Pixel Driving Circuit Using High-Frequency Reset for Low-Rate Flicker
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Solution Overview
Problem
Existing OLED displays experience visible flicker at low refresh rates due to hysteresis effects in driving transistors and cross-voltage delays from parasitic capacitance, leading to changes in intra-frame current and gate potential.
Innovation Solution
A pixel driving circuit with an initializing unit, data writing unit, reset unit, and light emitting control unit, utilizing high-frequency scanning cycles to reset node potentials and convert low-frequency flicker into high-frequency flicker unrecognizable to the human eye.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the refresh rate is reduced to lower power consumption, then energy efficiency is improved, but visible flicker occurs due to hysteresis effects and parasitic capacitance
Solution Approach 1:
The patent applies periodic action by introducing a reset operation that occurs multiple times within a single frame period. The reset unit performs periodic resetting of the driving transistor at a frequency higher than the refresh rate (e.g., N times per frame), which suppresses the accumulation of hysteresis effects and parasitic capacitance voltage drops that cause flicker. This allows the display to operate at low refresh rates while maintaining image stability.
Solution Approach 2:
The patent changes the frequency parameter of the reset operation relative to the refresh rate. By operating the reset unit at a frequency that is an integer multiple (N times) of the refresh rate, the system creates a hierarchical frequency structure where high-frequency reset actions suppress low-frequency flicker artifacts, enabling energy-efficient low refresh rate operation without visible flicker.
2Loss of energy
If the refresh rate is reduced, then power consumption is reduced, but hysteresis effect causes intra-frame current changes leading to flicker
Solution Approach 1:
The reset unit performs preliminary resetting of the driving transistor before the light emitting phase occurs. By proactively compensating for hysteresis effects through periodic reset operations at high frequency, the system prevents the accumulation of harmful hysteresis-induced current variations that would otherwise manifest as flicker during the display period.
3Loss of energy
If the refresh rate is reduced, then power consumption is reduced, but cross-voltage delay during OLED charging causes visible flicker
Solution Approach 1:
The high-frequency periodic reset operations charge and discharge the parasitic capacitance multiple times within each frame period. This periodic action prevents the accumulation of cross-voltage delays that would otherwise occur during OLED charging at low refresh rates, thereby eliminating visible flicker while maintaining low power consumption.
Data Source
AI summary
Disclosed are a pixel driving circuit and a driving method thereof, and a display apparatus, the circuit includes a driving transistor; a storage capacitor; an initializing unit configured to transmit an initialization voltage to a second node to charge the storage capacitor; a threshold compensation unit configured to obtain a threshold voltage of the driving transistor in response to a first scanning signal scanned at a first frequency and update a potential of the second node; a data writing unit configured to transmit a data signal to a first node; a reset unit configured to reset a potential of the first node in response to a second scanning signal scanned at a second frequency; a light emitting control unit configured to control light emission of an organic light emitting diode; the second frequency being N times the first frequency, N being an integer greater than or equal to 1.