CN115765649A

CN115765649A - Current amplifying circuit, driving method thereof, ambient light detection circuit and display panel

Info

Publication number: CN115765649A
Application number: CN202211448924.9A
Authority: CN
Inventors: 殷新社; 赵辉; 陈观钦
Original assignee: BOE Technology Group Co Ltd
Current assignee: BOE Technology Group Co Ltd
Priority date: 2022-11-18
Filing date: 2022-11-18
Publication date: 2023-03-07

Abstract

The disclosure relates to the technical field of display, and provides a current amplification circuit, a driving method thereof, an ambient light detection circuit and a display panel. The current amplification circuit is used for detecting ambient light of the display panel, and comprises an induction module, a storage module and a driving module, wherein the induction module is used for collecting the ambient light and outputting induction current based on the ambient light in response to a voltage difference between a first node and a first voltage end, and the storage module is used for storing electric quantity by utilizing the induction current and converting the stored electric quantity into a voltage signal to be coupled to the first node; the driving module is used for responding to a voltage signal of the first node and providing driving current for the second node by using a voltage difference between the second voltage end and the second node, wherein the driving current increases along with the increase of the voltage of the first node.

Description

Current amplifying circuit, driving method thereof, ambient light detection circuit and display panel

Technical Field

The present disclosure relates to the field of display technologies, and in particular, to a current amplifying circuit, a driving method thereof, an ambient light detection circuit, and a display panel.

Background

With the development of display technologies, more and more functions can be realized by display devices, for example, the display devices detect ambient light, and perform display color temperature adjustment, display brightness adjustment, and the like according to the ambient light, thereby increasing the experience of users. With the improvement of the integration of application technologies and display devices, the improvement of the light sensing accuracy of the photosensor and the reduction of the area of the photosensor are increasingly required.

Disclosure of Invention

The present disclosure provides a solution for improving the light sensing accuracy of an ambient light sensor and reducing the sensor area, and provides a current amplifying circuit, a driving method thereof, an ambient light detecting circuit, and a display panel.

According to an aspect of the present disclosure, there is provided a current amplification circuit for detecting ambient light of a display panel, the current amplification circuit including: the sensing module is connected with a first node and a first voltage end, and is used for collecting ambient light and responding to the voltage difference between the first node and the first voltage end to output an induced current based on the ambient light; the first end of the storage module is connected with the first node, the second end of the storage module is connected with the second voltage end, and the storage module is used for storing electric quantity by utilizing the induced current and converting the stored electric quantity into a voltage signal to be coupled to the first node; the driving module is used for responding to the voltage signals at the first node and the second voltage end to provide driving current to the second node, wherein the driving current increases along with the increase of the voltage of the first node.

In an exemplary embodiment of the present disclosure, the storage module includes: a first pole of the storage capacitor is connected with the first node, and a second pole of the storage capacitor is connected with the second voltage end; the driving module includes: and the first pole of the driving transistor is connected with the second voltage end, the second pole of the driving transistor is connected with the second node, the grid of the driving transistor is connected with the first node, and the driving transistor is used for responding to a voltage signal of the first node to provide driving current for the second node.

In an exemplary embodiment of the present disclosure, the driving transistor is an N-type transistor.

In an exemplary embodiment of the present disclosure, a voltage difference of the first voltage terminal and the second voltage terminal is greater than a threshold voltage of the driving transistor.

In an exemplary embodiment of the present disclosure, a voltage difference between the first voltage terminal and the second voltage terminal is greater than a sum of a threshold voltage of the driving transistor, a minimum bias voltage of the sensing module, and a gate dynamic voltage range of the driving transistor.

In an exemplary embodiment of the present disclosure, the voltage of the second voltage terminal satisfies the following relationship:

in the formula: v _E Indicating the voltage value, V, of the second voltage terminal _B Representing the second node voltage, I _DR(Max) Maximum induced current, T, generated by the induction module _Max Indicating the maximum charging time period for the storage capacitor, cst, indicating the capacitance of the storage capacitor.

In an exemplary embodiment of the present disclosure, the current amplifying circuit further includes: the reset module is used for responding to a signal of the reset signal end to transmit a voltage signal of the first voltage end to the first node so as to reset the first node; a first switch module, a first end of which is connected to the first node, a second end of which is connected to the second node, and a control signal end of which is connected to a first control signal end, wherein the first switch module is used for responding to a signal of the first control signal end to conduct the first node and the second node; and the first end of the second switch module is connected with the second node, the second end of the second switch module is connected with the third node, the control signal end of the second switch module is connected with the second control signal end, and the second switch module is used for responding to a signal of the second control signal end to transmit the driving current to the third node.

In an exemplary embodiment of the present disclosure, the turn-on level of the reset module, the turn-on level of the first switch module, and the turn-on average of the second switch module are the same in polarity as the turn-on level of the driving module.

In an exemplary embodiment of the present disclosure, the reset module includes: a reset transistor, having a first pole connected to the first voltage terminal, a second pole connected to the first node, and a gate connected to the reset signal terminal, wherein the reset transistor is configured to transmit a voltage signal of the first voltage terminal to the first node in response to a signal of the reset signal terminal; the first switch module includes: a first transistor, having a first electrode connected to the first node, a second electrode connected to the second node, and a gate connected to the first control signal terminal, the first transistor being configured to turn on the first node and the second node in response to a signal of the first control signal terminal; the second switch module includes: and a second transistor, having a first electrode connected to the second node, a second electrode connected to the third node, and a gate connected to the second control signal terminal, wherein the second transistor is configured to turn on the second node and the third node in response to a signal of the second control signal terminal.

In an exemplary embodiment of the present disclosure, the reset transistor, the first transistor, and the second transistor are all N-type transistors.

According to a second aspect of the present disclosure, there is also provided a driving method of a current amplification circuit, for driving the current amplification circuit according to any embodiment of the present disclosure, the driving method including: in an integration phase, the storage module stores electric quantity by using the induction current and converts the stored electric quantity into voltage to be coupled to the first node; in a current collection phase, the driving module outputs a driving current in response to the voltage signal of the first node, wherein the driving current increases with the increase of the voltage of the first node.

According to a third aspect of the present disclosure, there is also provided an ambient light detection circuit comprising: the current amplification circuit of any embodiment of the present disclosure; the current conversion circuit is connected with a third node and a fourth node and is used for converting the driving current output by the current amplification circuit into induction voltage and outputting the induction voltage to the fourth node; the filter circuit is connected with the output end of the current conversion circuit and is used for outputting the induction voltage after low-pass filtering; and the analog-to-digital conversion circuit is connected to the output end of the filter circuit and is used for converting the acquired induction voltage into a digital voltage signal to be output.

In an exemplary embodiment of the present disclosure, the current conversion circuit includes: one input end of the signal amplification unit is connected with a reference voltage end, the other input end of the signal amplification unit is connected with the third node, and the output end of the signal amplification unit is connected with the fourth node; and the gain control unit is provided with a gain coefficient, one end of the gain control unit is connected with the third node, the other end of the gain control unit is connected with the output end of the signal amplification unit, and the gain control unit is used for determining the induction voltage according to the gain coefficient.

in the formula: v _E Representing the voltage value, V, of the second voltage terminal _B Representing the second node voltage, I _DR(Max) Maximum induced current, T, generated by the induction module _Max Indicating the maximum charging time period for the storage capacitor, cst, indicating the capacitance of the storage capacitor.

In an exemplary embodiment of the present disclosure, the current conversion circuit further includes: and the feedback unit is connected in parallel with two ends of the gain control unit and is used for preventing the signal amplification unit from self-exciting.

In an exemplary embodiment of the present disclosure, the gain control unit includes a gain resistor; the signal amplification unit comprises an operational amplifier, one input end of the operational amplifier is connected with the reference voltage end, the other input end of the operational amplifier is connected with the third node, and the output end of the operational amplifier is connected with the fourth node; the feedback unit comprises a feedback capacitor, and the feedback capacitor is connected in parallel to two ends of the resistor.

In an exemplary embodiment of the present disclosure, the filter circuit includes: one end of the filter resistor is connected with the first end of the filter unit, and the other end of the filter resistor is connected with the second end of the filter unit; and one end of the filter capacitor is connected with the second end of the filter unit, and the other end of the filter capacitor is grounded.

According to a fourth aspect of the present disclosure, there is also provided a display panel including the ambient light detection circuit according to any embodiment of the present disclosure.

The current amplification circuit provided by the disclosure, the sensing module outputs an induced current to the first node based on ambient light, the storage module is connected with the first node, the storage module stores electric quantity by using the induced current of the first node, the storage module further converts the stored electric quantity into a voltage signal to be coupled to the first node, and the driving module provides a driving current increased along with the voltage increase of the first node to the second node under the control of the voltage signal of the first node, so that the induced current is amplified by using the storage module and the driving module.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the disclosure. It should be apparent that the drawings in the following description are merely examples of the disclosure and that other drawings may be derived by those of ordinary skill in the art without inventive effort.

Fig. 1 shows a corresponding schematic diagram of the induced current detected by a photosensor at different illumination intensities;

FIG. 2 is a schematic diagram of a current amplifying circuit according to an embodiment of the present disclosure;

FIG. 3 is a timing diagram of nodes of the current amplifying circuit of FIG. 2;

FIG. 4 is an equivalent circuit diagram of the current amplifying circuit in FIG. 2 during a reset phase;

FIG. 5 is an equivalent circuit diagram of the current amplifying circuit in FIG. 2 during a threshold compensation phase;

FIG. 6 is an equivalent circuit diagram of the current amplifying circuit in FIG. 2 during an integration phase;

FIG. 7 is an equivalent circuit diagram of the current amplifying circuit in FIG. 2 during a current collection phase;

fig. 8 is a schematic structural diagram of an ambient light detection circuit according to an embodiment of the present disclosure.

Detailed Description

Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted. Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale.

Although relative terms, such as "upper" and "lower," may be used herein to describe one element of an icon relative to another, such terms are used herein for convenience only, e.g., with reference to the orientation of the example illustrated in the drawings. It will be understood that if the illustrated device is turned upside down, elements described as "upper" will be those that are "lower". When a structure is "on" another structure, it may mean that the structure is integrally formed with the other structure, or that the structure is "directly" disposed on the other structure, or that the structure is "indirectly" disposed on the other structure via another structure.

The terms "a," "an," "the," "said," and "at least one" are used to indicate the presence of one or more elements/components/parts/etc.; the terms "comprising" and "having" are intended to be inclusive and mean that there may be additional elements/components/etc. other than the listed elements/components/etc.; the terms "first," "second," and "third," etc. are used merely as labels, and are not limiting on the number of their objects.

As shown in fig. 1, the ordinate represents the leakage current of the photosensor, and the abscissa represents the bias voltage of the photosensor, and it can be seen that, when the photosensor is forward biased, the leakage current generated when the illumination intensity is low is not significantly changed when the photosensor is forward biased, and when the photosensor is reverse biased, the leakage current generated when the illumination intensity is low is also significantly distinguished. Because the leakage current when photoelectric sensor reverse bias is under different light intensities, present different electric leakage characteristics, can utilize this characteristic to make certain area's photoelectric sensor in display device and detect ambient light, the sensing signal that corresponds the size is exported according to ambient light's illumination intensity to further utilize the sensing signal that detects to show the automatically regulated of luminance.

However, the inventors found that the leakage current of the photoelectric sensor made of thin film is extremely small at different light intensities, corresponding to pA level and nA level. The simplest and most reliable resistance sampling method for the external sampling circuit is characterized in that the maximum high-precision resistance is only 10Mohm, namely, only uA-level current can be collected, and the photoelectric sensor only has pA-level current, in order to enable the external circuit to collect current, one method is to increase the photoelectric area of the sensor, namely, tens of thousands of sensor devices are connected in parallel to increase the area of the photoelectric sensor, but the increase of the area of the photoelectric sensor can occupy the limited space of the display screen, and the integration of other functions of the display screen is influenced.

The present disclosure provides a current amplifying circuit for solving the above technical problem, which can detect ambient light with different illumination intensities without increasing the area of the display screen. The technical scheme of the disclosure is specifically described below with reference to the accompanying drawings.

Fig. 2 is a schematic structural diagram of a current amplifying circuit according to an embodiment of the present disclosure, and as shown in fig. 2, the current amplifying circuit 100 may include a sensing module 10, a storage module 20, and a driving module 30, wherein the sensing module10 connect the first node a and the first voltage terminal V _C The sensing module 10 is operable to collect ambient light and is responsive to the first node A and the first voltage terminal V _C Based on ambient light to output an induced current I _DR (ii) a The first terminal of the memory module 20 is connected to the first node A, and the second terminal of the memory module 20 is connected to the second voltage terminal V _E The memory module 20 can be used to utilize the induced current I _DR Storing electric quantity and converting the stored electric quantity into a voltage signal to be coupled to a first node A; the first terminal of the driving module 30 is connected to the second voltage terminal V _E A second terminal of the driving module 30 is connected to the second node B, a control signal terminal of the driving module 30 is connected to the first node a, and the driving module 30 is configured to respond to the first node a and the second voltage terminal V _E To provide a driving current I to a second node B _TD Driving current I _TD Increases as the voltage of the first node a increases.

The current amplifying circuit 100 and the sensing module 10 provided in the present disclosure output an induced current I based on ambient light _DR To the first node A, the memory module 20 is connected to the first node A, and the memory module 20 utilizes the induced current I of the first node A _DR The storage module 20 further converts the stored power into a voltage signal and couples the voltage signal to the first node a, and the driving module 30 provides a driving current I to the second node B under the control of the voltage signal of the first node a, wherein the driving current I increases with the increase of the voltage of the first node a _TD Thereby inducing current I by using the memory module 20 and the driving module 30 _DR Amplification is performed.

The sensing module 10 of the present disclosure may be a current sensing module, which can output an induced current I of a corresponding magnitude according to the intensity of the optical signal _DR . In an exemplary embodiment, as shown in fig. 2, the sensing module 10 may include a photosensor D _ALS Photoelectric sensor D _ALS Can be connected with a first voltage terminal V _C Photoelectric sensor D _ALS May be connected to the first node a. Photoelectric sensor D _ALS The induced current I of a corresponding magnitude can be output based on the optical signal _DR Induced current I _DR Charging the memory module 20 via the first node a, the memory module 20 proceedsThe amount of power is stored and the stored power is converted into a voltage signal.

The storage module 20 of the present disclosure refers to a circuit capable of storing power and performing voltage coupling. Generally, the memory module 20 may be implemented by a capacitor. As shown in fig. 2, in an exemplary embodiment, the storage module 20 may include a storage capacitor Cst having a first pole connected to the first node a and a second pole connected to the second voltage terminal V _E . Induced current I _DR The storage capacitor Cst may be charged, so that the charge of the storage capacitor Cst is increased to accumulate the electric quantity, because the first pole of the storage capacitor Cst is connected to the first node a, the voltage of the first node a increases after the electric quantity increases, that is, the voltage of the control signal terminal of the driving module 30 increases, in other words, the voltage increase of the control signal terminal of the driving module 30 is determined by the electric quantity stored by the storage capacitor Cst, therefore, the voltage increase of the first node a may be determined according to the electric quantity stored by the storage capacitor Cst, and the current signal amplified by the amplification characteristic of the driving module 30 based on the voltage of the first node a, that is, the driving current I _TD 。

The driving module 30 can output the driving current I by using the voltage signal of the control signal terminal _TD And driving a current I _TD The voltage at the first node A increases, indicating that the driving module 30 has an amplification characteristic, and the driving current I is increased when the voltage at the control signal terminal increases _TD And also correspondingly increased; when the voltage of the control signal terminal is reduced, the current I is driven _TD And is correspondingly reduced. The voltage of the control signal terminal of the driving module 30 and the driving current I outputted by the driving module 30 _TD Has a one-to-one correspondence relationship so that the memory module 20 is induced by the induced current I _DR The voltage charged and stored to the first node a (i.e. the voltage at the control signal terminal of the driving module 30) is converted into the driving current I with the corresponding magnitude by the driving module 30 _TD Realize the pair of induced currents I _DR The amplified output of (1).

The driving module 30 of the present disclosure may be implemented by a transistor. Illustratively, as shown in fig. 2, the driving module 30 may include a driving transistor T _D Driving transistor T _D Is connected with a second voltage terminal V _E A second electrode connected to the second node B, a gate connected to the first node A, and a driving transistor T _D Operable to provide a drive current I to a second node B in response to a voltage signal at a first node A _TD . Wherein the driving transistor T _D Is connected to the first node a, the memory module 20 may utilize the sense current I, as described above _DR Charging is performed to raise the voltage of the first node A, and after the voltage of the first node A rises, the transistor T is driven _D Is greater than its threshold voltage Vth, so that the driving transistor T _D Is turned on, and further, is controlled by a second node B and a second voltage terminal V _E Is sufficiently large to drive the transistor T _D Operating in saturation region, and driving the transistor T according to the output characteristic curve of the transistor _D The magnitude of the driving current outputted therefrom in the saturation region increases as the gate voltage increases, thereby driving the transistor T _D The increased voltage signal of the first node A can be converted into a corresponding driving current I _TD Output is performed, obviously, the output driving current I _TD Comparing the induced current I output by the induction module 10 _DR Is amplified, thereby, the photoelectric sensor D is not added _ALS The induced current I under different illumination intensities can be detected under the condition of area _DR Addition of the photosensor D compared to the related art _ALS Area-wise collection of the induced current I _DR In the scheme, the ambient light detection circuit based on the current amplification circuit 100 provided by the disclosure occupies a small space, and does not affect the realization of other functions of the display panel. Of course, it is understood that the driving module 30 may have other circuit structures in other embodiments.

As shown in FIG. 2, in an exemplary embodiment, the driving transistor T _D The transistor may be an N-type transistor, for example, an N-type oxide thin film transistor. Drive transistor T _D The channel region of (1) can be formed by indium gallium zinc oxide, and the N-type oxide thin film transistor has smaller leakage current, so that the leakage current can be reduced. Of course, in other embodiments, the driving transistor T _D Also can be usedIs a P-type transistor, and may be, for example, a P-type low temperature polysilicon transistor or the like, and it will be understood that when the drive transistor TD is a P-type transistor, the photosensor D _ALS In a manner just opposite to that shown in figure 2.

As shown in FIG. 2, in an exemplary embodiment, the first voltage terminal V _C And a second voltage terminal V _E Is greater than the driving transistor T _D Threshold voltage Vth of, and photosensor D _ALS Minimum bias voltage V _R And a driving transistor T _D The sum of the gate dynamic voltage ranges. The photoelectric sensor generates different induced currents under different illumination, and the capacitance voltage integrated on the storage capacitor by the different induced currents has a variation range, so that the driving transistor T is driven _D Has a dynamic voltage range D _R Driving transistor T _D Gate dynamic voltage range of D _R The maximum value of (A) is the driving transistor T when the capacitor voltage integrated on the storage capacitor is maximum _D The gate voltage of (c). As mentioned above, the present disclosure is directed to a photosensor D _ALS Reverse bias, providing a reverse bias current, and thus the photosensor D described herein _ALS Minimum bias voltage V _R I.e. a photoelectric sensor D _ALS Minimum bias voltage at reverse bias. First voltage terminal V _C And a second voltage terminal V _E Is larger than the driving transistor T _D Threshold voltage Vth of, and photosensor D _ALS Minimum bias voltage V _R And a drive transistor T _D Thereby enabling the photosensor D _ALS The operation is in a reverse bias state to generate an induced current corresponding to the intensity of the illumination.

In an exemplary embodiment, the second voltage terminal V _E Satisfies the following relationship:

in the formula: v _E Indicating the voltage value, V, of the second voltage terminal _B To representVoltage value of the second node, I _DR(Max) Maximum induced current, T, generated by the induction module _Max Indicating the maximum charging time period for the storage capacitor and Cst indicating the capacitance of the storage capacitor.

Voltage value V of second voltage terminal _E Satisfies the above relation (1), thereby driving the transistor T _D The source-drain voltage of the transistor is larger than the difference value of the grid-source voltage and the threshold voltage thereof, so that the driving transistor T _D Working in an amplifying state on the induced current I _DR And outputting after amplification.

As shown in fig. 2, in an exemplary embodiment, the current amplifying circuit 100 of the present disclosure may further include a reset module 40, a first switch module 50, and a second switch module 60, wherein a first end of the reset module 40 is connected to the first voltage terminal V _C The second terminal of the reset module 40 is connected to the first node a, the control signal terminal of the reset module 40 is connected to the reset signal terminal RST, and the reset module 40 is configured to respond to the signal of the reset signal terminal RST to couple the first voltage terminal V to the first voltage terminal V _C To the first node a to reset the first node a. A first terminal of the first switch module 50 is connected to the first node a, a second terminal of the first switch module 50 is connected to the second node B, a control signal terminal of the first switch module 50 is connected to the first control signal terminal VTS, and the first switch module 50 is configured to respond to a signal of the first control signal terminal VTS to turn on the first node a and the second node B. A first terminal of the second switch module 60 is connected to the second node B, a second terminal of the second switch module 60 is connected to the third node C, a control signal terminal of the second switch module 60 is connected to the second control signal terminal SEN, and the second switch module 60 is configured to drive the current I in response to a signal of the second control signal terminal SEN _TD To the third node C.

The reset module 40 can be turned on during the reset phase to connect the first voltage terminal V _C The voltage signal is transmitted to the first node A, so that the first node A and the first voltage terminal V _C And (4) equipotential.

The first switch module 50 can be turned on during a threshold compensation phase after the reset phase to turn on the communication paths between the first node a and the second node B, so that the first end and the controller of the driving module 30The signal control ends are communicated. In an exemplary embodiment, the first voltage terminal V _C And a second voltage terminal V _E Is greater than the driving transistor T _D The threshold voltage of (2). After resetting the first node a, the first voltage terminal V may be set _C Is written into the first node A, i.e. the voltage of the first node A is the first voltage end V _C Therefore, during the threshold compensation phase, the first switch module 50 turns on the first node a and the second node B, and the first node a can pass through the first switch module 50 and the driving transistor T _D The formed conduction path is toward the second voltage end V _E Discharging, so that the voltage of the first node a drops. When the voltage of the first node A and the second voltage terminal V _E Voltage difference of (2) and the driving transistor T _D When the threshold voltage of the driving transistor T is the same, the driving transistor T _D Is turned off, at this time, the transistor T is driven _D Is written into the first node a and the second voltage terminal V _E On the storage capacitor Cst in between, thereby driving the transistor T _D Is stored in the storage capacitor Cst in advance.

The second switch module 60 may be turned on during the current collection phase, such that the second node B and the third node C form a conduction path, thereby driving the driving current I provided by the driving module 30 _TD The driving current I can be obtained through the conduction path to the third node C and then through another circuit structure of the ambient light detection connected to the third node C _TD Corresponding to the acquisition of the current corresponding to I _DR The current signal of (2).

As shown in fig. 2, in an exemplary embodiment, the turn-on level of the reset module 40, the turn-on level of the first switch module 50, and the turn-on average of the second switch module 60 may be the same polarity as the turn-on level of the driving module 30, and may be, for example, a high level. Of course, in other embodiments, the conduction levels of the circuits may be all low, or the conduction levels of some circuits may be low and the conduction levels of some circuits may be high.

The on level a of a circuit configuration according to the present disclosure may be understood as being capable of controlling the circuit configuration to be in an on state when a level a is applied to a control terminal of the circuit configuration.

In addition, the high level and the low level in the present disclosure refer to two logic states represented by a potential range of a circuit node. The specific potential range can be set as required under specific application scenarios, which is not limited by the present disclosure.

Similar to the driving module 30, the reset module 40, the first switch module 50 and the second switch module 60 of the present disclosure may be implemented by transistors. As shown in fig. 2, in an exemplary embodiment, the reset module 40 may include a reset transistor T _R Reset transistor T _R Is connected with a first voltage end V _C Reset transistor T _R Is connected to the first node A, a reset transistor T _R Is connected with a reset signal terminal RST, a reset transistor T _R Operable to reset the first voltage terminal V in response to a signal from the reset signal terminal RST _C Is transmitted to the first node a. Wherein the reset transistor T _R The transistor may be an N-type transistor, for example, an N-type oxide thin film transistor. In the reset phase, the reset signal terminal RST provides a high level signal to control the reset transistor T _R Is conducted to the first voltage terminal V _C Is conducted with the first node A, and the first voltage terminal V _C Is transmitted to the first node a, the reset of the first node a is realized.

As shown in fig. 2, in an exemplary embodiment, the first switching module 50 may include a first transistor T _VT The second switch module 60 may include a second transistor T _S A first transistor T _VT Is connected to a first node A, a first transistor T _VT Is connected to the second node B, the first transistor T _VT A gate of the first transistor T is connected with a first control signal terminal VTS _VT A first node A and a second node B which are used for responding to the signal of the first control signal terminal VTS; the second switching module 60 may include a second transistor T _S Second transistor T _S A first electrode connected to a second node B and a second transistor T _S A second pole connected to a third node C and a second transistor T _S Gate connected to the second controlSignal terminal SEN, second transistor T _S Which is operable to turn on the second node B and the third node C in response to a signal of the second control signal terminal SEN.

Wherein the first transistor T _VT And a second transistor T _S May be an N-type transistor, for example, an N-type oxide thin film transistor. A first transistor T _VT The second node B and the first node A can be conducted during the threshold compensation period, and the driving transistor T is conducted at the time _D And a first transistor T _VT Forming a transistor diode in one-way conduction, the voltage signal of the first node A passes through the transistor diode to the second voltage end V _E Discharge to make the first voltage terminal V _C When the potential of the first voltage terminal V drops _C Is reduced to be equal to the second voltage terminal V _E Voltage value of and driving transistor T _D Is the sum of the threshold voltages of the driving transistor T _D Is turned off, at this time, the transistor T is driven _D Is written into the first node a.

Second transistor T _S The current collection stage can be conducted, the second node B and the third node C are conducted, and the third node C obtains the driving current I through the conduction path _TD So that the drive current I can be obtained by other circuit structures of the ambient light detection circuit connected to the third node C _TD Equivalent to obtaining the induced current I output by the sensing module 10 _DR 。

Notably, the reset transistor T of the present disclosure _R A first transistor T _VT A second transistor T _S And a driving transistor T _D Or all the transistors can be P-type transistors, such as all the transistors are P-type low temperature polysilicon thin film transistors. Alternatively, each of the transistors is also partially an N-type transistor and partially a P-type transistor. All falling within the scope of the present disclosure.

The driving method of the current amplifying circuit 100 of the present disclosure may include four stages, a reset stage t1, a threshold compensation stage t2, an integration stage t3, and a current collection stage t 4. FIG. 3 is a timing diagram of each node of the current amplifying circuit in FIG. 2, where RST represents the timing of the reset signal terminal and VTS is the first control signal terminalTime sequence, V _A Representing the timing of the first node, and SEN representing the timing of the second control signal terminal.

In the reset phase T1, the reset signal terminal RST is at a high level, the first control terminal signal terminal VTS and the second control terminal SEN are both at a low level, fig. 4 is an equivalent circuit diagram of the current amplifying circuit in fig. 2 in the reset phase, and as shown in fig. 4, the reset transistor T is _R The conducted reset module 40 enables the first voltage terminal V to be conducted _C Is transmitted to the first node A by using the first voltage terminal V _C Resets the first node a.

In the threshold compensation stage T2, the first control terminal VTS is at a high level, the reset signal terminal RST and the second control signal terminal SEN are both at a low level, fig. 5 is an equivalent circuit diagram of the current amplifying circuit in fig. 2 in the threshold compensation stage, as shown in fig. 5, the first transistor T is connected to the second transistor T _VT Is turned on so that the first transistor T _VT The first node A and the second node B are turned on because the first node A and the first voltage terminal V are connected _C Equipotential, and first voltage terminal V _C Is higher than the driving transistor T _D And a second voltage terminal V _E Thus, the driving transistor T _D Is turned on to drive the transistor T _D And a first transistor T _VT Form a diode circuit which is conducted in one direction, so that the first node A is conducted to the second voltage terminal V through the diode circuit _E Discharging is carried out, the potential of the first node A begins to fall, and when the voltage of the first node A falls to the driving transistor T _D And a second voltage terminal V _E Is the same, the transistor T is driven _D Off, when the voltage at the first node A (i.e. the driving transistor T) _D Gate voltage of) is a second voltage terminal V _E And a driving transistor T _D I.e. (VA = VE + Vth), thereby driving the transistor T _D Is written into the storage capacitor Cst.

In the integration phase t3, the reset signal terminal RST, the first control signal terminal VTS and the second control signal terminal SEN are all at low level. FIG. 6 is the equivalent of the current amplifying circuit in FIG. 2 in the integration stageIn the circuit diagram, as shown in fig. 6, the reset transistor TR, the first transistor TVT and the second transistor TS are all turned off, and the sensing module 10 provides the sensing current I _DR The storage capacitor Cst is charged, and the storage capacitor Cst accumulates electric quantity to raise the potential of the first node a, that is, the voltage of the first node a starts to rise. Obviously, the voltage rise of the first node A is induced by the induced current I _DR The amount of charge of the storage capacitor Cst.

Specifically, the voltage of the first node A is represented by (V) _E + Vth) begins to rise, and the charging time period (i.e. the integration time period) is set to T, the induced current I _DR The charge generated by the charging is:

ΔQ＝I _DR *T

accordingly, after the integration time T, the charge amount on the storage capacitor Cst is:

Qc＝Cst*(V _E +Vth-V _E )+I _DR *T＝Cst*Vth+I _DR *T

after integration, the voltage on the storage capacitor Cst is:

V _Cst ＝(Cst*Vth+I _DR *T)/Cst＝Vth+I _DR *T/Cst

the voltage variation of the first node a (i.e., the driving transistor T) _D Voltage variation of the gate) is:

ΔVA＝I _DR *T/Cst

as can be appreciated, the drive transistor T _D Has a certain variation range in order to ensure the photoelectric sensor D _ALS Charging the capacitor during the integration phase t3 does not go into saturation, and therefore V _C >V _E +Vth+D _R -V _R Wherein D is _R For driving a transistor T _D Maximum variation range of gate voltage, V _R Is the minimum reverse bias voltage value of the photosensor.

In the current collection phase t4, the second control signal end SEN is at a high level, and the reset signal end RST and the first control signal end VTS are both at a low level. FIG. 7 is an equivalent circuit diagram of the current amplifying circuit in FIG. 2 at the current collecting stage, as shown in FIG. 7, the second transistor T _S The second node B is communicated with the third node C through conduction, so that other circuit structures of the ambient light detection circuit connected with the third node C can acquire the driving current I _TD Equivalent to obtaining the induced current I _DR 。

In the current collection stage, the current passes through a photoelectric sensor D _ALS After discharge, the transistor T is driven _D Gate-source voltage of (d):

Vgs＝V _Cst ＝Vth+I _DR *T/Cst

accordingly, the transistor T is driven _D Drive current I of _TD Comprises the following steps:

wherein μ is the carrier mobility; cox is the amount of gate capacitance per unit area C, W is the width of the drive transistor channel, L is the length of the drive transistor channel, vgs is the difference in gate-source voltage of the drive transistor, and Vth is the threshold voltage of the drive transistor.

I _TD I.e. the amplified current outputted by the current amplifying circuit 100, it is obvious that the current is compared with the photo sensor D _ALS Output induced current I _DR Is amplified.

The present disclosure also provides an ambient light detecting circuit that outputs a voltage signal of a corresponding magnitude by detecting ambient light, and a display panel may perform automatic adjustment of display luminance based on the voltage signal. Fig. 8 is a schematic diagram illustrating a configuration of an ambient light sensing circuit according to an embodiment of the disclosure, and as shown in fig. 8, the ambient light sensing circuit may include the current amplifying circuit 100 according to any of the above embodiments of the disclosure, and further, the ambient light sensing circuit may further include a current converting circuit 200, a filter circuit 300, and an analog-to-digital converting circuit 400, wherein the current converting circuit 200 is connected to a third node C and a fourth node D, and the current converting circuit 200 may be configured to convert the driving current I output by the current amplifying circuit 100 into the driving current I _TD Converting the voltage into an induction voltage and outputting the induction voltage to the fourth node D; the filter circuit 300 is connected to the output terminal of the current converting circuit 200, and the filter circuit 300 can be used to low pass filter the induced voltage and output it. The analog-to-digital conversion circuit 400 is connected to the output end of the filter circuit 300, and the analog-to-digital conversion circuit 400 is configured to convert the acquired sensing voltage into a digital voltage signal for output.

The present disclosure provides an ambient light detection circuit, a current amplification circuit 100 capable of converting ambient light into an induced current I _DR And to the induced current I _DR After amplifying and outputting, the current converting circuit 200 can obtain the amplified induced current I _DR The data voltage signal is converted into an induced voltage, and then low-pass filtered by the filter circuit 300 and output to the analog-to-digital conversion circuit 400 for analog-to-digital conversion to output a digital voltage signal.

As shown in fig. 8, in an exemplary embodiment, the current converting circuit 200 may include a signal amplifying unit 210, a gain control unit 220, and a feedback unit 230, wherein one input terminal of the signal amplifying unit 210 is connected to the reference voltage terminal, another input terminal of the signal amplifying unit 210 is connected to the third node C, and an output terminal is connected to the fourth node D. The gain control unit 220 has a gain coefficient, one end of the gain control unit 220 is connected to the third node C, and the other end is connected to the output end of the signal amplification unit 210, and the gain control unit 220 is configured to determine the induced voltage according to the gain coefficient. The feedback unit 230 is connected in parallel to two ends of the gain control unit 220, and the feedback unit 230 can be used to prevent the signal amplification unit 210 from self-exciting, and increase the stability of the signal amplification unit 210.

The signal amplifying unit 210 may include an operational amplifier OP, one input terminal of the operational amplifier OP is connected to the reference voltage terminal, another input terminal of the operational amplifier OP is connected to the third node C, and an output terminal of the operational amplifier OP is connected to the fourth node D. The gain control unit 220 may include a gain resistor Rg. Obviously, the gain factor of the gain control unit 220 is determined by the size of the gain resistor Rg, and the amplification factor of the induced voltage can be adjusted by reasonably configuring the size of the gain resistor Rg. The feedback unit 230 may include a feedback capacitor CF connected in parallel to two ends of the gain resistor Rg, which may prevent the OP-amp OP from self-exciting.

In addition, the minimum value of the gain resistor Rg can generate the maximum induced current I in the sensing module 10 according to the maximum brightness of the ambient light _DR And the output voltage range of the operational amplifier OP in the current conversion circuit 200.

It is understood that in some embodiments, the number of gain control units 220 may be multiple, that is, the current conversion module may have multiple gain control units 220, and the gain factor of each gain control unit 220 may be different, so that the current conversion circuit 200 has different gain steps.

As shown in fig. 8, in an exemplary embodiment, the filter circuit 300 may include a filter resistor RS and a filter capacitor CS, one end of the filter resistor RS is connected to a first end of the filter unit, and the other end of the filter resistor RS is connected to a second end of the filter unit; one end of the filter capacitor CS is connected to the second end of the filter unit, and the other end of the filter capacitor CS is grounded. The filter resistor RS and the filter capacitor CS form a low-pass filter, and perform low-pass filtering on the induced voltage output by the current conversion circuit 200.

As shown in fig. 8, in an exemplary embodiment, the analog-to-digital conversion circuit 400 may be an integrated device, for example, an analog-to-digital conversion chip, and the sampling precision of the analog-to-digital conversion circuit 400 needs to match the usage requirement of the display device, and the detailed process and principle of the analog-to-digital conversion circuit 400 are not described in detail herein.

The present disclosure also provides a display panel, which may include the ambient light detection circuit according to any embodiment of the present disclosure, and the display panel may automatically adjust display brightness based on an induced voltage signal output by the ambient light detection circuit.

Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.

Claims

1. A current amplifying circuit for detecting ambient light of a display panel, the current amplifying circuit comprising:

the sensing module is connected with a first node and a first voltage end, and is used for collecting ambient light and responding to the voltage difference between the first node and the first voltage end to output an induced current based on the ambient light;

the first end of the storage module is connected with the first node, the second end of the storage module is connected with the second voltage end, and the storage module is used for storing electric quantity by utilizing the induction current and converting the stored electric quantity into a voltage signal to be coupled to the first node;

the driving module is used for responding to voltage signals of the first node and the second voltage end and providing driving current for the second node, wherein the driving current increases along with the increase of the voltage of the first node.

2. The current amplifying circuit according to claim 1, wherein the storage module comprises:

a first pole of the storage capacitor is connected with the first node, and a second pole of the storage capacitor is connected with the second voltage end;

the driving module includes:

and the first pole of the driving transistor is connected with the second voltage end, the second pole of the driving transistor is connected with the second node, the grid of the driving transistor is connected with the first node, and the driving transistor is used for responding to a voltage signal of the first node to provide driving current for the second node.

3. The current amplifying circuit according to claim 2, wherein the driving transistor is an N-type transistor.

4. The current amplifying circuit according to claim 3, wherein a voltage difference between the first voltage terminal and the second voltage terminal is greater than a threshold voltage of the driving transistor.

5. The current amplifying circuit of claim 3, wherein the voltage difference between the first voltage terminal and the second voltage terminal is greater than the sum of the threshold voltage of the driving transistor, the minimum bias voltage of the sensing module, and the gate dynamic voltage range of the driving transistor.

6. The current amplifying circuit according to claim 2, wherein the voltage of the second voltage terminal satisfies the following relationship:

in the formula: v _E Representing the voltage value, V, of the second voltage terminal _B Representing the second node voltage, I _DR(Max) Maximum induced current, T, generated by the induction module _Max Indicating the maximum charging time period for the storage capacitor and Cst indicating the capacitance of the storage capacitor.

7. The current amplifying circuit according to claim 1, wherein the current amplifying circuit further comprises:

a reset module, having a first end connected to the first voltage end, a second end connected to the first node, and a control signal end connected to a reset signal end, wherein the reset module is configured to transmit a voltage signal of the first voltage end to the first node in response to a signal of the reset signal end to reset the first node;

a first switch module, a first end of which is connected to the first node, a second end of which is connected to the second node, and a control signal end of which is connected to a first control signal end, wherein the first switch module is used for responding to a signal of the first control signal end to conduct the first node and the second node;

and the first end of the second switch module is connected with the second node, the second end of the second switch module is connected with the third node, the control signal end of the second switch module is connected with the second control signal end, and the second switch module is used for responding to a signal of the second control signal end to transmit the driving current to the third node.

8. The current amplifying circuit according to claim 7, wherein the conduction level of the reset module, the conduction level of the first switch module, and the conduction average of the second switch module are the same polarity as the conduction level of the driving module.

9. The current amplifying circuit according to claim 8,

the reset module includes:

a reset transistor, having a first electrode connected to the first voltage terminal, a second electrode connected to the first node, and a gate connected to the reset signal terminal, the reset transistor being configured to transmit a voltage signal of the first voltage terminal to the first node in response to a signal of the reset signal terminal;

the first switch module includes:

a first transistor, having a first electrode connected to the first node, a second electrode connected to the second node, and a gate connected to the first control signal terminal, the first transistor being configured to turn on the first node and the second node in response to a signal of the first control signal terminal;

the second switch module includes:

and a second transistor having a first electrode connected to the second node, a second electrode connected to the third node, and a gate connected to the second control signal terminal, the second transistor being configured to turn on the second node and the third node in response to a signal of the second control signal terminal.

10. The current amplification circuit according to claim 9, wherein the reset transistor, the first transistor, and the second transistor are all N-type transistors.

11. A driving method of a current amplification circuit for driving the current amplification circuit according to any one of claims 1 to 10, the driving method comprising:

in an integration phase, the storage module stores electric quantity by using the induction current and converts the stored electric quantity into voltage to be coupled to the first node;

in a current collection phase, the driving module outputs a driving current in response to the voltage signal of the first node, wherein the driving current increases as the voltage of the first node increases.

12. An ambient light detection circuit, comprising:

the current amplifying circuit of any one of claims 1-10;

the current conversion circuit is connected with a third node and a fourth node and is used for converting the driving current output by the current amplification circuit into induction voltage and outputting the induction voltage to the fourth node;

the filter circuit is connected with the output end of the current conversion circuit and is used for outputting the induction voltage after low-pass filtering;

and the analog-to-digital conversion circuit is connected to the output end of the filter circuit and is used for converting the acquired induction voltage into a digital voltage signal to be output.

13. The ambient light detection circuit of claim 12, wherein the current conversion circuit comprises:

one input end of the signal amplification unit is connected with a reference voltage end, the other input end of the signal amplification unit is connected with the third node, and the output end of the signal amplification unit is connected with the fourth node;

and the gain control unit is provided with a gain coefficient, one end of the gain control unit is connected with the third node, the other end of the gain control unit is connected with the output end of the signal amplification unit, and the gain control unit is used for determining the induction voltage according to the gain coefficient.

14. The ambient light detection circuit of claim 13, wherein the current conversion circuit further comprises:

and the feedback unit is connected in parallel with two ends of the gain control unit and is used for preventing the signal amplification unit from self-exciting.

15. The ambient light detection circuit according to claim 14, wherein the gain control unit comprises a gain resistor;

the signal amplification unit comprises an operational amplifier, one input end of the operational amplifier is connected with the reference voltage end, the other input end of the operational amplifier is connected with the third node, and the output end of the operational amplifier is connected with the fourth node;

the feedback unit comprises a feedback capacitor, and the feedback capacitor is connected in parallel to two ends of the gain resistor.

16. The ambient light detection circuit of claim 12, wherein the filter circuit comprises:

one end of the filter resistor is connected with the first end of the filter unit, and the other end of the filter resistor is connected with the second end of the filter unit;

and one end of the filter capacitor is connected with the second end of the filter unit, and the other end of the filter capacitor is grounded.

17. A display panel comprising the ambient light detection circuit of any one of claims 12 to 16.