Pixel Circuit Driving Modules for Display Gray Value Control
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Solution Overview
Problem
Conventional display driving techniques, such as pulse amplitude modulation (PAM) and pulse width modulation (PWM), face challenges in achieving high light emitting efficiency and display evenness, particularly at low gray values, and require excessive frequency divisions at high gray values, straining chip resources.
Innovation Solution
A pixel circuit incorporating both pulse amplitude and pulse width driving modules, where the pulse amplitude driving module is used for middle to high gray values to reduce frequency divisions and the pulse width driving module is used for middle to low gray values to enhance light emitting efficiency and luminance evenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If pulse amplitude modulation (PAM) driving technique is used, then the control method is simple, but the light emitting efficiency is low and power consumption is high at low gray values
Solution Approach 1:
The patent segments the driving range into different gray value ranges (low, middle, high) and applies different driving techniques to each segment. For low gray values, PWM is used to maintain high light emitting efficiency, while for middle and high gray values, PAM is used for simple control. This segmentation resolves the contradiction by allowing each technique to operate in its optimal range.
Solution Approach 2:
The patent dynamically switches between PAM and PWM driving techniques based on the current gray value being displayed. The switching is controlled by comparing the data signal voltage with reference voltages to determine which driving module should be active. This dynamic adaptation allows the system to optimize light emitting efficiency at low gray values while maintaining control simplicity at higher gray values.
2Loss of energy
If pulse width modulation (PWM) driving technique is used, then the light emitting efficiency is higher and display evenness is better, but the number of frequency divisions increases significantly at high gray values
Solution Approach 1:
The patent divides the gray value range into segments where PWM is applied only to low gray values (0-127 out of 256 total levels). For middle and high gray values, PAM takes over, eliminating the need for extensive frequency divisions that would be required if PWM were used across the entire range. This segmentation dramatically reduces device complexity while preserving PWM's efficiency benefits where needed.
Solution Approach 2:
The patent changes the driving parameter from pulse width (PWM) to pulse amplitude (PAM) based on the gray value range. By switching the control parameter itself rather than just adjusting values within one technique, the system avoids the exponential increase in frequency divisions required for high-resolution PWM at high gray values, thereby reducing device complexity.
3Measurement precision
If PWM driving technique is used for high gray values, then more gray levels are achieved, but the frequency of control signal must be higher which strains chip resources
Solution Approach 1:
The patent segments the gray level range so that low gray levels (0-127) are controlled by PWM with its fine resolution capability, while middle and high gray levels (128-255) are controlled by PAM. This segmentation allows high resolution to be achieved where it matters most (low gray values where precision is most noticeable) while avoiding the high frequency requirements that would be needed to achieve similar resolution across the entire range using PWM alone.
Solution Approach 2:
The patent applies PWM's high-resolution capability partially, only to the lower half of the gray value range where precision is most critical for display quality. For the upper half, PAM provides sufficient resolution without requiring excessive control signal frequency. This partial application of PWM resolves the contradiction by using high-frequency capability only when necessary.
Data Source
AI summary
A pixel circuit and a display panel are disclosed. The pixel circuit comprises a first transistor, a pulse amplitude driving module, and a pulse width driving module. The pixel circuit and the display panel utilize a pulse amplitude driving module to drive the first transistor when a middle to high gray value of a frame is being displayed such that the number of frequency divisions in a high gray value could be reduced. Furthermore, the pixel circuit and the display panel utilize a pulse width driving module to drive the first transistor when a middle to low gray value of the frame is being displayed to improve the light emitting efficiency and luminance evenness in a low gray value.