Sweep Signal Driver Using PWM to Stabilize Inorganic LED Wavelength
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Solution Overview
Problem
Inorganic light emitting diode elements in display devices experience a change in wavelength due to driving current, leading to image quality deterioration when driven similarly to organic light emitting diode elements.
Innovation Solution
A sweep signal driver with multiple stages that output emission and sweep signals, where the pulse width of emission signals is greater than sweep signals, allowing for controlled luminance adjustment by varying the period of driving current while maintaining a constant current, thereby stabilizing the wavelength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If inorganic light emitting diode elements are driven with varying driving current to adjust luminance, then luminance control is achieved, but wavelength changes causing image quality deterioration occur
Solution Approach 1:
The patent applies periodic action by using pulse width modulation (PWM) to control the emission signal. The emission signal is applied periodically with different pulse widths to control luminance, while the driving current remains constant during each pulse, preventing wavelength shifts. This periodic on-off switching allows luminance control without the harmful wavelength variations that occur with continuous current adjustment.
Solution Approach 2:
The patent changes the parameter being controlled from driving current magnitude to pulse width duration. Instead of varying the current amplitude to control luminance (which causes wavelength changes), the invention varies the temporal parameter (pulse width) while maintaining constant current amplitude, thus achieving luminance control without wavelength instability.
2Illumination intensity
If the pulse width of emission signal is increased to improve luminance control, then luminance adjustment capability is enhanced, but the duration of driving current application increases
Solution Approach 1:
The emission signal is structured as periodic pulses with variable widths. By adjusting the pulse width within the periodic cycle, the invention achieves luminance control while limiting the actual duration of current application to only when needed, rather than continuous application. The periodic nature allows the signal to return to zero between pulses.
3Reliability
If sweep signal duration is extended to match emission signal duration, then signal synchronization is improved, but unnecessary current application increases energy consumption
Solution Approach 1:
Both sweep and emission signals are structured as periodic pulses with coordinated timing. The sweep signal pulse width is specifically designed to be shorter than or equal to the emission signal pulse width, creating a periodic pattern where the sweep signal activates only during the necessary scanning period, then returns to idle state, preventing unnecessary energy consumption while maintaining synchronization.
Solution Approach 2:
The sweep signal is applied partially - only for the duration needed to complete the scanning operation across all pixels, rather than being continuously applied to match the full emission signal duration. This partial application achieves the necessary synchronization function without the excessive energy consumption of continuous application.
Data Source
AI summary
A sweep signal driver includes: a kth stage to output a kth emission signal to a kth emission line, and a kth sweep signal to a kth sweep signal line, the kth stage including: first, second, and third pull-up nodes; a node connection circuit between the first pull-up node and the second pull-up node, and between the first pull-up node and the third pull-up node; a first output circuit to output a sweep clock signal of a sweep clock terminal to a first output terminal connected to the kth sweep signal line when the third pull-up node has a gate-on voltage; and a second output circuit to output a gate-on voltage to a second output terminal connected to the kth emission line when the second pull-up node has a gate-on voltage. A pulse of the kth sweep signal linearly changes from a gate-off voltage to the gate-on voltage.