PMOSFET Sub Pixel Circuit Forward Voltage Compensation
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Solution Overview
Problem
Inorganic light emitting devices in display apparatuses face variations in electrical properties such as threshold voltage and mobility, leading to image quality deterioration, and existing driving circuits fail to effectively compensate for these variations, especially in p-type metal-oxide-semiconductor field-effect transistor (PMOSFET) sub pixel circuits with cathode common structures.
Innovation Solution
A display apparatus with a pixel array and sub pixel circuits that include a sensing part to detect current variations and a correcting part to adjust image data voltage, using a p-type metal-oxide-semiconductor field-effect transistor (PMOSFET) with an anode common structure to maintain stable driving voltage and compensate for forward voltage variations, incorporating constant current generator and pulse width modulation circuits to optimize driving current and time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a cathode common structure is used in PMOSFET sub pixel circuits, then stable driving voltage is achieved, but forward voltage variation of inorganic light emitting devices cannot be compensated
Solution Approach 1:
The patent introduces a sensing circuit that measures the forward voltage of each inorganic light emitting device and feeds back this information to a compensation circuit. The compensation circuit then adjusts the driving voltage individually for each device based on the measured forward voltage, enabling real-time compensation of forward voltage variations while maintaining stable driving conditions.
Solution Approach 2:
The patent dynamically changes the driving voltage parameter based on the measured forward voltage of each inorganic light emitting device. By adjusting the driving voltage to compensate for forward voltage variations, the system maintains consistent image quality across all pixels while preserving the stability benefits of the cathode common structure.
2Device complexity
If threshold voltage and mobility variations of driving transistors are not compensated, then device complexity is reduced, but image quality deteriorates
Solution Approach 1:
The patent employs sensing circuits that measure the electrical properties of driving transistors and feed back this data to compensation circuits. These compensation circuits adjust the driving voltage to account for threshold voltage and mobility variations, thereby maintaining image quality consistency without requiring complex circuit redesigns.
Solution Approach 2:
The patent implements a universal compensation mechanism that can handle multiple sources of variation (threshold voltage, mobility, forward voltage) through a single integrated sensing and compensation system. This multi-functional approach maintains image quality consistency while avoiding the need for separate compensation circuits for each type of variation.
3Manufacturing precision
If forward voltage variation of inorganic light emitting devices is not compensated, then manufacturing precision requirements are reduced, but brightness uniformity deteriorates
Solution Approach 1:
The patent introduces sensing circuits that measure the forward voltage of each inorganic light emitting device and feed back this information to a compensation circuit. The compensation circuit adjusts the driving voltage for each device based on the measured forward voltage, thereby compensating for manufacturing variations and maintaining brightness uniformity across the display.
Solution Approach 2:
The patent dynamically changes the driving voltage parameter for each inorganic light emitting device based on its measured forward voltage. This parameter adjustment compensates for manufacturing precision variations, ensuring that devices with different forward voltages produce uniform brightness output.
Data Source
AI summary
In a display apparatus, a display panel includes a pixel array of pixels, each pixel disposed on one of a plurality of row lines and including a plurality of inorganic LEDs, and a sub pixel circuit corresponding to each of the plurality of LEDs. Each sub pixel circuit includes a PMOSFET driving transistor, and drives a corresponding LED based on an applied image data voltage. A sensing part senses a current through the driving transistor of at least one sub pixel circuit based on a specified voltage applied to the sub pixel circuit, and outputs corresponding sensing data. A correcting part corrects an image data voltage applied to the sub pixel circuit based on the sensing data. In each LED, an anode electrode is coupled to a common node to which a driving voltage is applied, and a cathode electrode is coupled to a source terminal of the driving transistor.