Sensor circuit and driving method

Abstract

The application provides a sensor circuit and a driving method thereof, and relates to the technical field of detection. In the sensor circuit, a single photon avalanche diode (SPAD) detection unit is configured to receive a bias voltage; a first end of the detection unit is connected to GND, and a second end is connected to a first driving voltage through a first driving transistor; a voltage conversion module is used for outputting the first driving voltage and a second driving voltage, wherein the first driving voltage is higher than the second driving voltage; and the second driving voltage is used for at least part of an output circuit. In this way, the isolation of the high driving voltage and the low driving voltage in the same sensor circuit is realized, and the energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a sensor circuit and a driving method thereof. BACKGROUND

[0002] In recent years, with the progress of semiconductor technology, miniaturization of distance measuring modules for measuring distances to objects has been achieved. Therefore, for example, it has been realized to install distance measuring modules in mobile terminals such as so-called smart phones, which are small-sized information processing devices with communication functions. With the progress of technology, in the process of distance or depth information detection, the method frequently used is the time of flight (TOF) ranging method, which is based on the principle of continuously sending light pulses to a target object, and then receiving the light returned from the object with a sensor, and obtaining the distance of the target object by detecting the flight (round trip) time of the light pulses. In the TOF technology, the technology of directly measuring the flight time of light is called DTOF (direct-TOF); the measurement technology of periodically modulating the transmitted light signal, measuring the phase delay of the reflected light signal relative to the transmitted light signal, and then calculating the flight time from the phase delay is called ITOF (Indirect-TOF) technology. According to the different types of modulation and demodulation, it can be divided into continuous wave (CW) modulation and demodulation mode and pulse modulation (PM) modulation and demodulation mode. Direct time of flight (DTOF) is one of TOF, which directly obtains the target distance by calculating the transmission and reception time of the light pulse, has the advantages of simple principle, good signal-to-noise ratio, high sensitivity, high accuracy, etc., and has received more and more attention.

[0003] DToF is a direct distance measurement based on the time difference between pulse transmission and reception. At the moment of laser emission, an electronic clock is activated. The light beam steering unit directs the pulse to the desired direction. The pulse is reflected back from the target, and part of it is received by the photodetector.

[0004] In response, the photodetector connected to the front-end electronic device generates an electrical signal, thereby validating the clock. By measuring the flight time Δt, the distance d between the reflected object is calculated, and the calculation formula is d = cΔt / 2, where c refers to the speed of light in the medium.

[0005] The avalanche photodiode has linear mode, Geiger mode and several other working states. The avalanche photodiode in Geiger mode is often used as single photon detection due to its extremely high gain, and is also called single photon avalanche diode (SPAD). The SPAD is the most core technology for implementing DToF.

[0006] The SPAD is applied with a reverse voltage on the PN junction, and an avalanche phenomenon occurs when the reverse voltage difference reaches the avalanche voltage. There are two ways to achieve the reverse voltage at present. One is to apply a negative high voltage to the anode of the SPAD and a positive low voltage to the cathode of the SPAD, so as to achieve a large reverse voltage difference and reach the avalanche voltage. The other way is that the anode of the SAPD is connected to GND, and the cathode is applied with a positive high voltage so as to achieve a large reverse voltage difference and reach the avalanche voltage. However, in the second implementation mode, the sensor circuit needs to provide a high positive voltage to the SPAD cathode and also needs to provide a voltage to the output circuit. The output circuit does not need such a high voltage, and if all high voltages are used, the power consumption will be increased. Therefore, a sensor circuit is needed to provide a high positive voltage to the SPAD

[0007] cathode and a voltage for the normal operation of the output circuit. SUMMARY

[0008] The purpose of the present application is to provide a sensor circuit and a driving method to solve the technical problems of the existing sensor circuit that the high driving voltage and the low driving voltage cannot be isolated and the power consumption is high.

[0009] To achieve the above purpose, the technical solutions adopted by the embodiments of the present application are as follows:

[0010] In a first aspect, the embodiments of the present application provide a sensor circuit, comprising: a single photon avalanche diode (SPAD) detection unit configured to receive a bias voltage; the first end of the detection unit is connected to GND, and the second end is connected to a first driving voltage through a first driving transistor;

[0011] a voltage conversion module for outputting the first driving voltage and a second driving voltage, wherein

[0012] the first driving voltage is higher than the second driving voltage; and the second driving voltage is used at least for part of the output circuit.

[0013] Optionally, the first driving voltage is at least the bias voltage for driving the avalanche of the SPAD detection unit.

[0014] Optionally, the first driving voltage and the second driving voltage are electrically connected through the voltage conversion module.

[0015] Optionally, the first driving voltage and the second driving voltage have a consistent variation trend, and a proportional relationship exists between the first driving voltage and the variation amount of the second driving voltage.

[0016] Optionally, the proportional relationship between the first driving voltage and the second driving voltage is realized through a capacitor.

[0017] In a second aspect, an embodiment of the present application provides a driving method of a sensor circuit, applied to the sensor circuit in the first aspect, and the driving method of the sensor circuit comprises the following steps of:

[0018] a voltage conversion module, configured to output a first driving voltage to a second end of a SPAD detection unit;

[0019] a voltage conversion module, configured to output a second driving voltage to at least part of an output circuit of the sensor;

[0020] connecting the second end of the SPAD detection unit to GND.

[0021] Optionally, the first driving voltage is at least a bias voltage for driving avalanche of the SPAD detection unit.

[0022] Optionally, the first driving voltage and the second driving voltage are electrically connected through the voltage conversion module.

[0023] Optionally, the first driving voltage and the second driving voltage have a consistent variation trend, and a proportional relationship exists between the first driving voltage and the variation amount of the second driving voltage.

[0024] Optionally, the proportional relationship between the first driving voltage and the second driving voltage is realized through a capacitor.

[0025] The beneficial effects of the present application are as follows:

[0026] An embodiment of the present application provides a sensor circuit and a driving method, and the sensor circuit comprises:

[0027] a single photon avalanche diode (SPAD) detection unit, configured to receive a bias voltage; a first end of the detection unit is connected to GND, and a second end is connected to a first

[0028] driving voltage through a first driving transistor;

[0029] a voltage conversion module, configured to output the first driving voltage and a second driving voltage, wherein

[0030] The first driving voltage is higher than the second driving voltage; and the second driving voltage is used for at least part of the output circuit. The sensor circuit and the driving method provided by the present application can isolate the high driving voltage and the low driving voltage in the same circuit, and reduce power consumption. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced as follows. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0032] Figure 1 A schematic diagram of avalanche breakdown of a PN junction of the prior art provided for the embodiments of the present application;

[0033] Figure 2 A circuit schematic diagram of a SPAD provided for the embodiments of the present application;

[0034] Figure 3 A timing diagram of a SPAD circuit provided for the embodiments of the present application;

[0035] Figure 4 A schematic diagram of a sensor circuit driving method provided for the embodiments of the present application. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.

[0037] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. All other embodiments obtained by those skilled in the art on the basis of the embodiments in the present application without creative labor are within the scope of protection of the present application.

[0038] It should be noted that: similar reference numerals and letters represent similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0039] Figure 1 A schematic diagram of avalanche breakdown of a PN junction of the prior art provided for the embodiments of the present application. As shown in the figure, the avalanche breakdown of the PN junction is caused by the high driving voltage.Figure 1 As shown in the figure, in the PN junction with lower material doping concentration, when the reverse voltage of the PN junction increases, the electric field in the space charge region is enhanced. Thus the electrons and holes passing through the space charge region will gain energy under the action of the electric field, and the electrons and holes running in the crystal will continuously collide with the atoms in the crystal. Through such collisions, the valence electrons bound in the covalent bond can be collided out to generate free electron-hole pairs. The newly generated carriers will collide with other neutral atoms under the action of the electric field to generate new free electron-hole pairs. Such a chain reaction causes the number of carriers in the barrier layer to increase sharply, and thus the reverse current flowing through the PN junction increases sharply. Because the growth rate is extremely fast, it is like an avalanche, so this collision ionization is called avalanche breakdown. The voltage at this time is called avalanche breakdown voltage. As shown in the figure, in the actual SPAD device, the anode is connected to the negative pole or GND of the power supply, and the cathode is connected to the positive pole of the power supply. When the voltage difference between the anode and the cathode of the SPAD reaches the avalanche voltage, the avalanche phenomenon occurs. Figure 1

[0040] Figure 2 ​A circuit schematic of a SPAD is provided for the embodiments of the present application. In order to ensure that the system has a certain initial state, the SPAD is connected to the first driving voltage through the first driving transistor MP1, and when the system is powered on, the Por system state fixing signal controls the photodiode to have a certain initial state. At this time, the period is restored to the maximum driving voltage, and the pixel unit working in the actual detection is selected. At this time, the system state fixing transistor becomes high level, so the transistor is in the off state. The maintenance of the initial state makes the selected unit of the detector consistent in the working state, and there is no need to worry about the interference of historical signals each time it is used. On the other hand, it can also ensure that the pixel unit is quickly set to the working voltage mode and quickly put into the working state. As previously described, the basic working principle of the SPAD detection unit, the SPAD unit of the pixel driving circuit of the present scheme is connected to the ground at one end, so that all adjustments are set at the other end. The circuit driving module of the present scheme is provided with a high voltage driving generation part, thereby realizing the unification of the output voltage and the overall design of the entire circuit.In order to realize that the SPAD is in an avalanche state, it is necessary to make the first driving voltage higher than the SPAD avalanche threshold voltage, for example, when the avalanche threshold voltage of the SPAD is 20V, the first driving voltage here can be higher than the avalanche threshold voltage by 2-5V, so as to ensure that each avalanche diode can be excited by the first driving voltage and reach an avalanche state, and the specific value is not limited here, for example, the first driving voltage at this time can be 23V, in the initial detection, the working unit has been applied with a driving voltage of 23V, and the voltage across the avalanche diode reaches 23V which is higher than the threshold voltage, at this time, the SPAD unit is in an avalanche state, when the photon event is fed back to the photodiode, the SPAD is triggered so as to be able to perceive the return trigger information of the photon, but after the SPAD unit is excited, it needs to be quenched quickly, that is, the voltage across the SPAD unit is pulled down, so as to avoid continuous avalanche, and the quenching time is actually very important for single-photon type detectors, and it is too long, which may cause a series of problems such as post-pulse triggering, etc. The traditional quenching adopts a large resistance scheme, so the quenching current will be very small, and there are a series of technical problems such as that it is difficult to obtain the signal, etc. The quenching module of the present application is a direct active quenching mode, its working mechanism is different from that of the passive quenching with a resistor, and the principle is as follows: a third voltage output part is arranged in the quenching module, which can output a third voltage value lower than the threshold value of the SPAD, for example, 1-5V lower than the threshold voltage, and 18V is taken as an example here for illustration, for example, the second end of the SPAD detection unit can be connected to a voltage source with a third voltage value through a transistor, when the SPAD detects the excited information, an avalanche occurs, at this time, the gate voltage signal of the sensing signal generating transistor in the circuit is generated, so that the voltage output of the third voltage value is output to the second end of the SPAD, at this time, since the voltage of the avalanche diode is forcibly pulled down, the entire avalanche state can be stopped in time, of course, the minimum voltage caused by the avalanche state is the third voltage, and the difference between the third voltage and the first driving voltage is small, rather than being directly reduced to close to 0V, so that the time for subsequent recovery to the avalanche state can also be realized, so as to ensure the efficiency of the detection process, and also ensure the accuracy of the detection result. Figure 3The process that the voltage caused by the photon event is reduced from the highest first driving voltage to the third voltage is embodied in the timing diagram. When the voltage across the SPAD unit is reduced to the third voltage, the recovery module of the quenching module receives a control signal, so that the first driving voltage is applied to the second end of the SPAD. Here, the connection end of the recovery module and the third voltage is separated for exemplary illustration, and in fact, the third voltage output end and the output end of the third voltage can be the same node, which is not limited here. When the second end of the SPAD is connected to the driving voltage through the recovery module, the voltage across the SPAD unit can be quickly pulled up from the third voltage to the first voltage, so as to quickly recover to a state capable of being excited, and complete the information detection of one photon event. When the voltage across the SPAD unit recovers to the first driving voltage, detection can be performed again, so that the continuity of the single photon event can be achieved.

[0041] As Figure 2 The circuit also includes an output part of the SPAD excited information driven by the second driving voltage. The output part and the quenching module can be connected through a coupling part. The coupling part can be a capacitor. The coupling part can couple the rise after the voltage caused by the photon event in the quenching module is reduced to an analog follow-up signal with a lower voltage. Since the voltage is generally low in the processing of the data signal, for example, the driving voltage of the third voltage 3.3V can be used here (only for exemplary illustration and is not limited to this voltage value). In this way, the high voltage change caused by the photon trigger is converted into a low voltage change through the coupling part, the signal input range of the output part is achieved, and the processing device of the output part also does not have special requirements. The entire output part can be designed by using the existing device. The low voltage change transmitted by the output part through the processing of the coupling part finally obtains the output signal of the SPAD excited.

[0042] Figure 3 A timing diagram of a SPAD circuit is provided for the embodiment. As shown in the SPAD circuit shown in Figure 2 The timing of the SPAD circuit is shown in Figure 3 After the system is powered on, the por signal is low, the node diode cathode voltage is reset to the first driving voltage, and the output part voltage is reset to the second driving voltage. The SPAD enters the detection state.

[0043] When the SPAD detects a photon, the photodiode cathode voltage starts to rapidly decrease from the first driving voltage, and the output part voltage starts to decrease from the second driving voltage. The photodiode cathode voltage is finally reduced to the third voltage. With the decrease of the output part voltage, the second driving voltage is reduced to 0V, and the voltage of the recovery module is reduced from the first driving voltage to reset the voltage of the photodiode to the first driving voltage. After the reset is completed, the voltage is raised, and finally the reset of the SPAD is completed, and the SPAD reenters the detection state.Figure 3 The first voltage and the second voltage have the same change trend, and the change trend can be realized by a capacitor, and the change amount of the left and right plates of the capacitor is in a proportional relationship.

[0044] Figure 4 A sensor circuit driving method is provided for the embodiments of the present application. The method can be applied to the aforementioned sensor circuit, and the basic principle and technical effects of the method are the same as those of the corresponding sensor circuit embodiments. For brevity, the parts not mentioned in the present embodiment can refer to the corresponding contents in the sensor circuit embodiments. As shown in the figure, the driving method comprises: Figure 4

[0045] S101, a voltage conversion module outputs a first driving voltage to the second end of the SPAD detection unit;

[0046] S102, a voltage conversion module outputs a second driving voltage to at least part of the output circuit of the sensor;

[0047] S103, the second end of the SPAD detection unit is connected to GND.

[0048] Optionally, the first driving voltage is at least a bias voltage for driving avalanche of the SPAD detection unit.

[0049] Optionally, the first driving voltage and the second driving voltage are electrically connected through the voltage conversion module.

[0050] Optionally, the first driving voltage and the second driving voltage have the same change trend, and there is a proportional relationship between the change amount of the first driving voltage and the second driving voltage.

[0051] Optionally, the proportional relationship between the first driving voltage and the second driving voltage is realized by a capacitor.

[0052] The above method is applied to the sensor circuit provided by the aforementioned embodiments, and the implementation principle and technical effects are similar, which will not be repeated here.

[0053] ​It has to be noted that, in the present document, relational terms are intended only to convey a possible relationship between elements or items or

[0054] The foregoing is merely illustrative of the principles of this application and various modifications can be made by those skilled in the art without departing from the scope and spirit of the application. Accordingly, the disclosure of the present application is intended to be illustrative, but not limiting, of the scope of the application, which is set forth in the following claims. It is noted that, as used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component" can include mixtures of two or more such components, and the like. It is further noted that the claims can be drafted to exclude any element or step considered to be unnecessary for the practice of the application and this application can be defined solely by the appended claims and equivalents thereof.

Claims

1. A sensor circuit, comprising: a single photon avalanche diode (SPAD) detection unit configured to receive a bias voltage; a first end of the detection unit is connected to GND, and a second end is connected to a first driving voltage through a first driving transistor, a gate signal of the first driving transistor is used to control the single photon avalanche diode detection unit to maintain a determined initial state; a voltage conversion module for outputting the first driving voltage to the second end of the SPAD detection unit and outputting a second driving voltage to at least part of an output circuit, wherein the first driving voltage is higher than the second driving voltage; the first driving voltage and the second driving voltage are electrically connected through the voltage conversion module; a quenching module of the single photon avalanche diode detection unit is internally provided with a third voltage output part, the third voltage output part is connected to the second end of the SPAD detection unit through a transistor, when the SPAD detection unit is excited to avalanche, a gate voltage signal of a sensing signal generating transistor inside the circuit is generated, so that the voltage output of the third voltage value is output to the second end of the SPAD, ensuring that the whole avalanche state is stopped in time; when the gate signal of the first driving transistor is low, the cathode voltage of the single photon avalanche diode (SPAD) detection unit is reset to the first driving voltage, and the output part voltage is reset to the second driving voltage, when the single photon avalanche diode (SPAD) detection unit detects a photon, the cathode voltage of the single photon avalanche diode (SPAD) detection unit decreases from the first driving voltage to a third driving voltage, and the output circuit voltage decreases from the second driving voltage to 0V.

2. The sensor circuit of claim 1, wherein: the first driving voltage is at least a bias voltage for driving the SPAD detection unit to avalanche.

3. The sensor circuit of claim 1, wherein: the first driving voltage and the second driving voltage have consistent variation trends, and there is a proportional relationship between the variation amount of the first driving voltage and the second driving voltage.

4. The sensor circuit of claim 3, wherein: the proportional relationship between the first driving voltage and the second driving voltage is realized through a capacitor.

5. A driving method of a sensor circuit, comprising: the method is applied to the sensor circuit of claim 1, and the method comprises: a voltage conversion module outputs a first driving voltage to a second end of a SPAD detection unit; a voltage conversion module outputs a second driving voltage to at least part of an output circuit of a sensor; a first end of the SPAD detection unit is connected to GND; When the gate signal of the first driving transistor is low, the cathode voltage of the single photon avalanche diode (SPAD) detection unit is reset to the first driving voltage, and the output part voltage is reset to the second driving voltage; when the single photon avalanche diode (SPAD) detection unit detects photons, the cathode voltage of the single photon avalanche diode (SPAD) detection unit decreases from the first driving voltage to a third driving voltage, and the output part voltage decreases from the second driving voltage to 0V.

6. The driving method of the sensor circuit according to claim 5, wherein the first driving voltage is at least a bias voltage for driving the SPAD detection unit avalanche.

7. The driving method of the sensor circuit according to claim 5, wherein the first driving voltage and the second driving voltage are electrically connected through the voltage conversion module.

8. The driving method of the sensor circuit according to claim 5, wherein the first driving voltage and the second driving voltage have consistent variation trends, and there is a proportional relationship between the variation amount of the first driving voltage and the second driving voltage.

9. The driving method of the sensor circuit according to claim 5, wherein the proportional relationship between the first driving voltage and the second driving voltage is realized through a capacitor. ​ ​ ​ ​

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