CN110299106B

CN110299106B - Light sensing driving circuit, driving method thereof and display device

Info

Publication number: CN110299106B
Application number: CN201910582517.9A
Authority: CN
Inventors: 周星耀; 高娅娜; 李玥; 杨康; 陈浩; 姚绮君
Original assignee: Shanghai Tianma AM OLED Co Ltd
Current assignee: Wuhan Tianma Microelectronics Co Ltd
Priority date: 2019-06-27
Filing date: 2019-06-27
Publication date: 2020-11-27
Anticipated expiration: 2039-06-27
Also published as: CN110299106A

Abstract

The embodiment of the application provides a light sensing driving circuit, wherein a display module group comprises a first power supply signal end, a driving transistor, an organic light emitting element and a second power supply signal end which are connected in series; the driving transistor is used for generating a driving current; the light sensing module group comprises a signal generating module and a reading module; the signal generating module is used for generating a light sensing signal under the action of illumination; the reading module is used for reading the light sensing signal; the signal generation module comprises a light sensing diode, a first storage capacitor and a first node, wherein the light sensing diode and the first storage capacitor are arranged in series; the first node is connected with the first pole of the driving transistor; the signal generating module is electrically connected with the grid electrode of the driving transistor; the reading module is electrically connected between the second pole of the driving transistor and the organic light emitting element. The photosensitive driving circuit for fingerprint identification under the screen is integrated in the screen, and the fingerprint identification function is realized and the fingerprint identification effect is improved through circuit design.

Description

Light sensing driving circuit, driving method thereof and display device

[ technical field ] A method for producing a semiconductor device

The invention relates to the technical field of display, in particular to a light sensation driving circuit, a driving method thereof and a display device comprising the light sensation driving circuit.

[ background of the invention ]

Along with consumption upgrading, the consumer needs the integrated more functions of display panel, for example fingerprint identification function, and present display panel fingerprint identification function says that the fingerprint identification chip sets up in display panel's below, utilizes the principle that organic light emitting display panel possesses certain light transmissivity to carry out fingerprint identification. However, the method needs to be externally hung with a fingerprint identification chip, has complex process and high cost, and cannot realize full-screen fingerprint identification. In the process of integrating fingerprint identification in the screen in the prior art, it is found that the parasitic capacitance on the reading lines is very large due to the layout design of the Organic Light Emitting (OLED) display panel, and the parasitic capacitance on each line is different, so that the light sensation signals generated by the light rays with the same intensity are different through the signals read by the different reading lines, and the fingerprint identification cannot be accurately completed.

[ summary of the invention ]

In view of the above, embodiments of the present invention provide a light sensing driving circuit and a driving method thereof, and a display device including the same, so as to solve the above technical problems.

In one aspect, the present application provides a light sensing driving circuit, including: the display module group and the light sensing module group; the display module group comprises a first power supply signal end, a driving transistor, an organic light-emitting element and a second power supply signal end which are connected in series; the driving transistor is used for generating a driving current; the light sensing module group comprises a signal generating module and a reading module; the signal generating module is used for generating a light sensing signal under the action of illumination; the reading module is used for reading the light sensing signal; the signal generation module comprises a light sensing diode, a first storage capacitor and a first node, wherein the light sensing diode and the first storage capacitor are arranged in series; the first node is connected with the first pole of the driving transistor; the signal generating module is electrically connected with the grid electrode of the driving transistor; the reading module is electrically connected between the second pole of the driving transistor and the organic light emitting element.

On the other hand, the present application provides a driving method of a light sensing driving circuit, which is characterized by comprising the light sensing driving circuit;

the driving method comprises a display mode and a light sensing reading mode;

the display mode includes a first initialization period, a data writing period, and a light emitting period;

during the first initialization period: the first scan signal is an active level, and the second scan signal, the third scan signal, the fourth scan signal, the first light emission control signal, and the second light emission control signal are off levels; the first initialization transistor and the second initialization transistor transmit the initialization signal to the driving transistor and the organic light emitting element to reset the driving transistor and the organic light emitting element, respectively;

in the data writing period: the second scan signal is an active level, and the first scan signal, the third scan signal, the fourth scan signal, the first light emission control signal, and the second light emission control signal are off levels; the data writing transistor writes the data signal into a gate of the driving transistor;

in the light emission period: the first and second light emission control signals are active levels, and the first, second, third, and fourth scan signals are off levels; the first light-emitting control transistor is conducted, and the first power supply signal is transmitted to the first pole of the driving transistor so that the driving transistor generates a driving current; the second emission control transistor is turned on to transmit the driving current to the organic light emitting element.

According to the light sensation drive circuit and the drive method provided by the application, the light sensation drive circuit for fingerprint identification under the screen is integrated in the screen, and the fingerprint identification effect is improved while the fingerprint identification function is realized through circuit design.

[ description of the drawings ]

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a schematic diagram of a display panel according to an embodiment of the present application;

FIG. 2 is a schematic cross-sectional view of the embodiment AA' of FIG. 1;

FIG. 3 is a diagram of a photo sensing driving circuit according to an embodiment of the present application;

FIG. 4 is a diagram of a photo sensing driving circuit according to another embodiment of the present application;

FIG. 5 is a diagram illustrating a display period of the photo sensing circuit of the embodiment of FIG. 4;

FIG. 6 is a diagram illustrating a fingerprint identification period of the light sense driving circuit of the embodiment of FIG. 4;

FIG. 7 is a diagram illustrating a fingerprint identification period and a display period of the light sense driving circuit of the embodiment of FIG. 4;

FIG. 8 is a schematic view of a display device according to the present application;

[ detailed description ] embodiments

For better understanding of the technical solutions of the present invention, the following detailed descriptions of the embodiments of the present invention are provided with reference to the accompanying drawings.

It should be understood that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It should be understood that the term "and/or" as used herein is merely one type of association that describes an associated object, meaning that three relationships may exist, e.g., a and/or B may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" herein generally indicates that the former and latter related objects are in an "or" relationship.

It should be understood that although the terms first, second, third, etc. may be used to describe the pass transistors in the embodiments of the present invention, the pass transistors should not be limited to these terms. These terms are only used to distinguish the pass transistors from each other. For example, the first pass transistor may also be referred to as a second pass transistor, and similarly, the second pass transistor may also be referred to as a first pass transistor, without departing from the scope of embodiments of the present invention.

In the prior art, in the existing fingerprint identification design, a photodiode PIN junction is adopted to receive illumination to accumulate photo-generated charges, and a reading line is adopted to read signals. Due to the fact that parasitic capacitance (Cline) on a reading line is large and different, data reading accuracy is different to a certain degree, and the fingerprint identification effect is poor.

Referring to fig. 1, fig. 2 and fig. 3, fig. 1 is a schematic view of a display panel according to an embodiment of the present application; FIG. 2 is a schematic cross-sectional view of the embodiment AA' of FIG. 1; FIG. 3 is a diagram of a photo sensing driving circuit according to an embodiment of the present application;

the display panel of the application can realize the fingerprint identification function in the screen. Referring to fig. 1, 2 and 3 in particular, the display panel of the present application includes a light sensing driving circuit, which includes a display module group 20 and a light sensing module group 30,

the display module group 20 includes a first power signal terminal PVDD, a driving transistor DT, an organic light emitting element OLED, and a second power signal terminal PVEE connected in series; the driving transistor DT is used for generating a driving current; the first power voltage terminal PVDD supplies a first power signal VDD to the first electrode of the driving transistor DT, and generates a driving current together with the potential of the gate electrode of the driving transistor DT, and the driving current flows into the second power signal terminal PVEE through the organic light emitting element OLED, driving the organic light emitting element OLED to emit light.

The light sensing module group 30 comprises a signal generating module M1 and a reading module M2; the signal generating module M1 is used for generating a light sensing signal under the action of illumination; the reading module M2 is used for reading the light sensing signal; the signal generating module M1 includes a photo diode D1 and a first storage capacitor C1 connected in series, and a first node N1 disposed between the photo diode D1 and the first storage capacitor C1; the signal generating module M1 is electrically connected to the gate of the driving transistor DT; the first node N1 is connected to the first pole of the driving transistor DT; when the light sensing diode D1 receives the light reflected by the fingerprint, the light sensing signal is transmitted to the gate of the driving transistor DT, the first power signal VDD transmitted by the first power signal terminal PVDD generates a driving current corresponding to the stable light sensing signal for reading by the reading module M2, and the reading module M2 is electrically connected between the second electrode of the driving transistor DT and the organic light emitting device OLED for reading the light sensing signal.

Referring to fig. 2, the light sensing driving circuit of the present application first drives the organic light emitting device OLED to emit light, the light emitted from the organic light emitting device OLED is incident on the finger, and when the light is incident on the finger ridge, the light passes through the glass cover plate to reach the finger ridge because the refractive indexes of the finger ridge and the glass cover plate 160 are similar. When the light enters the valleys of the finger, air is spaced between the valleys of the finger and the glass cover 160, and the refractive index of the air is much smaller than that of the finger, so that the light enters the optically thinner medium from the optically denser medium, and is totally reflected, and the reflected light irradiates the photodiode D1, thereby generating a light sensing signal. The light sensation driving circuit for the fingerprint identification module is integrated in the display panel and is connected with the OLED light-emitting pixels, and the light-emitting and fingerprint identification integration is realized by sharing the driving tube in the pixels. And, through writing the fingerprint identification reading electric potential (light sense signal) in advance into the grid of the driving transistor DT, the driving transistor DT drives the tube to generate the driving current corresponding to the light sense signal for signal reading. The active current drive is adopted, so that the signal reading capability is strong, the problem of large difference of parasitic capacitance of a reading signal line can be avoided, and the signal reading accuracy is improved.

Referring to fig. 2, the light sensing driving circuit of the present application is disposed on an organic light emitting display panel capable of simultaneously implementing light emission and fingerprint recognition. The display panel may include a substrate 110, and an active layer 120, a gate insulating layer 141, a gate metal layer 131, a first interlayer insulating layer 142, a capacitor metal layer 132, a second interlayer insulating layer 143, a source-drain metal layer 133, a planarization layer 144, a first electrode 151, and a pixel defining layer 145 sequentially disposed on the substrate 110; and the pixel defining layer 145 forms an opening in which the organic light emitting material layer 152 is formed; finally, a second electrode 153 is formed to cover the organic light emitting material layer 152.

Referring to fig. 4, fig. 5 and fig. 6, fig. 4 is a schematic diagram of a photo sensing driving circuit according to another embodiment of the present disclosure; FIG. 5 is a diagram illustrating a display period of the photo sensing circuit of the embodiment of FIG. 4; FIG. 6 is a diagram illustrating a fingerprint identification period of the light sense driving circuit of the embodiment of FIG. 4;

the signal generating module M1 further includes a signal first transmission transistor T7; the first signal transmitting transistor T7 is coupled in series between the first pole of the driving transistor DT and the first node N1; the light sensing signal is transmitted to the driving transistor DT by being controlled by the third SCAN signal SCAN 3.

Further, the signal generating module M1 further includes a second pass transistor T8; the second transfer transistor T8 is coupled in series between the gate of the driving transistor DT and the second pole of the driving transistor DT; the light sensing signal is transmitted to the gate electrode of the driving transistor DT and generates a stable light sensing signal under the control of the third SCAN signal SCAN 3. It should be noted that the generated stable photo sense signal and the photo sense signal transmitted to the gate of the driving transistor DT through the first and second transmission transistors T7 and T8 are not necessarily equal to each other. The stable light sensing signal is a signal corresponding to the light sensing signal, and the stable light sensing signal can be read to obtain an actual light sensing signal. For example, as shown in fig. 4, a first node N1 between the photo diode D1 and the first storage capacitor C1, the other pole of the photo diode D1 is connected to the other pole of the first storage capacitor C1, a common voltage signal Vcom is provided, when the reflected light of fingerprint identification irradiates the photo diode D1, a leakage current is generated to the N1 node, so that the N1 node generates a photo signal, the photo signal is transmitted to the gate of the driving transistor DT through the first transmission transistor T7, the driving transistor DT and the second transmission transistor T8, and the driving transistor DT generates a stable driving current directly corresponding to the photo signal according to the first power signal VDD and the photo signal. . On the other hand, in this embodiment, the first node N1 is not directly connected to the gate N2 of the driving transistor DT, but is connected between the second pole and the gate of the driving transistor DT in a diode manner through the second transfer transistor T8, so that the threshold of the driving transistor is captured, and the stable photo sensing signal is threshold-compensated, so that the stable photo sensing signal is not correlated with the threshold of the driving transistor, and the influence of non-uniform threshold and drift of the threshold voltage on the stable photo sensing signal is avoided.

Further, the read module M2 includes a third pass transistor T9; the third transfer transistor T9 is coupled in series between the organic light emitting element OLED and the read signal line Rd; the stable photo sensing signal is transmitted to the read chip under the control of the fourth SCAN signal SCAN 4. Since the stable photo sensing signal of the present embodiment is generated by the stable active current, the stable photo sensing signal can be transmitted to the read chip through the read signal line Rd without being affected by the parasitic capacitance of the read signal line Rd.

Further, the display module group 30 further includes an initialization module M3, a lighting control module M4, a threshold compensation module M5, a data writing module M6, and a storage module M7.

The initialization module M3 includes a first initialization transistor T1 and a second initialization transistor T2; the first initialization transistor T1 is coupled in series between the initialization signal terminal Vref and the gate of the driving transistor DT; the initialization signal ref is transmitted to the gate of the driving transistor DT by being controlled by the first SCAN signal SCAN 1; the second initializing transistor is coupled in series between the initializing signal terminal Vref and the organic light emitting element OLED; the initialization signal ref is transmitted to the organic light emitting element OLED by being controlled by the first SCAN signal SCAN1 or the second SCAN signal SCAN 2. The first and second initialization transistors T1 and T2 of the initialization module are used to transmit an initialization signal ref to the driving transistor DT and the organic light emitting element OLED for initializing the driving transistor DT and the organic light emitting element OLED.

The photo sensing module group 20 further includes a photo sensing initialization module multiplexing the first initialization transistor T1, the first transfer transistor T7, and the second transfer transistor T8 to transmit the initialization signal ref to the first node N1. Initializing the first node N1 each time before fingerprinting so that the reference point for each fingerprinting is the same may improve the accuracy of the fingerprinting. The embodiment can complete the initialization of the light sensing module group 20 without increasing transistors, thereby reducing the number of transistors and reducing the pressure of layout of the display panel.

Further, the light emitting control module M4 includes a first light emitting control transistor T3 and a second light emitting control transistor T4; the first light emitting control transistor T3 is coupled in series between the first power signal terminal PVDD and the first pole of the driving transistor DT; transmitting a first power signal VDD to a first pole of the driving transistor DT under the control of a first emission control signal EMIT 1; a connection point of the first node N1 and the first pole of the driving transistor is located between the first light emission controlling transistor T3 and the driving transistor DT; the second light emission control transistor T4 is coupled in series between the second pole of the driving transistor DT and the organic light emitting element OLED; transmitting a driving current to the organic light emitting element OLED under the control of the second emission control signal EMIT; the second light emission control transistor T4 is coupled in series between the read module M2 and the organic light emitting element OLED. The first lighting control transistor T3 is used to transmit the first power signal VDD to the gate of the driving transistor D and to prevent the first power signal VDD from being transmitted to the signal generating module M1. The second light emission controlling transistor T4 is for transmitting a driving current to the organic light emitting element OLED, and for spacing the organic light emitting element OLED from the reading module M2.

Further, the threshold compensation module M5 includes a threshold compensation transistor T5; the threshold compensation transistor T5 is coupled in series between the second pole of the driving transistor DT and the gate of the driving transistor DT; the deviation of the threshold voltage of the driving transistor DT is compensated by the second scanning signal SCAN;

the data write module M6 includes a data write transistor T6; the DATA writing transistor T6 is coupled in series between the DATA writing signal terminal DATA and the first pole of the driving transistor DT; writing a data signal into the gate of the driving transistor DT by being controlled by the second SCAN signal SCAN;

the storage module M7 includes a second capacitance CST; the second capacitor CST is coupled in series between the first power signal terminal PVDD and the gate electrode of the driving transistor DT, for storing the data signal.

A driving method of the light sensing driving circuit of the present application, which includes a display mode and a light sensing read mode, is described below with reference to the light sensing driving circuit of fig. 4 and the driving timings of fig. 5 and 6; it should be noted that the following embodiments take the second initialization transistor T2 controlled by the first SCAN signal SCAN1 as an example.

The display mode includes a first initialization period P1, a data write period P2, and a light emission period P3;

at the first initialization period P1: the first SCAN signal SCAN1 is at an active level, and the second SCAN signal SCAN2, the third SCAN signal SCAN3, the fourth SCAN signal SCAN4, the first emission control signal EMIT1, and the second emission control signal EMIT2 are at an off level; it should be noted that the active level here refers to a level that can make the transistor controlled by the active level in a conducting state, for example, in the PMOS type photo-sensing driving circuit of fig. 4, the active level refers to a low level. In the first initialization period P1, the first and second initialization transistors T1 and T2 are turned on, and the initialization signal ref is transmitted to the driving transistor DT and the organic light emitting element OLED to reset the driving transistor DT and the organic light emitting element OLED, respectively; at this time, the other transistors are all in the off state, and the initialization signal ref is stored at the node N2 of the gate of the driving transistor. In this stage, the driving transistor DT and the organic light emitting element OLED can be kept in the same initial state before each frame starts, and the uniformity of the light sensing driving circuit is improved. In addition, since the first emission control transistor T3 is in the off state, the source of the driving transistor DT may remain at the potential at the previous time, and at this time, the second emission control transistor T4 is in the off state, so that no leakage current flows through the organic light emitting element OLED, and the organic light emitting element OLED is prevented from being turned on. On the other hand, the first transfer transistor T7 is turned off to prevent the signal of the first pole of the driving transistor DT from affecting the first node N1.

During the data writing period T2: the second SCAN signal SCAN2 is at an active level, the first SCAN signal SCAN1, the third SCAN signal SCAN3, the fourth SCAN signal SCAN4, the first emission control signal EMIT1, and the second emission control signal EMIT2 are at an off level; the data writing transistor T6 writes the data signal Vdata into the gate N2 node of the driving transistor DT; at this time, the compensation transistor T5 is also in a turned-on state, the data signal Vdata is transmitted to the gate of the driving transistor DT through the first pole of the data writing transistor T6, the driving transistor DT and the compensation transistor T5, and the voltage ref stored at the node N2 of the driving transistor at the previous time is raised until the driving transistor DT is turned off when the voltage at the node N2 of the driving transistor is Vdata-Vth, where Vth is the threshold voltage of the driving transistor, and the voltage stored at the node N2 of the driving transistor is Vdata-Vth. Due to the process of manufacturing transistors, even if the same process parameters are satisfied during the manufacturing of the transistors, the threshold voltages of the transistors on the display panel are different, and the threshold voltages of the transistors drift with the increase of the service time after the transistors age, which causes the brightness of the same written data signals at different positions of the display panel to be different, and the brightness of the same written data signals displayed with the increase of the service time also to be different, which causes the display to be uneven and the color to drift. Therefore, the present embodiment grasps and stores the threshold voltage of the driving transistor DT to the gate N2 node of the driving transistor in order to eliminate the influence of the threshold voltage on the light emission luminance. It should be noted that if the second initialization transistor T2 is controlled by the second SCAN signal SCAN2, the organic light emitting element OLED is initialized in this period.

In the light emission period P3: the first and second emission control signals EMIT1 and EMIT2 are active levels, and the first, second, third, and fourth SCAN signals SCAN1, SCAN2, SCAN3, and SCAN4 are off levels; the first light-emitting control transistor T3 is turned on, and the first power signal VDD is transmitted to the first pole of the driving transistor DT to enable the driving transistor DT to generate a driving current; the second light emission controlling transistor T4 is turned on to transmit the driving current to the organic light emitting element OLED. The driving transistor DT generates a driving current Ids ═ k ^ g (Vsg-Vth) ^2 ═ k ^ g (VDD- (Vdata-Vth) -Vth) ^2 ═ k ^2 (VDD-Vdata). It can be seen that the light emission current of the present embodiment depends on the written data signal regardless of the threshold voltage of the driving transistor D through the compensation of the data writing period P2, and thus, the influence of the non-uniformity and the drift of the threshold voltage of the driving transistor on the light emission current is eliminated. Also, in the light sensing driving circuit of the present application, the light emitting function may be continuously performed individually by the timing sequence of the driving method of the light sensing driving circuit integrated with the light sensing fingerprint recognition function provided in the present embodiment, and the normal light emitting function may be performed all the time as long as the first initialization period P1, the data writing period P2, and the light emitting period P3 of the present embodiment are repeated in turn.

Further, the light sensing driving circuit of the present application can also execute a light sensing reading mode, and it should be noted that the light sensing driving circuit of the present application integrates the display module group 20 and the light sensing module group 30 to realize light sensing fingerprint identification. That is to say, the light sensing driving circuit of the present application can perform the light emitting function alone, or can multiplex the light emitting function of the organic light emitting element OLED as the light source for light sensing fingerprint identification. Referring to fig. 2, the light sensing driving circuit of the present application first drives the organic light emitting device OLED to emit light, and the light emitted from the organic light emitting device OLED is incident on the finger, and the light is incident on the finger ridge because the refractive indexes of the finger ridge and the glass cover plate 160 are similar, and thus the light passes through the glass cover plate to reach the finger ridge. When the light is incident to the valley of the finger, air is arranged between the valley of the finger and the glass cover plate 160, and at the moment, the light has the optically dense medium to be incident to the optically sparse medium, so that the light is totally reflected, and the reflected light irradiates the light sensing diode D1, so as to generate a light sensing signal. The method for reading the light sensing signal by the light sensing driving circuit of the present application is further described below.

The photo sensing read mode includes a second initialization period P4, a photo sensing voltage write period P5, and a read period P6;

at the second initialization period P4: the first SCAN signal SCAN1 is at an active level, and the second SCAN signal SCAN2, the second SCAN signal SCAN3, the fourth SCAN signal SCAN4, the first emission control signal EMIT, and the second emission control signal EMIT2 are at an off level; the first initialization transistor transmits an initialization signal ref to the driving transistor DT to reset the driving transistor DT; since the present embodiment utilizes the light source provided by the organic light emitting device OLED for light sensing fingerprint identification, therefore, the node N2 of the gate of the driving transistor DT in the previous frame is written with the light emitting signal, see fig. 2, since the light for fingerprint recognition needs to pass through the glass cover 160 and needs to be lost through reflection, therefore, the luminance of the organic light emitting device OLED is usually maximized, which means that the potential of the node of the driving transistor gate N2 is relatively low, and when the photo-reception signal generated at the first node N1 is lower due to the light irradiating the photo-sensing diode D1, the driving transistor DT cannot be turned on, the light sensing voltage signal cannot be written to the gate of the driving transistor, and there is no way to perform the subsequent period to generate the stable light sensing signal, and therefore, the driving transistor D is initialized before reading to ensure that the driving transistor DT can be turned on when the photosensitive signal is written.

In the light sense voltage writing period P5: the third SCAN signal SCAN3 is at an active level, and the first SCAN signal SCAN1, the second SCAN signal SCAN2, the fourth SCAN signal SCAN4, the first emission control signal EMIT1, and the second emission control signal EMIT2 are at an off level; the first and second transfer transistors T7 and T8 are turned on, and the light sensing signal is transmitted to the gate N2 node of the driving transistor. In this embodiment, the first node N1 is not directly connected to the gate N2 of the driving transistor DT, but is connected between the second pole and the gate of the driving transistor DT in a diode manner through the second transfer transistor T8, so that the threshold of the driving transistor is captured, and the stable photo sensing signal is threshold compensated, so that the stable photo sensing signal is not related to the threshold of the driving transistor, thereby avoiding the influence of non-uniform threshold and drift of the threshold voltage on the stable photo sensing signal. Specifically, as in the data writing phase T2, for example, the light sensing signal generated by the first node N1 is V1, the driving transistor DT is turned on in the light sensing voltage writing phase P5, the light sensing signal V1 raises the ref voltage of the node N2, the driving transistor DT is turned off when the node N2 is V1-Vth, and the gate second node N2 stores the voltage V1-Vth.

At the reading period P6: the fourth SCAN signal SCAN4 and the first emission control signal EMIT1 are at an active level, and the first SCAN signal SCAN1, the second SCAN signal SCAN2, the third SCAN signal SCAN3, and the second emission control signal EMIT2 are at an off level; transmitting a first power supply signal VDD to a first pole of a driving transistor DT to generate a stable photosensitive voltage; the third pass transistor T9 is turned on, and the stable photo sensing voltage is transmitted to the read chip. When the first power signal VDD is transmitted to the gate N2 node of the driving transistorThe generated driving current is Ids ═ k (VDD-V1) ^2, and a stable photo sensing signal is generated at the third node N3 connected to the third transfer transistor T9 at the second terminal of the driving transistor DT and transmitted to the readout chip through the third transfer transistor T9 and the readout line Rd, and the readout chip can read the parameters directly related to V1, thereby calculating the photo sensing signal V1. Since the driving transistor DT can always generate a stable light sensing signal current in the reading process, the reading chip can read an accurate light sensing signal without being influenced by the parasitic capacitance C on the reading line Rd_lineTo avoid parasitic capacitance C_lineThe difference causes the inaccurate problem of reading, consequently, this application can read accurate light sense signal, promotes fingerprint identification's precision. It should be noted that the same row of photo sensing driving circuits share the same readout line Rd, so that the readout is performed in a time-sharing manner, and the stage P7 in fig. 6 refers to the period when the other rows read the photo sensing signals.

Further, referring to fig. 7, fig. 7 is a schematic diagram illustrating a fingerprint identification period and a display period of the light sensing driving circuit of the embodiment of fig. 4; in order to further improve the accuracy of fingerprint identification, the time of fingerprint identification is controlled;

in the third initialization period P0, the first and third SCAN signals SCAN1 and SCAN3 are active levels, and the second and fourth SCAN signals SCAN2 and SCAN4, the first and second emission control signals EMIT1 and EMIT2 are off levels; the first node N1 is discharged through the first transfer transistor T7, the second transfer transistor T8, and the first initialization transistor T1, thereby initializing the first node N1. This initialization is used to erase the voltage at the first node N1 remaining during the last fingerprint recognition, thereby avoiding fingerprint recognition errors. For example, the photodiode D1 receives light at the previous time, and generates the photo signal V3 corresponding to the received light at the first node N1. However, when there is no third initialization process, the light sensing signal V3 at the previous time is maintained by the first capacitor C1, so that the signal read by the fingerprint identification at this time corresponds to the received light, and an identification error occurs. Therefore, the present embodiment eliminates the potential remaining at the first node N1 at the previous time by the third initialization period PO, improving the accuracy of fingerprint identification.

At the third initialization period P0, the first node N1 is initialized; then, a display mode is executed, the light sensing diode D1 generates electric leakage in different degrees according to the reflected light of the finger illuminated by the display mode light, so that the first node N1 becomes a light sensing signal corresponding to the illumination, and finally, a light sensing reading mode is executed, and the stable light sensing signal of the first node N1 is read through the active current, so as to finally realize fingerprint identification. And the intensity of the signal can be changed by controlling the time of the middle display mode, so that the accuracy of light sensing fingerprint identification is improved.

Further, the third initialization period P0 and the first initialization period P1 may be simultaneously performed, the first SCAN signal SCAN1 and the third SCAN signal SCAN3 are active levels, and the second SCAN signal SCAN2, the fourth SCAN signal SCAN4, the first emission control signal EMIT1 and the second emission control signal EMIT2 are off levels; the gate of the driving transistor and the first node N1 are initialized at the same time, or the gate of the driving transistor, the first node N1 and the organic light-emitting element OLED are initialized at the same time, so that the working time of fingerprint identification is shortened, and the efficiency of fingerprint identification is improved.

In another embodiment of the present application, the third initialization period P0, the second and third SCAN signals SCAN2 and SCAN3 are active levels, and the first and fourth SCAN signals SCAN1 and SCAN4, the first and second emission control signals EMIT1 and EMIT2 are off levels; the DATA line signal terminal DATA inputs the initialization signal, and the first node N1 is discharged through the first transfer transistor T7 and the DATA writing transistor T6, thereby initializing the first node N1. The present embodiment can prevent the initialization potential of the first node N1 from including the threshold voltage Vth of the driving transistor, so that the initialization is not uniform due to non-uniform threshold voltage or drift with use. On the other hand, the embodiment also does not need to add signal lines and transistors, and is beneficial to layout of the fingerprint identification display panel. In the present embodiment, the third initialization period P0 may also enable the first SCAN signal SCAN1 to be active at the same time as the first initialization period P1, so as to reduce the operating time of fingerprint identification and improve the efficiency of fingerprint identification.

In another embodiment of the present application, the third initialization period P0, the first SCAN signal SCAN1, the third SCAN signal SCAN3, and the fourth SCAN signal SCAN4 are at an active level, and the second SCAN signal SCAN2, the first emission control signal EMIT1, and the second emission control signal EMIT2 are at an off level; the readout line Rd inputs an initialization signal, the driving transistor DT is turned on, and the first node N1 is discharged through the first transfer transistor T7, the driving transistor DT, and the third transfer transistor T9, thereby initializing the first node N1. Of course, at this time, the second initialization transistor T4 may be controlled by the first SCAN signal SCAN1, which is equivalent to being performed simultaneously with the first initialization period, so as to reduce the working time of fingerprint identification and improve the efficiency of fingerprint identification.

Referring to fig. 8, fig. 8 is a schematic view of a display device according to an embodiment of the present application. The application also discloses a display device. The display device of the application can comprise the display panel with the light sensation driving circuit, wherein the light sensation display panel comprises sub-pixels which are arranged in an array mode, and each sub-pixel is electrically connected with the light sensation driving circuit. Including but not limited to cellular phone 1000, tablet computers, displays for applications on smart wearable devices, display devices for applications on vehicles such as automobiles, and the like. As long as the display device includes the light sensing driving circuit included in the display device disclosed in the present application, the display device is considered to fall within the scope of the present application.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A light sensing driving circuit, comprising: the display module group and the light sensing module group;

the display module group comprises a first power supply signal end, a driving transistor, an organic light-emitting element and a second power supply signal end which are connected in series; the driving transistor is used for generating a driving current;

the light sensing module group comprises a signal generating module and a reading module; the signal generating module is used for generating a light sensation signal under the action of illumination; the reading module is used for reading the light sensation signal;

the signal generation module comprises a light sensing diode and a first storage capacitor which are arranged in series, and a first node arranged between the light sensing diode and the first storage capacitor;

the first node is connected with a first pole of the driving transistor; the signal generating module is electrically connected with the grid electrode of the driving transistor; the reading module is electrically connected between the second pole of the driving transistor and the organic light emitting element.

2. A light sensation driver circuit as claimed in claim 1,

the signal generation module further comprises a first signal transmission transistor;

the first transfer transistor is coupled in series between the first pole of the drive transistor and the first node; the light sensing signal is transmitted to the driving transistor under the control of a third scanning signal.

3. A light sensation driver circuit as claimed in claim 2,

the signal generation module further comprises a second pass transistor;

the second pass transistor is coupled in series between the gate of the drive transistor and the second pole of the drive transistor; the light sensing signal is transmitted to the gate of the driving transistor under the control of the third scanning signal, and is used for compensating the deviation of the threshold voltage of the driving transistor to generate a stable light sensing signal.

4. A light sensation driver circuit according to claim 3,

the reading module comprises a third transmission transistor;

the third transfer transistor is coupled in series between the organic light emitting element and a read signal line; and transmitting the stable light sensing signal to a reading chip under the control of a fourth scanning signal.

5. A light sensation driver circuit according to claim 4, wherein,

the display module group further comprises an initialization module, a light emitting control module, a threshold compensation module, a data writing module and a storage module.

6. A light sensation driver circuit according to claim 5, wherein,

the initialization module comprises a first initialization transistor and a second initialization transistor;

the first initialization transistor is coupled in series between an initialization signal terminal and the gate of the driving transistor; transmitting an initialization signal to the gate of the driving transistor under the control of a first scan signal;

the second initialization transistor is coupled in series between the initialization signal terminal and the organic light emitting element; the initialization signal is transmitted to the organic light emitting element under control of the first scan signal or the second scan signal.

7. A light sensation driver circuit according to claim 6,

the light sense module group further comprises a light sense initialization module, and the light sense initialization module multiplexes the first initialization transistor, the second transmission transistor and the first transmission transistor and transmits the initialization signal to the first node.

8. A light sensation driver circuit as claimed in claim 7,

the light emitting control module comprises a first light emitting control transistor and a second light emitting control transistor;

the first light emission control transistor is coupled in series between the first power signal terminal and the first pole of the driving transistor; transmitting a first power signal to a first pole of the driving transistor under control of the first light emission control signal;

the connection point of the first node and the first pole of the driving transistor is positioned between the first luminous control transistor and the driving transistor;

the second light emission control transistor is coupled in series between the second electrode of the driving transistor and the organic light emitting element; transmitting the driving current to the organic light emitting element under control of a second light emission control signal;

the second emission control transistor is coupled in series between the read module and the organic light emitting element.

9. A light sensation driver circuit as claimed in claim 8,

the threshold compensation module comprises a threshold compensation transistor; the threshold compensation transistor is coupled in series between the second pole of the drive transistor and the gate of the drive transistor; the deviation of the threshold voltage of the driving transistor is compensated by the second scanning signal;

the data writing module comprises a data writing transistor; the data write transistor is coupled in series between the data write signal terminal and the first pole of the drive transistor; writing a data signal into the gate of the driving transistor under the control of the second scan signal;

the storage module comprises a second capacitor; the second capacitor is coupled in series between the first power signal terminal and the gate of the driving transistor for storing the data signal.

10. A driving method of a light sensing driving circuit, comprising the light sensing driving circuit of claim 9;

the driving method comprises a display mode and a light sensing reading mode;

11. The driving method of light sensation driving circuit according to claim 10, characterized in that,

the light sensing reading mode comprises a second initialization period, a light sensing voltage writing period and a reading period;

during the second initialization period: the first scan signal is an active level, and the second scan signal, the third scan signal, the fourth scan signal, the first light emission control signal, and the second light emission control signal are off levels; the first initialization transistor transmits the initialization signal to the driving transistor to reset the driving transistor;

in the light sensing voltage writing period: the third scanning signal is an active level, and the first scanning signal, the second scanning signal, the fourth scanning signal, the first light emission control signal, and the second light emission control signal are off levels; the first transmission transistor and the second transmission transistor are conducted, and the light sensing signal is transmitted to the grid electrode of the driving transistor;

during the reading period: the fourth scan signal and the first light emission control signal are active levels, and the first scan signal, the second scan signal, the third scan signal, and the second light emission control signal are off levels; the first light-emitting control transistor is conducted, the first power supply signal is transmitted to the first pole of the driving transistor, and stable light sensing voltage is generated; the third transmission transistor is conducted, and the stable photosensitive voltage is transmitted to the reading chip.

12. The driving method of light sensation driving circuit according to claim 11, wherein,

a third initialization phase is also included;

in the third initialization period, the first scan signal and the third scan signal are at an active level, and the second scan signal, the fourth scan signal, the first light emission control signal and the second light emission control signal are at an off level; the first node is discharged through the first transfer transistor, the second transfer transistor, and the first initialization transistor, thereby initializing the first node.

13. A light-sensing display device, comprising a light-sensing display panel, wherein the light-sensing display panel comprises sub-pixels arranged in an array, and each sub-pixel is electrically connected to the light-sensing driving circuit as claimed in any one of claims 1 to 9.