Distributed PWM System for LED Flicker Reduction
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Solution Overview
Problem
Existing active-matrix display systems face limitations in providing efficient, constant current drive signals to light emitters, leading to reduced display resolution and increased power consumption due to flicker issues in passive-matrix displays and complex control schemes in OLED active-matrix displays.
Innovation Solution
A distributed pulse-width modulation system with multi-bit digital values stored in small, high-performance micro transfer printed integrated circuits, enabling constant-current drive for LEDs with reduced flicker and high-frequency active-matrix control, using an array of pulse-width modulation elements with digital memory and drive circuits to independently control each pixel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pre-charge current pulses and discharge pulses are used to address capacitance and inductance issues, then temporal resolution for light emitters is improved, but power consumption increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-charging the storage capacitor during the data writing phase before the actual light emission. This allows the capacitor to be ready to provide the required current pulse without needing additional pre-charge pulses at the moment of emission, thereby reducing power consumption while maintaining temporal resolution.
Solution Approach 2:
The patent ensures continuous useful action by maintaining the storage capacitor charged throughout the frame period, allowing immediate response to PWM signals without interruption. This eliminates the need for repeated pre-charge and discharge cycles, reducing power consumption while sustaining high temporal resolution.
2Measurement precision
If active-matrix control with separate TFT circuit for each pixel is used, then display resolution is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent merges the control transistor and storage capacitor into a single integrated pixel circuit unit that is directly formed on the display substrate. This consolidation reduces the number of separate components and interconnections needed, simplifying the overall device structure while maintaining active-matrix control capabilities for high display resolution.
Solution Approach 2:
The integrated pixel circuit serves multiple functions: it acts as both the control element for PWM signaling and the storage element for maintaining the drive voltage. This multi-functionality reduces the need for separate dedicated components, thereby reducing device complexity while preserving high-resolution display capabilities.
3Ease of operation
If inorganic LEDs are driven with variable current or voltage, then ease of operation is improved, but efficiency and power consumption worsen due to variable efficiency at different operating levels
Solution Approach 1:
The patent employs periodic PWM (pulse-width modulation) signaling to drive the inorganic LEDs. By switching the constant current source on and off at high frequency with duty cycles corresponding to the desired brightness levels, the system maintains high efficiency at all brightness levels while achieving precise grayscale control, thus improving both ease of operation and power efficiency.
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 system achieves high-resolution displays with efficient constant-current drive for LEDs, reducing flicker and power consumption while enabling arbitrary bit depth and gray-scale resolution through spatially distributed pulse-width modulation control.
Implementation Method 1
each element including a digital memory for storing a multi-bit digital value
Implementation Method 2
A distributed pulse-width modulation system with multi-bit digital values stored in small, high-performance micro transfer printed integrated circuits, enabling constant-current drive for LEDs
Data Source
AI summary
A distributed pulse-width modulation system includes an array of pulse-width modulation elements, each element including a digital memory for storing a plurality of multi-bit digital values, a drive circuit for each stored multi-bit digital value, and an output device for each stored multi-bit digital value. The multi-bit digital values all have the same number of bits. For each stored multi-bit digital value, the corresponding drive circuit drives the corresponding output device in response to the multi-bit digital value stored in the digital memory. A system controller includes a memory for storing the multi-bit digital values for each pulse-width modulation element and a communication circuit communicates each multi-bit digital value to each corresponding pulse-width modulation element.