Quenching circuit for photodetector, and detection circuit

Abstract

A quenching circuit (12) for a photodetector, and a detection circuit (M). The quenching circuit (12) can control the operating state of the photodetector (11), the photodetector (11) can perform photoelectric conversion, and the operating voltage of the photodetector (11) is higher than the avalanche breakdown voltage (VBD) of the photodetector (11); the quenching circuit (12) can quench the photodetector (11) after avalanche breakdown of the photodetector (11), and the quenching circuit (12) can also output a corresponding electrical signal, wherein the maximum voltage corresponding to the electrical signal is lower than the difference between the operating voltage and the avalanche breakdown voltage (VBD).

Description

Quenching circuit and detection circuit for photodetector

[0001] The present disclosure claims priority to Chinese patent application entitled “Quenching circuit and detection circuit of light detector” and application number 202311649692.8 filed on December 4, 2023, and Chinese patent application entitled “Detection circuit” and application number 202323293877.8 filed on December 4, 2023, and the contents of the priority applications are incorporated in their entirety into the present disclosure by reference. Technical Field

[0002] The embodiments of the present disclosure relate to the field of photoelectric conversion technology, and in particular to a quenching circuit and a detection circuit for a photodetector. Background Art

[0003] Detection circuits are an important component of laser detection. With the rapid development of semiconductor technology, it has become a trend to integrate light detectors and circuits into chips to make highly integrated, low-cost detection circuits. Among various light detectors, single-photon avalanche diodes (SPADs) have extremely high gain, thus having good weak signal detection capabilities and time resolution capabilities. SPADs are widely used in scenarios such as time-of-flight ranging and fluorescence lifetime imaging. SPADs are compatible with complementary metal oxide semiconductor (CMOS) processes. Therefore, SPADs can be integrated with CMOS readout circuit chips to achieve low-cost, high-performance SPAD sensors. The detection circuit may include a SPAD sensor array and a readout chip. The SPAD sensor can perform photoelectric conversion and output electrical signals. The readout chip can read the electrical signals, perform signal processing and storage.

[0004] The CMOS process places limitations on the operating voltage of the readout chip. The electrical signal output by the SPAD cannot exceed the operating voltage of the readout chip, otherwise the readout chip will not work effectively. The voltage of the electrical signal output by the SPAD is related to the reverse bias voltage applied to both ends of the SPAD. In this case, due to the operating voltage of the readout chip, the SPAD reverse bias voltage is also greatly limited. The performance of the SPAD is related to the magnitude of the applied reverse bias voltage. Generally speaking, the detection efficiency increases with the increase of the reverse bias voltage. If the SPAD operates in a low-voltage environment, the coverage of the depletion region in the SPAD is low. This will have a negative impact on the detection efficiency, timing jitter and other performance parameters of the SPAD. Therefore, how to reduce the limitations on the operating voltage of the optical detector and improve the performance of the optical detector has become an urgent problem to be solved. Summary of the Invention

[0005] In view of this, embodiments of the present disclosure provide a quenching circuit and a detection circuit for a light detector.

[0006] In a first aspect, embodiments of the present disclosure provide a quenching circuit for a photodetector, the quenching circuit being configured to control an operating state of the photodetector, the photodetector being configured to perform photoelectric conversion, the operating voltage of the photodetector being higher than an avalanche breakdown voltage of the photodetector;

[0007] The quenching circuit is configured to quench the photodetector after the photodetector avalanche breakdown, and the quenching circuit is further configured to output a corresponding electrical signal, wherein a maximum voltage corresponding to the electrical signal is lower than a difference between the operating voltage and the avalanche breakdown voltage.

[0008] Optionally, the maximum voltage corresponding to the electrical signal is proportional to an overvoltage, wherein the overvoltage is a difference between an operating voltage and an avalanche breakdown voltage.

[0009] Optionally, the quenching circuit includes a plurality of quenching resistors, and the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage is determined by the resistance values ​​of the plurality of quenching resistors.

[0010] Optionally, the quenching circuit includes: a first voltage-applying terminal configured to apply a first power supply voltage, the first voltage-applying terminal being arranged at an end away from the light detector; and

[0011] A second voltage-applying terminal is configured to apply a second supply voltage, and the second voltage-applying terminal is provided at an end of the photodetector away from the quenching circuit.

[0012] The difference between the first supply voltage and the second supply voltage is the operating voltage.

[0013] Optionally, the quenching circuit further includes:

[0014] The signal output end is configured to output the electrical signal, and the signal output end is arranged between the multiple quenching resistors.

[0015] Optionally, the plurality of quenching resistors include

[0016] a first quenching resistor and a second quenching resistor,

[0017] The first quenching resistor, the second quenching resistor and the photodetector are connected.

[0018] Optionally, the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage is determined by the resistance values ​​of the first quenching resistor and the second quenching resistor.

[0019] Optionally, the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage is: the ratio of the resistance of the first quenching resistor to the sum of the resistances of the first quenching resistor and the second quenching resistor.

[0020] Optionally, the first supply voltage is less than an overvoltage.

[0021] Optionally, the photodetector is a single photon avalanche diode.

[0022] In a second aspect, an embodiment of the present disclosure further provides a detection circuit, including:

[0023] a light detection chip, comprising a light detector configured to perform photoelectric conversion and output a corresponding electrical signal; and

[0024] a readout chip, comprising a readout circuit, wherein the readout circuit is configured to read out the electrical signal,

[0025] The operating voltage of the photodetector is higher than the avalanche breakdown voltage of the photodetector,

[0026] The maximum voltage corresponding to the electrical signal is lower than the difference between the operating voltage and the avalanche breakdown voltage.

[0027] Optionally, the maximum voltage corresponding to the electrical signal is proportional to an overvoltage, wherein the overvoltage is a difference between an operating voltage and an avalanche breakdown voltage.

[0028] Optionally, the detection circuit further includes

[0029] a quenching circuit configured to control the working state of the light detector and output the electrical signal,

[0030] The quenching circuit includes a plurality of quenching resistors, and the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage is determined by the resistance values ​​of the plurality of quenching resistors.

[0031] Optionally, the quenching circuit includes

[0032] A signal output terminal is configured to output the electrical signal, the signal output terminal is arranged between the multiple quenching resistors, and the signal output terminal is connected to the readout circuit.

[0033] Optionally, at least one quenching resistor is provided on the light detection chip.

[0034] Optionally, the multiple quenching resistors include a first quenching resistor and a second quenching resistor, the first quenching resistor, the second quenching resistor and the photodetector are connected, and the quenching circuit also includes a signal output end configured to output an electrical signal, and the signal output end is arranged between the first quenching resistor and the second quenching resistor.

[0035] Optionally, the second quenching resistor is provided on the light detection chip.

[0036] Optionally, the readout chip further includes a first voltage-applying terminal configured to apply a first power supply voltage, and the first voltage-applying terminal is connected to an end of the first quenching resistor away from the second quenching resistor.

[0037] Optionally, the light detection chip further includes a first voltage-applying terminal configured to apply a first power supply voltage, and the first voltage-applying terminal is connected to an end of the first quenching resistor away from the second quenching resistor.

[0038] Optionally, the light detection chip further includes a second voltage-applying terminal configured to apply a second supply voltage, the second voltage-applying terminal being connected to a terminal of the light detector away from the quenching circuit, wherein the difference between the first supply voltage and the second supply voltage is the operating voltage.

[0039] Using the quenching circuit of the embodiment of the present disclosure, the quenching circuit can control the operating state of the photodetector. The photodetector can be loaded with an operating voltage higher than its avalanche breakdown voltage. This allows the photodetector to undergo avalanche breakdown, thereby achieving high gain. The avalanche current of the photodetector can be output through the quenching circuit to obtain a corresponding electrical signal. The quenching circuit of the present disclosure can ensure that the maximum voltage corresponding to the electrical signal is lower than the difference between the operating voltage and the avalanche breakdown voltage. In this case, the quenching circuit of the present disclosure can reduce the operating voltage limitations of the photodetector and improve its performance.

[0040] By using the detection circuit of the embodiment of the present disclosure, the photodetector can be loaded with an operating voltage higher than the avalanche breakdown voltage of the photodetector. In this way, the photodetector can undergo avalanche breakdown, thereby obtaining high gain. After the photodetector avalanches, the photodetection chip can output a corresponding electrical signal to the readout circuit of the readout chip. The maximum voltage corresponding to the electrical signal is lower than the difference between the operating voltage of the photodetector and the avalanche breakdown voltage. In this case, the detection circuit of the present disclosure can increase the operating voltage of the photodetector, reduce the restrictions imposed by the readout circuit on the operating voltage of the photodetector, and improve the performance of the photodetector and the detection circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The following is a brief introduction to the drawings required for use in the embodiments of the present disclosure or in the description of the prior art. The drawings described below are merely some embodiments of this specification. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0042] FIG1 shows a schematic structural diagram of an exemplary detection circuit consistent with some embodiments of the present disclosure.

[0043] 2 to 4 respectively illustrate schematic diagrams of three exemplary quenching circuits consistent with some embodiments of the present disclosure.

[0044] FIG5 is a schematic diagram illustrating an exemplary operating state of a light detector consistent with some embodiments of the present disclosure. DETAILED DESCRIPTION

[0045] A single photon avalanche diode (SPAD) operates in Geiger mode. An operating voltage is applied to the SPAD. This operating voltage can be higher than the reverse bias of the avalanche breakdown voltage. When a photon is received, the SPAD can be triggered to avalanche. After the SPAD is triggered, the external circuit can reduce the voltage across the SPAD to quench it. The external circuit then restores the voltage across the SPAD to the operating voltage. The SPAD can wait for the next photon trigger. In practical applications, a photodetector and a quenching circuit can be used in conjunction. The quenching circuit can quench the avalanche of the photodetector. The quenching circuit can also output an avalanche current.

[0046] 1 , which shows a schematic structural diagram of an exemplary detection circuit consistent with some embodiments of the present disclosure.

[0047] In some embodiments, the detection circuit M includes a light detection chip M1 and a readout chip M2. The light detection chip M1 can convert light signals into electrical signals and output them. The readout chip M2 can read the electrical signals output by the light detection chip M1. The readout circuit M2 can also process and store the signals.

[0048] For example, the light detection chip M1 includes a light detector 11. The readout chip M2 includes a quenching circuit 12 and a readout circuit (not shown). The light detector 11 and the quenching circuit 12 can be connected in series.

[0049] In some embodiments, the quenching circuit 12 includes a signal output terminal S0. The signal output terminal S0 can be arranged between the light detector 11 and the quenching circuit 12. The signal output terminal S0 can output an electrical signal to the readout circuit. The quenching circuit 12 can also include a first voltage supply terminal S1 and a second voltage supply terminal S2. The first voltage supply terminal S1 can be arranged at an end away from the light detector 11. The first voltage supply terminal S1 can be used to apply a first supply voltage V S1 The second voltage-adding terminal S2 can be set at the end of the light detector 11 away from the quenching circuit 12. The second voltage-adding terminal S2 can be used to load the second power supply voltage V S2 .

[0050] For example, the readout circuit may include a complementary metal-oxide-semiconductor (CMOS) circuit. The photodetector may include a SPAD. The SPAD includes the following periodic working states: readiness, triggering, quenching, and recovery.

[0051] Both ends of the SPAD can be connected through V S1 and V S2 Load the working voltage. The working voltage can be the first supply voltage V S1 With the second supply voltage V S2 The voltage difference (V S1 -V S2 ). The operating voltage can be higher than the breakdown voltage. When the SPAD does not receive a photon, the SPAD is turned off. The SPAD is in a state of waiting for a photon to be detected. The circuit between the first voltage-applying terminal S1 and the second voltage-applying terminal S2 is open. The voltage V corresponding to the signal output terminal S0 is S0 Equal to the first supply voltage V of the first voltage terminal S1 S1 At this time, the voltage difference across the SPAD is the operating voltage.

[0052] When receiving a photon, the SPAD may be triggered to avalanche. The SPAD can undergo avalanche breakdown and output an avalanche current.

[0053] When the SPAD avalanches, the avalanche current flows through the quenching circuit. The voltage divider of the quenching circuit quickly reduces the voltage difference between the two ends of the SPAD to below the avalanche breakdown voltage. The avalanche is quenched. The voltage V S0 Reduced to the second supply voltage V S2 and avalanche breakdown voltage V BD The sum (V S2 +V BD ).

[0054] After the avalanche of the SPAD is quenched, the SPAD enters a recovery state. Under the influence of the voltage difference between the first voltage-applying terminal S1 and the second voltage-applying terminal S2, the bias voltage across the SPAD gradually increases to the operating voltage. After that, the SPAD enters the standby state again.

[0055] It can be seen that during the process of SPAD being triggered, quenched and recovered, the output voltage of the signal output terminal S0 is (V S2 +V BD )~V S1 The maximum output voltage is V S1 To ensure the normal operation of the COMS circuit, V S1 The operating voltage of the SPAD (V S1 -VS2 ) are also restricted.

[0056] CMOS technology with a process of 130nm or above can make the circuit's operating voltage higher. However, the CMOS process has high power consumption and high cost, and cannot meet the needs of high-density SPAD sensors. If a process below 65nm is used, the operating voltage of the CMOS circuit can be 3.3V or 5V. For example, V S2 =-V BD , then V S1 =V EX , where V EX The SPAD operating voltage is higher than the avalanche breakdown voltage V BD Therefore, the CMOS circuit requires the SPAD to work with V EX The V of SPAD operation cannot exceed 3.3V or 5V. EX Usually between 10 and 20V. EX A lower value will result in a smaller depletion region in the SPAD, which may negatively impact the detection efficiency, timing jitter, and other performance of the SPAD.

[0057] In order to solve the above technical problems, the embodiment of the present disclosure provides a quenching circuit for a light detector. The quenching circuit can control the working state of the light detector. The light detector can be loaded with an operating voltage higher than the avalanche breakdown voltage of the light detector. In this way, the light detector can undergo avalanche breakdown and obtain extremely high gain (10 6 The quenching circuit quenches the photodetector after avalanche breakdown and outputs a corresponding electrical signal. The maximum voltage corresponding to the electrical signal is lower than the difference between the operating voltage and the avalanche breakdown voltage.

[0058] For example, the operating voltage of the photodetector may be any one of the following: a voltage difference across the photodetector when the photodetector is in a test state; or a maximum voltage difference across the photodetector during the entire operating cycle of the photodetector.

[0059] By employing the technical solutions of the embodiments of the present disclosure, a photodetector can be loaded with an operating voltage higher than its avalanche breakdown voltage. This allows the photodetector to undergo avalanche breakdown, thereby achieving extremely high gain and sensitivity. After the photodetector undergoes avalanche breakdown, a quenching circuit can quench the photodetector and output an electrical signal. The maximum voltage of the output electrical signal is lower than the difference between the operating voltage and the avalanche breakdown voltage. In this case, the quenching circuit of the present disclosure can reduce the limitations of the readout circuit on the photodetector's operating voltage, thereby improving the performance of the photodetector.

[0060] In some embodiments, the maximum voltage corresponding to the electrical signal may be positively correlated with an overvoltage. For example, the overvoltage is the difference between the operating voltage and the avalanche breakdown voltage of the photodetector.

[0061] For example, when the maximum voltage corresponding to the electrical signal is positively correlated with the overvoltage, the maximum overvoltage of the photodetector can be determined based on the maximum voltage limit imposed by the photodetector's application scenario. For example, when the photodetector is connected to a CMOS readout circuit, the maximum voltage of the electrical signal should not exceed the operating voltage of the readout circuit. The range of the photodetector's overvoltage can be determined based on the positive correlation between the maximum voltage corresponding to the electrical signal and the overvoltage. This range, for example, includes the maximum value. In this case, the overvoltage of the photodetector can be adjusted within the range that does not exceed the maximum overvoltage limit. This allows for adjusting the performance of the photodetector and reducing any limitations on its operating voltage.

[0062] For example, the maximum voltage corresponding to the electrical signal may be proportional to the overvoltage.

[0063] In some embodiments, the maximum voltage of the electrical signal can be determined based on the maximum voltage limit imposed by the photodetector's application scenario. The maximum overvoltage range can be determined based on the maximum voltage of the electrical signal and the proportional relationship between the maximum voltage of the electrical signal and the overvoltage.

[0064] In some embodiments, the quenching circuit includes a plurality of quenching resistors, and the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage can be determined based on the resistance values ​​of the plurality of quenching resistors.

[0065] The application scenario of a photodetector may limit the maximum voltage corresponding to the electrical signal it outputs. To achieve the expected performance, the photodetector has a certain operating voltage and a corresponding overvoltage. The ratio of the operating voltage to the overvoltage can be determined based on the maximum voltage limit corresponding to the electrical signal and the overvoltage required by the photodetector. The resistance values ​​of multiple quenching resistors can be determined based on this ratio. The photodetector can operate under the required operating voltage and overvoltage conditions. The output electrical signal does not exceed the voltage limits imposed by the readout circuit, etc. This ensures both the performance of the photodetector and the operational safety of subsequent circuits.

[0066] In some embodiments, the quenching circuit includes a first voltage-applying terminal and a second voltage-applying terminal. The first voltage-applying terminal can be loaded with a first supply voltage. The first voltage-applying terminal can be located at an end of the photodetector away from the photodetector, and the second voltage-applying terminal can be loaded with a second supply voltage. The second voltage-applying terminal can be located at an end of the photodetector away from the quenching circuit. The difference between the first supply voltage and the second supply voltage can be the operating voltage of the photodetector. A reverse bias voltage can be applied to both ends of the photodetector via the first voltage-applying terminal and the second voltage-applying terminal. The reverse bias voltage can serve as the operating voltage of the photodetector. The operating voltage can exceed the avalanche breakdown voltage of the photodetector. The photodetector can operate in Geiger mode, achieving extremely high gain.

[0067] In some embodiments, the quenching circuit further includes a signal output terminal. The signal output terminal can output an electrical signal. The signal output terminal can be arranged between the plurality of quenching resistors.

[0068] When the photodetector is triggered to avalanche and avalanche breakdown occurs, the photodetector can be turned on. The signal output terminal can be set between multiple quenching resistors. Due to the voltage divider effect of the quenching resistors, the maximum voltage value of the output electrical signal is less than the voltage value applied to the first voltage-applying terminal.

[0069] In some embodiments, the first supply voltage loaded on the first voltage-applying terminal may be lower than the overvoltage of the photodetector, so that the maximum voltage corresponding to the electrical signal output by the photodetector is lower than the overvoltage of the photodetector.

[0070] The concepts, schemes, principles and advantages of the embodiments of the present disclosure are described in detail below with reference to the accompanying drawings and through specific application examples.

[0071] In some embodiments, the quenching circuit includes a first quenching resistor and a second quenching resistor, wherein the first quenching resistor, the second quenching resistor and the first terminal of the photodetector are connected.

[0072] 2 to 4 , which respectively illustrate schematic diagrams of three exemplary quenching circuits consistent with some embodiments of the present disclosure.

[0073] 2 to 4 , the quenching circuit 12 may include a first quenching resistor R1 and a second quenching resistor R2. The quenching circuit 12 may control the working state of the photodetector 11. The photodetector 11 includes a first terminal 11a and a second terminal 11b.

[0074] In some embodiments, the first quenching resistor R1 , the second quenching resistor R2 and the first end 11 a of the photodetector 11 are connected.

[0075] In a specific implementation, the type of the first quenching resistor can be determined based on specific circumstances.

[0076] For example, the first quenching resistor may include a single resistor.

[0077] For another example, the first quenching resistor may include a plurality of resistors, and the plurality of resistors may be connected in at least one of the following ways: in series or in parallel.

[0078] In a specific implementation, the type of the second quenching resistor can be determined based on specific circumstances.

[0079] For example, the second quenching resistor may include a single resistor.

[0080] For another example, the second quenching resistor may include multiple resistors, and the multiple resistors may be connected in at least one of the following ways: in series or in parallel.

[0081] It should be noted that in the embodiment of the present disclosure, there is no limitation on the types of the first quenching resistor and the second quenching resistor, as long as the first quenching resistor and the second quenching resistor can provide corresponding resistance values.

[0082] In a specific implementation, the type of the light detector can be determined based on specific circumstances.

[0083] For example, the photodetector may include at least one of the following: a SPAD, an avalanche photodiode (APD), or a silicon photomultiplier (SiPM).

[0084] It should be noted that the embodiment of the present disclosure does not limit the type of photodetector, as long as the photodetector has an avalanche breakdown voltage and can be triggered to avalanche by photons when the reverse bias voltage at both ends exceeds the avalanche breakdown voltage.

[0085] In some embodiments, referring to Figures 2 to 4, the quenching circuit 12 may include a first voltage-applying terminal S1 and a second voltage-applying terminal S2. The first voltage-applying terminal S1 may be provided at an end of the first quenching resistor R1 away from the second quenching resistor R2. The first voltage-applying terminal S1 may be used to apply a first supply voltage V S1 .

[0086] The second voltage supply terminal S2 can be provided at the second terminal 11b of the light detector 11. The second voltage supply terminal S2 can be used to apply a second power supply voltage V S2 The first supply voltage V S1 and the second supply voltage V S2 The difference between and can be the operating voltage.

[0087] For example, the difference between the first power supply voltage and the second power supply voltage may be the operating voltage. The operating voltage may be the difference between the first power supply voltage applied to the first voltage-applying terminal and the second power supply voltage applied to the second voltage-applying terminal.

[0088] In some embodiments, at least one of the first supply voltage or the second supply voltage is adjustable. Adjusting at least one of the first supply voltage or the second supply voltage can adjust the operating voltage of the photodetector, thereby adjusting the performance of the photodetector.

[0089] In some embodiments, the first supply voltage is adjustable.

[0090] It should be noted that the method for adjusting the operating voltage of the light detector in the embodiment of the present disclosure is not limited, as long as the difference between the first supply voltage and the second supply voltage can be adjusted. For example, the second supply voltage can also be adjusted. For another example, the first supply voltage and the second supply voltage can also be adjusted simultaneously.

[0091] 2 to 4 , the quenching circuit 12 may further include a signal output terminal S0 . The signal output terminal S0 is disposed between the first quenching resistor R1 and the second quenching resistor R2 .

[0092] For example, the signal output terminal is arranged between the first quenching resistor and the second quenching resistor. After the photodetector undergoes avalanche breakdown, the avalanche current can flow through the second quenching resistor and then be output.

[0093] In some embodiments, the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage of the photodetector may be determined based on the resistance values ​​of the first quenching resistor and the second quenching resistor.

[0094] Using the technical solutions of the disclosed embodiments, the resistance of at least one of the first quenching resistor and the second quenching resistor can be adjusted, thereby adjusting the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage. If the maximum voltage corresponding to the output electrical signal is determined, the maximum range or maximum value of the overvoltage can be adjusted. This allows the operating voltage of the photodetector to meet application requirements, thereby reducing the impact of the output electrical signal on the operating voltage of the photodetector and improving the performance of the photodetector.

[0095] In some embodiments, the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage may be the ratio of the resistance value of the first quenching resistor to the sum of the resistance values ​​of the first quenching resistor and the second quenching resistor.

[0096] The maximum range or maximum value of the overvoltage can be determined based on the application scenario's restrictions on the maximum voltage of the output electrical signal and the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage. The resistance of at least one of the first quenching resistor or the second quenching resistor can be adjusted, so that the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage can be adjusted. The maximum overvoltage is adjusted to meet the application requirements. For example, when the maximum voltage corresponding to the electrical signal limited by the application scenario is low, and the photodetector needs to operate at a higher overvoltage, the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage can be reduced by at least one of the following methods: reducing the resistance of the first quenching resistor or increasing the resistance of the second quenching resistor. When the maximum voltage corresponding to the electrical signal is determined, the overvoltage can take a wider range. The photodetector can operate at a higher operating voltage. The impact of the output electrical signal on the operating voltage of the photodetector can be further reduced. The performance of the photodetector can be adjusted, for example, to achieve higher detection efficiency.

[0097] Continuing with reference to Figures 2 to 4 and Figure 5, Figure 5 shows an exemplary operating state diagram of a photodetector consistent with some embodiments of the present disclosure. The abscissa of Figure 4 represents the reverse bias voltage across the photodetector, and the ordinate represents the current of the photodetector.

[0098] The first supply voltage V is applied through the first voltage terminal S1 S1 , the second supply voltage V is loaded through the second voltage-adding terminal S2 S2 , so that the working voltage of the photodetector 11 is (V S1 -V S2 ).

[0099] When the photodetector 11 does not receive a photon, the photodetector 11 is in a state of waiting for a photon to be detected. The photodetector 11 is cut off. The current I is 0. The reverse bias voltage V at both ends of the photodetector is the first power supply voltage V S1 With the second supply voltage V S2 The voltage difference, that is, the operating voltage (V S1 -V S2 ). The voltage at the signal output terminal S0 is V S1 .

[0100] When the photodetector 11 receives a photon, it triggers an avalanche. The photodetector 11 undergoes an avalanche breakdown. The photodetector instantly switches from cutoff to conduction. The current I of the photodetector 11 instantly increases from 0 to I MAX .

[0101] After the photodetector avalanches, current flows through the quenching circuit. Due to the voltage divider effect of the quenching resistor, the voltage difference V across the photodetector 11 quickly decreases to the avalanche breakdown voltage V BDThe avalanche in the photodetector 11 is quenched. The photodetector switches from on to off. The current I of the photodetector 11 changes from I MAX Reduced to 0.

[0102] During the process from avalanche triggering to quenching, the voltage V S0 From V S1 Reduce to (V S1 -(V S1 -V S2 -V BD )*k). Wherein, k=R1 / (R1+R2), that is, the ratio of the first quenching resistor R1 to the sum of the resistance values ​​of the first quenching resistor R1 and the second quenching resistor R2.

[0103] In summary, the overvoltage V EX is (V S1 -V S2 -V BD ). The voltage V corresponding to the electrical signal at the signal output terminal S0 S0 The value range is (V S1 -(V S1 -V S2 -V BD )*k~V S1 ).

[0104] In some embodiments, the first supply voltage V S1 Less than the overvoltage. The minimum voltage corresponding to the electrical signal at the signal output terminal S0 is 0. The voltage corresponding to the electrical signal output by the photodetector to the subsequent circuit is in the range of (0~V S1 ) range. The output voltage is not less than 0 and is less than the overvoltage. This ensures the normal operation of the subsequent circuits while keeping the overvoltage above the maximum voltage limit of the readout circuit, thus ensuring the performance of the photodetector.

[0105] The second pressurizing end S2 is loaded with negative pressure, for example, V S2 =-V BD -(1-k)V EX The first pressure terminal S1 is loaded with V S1 =k*V EX The operating voltage of the photodetector is V S1 -V S2 =V BD +V EX .

[0106] At this time, the voltage variation range of the signal output terminal S0 is (0~k*V Ex) range. Wherein, k=R1 / (R1+R2). The resistance values ​​of the first quenching resistor R1 and the second quenching resistor R2 are both greater than 0, so k is less than 1. The voltage V corresponding to the electrical signal at the signal output terminal S0 is S0 The maximum value is less than the overvoltage V EX .

[0107] The technical solution of the embodiment of the present disclosure is adopted to set multiple quenching resistors. A first supply voltage is applied to the end of the quenching circuit away from the light detector. The first supply voltage is less than the overvoltage. An electrical signal is drawn between the multiple quenching resistors so that the voltage V corresponding to the electrical signal at the signal output end is S0 The maximum value is less than the overvoltage V EX This can reduce the limitation of the output electrical signal on the operating voltage of the photodetector and improve the performance of the photodetector.

[0108] For example, the value of k can be based on the voltage V corresponding to the electrical signal. S0 The maximum value of the overvoltage V required for the photodetector to achieve the performance required by the application EX OK. Then you can set the resistance value of the quenching resistor.

[0109] In some embodiments, the overvoltage determined based on the maximum voltage limit at the signal output terminal and the k value can be higher than the maximum overvoltage required for practical photodetector applications. This allows the photodetector's operating voltage to be adjusted over a wide range. This further reduces the limitations imposed by the output electrical signal on the photodetector's operating voltage and increases the adjustable range of the photodetector's performance.

[0110] The present disclosure also provides a detection circuit. Referring to Figures 2 to 4 , the detection circuit M may include a light detection chip M1 and a readout chip M2.

[0111] The light detection chip may include a light detector 11. The light detector 11 may perform photoelectric conversion and output a corresponding electrical signal. The readout chip M2 may include a readout circuit (not shown in the figure). The readout chip M2 may read the electrical signal, process and store the signal. The operating voltage of the light detector 11 may be higher than the avalanche breakdown voltage of the light detector. The maximum voltage corresponding to the electrical signal may be lower than the difference between the operating voltage and the avalanche breakdown voltage.

[0112] In some embodiments, the maximum voltage corresponding to the electrical signal read out by the readout circuit may be lower than the difference between the operating voltage applied across the photodetector and the avalanche breakdown voltage of the photodetector.

[0113] By adopting the technical solution of the embodiment of the present disclosure, the light detector in the light detection chip can be loaded with an operating voltage higher than the avalanche breakdown voltage of the light detector. In this way, the light detector can undergo avalanche breakdown when receiving photons. The gain of the light detector can be improved. After the light detector undergoes avalanche breakdown, the light detection chip can output a corresponding electrical signal to the readout circuit of the readout chip. The maximum voltage corresponding to the electrical signal is lower than the difference between the operating voltage of the light detector and the avalanche breakdown voltage. In this case, the detection circuit disclosed in the present disclosure can increase the operating voltage of the light detector and reduce the limitation of the readout circuit on the operating voltage of the light detector. The performance of the light detector and the detection circuit can be improved.

[0114] In some embodiments, the readout chip may include CMOS circuitry. The readout chip including the CMOS circuitry can be 3D stacked with the photodetector chip. The photodetector can be stacked above the circuitry. The circuitry does not occupy the photosensitive area of ​​the photodetector. This ensures that the photodetector has sufficient photosensitive area at high pixel density while still being compatible with the use of low-power, high-performance CMOS circuitry.

[0115] In some embodiments, the readout circuit may be fabricated at a process no greater than 65 nm. CMOS process platforms with a process below 65 nm are more advanced, with lower power consumption and cost.

[0116] In some embodiments, the maximum voltage corresponding to the electrical signal may be positively correlated with an overvoltage, which is the difference between an operating voltage and an avalanche breakdown voltage of the photodetector.

[0117] When the maximum voltage corresponding to the electrical signal is positively correlated with the overvoltage, the maximum overvoltage of the photodetector can be determined based on the maximum voltage limit imposed by the photodetector's application scenario. For example, when the photodetector is connected to a CMOS readout circuit, the maximum voltage of the electrical signal should not exceed the operating voltage of the readout circuit. The range of the photodetector's overvoltage can be determined based on the positive correlation between the maximum voltage corresponding to the electrical signal and the overvoltage. This range, for example, includes the maximum value. In this case, the photodetector's overvoltage can be adjusted within a range that does not exceed the maximum overvoltage limit. This allows the performance of the photodetector to be adjusted, thereby reducing the limitations on the photodetector's operating voltage.

[0118] In some embodiments, the maximum voltage corresponding to the electrical signal may be proportional to the overvoltage.

[0119] In some embodiments, the maximum voltage of the electrical signal can be determined based on the maximum voltage limit imposed by the photodetector's application scenario. The maximum overvoltage range can be determined based on the maximum voltage of the electrical signal and the proportional relationship between the maximum voltage of the electrical signal and the overvoltage.

[0120] In some embodiments, the detection circuit M further includes a quenching circuit. The quenching circuit can control the working state of the light detector. For example, after the light detector is triggered to avalanche, the quenching circuit can quench the avalanche and output an avalanche signal.

[0121] In some embodiments, the quenching circuit includes a plurality of quenching resistors, and the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage can be determined based on the resistance values ​​of the plurality of quenching resistors.

[0122] The application scenario of a photodetector may limit the maximum voltage corresponding to the electrical signal it outputs. To achieve the expected performance, the photodetector has a certain operating voltage and a corresponding overvoltage. The ratio of the operating voltage to the overvoltage can be determined based on the maximum voltage limit corresponding to the electrical signal and the overvoltage required by the photodetector. Furthermore, the resistance values ​​of multiple quenching resistors can be determined based on this ratio. The photodetector can operate under the required operating voltage and overvoltage conditions. The output electrical signal does not exceed the voltage limits imposed by the readout circuit, etc. This ensures both the performance of the photodetector and the operational safety of subsequent circuits.

[0123] In some embodiments, the quenching circuit includes a first voltage-applying terminal and a second voltage-applying terminal. The first voltage-applying terminal can be loaded with a first supply voltage. The first voltage-applying terminal can be located at a terminal away from the photodetector. The second voltage-applying terminal can be loaded with a second supply voltage. The second voltage-applying terminal can be located at a terminal of the photodetector away from the quenching circuit. The difference between the first supply voltage and the second supply voltage can be the operating voltage of the photodetector. A reverse bias voltage can be applied to both ends of the photodetector via the first voltage-applying terminal and the second voltage-applying terminal. The reverse bias voltage can serve as the operating voltage of the photodetector. The operating voltage can exceed the avalanche breakdown voltage of the photodetector. The photodetector can operate in Geiger mode, achieving extremely high gain.

[0124] In some embodiments, the quenching circuit further includes a signal output terminal. The signal output terminal can output an electrical signal. The signal output terminal can be arranged between the plurality of quenching resistors.

[0125] When the photodetector is triggered to avalanche and avalanche breakdown occurs, the photodetector can be turned on. The signal output terminal can be set between multiple quenching resistors. Due to the voltage divider effect of the quenching resistors, the maximum value of the output electrical signal is less than the voltage value applied to the first voltage-applying terminal.

[0126] In some embodiments, the first supply voltage loaded on the first voltage-applying terminal is lower than the overvoltage of the photodetector, so that the maximum voltage corresponding to the electrical signal output by the photodetector is lower than the overvoltage of the photodetector.

[0127] In some embodiments, at least one quenching resistor is disposed on the light detection chip.

[0128] An operating voltage can be applied to both ends of the photodetector. The maximum voltage between the photodetector and the quenching circuit can be the difference between the operating voltage and the avalanche breakdown voltage, i.e., the overvoltage. At least one quenching resistor is provided in the photodetection chip. This ensures that voltage changes between the photodetector and the quenching circuit do not affect the readout chip. The signal output terminal can be provided between multiple quenching resistors. This ensures that the maximum voltage at the signal output terminal is less than the overvoltage. When the overvoltage of the photodetector exceeds the operating voltage threshold of the readout chip, the maximum voltage of the electrical signal output by the signal output terminal can still not exceed the operating voltage threshold of the readout chip, ensuring the normal operation of the readout chip.

[0129] In some embodiments, the quenching circuit includes a first quenching resistor and a second quenching resistor, wherein the first quenching resistor and the second quenching resistor are connected to the first terminal of the photodetector.

[0130] 2 to 4 , the detection circuit M may further include a quenching circuit 12. The quenching circuit 12 may control the working state of the light detector 11 and output the electrical signal.

[0131] In some embodiments, referring to Figures 2 to 4, the quenching circuit 12 may include a first quenching resistor R1, a second quenching resistor R2, and a signal output terminal S0. The photodetector 11 may include a first terminal 11a and a second terminal 11b. The first quenching resistor R1 and the second quenching resistor R2 are connected to the first terminal 11a of the photodetector 11. The signal output terminal S0 is disposed between the first quenching resistor R1 and the second quenching resistor R2. The signal output terminal S0 is connected to the readout circuit.

[0132] Exemplarily, after the photodetector converts the optical signal into an electrical signal, the quenching circuit outputs the corresponding electrical signal to a readout circuit of a readout chip via a signal output terminal. After voltage division processing by the quenching circuit, the electrical signal output by the signal output terminal to the readout circuit of the readout chip has a voltage different from that corresponding to the electrical signal at the first terminal of the photodetector.

[0133] In some embodiments, a ratio of a maximum voltage corresponding to the electrical signal to the overvoltage may be determined based on resistance values ​​of the first quenching resistor and the second quenching resistor.

[0134] The maximum range or maximum value of the overvoltage can be determined based on the application scenario's maximum voltage limit for the output electrical signal and the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage. By adjusting the resistance of at least one of the first quenching resistor or the second quenching resistor, the ratio of the maximum voltage to the overvoltage can be adjusted, thereby ensuring that the maximum overvoltage meets the application requirements.

[0135] In some embodiments, the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage may be the ratio of the resistance value of the first quenching resistor to the sum of the resistance values ​​of the first quenching resistor and the second quenching resistor.

[0136] For example, when the maximum voltage corresponding to the electrical signal is low due to the application scenario, and the photodetector needs to operate at a higher overvoltage, the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage can be reduced by at least one of the following methods: reducing the resistance of the first quenching resistor, or increasing the resistance of the second quenching resistor. When the maximum voltage corresponding to the electrical signal is determined, the overvoltage can take a wider range. The photodetector can operate at a higher operating voltage. The impact of the output electrical signal on the operating voltage of the photodetector can be further reduced. The performance of the photodetector can be adjusted, for example, to achieve higher detection efficiency.

[0137] In some embodiments, referring to Figures 2 to 4 , the detection circuit M further includes a first voltage-applying terminal S1 and a second voltage-applying terminal S2. The first voltage-applying terminal S1 is connected to an end of the first quenching resistor R1 that is distal from the second quenching resistor R2. A first supply voltage can be applied to the first voltage-applying terminal S1. The second voltage-applying terminal S2 is connected to the second end 11b of the photodetector 11. A second supply voltage can be applied to the second voltage-applying terminal S2. The difference between the first and second supply voltages can be the operating voltage.

[0138] It should be noted that the quenching circuit and the photodetector in the detection circuit described in the embodiment of the present disclosure may be the same as or similar to the quenching circuit and the photodetector in any of the aforementioned embodiments.

[0139] In some embodiments, the position of the first pressurizing end may be determined based on specific circumstances.

[0140] For example, referring to FIG. 4 , the first pressurizing end S1 may be provided on the light detecting chip M1 .

[0141] For another example, referring to Figures 2 and 3 , the first voltage-applying terminal S1 can be provided on the readout chip M2. In some embodiments, the readout chip includes a CMOS circuit. The readout chip can include a power supply circuit. The power supply circuit can apply a first supply voltage to the first voltage-applying terminal. The readout chip can also include a circuit for adjusting the supply voltage, making the first supply voltage adjustable. The magnitude of the first supply voltage can be adjusted based on actual application needs, thereby adjusting the operating voltage and output voltage of the photodetector.

[0142] In some embodiments, the readout chip may further include a gating circuit. When the photodetector needs to be gated, the gating circuit can apply a first supply voltage to the first voltage-applying terminal of the photodetector, placing the photodetector in Geiger mode. When the photodetector does not need to be gated, the gating circuit can disconnect the path for applying the first supply voltage to the first voltage-applying terminal, reducing the reverse bias voltage of the photodetector to below the avalanche breakdown voltage. This prevents the photodetector from being accidentally triggered by avalanches and generating interference signals.

[0143] In some embodiments, the position of the second pressurizing end may be determined based on specific circumstances.

[0144] For example, with reference to FIG. 2 to FIG. 4 , the second pressurizing end S2 may be provided on the light detecting chip M1 .

[0145] For another example, the second pressurizing end S2 may be provided on the readout chip M2.

[0146] For example, referring to FIG. 4 , the first pressurizing end S1 and the second pressurizing end S2 are provided on the light detecting chip M1 .

[0147] For another example, referring to FIG2 and FIG3 , the first pressurizing end S1 is provided on the readout chip M2 , and the second pressurizing end S2 is provided on the light detection chip M1 .

[0148] In some embodiments, the location of the first quenching resistor may be determined based on specific circumstances.

[0149] For example, referring to FIG. 3 and FIG. 4 , the first quenching resistor R1 may be provided on the light detection chip M1 .

[0150] For another example, referring to FIG. 2 , the first quenching resistor R1 may be provided in the readout chip M2 .

[0151] In some embodiments, the location of the second quenching resistor may be determined based on specific circumstances.

[0152] For example, with reference to FIG. 2 to FIG. 4 , the second quenching resistor R2 may be provided in the light detection chip M1 .

[0153] For another example, referring to FIG. 3 and FIG. 4 , the first quenching resistor R1 and the second quenching resistor R2 are provided in the light detection chip M1 .

[0154] Using the technical solutions of the disclosed embodiments, a first quenching resistor and a second quenching resistor can be provided in the light detection chip. The first and second quenching resistors can be manufactured using the same process. The first and second quenching resistors can have the same temperature coefficient of resistance variation with temperature. This allows the k value to remain stable over a wide temperature range, thereby stabilizing the voltage corresponding to the electrical signal output by the signal output terminal.

[0155] In some embodiments, referring to FIG2 , the first quenching resistor R1 is disposed in the readout chip M2 , and the second quenching resistor R2 is disposed in the light detection chip M1 .

[0156] It should be noted that the above describes multiple embodiment schemes provided by the embodiments of the present disclosure. The optional implementation methods and specific examples introduced in each embodiment scheme can be combined and cross-referenced with each other without conflict, thereby extending a variety of possible embodiment schemes, which can all be considered as embodiment schemes disclosed and disclosed by the present disclosure.

[0157] It should be noted that the “examples” or “embodiments” referred to in this specification refer to specific features, structures or characteristics that may be included in at least one implementation of the novel embodiments of the present disclosure. And in the description of this specification, terms such as “first” and “second” are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined by terms such as “first” and “second” may explicitly or implicitly include one or more of the features. Moreover, terms such as “first” and “second” are used to distinguish similar objects and are not necessarily used to describe a specific order or to express importance. It is understood that the terms used in this way can be interchangeable where appropriate so that the embodiments of the present disclosure described herein can be implemented in an order other than those illustrated or described herein.

[0158] Although the embodiments of the present disclosure are disclosed above, the present disclosure is not limited thereto. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be based on the scope defined by the claims.

Claims

1. A quenching circuit for a photodetector, the quenching circuit being configured to control the working state of the photodetector, the photodetector being configured to perform photoelectric conversion, the working voltage of the photodetector being higher than the avalanche breakdown voltage of the photodetector; The quenching circuit is configured to quench the photodetector after the photodetector avalanche breakdown, and the quenching circuit is also configured to output a corresponding electrical signal, wherein, The maximum voltage corresponding to the electrical signal is lower than the difference between the operating voltage and the avalanche breakdown voltage.

2. The quenching circuit according to claim 1, characterized in that: The maximum voltage corresponding to the electrical signal is proportional to the overvoltage, wherein the overvoltage is the difference between the operating voltage and the avalanche breakdown voltage.

3. The quenching circuit according to claim 2, characterized in that: It comprises a plurality of quenching resistors, and the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage is determined by the resistance values ​​of the plurality of quenching resistors.

4. The quenching circuit according to claim 3, characterized in that: include: A first voltage-applying terminal, configured to load a first supply voltage, the first voltage-applying terminal being disposed at an end of the quenching circuit away from the photodetector; and A second voltage-applying terminal is configured to load a second supply voltage, and the second voltage-applying terminal is arranged at an end of the photodetector away from the quenching circuit, The difference between the first power supply voltage and the second power supply voltage is the operating voltage.

5. The quenching circuit according to claim 3, characterized in that: Also includes: The signal output terminal is configured to output the electrical signal, and the signal output terminal is arranged between the multiple quenching resistors.

6. The quenching circuit according to claim 3, characterized in that: The plurality of quenching resistors include a first quenching resistor and a second quenching resistor, The first quenching resistor, the second quenching resistor and the photodetector are connected.

7. The quenching circuit according to claim 6, characterized in that: The ratio of the maximum voltage corresponding to the electrical signal to the overvoltage is determined by the resistance values ​​of the first quenching resistor and the second quenching resistor.

8. The quenching circuit according to claim 7, characterized in that: The ratio of the maximum voltage corresponding to the electrical signal to the overvoltage is: the ratio of the resistance value of the first quenching resistor to the sum of the resistance values ​​of the first quenching resistor and the second quenching resistor.

9. The quenching circuit according to claim 4, characterized in that: The first supply voltage is less than the overvoltage.

10. The quenching circuit according to claim 1, characterized in that: The photodetector is a single photon avalanche diode.

11. A detection circuit comprising: A light detection chip, comprising a light detector, wherein the light detector is configured to perform photoelectric conversion and output a corresponding electrical signal; and a readout chip, comprising a readout circuit, wherein the readout circuit is configured to read out the electrical signal, The operating voltage of the photodetector is higher than the avalanche breakdown voltage of the photodetector, The maximum voltage corresponding to the electrical signal is lower than the difference between the operating voltage and the avalanche breakdown voltage.

12. The detection circuit according to claim 11, characterized in that: The maximum voltage corresponding to the electrical signal is proportional to the overvoltage, wherein the overvoltage is the difference between the operating voltage and the avalanche breakdown voltage.

13. The detection circuit according to claim 12, characterized in that: Also includes a quenching circuit configured to control the working state of the photodetector and output the electrical signal, The quenching circuit includes a plurality of quenching resistors, and the ratio of the maximum voltage corresponding to the electrical signal to the overvoltage is determined by the resistance values ​​of the plurality of quenching resistors.

14. The detection circuit according to claim 13, characterized in that: The quenching circuit includes A signal output terminal is configured to output the electrical signal, the signal output terminal is arranged between the multiple quenching resistors, and the signal output terminal is connected to the readout circuit.

15. The detection circuit according to claim 13, characterized in that: At least one quenching resistor is disposed on the light detection chip.

16. The detection circuit according to claim 13, characterized in that: The plurality of quenching resistors include a first quenching resistor and a second quenching resistor, the first quenching resistor, the second quenching resistor and the photodetector are connected, The quenching circuit further includes a signal output terminal configured to output an electrical signal, wherein the signal output terminal is disposed between the first quenching resistor and the second quenching resistor.

17. The detection circuit according to claim 16, characterized in that: The second quenching resistor is arranged on the light detection chip.

18. The detection circuit according to claim 17, characterized in that: The readout chip further includes a first voltage-applying terminal configured to load a first supply voltage, and the first voltage-applying terminal is connected to an end of the first quenching resistor away from the second quenching resistor.

19. The detection circuit according to claim 17, characterized in that: The light detection chip further includes a first voltage-applying terminal configured to apply a first supply voltage, and the first voltage-applying terminal is connected to an end of the first quenching resistor away from the second quenching resistor.

20. The detection circuit according to claim 18 or 19, characterized in that: The light detection chip also includes a second voltage-applying terminal configured to load a second supply voltage, the second voltage-applying terminal being connected to an end of the light detector away from the quenching circuit, wherein the difference between the first supply voltage and the second supply voltage is the operating voltage.

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