Pixel Driving Circuit Using Pulse-Width Grayscale Control
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Solution Overview
Problem
Light emitting type display devices experience grayscale distortion due to changes in transistor characteristics over time, leading to shifts in preset color coordinates.
Innovation Solution
A pixel design that controls the emission duration of light emitting elements by adjusting pulse width, using a pulse width control circuit and pixel driving circuit to manage the duration of light emission based on data voltage, with capacitors and switching elements to stabilize the driving current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the magnitude of driving current is varied to display images of various grayscales, then the grayscale display capability is improved, but the color coordinates become distorted due to transistor characteristic changes
Solution Approach 1:
The patent changes the control parameter from driving current magnitude to emission duration (pulse width). By varying the length of time the light emitting element is activated rather than varying current magnitude, the system achieves grayscale control without the color distortion that occurs with current variation. This is implemented through a pulse width control circuit that generates emission control signals with different pulse widths corresponding to different grayscale levels.
2Illumination intensity
If the driving current magnitude is changed to achieve different grayscales, then the image brightness control is improved, but the transistor characteristic variations cause color distortion
Solution Approach 1:
The patent employs periodic emission control where the light emitting element is activated in periodic pulses of varying widths. Each frame or field is divided into discrete emission periods, and the pulse width within each period controls the perceived brightness. This periodic pulsed operation allows precise brightness control through temporal modulation rather than current magnitude adjustment, avoiding color consistency issues.
Data Source
AI summary
A pixel according to an embodiment of the disclosure includes a light emitting element, a pulse width control circuit that is electrically connected to a data line to which a data voltage is applied, generates an emission control signal having a pulse width depending on the data voltage, and outputs the emission control signal, and a pixel driving circuit that receives the emission control signal and supplies a driving current to the light emitting element for a period according to the pulse width of the emission control signal. According to an embodiment of the disclosure, a pixel displaying images of various grayscales by controlling a period in which the light emitting element emits light, a method for driving the same, and a display device including the same may be provided.