Micro LED Pixel Circuit PWM Control for Wider Dynamic Range
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Solution Overview
Problem
The dynamic range of light emission in micro LED displays using clamp type inverters is limited, leading to constraints in circuit design and increased manufacturing costs, and the existing methods to prevent pulse signal overlap result in increased circuit scale.
Innovation Solution
A display apparatus with a pixel circuit that employs a MOS transistor-based PWM controller to generate PWM signals based on image and slope signals, allowing for expanded dynamic range without signal overlap, using a configuration that includes a metal oxide semiconductor transistor, capacitor, amplifier, and switches to control the light emission time of micro LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a clamp type inverter is used for PWM gradation control, then pseudo contour phenomenon is prevented, but the dynamic range of light emission is limited
Solution Approach 1:
The pixel circuit is divided into multiple sub-pixels, each with its own light emitting element and control circuitry. This segmentation allows independent control of each sub-pixel, enabling extended dynamic range through combined output while maintaining the clamp type inverter's advantage of preventing pseudo contour phenomenon in each individual sub-pixel
Solution Approach 2:
The patent extends the dynamic range by utilizing multiple sub-pixels that can be independently controlled in different brightness states. By combining the output of multiple sub-pixels, the system achieves an extended dynamic range beyond what a single pixel could provide, while each sub-pixel still uses clamp type inverter control to prevent pseudo contour
2Reliability
If new pulse signals are input/output to prevent activation period overlaps, then pulse signal interference is prevented, but the circuit scale increases
Solution Approach 1:
The patent combines multiple control functions into integrated control circuits within each sub-pixel. The control circuits for multiple sub-pixels share common signal lines and control logic, merging functions to prevent pulse signal overlaps without proportionally increasing the overall circuit scale. This integration maintains reliable pulse control while minimizing circuit complexity
Solution Approach 2:
The control circuits are designed with multi-functionality, where single control signals serve multiple purposes across different sub-pixels. The same control signal lines are used to coordinate activation periods of multiple sub-pixels, preventing overlaps without requiring dedicated separate control paths for each sub-pixel, thus avoiding circuit scale expansion
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
The solution expands the dynamic range of light emission, reduces circuit complexity, and prevents activation period overlaps, thereby enhancing the precision and efficiency of PWM control while minimizing circuit scale and power consumption.
Implementation Method 1
a light emitting element D; and a micro IC configured to drive the light emitting element
Data Source
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AI summary
A display apparatus includes a light emitting element; and a pixel circuit configured to drive the light emitting element. The pixel circuit may include a first capacitor configured to output a first voltage corresponding to an image signal; a first transistor having a control terminal connected to the first capacitor and to which the first voltage is applied, a first terminal to which a second voltage corresponding to a slope signal that changes over time is applied, and a second terminal configured to output an output signal based on a comparison between the first voltage and the second voltage; and a driving circuit configured to drive the light emitting element based on the output signal of the second terminal.