阅读说明：本技术 一种光电器件脉冲宽度调制方法及外置淬灭辅助电路 (Pulse width modulation method and external quenching auxiliary circuit for photoelectric device ) 是由 杨明洁 张寿山 于 2021-08-04 设计创作，主要内容包括：本发明公开了一种光电器件脉冲宽度调制方法及外置淬灭辅助电路。本方法为：1)在光电器件的工作读出电路上添加外置灭辅助电路；2)所述外置淬灭辅助电路判断所述光电器件是否产生有效脉冲信号,当产生有效脉冲信号时产生一个逻辑高电平信号,经过一定延迟时间t-(integral)后,该逻辑高电平信号切断所述光电器件阳极偏置电压和阴极脉冲输出通道,并将所述光电器件的阴阳极共地短接；然后所述外置淬灭辅助电路输出一逻辑低电平信号,恢复所述光电器件的正常工作。本发明从SiPM内部工作物理过程上缩短SiPM的淬灭恢复时间,进一步调制缩短SiPM输出脉冲宽度。(The invention discloses a pulse width modulation method of a photoelectric device and an external quenching auxiliary circuit. The method comprises the following steps: 1) an external extinguishing auxiliary circuit is added on a work reading circuit of the photoelectric device; 2) the external quenching auxiliary circuit judges whether the photoelectric device generates an effective pulse signal or not, generates a logic high level signal when the effective pulse signal is generated, and delays for a certain delay time t integral Then, the logic high level signal cuts off the anode bias voltage and the cathode pulse output channel of the photoelectric device and short-circuits the cathode and the anode of the photoelectric device in common; and then the external quenching auxiliary circuit outputs a logic low level signal to recover the normal work of the photoelectric device. The invention shortens the quenching recovery time of the SiPM from the internal working physical process of the SiPM, and further modulates and shortens the output pulse width of the SiPM.)

1. A method of pulse width modulation of an optoelectronic device comprising the steps of:

1) an external extinguishing auxiliary circuit is added on a work reading circuit of the photoelectric device;

2) the external quenching auxiliary circuit judges whether the photoelectric device generates an effective pulse signal or not, generates a logic high level signal when the effective pulse signal is generated, and delays for a certain delay time t_integralThen, the logic high level signal cuts off the bias voltage and the pulse output channel of the photoelectric device and short-circuits the cathode and the anode of the photoelectric device in common; and then the external quenching auxiliary circuit outputs a logic low level signal to recover the normal work of the photoelectric device.

2. The method of claim 1, wherein the delay time isWherein Sf is the sampling frequency of the data acquisition card to the pulse signal generated by the SiPM, and n is the ratioMost stable value, Q_nIntegrating charge integration results Q of n sampling points for sampling from the maximum value of the output pulse of the photoelectric device_n，Q₀The total charge generated for avalanche quenching within the optoelectronic device.

3. The method of claim 2,wherein, t_peakIn order to be the time of the rising edge,

i_tthe current at time t.

4. The method of claim 2, wherein the delay time is adjustably controlled by controlling an LC or RC delay circuit.

5. The method of claim 4, wherein the delay time is adjustably controlled by an RC delay circuit; the resistor of the RC delay circuit is a digital resistor or a common analog resistor, and when the resistor is a digital resistor, the resistance value of the digital resistor is adjusted in real time through the FPGA or the singlechip.

6. The method of claim 1, wherein the external quench assist circuit determines whether the optoelectronic device is generating an active pulse signal by a comparator circuit leading edge trigger, the comparator circuit outputting a logic high level when the active pulse signal is generated.

7. The method of any of claims 1 to 6, wherein the optoelectronic device is a silicon photomultiplier or an avalanche photodiode.

8. An external quenching auxiliary circuit for pulse width modulation of a photoelectric device is characterized by comprising an amplifying circuit, a comparing circuit, a time delay unit and a group of controllable switches; wherein the content of the first and second substances,

the amplifying circuit is used for amplifying the output pulse signal of the photoelectric device with low noise;

the comparison circuit is used for judging whether the photoelectric device generates an effective pulse signal or not, outputting a logic high level and sending the logic high level to the time delay unit when the effective pulse signal is generated, and otherwise outputting a logic low level and sending the logic low level to the time delay unit;

the time delay unit is used for controlling the controllable switch according to the received signal, wherein when the logic high level signal is received, the time t is delayed_integralPost-cutting off the photovoltaicThe device bias voltage and the pulse output channel are connected in short circuit in a common mode; and restoring the normal operation of the photoelectric device when the logic low level signal is received.

9. The external quench assist circuit of claim 8 wherein the delay time isWherein Sf is the sampling frequency of the data acquisition card to the pulse signal generated by the SiPM, and n is the ratioMost stable value, Q_nIntegrating charge integration results Q of n sampling points for sampling from the maximum value of the output pulse of the photoelectric device_n，Q₀The total charge generated for avalanche quenching within the optoelectronic device.

10. The external quench aid circuit of claim 8 wherein an anode of said optoelectronic device is connected to one end of a first controllable switch and a cathode of said optoelectronic device is connected to one end of a second controllable switch; the other end of the first controllable switch is respectively used for being connected with a signal output end, a grounding end and a power supply end Vbias of the time delay unit, and the other end of the second controllable switch is respectively used for being connected with a signal input end, a grounding end and a signal input end of the amplifying circuit of the time delay unit.

Technical Field

The invention belongs to the technical field of particle detection, particularly relates to the field of photoelectric detection, and particularly relates to a pulse width modulation method of a photoelectric device and an external quenching auxiliary circuit.

Background

A silicon photomultiplier (SiPM) is a novel photoelectric conversion device (born in the 90's of the 20 th century) and is formed by connecting in parallel a large number of Avalanche Photodiode (APD) arrays operating in the geiger mode. Incident photons strike the surface of the SiPM, so that APD infinitesimal under the Geiger mode generates avalanche and generates a pulse with a certain amplitude, and the output pulse of the SiPM is equal to the superposition of avalanche pulse of each avalanche APD infinitesimal. Since the APD avalanche current pulse size is related only to the bias voltage and the internal quench resistance, the SiPM output pulse size is proportional to the number of avalanche APD microcells occurring, and further proportional to the number of photons incident on the SiPM surface.

The SiPM has compact structure, large gain, low working voltage, insensitivity to magnetic field, fast response rise time of optical signals, good uniformity and difficult aging under exposure conditions, so the SiPM is widely applied to the fields of nuclear physics, nuclear medicine, high-energy particle physics, cosmic ray physics, laser ranging, quantum communication and the like. Compared with a photomultiplier tube (PMT), the SiPM serving as a photoelectric device can meet the requirements of photoelectric conversion detection, and is more suitable for being applied to magnetic field environments, high-altitude areas, night sky space line and background observation and development of portable equipment.

However, due to the influence of the quenching resistor with large internal resistance and the junction capacitance, the pulse width (especially the falling edge of the pulse signal) of the SiPM light detection output is far larger than that of the PMT. This not only increases the dead time zone of the detector, but also introduces excessive background noise into the effective pulse signal, which degrades the signal-to-noise ratio of the pulse signal. The SiPM of the SensL has a 'Fast Output' pin, so that Fast signals with Fast rising time and narrow pulse width can be taken out, but the charge quantity of the Fast signals is only about 2% of the charge generated by SiPM avalanche, and the SiPM is suitable for timing measurement but not suitable for energy measurement; the fermi national laboratory adopts a high-pass filter circuit to effectively shorten the output pulse width of the SiPM, but also greatly reduce the pulse amplitude. It seems that the pulse width problem that has been solved has not been solved satisfactorily and the quench recovery time of sipms is still long.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a pulse width modulation method of a photoelectric device and an external quenching auxiliary circuit. The external SiPM quenching auxiliary circuit is designed based on a comparison circuit, a leading edge trigger technology and a high-speed analog switch, the quenching recovery time of the SiPM is shortened in the internal working physical process of the SiPM, and the output pulse width of the SiPM is further shortened by modulation.

The silicon photomultiplier has very fast photo-detection response time, but the back edge of the output pulse signal of the SiPM is too slow due to the overlong charge release time of the internal large-resistance quenching resistor. The invention adds an external auxiliary circuit for extinguishing on a work reading circuit of the SiPM to assist the large-resistance quenching resistor in the SiPM to finish the charge release process. The external quenching auxiliary circuit design framework is as follows:

A) judging whether the SiPM effectively responds or not and whether an effective pulse signal is output or not;

B) after the SiPM effectively responds, after a period of time delay, the cathode and the anode of the SiPM are short-circuited in a common ground mode, and the charge release process of the large-resistance avalanche quenching resistor is accelerated;

C) the delay time is adjusted, controlled and adjusted through inductance, resistance and capacitance parameters of the LC or RC delay circuit, and the SiPM output pulse width is modulated to achieve the best effect, namely, the pulse width is shortened on the premise of not losing the amplitude of the output pulse signal and achieving the best response efficiency to the incident light intensity. According to the physical process of SiPM avalanche quenching, the integral of the rising edge of the SiPM output current pulse along with time is the total charge number generated by SiPM internal avalanche quenching(where i is current and t is time); adding random noise at the falling edge of the SiPM pulse, and simulating and calculating the charge integration result of sampling and integrating n sampling points from the maximum value of the output pulse of the SiPM by using the actual sampling frequency Sf (such as 1GHz, 500MHz, 50MHz and the like) of a pulse signal generated by the SiPM by using a data acquisition card:controlling variables, respectively changing random noise frequency (1 Hz-1 GHz), signal-to-noise ratio (10-100), and rising edge time t_peakDuring the process of changing the above three conditions, n is adjusted and the calculation finds the most stable RQ, among whichThe ratio of (a) to (b), when RQ is most stable,for optimal integration time. This integration time is the delay time of the "external quench aid circuit". The delay time may be fixed; the resistance of the RC delay circuit can be changed into a digital resistance, the resistance value of the digital resistance is adjusted in real time through the FPGA, and the delay time is adjusted in real time to meet the complex and changeable application scenes.

D) Since the number of incident photons changes with the energy of the radiation, the time at which the SiPM is determined to respond effectively needs to be unaffected by the number of incident photons. In the invention, the time of SiPM effective response is obtained by a leading edge triggering mode; therefore, the invention designs a low-noise fast amplifying circuit, keeps the fast rising time of the SiPM output pulse signal in a low-noise state, further reduces the effective response judgment threshold value of the SiPM, and reduces the fluctuation of the effective response judgment time along with the number of incident photons or the energy of incident rays.

Whether the SiPM generates an effective pulse signal is judged by leading edge triggering of a comparison circuit, when the effective pulse signal is generated, a comparator outputs a logic high level, after a certain time delay, the high level signal cuts off an anode bias voltage and a cathode pulse output channel of the SiPM, and a cathode and an anode of the SiPM are short-circuited in common to accelerate a charge release process of a quenching resistor in the SiPM. When the comparator circuit outputs a low level, the normal operation of the SiPM will be restored again to the line connection state.

The technical scheme of the invention is as follows:

a method of pulse width modulation of an optoelectronic device comprising the steps of:

1) an external extinguishing auxiliary circuit is added on a work reading circuit of the photoelectric device;

2) the external quenching auxiliary circuit judges whether the photoelectric device generates an effective pulse signal or not, generates a logic high level signal when the effective pulse signal is generated, and delays for a certain delay time t_integralThen, the logic high level signal cuts off the anode bias voltage and the cathode pulse output channel of the photoelectric device and short-circuits the cathode and the anode of the photoelectric device in common; however, the device is not suitable for use in a kitchenAnd then the external quenching auxiliary circuit outputs a logic low level signal to recover the normal work of the photoelectric device. The bias voltage can be applied to the anode or the cathode; the pulse output channel can be arranged at the anode or the cathode.

Further, the delay timeWherein Sf is the sampling frequency of the data acquisition card to the pulse signal generated by the SiPM, and n is the ratioMost stable value, Q_nIntegrating charge integration results Q of n sampling points for sampling from the maximum value of the output pulse of the photoelectric device_n，Q₀The total charge generated for avalanche quenching within the optoelectronic device.

Further, in the above-mentioned case,wherein, t_peakFor rising edge time, i_tThe current at time t.

Furthermore, the external quenching auxiliary circuit judges whether the photoelectric device generates an effective pulse signal or not through the leading edge trigger of the comparison circuit, and the comparison circuit outputs a logic high level when the effective pulse signal is generated.

Further, the optoelectronic device is a silicon photomultiplier (SiPM) or an Avalanche Photodiode (APD).

An external quenching auxiliary circuit for pulse width modulation of a photoelectric device is characterized by comprising an amplifying circuit, a comparing circuit, a time delay unit and a group of controllable switches; wherein the content of the first and second substances,

the amplifying circuit is used for amplifying the output pulse signal of the photoelectric device with low noise and simultaneously keeping the fast rising edge of the output pulse;

the comparison circuit is used for judging whether the photoelectric device generates an effective pulse signal or not, outputting a logic high level and sending the logic high level to the time delay unit when the effective pulse signal is generated, and otherwise outputting a logic low level and sending the logic low level to the time delay unit;

the time delay unit is composed of delay circuits (such as RC delay circuit, LC delay circuit, or related delay circuits such as inherent delay response time inside electronic components) and is used for providing transmission time delay t for logic high and low level signals output by the comparison circuit_integral；

The external quenching assistance is that a controllable switch (as shown in fig. 2) is respectively arranged at the cathode end and the anode end of the photoelectric device, wherein when the controllable switch receives a logic high level signal, the controllable switch disconnects the cathode and the anode of the photoelectric device from a power supply and output circuit, and the cathode and the anode of the photoelectric device are short-circuited in common to accelerate the internal discharge of the photoelectric device; when the controllable switch receives a logic low level, the switch disconnects the cathode and the anode of the photoelectric device from the ground, and the power supply and signal reading circuit is connected to enable the photoelectric device to recover to normal work.

The invention has the following advantages:

an external quenching circuit for assisting SiPM quenching is developed to modulate the avalanche quenching recovery time of the SiPM; according to the actual application requirement and the incident light time characteristic, the output pulse width of the SiPM can be shortened to the actual requirement level, and meanwhile, the output pulse amplitude of the SiPM is kept unchanged.

Drawings

FIG. 1 is a block diagram of the design of an external quench assist circuit.

FIG. 2 is a diagram of an external quenching circuit.

Detailed Description

The invention will be described in further detail with reference to the following drawings, which are given by way of example only for the purpose of illustrating the invention and are not intended to limit the scope of the invention.

The external quenching auxiliary circuit design framework of the invention is shown in figure 1, whether the SiPM generates an effective pulse signal is judged by the leading edge trigger of the comparison circuit, when the effective pulse signal is generated, the comparison circuit outputs a logic high level, after a certain time delay, the high level signal cuts off the SiPM cathode bias voltage and anode pulse output channel, and the cathode and the anode of the SiPM are short-circuited in common to accelerate the charge release process of the quenching resistor in the SiPM. When the comparison circuit outputs low level, the normal work reading circuit connection state of the SiPM is recovered again, namely the normal bias voltage of the SiPM cathode is recovered, the pulse output of the SiPM anode is recovered, and the cathode and the anode of the SiPM are disconnected with the ground.

As shown in FIG. 2, the external quenching circuit of the invention is characterized in that a photoelectric device can generate electric pulses and output the electric pulses to an amplifying circuit when receiving incident light signals in a normal working mode (namely, the anode is connected with a Vbias power supply and the cathode is connected with a pulse signal output circuit through a controllable switch); the amplifying circuit amplifies the electric pulse from the photoelectric device, and simultaneously, the signal-to-noise ratio of the output pulse signal is consistent with that of the input pulse signal; keeping the rising edge of the output pulse signal consistent with the input pulse signal; one path of output signals of the amplifying circuit is transmitted to the rear-end electronics for digital conversion and acquisition, and the other path of output signals is transmitted to the comparison circuit for judgment; once the comparison circuit judges that the analog pulse signal is an effective working signal of the photoelectric device, a logic high level is generated and output to the delay circuit; the logic high level is delayed by a time t_integralAfter reaching the controllable switch 1 and the controllable switch 2 at the cathode and anode ends of the photoelectric device, the controllable switch 1 is pulled to GND (ground) by Vbias (power supply), the controllable switch 2 is pulled to GND (ground) by the input end of the amplifying circuit, and finally the photoelectric device is disconnected from a normal working circuit, the cathode and the anode are short-circuited in common, and internal discharge is accelerated; when the comparison circuit judges that the analog pulse signal is an invalid working signal of the photoelectric device, a logic low level is generated and output to the delay circuit; the logic low level is delayed by a time t_integralAnd then reaching a controllable switch 1 and a controllable switch 2 at the cathode and anode ends of the photoelectric device, connecting the controllable switch 1 with Vbias (power supply), connecting the controllable switch 2 with the input end of the amplifying circuit, and finally connecting the photoelectric device to a normal working circuit.

Although specific embodiments of the invention have been disclosed for purposes of illustration, and for purposes of aiding in the understanding of the contents of the invention and its implementation, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.