Hybrid Microdriver Circuit for μLED Display Driving
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Solution Overview
Problem
Conventional active matrix display technologies face challenges in efficiently driving micro LEDs (μLEDs) due to low electron mobility and larger threshold voltage shifts in amorphous silicon TFTs, and high power consumption with existing TFTs, which limits the ability to provide high currents required for μLEDs.
Innovation Solution
A hybrid microdriver circuit architecture combining crystalline silicon MOSFETs with TFT processing, using a hybrid of analog and digital driving techniques, including a microdriver IC with emission logic and comparator logic to control LED emission pulses based on analog input voltages, allowing for constant current driving and pulse width modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If amorphous silicon TFTs are used for driving μLEDs, then large-area fabrication in low temperature process is enabled, but electron mobility is low and threshold voltage shift is large
Solution Approach 1:
The display driver is segmented into two distinct parts: a TFT backplane for addressing and data storage (maintaining ease of manufacture) and separate microdriver integrated circuits for constant current driving (providing high mobility and reliability). This segmentation allows each component to be optimized independently for its specific function.
Solution Approach 2:
The microdriver integrated circuit acts as an intermediary between the TFT backplane and the μLEDs. It receives analog data voltages from the TFT backplane and converts them into precise constant current drive signals, bridging the gap between the low-mobility TFT and the high-current-requiring μLED.
2Device complexity
If conventional TFTs are used to drive μLEDs, then integration is simplified, but power consumption is high due to inability to provide required currents
Solution Approach 1:
The driving function is segmented between the TFT backplane (addressing and data storage) and dedicated microdriver ICs (constant current driving). This allows the microdriver to be optimized for efficient current delivery to μLEDs, significantly reducing power consumption while maintaining integration through the hybrid architecture.
Solution Approach 2:
The system transitions from direct voltage driving by TFTs to pulse-width modulation (PWM) with constant current driving by microdrivers. By changing the driving parameter from voltage to controlled current pulses, power consumption is optimized while maintaining the necessary current delivery capability for μLEDs.
3Power
If higher current delivery to LEDs is enabled, then brightness and efficiency improve, but transistor geometry must be larger increasing circuit area
Solution Approach 1:
The microdriver integrated circuit serves as an intermediary that can deliver high currents to μLEDs without requiring large transistor geometries in the TFT backplane. The microdriver contains the necessary current-boosting capability, allowing the TFTs to remain small while still achieving high current delivery through the hybrid architecture.
Solution Approach 2:
The current driving function is segmented into the microdriver IC, which is optimized for high current delivery with appropriate transistor sizes. This separates the high-current requirement from the TFT backplane, allowing the backplane transistors to remain small while the microdriver handles the power delivery demands.
Data Source
AI summary
Methods, systems, and apparatuses for controlling an emission of the light emitting devices are described herein. The light emitting devices may be light emitting diode (LED) devices including μLED devices or organic LED (OLED) devices. Emission control of the LED may be performed using a micro-scale driving circuit (e.g., μDriver) containing drive transistors for constant current driving of the light emitting devices. One embodiment provides for a display driver hardware circuit including emission logic, the emission logic including comparator logic to compare a data voltage from a storage capacitor to a voltage ramp provided via the TFT backplane, the comparator logic to cause the emission logic to generate an emission pulse to an LED device, and wherein the integrated circuit is to switch and drive a plurality of LED devices. In one embodiment each of the plurality of LED devices is a subpixel for a display device.