Pixel Driving Circuit PWM Control for Micro LED Color Stability
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Solution Overview
Problem
Micro LED display technologies face image quality degradation due to unstable color coordinates caused by drifting driving current, especially at low current values, in traditional OLED pixel driving circuits.
Innovation Solution
A pixel driving circuit that includes a digital-driving circuit converting pixel voltage signals to pulse-width-modulation (PWM) signals, with a duty cycle proportional to grayscale levels, ensuring constant driving current and stable color coordinates by controlling the Micro LED's light emission through PWM signals rather than current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a traditional OLED pixel driving circuit is used to control pixel brightness by controlling driving current, then the pixel brightness can be adjusted, but the color coordinates of the Micro LED become unstable especially under low driving current, causing degraded image display quality
Solution Approach 1:
The patent applies pulse-width modulation (PWM) to drive the Micro LED with periodic pulse signals instead of continuous current. The duty cycle of the PWM signal is adjusted to control brightness, while the peak current during each pulse remains constant to maintain stable color coordinates. This periodic action separates brightness control (via duty cycle) from color stability (via constant peak current).
Solution Approach 2:
The patent changes the driving parameter from continuous current level to PWM duty cycle. By keeping the peak current parameter constant and varying only the duty cycle parameter, the system achieves brightness adjustment without affecting color coordinates stability. This parameter separation resolves the contradiction between brightness control and color stability.
2Use of energy by moving object
If driving current is reduced to achieve dimmer pixel brightness, then power consumption decreases, but color coordinates drift increases causing image quality degradation
Solution Approach 1:
The PWM driving method uses periodic pulses with constant peak current but varying duty cycles. Power consumption is reduced by decreasing the duty cycle (less time at peak current), while the color coordinates remain stable because the peak current magnitude during each pulse remains constant. This resolves the contradiction between power savings and color stability.
Solution Approach 2:
The system dynamically adjusts the duty cycle parameter while keeping the peak current parameter fixed. This dynamic control approach allows power consumption to vary with duty cycle while maintaining color stability through constant peak current, resolving the contradiction between energy efficiency and reliability.
3Reliability
If PWM signaling is used to control Micro LED light emission, then color coordinates stability is improved, but the device complexity increases due to additional digital-driving circuit components
Solution Approach 1:
The patent integrates the digital-driving circuit functions (ADC, memory, PWM generation) into a unified circuit block that interfaces with the existing pixel driving circuitry. By merging these functions into a compact integrated structure, the complexity increase is minimized while achieving color coordinates stability through PWM control.
Solution Approach 2:
The digital-driving circuit acts as an intermediary between the input voltage signal and the Micro LED. It converts the input signal to PWM format and provides it to the LED through the driving transistor. This intermediary circuit enables color stability while managing the complexity through functional integration and modular design.
Data Source
AI summary
A pixel driving circuit for a light-emission-device-based display panel is provided, including a driving transistor coupled to a light-emission device per subpixel; a digital-driving circuit having a first input terminal configured to receive a pixel voltage signal corresponding to a grayscale level of a subpixel image to be displayed and a first output terminal coupled to a gate terminal of the driving transistor. The digital-driving circuit is configured to convert the pixel voltage signal to a digital signal and transform the digital signal to a pulse-width-modulation (PWM) signal outputted via the first output terminal to the gate terminal of the driving transistor. The PWM signal comprises a pulse width proportional to the grayscale level as a duty cycle in a period of driving the light-emitting device to display subpixel image.