MicroLED Data Driver PWM White Balance
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Solution Overview
Problem
Conventional microLED displays face challenges in achieving white balance due to differences in characteristics among microLEDs of different colors and their varying responses to human eyes, leading to complex driver mechanisms and issues with narrow display signal widths, particularly with 8-bit data that can result in insufficient driving of microLEDs.
Innovation Solution
A data driver for microLED displays is designed with clock generators producing PWM clocks for primary colors, counters generating PWM signals, comparators comparing held data signals with PWM signals to generate comparison results, and channel amplifiers outputting adjusted currents to achieve white balance and sufficient driving of microLEDs, including switches for testing uniformity across microLEDs of the same color.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current adjust mechanism is used to achieve white balance, then white balance can be achieved, but driver complexity increases
Solution Approach 1:
The patent changes the control parameter from direct current adjustment to PWM duty cycle control. By using pulse width modulation with different duty cycles for different colors (R, G, B channels), the system achieves white balance through temporal averaging of light output rather than complex current adjustment mechanisms, thereby simplifying the driver architecture while maintaining color accuracy
Solution Approach 2:
The patent employs periodic PWM signals to control microLED brightness. Instead of using complex continuous current adjustment circuits, the system uses periodic pulse trains with variable duty cycles to achieve the desired luminance levels and white balance, replacing complex analog control with simpler digital periodic control
2Productivity
If 8-bit display data is used, then data transmission is efficient, but signal width becomes too narrow to drive microLED sufficiently
Solution Approach 1:
The patent transitions from spatial signal width control to temporal duty cycle control. Instead of relying on the width of continuous analog signals, the system encodes brightness information in the temporal dimension through PWM duty cycles. This allows 8-bit data to be effectively utilized by mapping each bit to a specific duty cycle percentage, ensuring sufficient driving capability while maintaining data transmission efficiency
Solution Approach 2:
The patent replaces the mechanical/analog approach of varying signal width with a digital PWM approach. By substituting continuous analog signal amplitude/width control with discrete digital duty cycle control, the system achieves both efficient 8-bit data transmission and sufficient microLED driving through the relationship: Drive Current ∝ PWM Duty Cycle
Data Source
AI summary
A data driver of a microLED display includes clock generators that generate pulse width modulation (PWM) clocks of corresponding primary colors respectively; counters that receive the PWM clocks of corresponding primary colors respectively and accordingly generate corresponding PWM signals; and comparators associated with corresponding data channels respectively for comparing a held data signal with the corresponding PWM signal, thereby generating a comparison result signal. In one embodiment, the data driver further includes switches configured to electrically short output nodes of channel amplifiers of corresponding primary colors respectively for testing uniformity of microLEDs of one color.