OLED Pixel Circuit Leakage Current Isolation

Solution Overview

Problem

In OLED panels, the electric leakage of drive transistors leads to a bright dot defect due to instability in the gate electrode voltage, causing increased drive current and display defects.

Innovation Solution

A pixel circuit design that includes a storage capacitor and a switch transistor arranged between the gate electrode of the drive transistor and the reset transistor, reducing the influence of leakage currents on the gate electrode signal, and a second reset transistor with a short-circuited gate and first electrode connected to the second reset signal terminal, to minimize the impact of leakage currents on the anode reset.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional pixel circuit without additional switch transistors is used, then the circuit structure is simple, but leakage current causes bright dot defects due to gate electrode voltage instability

Engineering Contradiction:

Improvedisplay stabilityVSAvoidcircuit structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The reset operation is segmented into two independent stages: first reset stage (resetting gate electrode) and second reset stage (resetting anode). This is achieved by dividing the reset process into two sequential operations controlled by different signal terminals, allowing each stage to be optimized independently and preventing interference between reset operations that causes bright dot defects.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A first switch transistor is introduced as an intermediary component between the gate electrode and the anode during the reset process. This switch transistor acts as a mediator that isolates the gate electrode from direct connection to the anode during the first reset stage, preventing leakage current from the anode from affecting the gate electrode voltage, thereby eliminating bright dot defects.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the gate electrode is directly connected to the anode during reset, then the reset operation is simple, but leakage current from the anode affects gate electrode voltage causing bright dot defects

Engineering Contradiction:

Improvegate electrode voltage stabilityVSAvoidreset operation

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The reset operation is segmented into two independent stages: first reset stage (resetting gate electrode) and second reset stage (resetting anode). This is achieved by dividing the reset process into two sequential operations controlled by different signal terminals, allowing each stage to be optimized independently and preventing interference between reset operations that causes bright dot defects.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A first switch transistor is introduced as an intermediary component between the gate electrode and the anode during the reset process. This switch transistor acts as a mediator that isolates the gate electrode from direct connection to the anode during the first reset stage, preventing leakage current from the anode from affecting the gate electrode voltage, thereby eliminating bright dot defects.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a single reset transistor is used, then the circuit is simple, but the reset process causes bright dot defects due to simultaneous gate and anode resetting interference

Engineering Contradiction:

Improvedisplay qualityVSAvoidreset transistor structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The reset operation is segmented into two independent stages: first reset stage (resetting gate electrode) and second reset stage (resetting anode). This is achieved by dividing the reset process into two sequential operations controlled by different signal terminals, allowing each stage to be optimized independently and preventing interference between reset operations that causes bright dot defects.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The gate electrode is reset first before the anode is reset. By performing the gate electrode reset in advance (first reset stage) and then performing the anode reset subsequently (second reset stage), the patent ensures that the gate electrode voltage is stabilized before the anode reset operation begins, preventing interference that would cause bright dot defects.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11830427B2Pixel circuit, display apparatus and driving method

Publication Date: 2023.11.28 ORDOS YUANSHENG OPTOELECTRONICS

AI summary

Provided are a pixel circuit, a display apparatus and a driving method. In one type of pixel circuit, a first switch transistor is arranged between a gate electrode of a driving transistor and a second electrode of a first reset transistor, such that a leak current of the first reset transistor has a relatively small influence on a gate signal of the driving transistor. In other types of pixel circuit, a second reset transistor for short-circuiting the gate electrode and a first electrode is provided, such that the resetting of an anode of a light-emitting device is only related to a signal of a second reset signal end. Therefore, the voltage difference between two ends of a third reset transistor can be reduced by means of adjusting a signal voltage of a reference voltage signal end.