Pixel Driving Circuit for Micro LED Gray Level Control
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Solution Overview
Problem
Micro LEDs experience efficiency decreases at low current densities, leading to poor gray level modulation and potential color shifts in display, as existing pixel driving circuits fail to ensure output characteristics and maintain color accuracy during gray level changes.
Innovation Solution
A pixel driving circuit is designed with a driving circuit and a light-emitting duration control circuit, which includes sub-circuits for reset, switching, and voltage control, allowing for precise control of the light-emitting period and connection between the driving circuit and the light-emitting element, thereby adjusting gray levels and preventing color shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If current density is used to modulate gray levels, then gray level control is achieved, but efficiency decreases at low gray levels and color shifts occur
Solution Approach 1:
The patent changes the control parameter from current density to light-emitting duration (pulse width modulation). By controlling the duration of the light-emitting element's operation rather than the current magnitude, the system achieves gray level modulation without the efficiency degradation and color shifts that occur at low current densities. This parameter substitution resolves the contradiction between ease of gray level control and reliability of output characteristics.
2Illumination intensity
If Micro LED operates at low current density for low gray levels, then low gray level display is achieved, but efficiency decreases
Solution Approach 1:
The patent employs periodic action by controlling the light-emitting element to operate in pulsed modes with varying durations. Instead of using continuous low current density operation for low gray levels, the system uses shorter light-emitting durations within each frame period. This periodic control maintains high current density during active emission (preserving efficiency) while achieving low gray levels through reduced cumulative light output over time.
3Illumination intensity
If current density varies for gray level modulation, then gray level changes are achieved, but color coordinate changes occur
Solution Approach 1:
The patent substitutes current density variation with light-emitting duration variation as the control parameter. By maintaining constant current density (and thus constant color coordinates) while varying the duration of light emission, the system achieves gray level modulation without color shifts. This parameter change decouples intensity control from color stability, resolving the contradiction between gray level modulation capability and color coordinate stability.
Data Source
AI summary
A pixel driving circuit, a pixel driving method and a display device are provided. the pixel driving circuit includes a driving circuit and a light-emitting duration control circuit, a first end of the driving circuit is connected to a first voltage end, a second end of the driving circuit is connected to the light-emitting element, and the driving circuit is configured to control the first end and the second end to connect to each other; the light-emitting duration control circuit is configured to switch on or switch off a connection between the second end of the driving circuit and the light-emitting element, according to a control data voltage input by a control data line and a control initial voltage input by a control initial voltage end.