Pixel Circuit Duty Cycle Control for Grayscale Uniformity
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Solution Overview
Problem
Self-luminous devices in display apparatuses suffer from non-uniform brightness and grayscale uniformity issues due to changes in photoelectric conversion properties with current density, leading to display defects such as grayscale disorder and color shift.
Innovation Solution
A pixel circuit with a driving circuit and control circuits that control the operation of elements like LEDs by adjusting the amplitude and frequency of driving signals, ensuring stable luminous efficiency and grayscale representation through precise control of light-emitting duration and current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If self-luminous devices are used to improve display brightness and response speed, then luminance efficiency is improved, but photoelectric conversion properties change with current density causing grayscale uniformity issues and color shifts
Solution Approach 1:
The patent implements dynamic control of the light emitting element by adjusting the duty cycle of the driving signal. The control circuit varies the ratio of ON-time to total period of the driving signal, enabling dynamic adjustment of the element's operation state. This dynamic control allows the system to maintain stable photoelectric conversion properties across different brightness levels, resolving the grayscale uniformity issue while preserving high luminance efficiency.
Solution Approach 2:
The patent changes the driving parameter from continuous current amplitude control to pulsed duty cycle control. By modifying the driving signal from a continuous analog signal to a pulsed digital signal with variable duty cycle, the system achieves grayscale control without varying the current density during the ON state. This parameter change eliminates the photoelectric conversion property variations that cause grayscale disorder and color shifts.
2Manufacturing precision
If duty cycle control is used to maintain stable photoelectric conversion properties, then grayscale uniformity is improved, but circuit complexity increases due to additional control circuits
Solution Approach 1:
The control circuit in the patent is designed with multi-functionality, serving both as a switching element and a duty cycle regulator. The same control circuit that switches the light emitting element ON and OFF also controls the duty cycle to regulate brightness. This universal design eliminates the need for separate brightness control circuits, reducing overall circuit complexity while maintaining grayscale uniformity through duty cycle control.
3Illumination intensity
If continuous driving signal is used to maintain element operation, then luminance stability is improved, but power consumption increases
Solution Approach 1:
The patent employs periodic pulsing of the driving signal instead of continuous driving. The light emitting element is driven in periodic pulses with controlled duty cycles, allowing it to operate intermittently rather than continuously. This periodic action maintains perceived luminance stability through persistence of vision while significantly reducing average power consumption by keeping the element OFF during the off-period of each pulse cycle.
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
Improves display quality by maintaining efficient luminance and preventing grayscale uniformity issues and color shifts, reducing flicker perception, and optimizing power consumption.
Implementation Method 1
Self-luminous devices in display apparatuses suffer from non-uniform brightness and grayscale uniformity issues due to changes in photoelectric conversion properties with current density
Data Source
AI summary
A pixel circuit includes a driving circuit, a first control circuit and a second control circuit. The driving circuit is configured to receive a data signal in response to a scan signal, and generate, in response to a first enable signal, a driving signal according to a first voltage and the data signal. The first control circuit is configured to: receive a first input signal in response to a first control signal, and transmit a third input signal in response to the first input signal; and receive a second input signal in response to a second control signal, and transmit a second enable signal in response to the second input signal. The second control circuit is configured to transmit the driving signal to an element to be driven in response to one of the third input signal and the second enable signal.