Single-photon detector cooling control method and system with adaptive temperature and TEC performance changes

Abstract

The present invention discloses a single-photon detector refrigeration control method and system that is adaptive to temperature and TEC performance changes. The method limits the maximum operating voltage of TEC, monitors the TEC operating voltage and refrigeration temperature in real time, and automatically adjusts the target temperature and APD working bias voltage according to the monitoring results, effectively ensuring that the single-photon detector can still work stably when the working environment temperature is too high or the TEC performance is degraded. At the same time, when the ambient temperature is allowed to return to the normal temperature range, the TEC's refrigeration target temperature can be restored to the initial refrigeration target temperature and the APD's working bias voltage can be adjusted synchronously, so that the performance indicators of the single-photon detector, such as the detection efficiency, dark count rate, and after-pulse probability, will be synchronously restored to normal. In this way, the service life of TEC and single-photon detector equipment can be effectively improved, and the environmental adaptability of the single-photon detector can be improved.

Description

Technical Field

[0001] The present invention relates to the field of single-photon detectors, and in particular to a single-photon detector refrigeration control method and system, which can automatically adapt to ambient temperature changes and TEC performance degradation. Background Art

[0002] In existing single-photon detectors, the following TEC (semiconductor refrigerator) cooling control process is usually adopted, namely: the controller controls the DAC chip to provide a control voltage to the TEC dedicated driver chip, and changes the output voltage size and direction to achieve TEC cooling or heating. During the control process, the ADC chip is used to collect temperature to achieve temperature control of the single-photon detector. Figure 1 Among them, some TEC dedicated driver chips can configure their temperature control target value through external resistors, and then perform temperature PID stabilization control through resistance and capacitance values, which can further simplify the external drive circuit of the TEC controller and have a higher degree of integration.

[0003] Patent document CN111258351A specifically discloses a single-photon detector TEC temperature control scheme. In this control scheme, the DAC chip inputs a voltage V_DAC to the temperature control circuit according to the DAC digital signal control value, and the electronic components in the temperature control circuit shunt the voltage V_DAC and couple it through the capacitor group, and finally load the voltage V_TEC_P / N for adjusting the temperature of the TEC refrigerator to the two voltage input ends of the TEC refrigerator. Among them, the current or voltage upper limit is adjusted by selecting different power supply chips or the resistance value obtained by the free combination of resistors; and the temperature value and PID parameter value of the single-photon detector module controlled by the TEC refrigerator are placed in the memory, and the temperature control algorithm of the TEC is embedded in the main control unit, so there is no need for a TEC refrigeration driver chip, thereby solving the problem of insufficient voltage or current output of the TEC refrigeration chip and poor parameter consistency of the existing TEC refrigeration hardware platform, and achieving the purpose of unified parameter allocation, flexible hardware circuit design, and effective cost reduction.

[0004] However, the prior art does not mention the need for voltage protection of TEC devices, and when TEC devices work near the rated working voltage for a long time, their service life will be reduced. In addition, the prior art also does not mention how to achieve refrigeration control when the difference between the ambient temperature and the refrigeration target temperature exceeds the maximum refrigeration temperature difference of TEC. When the ambient temperature is too high or the TEC performance in the detector deteriorates, the difference between the ambient temperature and the refrigeration target temperature will exceed the maximum refrigeration temperature difference of TEC, causing TEC to be unable to cool the APD (avalanche photodiode) device temperature to the target value. At this time, temperature-related indicators such as detection efficiency, dark count rate, and post-pulse probability will fluctuate, affecting the overall performance of the single-photon detector. At the same time, in this case, in order to reach the target temperature, the TEC device will work under extreme refrigeration working conditions for a long time, and long-term use will lead to reduced performance and reliability of the TEC device. Summary of the invention

[0005] In view of the above problems existing in the prior art, the present invention discloses a single-photon detector refrigeration control method and system that is adaptive to temperature and TEC performance changes. The method limits the maximum operating voltage of TEC, monitors the TEC operating voltage and refrigeration temperature in real time, and automatically adjusts the target temperature and APD working bias voltage according to the monitoring results, effectively ensuring that the single-photon detector can still work stably when the working environment temperature is too high or the TEC performance is degraded. At the same time, when the ambient temperature is restored to the normal temperature range, the TEC's refrigeration target temperature can be restored to the initial refrigeration target temperature and the APD's working bias voltage can be adjusted synchronously, so that the performance indicators of the single-photon detector, such as the detection efficiency, dark count rate, and after-pulse probability, will be synchronously restored to normal. In this way, the service life of TEC and single-photon detector equipment can be effectively improved, and the environmental adaptability of single-photon detectors can be improved.

[0006] Specifically, a first aspect of the present invention relates to a single-photon detector cooling control method that is adaptive to temperature and TEC performance changes, which pre-sets an upper limit value of the operating voltage for the TEC and a specified minimum voltage; and

[0007] When the TEC is not cooled to the target temperature within a specified time or the operating voltage at the target temperature is higher than the upper limit of the operating voltage, increasing the target temperature and the APD bias voltage; and,

[0008] When the TEC operating voltage at the target temperature is below the specified minimum voltage, the APD bias voltage and the target temperature are reduced.

[0009] Preferably, the upper limit of the operating voltage can be set to 70% of the rated operating voltage of the TEC.

[0010] Further, the single-photon detector refrigeration control method of the present invention may include an initialization step, an adaptive temperature increase step, a specified maximum voltage monitoring step, a specified minimum voltage monitoring step, an adaptive temperature reduction step, and a refrigeration temperature monitoring step;

[0011] The initialization step is used to configure the target temperature and the APD bias voltage as the initial target temperature and the initial APD bias voltage when the power is turned on; determine whether the TEC is cooled to the target temperature within the specified time, and determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage when the TEC is cooled to the target temperature within the specified time, wherein the specified maximum voltage is set to be lower than the upper limit of the operating voltage, and if the TEC is not cooled to the target temperature within the specified time or the operating voltage at the target temperature is higher than the specified maximum voltage, then execute the adaptive temperature increase step, otherwise continue to determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage;

[0012] The adaptive temperature rise step is used to update the target temperature by heating, and after cooling to the target temperature, the APD bias voltage is increased, and then the specified maximum voltage monitoring step is performed;

[0013] The specified maximum voltage monitoring step is used to determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage. If so, the adaptive temperature rise step is executed, otherwise, the specified minimum voltage monitoring step is executed;

[0014] The specified minimum voltage monitoring step is used to determine whether the operating voltage of the TEC at the target temperature is lower than the specified minimum voltage, and if so, the adaptive temperature reduction step is performed;

[0015] The adaptive cooling step is used to update the target temperature by cooling, and cool to the target temperature after reducing the APD bias voltage, and then perform the cooling temperature monitoring step;

[0016] The cooling temperature monitoring step is used to determine whether the TEC is cooled to the target temperature within a specified time. If not, the adaptive temperature increase step is executed.

[0017] Furthermore, the initialization step also configures initial values ​​for the flags; and,

[0018] When it is determined in the specified minimum voltage monitoring step that the operating voltage of the TEC at the target temperature is not lower than the specified minimum voltage, it is determined whether the flag is an initial value, if so, a concession operating voltage monitoring step is executed, otherwise, a specified maximum voltage monitoring step is executed;

[0019] The concession operating voltage monitoring step is used to determine whether the operating voltage of the TEC at the target temperature is lower than the concession operating voltage. If the operating voltage of the TEC at the target temperature is not lower than the concession operating voltage, the specified maximum voltage monitoring step is executed. Otherwise, the flag is configured to other values, and the adaptive cooling step is executed. When the TEC is cooled to the target temperature within the specified time, the flag is restored to the initial value.

[0020] The concession operating voltage is the sum of the specified minimum voltage and the preset voltage margin value.

[0021] Furthermore, the single-photon detector refrigeration control method of the present invention further includes a step of determining whether the target temperature is equal to the initial target temperature when the TEC is cooled to the target temperature within a specified time in the refrigeration temperature monitoring step, wherein:

[0022] If yes, then determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage, and perform the adaptive temperature increase step when the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage, otherwise continue to determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage;

[0023] If not, the specified maximum voltage monitoring step is executed.

[0024] Furthermore, the single-photon detector cooling control method of the present invention also includes the step of providing an abnormal prompt when the target temperature is different from the initial target temperature.

[0025] Further, the operating voltage of the TEC at the target temperature is determined when the temperature stably reaches the target temperature.

[0026] Furthermore, the coefficient factor a between the APD avalanche breakdown voltage and the temperature is used to calculate the adjustment amount of the APD bias voltage according to the adjustment amount of the target temperature, so as to keep the difference between the APD bias voltage and the avalanche breakdown voltage unchanged.

[0027] A second aspect of the present invention relates to a single-photon detector refrigeration control system that is adaptive to temperature and TEC performance changes, comprising a temperature sensing module, a control module and a TEC;

[0028] The TEC is set to cool the APD;

[0029] The temperature sensing module is configured to obtain the real-time cooling temperature of the TEC and upload it to the control module;

[0030] The control module is configured to control a target temperature for the TEC and an APD bias voltage acting on the APD according to the above-mentioned single photon detector cooling control method.

[0031] Further, the temperature sensing module includes a TEC temperature acquisition unit and an ADC unit;

[0032] The TEC temperature acquisition unit is configured to acquire the real-time cooling temperature of the TEC and output a simulated temperature value;

[0033] The ADC unit is configured to convert the analog temperature value into a temperature acquisition digital signal and upload it to the control module.

[0034] Further, the control module includes a storage unit, a control unit, a DAC unit, an APD bias unit and a DC / DC power supply;

[0035] The storage unit stores an initial target temperature and an initial APD bias voltage;

[0036] The control unit is configured to determine the target temperature and the APD bias voltage according to the above-mentioned single-photon detector cooling control method, and generate a TEC working voltage digital control signal according to the target temperature and the real-time cooling temperature of the TEC, and generate an APD bias digital control signal according to the APD bias voltage;

[0037] The DAC unit is configured to convert the TEC working voltage digital control signal into the TEC working voltage analog control signal, and convert the APD bias voltage digital control signal into the APD bias analog control signal;

[0038] The DC / DC power supply is configured to simulate a control signal according to the TEC operating voltage to provide an operating voltage for the TEC;

[0039] The APD bias unit is configured to provide a bias voltage to the APD according to an APD bias analog control signal.

[0040] Furthermore, the storage unit also stores PID parameters; and the control unit is further configured to generate a TEC operating voltage digital control signal based on the target temperature and the real-time cooling temperature of the TEC using a PID algorithm.

[0041] Furthermore, the maximum output voltage of the DC / DC power supply is configured as an upper limit value of the operating voltage of the TEC by means of a resistor network; and / or the TEC operating voltage digital control signal is in the form of a DAC code value. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. It is obvious that the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 The TEC cooling control scheme for single photon detectors in the prior art is schematically shown;

[0045] Figure 2 An example of a single-photon detector refrigeration control system with adaptive temperature and TEC performance changes according to the present invention is shown;

[0046] Figure 3 An example of a single-photon detector cooling control method according to the present invention that is adaptive to temperature and TEC performance changes is shown;

[0047] Figure 4 The flowchart of processing abnormal temperature signal in the single-photon detector cooling control method with adaptive temperature and TEC performance change according to the present invention is shown. DETAILED DESCRIPTION

[0048] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following embodiments are provided by way of example so as to fully convey the spirit of the present invention to those skilled in the art to which the present invention belongs. Therefore, the present invention is not limited to the embodiments disclosed herein.

[0049] Figure 2 An example of a single-photon detector refrigeration control system that adapts to temperature and TEC performance changes according to the present invention is shown.

[0050] The single-photon detector refrigeration control system capable of self-adapting to temperature and TEC performance changes of the present invention may include a TEC, a temperature sensing module and a control module.

[0051] Those skilled in the art know that in a single-photon detector, APD is the core optoelectronic device, which works in a Geiger mode with a reverse bias voltage higher than the avalanche breakdown voltage, and usually requires TEC to provide cooling to suppress dark counts. Among them, TEC can be a semiconductor cooler made by using the Peltier effect of semiconductor materials.

[0052] In order to realize cooling control, it is necessary to use the temperature sensor module to obtain the real-time cooling temperature of TEC and upload it to the control module to implement the corresponding cooling control.

[0053] like Figure 2As shown, the temperature sensing module may include a TEC temperature acquisition unit and an ADC unit, wherein the TEC temperature acquisition unit acquires the real-time cooling temperature of the TEC and outputs an analog temperature value, and the ADC unit converts the analog temperature value into a temperature acquisition digital signal and uploads it to the control module.

[0054] As an example, the TEC temperature acquisition unit can acquire the real-time temperature at the APD, that is, the real-time cooling temperature of the TEC, by means of a thermistor in a resistance voltage division manner.

[0055] As an example, the ADC unit may be implemented by means of an ADC chip.

[0056] In the present invention, in addition to controlling the target (cooling) temperature on the TEC and controlling the application of the corresponding working bias to the APD, the control module can also adaptively adjust the target temperature of the TEC and the APD bias according to the changes in the ambient temperature and the degradation of the TEC performance, so that the TEC will not work at full load for a long time, and at the same time keep the performance of the single-photon detector stable when the ambient temperature changes (too high) or the TEC performance deteriorates.

[0057] like Figure 2 As shown, the control module may include a storage unit, a control unit, a DAC unit, an APD bias unit, and a DC / DC power supply. The storage unit and the control unit may be implemented in the form of a memory and a controller, respectively, and the DAC unit, the APD bias unit, and the DC / DC power supply may be implemented in the form of a chip.

[0058] In the present invention, for example, the factory-configured APD cooling temperature and APD working bias voltage can be obtained and stored in the storage unit as the initial target temperature and initial APD bias voltage of the TEC. In addition, when it is desired to use the PID algorithm to complete the control process of achieving the target temperature on the TEC, the corresponding PID parameters can also be pre-stored in the storage unit.

[0059] Therefore, when the device is powered on, the control unit can read the initial target temperature and the initial APD bias from the storage unit as the current (real-time) target temperature and APD bias, and read the PID parameters for the subsequent PID control process.

[0060] When the control unit obtains the current target temperature and learns the real-time cooling temperature of the TEC based on the temperature acquisition digital signal reported by the ADC unit, the corresponding PID algorithm can be used to generate a digital control signal for the TEC operating voltage based on the current target temperature and the real-time cooling temperature, and the signal is sent to the DAC unit. The DAC unit can control the DC / DC power supply to output the corresponding operating voltage to the TEC based on the received digital control signal for the TEC operating voltage, and finally make the real-time cooling temperature of the TEC stably reach the target temperature, thereby realizing the control process of the current target temperature.

[0061] As an example, the TEC operating voltage digital control signal output by the control unit can be in the form of a DAC code value (code value), wherein different DAC code values ​​correspond to different TEC operating voltages. Therefore, when the real-time cooling temperature of the TEC stably reaches the target temperature, the TEC operating voltage adjusted by the PID algorithm in the control unit is also a corresponding stable value, that is, the DAC code value output by the control unit is also a stable value (or fluctuates within a very small range). Therefore, the control unit can calculate the current TEC operating voltage according to the DAC code value at this time, thereby determining the current TEC cooling power (working state).

[0062] For example, the DAC code value range is 0-65535, and the smaller the code value, the higher the TEC working voltage that the DC / DC power supply should output to the TEC. Under normal circumstances where the factory-calibrated configuration parameters are used and the cooling temperature and TEC working state are stable, the DAC code value corresponding to the target temperature (i.e., the initial target temperature) should be 20000. As the TEC is used for a longer time, its performance may deteriorate. Therefore, when other conditions remain unchanged, the corresponding DAC code value will decrease (for example, to 10000) when the TEC is stably cooled to the same target temperature, which means that the TEC needs to work at a higher working voltage; or, as the working environment temperature increases, the cooling temperature difference of the TEC increases, and it needs to increase the cooling power to stably cool to the same target temperature. At this time, the corresponding DAC code value will also decrease (for example, to 10000) when the TEC is stably cooled to the same target temperature, which also means that the TEC needs to work at a higher working voltage. Therefore, in the present invention, the DAC code value can be conveniently used to monitor the ambient temperature change and TEC performance degradation. For example, when the DAC code value is lower than a certain set value, it can be judged that an abnormality has occurred, and the abnormal state can be reported to the host computer as needed or the abnormality can be prompted by the hardware indicator light.

[0063] As mentioned above, the control unit of the present invention also needs to adaptively adjust the target temperature and APD bias of TEC according to changes in ambient temperature and degradation of TEC performance, so that TEC will not operate at full load for a long time, while maintaining the stability of the single-photon detector performance when the ambient temperature changes (too high) or the TEC performance deteriorates.

[0064] To this end, an upper limit value of the TEC's operating voltage can be pre-set to prevent it from being in a full-load state for a long time. Therefore, the control unit can adjust the target temperature of the TEC adaptively according to the change of ambient temperature and the degradation of TEC performance by increasing the target temperature when the TEC fails to cool to the target temperature within a specified time or the operating voltage at the target temperature is higher than the upper limit value of the operating voltage, and by reducing the target temperature when the operating voltage of the TEC at the target temperature is lower than the specified minimum voltage.

[0065] As an example, the maximum output voltage of the DC / DC power supply for providing the operating voltage to the TEC can be limited to the upper limit of the operating voltage in the form of hardware by means of a resistor network. The upper limit of the operating voltage of the TEC can preferably be set to 70% of its rated operating voltage.

[0066] Furthermore, in order to ensure the stable performance of the single-photon detector at the same time, the control unit can also calculate the APD bias corresponding to the adjusted target temperature based on the linear relationship between the APD avalanche breakdown voltage and temperature while adjusting the target temperature, so as to, for example, keep the difference between the bias voltage acting on the APD and the current avalanche breakdown voltage unchanged.

[0067] Assume that the control unit is set to step value T level Adjust the target temperature, T target_1 is the current target temperature, T real is the real-time cooling temperature of TEC, v bias_1 is the APD bias voltage corresponding to the current target temperature, and a is the avalanche breakdown voltage-temperature coefficient factor.

[0068] When the control unit determines that the current target temperature needs to be increased, it can calculate the adjusted target temperature. in, The value is rounded down.

[0069] Subsequently, the control unit will also calculate the adjusted target temperature T target_change The corresponding APD bias voltage V bias_change =V bias_1 +a*ΔT target , where ΔT target =T target_change -T target_1 .

[0070] Therefore, the control unit can use the PID algorithm to control the TEC to stably achieve the target temperature T target_change , and to achieve the target temperature T target_change Then the APD bias unit is controlled to apply an APD bias voltage V to the APD. bias_change .

[0071] Similarly, when the control unit determines that the current target temperature needs to be lowered, the adjusted target temperature T target_change =T target_1 -T level .

[0072] Subsequently, the control unit will also calculate and adjust the target temperature T accordingly. target_change The corresponding APD bias voltage V bias_change =V bias_1 -a*T level .

[0073] At this time, unlike the heating process, the control unit will first control the APD bias unit to apply the APD bias voltage V on the APD. bias_change , and then use the PID algorithm to control the TEC to stably achieve the target temperature T target_change , thereby providing necessary protection for the APD device while adaptively cooling down.

[0074] In order to better understand the working principle of the present invention (especially the control unit), the following will be combined with Figure 3-4 , a single-photon detector cooling control method that is adaptive to temperature and TEC performance changes of the present invention is described in detail.

[0075] like Figure 3 As shown, the single-photon detector cooling control method of the present invention may include an initialization step, an adaptive temperature increase step, a specified maximum voltage monitoring step, a specified minimum voltage monitoring step, an adaptive temperature reduction step and a cooling temperature monitoring step.

[0076] In an initialization step (which is initiated, for example, at power-on), the control unit may read an initial target temperature T from the storage unit. target and the initial APD bias V bias , and configure these initial values ​​as the current target temperature and APD bias voltage. In addition, the initial value of the flag P can also be configured (eg, P=0).

[0077] Therefore, the control unit can use the PID algorithm to control the TEC to reach the target temperature and determine whether the TEC is cooled to the target temperature within a specified time.

[0078] If the target temperature is reached within the specified time, it can be further determined whether the operating voltage of the TEC when the target temperature is stably reached is higher than the specified maximum voltage. The specified maximum voltage can be set to be slightly lower than the upper limit of the TEC operating voltage, which will help to achieve the required cooling state more stably.

[0079] If the target temperature is not cooled to within the specified time or the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage, the target temperature can be increased with the help of an adaptive temperature increase step to relieve the cooling pressure of the TEC and keep the single-photon detector working stably.

[0080] If the temperature is cooled to the target temperature within the specified time and the operating voltage of the TEC at the target temperature is not higher than the specified maximum voltage, the current operating state of the TEC can be maintained, and the operating voltage of the TEC at the target temperature is cyclically determined to be higher than the specified maximum voltage, so as to continuously monitor the ambient temperature changes and / or the occurrence of TEC performance degradation.

[0081] In the adaptive temperature increase step, the control unit can, for example, adjust the temperature according to the step value T level The target temperature is increased to update it and the corresponding APD bias is calculated, for example, to obtain the above-mentioned and V bias_change =V bias_1 +a*ΔT target ; and after controlling the TEC to cool to the updated target temperature (eg, using a PID algorithm), controlling the APD bias unit to apply a corresponding APD bias to the APD. Subsequently, the control unit will begin to execute the specified maximum voltage monitoring step.

[0082] In the specified maximum voltage monitoring step, the control unit can determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage. If so, the adaptive temperature increase step is executed to further increase the target temperature. Otherwise, the specified minimum voltage monitoring step can be executed.

[0083] In the specified minimum voltage monitoring step, the control unit can determine whether the operating voltage of the TEC at the target temperature is lower than the specified minimum voltage, and if so, perform an adaptive temperature reduction step to reduce the target temperature.

[0084] In the adaptive cooling step, the control unit can also, for example, adjust the temperature according to the step value T level The target temperature is lowered to update it and the corresponding APD bias is calculated, for example, to obtain the T target_change =T target_1 -T level and V bias_change =V bias_1 -a*T levelDifferent from the heating process, after calculating the lowered target temperature and its corresponding APD bias, the control unit will first control the APD bias unit to apply an updated APD bias to the APD, and then (for example, using a PID algorithm) control the TEC to cool to the updated target temperature, thereby providing protection for the APD device during the cooling process and avoiding the risk of the APD being broken down due to excessive overvoltage.

[0085] If, in the specified minimum voltage monitoring step, it is determined that the operating voltage of the TEC at the target temperature is not lower than the specified minimum voltage, the control unit can determine whether the flag P is an initial value (for example, this can be achieved by determining whether P is a value other than the initial value 0, 1). If the flag P is another value (for example, P=1), the specified maximum voltage monitoring step is executed.

[0086] If the flag P is an initial value (P=0), the concession operating voltage monitoring step is started to determine whether the operating voltage of the TEC at the target temperature is lower than the concession operating voltage.

[0087] If the operating voltage of TEC at the target temperature is not lower than the concession operating voltage, the specified maximum voltage monitoring step is executed, otherwise the flag P is configured to other values ​​(P=1), and the adaptive cooling step is executed, and when the TEC is cooled to the target temperature (calculated by the adaptive cooling step) within the specified time, the flag P is restored to the initial value (P=0).

[0088] In the present invention, since the specified minimum voltage is set so that any TEC with a working voltage lower than the specified minimum voltage is allowed to further reduce its target temperature, and TEC devices inevitably have individual differences, some TEC devices may allow the target temperature to be further reduced even when their working voltage is not lower than the specified minimum voltage. Therefore, the present invention proposes to add a certain redundant voltage on the basis of the specified minimum voltage to form a concession working voltage as the final temperature reduction judgment voltage value. Thus, with the help of the concession working voltage monitoring step, a temperature reduction attempt is made when the TEC working voltage is lower than the concession working voltage but not lower than the specified minimum voltage. If the temperature reduction is successful, the flag P is restored to the initial value (P=0), and the same operation is performed the next time the same situation occurs; if the temperature reduction fails, the flag P is maintained at another value (P=1), and the judgment is skipped the next time the same situation occurs, so that the method system of the present invention can identify the differences between different batches of TEC devices with minimal computing resources, so that the cooling performance of the TEC device is maximized within a reasonable range.

[0089] After completing the target temperature lowering operation with the help of the adaptive cooling step, the control unit can execute the cooling temperature monitoring step to determine whether the cooling reaches the target temperature within the specified time, and restore the flag P to the initial value (P=0) when the TEC cools to the target temperature within the specified time, otherwise perform the heating operation with the help of the adaptive heating step.

[0090] Continue to see Figure 3 After completing the cooling operation with the help of the adaptive cooling step, the control unit may further execute a step of determining whether the target temperature is equal to the initial target temperature.

[0091] If the target temperature is determined to be equal to the initial target temperature, the control unit will continue to determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage, and execute the adaptive temperature increase step when the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage, otherwise it will continue to determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage.

[0092] If it is determined that the target temperature is not equal to the initial target temperature, the specified maximum voltage monitoring step is executed and the temperature reduction determination step is continued.

[0093] In this way, the control unit can adaptively adjust (cool) the target temperature and APD bias voltage when the ambient temperature changes and the TEC performance deteriorates by continuously executing the above control process during operation, so as to keep the detector working state stable.

[0094] like Figure 4 As shown, the control unit can also raise the temperature abnormality signal Error when detecting that the target temperature is different from the (initial) target temperature stored in the storage unit, prompting the user to maintain an ambient temperature suitable for the device to work or check the working status of the TEC device and issue an abnormal prompt.

[0095] Furthermore, it is easy for those skilled in the art to understand that when obtaining the TEC operating voltage, it is necessary to first determine whether the TEC operating voltage has stabilized within a certain period of time (because when the PID parameters are not set properly, the TEC operating voltage may continue to oscillate for a long time) to avoid sampling the unstable operating voltage for judgment, thereby ensuring the accurate implementation of the refrigeration control method.

[0096] In summary, in the single-photon detector TEC refrigeration control method and system that is adaptive to ambient temperature changes and TEC performance degradation proposed in the present invention, by limiting the maximum operating voltage of TEC (for example, configuring the maximum output voltage of the TEC power supply to 70% of the rated operating voltage of TEC through a resistor network in hardware), the TEC operating voltage and the refrigeration temperature are monitored in real time, and the target temperature of TEC and the operating bias of APD are automatically adjusted according to the monitoring results (for example, when the ambient temperature is too high or the TEC performance is degraded, the TEC refrigeration target temperature is increased and the APD operating bias is adjusted), to ensure that the operating overvoltage of APD (that is, the difference between the APD bias and the avalanche breakdown voltage) remains unchanged when the refrigeration temperature changes, so that the single-photon detector maintains a stable detection efficiency, only partially sacrificing the dark count performance of the detector, and at the same time optimizing the post-pulse index to ensure that the single-photon detector can still operate stably when the working environment temperature is too high or the TEC performance is degraded. When the ambient temperature returns to the normal temperature range, the (cooling) target temperature of the TEC can be automatically restored to the original cooling target temperature (i.e., the initial target temperature) stored in the memory (e.g., Flash), and the working bias voltage of the APD can be adjusted synchronously, so that the performance indicators such as the detection efficiency, dark count rate, and after-pulse probability of the single-photon detector can be synchronously restored to normal. In this way, the TEC device can be protected, the service life of the TEC device and the single-photon detector equipment can be increased, and the environmental adaptability of the single-photon detector can be improved, so that the single-photon detector can maintain stable operation by sacrificing only some dark count indicators under extreme conditions where the ambient temperature is too high or the TEC performance is degraded.

[0097] Although the present invention has been described above through specific embodiments in conjunction with the accompanying drawings, those skilled in the art will readily recognize that the above embodiments are merely exemplary and are used to illustrate the principles of the present invention, and do not limit the scope of the present invention. Those skilled in the art may make various combinations, modifications and equivalent substitutions to the above embodiments without departing from the spirit and scope of the present invention.

Claims

1. A single-photon detector cooling control method that is adaptive to temperature and TEC performance changes, which pre-sets an upper limit value of the operating voltage for the TEC and a specified minimum voltage; and When the TEC is not cooled to the target temperature within a specified time or the operating voltage at the target temperature is higher than the upper limit of the operating voltage, increasing the target temperature and the APD bias voltage; and, When the TEC operating voltage at the target temperature is below the specified minimum voltage, the APD bias voltage and the target temperature are reduced.

2. The single photon detector cooling control method according to claim 1, wherein: The upper limit of the operating voltage is 70% of the rated operating voltage of the TEC.

3. The single-photon detector cooling control method according to claim 1, comprising an initialization step, an adaptive temperature increase step, a specified maximum voltage monitoring step, a specified minimum voltage monitoring step, an adaptive temperature reduction step and a cooling temperature monitoring step; The initialization step is used to configure the target temperature and the APD bias voltage to the initial target temperature and the initial APD bias voltage at power-on; determine whether the TEC is cooled to the target temperature within a specified time, and determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage when the TEC is cooled to the target temperature within the specified time, wherein: The specified maximum voltage is set to be less than the upper limit of the operating voltage, and if the TEC is not cooled to the target temperature within the specified time or the operating voltage at the target temperature is higher than the specified maximum voltage, the adaptive temperature increase step is performed, otherwise it continues to be determined whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage; The adaptive temperature rise step is used to update the target temperature by heating, and after cooling to the target temperature, the APD bias voltage is increased, and then the specified maximum voltage monitoring step is performed; The specified maximum voltage monitoring step is used to determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage. If so, the adaptive temperature rise step is executed, otherwise, the specified minimum voltage monitoring step is executed; The specified minimum voltage monitoring step is used to determine whether the operating voltage of the TEC at the target temperature is lower than the specified minimum voltage, and if so, the adaptive temperature reduction step is performed; The adaptive cooling step is used to update the target temperature by cooling, and cool to the target temperature after reducing the APD bias voltage, and then perform the cooling temperature monitoring step; The cooling temperature monitoring step is used to determine whether the TEC is cooled to the target temperature within a specified time. If not, the adaptive temperature increase step is executed.

4. The single-photon detector cooling control method according to claim 3, wherein: The initialization step also configures initial values ​​for flags; and, When it is determined in the specified minimum voltage monitoring step that the operating voltage of the TEC at the target temperature is not lower than the specified minimum voltage, it is determined whether the flag is an initial value, if so, a concession operating voltage monitoring step is executed, otherwise, a specified maximum voltage monitoring step is executed; The concession operating voltage monitoring step is used to determine whether the operating voltage of the TEC at the target temperature is lower than the concession operating voltage. If the operating voltage of the TEC at the target temperature is not lower than the concession operating voltage, the specified maximum voltage monitoring step is executed. Otherwise, the flag is configured to other values, and the adaptive cooling step is executed. When the TEC is cooled to the target temperature within the specified time, the flag is restored to the initial value. The concession operating voltage is the sum of the specified minimum voltage and the preset voltage margin value.

5. The single-photon detector cooling control method according to claim 3 or 4, further comprising the step of determining whether the target temperature is equal to the initial target temperature when the TEC is cooled to the target temperature within a specified time in the cooling temperature monitoring step, wherein: If yes, then determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage, and perform the adaptive temperature increase step when the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage, otherwise continue to determine whether the operating voltage of the TEC at the target temperature is higher than the specified maximum voltage; If not, the specified maximum voltage monitoring step is executed.

6. The single-photon detector cooling control method as described in claim 1 further comprises the step of providing an abnormal prompt when the target temperature is different from the initial target temperature.

7. The single-photon detector cooling control method according to claim 1, wherein: The operating voltage of the TEC at the target temperature is determined when the temperature stabilizes to reach the target temperature.

8. The single photon detector cooling control method according to claim 1, wherein: The coefficient factor a between the APD avalanche breakdown voltage and the temperature is used to calculate the adjustment amount of the APD bias voltage according to the adjustment amount of the target temperature, so as to keep the difference between the APD bias voltage and the avalanche breakdown voltage unchanged.

9. A single-photon detector refrigeration control system that is adaptive to temperature and TEC performance changes, comprising a temperature sensing module, a control module and a TEC; The TEC is set to cool the APD; The temperature sensing module is configured to obtain the real-time cooling temperature of the TEC and upload it to the control module; The control module is configured to control a target temperature for the TEC and an APD bias voltage acting on the APD according to the single-photon detector cooling control method according to any one of claims 1 to 8.

10. The single photon detector cooling control system according to claim 9, wherein: The temperature sensing module includes a TEC temperature acquisition unit and an ADC unit; The TEC temperature acquisition unit is configured to acquire the real-time cooling temperature of the TEC and output a simulated temperature value; The ADC unit is configured to convert the analog temperature value into a temperature acquisition digital signal and upload it to the control module.

11. The single photon detector cooling control system according to claim 9, wherein: The control module includes a storage unit, a control unit, a DAC unit, an APD bias unit and a DC / DC power supply; The storage unit stores an initial target temperature and an initial APD bias voltage; The control unit is configured to determine the target temperature and the APD bias voltage according to the single-photon detector cooling control method according to any one of claims 1 to 8, and generate a TEC working voltage digital control signal according to the target temperature and the real-time cooling temperature of the TEC, and generate an APD bias digital control signal according to the APD bias voltage; The DAC unit is configured to convert the TEC working voltage digital control signal into the TEC working voltage analog control signal, and convert the APD bias voltage digital control signal into the APD bias analog control signal; The DC / DC power supply is configured to simulate a control signal according to the TEC operating voltage to provide an operating voltage for the TEC; The APD bias unit is configured to provide a bias voltage to the APD according to an APD bias analog control signal.

12. The single photon detector cooling control system according to claim 11, wherein: The storage unit also stores PID parameters; and, The control unit is also configured to generate a TEC operating voltage digital control signal according to the target temperature and the real-time cooling temperature of the TEC by using a PID algorithm.

13. The single photon detector cooling control system according to claim 11, wherein: By means of a resistor network, the maximum output voltage of the DC / DC power supply is configured to be the upper limit of the operating voltage for the TEC; and / or, The TEC operating voltage digital control signal is in the form of DAC code value.

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