Pixel Circuit With Integrated Threshold Compensation and PWM Dimming
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Solution Overview
Problem
The internal compensation circuit of Micro-LED displays with both threshold compensation and pulse width modulation functions has a complex structure, hindering high PPI design and brightness uniformity during low-gray-scale display.
Innovation Solution
A pixel circuit with a simplified structure incorporating a driving circuit and a light emitting gating control circuit, which forms current paths under control signals to manage light emission, including multiple control circuits and energy storage circuits to achieve dimming and low grayscale compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pixel circuit includes both compensation module and dimming module to achieve threshold compensation and pulse width modulation functions, then the display performance is improved, but the circuit structure becomes complicated
Solution Approach 1:
The patent combines the compensation module and dimming module into a single integrated pixel circuit structure. The driving transistor serves dual functions: it provides threshold compensation through the compensation capacitor while simultaneously enabling pulse width modulation for dimming control. This merging eliminates the need for separate dedicated circuits for each function, thereby improving display performance without proportionally increasing circuit complexity.
Solution Approach 2:
The driving transistor is designed to perform multiple functions within the pixel circuit. It acts as both the compensation transistor for threshold voltage correction and the dimming control transistor for brightness adjustment via pulse width modulation. This multi-functionality reduces the total number of transistors required while maintaining both compensation and dimming capabilities.
2Productivity
If the internal compensation circuit structure is simplified to achieve high PPI design, then the pixel density is improved, but the brightness uniformity during low-gray-scale display deteriorates
Solution Approach 1:
The patent implements a feedback mechanism where the compensation capacitor stores the threshold voltage information of the driving transistor, and this compensated voltage is fed back to control the light emitting element. This feedback loop ensures that even with a simplified circuit structure suitable for high PPI, the threshold variations are compensated, maintaining brightness uniformity during low-gray-scale display through pulse width modulation.
Solution Approach 2:
The compensation capacitor performs preliminary compensation of the driving transistor's threshold voltage before the actual display operation. By pre-compensating the threshold voltage in the pixel circuit, the system ensures that subsequent low-gray-scale display operations maintain brightness uniformity without requiring complex real-time adjustment circuits.
Data Source
AI summary
A pixel circuit, a pixel driving method and a display device are provided. The pixel circuit includes a driving circuit, a light emitting element and a light emitting gating control circuit; the driving circuit is electrically connected to a first electrode of the light emitting element, and is configured to drive the light emitting element; the light emitting gating control circuit is configured to form a current path between the second electrode of the light emitting element and the first voltage terminal under the control of the first control signal provided by the first control terminal according to the first light emitting control voltage provided by the first light emitting control voltage terminal and the light emitting data voltage provided by the light emitting data voltage terminal, to control the driving circuit to control the light emitting element to emit light.