Avalanche detection circuit and dual-mode APD detector

Abstract

The invention relates to an avalanche detection circuit and a dual-mode APD detector, and belongs to the technical field of photoelectric detection. A dual-mode APD detector is formed by an APD and an avalanche detection circuit, a current feedback control module and a voltage feedback control module are arranged in the avalanche detection circuit, the influence of noise current is eliminated by utilizing a current feedback control mechanism at an avalanche current input node, and the photoelectric detection performance of the APD detector is improved; meanwhile, the avalanche current of the APD detector in a Geiger mode is automatically quenched by utilizing a voltage feedback control mechanism, a quenching resistor is not needed, and noise introduction is avoided; the APD detector can be conveniently and quickly switched between a linear mode and a Geiger mode only by adjusting one variable resistor and one high-voltage power supply, and two sets of independent avalanche signal processing circuits do not need to be adopted, so that the application of the detector is more flexible, and the use convenience is improved.

Description

Technical Field

[0001] The present invention belongs to the field of photoelectric detection technology, relates to a photoelectric detection device, and in particular to an avalanche detection circuit and a dual-mode APD detector. Background Art

[0002] Avalanche photodiodes (APDs) utilize the ionization collision effect under high reverse bias to generate internal current gain, amplifying weak photogenerated current signals. They are widely used in fields such as LiDAR, medical imaging, and high-energy physics. APDs operate in two modes: linear and Geiger modes. When the reverse bias voltage is below the avalanche breakdown voltage, the APD linearly multiplies photogenerated carriers; this operating state is known as the linear mode. When the reverse bias voltage is above the avalanche breakdown voltage, the APD exponentially amplifies photogenerated carriers; this operating state is known as the Geiger mode.

[0003] Existing technical solutions can only allow the APD detector to work independently in linear or Geiger mode, and the front-end avalanche detection circuit is not compatible with the two working modes. Figure 1 This is an avalanche detection circuit commonly used in linear mode APDs in the prior art. The source of its PMOS1 tube serves as the circuit input node of the avalanche current. Under the action of the common-gate amplifier circuit and the feedback circuit, it has a very small equivalent input resistance, so it cannot perform avalanche quenching on the Geiger mode APD. At the same time, the large dark current or avalanche current of the Geiger mode APD will cause the drain voltage of the PMOS1 tube to increase, thereby entering the linear working area, causing the performance of the common-gate amplifier circuit to degrade. Figure 2 This is an avalanche detection circuit commonly used in Geiger-mode APDs in the prior art. To prevent high bias voltage or pulse voltage from damaging the back-end charge-sensitive amplifier (CSA), a sampling resistor with a smaller resistance is usually used and AC coupling is adopted. As a result, the avalanche current of the linear-mode APD will be shunted by the sampling resistor. In addition, the resistance of the quenching resistor is usually large, which will be a large noise source for the linear-mode APD.

[0004] Therefore, there is an urgent need for an avalanche detection circuit that is compatible with both linear and Geiger operating modes, so that the APD detector can switch the operating mode conveniently and quickly according to different application environments. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an avalanche detection circuit and a dual-mode APD detector, which avoids the use of sampling resistors by setting voltage feedback, and at the same time realizes avalanche quenching of the APD Geiger mode, and switches the APD working mode by setting an adjustable resistor. The avalanche detection circuit is combined with the APD to form a dual-working mode APD detector.

[0006] To achieve the above objectives, the present invention provides, on one hand, an avalanche detection circuit, comprising an input MOS transistor, a voltage feedback control module, a current feedback control module, a follower, and a charge-sensitive amplifier. The drain of the input MOS transistor receives a photocurrent; the output of the voltage feedback control module is connected to the gate of the input MOS transistor; the input of the current feedback control module is connected to the source of the input MOS transistor, thereby eliminating noise current flowing through the input MOS transistor and outputting the photocurrent transmitted by the input MOS transistor to the charge-sensitive amplifier; and the follower is disposed between the voltage feedback control module and the current feedback control module, with the input of the follower connected to the output of the current feedback control module, transferring the output voltage of the current feedback control module due to the photocurrent to the input of the voltage feedback control module, thereby enabling the voltage feedback control module to control the gate voltage of the input MOS transistor.

[0007] Furthermore, the current feedback control module includes a feedback-common-gate amplifier unit, a delay unit, and transistor NPN1. The input of the feedback-common-gate amplifier unit and the collector of transistor NPN1 are both connected to the source of the input MOS tube; the output of the feedback-common-gate amplifier unit is respectively connected to the input of the charge-sensitive amplifier and the follower; the input of the delay unit is connected to the output of the follower, and the output of the delay unit is connected to the base of transistor NPN1; the emitter of transistor NPN1 is grounded.

[0008] The feedback-common-gate amplifier unit includes an amplifier, a flow-through MOS transistor, and a resistor R1; the positive input terminal of the amplifier is connected to a reference voltage, the negative input terminal is connected to the source of the input MOS transistor, and the output terminal of the amplifier is connected to the gate of the flow-through MOS transistor; the source of the flow-through MOS transistor is connected to the source of the input MOS transistor, and the drain of the flow-through MOS transistor is respectively connected to the second terminal of the resistor R1, the input terminal of the follower, and the input terminal of the charge-sensitive amplifier; and the first terminal of the resistor R1 is connected to the power supply VDD.

[0009] The delay unit includes a resistor R2 and a capacitor C; the first end of the resistor R2 is connected to the output end of the follower, and the second end is connected to the base of the transistor NPN1 and the first end of the capacitor C respectively, and the second end of the capacitor C is grounded.

[0010] Furthermore, the voltage feedback control module includes a variable resistor R4, a resistor R3, and a transistor NPN2. The first end of the variable resistor R4 is connected to the power supply VDD, and the second end is connected to the gate of the input MOS transistor and the first end of the resistor R3. The collector of the transistor NPN2 is connected to the second end of the resistor R3, the base is connected to the output end of the follower, and the emitter is grounded.

[0011] On the other hand, the present invention provides a dual-mode APD detector, which includes the avalanche detection circuit described in the avalanche photodiode, the cathode end of the avalanche photodiode is connected to the high voltage power supply, and the anode end is connected to the drain of the input MOS tube in the avalanche detection circuit.

[0012] By adjusting the resistance of the variable resistor in the avalanche detection circuit and the voltage of the high-voltage power supply, the APD detector can be switched between linear mode and Geiger mode. The switching method is as follows:

[0013] Adjusting the resistance of the variable resistor to zero, and adjusting the voltage of the high-voltage power supply so that the voltage across the avalanche photodiode is lower than the avalanche breakdown voltage, and the APD detector switches to the linear mode;

[0014] Adjust the resistance of the variable resistor to R R4 At the same time, the voltage of the high-voltage power supply is adjusted so that the voltage across the avalanche photodiode is higher than the avalanche breakdown voltage, and the APD detector is switched to the Geiger mode.

[0015] Among them, the resistance R R4 It needs to meet the following conditions: when the pulse current output from the source of the input MOS tube reaches a preset threshold, the voltage difference between the gate and source of the input MOS tube is lower than the turn-on voltage of the input MOS tube.

[0016] The beneficial effects of the present invention are as follows: the present invention proposes a dual-mode APD detector consisting of an avalanche photodiode and an avalanche detection circuit, wherein a current feedback control module and a voltage feedback control module are provided in the avalanche detection circuit, and the influence of noise current (dark current or background current) is eliminated by using a current feedback control mechanism at the avalanche current input node (i.e., the connection point between the input MOS tube source, the current-passing MOS tube source and the transistor NPN1 collector), thereby improving the photoelectric detection performance of the APD detector, and the delay unit in the current feedback control module enables the pulse current transmitted by the input MOS tube to efficiently flow to the charge-sensitive amplifier, and be converted into a pulse voltage through the charge-sensitive amplifier without the need for a sampling resistor; at the same time, the voltage feedback control mechanism is used to automatically quench the avalanche current in the Geiger mode of the APD detector, without the need for a quenching resistor, thereby avoiding the introduction of noise.

[0017] In addition, through the design of the voltage feedback control module, the present invention can enable the APD detector to be conveniently and quickly switched between the linear mode and the Geiger mode by adjusting only a variable resistor and a high-voltage power supply, without the need to use two independent avalanche signal processing circuits, making the application of the detector more flexible and improving the convenience of use.

[0018] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0020] Figure 1 The present invention is an avalanche current detection circuit of a linear mode APD in the prior art.

[0021] Figure 2 The present invention is an avalanche current detection circuit of a Geiger mode APD in the prior art.

[0022] Figure 3 A schematic diagram of the avalanche detection circuit structure provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0023] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0024] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0025] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0026] The present invention provides an avalanche detection circuit and an APD detector with dual working modes. The avalanche detection circuit realizes compatibility of the two working modes of the APD detector, and the working mode can be quickly and conveniently switched according to different application environments. There is no need to use a quenching resistor for avalanche quenching, thus avoiding the introduction of noise.

[0027] An embodiment of the present invention provides an avalanche detection circuit to achieve the above effect, such as Figure 3 As shown, it includes two N-type MOS tubes NMOS1 and NMOS2, two N-type triodes NPN1 and NPN2, three resistors R1, R2 and R3, a variable resistor R4, an avalanche photodiode APD, a follower SF, a capacitor C, an amplifier AMP and a charge sensitive amplifier CSA.

[0028] The connections of the components in this circuit are as follows:

[0029] The cathode of the APD is connected to the high-voltage power supply HV, and the anode is connected to the drain of the MOS tube NMOS tube, and the light signal is sensed through the APD.

[0030] The gate of the MOS transistor NMOS2 is connected to the first end of the resistor R3, and the source is connected to the collector of the transistor NPN1; the base of the transistor NPN1 is connected to the first end of the resistor R2, and the emitter is grounded.

[0031] The base of the transistor NPN2 is connected to the second end of the resistor R2 , the emitter is connected to the ground potential, and the collector is connected to the second end of the resistor R3 .

[0032] The gate of MOS transistor NMOS1 is connected to the output of amplifier AMP, the source is connected to the collector of transistor NPN1, and the drain is connected to the input of charge-sensitive amplifier CSA. The output of CSA serves as the circuit output port VO. The positive input of amplifier AMP is connected to reference voltage VREF, and the negative input is connected to the source of MOS transistor NMOS1.

[0033] The second end of the resistor R1 is connected to the drain of the MOS transistor NMOS1 , and the first end of the resistor R1 is connected to the power supply VDD.

[0034] The input end of the follower SF is connected to the drain of the MOS transistor NMOS1, and the output end is connected to the base of the transistor NPN2.

[0035] The second end of the adjustable resistor R4 is connected to the gate of the MOS transistor NMOS2, the first end is connected to the power supply VDD, and the resistance adjustment end of R4 is connected to the control port CTRL.

[0036] A first end of the capacitor C is connected to the base of the transistor NPN1, and a second end of the capacitor C is connected to the ground potential.

[0037] Amplifier AMP, MOS transistor NMOS1, and resistor R1 form a feedback-common-gate amplifier unit, which receives the pulse current transmitted by MOS transistor NMOS2. Resistor R2 and capacitor C form a delay unit. Transistor NPN1 provides current feedback from the current input node. The feedback-common-gate amplifier unit, delay unit, and transistor NPN1 together form a current feedback control module. Transistor NPN2, resistor R3, and variable resistor R4 form a voltage feedback control module, which controls the gate voltage of MOS transistor NMOS2. Follower SF performs level shifting. MOS transistor NMOS2 transmits the pulse current generated by the APD and performs avalanche quenching of the APD. A charge-sensitive amplifier CSA converts the pulse current into a pulse voltage.

[0038] The dual-mode working principle of the APD detector based on the avalanche detection circuit is as follows:

[0039] like Figure 3 As shown, in the avalanche detection circuit, the anode of the APD is connected to the drain of the MOS transistor NMOS2 to form a node VN; the source of the MOS transistor NMOS2 is connected to the collector of the transistor NPN1 to form a node VM; the drain of the MOS transistor NMOS1 is connected to one end of the resistor R1 to form a node VX; the output end of the follower SF is connected to the base of the transistor NPN2 to form a node VY; the first end of the resistor R3 is connected to the second end of the variable resistor R4 to form a node VZ.

[0040] Among them, the equivalent input resistance at the node VM is equal to the input resistance of the feedback-common-gate amplifier circuit in parallel with the collector output resistance of the transistor NPN1. The feedback-common-gate amplifier unit composed of the amplifier AMP, the MOS transistor NMOS1 and the resistor R1 has an extremely low equivalent input resistance, usually a few ohms or less, while the output resistance of the collector of the transistor NPN1 can usually reach tens of kiloohms. Therefore, the equivalent input resistance at the node VM is very small, which is conducive to improving the current injection efficiency and allowing the current to flow efficiently to the charge-sensitive amplifier CSA.

[0041] When an injected current flows into the VM node, the voltage of the VX node inside the feedback-common-gate amplifier circuit increases. At this time, the follower SF shifts the level so that the voltage at the node VY can follow the voltage of the VX node, so the voltage at the node VY increases.

[0042] When the voltage at node VY rises, the voltage at node VY, after passing through the delay unit, controls the base voltage of transistor NPN1 to rise, increasing the collector current flowing through transistor NPN1 until it equals the current flowing into node VM. This causes the injected current at node VM to flow entirely into the collector of transistor NPN1 and no longer into the feedback-common-gate amplifier unit. This feedback control process is known as the current feedback control of the avalanche detection circuit. Furthermore, the voltage at node VY simultaneously controls the base voltage of transistor NPN2, causing the voltage at node VZ, the output of the voltage feedback control, to drop, thereby lowering the gate voltage of MOS transistor NMOS2. Because the feedback-common-gate amplifier unit maintains the voltage at node VM at reference voltage VREF, the gate-source voltage of MOS transistor NMOS2 decreases, increasing its on-resistance. Furthermore, when the gate-source voltage falls below the turn-on threshold voltage of MOS transistor NMOS2, NMOS2 is turned off. This feedback control process is known as the voltage feedback control of the avalanche detection circuit.

[0043] Based on the above working principle, when the APD detector needs to be in linear mode, the resistance of the variable resistor R4 is first adjusted to zero through the control port CTRL, so that the gate of the MOS tube NMOS2 is approximately short-circuited with the power supply VDD. At this time, the MOS tube NMOS2 is in a normally on state and the on-resistance is very small. The voltage at the node VN is approximately equal to the voltage at the node VM, that is, VREF. Then, by adjusting the high-voltage power supply HV, the voltage across the APD (HV-VREF) is made lower than the avalanche breakdown voltage. At this time, the APD detector is in linear mode.

[0044] When the APD detector does not detect pulsed light in the linear mode, DC currents such as dark current or background current will be offset by the collector current of the transistor NPN1 under the current feedback control of the avalanche detection circuit, and will not be injected into the charge-sensitive amplifier CSA; when the APD detector detects pulsed light and outputs pulsed current in the linear mode, since the pulse signal width is usually within tens of nanoseconds and there is a delay unit in the follower SF feedback branch, the collector current of the transistor NPN1 cannot respond in time to offset the pulse current. Therefore, the pulse current will be injected into the charge-sensitive amplifier CSA through the MOS tube NMOS1, converted into a pulse voltage and output to the back-end processing circuit.

[0045] When the APD detector needs to be in Geiger mode, the resistance of the variable resistor R4 is first adjusted to an appropriate value through the control port CTRL. At this time, the resistance of R4 is such that when the detected pulse current reaches a preset threshold (for example, 200 microamperes), the voltage difference between the output node VZ of the common-emitter amplifier circuit and the current input node VM can be lower than the turn-on threshold voltage of the MOS tube NMOS2. Then, the high-voltage power supply HV is adjusted so that the voltage across the APD (HV-VREF) is higher than the avalanche breakdown voltage. At this time, the APD detector is in Geiger mode.

[0046] Since the Geiger mode of the APD detector is usually used in a weak light environment, there is almost no background current and only dark current exists. At this time, the MOS tube NMOS2 is still in the normal on state, and the voltage drop across its source and drain is very small. Therefore, the voltage at the node VN is still approximately equal to the reference voltage VREF. When in Geiger mode, when the APD is not triggered to avalanche by photons, the dark current will be offset by the collector current of the transistor NPN1 under the current feedback control of the avalanche detection circuit, and will not be injected into the charge-sensitive amplifier CSA; when in Geiger mode, when the APD detects photons and induces avalanche multiplication, the avalanche pulse current rises exponentially. Under the voltage feedback control of the avalanche detection circuit, the gate voltage of the MOS tube NMOS2 drops. When the avalanche pulse current reaches the preset threshold, the MOS tube NMOS2 is turned off, and the voltage at the node VN rises rapidly, making the voltage across the APD detector lower than the avalanche breakdown voltage, thereby causing the APD detector to exit the Geiger mode. In the above process, due to the influence of the delay unit of the follower SF feedback branch, the collector current of the transistor NPN1 cannot respond in time, so the pulse current will be injected into the charge-sensitive amplifier CSA, converted into a pulse voltage and output to the back-end processing circuit.

[0047] When the APD detector leaves the Geiger mode and the avalanche current is quenched, the voltage at the node VZ gradually returns to its initial state, the MOS tube NMOS2 is turned on, and the voltage at the node VN is reset to the reference voltage VREF, so that the APD detector returns to the Geiger mode again and waits for the next photon detection.

[0048] In summary, the present invention proposes an avalanche detection circuit and a dual-mode APD detector based on the avalanche detection circuit. This circuit utilizes a current feedback control structure at the circuit's avalanche current input node to eliminate the effects of dark current and background current, while simultaneously utilizing a voltage feedback control structure to automatically quench and reset the APD in Geiger mode. Furthermore, the present invention enables the avalanche detection circuit to freely switch between the linear and Geiger operating modes of the APD detector simply by adjusting a variable resistor and a high-voltage power supply, eliminating the need for two independent avalanche signal processing circuits. This makes the detector more flexible and convenient to use.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. An avalanche detection circuit, characterized in that: The device comprises an input MOS tube, a voltage feedback control module, a current feedback control module, a follower, and a charge-sensitive amplifier; the drain of the input MOS tube receives the photocurrent; the output end of the voltage feedback control module is connected to the gate of the input MOS tube; the input end of the current feedback control module is connected to the source of the input MOS tube, and is used to eliminate the noise current flowing through the input MOS tube and output the photocurrent transmitted by the input MOS tube to the charge-sensitive amplifier; The follower is arranged between the voltage feedback control module and the current feedback control module, and the input end of the follower is connected to the output end of the current feedback control module, transferring the output voltage generated by the current feedback control module due to the photocurrent to the input end of the voltage feedback control module, so that the voltage feedback control module controls the gate voltage of the input MOS tube.

2. The avalanche detection circuit according to claim 1, wherein: The current feedback control module includes a feedback-common-gate amplifier unit, a delay unit and a transistor NPN1; the input end of the feedback-common-gate amplifier unit and the collector of the transistor NPN1 are both connected to the source of the input MOS tube; the output end of the feedback-common-gate amplifier unit is respectively connected to the input end of the charge-sensitive amplifier and the follower; the input end of the delay unit is connected to the output end of the follower, and the output end of the delay unit is connected to the base of the transistor NPN1; the emitter of the transistor NPN1 is grounded.

3. The avalanche detection circuit according to claim 2, wherein: The feedback-common-gate amplifier unit includes an amplifier, a flow-through MOS transistor and a resistor R1; the positive input terminal of the amplifier is connected to the reference voltage, the negative input terminal is connected to the source of the input MOS transistor, and the output terminal of the amplifier is connected to the gate of the flow-through MOS transistor; the source of the flow-through MOS transistor is connected to the source of the input MOS transistor, and the drain of the flow-through MOS transistor is respectively connected to the second end of the resistor R1, the input end of the follower and the input end of the charge-sensitive amplifier; the first end of the resistor R1 is connected to the power supply VDD.

4. The avalanche detection circuit according to claim 2, wherein: The delay unit includes a resistor R2 and a capacitor C; the first end of the resistor R2 is connected to the output end of the follower, and the second end is connected to the base of the transistor NPN1 and the first end of the capacitor C respectively, and the second end of the capacitor C is grounded.

5. The avalanche detection circuit according to claim 1, wherein: The voltage feedback control module includes a variable resistor R4, a resistor R3 and a transistor NPN2; the first end of the variable resistor R4 is connected to the power supply VDD, and the second end is respectively connected to the gate of the input MOS tube and the first end of the resistor R3; the collector of the transistor NPN2 is connected to the second end of the resistor R3, the base is connected to the output end of the follower, and the emitter is grounded.

6. A dual-mode APD detector comprising an avalanche photodiode, characterized in that: It also includes an avalanche detection circuit according to any one of claims 1 to 5, wherein the cathode end of the avalanche photodiode is connected to a high-voltage power supply, and the anode end of the avalanche photodiode is connected to the drain of the input MOS tube in the avalanche detection circuit; the APD detector is switched between linear mode and Geiger mode by adjusting the resistance value of the variable resistor in the avalanche detection circuit and the voltage value of the high-voltage power supply.

7. The APD detector according to claim 6, characterized in that: By adjusting the resistance of the variable resistor to zero and adjusting the voltage of the high-voltage power supply so that the voltage across the avalanche photodiode is lower than the avalanche breakdown voltage, the APD detector is switched to the linear mode; By adjusting the resistance of the variable resistor to R R4 , and at the same time adjust the voltage of the high-voltage power supply so that the voltage across the avalanche photodiode is higher than the avalanche breakdown voltage, thereby switching the APD detector to the Geiger mode; wherein the resistance R R4 The following conditions are met: when the pulse current output from the source of the input MOS tube reaches a preset threshold, the voltage difference between the gate and the source of the input MOS tube is lower than the turn-on voltage of the input MOS tube.

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