Pixel Circuit IR Drop Compensation for OLED Uniformity
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Solution Overview
Problem
In organic light-emitting display devices, power supply voltage drops (IR drops) lead to uneven display luminance due to different currents flowing through light-emitting diodes, causing variations in display brightness.
Innovation Solution
A pixel circuit comprising six thin film transistors, a storage capacitor, and a light-emitting diode, where the current flowing through the diode is independent of the power supply voltage, compensated by reference and data voltages, ensuring consistent luminance across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If power supply voltage is transmitted between multiple pixel circuits, then power supply can be shared across the display device, but power supply voltage drop (IR drop) occurs resulting in different actual power supply voltages at each pixel circuit
Solution Approach 1:
The patent introduces a compensation transistor and capacitor to dynamically adjust and compensate for power supply voltage drops. By changing the operating parameters (voltage levels) through active compensation circuitry, the system maintains consistent current flow to light-emitting diodes despite IR drops, thereby preserving display luminance uniformity while enabling power supply sharing across multiple pixel circuits
2Manufacturing precision
If power supply voltage drops occur, then current flow through light-emitting diodes varies, but increasing power supply voltage to compensate would increase power consumption and heat generation
Solution Approach 1:
The patent employs a compensation transistor and capacitor that consume minimal energy to correct voltage drops. Rather than increasing the main power supply voltage across the entire display (which would increase overall power consumption), the compensation circuit locally adjusts voltage levels using small amounts of energy, effectively 'disposing' of the voltage drop problem at each pixel circuit level without substantial energy cost
3Manufacturing precision
If different currents flow through light-emitting diodes due to power supply voltage drops, then display luminance becomes uneven, but adding more transistors per pixel circuit increases circuit complexity
Solution Approach 1:
The compensation transistor and capacitor perform multiple functions: they compensate for power supply voltage drops, maintain consistent current flow to light-emitting diodes, and ensure uniform display luminance. By making these components multi-functional, the patent achieves display luminance uniformity without substantially increasing circuit complexity, as the same components address multiple aspects of the voltage drop problem
Data Source
AI summary
The disclosure discloses a pixel circuit and a driving method thereof, a display device. The pixel circuit includes a first through six thin film transistors, a light-emitting diode and a storage capacitor. A gate of the first thin film transistor is separately connected to a source of the second thin film transistor, a source of the third thin film transistor and one end of the storage capacitor. The other end of the storage capacitor is separately connected to a drain of the fourth thin film transistor and a source of the fifth thin film transistor. A source of the first thin film transistor is connected to a first power source. A drain of the first thin film transistor is separately connected to a drain of the second thin film transistor and a source of the sixth thin film transistor.