Pixel Circuit Leakage Current Control for Variable Frame Flicker
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Solution Overview
Problem
Display apparatuses experience luminance differences between basic and variable frame periods due to delays in the on-slew of light emitting elements, leading to flicker issues when displaying low grayscale images in synchronization with variable frame frequencies.
Innovation Solution
A display apparatus and pixel design that controls a leakage current of the driving current flowing into the light emitting element during variable frame periods by activating a dimming signal, which is not present in basic frame periods, to match the length of the blank period, thereby reducing luminance differences and improving image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If variable frame frequency is used to prevent tearing phenomenon, then image synchronization with host processor is improved, but luminance difference between basic and variable frame periods occurs causing flicker
Solution Approach 1:
The patent applies preliminary action by controlling the on-slew of light emitting elements in advance during the blank period. Specifically, the on-slew control signal is applied earlier in the blank period to ensure that the light emitting elements reach their target luminance level before the active display period begins, preventing luminance differences between basic and variable frame periods.
Solution Approach 2:
The patent employs parameter changes by adjusting the timing and duration of the on-slew control signal based on frame type. The on-slew period is modified between basic frame periods and variable frame periods, changing the electrical parameters applied to the light emitting elements to compensate for the different blank period lengths and maintain consistent luminance.
2Productivity
If blank period is extended in variable frame period, then frame frequency synchronization is achieved, but on-slew delay causes luminance difference
Solution Approach 1:
The patent uses preliminary action by performing the on-slew transition during the extended blank period before the active display begins. The light emitting elements are prepared in advance to reach their target state, ensuring that when the active period starts, there is no visible luminance difference despite the varying blank period length.
Solution Approach 2:
The patent applies preliminary anti-action by counteracting the potential luminance difference before it can manifest. The on-slew control is applied during the blank period to pre-compensate for the effects of varying frame rates, preventing the luminance inconsistency from occurring during the visible display period.
3Illumination intensity
If on-slew delay is reduced to prevent luminance difference, then luminance consistency is improved, but additional control complexity is introduced
Solution Approach 1:
The patent applies universality by using a single on-slew control signal mechanism that serves multiple functions. The same control signal path and circuitry are used for both basic frame periods and variable frame periods, with only the timing and duration parameters being adjusted. This avoids the need for separate control systems while maintaining luminance consistency.
Solution Approach 2:
The patent employs parameter changes by modifying the temporal characteristics of the existing control signal rather than introducing new control mechanisms. The on-slew period duration and timing are adjusted as parameters based on the frame type, allowing luminance consistency to be maintained through simple parameter modification rather than complex additional circuitry.
Data Source
AI summary
A pixel includes a capacitor including a first electrode and a second electrode, a first transistor which generates a driving current, a second transistor which applies a data voltage to the first electrode of the capacitor, a third transistor which applies an initialization voltage to the second electrode of the capacitor, a fourth transistor which generates a leakage current in response to a dimming signal, and a light emitting element which emits light based on a residual driving current, where the residual driving current is obtained by subtracting the leakage current from the driving current.