AMOLED Pixel Circuit Compensation Module for G Node Potential Drop
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Solution Overview
Problem
Conventional active matrix organic light emitting diode (AMOLED) pixel circuits experience uneven light emission due to potential drops at the G node caused by capacitor coupling, leading to display uniformity issues over time.
Innovation Solution
A pixel circuit design incorporating a compensation module connected to a scan signal and power supply voltage to counteract potential drops at the G node, maintaining a constant reference voltage and ensuring uniform light emission by using a third thin film transistor and second capacitor in conjunction with existing transistors and capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional 3T1C pixel circuit is used, then the circuit structure is simple, but the display uniformity deteriorates due to potential drop at G node caused by capacitor coupling
Solution Approach 1:
The pixel circuit is segmented into multiple functional modules: driving transistor T1, switching transistors T2-T5, compensation transistor T6, and multiple capacitors (C1-C4) with distinct functions. This segmentation allows independent optimization of each module to address the coupling effect while maintaining overall circuit functionality.
Solution Approach 2:
A compensation transistor T6 is introduced as an intermediary element to counteract the harmful coupling effect between capacitor C1 and node G. The compensation transistor actively adjusts the potential at node G to compensate for voltage drops, thereby maintaining display uniformity without fundamentally changing the basic 3T1C structure.
2Ease of operation
If the gate of T2 is closed to write data signal, then the data writing function is achieved, but the potential at G node drops due to coupling of capacitor C1 causing current fluctuation
Solution Approach 1:
Capacitor C2 is pre-charged to a reference voltage before the data writing operation. When the gate of T2 is closed, this pre-charged capacitor provides a stabilizing effect that prevents excessive potential drop at node G, thereby maintaining current stability during the data writing process.
Solution Approach 2:
The compensation transistor T6 is configured to provide feedback control on node G potential. By monitoring the voltage at node G and actively adjusting the compensation current, the circuit maintains stable operating conditions even when capacitor C1 couples and causes potential fluctuations during data writing.
3Quantity of substance
If capacitor C1 is used for voltage storage, then the basic pixel function is maintained, but coupling effects cause uneven light emission across the panel
Solution Approach 1:
Different capacitors are assigned different local functions: capacitor C1 stores the main drive voltage, capacitor C2 provides reference voltage and coupling compensation, and capacitor C3 stores compensation voltage. This local differentiation of capacitor functions allows the system to maintain voltage storage capacity while eliminating the harmful coupling effects that cause non-uniform light emission.
Solution Approach 2:
The circuit introduces additional voltage parameters through multiple capacitors (Vref from C2, Vcomp from C3) to control and stabilize the operating point. By changing and controlling multiple voltage parameters simultaneously, the system maintains proper voltage storage while compensating for coupling-induced variations in light emission intensity across different panel regions.
Data Source
AI summary
Provided are a pixel circuit, a display panel, and a compensation method of a reference voltage of a pixel circuit, including a plurality of pixel internal driving circuits arranged in an array. The internal driving circuit of each pixel includes: a first thin film transistor (T1), a second thin film transistor (T2), a fourth thin film transistor (T4), a first capacitor (C1), an organic light emitting diode (D1), and a compensation module. By setting the compensation module, the compensation module is connected to a scan signal (EM). An end of the compensation module is connected to a first node (G), and another end of the compensation module is connected to a power supply voltage (VDD). The compensation module is configured to compensate a potential drop of the first node (G) due to coupling of the first capacitor (C1).