WO2023019394A1

WO2023019394A1 - Photosensitive apparatus and related electronic apparatus

Info

Publication number: WO2023019394A1
Application number: PCT/CN2021/112749
Authority: WO
Inventors: 江哲豪
Original assignee: 迪克创新科技有限公司
Priority date: 2021-08-16
Filing date: 2021-08-16
Publication date: 2023-02-23
Also published as: CN114207390A

Abstract

Disclosed in the present application are a photosensitive apparatus and a related electronic apparatus. The photosensitive apparatus sequentially operates in an initial stage, a coarse conversion stage and a fine conversion stage. The photosensitive apparatus comprises: a photodiode; an integration unit, which is used for performing an integration operation according to a charge generated by the photodiode, and correspondingly outputting an integration voltage; and a switch, which is coupled between the integration unit and a top plate sampling successive approximation analog-to-digital converter. The top plate sampling successive approximation analog-to-digital converter includes: a comparator, wherein a first input end thereof is coupled to a threshold voltage in the coarse conversion stage, and a second input end thereof is selectively coupled to the integration voltage by means of the switch; a capacitor array, which comprises a plurality of capacitors, which are all coupled to the second input end of the comparator by means of a top plate; and a successive approximation logic circuit.

Description

Photosensitive devices and related electronic devices

technical field

The present application relates to a sensor, in particular to a photosensitive device and related electronic devices.

Background technique

In the field of ambient light sensors, high dynamic range has always been one of the goals pursued by designers. In the past, high dynamic range was often achieved, but the sensitivity of the sensor was sacrificed. If the need to complete ambient light sensing within a very short exposure time is also added, the difficulty is even higher. Therefore, a new design is urgently needed in this field to replace the existing ambient light sensor method, so as to overcome all the above-mentioned problems.

Contents of the invention

One of the objectives of the present application is to disclose a photosensitive device and a related electronic device to solve the above problems.

An embodiment of the present application discloses a photosensitive device, the photosensitive device operates in an initial stage, a coarse conversion stage, and a fine conversion stage in sequence, and the photosensitive device includes: a photodiode coupled to a first reference voltage; an integral A unit, used to perform an integral operation according to the charge generated by the photodiode, and output an integrated voltage correspondingly; a switch, coupled between the integral unit and the successive approximation analog-to-digital converter sampled by the top plate; the A top-plate-sampled successive approximation analog-to-digital converter, comprising a comparator whose first input is coupled to a threshold voltage during the coarse conversion stage, and whose second input is passed through the The switch is selectively coupled to the integrated voltage, the second input terminal of the comparator is also coupled to a capacitor array, and the output terminal of the comparator is coupled to a successive approximation logic circuit; the capacitor array includes A plurality of capacitors are coupled to the second input terminal of the comparator through the top plate; the successive approximation logic circuit is used to control the bottom electrodes of the plurality of capacitors respectively according to the output signal of the comparator a plate selectively coupled to one of a plurality of voltages; a discharge unit coupled to the integration unit; and a controller configured to control the conduction of the switch so that the photosensitive device enters the rough switching stage, and controlling the switch to be non-conductive so that the photosensitive device enters the fine switching stage, wherein in the coarse switching stage, the controller controls the first input terminal of the comparator to be coupled to the threshold voltage, and when the output signal of the comparator indicates that the integration voltage is higher than the threshold voltage, the controller will add 1 to the coarse conversion digital code, and control the discharge unit to the integration unit A discharge operation is performed to lower the integrated voltage.

An embodiment of the present application discloses an electronic device, including: a display screen; and the above-mentioned photosensitive device, which is disposed under the display screen and senses ambient light passing through the display screen.

The photosensitive device and related electronic device of the present application can simultaneously take into account high dynamic range, high sensitivity and high resolution in the application of extremely short exposure time.

Description of drawings

FIG. 1 is a schematic diagram of an embodiment of a photosensitive device proposed in the present application operating in a rough switching stage.

FIG. 2 is a schematic diagram of an embodiment of the photosensitive device proposed in the present application operating in the fine switching stage.

FIG. 3 is an operation timing diagram of the photosensitive device of the present application.

FIG. 4 is an operation timing diagram of the photosensitive device of the present application at an initial stage.

FIG. 5 is an operation timing diagram of the photosensitive device of the present application during the discharge operation.

Detailed ways

The following disclosure provides various implementations or illustrations, which can be used to achieve different features of the disclosure. Specific examples of components and arrangements are described below to simplify the present disclosure. It will be appreciated that these descriptions are examples only and are not intended to limit the disclosure. For example, in the description below, forming a first feature on or over a second feature may include some embodiments wherein the first and second features are in direct contact with each other; and may also include In some embodiments, additional components are formed between the first and second features, such that the first and second features may not be in direct contact. In addition, this disclosure may reuse reference symbols and/or labels in various embodiments. Such repetition is for the sake of brevity and clarity, and does not in itself represent a relationship between the different embodiments and/or configurations discussed.

Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the application are approximations, the relative numerical values set forth in the specific examples are reported here as precisely as possible. Any numerical value, however, inherently inherently contain standard deviations resulting from their individual testing methodology. As used herein, "about" generally means that the actual value is within plus or minus 10%, 5%, 1%, or 0.5% of a particular value or range. Alternatively, the term "about" means that the actual value falls within an acceptable standard error of the mean, as considered by one of ordinary skill in the art to which this application pertains. It should be understood that, except for the experimental examples, or unless otherwise clearly stated, all ranges, quantities, numerical values and percentages used herein (for example, to describe the amount of material used, the length of time, temperature, operating conditions, ratios of quantities and others) similar) are modified by "about". Therefore, unless otherwise stated to the contrary, the numerical parameters disclosed in this specification and the appended patent claims are approximate values and may be changed as required. At least these numerical parameters should be understood as the value obtained by applying the normal rounding method to the indicated effective digits. Herein, numerical ranges are expressed as being from one endpoint to another endpoint or between two endpoints; unless otherwise stated, the numerical ranges stated herein are inclusive of the endpoints.

FIG. 1 is a schematic diagram of an embodiment of a photosensitive device proposed in the present application. The photosensitive device 100 in FIG. 1 can be used as an ambient light sensor to detect the charge accumulated by the photodiode 102 in a period of time (which is positively related to the average illuminance of the period of time), and output as a rough converted digital code DO_c And fine conversion digital code DO_f.

The photosensitive device 100 can be used to sense ambient light. For example, it can be installed in an electronic device as a proximity sensor. The present application proposes that the photosensitive device 100 be arranged under the display screen of the electronic device to form an under-screen proximity sensor. Sensing is performed to reduce the bezel width of the non-display area of the electronic device. In this application, in order to prevent the backlight of the display screen from interfering with the sensing of ambient light by the photosensitive device 100, the photosensitive device 100 only performs sensing during the blanking period when the backlight of the display screen does not emit light. However, the blanking period is extremely short, and the display screen Generally speaking, the light transmittance to ambient light is extremely low, and in the case of an organic light emitting diode display, it is only about 2% to 4%.

In order to complete ambient light detection with high sensitivity and high dynamic range in a very short time, the photosensitive device 100 in FIG. 1 divides the sensing process into three stages: initial stage, coarse conversion stage and fine conversion stage . For an under-display proximity sensor application, the coarse transition phase must be during the blanking period so as not to be disturbed by the display backlight, but the initial phase and the fine transition phase are not disturbed by the display backlight. Jamming, may be performed outside the blanking period.

The anode of the photodiode 102 in FIG. 1 is coupled to the first reference voltage V1 , and the cathode is coupled to the integration unit 104 . The integrating unit 104 is used for performing an integrating operation according to the charge generated by the photodiode 102 irradiated by light, and correspondingly outputs the integrated voltage Vo. Because the integrating unit 104 cannot integrate forever, the integrated voltage Vo will inevitably be saturated if it keeps increasing. Therefore, the photosensitive device 100 of the present application uses the comparator 1062 to determine whether the integrated voltage Vo is higher than the threshold voltage Vth. If the integrated voltage Vo is higher than the threshold voltage Vth, the controller 110 is notified to add 1 to the coarse conversion digital code DO_c, and the controller 110 uses the discharge unit 108 to discharge the integration unit 104 to pull down the integration voltage Vo, so that the integration unit 104 can In the coarse conversion stage, the charge generated by the photodiode 102 after being irradiated by light is continuously integrated.

The stronger the light, the faster the rising speed of the integrated voltage Vo. Therefore, under the fixed time length of the rough conversion phase, the number of times the threshold voltage Vth is exceeded is also more. When the rough conversion phase ends, the rough conversion digital The code DO_c is also naturally larger. But relatively, the weaker the light is, the smaller the coarse conversion digital code DO_c is when the coarse conversion phase ends.

It can be understood that the controller 110 will be triggered to add 1 to the coarse converted digital code DO_c only when the integral voltage Vo exceeds the threshold voltage Vth. When the ambient light is very low, it is possible that the charges generated by the photodiode 102 during the entire coarse conversion stage cannot make the integrated voltage Vo exceed the threshold voltage Vth, so that the sensitivity is limited by the threshold voltage Vth. However, if the threshold voltage Vth is set lower, the probability of the discharge operation will inevitably increase. Since the discharge operation may affect the accuracy of the integral operation, too frequent discharge operations are critical to maintaining the accuracy of the photosensitive device 100. is unfavorable. Therefore, the present application also utilizes the successive approximation analog-to-digital converter 106 to convert the remaining integrated voltage Vo, which is less than the threshold voltage Vth at the end of the coarse conversion phase, into a fine conversion digital code DO_f in the fine conversion phase. The sensitivity and resolution of the photosensitive device 100 are improved.

Specifically, the successive approximation analog-to-digital converter 106 of the present application is a top-plate sampling architecture as shown in FIG. 1 and FIG. At the second input terminal of 1062, a plurality of capacitors (capacitance values C, C, 2C, ..., 2N-1C) included in the capacitor array 1066 all pass through the top pole The plate is coupled to the second input of the comparator 1062 . The advantage of this is that when the photosensitive device 100 is in the rough conversion stage and the switch 108 is turned on, the integral voltage Vo and the threshold voltage Vth are respectively directly coupled to the two input terminals of the comparator 1062, so that the successive approximation analog-to-digital converter 106 becomes a simple comparator, and in fact the capacitor array 1068 will continuously sample; therefore, when the photosensitive device 100 enters the fine conversion stage from the coarse conversion stage, the switch 108 is turned off, and the successive approximation analog-to-digital converter 106 can concentrate on performing the successive approximation analog-to-digital conversion on the integral voltage Vo sampled by the capacitor array 1068 when entering the fine conversion stage from the coarse conversion stage, and the controller 110 will convert the successive approximation analog-to-digital converter 106 in The output signal Ss output by the fine conversion stage is converted into a fine conversion digital code DO_f.

Further details regarding the operation of the successive approximation analog-to-digital converter 106 include the following. After entering the fine conversion stage, the first input terminal of the comparator 1062 of the successive approximation analog-to-digital converter 106 sampled by the top plate can be originally coupled to the threshold voltage Vth through the control signal Sm generated by the controller 110 Switched to be coupled to the second reference voltage V2. The successive approximation logic circuit 1064 respectively controls the bottom plates of the multiple capacitors of the capacitor array 1066 to selectively couple to one of multiple voltages (such as the first reference voltage V1, the second reference voltage V1, and the second reference voltage) according to the output signal Ss of the comparator 1062. Voltage V2, the third reference voltage V3), wherein the second reference voltage may be between the first reference voltage V1 and the third reference voltage V3.

In some embodiments, a non-top-plate sampling architecture SAR ADC, for example, a bottom-plate sampling architecture SAR ADC may also be used as the SAR ADC 106 . However, because the input terminal of the comparator of the successive approximation analog-to-digital converter 106 using the bottom plate sampling architecture will not be directly coupled to the integrated voltage Vo through the switch 108, another comparator needs to be additionally added as the coarse conversion. stage used.

Next, details of the integrating unit 104 will be described. The integrating unit 104 includes an operational amplifier 1042 , an integrating capacitor Cint, a switch 1044 , a switch 1046 and a switch 1048 . The operational amplifier 1042 includes a positive input terminal, a negative input terminal and an output terminal, the negative input terminal is coupled to the photodiode 102 ; the positive input terminal is coupled to the fourth reference voltage V4. One terminal of the integrating capacitor Cint is coupled to the negative input terminal of the operational amplifier 1042 . The switch 1044 is coupled between the negative terminal of the operational amplifier 1042 and the output terminal; the switch 1046 is coupled between the other end of the integrating capacitor Cint and the output terminal of the operational amplifier 1042; the switch 1048 is coupled to the integral between the other end of the capacitor Cint and the reset voltage Vrst.

Please also refer to FIG. 4 , at the time T0 of the initial stage before the rough conversion stage, the controller 110 controls the

switches

1044 , 1046 and 1048 correspondingly through the control signals Srst1 , Srst2 and Srst3 , so that the switch 1044 is turned off. , the switch 1046 is turned on and the switch 1048 is turned off. Then the controller 110 turns off the switch 1046 at time T01, and turns on the switch 1044 and the switch 1048 at time T02 so that the integrated voltage Vo is reset to the reset voltage Vrst, and then the controller 110 turns off the switch 1044 and the switch 1048 at time T03. The switch 1048 is turned off, and the switch 1044 is turned on again at time T04 to complete the reset of the integration unit 104 .

Referring to FIG. 3, it can be seen that the integrated voltage Vo is reset to the reset voltage Vrst during the initial stage, then enters the coarse switching stage at time T1, and enters the fine switching stage from the coarse switching stage at time T8. transition phase, and ends the fine transition phase at time T9. In this embodiment, the length of time T1 to T8 is a preset time length, which, as mentioned above, needs to be shorter than the blanking period of the matched display screen. It can also be observed from FIG. 3 that when the integral voltage Vo is higher than the threshold voltage Vth, the output signal Ss of the comparator 1062 will be triggered, so that the controller 110 controls the discharge unit 108 to discharge the integral unit 104 to accumulate the integral capacitance Cint The charges of are moved to the discharge unit 108 to reduce the integrated voltage Vo. In this embodiment, the time length of the discharge operation is a preset time length, that is, the time length of time T2 to T3 is the same as the time length of time T4 to T5 and the time length of time T6 to T7. Details about the discharge unit 108 will be described below.

Please refer to FIG. 1 again, the discharge unit 108 includes a discharge capacitor Cd, the first end of the discharge capacitor Cd is coupled to the photodiode 102, the second end of the discharge capacitor Cd is selectively coupled to the discharge reference voltage Vrp through the switch 1082, and the discharge capacitor The second terminal of Cd is also selectively coupled to the first terminal of the discharge capacitor Cd through a switch 1084 .

Please refer to FIG. 5 together. During the non-discharging operation, the controller 110 controls the

switches

1084 and 1082 correspondingly through the control signals Sd1 and Sd2 , so that the switch 1084 is turned on and the switch 1082 is turned off. When entering the discharge operation, for example, between time T2 and T3, the controller 110 will turn off the switch 1084 at time T21, and turn on the switch 1082 at time T22 to absorb the charge accumulated in the integration capacitor Cint to the discharge capacitor Cd is equivalent to discharging the integral capacitor Cint, thereby reducing the integral voltage Vo. Then the controller 110 turns off the switch 1082 at time T23 and turns on the switch 1084 again at time T24 to complete the discharging operation.

It should be noted that the specific implementation of the discharge unit 108 of the present application is not limited to the embodiments shown in FIG. 1 and FIG. 2 , as long as the integration voltage Vo of the integration unit 104 can be reduced through the control of the controller 110, any method can be applied. in the photosensitive device 100 . In addition, the present application does not limit the implementation manner of the controller 110 . For example, the controller 110 can be realized by using a processor together with software or firmware, or by using a specific circuit in pure hardware.

The integrating capacitor Cint in the integrating unit 104 of the photosensitive device 100 of the present application may have a smaller value to increase the gain of the integrating unit 104 , so as to increase the efficiency of the rough conversion and increase the sensitivity of the photosensitive device 100 . At the same time, the capacitive array 1066 of the successive approximation analog-to-digital converter 106 sampled by the top plate can be enlarged to improve the resolution of the fine conversion. In this way, even if the photosensitive device 100 is disposed under the display screen, it can simultaneously take into account high dynamic range, high sensitivity and high resolution with a very short exposure time.

The foregoing description briefly sets forth features of certain embodiments of the present application, so that those skilled in the art to which the present application pertains can more fully understand the various aspects of the present disclosure. Those with ordinary knowledge in the technical field to which this application belongs should understand that they can easily use the disclosure as a basis to design or modify other processes and structures to achieve the same purpose and/or achieve the same advantages. Those with ordinary knowledge in the technical field of the present application should understand that these equivalent embodiments still belong to the spirit and scope of the present disclosure, and various changes, substitutions and changes can be made without departing from the spirit of the present disclosure. with range.

Claims

A photosensitive device, characterized in that the photosensitive device operates in an initial stage, a coarse conversion stage, and a fine conversion stage in sequence, and the photosensitive device includes:

a photodiode coupled to a first reference voltage;

an integration unit, used to perform an integration operation according to the charge generated by the photodiode, and output an integration voltage correspondingly;

a switch, coupled between the integration unit and the successive approximation analog-to-digital converter sampled by the top plate;

The successive approximation analog-to-digital converter of the top plate sampling includes:

a comparator having a first input coupled to a threshold voltage during the coarse switching phase, a second input of the comparator selectively coupled to the integrated voltage through the switch, the The second input terminal of the comparator is also coupled to the capacitor array, and the output terminal of the comparator is coupled to the successive approximation logic circuit;

The capacitor array, including a plurality of capacitors are coupled to the second input terminal of the comparator through the top plate;

The successive approximation logic circuit is used to respectively control the bottom plates of the plurality of capacitors to be selectively coupled to one of the plurality of voltages according to the output signal of the comparator;

a discharge unit coupled to the integration unit; and

a controller, configured to control the switch to be turned on so that the photosensitive device enters the coarse switching stage, and control the switch to be non-conductive to make the photosensitive device enter the fine switching stage, wherein in the coarse In a conversion stage, the controller controls the first input terminal of the comparator to be coupled to the threshold voltage, and when the output signal of the comparator indicates that the integrated voltage is higher than the threshold voltage , the controller accumulates the coarse conversion digital code by 1, and controls the discharge unit to perform a discharge operation on the integration unit, so as to reduce the integration voltage.
The photosensitive device according to claim 1, wherein the integrating unit comprises:

an operational amplifier comprising a positive input, a negative input, and an output, the negative input being coupled to the photodiode; and

The integrating capacitor is coupled between the negative input terminal and the output terminal of the operational amplifier.
The photosensitive device according to claim 2, wherein when the controller controls the discharge unit to perform the discharge operation on the integration unit, the charge accumulated in the integration capacitor moves to the discharge unit.
The photosensitive device according to claim 3, wherein the discharge unit comprises a discharge capacitor, a first end of the discharge capacitor is coupled to the photodiode, and a second end of the discharge capacitor is selectively coupled to the photodiode. to a discharge reference voltage, and the second terminal of the discharge capacitor is also selectively coupled to the first terminal of the discharge capacitor.
The light-sensing device according to claim 4, wherein the controller controls the switch to be turned on so that the light-sensing device enters the rough switching stage and maintains the first preset time length, and then controls the switch is non-conductive to enter the photosensitive device into the fine switching phase.
The photosensitive device according to claim 4, wherein when the output signal of the comparator indicates that the integrated voltage is higher than the threshold voltage, the controller controls the discharge unit to The unit performs the discharging operation and maintains it for a second preset time period.
The photosensitive device according to claim 4, wherein during the rough conversion stage and the controller does not control the discharge unit to perform the discharge operation on the integration unit, the controller controls the The second end of the discharge capacitor is coupled to the first end of the discharge capacitor and disconnected from the discharge reference voltage.
The photosensitive device according to claim 4, wherein during the rough conversion stage and the controller controls the discharge unit to perform the discharge operation on the integration unit, the controller controls the discharge The second end of the capacitor is coupled to the discharge reference voltage and disconnected from the first end of the discharge capacitor.
The photosensitive device according to claim 2, characterized in that:

a first terminal of the integrating capacitor is coupled to the negative input terminal of the operational amplifier, and the first terminal of the integrating capacitor is also selectively coupled to the output terminal of the operational amplifier; as well as

A second terminal of the integrating capacitor is selectively coupled to the output terminal of the operational amplifier, and the second terminal of the integrating capacitor is also selectively coupled to the reset voltage.
The photosensitive device according to claim 9, characterized in that, in the coarse switching stage, the first terminal of the integrating capacitor is disconnected from the output terminal of the operational amplifier, and the output terminal of the integrating capacitor is The second terminal is coupled to the output terminal of the operational amplifier and disconnected from the reset voltage.
The photosensitive device according to claim 9, wherein at an initial stage before the coarse conversion stage, the first terminal of the integrating capacitor is coupled to the output terminal of the operational amplifier, and the The second terminal of the integrating capacitor is coupled to the reset voltage and disconnected from the output terminal of the operational amplifier.
The photosensitive device according to claim 1, wherein the successive approximation logic circuit respectively controls the bottom plates of the plurality of capacitors to selectively couple to each other according to the output signal of the comparator in the fine conversion stage. to the first reference voltage, the second reference voltage, or the third reference voltage to convert the integrated voltage when the photosensitive device enters the fine conversion phase from the coarse conversion phase into a digital signal as a fine conversion A digital code, wherein the coarse conversion character code accumulated in the coarse conversion stage plus the fine conversion digital code obtained in the fine conversion stage is positively related to the average illuminance in the coarse conversion stage.
The photosensitive device according to claim 12, wherein the controller controls the first input terminal of the comparator to be coupled to the second reference voltage during the fine switching phase.
An electronic device, characterized in that it comprises:

display screen; and

The photosensitive device according to any one of claims 1 to 13, which is arranged under the display screen and senses ambient light passing through the display screen.
The electronic device as claimed in claim 14, wherein the first preset time length is shorter than a blanking period of the display screen.