OLED Pixel Driving Circuit With PWM and Progressive Emission
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Solution Overview
Problem
Display apparatuses with light emitting diodes face issues of increased power consumption due to high driving voltages required for achieving desired luminance, especially in high resolution displays, and variations in emission wavelength with current magnitude, affecting grayscale production.
Innovation Solution
The display apparatus employs a pulse width modulation method and progressive emission timing to reduce power consumption by adjusting light emission timings and compensates for transistor threshold voltage deviations, using a sensing circuit to enhance display quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the current for producing desired luminance is increased in simultaneous emission method, then the luminance is improved, but the power consumption increases
Solution Approach 1:
The patent implements progressive emission method where light emitting elements are divided into multiple groups that emit light sequentially in different time periods rather than simultaneously. This periodic action allows the display to achieve desired luminance through time-multiplexed emission, reducing the peak current requirement and thereby lowering power consumption while maintaining display quality
Solution Approach 2:
The patent segments the light emitting elements into multiple groups (e.g., first light emitting elements and second light emitting elements) that operate in different time periods. This segmentation enables independent control of each group, allowing the display to achieve full luminance through sequential emission rather than requiring all elements to emit simultaneously at high current
2Illumination intensity
If the driving voltage is increased to achieve desired luminance, then the luminance is improved, but the power consumption increases
Solution Approach 1:
By implementing periodic emission through progressive emission method, the patent reduces the duty cycle required for each light emitting group, allowing operation at lower driving voltages while maintaining average luminance through time-multiplexed display
3Illumination intensity
If the current magnitude is changed to produce grayscales, then the grayscale production is improved, but the emission wavelength varies
Solution Approach 1:
The patent uses pulse width modulation (PWM) where the duty cycle of periodic pulses is varied to produce different grayscale levels. By keeping the pulse amplitude constant and only varying the pulse width (duty cycle), the emission wavelength remains stable while grayscale production is achieved through temporal averaging of light emission
Solution Approach 2:
The patent changes the temporal parameter (duty cycle) rather than the amplitude parameter to control grayscale. This parameter substitution maintains constant emission wavelength by keeping the current amplitude fixed while varying the duration of current application, thereby achieving grayscale without wavelength shift
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces power consumption while maintaining luminance consistency and improving display quality by stabilizing transistor characteristics.
Implementation Method 1
The display panel may include a light emitting diode as a light emitting element. A emission wavelength of the light emitting diode may change according to a current magnitude
Data Source
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AI summary
A display apparatus is disclosed, which includes a pixel. The pixel includes first through fifth transistors and a light emitting element. The first transistor includes a control electrode electrically connected to a first node, an input electrode that receives a first power voltage and an output electrode electrically connected to the light emitting element. The second transistor includes a control electrode that receives a scan signal, an input electrode that receives a grayscale data voltage and an output electrode electrically connected to a second node. The third transistor includes a control electrode electrically connected to the second node, an input electrode that receives a reference voltage and an output electrode electrically connected to the first node. The fourth transistor includes a control electrode that receives the scan signal, an input electrode that receives a bias data voltage and an output electrode electrically connected to the first node. The fifth transistor includes a control electrode that receives a sensing control signal, an input electrode that receives an initialization voltage and an output electrode electrically connected to the light emitting element.