Optical sensing pixel circuit and driving method thereof, sensor and display panel

Abstract

The present disclosure discloses an optical sensing pixel circuit and a driving method thereof, a sensor and a display panel. The optical sensing pixel circuit includes: a photodiode, which is used to detect external light signals and convert the light signals into electrical signals; an amplifier circuit, which is electrically connected to the photodiode and is used to amplify the electrical signals into detectable large current signals; a constant current bias circuit, which is electrically connected to the output end of the amplifier circuit and is used to provide a constant current to the amplifier circuit so as to set a static operating point of the same current as the constant current for the amplifier circuit, so that the amplifier circuit amplifies the electrical signal based on the static operating point.

Description

Technical Field

[0001] The present disclosure relates to the field of fingerprints, and in particular to an optical sensing pixel circuit and a driving method thereof, a sensor and a display panel. Background Art

[0002] With the widespread application of OLED displays, integrating sensors on OLED displays has become a general trend.

[0003] Integrating sensors on OLED displays can be achieved using thin-film TFT technology, which can reduce the cost of sensors and the size and weight of these devices. For example, integrating a fingerprint sensor on an OLED display requires making a photoelectric sensor inside the display, and then reading the data of the photoelectric sensor in the light and dark states through an external circuit to obtain fingerprint information.

[0004] However, the current output by the optical sensor is very weak, usually between 0.1 and 10 pA, which makes it difficult for the fingerprint acquisition circuit to directly read the weak current output by the optical sensor, resulting in the inability to accurately obtain fingerprint information. Summary of the invention

[0005] The embodiments of the present disclosure provide an optical sensing pixel circuit and a driving method thereof, a sensor and a display panel, so as to solve the above-mentioned technical problems existing in the prior art.

[0006] In a first aspect, in order to solve the above technical problems, an embodiment of the present disclosure provides an optical sensing pixel circuit, which includes:

[0007] A photodiode, one end of which is electrically connected to a constant voltage terminal, and the photodiode is used to detect external light signals and convert the light signals into electrical signals; wherein the electrical signals are weak and difficult to be detected;

[0008] an amplifier circuit, electrically connected to the other end of the photodiode, the amplifier circuit being used to amplify the electrical signal into a detectable large current signal;

[0009] A constant current bias circuit is electrically connected to the output end of the amplifier circuit and is used to provide a constant current to the amplifier circuit so as to set a static operating point for the amplifier circuit that is the same as the constant current, so that the amplifier circuit amplifies the electrical signal based on the static operating point.

[0010] In a possible implementation manner, the constant current bias circuit includes:

[0011] A constant current source, used for providing the constant current;

[0012] The first switch transistor is connected between the constant current source and the output end of the amplifier circuit, and is used for providing the constant current to the amplifier circuit in the bias setting stage.

[0013] In a possible implementation manner, the amplifier circuit includes:

[0014] A driving transistor, wherein a first terminal of the driving transistor is electrically connected to the constant voltage terminal, a second terminal of the driving transistor serves as an output terminal of the amplifier circuit, and a control terminal of the driving transistor is electrically connected to an output terminal of the photodiode;

[0015] A storage capacitor, one end of which is electrically connected to the constant voltage end, and a second end of which is electrically connected to the control end of the driving transistor, for storing a first voltage of the driving transistor when the output current of the driving transistor is the constant current and receiving the electrical signal; wherein the first voltage is a voltage difference between the control end of the driving transistor and the first end of the driving transistor, and the first voltage includes a threshold voltage of the driving transistor;

[0016] A second switching transistor, wherein the first end of the second switching transistor is electrically connected to the control end of the driving transistor, the second end of the second switching transistor is electrically connected to the second end of the driving transistor, and the second switching transistor is turned on during the bias setting phase, so that the driving transistor stores the first voltage in the storage capacitor under the action of the constant current, and the driving transistor outputs the constant current in an amplified state.

[0017] In a possible implementation manner, the constant current is greater than 10 times the leakage current of the photodiode.

[0018] In a possible implementation manner, the optical sensing pixel circuit further includes:

[0019] A current detection circuit is electrically connected to the output end of the amplifier circuit, and is used to detect the large current signal during the signal reading phase and convert it into a corresponding voltage drop signal.

[0020] In a possible implementation manner, the current detection circuit includes:

[0021] a third switch transistor, a first end of the third switch transistor being electrically connected to the output end of the amplifier circuit, and the third switch transistor being turned on during the signal reading phase to receive the large current signal;

[0022] An integration circuit, wherein the input end of the integration circuit is electrically connected to the second end of the third switching transistor, the output end of the integration circuit serves as the output end of the current detection circuit, and the integration circuit is used to reset the integration circuit after receiving a reset signal at the reset end of the integration circuit, and integrate the large current signal after resetting to generate the voltage drop signal.

[0023] In a possible implementation manner, the integration circuit includes:

[0024] An integrator, wherein a first input terminal of the integrator serves as an input terminal of the integrator circuit, an output terminal of the integrator serves as an output terminal of the integrator circuit, and a second input terminal of the integrator is connected to a reference voltage;

[0025] An integrating capacitor, wherein a first end of the integrating capacitor is electrically connected to a first input end of the integrating operator, and a second end of the integrating capacitor is electrically connected to an output end of the integrating operator, and is used to integrate the large current signal and generate the voltage drop signal on the integrating capacitor;

[0026] A reset device, wherein the first end of the reset device is electrically connected to the first input end of the integrator, the second end of the reset device is electrically connected to the output end of the integrator, and the reset device is used to reset the integral capacitor and the output end of the amplifier circuit.

[0027] In a second aspect, an embodiment of the present disclosure provides a driving method based on the optical sensing pixel circuit as described in the first aspect, comprising:

[0028] In the bias setting stage, the first switch transistor and the second switch transistor are turned on, so that the constant current bias circuit provides a constant current for the amplifier circuit, so as to set a first voltage corresponding to the output of the constant current for the driving transistor of the amplifier circuit, and save it in the storage capacitor; wherein the first voltage is a voltage difference between the control terminal of the driving transistor and the first terminal of the driving transistor, and the first voltage includes a threshold voltage of the driving transistor;

[0029] In the signal reading stage, the first switch transistor and the second switch transistor are turned off, and the third switch transistor is turned on. At the same time, the integration circuit is reset, and then the third switch transistor is disconnected, so that the integration circuit starts to integrate the current signal at the output end of the amplifier circuit, generates a voltage change on the integration capacitor, and calculates the current output by the amplifier circuit based on the integration time and the voltage change.

[0030] In a third aspect, an embodiment of the present disclosure provides a sensor comprising optical sensing pixel circuits as described in the first aspect arranged in an array.

[0031] In a possible implementation, optical sensing pixel circuits located in the same column share a constant current bias circuit.

[0032] In a possible implementation manner, the sensor includes a detection area and a non-detection area surrounding the detection area;

[0033] A plurality of photoelectric detection circuits are arranged in an array in the detection area;

[0034] The constant current bias circuit is disposed in the non-detection area.

[0035] In a fourth aspect, an embodiment of the present disclosure provides a display panel, comprising the sensor as described in the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 A schematic diagram of the structure of an optical sensing pixel circuit provided in an embodiment of the present disclosure Figure 1 ;

[0037] Figure 2 A schematic diagram of the structure of a constant current bias circuit provided in an embodiment of the present disclosure;

[0038] Figure 3 A schematic diagram of the structure of an amplifier circuit provided in an embodiment of the present disclosure;

[0039] Figure 4 A schematic diagram of the structure of an optical sensing pixel circuit provided in an embodiment of the present disclosure Figure 2 ;

[0040] Figure 5 A schematic diagram of the structure of a current detection circuit provided in an embodiment of the present disclosure;

[0041] Figure 6 A schematic diagram of the structure of an integration circuit provided in an embodiment of the present disclosure;

[0042] Figure 7 A schematic diagram of the structure of the photoelectric sensor pixel circuit provided in the embodiment of the present disclosure Figure 3 ;

[0043] Figure 8 A control timing diagram of a photoelectric sensing pixel circuit provided in an embodiment of the present disclosure;

[0044] Fig. 9 A driving method for a photoelectric sensing pixel circuit provided in an embodiment of the present disclosure;

[0045] Fig.10 A schematic diagram of the structure of the sensor provided in the embodiment of the present disclosure Figure 1 ;

[0046] Fig.11A schematic diagram of the structure of the sensor provided in the embodiment of the present disclosure Figure 2 . DETAILED DESCRIPTION

[0047] The embodiments of the present disclosure provide a photoelectric sensing pixel circuit and a driving method thereof, a sensor and a display panel, which are used to solve the above-mentioned technical problems existing in the prior art.

[0048] Knowledge related to this disclosure:

[0049] The static operating point refers to the time when the AC input signal in the transistor amplifier circuit is zero and the circuit is in the DC operating state. The values ​​of these currents and voltages can be represented by a certain point on the BJT characteristic curve of the transistor, which is customarily called the static operating point Q.

[0050] In order to make the above-mentioned purposes, features and advantages of the present disclosure more obvious and easy to understand, the present disclosure will be further described below with reference to the accompanying drawings and examples. However, the example embodiments can be implemented in various forms and should not be understood as being limited to the embodiments described herein; on the contrary, these embodiments are provided to make the present disclosure more comprehensive and complete, and to fully convey the concepts of the example embodiments to those skilled in the art. The same figure marks in the figures represent the same or similar structures, and thus their repeated descriptions will be omitted. The words expressing position and direction described in the present disclosure are all explained using the accompanying drawings as examples, but changes can be made as needed, and the changes made are all included in the scope of protection of the present disclosure. The drawings of the present disclosure are only used to illustrate the relative position relationship and do not represent the true proportion.

[0051] It should be noted that specific details are described in the following description to facilitate a full understanding of the present disclosure. However, the present disclosure can be implemented in a variety of other ways different from those described herein, and those skilled in the art can make similar generalizations without violating the connotation of the present disclosure. Therefore, the present disclosure is not limited to the specific implementation methods disclosed below. The subsequent description of the specification is a preferred implementation method for implementing the present disclosure, but the description is for the purpose of illustrating the general principles of the present disclosure and is not intended to limit the scope of the present disclosure. The scope of protection of the present disclosure shall be determined by the definition of the attached claims.

[0052] In conjunction with the accompanying drawings, an optical sensing pixel circuit and its acquisition method, a sensor and a display panel provided by an embodiment of the present disclosure are described in detail below.

[0053] See also Figure 1 A schematic diagram of the structure of an optical sensing pixel circuit provided in an embodiment of the present disclosure Figure 1 , the optical sensing pixel circuit comprises:

[0054] A photodiode 1, one end of which is electrically connected to a constant voltage terminal VDD. The photodiode 1 is used to detect external optical signals and convert the optical signals into electrical signals; wherein the electrical signals are weak and difficult to be detected.

[0055] The amplifier circuit 2 is electrically connected to the photodiode 1 and is used to amplify the difficult-to-detect electrical signal output by the photodiode 1 into a detectable large current signal.

[0056] The constant current bias circuit 3 is electrically connected to the output end of the amplifier circuit 2, and is used to provide a constant current to the amplifier circuit 2, so as to set a static operating point for the amplifier circuit 2 with the same current as the constant current, so that the amplifier circuit 2 amplifies the electrical signal output by the photodiode 1 based on the static operating point.

[0057] exist Figure 1 The power supply terminal of the middle amplifier circuit 2 is also electrically connected to the constant voltage terminal VDD.

[0058] A constant current is provided to the amplifier circuit 2 through the constant current bias current 3, and the amplifier circuit 2 is set at a static operating point with the same current as the constant current, so that the amplifier circuit 2 amplifies the weak electrical signal that is not easily detected output by the photodiode 1 into a detectable large current signal based on the static operating point.

[0059] See also Figure 2 , is a schematic diagram of the structure of the constant current bias circuit provided in an embodiment of the present disclosure.

[0060] The constant current bias circuit 3 comprises:

[0061] The constant current source 31 is used to provide a constant current I bias ;

[0062] The first switch transistor 32 is connected between the constant current source 31 and the amplifier circuit 2, and is used to provide a constant current I to the amplifier circuit 2 during the bias setting stage. bias The other end of the constant current source 31 is grounded. The first switch transistor 32 can be an N-type transistor or a P-type transistor. Figure 2 In the figure, an N-type transistor is used as an example.

[0063] A possible implementation method is to use a constant current I bias Greater than 10 times the leakage current of photodiode 1.

[0064] By letting the constant current I bias The leakage current of the photodiode 1 is greater than 10 times, and the output electrical signal of the photodiode 1 can be determined according to the large current signal read from the output end of the amplifier circuit 2 during the signal reading stage.

[0065] See also Figure 3, which is a schematic diagram of the structure of the amplifier circuit provided in an embodiment of the present disclosure.

[0066] The amplifier circuit 2 comprises:

[0067] A driving transistor 21, wherein a first terminal 21a of the driving transistor 21 is electrically connected to the constant voltage terminal VDD, a second terminal 21b of the driving transistor 21 serves as an output terminal of the amplifier circuit 2, and a control terminal 21g of the driving transistor 21 is electrically connected to an output terminal of the photodiode 1;

[0068] A storage capacitor 22, one end of the storage capacitor 22 is electrically connected to the constant voltage terminal VDD, and the second end of the storage capacitor 22 is electrically connected to the control terminal 21g of the driving transistor 21, and is used to store a first voltage of the driving transistor 21 when the output current of the driving transistor 21 is a constant current and receive an electrical signal; wherein the first voltage is a voltage difference between the control terminal 21g of the driving transistor 21 and the first terminal 21a of the driving transistor 21, and the first voltage includes a threshold voltage of the driving transistor 21;

[0069] The second switch transistor 23, the first end 23a of the second switch transistor 23 is electrically connected to the output end of the photodiode 1, the second end 23b of the second switch transistor 23 is electrically connected to the second end 21b of the driving transistor 21, the second switch transistor 23 is turned on in the bias setting stage (the second switch transistor 23 is turned on when receiving the second control signal) to drive the transistor 21, so that the driving transistor 21 is at a constant current I bias The first voltage is stored in the storage capacitor 22 under the action of the first voltage, so that the driving transistor 21 outputs a constant current I in the amplified state. bias .

[0070] After the control terminal 23g of the second switch transistor 23 receives the second control signal (i.e., in the bias setting stage), the driving transistor 21 and the second switch transistor 23 are both in the on state (at the same time, the first switch transistor 32 also receives the first control signal and is in the on state), so that the constant current source 31 and the driving transistor 21 are connected in series. At this time, the current output by the driving transistor 21 is a constant current I bias That is, at this time, a conduction current of I is established at the control terminal 21g of the driving transistor 21. bias The bias gate voltage V bias , at the bias voltage V bias The threshold voltage V of the driving transistor is included th .

[0071] According to the driving characteristics of the transistor:

[0072] V GS =V DD -V bias (1);

[0073] I bias =β(V GS -V th ) 2 =β(V DD -V bias -V th ) 2 (2);

[0074] According to the formula, we can get:

[0075] Among them, V GS is a first voltage between the control terminal 21g and the second terminal 21b of the driving transistor 21, V DD The voltage provided by the constant voltage terminal, V th is the threshold voltage of the driving transistor 21, β is the gain of the driving transistor 21, I bias is the on-state current of the driving transistor 21 (that is, the constant current I provided by the constant current source 21). bias ). It can be seen from formula (2) that the bias voltage V bias The threshold voltage V of the driving transistor is included th .

[0076] It should be noted that the driving transistor 21 and the second switch transistor 23 are transistors with the same polarity, and they can be N-type transistors or P-type transistors, and there is no specific limitation on them. Figure 4 In the example, they are P-type transistors.

[0077] See also Figure 4 A schematic diagram of the structure of an optical sensing pixel circuit provided in an embodiment of the present disclosure Figure 2 The optical sensing pixel circuit also includes: a current detection circuit 4, which is electrically connected to the output end of the amplifier circuit 2, and is used to detect the large current signal output by the amplifier circuit 2 and convert it into a corresponding voltage drop signal.

[0078] See also Figure 5 A schematic diagram of the structure of a current detection circuit provided in an embodiment of the present disclosure.

[0079] The current detection circuit 4 comprises:

[0080] The third switch transistor 41, the first end 41a of the third switch transistor 41 is electrically connected to the output end of the amplifier circuit 2, the third switch transistor 41 is turned on in the signal reading stage (the third switch transistor 41 is turned on when receiving the third control signal), and is used to receive the large current signal output by the amplifier circuit 2; the control end 41g of the third switch transistor 41 turns on the third switch transistor 41 after receiving the third control signal.

[0081] The integration circuit 42 has an input terminal 42a electrically connected to the second terminal 41b of the third switch transistor 41, and an output terminal 42a of the integration circuit 42 serves as an output terminal of the current detection circuit 4. The integration circuit 42 is used to reset the integration circuit 42 after the reset terminal 42s of the integration circuit 42 receives a reset signal, and integrate the large current signal output by the amplifier circuit 2 after resetting to generate a voltage drop signal.

[0082] In the signal reading stage, the first switch transistor 32 and the second switch transistor 23 are in the cut-off state, the third switch transistor 41 and the driving transistor 21 are in the on state, and the reset end 42s of the integration circuit 42 resets the integration circuit 42 after receiving the reset signal, and then integrates the large current signal output by the driving transistor 21, and generates a voltage drop signal corresponding to the large current signal in the integration circuit 42.

[0083] See also Figure 6 A schematic diagram of the structure of an integration circuit provided in an embodiment of the present disclosure.

[0084] The integration circuit 42 includes: an integration operator 421, an integration capacitor 422, and a reset device 423;

[0085] The first input terminal (also called the inverting input terminal) of the integrator 421 is used as the input terminal of the integrator 42, the output terminal of the integrator 421 is the output terminal of the integrator 42, and the second input terminal (also called the non-inverting input terminal) of the integrator 421 is connected to the reference voltage V ref .

[0086] An integrating capacitor 422, wherein a first end of the integrating capacitor 422 is electrically connected to a first input end of the integrating operator 421, and a second end of the integrating capacitor 422 is electrically connected to an output end of the integrating operator 421, and is used to integrate the large current signal output by the amplifier circuit 2 and generate a corresponding voltage drop signal on the integrating capacitor;

[0087] A reset device 423, a first end of the reset device 423 is electrically connected to the first input end of the integrator 421, a second end of the reset device 423 is electrically connected to the output end of the integrator 421, and the reset device 423 is used to reset the integral capacitor 422 and the output end of the amplifier circuit 2.

[0088] After the reset device 423 resets the integration capacitor 422 and the output terminal of the amplifier circuit 2, the integration capacitor 422 begins to integrate the detected large current signal I, and the charge Q = I × T1 generated by the driving transistor 21 during the integration time T1 is generated. The voltage drop (V c1 )for:

[0089] Vc1 =Q / C1=I×T1 / C1 (4);

[0090] Wherein, C1 is the capacitance value of the integral capacitor 422 .

[0091] See also Figure 7 A schematic diagram of the structure of the optical sensing pixel circuit provided in the embodiment of the present disclosure Figure 3 .

[0092] The optical sensing pixel circuit in the embodiment of the present disclosure includes two stages, one is a bias setting stage, and the other is a signal reading stage.

[0093] In the bias setting stage, after receiving the first control signal and the second control signal at the same time, the first switch transistor 32 and the second switch transistor 23 are controlled to be turned on (the third switch transistor 41 is in the off state at this time), and the constant current I bias Provided to the driving transistor 21, so that the driving transistor 21 outputs a constant current I bias The same current is generated, and the voltage difference between the control terminal 21g of the driving transistor 21 and the first terminal 21a of the driving transistor 21 (ie, the first voltage difference) is stored in the storage capacitor 22.

[0094] In the signal reading stage, after receiving the third control signal, the third switch transistor 41 is controlled to be turned on (at this time, the first switch transistor 32 and the second switch transistor 23 are in the off state).

[0095] At this stage, the photodiode 1 converts the optical signal into an electrical signal and stores it in the storage capacitor 22 (ie, the leakage current I RD To charge the storage capacitor 22), assuming that the charging time is T2 and the capacitance of the storage capacitor 22 is C2, the charge added to the storage capacitor 22 is:

[0096] ΔQ=ΔV c2 ×C2=I RD ×T2 (5);

[0097] Where, is ΔV c2 The voltage increment on the storage capacitor 22, I RD is the leakage current generated by the photodiode 1 , and T2 is the charging time of the storage capacitor 22 .

[0098] From formula (5), we can calculate: ΔV c2 =ΔQ / C2=I RD ×T2 / C2 (6).

[0099] Since the first voltage is stored in the storage capacitor 22 during the bias setting phase, the photodiode 1 (i.e. Figure 7 The voltage at the output terminal (point A) is Vbias , the leakage current I through the photodiode 1 during the signal reading phase RD The storage capacitor 22 (capacitance value is C2) is charged so that the voltage at point A is V bias Based on the reduction of ΔV c2 becomes V A :

[0100]

[0101] According to the driving characteristics of the transistor, the current output by the driving transistor 21 during the signal reading phase is I s :

[0102]

[0103] When I bias >>I RD (such as I bias >10I RD ),(I RD ) 2 It is very small and can be regarded as 0, so:

[0104]

[0105] From formula (9), it can be seen that the leakage current I of the photodiode 1 can be reduced by the amplifier circuit 2. RD enlarge times.

[0106] At the same time, the reset device 423 is controlled to reset the integrator 421, and then the integrator 421 performs an operation on the current I output from the output terminal 21b of the driving transistor 21, and the output voltage is the signal V out , Figure 7 For the corresponding timing circuit diagram, please refer to Figure 8 , Figure 8 A control timing diagram of an optical sensing pixel circuit provided in an embodiment of the present disclosure.

[0107] exist Figure 8 The first control signal and the second control signal are low level effective, the third control signal and the reset signal are high level effective. The voltage corresponding to the voltage drop signal output by the current detection circuit 4 is V ref -V ci , V ci is the voltage of the integrating capacitor 422 .

[0108] Figure 8 Also shown is the timing of the photoelectric sensor pixel circuits in the nth row and the photoelectric sensor pixel circuits in the (n+1)th row in the sensor composed of the above-mentioned photoelectric sensor pixel circuits in an array manner.

[0109] It should be noted that in Figure 8 In the embodiment, the first control signal, the second control signal, and the third control signal are related to the types of the corresponding transistors. When the corresponding transistor type is a P-type transistor, the corresponding control signal is valid at a low level, and when the corresponding transistor type is an N-type transistor, the corresponding control signal is valid at a high level.

[0110] Based on the same inventive concept, the present disclosure provides a driving method based on the above optical sensing pixel circuit, see Fig. 9 , the driving method includes:

[0111] Step 901: In the bias setting stage, the first switch transistor and the second switch transistor are turned on to set a first voltage corresponding to the output of the constant current for the driving transistor of the amplifier circuit, and save it in a storage capacitor; wherein the first voltage is a voltage difference between the control terminal of the driving transistor and the first terminal of the driving transistor, and the first voltage includes a threshold voltage of the driving transistor;

[0112] Step 902: In the signal reading stage, the first switch transistor and the second switch transistor are turned off, and the third switch transistor is turned on. At the same time, the integration circuit is reset, and then the third switch transistor is disconnected, so that the integration circuit starts to integrate the current signal at the output end of the amplifier circuit, generates a voltage change on the integration capacitor, and calculates the current output by the amplifier circuit based on the integration time and the voltage change.

[0113] The above processing process can be referred to the bias setting stage and signal reading stage in the above optical sensing pixel circuit, which will not be introduced here.

[0114] Based on the same inventive concept, the present disclosure provides a sensor, see Fig.10 A schematic diagram of the structure of the sensor provided in the embodiment of the present disclosure Figure 1 The sensor includes the optical sensing pixel circuits as described above arranged in an array. The sensor can be used as a sensor for fingerprint recognition.

[0115] See also Fig.11 A schematic diagram of the structure of the sensor provided in the embodiment of the present disclosure Figure 2 , the identification circuits located in the same column share a constant current bias circuit 3.

[0116] By allowing the optical sensing pixel circuits in the same column to share one constant current bias circuit 3, the number of constant current bias circuits 3 and the space occupied by the constant current bias circuits 3 can be saved.

[0117] Please continue to see Fig.11 The sensor includes a detection area S and a non-detection area NS surrounding the detection area;

[0118] A plurality of photodiodes 1 are arranged in an array in a detection area S; wherein the photodiodes 1 are arranged together with corresponding amplifier circuits 2; and a constant current bias circuit 3 is arranged in a non-detection area NS.

[0119] By arranging the constant current bias circuit 3 in the non-detection area NS, it is easy to lay out the constant current bias circuit 3 .

[0120] It should be noted that in Fig.11 The diagram of the middle amplifier circuit 2 should not be understood as just a transistor. Its structure can be found in the relevant introduction of the optical sensor pixel circuit, which will not be described here. Fig.10 and Fig.11 The number of optical sensing pixel circuits shown in the figure does not represent the actual number. The number of optical sensing pixel circuits required for a sensor can be set according to actual needs.

[0121] The sensor can be an on-screen sensor or an under-screen sensor. It can be used alone in photoelectric detection devices such as time clocks and access control devices, or in mobile devices such as mobile phones, tablet computers, and smart watches.

[0122] Based on the same inventive concept, an embodiment of the present disclosure provides a display panel including the sensor as described above.

[0123] Although the preferred embodiments of the present disclosure have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present disclosure.

[0124] Obviously, those skilled in the art can make various changes and modifications to the present disclosure without departing from the spirit and scope of the present disclosure. Thus, if these modifications and variations of the present disclosure fall within the scope of the claims of the present disclosure and their equivalents, the present disclosure is also intended to include these modifications and variations.

Claims

1. An optical sensing pixel circuit, wherein: include: A photodiode, one end of which is electrically connected to a constant voltage terminal, and the photodiode is used to detect an external optical signal and convert the optical signal into an electrical signal; wherein the electrical signal is so small that it is not easily detected; an amplifier circuit, electrically connected to the output end of the photodiode, the amplifier circuit being used to amplify the electrical signal into a detectable large current signal; A constant current bias circuit is electrically connected to the output end of the amplifier circuit and is used to provide a constant current to the amplifier circuit so as to set a static operating point for the amplifier circuit that is the same as the constant current, so that the amplifier circuit amplifies the electrical signal based on the static operating point.

2. The optical sensing pixel circuit according to claim 1, wherein: The constant current bias circuit comprises: A constant current source, used for providing the constant current; The first switch transistor is connected between the constant current source and the output end of the amplifier circuit, and is used to provide the constant current to the amplifier circuit in a bias setting stage.

3. The optical sensing pixel circuit according to claim 1, wherein: The amplifying circuit comprises: A driving transistor, wherein a first terminal of the driving transistor is electrically connected to the constant voltage terminal, a second terminal of the driving transistor serves as an output terminal of the amplifier circuit, and a control terminal of the driving transistor is electrically connected to an output terminal of the photodiode; A storage capacitor, one end of which is electrically connected to the constant voltage, and a second end of which is electrically connected to the control end of the driving transistor, for storing a first voltage of the driving transistor when the output current of the driving transistor is the constant current and receiving the electrical signal; wherein the first voltage is a voltage difference between the control end of the driving transistor and the first end of the driving transistor, and the first voltage includes a threshold voltage of the driving transistor; A second switching transistor, wherein the first end of the second switching transistor is electrically connected to the control end of the driving transistor, the second end of the second switching transistor is electrically connected to the second end of the driving transistor, and the second switching transistor is used to be turned on in the bias setting stage, so that the driving transistor stores the first voltage in the storage capacitor under the action of the constant current, and the driving transistor outputs the constant current in an amplified state.

4. The optical sensing pixel circuit according to claim 3, wherein: The constant current is greater than 10 times the leakage current of the photodiode.

5. The optical sensing pixel circuit according to any one of claims 1 to 4, wherein: Also includes: A current detection circuit is electrically connected to the output end of the amplifier circuit, and is used to detect the large current signal during the signal reading phase and convert it into a corresponding voltage drop signal.

6. The optical sensing pixel circuit according to claim 5, wherein: The current detection circuit comprises: a third switch transistor, a first end of the third switch transistor being electrically connected to the output end of the amplifier circuit, and the third switch transistor being turned on during the signal reading phase to receive the large current signal; An integration circuit, wherein the input end of the integration circuit is electrically connected to the second end of the third switching transistor, the output end of the integration circuit serves as the output end of the current detection circuit, and the integration circuit is used to reset the integration circuit after receiving a reset signal at the reset end of the integration circuit, and integrate the large current signal after resetting to generate the voltage drop signal.

7. The optical sensing pixel circuit according to claim 6, wherein: The integration circuit comprises: An integrator, wherein a first input terminal of the integrator serves as an input terminal of the integrator circuit, an output terminal of the integrator serves as an output terminal of the integrator circuit, and a second input terminal of the integrator is connected to a reference voltage; An integrating capacitor, wherein a first end of the integrating capacitor is electrically connected to a first input end of the integrating operator, and a second end of the integrating capacitor is electrically connected to an output end of the integrating operator, and is used to integrate the large current signal and generate a voltage drop on the integrating capacitor; A reset device, wherein a first end of the reset device is electrically connected to a first input end of the integrator, a second end of the reset device is electrically connected to an output end of the integrator, and the reset device is used to reset the integral capacitor and the output end of the amplifier circuit.

8. A driving method based on the optical sensing pixel according to any one of claims 1 to 7, wherein: include: In the bias setting stage, the first switch transistor and the second switch transistor are turned on, so that the constant current bias circuit provides a constant current for the amplifier circuit, so as to set a first voltage corresponding to the output of the constant current for the driving transistor of the amplifier circuit, and save it in the storage capacitor; wherein the first voltage is a voltage difference between the control terminal of the driving transistor and the first terminal of the driving transistor, and the first voltage includes a threshold voltage of the driving transistor; In the signal reading stage, the first switch transistor and the second switch transistor are turned off, and the third switch transistor is turned on. At the same time, the integration circuit is reset first, and then the third switch transistor is disconnected, so that the integration circuit starts to integrate the current signal at the output end of the amplifier circuit, generates a voltage change on the integration capacitor, and calculates the current output by the amplifier circuit based on the integration time and the voltage change.

9. A sensor, wherein: The optical sensing pixel circuit comprises the optical sensing pixel circuit as described in any one of claims 1 to 7 arranged in an array.

10. The sensor according to claim 9, wherein: Optical sensing pixel circuits located in the same column share a constant current bias circuit.

11. The sensor according to claim 10, wherein: The sensor comprises a detection area and a non-detection area surrounding the detection area; A plurality of photodiodes are arranged in an array in the detection area; The constant current bias circuit is disposed in the non-detection area.

12. A display panel, wherein: Comprising a sensor as described in any one of claims 9-11.

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