Display Driving Circuit Segmentation for Brightness Uniformity
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Solution Overview
Problem
Existing display technologies face issues with uneven brightness (mura) due to the design of a single driving signal causing transistors in the light-emitting circuit to operate in the saturation region, leading to output waveform instability and recurrence of brightness issues over time.
Innovation Solution
The proposed solution involves a display design that includes a first light emitting device with a first switch and a second switch. The first switch adjusts a first node according to a first clock signal, while the second switch generates a first light emitting signal based on a first voltage signal. The control end of the second switch is coupled to the first node, and the clock signal switches between two voltage levels, with the voltage signal having a third voltage level that is more than one of the first voltage levels and less than the other.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single driving signal is used to control the light-emitting circuit, then the circuit structure is simple, but the transistor operates in the saturation region causing output waveform instability and uneven brightness
Solution Approach 1:
The patent divides the driving signal into multiple stages: a first driving signal to turn on the transistor and a second driving signal to turn it off. This segmentation allows the transistor to operate in the linear region during the second signal, preventing saturation and improving output waveform stability while maintaining relatively simple circuit structure.
Solution Approach 2:
The patent dynamically switches between different driving signals based on the operational phase. The control unit selectively applies the first driving signal during the on-phase and the second driving signal during the off-phase, enabling the transistor to operate in optimal regions at different times and improving overall waveform stability.
2Device complexity
If a single driving signal is used, then the control circuit is simple, but the brightness uniformity deteriorates over time due to transistor threshold voltage effects
Solution Approach 1:
The driving control is segmented into distinct phases with different signal characteristics. The first driving signal provides strong drive during the on-phase, while the second driving signal provides controlled turn-off in the linear region, compensating for threshold voltage effects and maintaining brightness uniformity over time.
Solution Approach 2:
The patent changes the driving signal parameters (amplitude, duration, timing) to optimize transistor operation. By adjusting the second driving signal to operate the transistor in the linear region, the system compensates for threshold voltage variations and maintains stable brightness uniformity throughout operation.
3Power
If the transistor operates in the saturation region, then the light emission is strong, but the output waveform is easily affected by critical voltage and brightness unevenness reappears
Solution Approach 1:
The patent dynamically transitions the transistor between saturation and linear operating regions. During the first driving signal phase, the transistor operates in saturation for strong light emission. During the second driving signal phase, it transitions to the linear region for stable turn-off, preventing waveform distortion and brightness unevenness.
Solution Approach 2:
The patent employs periodic alternating application of first and second driving signals. This periodic action ensures the transistor cycles through appropriate operating regions, maintaining strong emission during the on-phase while ensuring stable, distortion-free turn-off during the off-phase.
Data Source
AI summary
A display includes a first light emitting device. The first light emitting device includes a first switch and a second switch. The first switch is configured to adjust a first node according to a first clock signal. The second switch is configured to generate a first light emitting signal according to a first voltage signal. A control end of the second switch is coupled to the first node. The first clock signal switches between a first voltage level and a second voltage level. The first voltage signal has a third voltage level. The third voltage level is more than one of the first voltage level and the second voltage level and is less than the other one of the first voltage level and the second voltage level.