AMOLED Pixel Circuit Synchronizing Initialization and Threshold Compensation
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Solution Overview
Problem
Active matrix organic light emitting diode (AMOLED) panels face issues with display unevenness due to changing current intensity through electroluminescent elements, caused by threshold voltage variations in driving transistors, requiring complex pixel circuits to maintain stability and uniform illumination, which limits response speed and refresh rate.
Innovation Solution
A simplified pixel circuit design incorporating a scanning signal response module, a light emitting signal response module, and two capacitors to synchronize initialization, maintain gate voltage, and compensate for threshold voltage drift, using transistors and capacitors to store and release voltages effectively, thereby reducing the duty cycle complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a complicated pixel circuit with multiple transistors and capacitors is used to compensate threshold voltage variation, then display uniformity is improved, but device complexity increases and response speed decreases
Solution Approach 1:
The patent combines the initialization function and threshold voltage compensation function into a single integrated circuit block. The fourth transistor serves dual purposes: initializing the capacitor during the initialization period and compensating for threshold voltage variations during the light emitting period. This merging of functions reduces the number of required components while maintaining both display uniformity and response speed
2Stability of the object's composition
If a complicated pixel circuit with multiple transistors and capacitors is used to maintain current stability, then display uniformity is improved, but refresh rate decreases
Solution Approach 1:
The patent performs threshold voltage compensation in advance during the initialization period, before the light emitting period begins. The fourth transistor is turned on during initialization to pre-charges the capacitor with a voltage that compensates for anticipated threshold voltage variations. This preliminary action ensures current stability during light emission without extending the active display period, thereby maintaining high refresh rates
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enhances the response speed and refresh rate of the organic light emitting device by completing initialization synchronously and compensating for threshold voltage drift, ensuring consistent driving current during the light emitting period.
Implementation Method 1
a capacitor, and an electroluminescence element; the pixel circuit comprises: a scanning signal response module, a light emitting signal response module, a first capacitor and a second capacitor
Implementation Method 2
organic light emitting devices include organic light emitting diodes (OLEDs) and active matrix organic light emitting diodes (active matrix OLEDs, AMOLEDs)
Data Source
AI summary
A pixel circuit of an organic light emitting device and an organic light emitting display panel are disclosed. Two steps of a pixel circuit duty cycle can be realized by completing initialization in synchronization during the program period at same time, maintaining a gate voltage of a driving transistor, and compensating for a threshold voltage drift in the driving transistor. Thereby improving response speed of the organic light emitting device, and increasing refresh rate of the display panel.