Pixel circuit, image sensor, camera module, device and control method

Abstract

This application discloses a pixel circuit, an image sensor, a camera module, a device, and a control method, relating to the field of electronic technology. The pixel circuit includes a photodiode, an output module, and at least two shunt modules. The photodiode is electrically connected to both the output module and each shunt module. The total current converted by the photodiode is equal to the sum of a first shunt current and a second shunt current. The first shunt current is the current input from the photodiode to the output module, and the second shunt current is the current input from the shunt modules that are turned on by the photodiode. The output module is used to convert the first shunt current into voltage and output it. The number of shunt modules that are turned on is positively correlated with the total current value.

Description

Technical Field

[0001] This application belongs to the field of electronic technology, specifically relating to a pixel circuit, an image sensor, a camera module, a device, and a control method. Background Technology

[0002] An image sensor is a device that converts optical images into electronic signals, and pixel circuits are the basic units that make up an image sensor.

[0003] In related technologies, the total current converted by the photodiode in the pixel circuit is converted into voltage and output. Then, it undergoes analog-to-digital conversion, i.e., the conversion of analog signals into digital signals, to form the image data of the pixel. It should be noted that the output voltage of the pixel circuit is positively correlated with the brightness of the pixel image.

[0004] However, when the light intensity increases, the total current converted by the photodiodes in the pixel circuit increases, and the voltage output according to the total current increases, resulting in the pixel image being too bright and the details being blurred, thus reducing the image clarity of the pixel. Summary of the Invention

[0005] Embodiments of this application provide a pixel circuit, an image sensor, a camera module, a device, and a control method to avoid overly bright pixel images and improve the clarity of pixel images.

[0006] In a first aspect, embodiments of this application provide a pixel circuit, including: a photodiode, an output module, and at least two shunt modules;

[0007] The photodiode is electrically connected to the output module and each shunt module; the total current converted by the photodiode is equal to the sum of the first shunt current and the second shunt current; the first shunt current is the shunt current input by the photodiode to the output module, and the second shunt current is the shunt current input by the shunt module turned on by the photodiode; the output module is used to convert the first shunt current into voltage and output it.

[0008] The number of the shunt modules that are turned on is positively correlated with the total current value.

[0009] Secondly, embodiments of this application also provide an image sensor, including the pixel circuit described in the first aspect.

[0010] Thirdly, embodiments of this application also provide a camera module, including the image sensor as described in the second aspect.

[0011] Fourthly, embodiments of this application also provide an electronic device, including the camera module as described in the third aspect.

[0012] Fifthly, embodiments of this application also provide a pixel circuit control method, executed by the electronic device as described in the fourth aspect, the method comprising:

[0013] Obtain the voltage value of the cathode of the photodiode;

[0014] The shunt module, whose voltage value matches that of the cathode, is turned on;

[0015] The number of shunt modules that match the voltage value of the cathode is negatively correlated with the voltage value of the cathode.

[0016] In this embodiment, since the total current converted by the photodiode is equal to the sum of the first current received by the output module and the second current received by each conducting shunt module, the more conducting shunt modules there are, the smaller the first current received by the output module and the smaller the output voltage. Since the number of conducting shunt modules is positively correlated with the total current converted by the photodiode, when the total current increases, the number of conducting shunt modules increases, which reduces the first current received by the output module. Therefore, the increase in output voltage caused by the increase in total current can be reduced. Compared with related technologies, this avoids overly bright pixel images and improves the image clarity of pixels. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a pixel circuit provided in some embodiments of this application;

[0018] Figure 2 This is a schematic diagram of a specific structure of a pixel circuit provided in some embodiments of this application;

[0019] Figure 3 This is a schematic diagram of an image sensor provided in some embodiments of this application;

[0020] Figure 4 These are schematic diagrams of images acquired according to some embodiments of this application;

[0021] Figure 5 These are two schematic diagrams of pixel circuits provided in some embodiments of this application;

[0022] Figure 6 These are schematic diagrams of electronic devices provided in some embodiments of this application;

[0023] Figure 7 This is a flowchart of the steps of a pixel circuit control method provided in some embodiments of this application.

[0024] Explanation of reference numerals in the attached figures:

[0025] 10 - Photodiode; 20 - Output module; 21 - Output sub-module; 30 - Shunt module; Q1 - First switching device; Q2 - Second switching device; Q3 - Third switching device; Q4 - Reset switching device; Q5 - Selector switching device; C1 - First capacitor; C2 - Second capacitor. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0027] The terms "first," "second," and the like in the specification and claims of this application are used to distinguish similar objects, and are not used to describe a specific order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments of this application can be implemented in an order other than that illustrated or described herein, and that the objects distinguished by "first," "second," and the like are generally of the same type, and do not limit the number of objects; for example, the first object can be one or more. In addition, the term "and / or" in the specification and claims refers to at least one of the connected objects, and the character " / " generally indicates that the objects connected are in an "or" relationship.

[0028] Reference Figure 1 This application provides a pixel circuit including a photodiode 10, an output module 20, and at least two shunt modules 30. The photodiode 10 is electrically connected to the output module 20 and each shunt module 30. The total current converted by the photodiode 10 is equal to the sum of a first shunt current and a second shunt current. The first shunt current is the shunt current input from the photodiode 10 to the output module 20, and the second shunt current is the shunt current input from the photodiode 10 to the conducting shunt module 30. The output module 20 is used to convert the first shunt current into a voltage and output it. The number of conducting shunt modules 30 is positively correlated with the total current value.

[0029] It should be noted that the output module 20 and each shunt module 30 are connected in parallel; the output voltage of the output module 20 is the voltage generated by the conversion of the first shunt current.

[0030] Photodiode 10 is used to convert light signals into electrical signals, which are the signals of the total current converted by photodiode 10. During exposure, photodiode 10 operates in a reverse bias state. The total current converted by photodiode 10 is the current generated by photodiode 10 after converting light signals. The total current converted by photodiode 10 is positively correlated with the light intensity of the exposure. The total current converted by photodiode 10 includes photocurrent and dark current. Photocurrent is the effective signal and is related to photosensitivity and exposure time. Dark current is noise and is affected by semiconductor process, temperature, and exposure time.

[0031] The current shunt module 30 is used to shunt the total current converted by the photodiode 10 when the current shunt module 30 is turned on, so as to reduce the first shunt current obtained by the output module 20.

[0032] For example, the pixel circuit includes a photodiode 10, an output module 20, and two shunt modules 30. When the total current converted by the photodiode 10 is a first value, the first shunt module 30 is turned on, and the sum of the first shunt current F1 and the second shunt current F2 is equal to the first value. Here, the first shunt current F1 is the shunt current input from the photodiode 10 to the output module 20, and the second shunt current F2 is the shunt current input from the first shunt module 30 when the photodiode 10 is turned on.

[0033] When the total current converted by photodiode 10 is the second value, both shunt modules 30 are turned on. The sum of the current values ​​of the first shunt current F3, the second shunt current F4, and the second shunt current F5 is equal to the second value. The first value is less than the second value. The first shunt current F3 is the shunt current input from photodiode 10 to output module 20, the second shunt current F4 is the shunt current input from the first shunt module 30 turned on by photodiode 10, and the second shunt current F5 is the shunt current input from the second shunt module 30 turned on by photodiode 10.

[0034] In this embodiment, since the total current converted by the photodiode is equal to the sum of the first current received by the output module and the second current received by each conducting shunt module, the more conducting shunt modules there are, the smaller the first current received by the output module and the smaller the output voltage. Since the number of conducting shunt modules is positively correlated with the total current converted by the photodiode, when the total current increases, the number of conducting shunt modules increases, which reduces the first current received by the output module. Therefore, the increase in output voltage caused by the increase in total current can be reduced. Compared with related technologies, this avoids overly bright pixel images and improves the image clarity of pixels.

[0035] With the total current of conversion decreasing, the number of shunt modules 30 that are turned on decreases, which increases the first shunt current obtained by the output module 20 and the output voltage. This ensures that the pixel image has good brightness in low light environment, avoids the pixel image being too low in brightness and blurry in low light environment, and ensures that the pixel image has good clarity in low light environment.

[0036] Optional, refer to Figure 2 In some embodiments, each of the current shunt modules 30 includes a first switching device Q1, a second switching device Q2, and a first capacitor C1; the anode of the photodiode 10 is grounded, and the cathode of the photodiode 10 is electrically connected to the input terminal of the output module 20 and the first terminal of each of the first switching devices Q1; in the current shunt module 30, the second terminal of the first switching device Q1 is electrically connected to the first terminal of the first capacitor C1, and the control terminal of the first switching device Q1 is used to receive control signals; the first terminal of the second switching device Q2 is used to be electrically connected to an external power supply, the second terminal of the second switching device Q2 is grounded, and the control terminal of the second switching device Q2 is electrically connected to the first terminal of the first capacitor C1; the second terminal of the first capacitor C1 is grounded.

[0037] It should be noted that the first switching device Q1 is turned on and off by a control signal. Specifically, when a control signal of a first level is input to the first switching device Q1, the first switching device Q1 is turned on; when a control signal of a second level is input to the first switching device Q1, the first switching device Q1 is turned off; wherein, the first level and the second level are opposite.

[0038] When the first switching device Q1 is turned on, the shunt module 30 is turned on; when the first switching device Q1 is turned off, the shunt module 30 is turned off; the first capacitor C1 is used to store the charge converted by the photodiode 10 when the first switching device Q1 is turned on.

[0039] Each first switching device Q1 has a corresponding control signal input terminal 41 of the pixel circuit. The control terminal of the first switching device Q1 is electrically connected to the control signal input terminal 41 of the pixel circuit. The control signal input terminal 41 of the pixel circuit is used to receive the control signal of the first switching device Q1.

[0040] In some embodiments of this application, when the total current of the conversion increases, the first switching device Q1 is turned on by inputting a control signal of the first level, thereby increasing the number of the first switching devices Q1 that are turned on, and thus increasing the number of the current shunt modules 30 that are turned on. This reduces the first current shunt obtained by the output module 20, thereby reducing the increase in output voltage caused by the increase in total current. Compared with related technologies, this avoids the pixel image from being too bright, improves the image clarity of the pixel, and ensures that the image of the pixel has good clarity in bright light environments.

[0041] Optionally, in some embodiments, each of the first switching devices Q1 has a corresponding conduction parameter, which is the difference between the voltage value of the control signal of the first switching device Q1 and the conduction threshold of the first switching device Q1; at least a portion of the first switching devices Q1 have different conduction parameters; when the voltage value of the cathode of the photodiode 10 is less than the conduction parameter of the first switching device Q1, the first switching device Q1 is turned on; when the voltage value of the cathode of the photodiode 10 is greater than the conduction parameter of the first switching device Q1, the first switching device Q1 is turned off.

[0042] In some embodiments of this application, by setting the voltage value of the control signal of the first switching device Q1, the difference between the voltage value of the control signal of the first switching device Q1 and the conduction threshold of the first switching device Q1 can be greater than the voltage value of the cathode of the photodiode 10, thereby enabling the first switching device Q1 to be turned on; by setting the voltage value of the control signal of the first switching device Q1, the difference between the voltage value of the control signal of the first switching device Q1 and the conduction threshold of the first switching device Q1 can be less than the voltage value of the cathode of the photodiode 10, thereby enabling the first switching device Q1 to be turned off.

[0043] For example, both the first switching device Q1 and the second switching device Q2 are NMOS transistors, which are negative channel metal-oxide-semiconductor transistors. In the shunt module 30, the gate of the first switching device Q1 is used to receive control signals, the drain of the first switching device Q1 is electrically connected to the cathode of the photodiode 10, and the source of the first switching device Q1 is electrically connected to the first terminal of the first capacitor C1. The first terminal of the first capacitor C1 is electrically connected to the gate of the second switching device Q2, and the second terminal of the first capacitor C1 is grounded. The drain of the second switching device Q2 is electrically connected to an external power supply, and the source of the second switching device Q2 is grounded.

[0044] Optionally, in some embodiments, the output module 20 includes a second capacitor C2 and an output submodule 21; the anode of the photodiode 10 is grounded, and the cathode of the photodiode 10 is electrically connected to the first terminal of the second capacitor C2 and the input terminal of each shunt module 30; the input terminal of the output submodule 21 is electrically connected to the first terminal of the second capacitor C2, and the output submodule 21 is used to convert and output the voltage of the second capacitor C2; the second terminal of the second capacitor C2 is grounded.

[0045] It should be noted that the second capacitor C2 is used to store the charge converted by the photodiode 10.

[0046] In some embodiments of this application, the first current is obtained through the output module 20, the first current is used to charge the second capacitor C2, and the voltage of the second capacitor C2 is converted and output through the output submodule 21 to realize the voltage output of the pixel circuit.

[0047] Optionally, in some embodiments, the output submodule 21 includes a third switching device Q3 and a selection switching device Q5; the first terminal of the third switching device Q3 is electrically connected to an external power supply, and the second terminal of the third switching device Q3 is electrically connected to the first terminal of the selection switching device Q5; the control terminal of the selection switching device Q5 is used to receive a pixel row selection signal, and the second terminal of the selection switching device Q5 is used to output the voltage converted from the voltage of the second capacitor C2.

[0048] It should be noted that the third switching device Q3 is used to convert the voltage of the second capacitor C2 and output the voltage after the voltage of the second capacitor C2 is converted; the selection switching device is used to turn on when the pixel row selection signal is obtained at the control terminal of the selection switching device Q5, and outputs the voltage after the voltage of the second capacitor C2 through the second terminal of the selection switching device Q5.

[0049] In some embodiments of this application, the first current is obtained through the output module 20, and the first current is used to charge the second capacitor C2. When the difference between the voltage value of the second capacitor C2 and the voltage value of the second terminal of the third switching device Q3 is greater than the conduction threshold of the third switching device Q3, the third switching device Q3 is turned on. When the pixel row selection signal is obtained at the control terminal of the selection switching device Q5, the selection switching device Q5 is turned on. The voltage after the voltage of the second capacitor C2 is converted by the output of the second terminal of the selection switching device Q5 to realize the voltage output of the pixel circuit; wherein, the voltage value of the second capacitor C2 is the same as the voltage value of the gate of the third switching device Q3.

[0050] Optionally, in some embodiments, both the third switching device Q3 and the selection switching device Q5 are transistors.

[0051] It should be noted that the control terminal of the selection switch Q5 is electrically connected to the pixel row selection signal input terminal 43 of the pixel circuit, and the pixel row selection signal input terminal 43 is used to receive the pixel row selection signal; the second terminal of the selection switch Q5 is electrically connected to the output terminal 44 of the pixel circuit, and the voltage value VOUT between the output terminal 44 of the pixel circuit and ground is the voltage value of the output voltage of the pixel circuit, and the voltage value VOUT between the output terminal 44 of the pixel circuit and ground is also the voltage value output by the second terminal of the selection switch Q5.

[0052] Specifically, both the third switching device Q3 and the selection switching device Q5 are NMOS transistors. The first terminal of the second capacitor C2 is electrically connected to the gate of the third switching device Q3, the drain of the third switching device Q3 is electrically connected to the external power supply, and the source of the third switching device Q3 is electrically connected to the drain of the selection switching device Q5. The source of the selection switching device Q5 is electrically connected to the output terminal 44 of the pixel circuit, and the gate of the selection switching device Q5 is electrically connected to the pixel row selection signal input terminal 43.

[0053] In some embodiments of this application, since both the third switching device Q3 and the selection switching device Q5 are transistors, when the difference between the voltage value of the second capacitor C2 and the voltage value at the second terminal of the third switching device Q3 is greater than the conduction threshold of the third switching device Q3, the third switching device Q3 is turned on. When the control terminal of the selection switching device Q5 receives the pixel row selection signal, the selection switching device Q5 is turned on. The voltage converted from the voltage of the second capacitor C2 is output through the second terminal of the selection switching device Q5 to realize the voltage output of the pixel circuit; wherein, the voltage value of the second capacitor C2 is the same as the voltage value of the gate of the third switching device Q3.

[0054] In some embodiments, the second terminal of the second switching device Q2 is electrically connected to the first terminal of the selection switching device Q5. When the first switching device Q1 is turned on, the first capacitor C1 is charged by the second current, and the voltage of the first capacitor C1 increases. When the difference between the voltage value of the first capacitor C1 and the voltage value of the second terminal of the second switching device Q2 is greater than the conduction threshold of the second switching device Q2, the second switching device Q2 is turned on. The second terminal of the second switching device Q2 can serve as a redundant structure for the second terminal of the third switching device Q3. That is, when the selection switching device Q5 is turned on and the third switching device Q3 is abnormally turned off, so that the second terminal of the third switching device Q3 has no output, the voltage output by the second terminal of the second switching device Q2 can be used as the output voltage of the pixel circuit.

[0055] The second switching device Q2 has the same model number as the third switching device Q3, and the voltage output from the second terminal of the second switching device Q2 is equal to the voltage output from the second terminal of the third switching device Q3.

[0056] Optionally, in some embodiments, the pixel circuit further includes a reset switch device Q4; the first terminal of the reset switch device Q4 is electrically connected to the external power supply, the second terminal of the reset switch device Q4 is electrically connected to the first terminal of each first switch device Q1, and the control terminal of the reset switch device Q4 is used to receive a reset signal.

[0057] It should be noted that the control terminal of the reset switch device Q4 is electrically connected to the reset signal input terminal 42 of the pixel circuit, and the reset signal input terminal 42 is used to receive the reset signal of the reset switch device Q4.

[0058] The second terminal of the reset switch device Q4 is also electrically connected to the first terminal of the second capacitor C2.

[0059] In some embodiments of this application, when the reset switch Q4 is turned on and the first switch Q1 is turned on, the charge of the first capacitor C1 flows to the external power source. Therefore, the first capacitor C1 can be reset by the reset switch Q4, so that the charge of the first capacitor C1 is zero, and the voltage value of the first capacitor C1 is zero. When the reset switch Q4 is turned on, the charge of the second capacitor C2 flows to the external power source. Therefore, the second capacitor C2 can be reset by the reset switch Q4, so that the charge of the second capacitor C2 is zero, and the voltage value of the second capacitor C2 is zero.

[0060] Optionally, in some embodiments, the reset switch Q4, the first switch Q1, and the second switch Q2 are all transistors.

[0061] Specifically, the reset switch Q4, each first switch Q1, and each second switch are all NMOS transistors.

[0062] In some embodiments of this application, since the reset switch Q4 is a transistor, the reset switch Q4 can be turned on and off through the control terminal of the reset switch Q4; since the first switch Q1 is a transistor, the first switch Q1 can be turned on and off through the control terminal of the first switch Q1; since the second switch Q2 is a transistor, the first switch Q1 can be turned on and off through the control terminal of the second switch Q2.

[0063] Specifically, in some embodiments, the reset switch Q4, each first switch Q1, each second switch Q2, the third switch Q3, and the selection switch Q5 are all NMOS transistors. In the shunt module 30, the gate of the first switch Q1 is used to receive control signals, the drain of the first switch Q1 is electrically connected to the cathode of the photodiode 10, and the source of the first switch Q1 is electrically connected to the first terminal of the first capacitor C1; the first terminal of the first capacitor C1 is electrically connected to the gate of the second switch Q2, and the second terminal of the first capacitor C1 is grounded; the drain of the second switch Q2 is electrically connected to an external power supply, and the source of the second switch Q2 is grounded; the first terminal of the second capacitor C2 is electrically connected to the gate of the third switch Q2. The gate of the third switching device Q3 is electrically connected, the drain of the third switching device Q3 is electrically connected to the external power supply, and the source of the third switching device Q3 is electrically connected to the drain of the selection switching device Q5. The source of the selection switching device Q5 is electrically connected to the output terminal 44 of the pixel circuit, and the gate of the selection switching device Q5 is electrically connected to the pixel row selection signal input terminal 43. The drain of the reset switching device Q4 is electrically connected to the external power supply, and the source of the reset switching device Q4 is electrically connected to the drain of each first switching device Q1 and the first terminal of the second capacitor C2. The gate of the reset switching device Q4 is used to receive the reset signal. The cathode of the photodiode 10 is electrically connected to the drain of each first switching device Q1 and the first terminal of the second capacitor C2.

[0064] In some embodiments, the output voltage value of the pixel circuit is calculated using formula (1):

[0065]

[0066] Where V is the output voltage value of the pixel circuit, U s U is the source output voltage of the third switching device Q3, w is the amplification factor of the third switching device Q3, and U is the voltage value output from the source. g U is the gate voltage of the third switching device Q3. c q is the voltage value of the second capacitor C2, c is the charge of the second capacitor C2, c is the total capacitance value obtained by adding the capacitance value of the first capacitor C1 and the capacitance value of the second capacitor C2 in each conducting shunt module 30, i is the current value of the total current converted by the photodiode 10, and t is the exposure time.

[0067] It should be noted that the amplification factor w of the third switching device Q3 is usually less than 1; in an ideal situation, the amplification factor w of the third switching device Q3 is 1, and the third switching device Q3 is equivalent to a voltage follower. The amplification factor w of the third switching device Q3 is the gain factor of the third switching device Q3.

[0068] The more shunt modules 30 that are turned on, the larger the total capacitance value c, and the smaller the output voltage value V of the pixel circuit. Therefore, the number of shunt modules 30 that are turned on is negatively correlated with the output voltage value V of the pixel circuit.

[0069] In some embodiments, the reset switch Q4, each first switch Q1, each second switch Q2, the third switch Q3, and the selection switch Q5 are all NMOS transistors. In the shunt module 30, the gate of the first switch Q1 is used to receive a control signal, the source of the first switch Q1 is electrically connected to the cathode of the photodiode 10, and the drain of the first switch Q1 is electrically connected to the first terminal of the first capacitor C1. The first terminal of the first capacitor C1 is electrically connected to the gate of the second switch Q2, and the second terminal of the first capacitor C1 is grounded. The drain of the second switch Q2 is electrically connected to an external power supply, and the source of the second switch Q2 is grounded. The first terminal of the second capacitor C2 is connected to the gate of the third switch Q5. The gate of device Q3 is electrically connected, the drain of the third switching device Q3 is electrically connected to the external power supply, and the source of the third switching device Q3 is electrically connected to the drain of the selection switching device Q5. The source of the selection switching device Q5 is electrically connected to the output terminal 44 of the pixel circuit, and the gate of the selection switching device Q5 is electrically connected to the pixel row selection signal input terminal 43. The drain of the reset switching device Q4 is electrically connected to the external power supply, and the source of the reset switching device Q4 is electrically connected to the drain of each first switching device Q1 and the first terminal of the second capacitor C2. The gate of the reset switching device Q4 is used to receive the reset signal. The cathode of the photodiode 10 is electrically connected to the drain of each first switching device Q1 and the first terminal of the second capacitor C2.

[0070] It should be noted that when the NMOS transistor is turned on, current can flow from the drain of the NMOS transistor to the source of the NMOS transistor, or current can flow from the source of the NMOS transistor to the drain of the NMOS transistor.

[0071] For example, the pixel circuit in the image sensor includes a photodiode 10, an output module 20, and two shunt modules 30; each shunt module 30 includes a first switching device Q1, a second switching device Q2, and a first capacitor C1; the output module 20 includes a second capacitor C2 and an output sub-module 21; the output sub-module 21 includes a third switching device Q3 and a selection switching device Q5; each of the first switching device Q1, each of the second switching device Q2, the third switching device Q3, and the selection switching device Q5 is an NMOS transistor; wherein, in each shunt module 30, the gate of the first switching device Q1 is used to receive a control signal, the source of the first switching device Q1 is electrically connected to the cathode of the photodiode 10, and the drain of the first switching device Q1 is electrically connected to the first terminal of the first capacitor C1.

[0072] By setting the voltage value of the control signal, the first difference obtained by subtracting the conduction threshold of the first switching device Q1 in the first shunt module 30 from the gate voltage value of the first switching device Q1 is greater than the second difference obtained by subtracting the conduction threshold of the first switching device Q1 in the second shunt module 30 from the gate voltage value of the first switching device Q1 in the second shunt module 30.

[0073] When the voltage value of the cathode of photodiode 10 is the first voltage value, where the voltage value of the cathode of photodiode 10 is the same as the voltage value of the source of the first switching device Q1, the first voltage value is greater than the first difference and the first voltage value is greater than the second difference, the first switching device Q1 in the first shunt module 30 and the first switching device Q1 in the second shunt module 30 are both disconnected, and the output voltage value of the pixel circuit is calculated by formula (2):

[0074]

[0075] Among them, V a The output voltage value of the pixel circuit is denoted by , w is the amplification factor of the third switching device Q3, and i is the output voltage value of the pixel circuit. a t is the total current value converted by photodiode 10 in the pixel circuit, t is the exposure time, and c1 is the capacitance value of the second capacitor C2.

[0076] When the light intensity of the image acquired by the pixel circuit increases, the total current value converted by the photodiode 10 increases, and the voltage value of the cathode of the photodiode 10 decreases from the first voltage value to the second voltage value. The second voltage value is less than the first difference and greater than the second difference. Therefore, the first switching device Q1 in the first shunt module 30 is turned on, and the first switching device Q1 in the second shunt module 30 is turned off. At this time, the output voltage value of the pixel circuit is calculated by formula (3):

[0077]

[0078] Among them, V b The output voltage value of the pixel circuit is denoted by , w is the amplification factor of the third switching device Q3, and i is the output voltage value of the pixel circuit. b t is the total current value converted by the photodiode 10 in the pixel circuit, t is the exposure time, c1 is the capacitance value of the second capacitor C2, and c2 is the capacitance value of the first capacitor C1 in the first shunt module 30.

[0079] When the illumination intensity of the image acquired by the pixel circuit further increases, the total current value converted by the photodiode 10 further increases, and the voltage value of the cathode of the photodiode 10 decreases from the second voltage value to the third voltage value. The third voltage value is less than the first difference and less than the second difference. Therefore, the first switching device Q1 in the first shunt module 30 and the first switching device Q1 in the second shunt module 30 are both turned on. At this time, the output voltage value of the pixel circuit is calculated by formula (4):

[0080]

[0081] Among them, V c The output voltage value of the pixel circuit is denoted by , w is the amplification factor of the third switching device Q3, and i is the output voltage value of the pixel circuit. c C1 is the total current value converted by the photodiode 10 in the pixel circuit, t is the exposure time, C1 is the capacitance value of the second capacitor C2, C2 is the capacitance value of the first capacitor C1 in the first current shunt module 30, and C3 is the capacitance value of the first capacitor C1 in the second current shunt module 30.

[0082] In some embodiments, the second switching device Q2 is of the same type as the third switching device Q3, and the source of the second switching device Q2 is electrically connected to the drain of the selection switching device Q5. When the first switching device Q1 is turned on, the first capacitor C1 is charged by the second shunt current. When the difference between the voltage value of the first capacitor C1 and the voltage value of the source of the second switching device Q2 is greater than the conduction threshold of the second switching device Q2, the second switching device Q2 is turned on. At this time, the voltage value output from the source of the second switching device Q2 is equal to the product of the amplification factor of the second switching device Q2 and the voltage value of the gate of the second switching device Q2. Since the second switching device Q2 is of the same type as the third switching device Q3, the amplification factor of the second switching device Q2 is equal to the amplification factor of the third switching device Q3. Since the shunt module 30 is turned on... Since the first capacitor C1 and the second capacitor C2 are connected in parallel, the voltage value of the first capacitor C1 in the conducting shunt module 30 is equal to the voltage value of the second capacitor C2. Therefore, the voltage value output from the source of the second switching device Q2 in the conducting shunt module 30 is equal to the voltage value output from the source of the third switching device Q3. The source of the second switching device Q2 in the conducting shunt module 30 can serve as a redundant structure for the source of the third switching device Q3. When the selective switching device Q5 is turned on and the third switching device Q3 is abnormally turned off, resulting in no output from the source of the third switching device Q3, the voltage output from the source of the second switching device Q2 can serve as the output voltage of the pixel circuit. Here, the voltage value of the first capacitor C1 is the same as the voltage value of the gate of the second switching device Q2, and the gate of the second switching device Q2 is the same as the voltage value of the first capacitor C1.

[0083] This application also provides an image sensor, including the pixel circuit described above.

[0084] The specific implementation process of the pixel circuit in the image sensor is similar to that of the aforementioned pixel circuit, and will not be repeated here.

[0085] Reference Figure 3 In some embodiments, the image sensor includes multiple pixel column modules A1, each pixel column module A1 including multiple pixel circuits A11, column amplifiers A12, and column analog-to-digital converters (ADCs) A13; in the pixel column module A1, the input terminal of the column amplifier A12 is electrically connected to the output terminal of each pixel circuit A11, and the output terminal of the column amplifier A12 is electrically connected to the input terminal of the column ADC A13; each pixel of the image is exposed and read out line by line, the voltage signal output from the output terminal of the pixel circuit A11 is amplified by the column amplifier A12, the column amplifier A12 outputs the amplified voltage signal, and the column ADC A13 converts the amplified voltage signal into a digital signal and outputs it.

[0086] In some embodiments, the pixel circuit in the image sensor includes a photodiode 10, an output module 20, and two shunt modules 30; each shunt module 30 includes a first switching device Q1, a second switching device Q2, and a first capacitor C1; the output module 20 includes a second capacitor C2 and an output submodule 21; the output submodule 21 includes a third switching device Q3 and a selection switching device Q5; each of the first switching device Q1, each of the second switching device Q2, the third switching device Q3, and the selection switching device Q5 is an NMOS transistor.

[0087] For example, refer to Figure 4 If the brightness of image B1 is greater than the brightness of image B2, and the brightness of image B2 is greater than the brightness of image B3, then the light intensity at point b1 in image B1 is greater than the light intensity at point b2 in image B2, and the light intensity at point b3 in image B3 is greater than the light intensity at point b3 in image B3.

[0088] In the image sensor, in the pixel circuit of the image at point b1 in the acquired image B1, both shunt modules 30 are turned on. The output voltage value of the pixel circuit for acquiring the image at point b1 is calculated using formula (5):

[0089]

[0090] Wherein, V1 is the output voltage value of the pixel circuit that acquires the image at b1, w is the amplification factor of the third switching device Q3, i1 is the current value of the total current converted by the photodiode 10 in the pixel circuit that acquires the image at b1, t is the exposure time, c1 is the capacitance value of the second capacitor C2, c2 is the capacitance value of the first capacitor C1 in the first shunt module 30, c3 is the capacitance value of the first capacitor C1 in the second shunt module 30, and K1 is the capacitance gain coefficient of the pixel circuit that acquires the image at b1.

[0091] In the image sensor, in the pixel circuit for acquiring the image at point b2 in image B2, the first shunt module 30 is turned on and the second shunt module 30 is turned off. The output voltage value of the pixel circuit for acquiring the image at point b2 is then calculated using formula (6):

[0092]

[0093] Wherein, V2 is the output voltage value of the pixel circuit that acquires the image at b2, w is the amplification factor of the third switching device Q3, i2 is the current value of the total current converted by the photodiode 10 in the pixel circuit that acquires the image at b2, t is the exposure time, c1 is the capacitance value of the second capacitor C2, c2 is the capacitance value of the first capacitor C1 in the first shunt module 30, and K2 is the capacitance gain coefficient of the pixel circuit that acquires the image at b2.

[0094] In the image sensor, in the pixel circuit for acquiring the image at point b3 in image B3, both the first shunt module 30 and the second shunt module 30 are disconnected. Therefore, the output voltage value of the pixel circuit for acquiring the image at point b3 is calculated using formula (7):

[0095]

[0096] Wherein, V3 is the output voltage value of the pixel circuit that acquires the image at b3, w is the amplification factor of the third switching device Q3, i3 is the current value of the total current converted by the photodiode 10 in the pixel circuit that acquires the image at b3, t is the exposure time, c1 is the capacitance value of the second capacitor C2, and K3 is the capacitance gain coefficient of the pixel circuit that acquires the image at b3.

[0097] Since the light intensity at b1 in image B1 is greater than the light intensity at b2 in image B2, and the light intensity at b3 in image B3 is greater than the light intensity at b3 in image B3, then i1 is greater than i2, i2 is greater than i3; K1 is less than K2, and K2 is less than K3.

[0098] Figure 5(a) is the relationship curve between the capacitor gain coefficient K of the pixel circuit and the illumination intensity I. The illumination intensity of image B1 is greater than the illumination intensity I2. The illumination intensity of image B2 is greater than the illumination intensity I1 and less than or equal to the illumination intensity I2. The illumination intensity of image B2 is less than or equal to the illumination intensity I1. L1 is the relationship curve between the capacitor gain coefficient K of the pixel circuit for acquiring image B3 and the illumination intensity I. L2 is the relationship curve between the capacitor gain coefficient K of the pixel circuit for acquiring image B2 and the illumination intensity I. L3 is the relationship curve between the capacitor gain coefficient K of the pixel circuit for acquiring image B1 and the illumination intensity I. The capacitor gain coefficient of the pixel circuit for acquiring image B1 is K1, the capacitor gain coefficient of the pixel circuit for acquiring image B2 is K2, and the capacitor gain coefficient of the pixel circuit for acquiring image B3 is K3.

[0099] Figure 5 (b) is a curve showing the relationship between the output voltage V of the pixel circuit and the illumination intensity I. The illumination intensity of image B1 is greater than that of illumination intensity I2, the illumination intensity of image B2 is greater than that of illumination intensity I1 and less than or equal to that of illumination intensity I2, and the illumination intensity of image B2 is less than or equal to that of illumination intensity I1. Curve L4 is a curve showing the relationship between the output voltage V of the pixel circuit and illumination intensity I provided in this embodiment of the application, and curve L5 is a curve showing the relationship between the output voltage V of the pixel circuit and illumination intensity I in the related art. In the interval between illumination intensity I1 and illumination intensity I4, the output voltage of the pixel circuit provided in this embodiment of the application is less than that of the pixel circuit in the related art. The output voltage value of the circuit, for example at a light intensity of I3, is less than the output voltage value Vy of the pixel circuit in the related art when the pixel circuit output voltage value Vx is less than that when the pixel circuit output voltage value ...

[0100] Therefore, the embodiments of this application can adaptively adjust the value of K to achieve high gain conversion in low illumination and automatically switch to low gain mode in high brightness environments, realizing dynamic adjustment function. That is, the lower the illumination, the higher the conversion gain and the more details in the dark areas; the higher the illumination, the lower the conversion gain and the more details in the bright areas are preserved. Thus, adaptive HDR function can be realized, and only one data reading is needed to preserve the details in both dark and bright areas, achieving high dynamic range imaging. Here, illumination is light intensity.

[0101] This application also provides a camera module, including the image sensor as described above.

[0102] The specific implementation process of the pixel circuit in the camera module is similar to that of the aforementioned pixel circuit, and will not be repeated here.

[0103] It should be noted that the camera compact module (CCM) is an important tool for acquiring visual information, and it is usually composed of a lens, an infrared cut-off filter, an image sensor, and a voice coil motor (VCM).

[0104] The image sensor is the core component of a CCM. There are two main types of image sensors: charge-coupled devices (CCDs) and complementary metal-oxide-semiconductor (CMOS) devices. Similar to film in a traditional camera, the core function of an image sensor is light sensing, that is, converting the detected light signal into a digital signal that is easy to transmit and process.

[0105] In some embodiments, the image sensor is a CMOS image sensor (CIS). Compared to CCD devices, CMOS has lower cost and power consumption, and offers more flexible readout methods. The CIS works as follows: light signals are sensed and converted into electrical signals by an array of photodiodes 10, which are then amplified and converted into a digital signal matrix by an analog-to-digital converter. This digital signal matrix represents the image data. The image data is then compressed and stored by an image signal processor (ISP).

[0106] The lens is another core component of the CCM (Chip-Mounted Module), its function being to converge light within the field of view onto the imaging plane. Its optical quality directly affects image quality. From the perspective of information transmission, the design level of the lens determines the transmission of high-frequency information reaching the image plane, thus directly affecting the imaging sharpness of the module. From the perspective of energy transmission, the lens structure determines the intensity and distribution of light reaching the CIS (CMOS Image Sensor), thus directly affecting the signal-to-noise ratio (SNR) performance of the CIS.

[0107] Based on the aforementioned devices, the CCM's workflow is as follows: First, the VCM drives the lens to focus, focusing the light carrying visual information through the lens, and filtering out the infrared band invisible to the human eye through an infrared cutoff filter, thus imaging the image onto the image sensor. The photodiode 10 converts the optical signal into an electrical signal, which is then amplified and converted from digital to analog to form a digital signal matrix, i.e., the raw image. This image is then processed by the ISP module, compressed, and stored in memory.

[0108] The dynamic range (DR) of an image refers to the ability of a CIS (CMOS Image Sensor) to simultaneously capture both highlights and shadows. Therefore, a larger full-well capacity (FWC) and lower readout noise are beneficial for achieving high dynamic range (HDR) imaging. When the dynamic range of the CIS is smaller than the dynamic range of the image scene, overexposure in bright areas or loss of detail in dark areas occurs, affecting image quality. Compared to related technologies, the pixel circuit provided in this application embodiment can prevent overexposure of pixel images, improving pixel image clarity and ensuring good image clarity in bright environments. Therefore, the image sensor in the camera module provided in this application embodiment has a better dynamic range, meaning the image sensor in the camera module provided in this application embodiment has a high dynamic range.

[0109] Reference Figure 6 This application also provides an electronic device 200, including a camera module 201 as described above.

[0110] The specific implementation of the camera module 201 in the electronic device 200 is similar to that described above, and will not be repeated here.

[0111] It should be noted that the electronic devices disclosed in this application can be smartphones, tablets, e-book readers, wearable devices (such as smartwatches), video game consoles, etc. This application does not limit the specific types of electronic devices.

[0112] In some related technologies, multiple frames are captured based on different exposure strategies, and then fused into a single high dynamic range image using algorithms. However, multi-frame fusion is only suitable for static environments and is prone to ghosting in complex and dynamic scenes, affecting image quality. Furthermore, during multi-frame shooting, the exposure time of the shortest frame is very short to preserve highlight details as much as possible, which can cause banding when shooting LED light sources.

[0113] In other related technologies, two frames of images are output for the same pixel, namely a low-gain image and a high-gain image. The low-gain image is a shorter exposure image, and the high-gain image is a longer exposure image. Finally, the two frames of images are fused into a high dynamic range image by a fusion algorithm. However, since the pixel signal needs to be read multiple times, the readout time and data volume increase, which in turn reduces the frame rate and increases power consumption.

[0114] In this embodiment, since the total current converted by the photodiode is equal to the sum of the first current obtained by the output module and the second current obtained by each conducting shunt module, the more conducting shunt modules there are, the smaller the first current obtained by the output module and the smaller the output voltage. Since the number of conducting shunt modules is positively correlated with the total current converted by the photodiode, the number of conducting shunt modules increases as the total current increases, resulting in a decrease in the first current obtained by the output module. Therefore, the increase in output voltage caused by the increase in total current can be reduced. Compared with related technologies, this avoids overly bright pixel images and improves the clarity of pixel images. In addition, this embodiment avoids ghosting in complex and changing scenes caused by the fusion of multi-frame image algorithms into high dynamic range images, and does not have the problems of reduced frame rate and increased power consumption caused by multiple readings of pixel signals. Furthermore, this embodiment can realize adaptive HDR function, and its readout circuit is simpler than traditional DCG technology.

[0115] In summary, in this embodiment, since the total current converted by the photodiode is equal to the sum of the first current received by the output module and the second current received by each conducting shunt module, the more conducting shunt modules there are, the smaller the first current received by the output module and the smaller the output voltage. Furthermore, since the number of conducting shunt modules is positively correlated with the total current converted by the photodiode, an increase in the total converted current leads to an increase in the number of conducting shunt modules, resulting in a decrease in the first current received by the output module. Therefore, the increase in output voltage caused by the increase in total current can be reduced. Compared with related technologies, this avoids overly bright pixel images and improves the clarity of pixel images.

[0116] Figure 7 This is a flowchart illustrating the steps of a pixel circuit control method provided in an embodiment of this application. The pixel circuit control method is executed by the electronic device described above. Figure 7 As shown, the method may include:

[0117] Step 101: Obtain the voltage value of the cathode of the photodiode.

[0118] The implementation method for this step is similar to the aforementioned process, and will not be repeated here.

[0119] Specifically, the voltage value of the cathode of the photodiode is acquired by the voltage acquisition module in the electronic device, and the voltage value of the cathode is obtained by the processor in the electronic device.

[0120] Step 202: Control the shunt module that matches the voltage value of the cathode to be turned on.

[0121] The number of shunt modules that match the voltage value of the cathode is negatively correlated with the voltage value of the cathode.

[0122] The implementation method for this step is similar to the aforementioned process, and will not be repeated here.

[0123] Specifically, the shunt module, which is matched to the voltage value of the cathode, is turned on by the processor in the electronic device.

[0124] It should be noted that when the conduction parameter of the first switching device in the shunt module is greater than the voltage value of the cathode of the photodiode, the voltage value of the shunt module and the cathode are matched. Therefore, in the shunt module that matches the voltage value of the cathode, the conduction parameter of the first switching device is greater than the voltage value of the cathode of the photodiode. That is, the difference between the voltage value of the control signal of the first switching device and the conduction threshold of the first switching device is greater than the voltage value of the cathode of the photodiode.

[0125] In this embodiment, by acquiring the voltage value of the cathode of the photodiode, and then controlling the shunt module matching the cathode voltage value to be turned on, since the number of shunt modules matching the cathode voltage value is negatively correlated with the cathode voltage value, and the cathode voltage value is negatively correlated with the total current value converted by the photodiode, when the total current value is increased, the cathode voltage value decreases, the number of shunt modules turned on increases, and the first shunt current acquired by the output module decreases. Therefore, the increase in output voltage caused by the increase in total current can be reduced. Compared with related technologies, this avoids the pixel image from being too bright and improves the image clarity of the pixel.

[0126] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0127] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a computer software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) and includes several instructions to cause a terminal (which may be a mobile phone, computer, server, or network device, etc.) to execute the methods described in the various embodiments of this application.

[0128] The embodiments of this application have been described above with reference to the accompanying drawings. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A pixel circuit, characterized in that, include: A photodiode (10), an output module (20), and at least two shunt modules (30); The photodiode (10) is electrically connected to the output module (20) and each shunt module (30); the total current converted by the photodiode (10) is equal to the sum of the first shunt current and the second shunt current; the first shunt current is the shunt current input by the photodiode (10) to the output module (20), and the second shunt current is the shunt current input by the shunt module (30) turned on by the photodiode (10); the output module (20) is used to convert the first shunt current into voltage and output it; The number of the shunt modules (30) that are turned on is positively correlated with the current value of the total current.

2. The pixel circuit according to claim 1, characterized in that, Each of the shunt modules (30) includes a first switching device (Q1), a second switching device (Q2), and a first capacitor (C1); The anode of the photodiode (10) is grounded, and the cathode of the photodiode (10) is electrically connected to the input terminal of the output module (20) and the first terminal of each of the first switching devices (Q1); In the current shunt module (30), the second end of the first switching device (Q1) is electrically connected to the first end of the first capacitor (C1), and the control end of the first switching device (Q1) is used to receive control signals; the first end of the second switching device (Q2) is used to be electrically connected to an external power supply, the second end of the second switching device (Q2) is grounded, and the control end of the second switching device (Q2) is electrically connected to the first end of the first capacitor (C1); the second end of the first capacitor (C1) is grounded.

3. The pixel circuit according to claim 2, characterized in that, Each first switching device (Q1) has a corresponding conduction parameter, which is the difference between the voltage value of the control signal of the first switching device (Q1) and the conduction threshold of the first switching device (Q1). At least a portion of the first switching devices (Q1) have different conduction parameters; When the voltage value of the cathode of the photodiode (10) is less than the conduction parameter of the first switching device (Q1), the first switching device (Q1) is turned on; when the voltage value of the cathode of the photodiode (10) is greater than the conduction parameter of the first switching device (Q1), the first switching device (Q1) is turned off.

4. The pixel circuit according to claim 2, characterized in that, The pixel circuit also includes a reset switch device (Q4); The first terminal of the reset switch device (Q4) is used to be electrically connected to the external power supply, the second terminal of the reset switch device (Q4) is electrically connected to the first terminal of each first switch device (Q1), and the control terminal of the reset switch device (Q4) is used to receive a reset signal.

5. The pixel circuit according to claim 4, characterized in that, The reset switch (Q4), the first switch (Q1), and the second switch (Q2) are all transistors.

6. The pixel circuit according to claim 1, characterized in that, The output module (20) includes a second capacitor (C2) and an output submodule (21); The anode of the photodiode (10) is grounded, and the cathode of the photodiode (10) is electrically connected to the first terminal of the second capacitor (C2) and the input terminal of each shunt module (30). The input terminal of the output submodule (21) is electrically connected to the first terminal of the second capacitor (C2), and the output submodule (21) is used to convert and output the voltage of the second capacitor (C2); The second terminal of the second capacitor (C2) is grounded.

7. The pixel circuit according to claim 6, characterized in that, The output submodule (21) includes a third switching device (Q3) and a selection switching device (Q5); The first terminal of the third switching device (Q3) is electrically connected to an external power supply, and the second terminal of the third switching device (Q3) is electrically connected to the first terminal of the selection switching device (Q5). The control terminal of the selection switch device (Q5) is used to receive the pixel row selection signal, and the second terminal of the selection switch device (Q5) is used to output the voltage after converting the voltage of the second capacitor (C2).

8. The pixel circuit according to claim 7, characterized in that, Both the third switching device (Q3) and the selection switching device (Q5) are transistors.

9. An image sensor, characterized in that, Includes the pixel circuit as described in any one of claims 1 to 8.

10. A camera module, characterized in that, Including the image sensor as described in claim 9.

11. An electronic device, characterized in that, Includes the camera module as described in claim 10.

12. A pixel circuit control method, executed by the electronic device as described in claim 11, characterized in that, The method includes: Obtain the voltage value of the cathode of the photodiode; The shunt module, whose voltage value matches that of the cathode, is turned on; The number of shunt modules that match the voltage value of the cathode is negatively correlated with the voltage value of the cathode.

Images