Patent Grant
12131689
The present invention relates generally to a display device, and more particularly, to a display device able to realize both display and sensing functions in the same pixel circuit to provide an in-screen sensing function.
In general, a display device often only has a display function. Some display devices provides both display and touch functions. However, when sensing is required, for example, when an optical fingerprint sensor (OFPS) is used for sensing, the optical fingerprint sensor will need to be implemented as an independent device. In addition, when the optical sensing module is bonded under the display device, there will be additional cost, additional thickness, and additional yield risk during bonding.
Moreover, since the sensing area depends on the area of the sensor, the sensing area will be much smaller than the area of the entire panel. In addition, since the optical sensing module is attached to the bottom of the display device, components between the sensed object and the sensor may block the light.
Therefore, it is necessary to provide a display device that can integrate the sensing function and the display function in the same pixel circuit to overcome the above problems.
In order to achieve the objective of effectively solving the above problems, the present invention provides a display device, including: a plurality of sub-pixel areas, each including a pixel circuit, each pixel circuit including: a diode, configured to a forward-biasing state in a display phase of the pixel circuit for emitting light and configured to a reverse-biasing state in a sensing phase of the pixel circuit for generating a sensing voltage; a driving transistor, for driving the diode in the display phase; first to fifth transistors, gates of the first to fifth transistors being respectively applied with first to fifth gate control signals, so that the first to fifth transistors switching between the display phase and the sensing phase; and a storage capacitor, for storing a data voltage to be written to the diode in the display phase; a first circuit, by applying the five gate control signals to each pixel circuit to switch each pixel circuit between the display phase and the sensing phase respectively; and a second circuit, for applying the data voltage, a driving voltage, and a common voltage, the second circuit including a plurality of readout circuits, and each readout circuit including: an operational amplifier for reading out the sensing voltage in the sensing phase.
Preferably, each readout circuit is connected and corresponds to a plurality of pixel circuits in a same column to amplify and read out the sensing voltage in the pixel circuits in the column.
Preferably, in each pixel circuit, a first electrode of the first transistor is connected to the driving voltage, a second electrode of the first transistor is connected to a first node, a first electrode of the second transistor is connected to the first node, a second electrode of the second transistor is connected to a second node, a first electrode of the third transistor is applied with the data voltage, and a second electrode of the third transistor is connected to a third node, a first electrode of the fourth transistor is connected to the third node, a second electrode of the fourth transistor is connected to a fourth node, a first electrode of the fifth transistor is connected to the fourth node, a second electrode of the fifth transistor is connected to a fifth node of the readout circuit, and a gate electrode of the driving transistor is connected to the second node, a first electrode of the driving transistor is connected to the first node, a second electrode of the driving transistor is connected to the fourth node, and a first electrode of the diode is connected to the fourth node, a second electrode of the diode is applied with the common voltage, and both ends of the storage capacitor are connected to the second node and the third node respectively.
Preferably, each readout circuit further includes: a readout transistor, whose first electrode is connected to the fifth node, a second electrode is applied with a first readout voltage, and a gate is applied with a sixth gate control signal; a first capacitor with two ends connected to the fifth node and a sixth node respectively; a second capacitor with both ends connected to the sixth node and an output end of the operational amplifier respectively; a third capacitor with one end connected to the sixth node and the other end is applied with a second readout voltage; and an amplifier switch with one end connected to the output end of the operational amplifier and one end connected to the sixth node, wherein a positive terminal of the operational amplifier is connected to a reference voltage and a negative terminal is connected to the sixth node for outputting an amplified voltage at the output end according to the sensing voltage, the first capacitor, and the second capacitor in the sensing phase.
Preferably, the sensing phase includes: a first sensing phase, for initializing the diode so that the diode is in the reverse-biasing state; a second sensing phase, for making the diode accumulate charge at the fourth node; and a third sensing phase, for storing the sensing voltage into the first capacitor and using the operational amplifier to read out the sensing voltage.
Preferably, in the first sensing phase: the first to sixth gate control signals respectively control the first to fifth transistors and the readout transistor, so that the second transistor, the third transistor, the fifth transistor, and the readout transistor are on, and the first transistor and the fourth transistor are off; the amplifier switch remains on, the first readout voltage is a negative voltage, the data voltage is the negative voltage, and the second readout voltage is a ground level that is the same as the common voltage; in the second sensing phase: the first to sixth gate control signals control the first to fifth transistors and the readout transistor respectively, so that the fourth transistor and the readout transistor are on, the first transistor, and the second transistor, the third transistor, and the fifth transistor are off; the amplifier switch remains on, the first readout voltage is the negative voltage, and the data voltage is at the ground level, and the second readout voltage is at the ground level; in the third sensing phase: the first to sixth gate control signals control the first to fifth transistors and the readout transistor respectively, so that the first transistor changes from off to on at a second time point after a first time point, causing the second transistor to be off, causing the third transistor to be on, causing the fourth transistor to be off, causing the fifth transistor to be on, and causing the readout transistor to be turned off; and the amplifier switch changes from on to off at the first time point, the first readout voltage is the negative voltage, and the data voltage is at the ground level, and the second readout voltage changes from the ground level to the negative voltage at the second time point.
Preferably, the display phase includes: a 1-1 display phase, for pre-charging the pixel circuit; a 1-2 display phase, for writing the data voltage; a 1-3 display phase, for preparing the diode to emit light; and a second sensing phase, for making the diode emit light according to the data voltage.
Preferably, in the 1-1 display phase, the first to sixth gate control signals control the first to fifth transistors and the readout transistor respectively, so that the first transistor, the second transistor, the third transistor, the fifth transistor, and the readout transistor are on, and the fourth transistor is off; in the 1-2 display phase, the first to sixth gate control signals control the first to fifth transistors and the readout transistor respectively, so that the second transistor, the third transistor, the fifth transistor, and the readout transistor are on, and the first transistor and the fourth transistor are off; in the 1-3 display phase, the first to sixth gate control signals control the first to fifth transistors and the readout transistor respectively, so that the readout transistor is on, and the first transistor, the second transistor, the third transistor, the fourth transistor, and the fifth transistor are turned off; in the second display phase, the first to sixth gate control signals control the first to fifth transistors and the readout transistor respectively, so that the first transistor, the fourth transistor, and the readout transistor are on, and the second transistor, the third transistor, and the fifth transistor are off; during the second display phase, the amplifier switch remains on, the first readout voltage is at a ground level, and the second readout voltage is at a ground level that is the same as the common voltage.
Preferably, the diode includes one of a micro light-emitting diode, a sub-millimeter light-emitting diode, and an organic light-emitting diode.
Preferably, the transistors include one of or any combination of P-type metal oxide semiconductor field effect transistors (MOSFET), N-type MOSFETs, thin film transistors (TFT), low-temperature polycrystalline silicon TFTs, and low-temperature polycrystalline oxide TFTs.
The present invention will be apparent to those skilled in the art by reading the following detailed description of a preferred embodiment thereof, with reference to the attached drawings.
The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
The inventive concept will be explained more fully hereinafter with reference to the accompanying drawings in which exemplary embodiments of the inventive concept are shown. Advantages and features of the inventive concept and methods for achieving the same will be apparent from the following exemplary embodiments, which are set forth in more details with reference to the accompanying drawings. However, it should be noted that the present inventive concept is not limited to the following exemplary embodiments, but may be implemented in various forms. Accordingly, the exemplary embodiments are provided merely to disclose the inventive concept and to familiarize those skilled in the art with the type of the inventive concept. In the drawings, exemplary embodiments of the inventive concepts are not limited to the specific examples provided herein and are exaggerated for clarity.
The terminology used herein is used to describe particular embodiments only, and is not intended to limit the present invention. As used herein, the singular terms “a” and “the” are intended to include the plural forms as well, unless the context clearly dictates otherwise. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present.
Similarly, it will be understood that when an element (e.g., a layer, region, or substrate) is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present. In contrast, the term “directly” means that no intervening elements are present. It should be further understood that when the terms “comprising” and “including” are used herein, it is intended to indicate the presence of stated features, steps, operations, elements, and/or components, but does not exclude one or more other features, steps, operations, elements, components, and/or the presence or addition of groups thereof.
Furthermore, exemplary embodiments in the detailed description are set forth in cross-section illustrations that are idealized exemplary illustrations of the present inventive concepts. Accordingly, the shapes of the exemplary figures may be modified according to manufacturing techniques and/or tolerable errors. Therefore, the exemplary embodiments of the present inventive concept are not limited to the specific shapes shown in the exemplary figures, but may include other shapes that may be produced according to the manufacturing process. The regions illustrated in the figures have general characteristics and are used to illustrate specific shapes of elements. Therefore, this should not be considered limited to the scope of this creative concept.
It will also be understood that, although the terms “first,” “second,” “third,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish each element. Thus, a first element in some embodiments could be termed a second element in other embodiments without departing from the teachings of the present creation. Exemplary embodiments of aspects of the present inventive concept illustrated and described herein include their complementary counterparts. Throughout this specification, the same reference numbers or the same designators refer to the same elements.
Furthermore, example embodiments are described herein with reference to cross-sectional and/or planar views, which are illustrations of idealized example illustrations. Accordingly, deviations from the shapes shown, for example, caused by manufacturing techniques and/or tolerances, are expected. Accordingly, the exemplary embodiments should not be considered limited to the shapes of the regions shown herein, but are intended to include deviations in shapes resulting from, for example, manufacturing. Thus, the regions illustrated in the figures are schematic and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments.
It should be noted that the pixel circuit of the present invention can be implemented in any sub-pixel such as red sub-pixel, blue sub-pixel, green sub-pixel, white sub-pixel, etc., but the present invention is not limited thereto.
Refer to
It should be understood that when the circuit is actually operating, there will be switching time between each phase. For ease of understanding, in this specification, the duration of each phase includes the actual execution of the corresponding action and switching to the next phase. For example, the first display phase D1 includes the time of initializing the circuit, writing data, and switching to the second display phase D2.
Refer to
It can be understood that, according to the user's settings, at the same point in time, the pixel circuits in the display device may be in different stages. For example, the pixel circuits in different rows may be in different stages. In addition, since the sensing phase S and the display phase of the present invention are achieved by controlling the gate control signal GCS to adjust the operating sequence, the sensor of the display device can be turned on or off the sensing phase S at any time according to the user's settings and needs.
Refer to
As shown in
It should be understood that the first circuit 20 may be, for example, one of a row circuit or a column circuit. The second circuit 30 may be, for example, one of a row circuit or a column circuit, but the present invention is not limited thereto.
It should be understood that the readout circuit 40 of the present invention is respectively connected to a plurality of pixel circuits 10 in the same column. That is, one readout circuit 40 corresponds to a plurality of pixel circuits 10 in one column to read out the light sensed by the diode LEDs in the pixel circuits 10 in the column.
It should be noted that the pixel circuit 10 of the display device of the present invention is divided into a sensing phase S and a display phase by applying the gate control signal GCS. In the sensing phase S, the diode LED is under reverse-biasing to sense light as a photodiode. Then, the diode LED accumulates charges in an integral mode. Finally, the accumulated charges are amplified and read out. In the display phase, the diode LED is in forward-biasing to emit light as a light-emitting diode to display data according to the data voltage Vdata. It can be understood that the diode LED of the present invention includes, but is not limited to, micro-LEDs (micro-LEDs), sub-millimeter light-emitting diodes (mini-LEDs), and organic light-emitting diodes (OLEDs).
Refer to
As shown in
Referring to
As shown in
In the following, the circuit operation of the pixel circuit 10 and the readout circuit 40 of the present invention in the sensing phase S will be described with reference to
Specifically, referring to
Specifically, referring to
Specifically, referring to
Herein, the circuit operation of the aforementioned third sensing phase S3 is described in detail. At the beginning of the third sensing phase S3, since the third transistor T3 is on, the fourth transistor T4 is off, and the data voltage Vdata is at 0V, the third node N3 changes from (−3V+Vsig) to 0V. And due to the voltage across the storage capacitor Cst, the voltage of the second node N2 becomes the threshold voltage Vth of the driving transistor T6. And since the fifth transistor T5 is on, the readout transistor Tsw1 is off, and the voltage of the fourth node N4 is (−3V+Vsig), (−3V+Vsig) is stored in the first capacitor Csh. Next, the amplifier switch op_rst changes from on to off (i.e., open circuit) at the first time point t1; and then, at the second time point t2, the first transistor T1 turns from off to on, and the second readout voltage Vcomp changes from 0V to −3V. Therefore, the driving voltage VDD is connected to the first electrode of the driving transistor T6, so that a current flows to the fourth node N4 until the voltage of the fourth node N4 becomes 0V. Then, since Vgs of the driving transistor T6 is equal to Vth at this point, the driving transistor T6 becomes turned off. Then, because the fourth node N4 changes from (−3V+Vsig) to 0V, and due to the voltage across the first capacitor Csh, the sixth node N6 changes to 0−(−3V+Vsig), that is, 3V-Vsig. At this point, since the second readout voltage Vcomp changes from 0V to −3V and is also coupled to the negative terminal of the operational amplifier op_amp, the voltage across the first capacitor Csh becomes Vref+(3V-Vsig)+(−3V)=Vref-Vsig. Finally, according to the amplification of the operational amplifier op_amp, the obtained amplification voltage op_out is equal to Vsig*Csh/Cf. That is, the sensing voltage Vsig can be calculated from the ratio of the first capacitance Csh to the second capacitance Cf and the obtained amplified voltage op_out.
In the following, the circuit operation of the pixel circuit 10 and the readout circuit 40 of the present invention in the display phase will be described with reference to
Specifically, referring to
Specifically, referring to
Specifically, referring to
Specifically, referring to
Here, the current Iled flowing through the diode LED in the second display phase D2 is further described. In the second display phase D2, the gate-source voltage Vgs of the driving transistor T6 is equal to the voltage across the storage capacitor Cst in the 1-3 display phase D13, that is, the gate-source voltage Vgs is equal to the threshold voltage Vth minus the data voltage Vdata. For example, if Vth=1V, Vdata=−3V, then Vgs equals 1−(−3)=4V. The current I_led flowing through the diode LED will be equal to the saturation current of the driving transistor T6. That is, I_led=½k*W/L(Vgs−Vth)2. Then, the input gate source voltage Vgs is equal to the threshold voltage Vth minus the data voltage Vdata. I_led=½k*W/L((Vth−Vdata)−Vth) 2=½k*W/L(−Vdata)2, wherein k is a process parameter, and the data voltage Vdata is the information to be displayed.
As such, the pixel circuit 10 can realize that: in the sensing phase S, the diode LED is under reverse-biasing to sense light as a photodiode, and then the diode LED accumulates charges in an integral mode. Finally, the accumulated charge is amplified and read out; and in the display phase, the diode LED is under forward-biasing to emit light as a light-emitting diode to display data according to the data voltage Vdata.
It should be understood that the embodiment of the present invention uses an N-type metal oxide semiconductor (NMOS) field effect transistor as an exemplary transistor in the pixel circuit 10. However, the present invention is not limited thereto. The transistor used in the pixel circuit of the present invention can be arbitrarily implemented as P-type PMOS field effect transistor, thin film transistor (TFT), low-temperature polycrystalline silicon (LTPS) TFT, low-temperature polycrystalline oxide (LTPO) TFT, etc. In addition, as long as it complies with the inventive concept of the present invention, the transistors can also be combined arbitrarily to form the pixel circuit of the present invention. For example, some transistors are implemented as PMOS and other transistors are implemented as NMOS. Therefore, those skilled in the art can easily understand that the inventive concept of the present invention can be applied to pixel circuits using various types of transistors without being limited by the characteristics of the transistors.
Finally, the technical features of the present invention and its achievable technical effects are summarized as follows:
First, the display device of the present invention can realize both display and sensing functions in the same pixel circuit to have an in-screen sensing function.
Second, since the display device of the present invention uses the same pixel circuit to realize both display and sensing functions at the same time, there is no element between the sensed object and the sensor that will block the light. Therefore, the present invention can achieve more accurate sensing.
Third, since the display device of the present invention uses the same pixel circuit to achieve both display and sensing functions, the total thickness of the screen is thinner, redundant manufacturing processes are not required, and the yield risk caused by additional bonding is reduced.
Although the present invention has been described with reference to the preferred embodiments thereof, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims.
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