Digital Pixel Driver Circuit for Micro LED Current Control
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Solution Overview
Problem
Current analog pixel driver circuits for micro LEDs face challenges in responding quickly to low pixel currents required for high refresh rates and achieving nanoamp-level currents, which is difficult due to transistor size limitations and manufacturing constraints in display technology.
Innovation Solution
Implementing digital driving techniques using nMOS transistors and a transconductor architecture that includes transistors configured as differential transconductance amplifiers and linearizing circuits to control current through micro LEDs, allowing for pulse width or pulse density modulation to manage brightness and luminance uniformly across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog pixel driver circuits are used for micro LEDs, then current control capability is improved, but response speed deteriorates for high refresh rates
Solution Approach 1:
The patent replaces analog pixel driver circuits with a digital pixel driver circuit that uses nMOS transistors as switches controlled by digital signals. This substitution of digital control for analog control enables faster response speeds suitable for high refresh rates while maintaining precise current control through the transistor switching mechanism and transconductor architecture.
2Measurement precision
If transistor size is reduced to achieve nanoamp-level currents, then current precision is improved, but manufacturing difficulty increases
Solution Approach 1:
The patent changes the operating parameters of the nMOS transistors by controlling their switching states with digital signals and using the transconductor circuit to convert voltage signals to precise current outputs. This allows achievement of nanoamp-level current precision without requiring extremely small transistor dimensions, thereby avoiding manufacturing difficulties associated with sub-10nm fabrication.
3Use of energy by moving object
If digital driving techniques are implemented, then power consumption is reduced, but circuit complexity increases
Solution Approach 1:
The patent segments the pixel driver circuit into distinct functional blocks: nMOS switching transistors for digital control, a transconductor for voltage-to-current conversion, and linearizing circuits for current precision. This segmentation allows each component to be optimized independently and simplifies the overall digital control architecture, reducing the perceived complexity while enabling low-power operation through efficient digital switching.
4Speed
If nMOS transistors are used as switches, then switching speed is improved, but current control precision deteriorates
Solution Approach 1:
The patent introduces a transconductor circuit as an intermediary between the nMOS switching transistors and the micro LED current control. The transconductor converts the fast-switching voltage signals from the nMOS transistors into precisely controlled current signals, thereby maintaining the high switching speed advantage of nMOS devices while achieving the required current control precision for display applications.
Data Source
AI summary
In one example, a system for driving current, including a circuit to receive an input voltage, and to produce a current to be provided to one or more light-emitting diodes. The current is to be linearly dependent on the input voltage.