resistor of the SAPD sensor, and after avalanche multiplication occurs in the SAPD sensor, passive quenching is automatically realized through the passive quenching resistor.

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