Pixel Circuit Voltage Isolation for OLED Luminance Uniformity
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Solution Overview
Problem
In organic light-emitting display devices, the resistance and capacitance variations of OLEDs between pixels lead to luminance non-uniformity and increased power consumption due to the influence of the light emitting element on pixel data writing, causing changes in pixel luminance.
Innovation Solution
A pixel circuit design with separate data and reference voltage lines, utilizing a driving element and switches to manage voltages and capacitors, which separates the driving element from the light emitting element during sampling and addressing periods, preventing luminance changes caused by OLED resistance and capacitance variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If data voltage and reference voltage are alternately applied to data lines in a cycle of one horizontal period, then power consumption increases, but this conventional approach maintains simple circuit structure
Solution Approach 1:
The patent segments the voltage application by introducing separate data lines and reference lines, dividing the alternating voltage cycle into independent continuous voltage lines. This eliminates the need for frequent switching and reduces power consumption while maintaining circuit functionality.
Solution Approach 2:
The patent introduces dynamic control through multiple switches (first switch, second switch, third switch) that dynamically connect or disconnect the driving element from the light emitting element during different periods (sampling period, addressing period, light emission period). This dynamic separation allows continuous voltage application without frequent switching, reducing power consumption.
2Reliability
If the driving element is connected to the OLED during sampling and addressing periods, then luminance non-uniformity occurs due to OLED resistance and capacitance variations, but disconnecting them会增加 circuit complexity
Solution Approach 1:
The patent employs dynamic switching to connect or disconnect the driving element from the light emitting element based on the operational period. During sampling and addressing periods, the third switch disconnects them to prevent luminance non-uniformity. During light emission period, the third switch connects them for normal operation. This dynamic approach achieves luminance uniformity without excessive circuit complexity.
Solution Approach 2:
The patent implements periodic connection and disconnection of the driving element and light emitting element according to different operational periods (sampling period, addressing period, light emission period). This periodic action ensures the driving element is isolated during critical periods to prevent luminance variations, then connected during light emission for normal display function.
3Reliability
If the driving element remains connected to the OLED, then the gate-source voltage changes under the influence of OLED internal high resistance, causing luminance changes, but isolating them requires additional switches
Solution Approach 1:
The patent uses the third switch as a dynamic isolation element that disconnects the driving element from the light emitting element during sampling and addressing periods. This dynamic isolation prevents the gate-source voltage from being influenced by OLED internal resistance, ensuring luminance stability. The switch is integrated into the existing circuit topology, minimizing additional complexity.
Data Source
AI summary
A pixel circuit and a display device including the same are disclosed. The pixel circuit includes: a driving element including electrodes respectively connected to a first node to receive a first constant voltage, a second node, and a third node; a light emitting element including an anode connected to a fourth node and a cathode to receive a second constant voltage; a first switch to provide a data voltage to the second node; a second switch to provide a third constant voltage to the second node; a third switch to provide a fourth constant voltage to the fourth node; a fourth switch to provide the first constant voltage to the first node; a fifth switch to electrically connect the third node to the fourth node.