US-12620346-B2 - Display device with driving current modulation using pulse amplitude modulation and pulse width modulation

US12620346B2US 12620346 B2US12620346 B2US 12620346B2US-12620346-B2

Abstract

According to an aspect of the present disclosure, a display device includes a display panel in which a plurality of pixel groups is defined; one PAM circuit disposed in each of the plurality of pixel groups; a plurality of PWM circuits which is disposed in each of the plurality of pixel groups and is connected to one PAM circuit; a plurality of light emitting diodes which is disposed in each of the plurality of pixel groups and is connected to the plurality of PWM circuits. The plurality of PWM circuits is connected to an output terminal of one PAM circuit in parallel in each of the plurality of pixel groups. Accordingly, the plurality of PWM circuits shares one PAM circuit to reduce the number of overall transistors and simplify the structure of the display device.

Inventors

Jaemin Park
JongBeom Lee
Soyi Lee
Seeun Kim

Assignees

LG DISPLAY CO., LTD.

Dates

Publication Date: 20260505
Application Date: 20241010
Priority Date: 20231127

Claims (20)

1 . A display device, comprising: a display panel including a plurality of pixel groups, each of the plurality of pixel groups including a plurality of light emitting diodes; a plurality of pulse amplitude modulation (PAM) circuits, each of the plurality of pixel groups including a respective PAM circuit; and a set of pulse width modulation (PWM) circuits, wherein a corresponding plurality of PWM circuits from the set are included in each of the plurality of pixel groups, a set of light emitting diodes of the plurality of light emitting diodes within the corresponding plurality of PWM circuits receiving a driving current from the respective PAM circuit, wherein in each of the plurality of pixel groups, the corresponding plurality of PWM circuits are connected in parallel to an output terminal of the respective PAM circuit.
2 . The display device according to claim 1 , wherein a PAM circuit from the plurality of PAM circuits is configured to adjust an intensity of the driving current that drives the plurality of light emitting diodes that are included in the pixel group that is connected to the PAM circuit based on a first data voltage.
3 . The display device according to claim 2 , wherein the first data voltage is applied to the plurality of pixel groups.
4 . The display device according to claim 3 , wherein the PAM circuit is configured to supply the driving current with a same intensity to the plurality of PWM circuits that is connected to the PAM circuit.
5 . The display device according to claim 2 , wherein each of the plurality of PWM circuits that is connected to the PAM circuit is configured to adjust a pulse width of the driving current output from the PAM circuit based on a second data voltage.
6 . The display device according to claim 5 , wherein the second data voltage that is applied to each of the plurality of PWM circuits in the set is based on a gray scale level of an image.
7 . The display device according to claim 5 , further comprising: a plurality of emission control transistors, each emission control transistor connected to the PAM circuit and a PWM circuit from the corresponding plurality of PWM circuits that are connected to the PAM circuit, wherein each emission control transistor is configured to connect or disconnect a driving current path between the PAM circuit and the corresponding plurality of PWM circuits.
8 . The display device according to claim 7 , further comprising: a plurality of emission control lines connected to gate electrodes of the plurality of emission control transistors, wherein each of the plurality of emission control transistors is connected to a different emission control line from the plurality of emission control lines.
9 . The display device according to claim 7 , wherein the PAM circuit includes a first driving transistor that controls the intensity of the driving current based on the first data voltage and each of the plurality of PWM circuits includes a second driving transistor that controls a time to supply the driving current to the plurality of light emitting diodes based on the second data voltage.
10 . The display device according to claim 9 , wherein an emission period of each of the plurality of light emitting diodes in the pixel group is a same as a period during which second driving transistors of the corresponding plurality of PWM circuits and the plurality of emission control transistors are turned on.
11 . The display device according to claim 9 , wherein the PAM circuit further comprises a first sensing transistor that is connected to the first driving transistor of the PAM circuit and each of the corresponding plurality of PWM circuits further includes a second sensing transistor that is connected to the second driving transistor that is included in the PWM circuit.
12 . The display device according to claim 11 , further comprising: a plurality of third sensing transistors, each third sensing transistor connected to a corresponding second driving transistor from the corresponding plurality of PWM circuits and supplying a sensing voltage to the corresponding second driving transistor, wherein any one of a source electrode and a drain electrode of each first driving transistor is connected to a high potential power line and the other of the source electrode and the drain electrode of the first driving transistor is connected to the first sensing transistor, and any one of a source electrode and a drain electrode of the second driving transistor is connected to the third sensing transistor and the other of the source electrode and the drain electrode of the second driving transistor is connected to the second sensing transistor.
13 . The display device according to claim 9 , wherein the PAM circuit further comprises: a first capacitor having a first end connected to a gate electrode of the first driving transistor and a second end; a first switching transistor that is connected to the second end of the first capacitor, the first switching transistor transmitting the first data voltage to the first capacitor; and a second switching transistor that is connected to any one of a source electrode and a drain electrode of the first driving transistor and the gate electrode of the first driving transistor, the second switching transistor is configured to be turned on and diode-connect the first driving transistor.
14 . The display device according to claim 13 , wherein each of the corresponding plurality of PWM circuits further includes: a second capacitor having a first end connected to a gate electrode of the second driving transistor; a fifth switching transistor that is connected to the second driving transistor, the fifth switching transistor transmitting the second data voltage to the second driving transistor; and a sixth switching transistor that is connected to any one of a source electrode and a drain electrode of the second driving transistor and the gate electrode of the second driving transistor, the sixth switching transistor configured to be turned on and diode-connect the second driving transistor.
15 . A display device comprising: a plurality of light emitting elements that emit a same color of light; a pulse amplitude modulation (PAM) circuit, the PAM including a first driving transistor that controls an intensity of a driving current that is generated by the PAM circuit based on a first data voltage; and a plurality of pulse width modulation (PWM) circuits that are electrically connected to the PAM circuit and receive the driving current generated by the PAM circuit, wherein a set of light emitting elements of the plurality of light emitting elements within the plurality of PWM circuits receive the driving current from the PAM circuit, and wherein each of the PWM circuits includes a second driving transistor that is connected to a corresponding light emitting element from the plurality of light emitting elements and controls a duration of time that the driving current from the PAM circuit is supplied to the corresponding light emitting element based on a second data voltage that has a magnitude that is image dependent.
16 . The display device of claim 15 , wherein the first data voltage has a constant value.
17 . The display device of claim 16 , wherein the second data voltage has a first magnitude that corresponds to a first image at a first time such that the driving current is supplied to the second driving transistor for a first duration and the second data voltage has a second magnitude that corresponds to a second image at a second time such that the driving current is supplied to the second driving transistor for a second duration that is different from the first duration.
18 . The display device of claim 15 , further comprising: a plurality of emission control transistors, each emission control transistor connected to the PAM circuit and a corresponding PWM circuit from the plurality of PWM circuits, wherein each emission control transistor is configured to connect or disconnect the PAM circuit from the corresponding PWM circuit.
19 . The display device according to claim 18 , further comprising: a plurality of emission control lines connected to gate electrodes of the plurality of emission control transistors, wherein each of the plurality of emission control transistors is connected to a different emission control line from the plurality of emission control lines.
20 . The display device according to claim 18 , wherein the first driving transistor includes a gate electrode, a first electrode, and a second electrode that is connected to each of the plurality of emission control transistors, and the PAM circuit further comprises: a first switching transistor including a gate electrode that receives a first scan signal, a first electrode that receives the first driving voltage, and a second electrode connected to the gate electrode of the first driving transistor, the first switching transistor configured to supply the first driving voltage to the gate electrode of the first driving transistor responsive to the first scan signal; a first sensing transistor including a gate electrode that receives a sensing signal, a first electrode that is connected to the second electrode of the first driving transistor and each of the plurality of emission control transistors, and a second electrode that is connected to a reference line; and a first capacitor connected to the gate electrode of the first driving transistor and the second electrode of the first driving transistor.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the priority of Republic of Korea Patent Application No. 10-2023-0166454 filed on Nov. 27, 2023, which is hereby incorporated by reference in its entirety. BACKGROUND Field The present disclosure relates to a display device and more particularly, to a display device which simplifies a structure of a pixel circuit. Description of the Related Art As display devices which are used for a monitor of a computer, a television, a cellular phone, or the like, there are an organic light emitting display (OLED) device which is a self-emitting device, a liquid crystal display (LCD) device which requires a separate light source, and the like. An applicable range of the display device is diversified to personal mobile devices as well as monitors of computers and televisions and a display device with a large display area and a reduced volume and weight is being studied. In the meantime, various types of display elements may be used for the display device and in recent years, a light emitting diode (LED) or a micro-LED (micro light-emitting diode) which is formed of an inorganic material to have a high reliability and excellent luminous efficiency is being used. Further, a pixel circuit which drives the LED is configured by a pulse amplitude modulation (PAM) method which expresses a gray scale level with an amplitude of a driving current and/or a pulse width modulation (PWM) method which expresses a gray scale level with a pulse width of a driving current. SUMMARY An object to be achieved by the present disclosure is to provide a display device in which a plurality of sub pixels shares one PAM circuit to reduce the number of transistors. Another object to be achieved by the present disclosure is to provide a display device in which the number of transistors disposed in each of the plurality of sub pixels is reduced to reduce a design area of each sub pixel. Still another object to be achieved by the present disclosure is to provide a display device in which a design area of each of a plurality of sub pixels is reduced to implement a high resolution. Still another object to be achieved by the present disclosure is to provide a display device in which color coordinate distortion of a light emitting diode in a low current band is minimized. Still another object to be achieved by the present disclosure is to provide a display device in which an emission timing of each of a plurality of sub pixels which shares a PAM circuit may be individually controlled. Still another object to be achieved by the present disclosure is to provide a display device which compensates for a threshold voltage of a driving transistor of each of a PAM circuit and a PWM circuit using an external compensation method. Still another object to be achieved by the present disclosure is to provide a display device which compensates for a threshold voltage of a driving transistor of each of a PAM circuit and a PWM circuit using an internal compensation method. Objects of the present disclosure are not limited to the above-mentioned objects, and other objects, which are not mentioned above, can be clearly understood by those skilled in the art from the following descriptions. In order to achieve the objects as described above, according to an embodiment of the present disclosure, a display device comprises: a display panel including a plurality of pixel groups, each of the plurality of pixel groups including a plurality of light emitting diodes; a plurality of pulse amplitude modulation (PAM) circuits, each PAM circuit connected to one pixel group from the plurality of pixel groups; a set of pulse width modulation (PWM) circuits, wherein a corresponding plurality of PWM circuits from the set are included in each of the plurality of pixel groups and are connected to the PAM circuit that is connected to the pixel group and connected to the plurality of light emitting diodes that are included in the pixel group, wherein in each of the plurality of pixel groups, the corresponding plurality of PWM circuits are connected in parallel to an output terminal of the PAM circuit that is connected to the pixel group. Accordingly, the plurality of PWM circuits shares one PAM circuit to reduce the number of overall transistors and simplify the structure of the display device. In one embodiment, a display device comprises: a plurality of light emitting elements that emit a same color of light; a pulse amplitude modulation (PAM) circuit, the PAM including a first driving transistor that controls an intensity of a driving current that is generated by the PAM circuit based on a first data voltage; and a plurality of pulse width modulation (PWM) circuits that are electrically connected to the PAM circuit and receive the driving current generated by the PAM circuit, each of the PWM circuits including a second driving transistor that is connected to a corresponding light emitting element from the plurality of light emitt