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KR-20260063091-A - Pixel driving circuit of display panel

KR20260063091AKR 20260063091 AKR20260063091 AKR 20260063091AKR-20260063091-A

Abstract

A pixel driving circuit of a display panel according to an embodiment of the present invention comprises: a first transistor connected between a first driving voltage and a third node, with a gate electrode connected to the first node; a second transistor connected between a second node and the third node, with a gate electrode connected to a first scanning line; a third transistor connected between the third node and a fourth node, with a gate electrode connected to a light emission control line; a fourth transistor connected between the first driving voltage and the first node, with a gate electrode connected to the first scanning line; a fifth transistor connected between the second node and the second driving voltage, with a gate electrode connected to the first scanning line; a sixth transistor connected between the second node and the second driving voltage, with a gate electrode connected to the second scanning line; a seventh transistor connected between a data line and the second node, with a gate electrode connected to the second scanning line, and transmitting or blocking a data voltage; a first storage capacitor connected between the first node and the second node; and a second storage capacitor connected between the second node and the fourth node. The feature is that it includes an organic light-emitting diode connected between the fourth node and the second driving voltage.

Inventors

  • 문국철
  • 한원희
  • 백기현

Assignees

  • 주식회사 에이피에스

Dates

Publication Date
20260507
Application Date
20241030

Claims (11)

  1. A first transistor connected between a first driving voltage and a third node, with its gate electrode connected to the first node; A second transistor connected between the second node and the third node, with its gate electrode connected to the first scanning line; A third transistor connected between the third and fourth nodes, with its gate electrode connected to a light emission control line; A fourth transistor connected between the first driving voltage and the first node, with its gate electrode connected to the first scanning line; A fifth transistor connected between the second node and the second driving voltage, with its gate electrode connected to the first scanning line; A sixth transistor connected between the second node and the second driving voltage, with its gate electrode connected to the second scanning line; A seventh transistor connected between the data line and the second node, with its gate electrode connected to the second scan line, and which transmits or blocks the data voltage; A first storage capacitor connected between the first node and the second node; A second storage capacitor connected between the second node and the fourth node; and A pixel driving circuit of a display panel comprising an organic light-emitting diode connected between the fourth node and the second driving voltage.
  2. In paragraph 1, A pixel driving circuit of a display panel characterized in that the first transistor is composed of an LDD (Lightly Doped Drain) N-type LTPS TFT.
  3. In paragraph 1, A pixel driving circuit of a display panel characterized in that the second to seventh transistors are composed of NMOS-based source follower type TFTs.
  4. In paragraph 1, A pixel driving circuit of a display panel characterized by a seventh transistor receiving a data signal and a second transistor receiving a threshold voltage (V T ) of the first transistor being connected in series between the first storage capacitor and the second storage capacitor.
  5. In paragraph 1, A pixel driving circuit of a display panel characterized in that when a first scanning signal is input to the fourth transistor through a first scanning line and a first driving voltage is applied, the fourth transistor is turned on to initialize the first storage capacitor through a first node, and when a second driving voltage is applied while the light emission control signal transmitted through the light emission control line is high and the second scanning signal is low, the second transistor, the third transistor, and the fifth transistor are turned on to initialize the second storage capacitor through the second node, the third node, and the fourth node.
  6. In paragraph 1, A pixel driving circuit of a display panel characterized in that, when a first driving voltage is applied and the first scanning signal is input as high so that the first transistor, the second transistor, the fourth transistor, and the fifth transistor are in a turned-on state, and when a second driving voltage is applied and the second scanning signal and the light emission control signal are input as low so that the third transistor, the sixth transistor, and the seventh transistor are in a turned-off state, the threshold voltage of the first transistor is stored in the first storage capacitor.
  7. In paragraph 6, A pixel driving circuit of a display panel characterized in that when the threshold voltage of a first transistor is stored in the first storage capacitor, the second node and the third node have a voltage value obtained by subtracting the threshold voltage of the first transistor from the first driving voltage.
  8. In paragraph 1, A pixel driving circuit of a display panel characterized in that when a first driving voltage is applied and the first scanning signal is input as low so that the first transistor, the second transistor, the third transistor, and the fourth transistor are in a turn-off state, and when a second driving voltage is applied and the second scanning signal is input as high so that the light emission control signal is input as low so that the fifth transistor, the sixth transistor, and the seventh transistor are in a turn-on state, when a data voltage is applied to the seventh transistor, the data voltage and the threshold voltage of the first transistor are stored in the first storage capacitor.
  9. In paragraph 8, A pixel driving circuit of a display panel characterized in that, when a data voltage and a threshold voltage of a first transistor are stored in the first storage capacitor, the first node has a voltage value obtained by adding the data voltage and the threshold voltage of the first transistor, and the third node has a voltage value obtained by subtracting the threshold voltage of the first transistor from the first driving voltage.
  10. In paragraph 1, A pixel driving circuit of a display panel characterized in that a first driving voltage is applied and a first scanning signal is input as low so that the first transistor, the second transistor, and the fourth transistor are in a turned-off state, a second driving voltage is applied and a second scanning signal is input as low so that the fifth transistor, the sixth transistor, and the seventh transistor are in a turned-off state, and a second driving voltage is applied and a light emission control signal is input as high so that the third transistor is in a turned-on state and the organic light-emitting diode emits light.
  11. In Paragraph 10, A pixel driving circuit of a display panel characterized in that, when the above-mentioned organic light-emitting diode emits light, the first node has a voltage value obtained by subtracting a second driving voltage from a voltage value obtained by adding a data voltage, a threshold voltage of a first transistor, and an anode voltage of an organic light-emitting diode.

Description

Pixel driving circuit of display panel The present invention relates to a pixel driving circuit of a display panel, and more particularly to a pixel driving circuit of a display panel that can improve afterimages by reducing the leakage current of an LTPS (Low Temperature Poly-Silicon) driving TFT in an LTPO pixel driving circuit. Flat panel displays (FPDs) are employed in various electronic devices such as mobile phones, tablets, laptop computers, as well as televisions and monitors. Examples of FPDs include liquid crystal displays (LCDs), plasma display panels (PDPs), organic light emitting diode (OLEDs), and electrophoretic displays (EPDs). The pixels of FPDs are arranged in a matrix form and controlled by an array of pixel circuits. Some of the driving circuits that provide signals to control the array of pixel circuits are implemented using TFTs on the same substrate as the array of pixel circuits. The substrate on which the pixel circuits and driving circuits are formed is referred to as the TFT backplane. Recently, LTPS circuits have been mainly used in AMOLED displays, and LTPO is gaining attention as power consumption has become critical. Since general TFTs, which are not ideal TFTs, cannot satisfy all characteristics, different types of TFTs are used depending on the role. This LTPO (Low-Temperature Polycrystalline Oxide) technology combines the advantages of LTPS (Low-Temperature Polycrystalline Silicon) and Oxide TFT (Oxide Thin Film Transistor) to improve power efficiency and optimize the driving speed and resolution of displays. Therefore, LTPO pixel circuits reduce the disadvantages of standalone LTPS circuits, which have high power consumption, by adding oxide TFTs to circuits that were previously composed solely of LTPS TFTs. High power efficiency is essential for mobile devices, which have become mainstream, to be used for extended periods without charging due to their limited battery life. Furthermore, reduced power consumption contributes to environmental issues by extending battery life and decreasing energy usage. Since LTPO circuits have lower leakage current and offer superior dynamic refresh rates compared to standalone LTPS circuits, efforts are being made to resolve disadvantages such as increased manufacturing costs and maximize their advantages. Figure 1 is a diagram showing hysteresis characteristics in which black brightness increases due to leakage current of a general driving TFT (T1), and Figure 2 is a diagram showing flicker generation due to the phenomenon of charge trapping of the driving TFT (T1) of Figure 1. As shown in Figures 1 and 2, even in this LTPO pixel circuit, when in a black image state, weak light emission occurs due to the leakage current of T1, and there is a problem in that flicker or afterimage occurs due to hysteresis of T1 or shallow trap charge of T1. Figure 1 is a diagram showing the hysteresis characteristics of increased black luminance due to leakage current of a typical driving TFT (T1). FIG. 2 is a diagram showing the occurrence of flicker due to the phenomenon of charge being trapped in the driving TFT (T1) of FIG. 1. FIG. 3 is a diagram showing the hysteresis characteristics of the LTPS-driven TFT and oxide TFT of the present invention. FIG. 4 is a schematic block diagram of an organic light-emitting display device according to one embodiment of the present invention. FIG. 5 is a drawing illustrating a pixel driving circuit according to an embodiment of the present invention. FIGS. 6 to 9 are timing diagrams for explaining a driving method of a pixel driving circuit according to an embodiment of the present invention. The present invention is susceptible to various modifications and may have various embodiments, and specific embodiments will be described in detail with reference to the drawings. However, this is not intended to limit the invention to specific embodiments, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention. Similar reference numerals have been used for similar components in the description of each drawing. Terms such as first, second, A, B, etc., may be used to describe various components, but said components shall not be limited by said terms. These terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and/or" includes a combination of multiple related description items or any of the multiple related description items. The terms used in this application are used merely to describe specific embodiments and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this application, terms such as "comp