Micro-LED Pulse Driving With Baseline Pre-Charge for Fast Turn-On
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Solution Overview
Problem
Conventional driving techniques for micro-LEDs with dimensions smaller than 20 μm result in prolonged rise times from an off-state to an on-state, exceeding 100 ns, which is inadequate for fast modulation required in future display technologies like augmented reality and virtual reality systems.
Innovation Solution
Applying a low baseline power to pre-charge micro-LEDs in a nominally-off state, combined with a shaped current pulse having multiple phases, significantly reduces the time to onset of light emission by minimizing capacitance charging time and asymmetry in response times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional driving methods are used for micro-LEDs, then the device structure is simple, but the response time is slow due to high capacitance charging times
Solution Approach 1:
A baseline current is applied to pre-charge the micro-LED before the main driving pulse is applied. This preliminary action reduces the capacitance charging time when the micro-LED switches from off-state to on-state, significantly improving response time without requiring fundamental changes to the device structure.
Solution Approach 2:
The driving waveform is segmented into two distinct phases: a baseline phase that maintains a low current to pre-charge the device, and a pulse phase that delivers the main driving current. This segmentation allows optimized control of the charging process, reducing overall response time while managing complexity through structured waveform design.
2Speed
If baseline power is applied to pre-charge micro-LED, then response time decreases, but power consumption increases
Solution Approach 1:
Instead of applying full driving power continuously, only a partial baseline current is applied during the nominally-off state. This partial action is sufficient to pre-charge the capacitance and reduce turn-on time, while consuming significantly less power than full continuous operation would require.
Solution Approach 2:
The baseline power level is carefully selected to be greater than zero to enable pre-charging, but kept low enough that light emission remains negligible. This parameter optimization balances the trade-off between response time improvement and power consumption, achieving fast switching without excessive energy use.
3Length of moving object
If micro-LED lateral dimension is reduced below 20 μm, then display resolution improves, but capacitance charging time increases
Solution Approach 1:
The baseline current pre-charges the micro-LED capacitance before the main pulse arrives. This is particularly beneficial for sub-20 μm pixels where capacitance effects are more pronounced, enabling fast modulation speeds despite the small size and associated charging challenges.
Solution Approach 2:
The driving scheme uses periodic baseline current application synchronized with the pixel refresh cycle. This periodic pre-charging maintains optimal charge levels without requiring continuous high current, enabling fast response in miniaturized pixels while managing power and heat constraints.
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 approach decreases the turn-on time to less than 500 ns, enabling faster modulation speeds suitable for advanced display applications by maintaining negligible light emission in the off-state and optimizing internal quantum efficiency.
Implementation Method 1
struggle with slow response times due to high capacitance charging times
Implementation Method 2
driving a first micro light emitting diode (micro-LED)
Data Source
AI summary
A micro-LED driver applies a low baseline power (i.e., a baseline voltage or current) to pre-charge a micro-LED in a nominally-off (i.e., non-light-emitting) state in addition to applying an operating driving power to drive the micro-LED in a light-emitting state. By pre-charging the micro-LED prior to applying the operating driving power, the micro-LED driver significantly decreases the time between application of the operating driving power and onset of emission of light from the micro-LED. In some embodiments, the micro-LED driver applies an operating driving power having multiple phases of current density to reduce the time between application of the operating driving power and onset of emission of light from the micro-LED.