AMOLED Shutdown Circuit Prevents Image Retention
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Solution Overview
Problem
In IGZO-based AMOLED display devices, gate stress applied to driving transistors during shutdown leads to image retention due to prolonged voltage on gate electrodes, causing the last image to be retained on the screen when the device is turned back on.
Innovation Solution
A shutdown controlling method and circuit that determines the presence of a shutdown signal, controls the voltage on signal lines to discharge capacitors completely via switching elements, and cuts off power sources to prevent image retention by ensuring the capacitors are fully discharged before shutdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the power source is turned off during shutdown, then energy consumption is reduced, but the capacitor retains charge causing gate stress and image retention
Solution Approach 1:
The patent applies preliminary action by discharging the capacitor before turning off the power source. The control circuit detects the shutdown signal and activates the switching element to discharge the capacitor stored charge to the signal line, ensuring the gate electrode voltage is removed before complete power shutdown, thereby preventing image retention while still achieving energy savings
Solution Approach 2:
The patent extracts the harmful stored charge from the capacitor before shutdown. By using the switching element to transfer the charge from the capacitor to the signal line, the harmful gate stress is removed and extracted from the system before power cutoff, preventing the image retention effect
2Use of energy by stationary object
If the switching element is kept in off state during shutdown, then power consumption is reduced, but the capacitor charge cannot be released causing prolonged gate stress
Solution Approach 1:
The control circuit performs preliminary action by detecting the shutdown signal and switching the switching element to the on state before complete power shutdown. This allows the capacitor charge to be discharged to the signal line through the switching element, removing gate stress before power is fully cut off, thus preventing image retention while minimizing power consumption
Solution Approach 2:
The patent implements periodic control of the switching element based on shutdown signals. The switching element transitions from off state during normal operation to on state during shutdown to discharge the capacitor, then returns to off state after discharge completion, creating a periodic on-off pattern that balances power consumption with gate stress prevention
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
Prevents image retention by ensuring complete discharge of capacitors connected to the gate electrodes of driving transistors, thereby eliminating the effect of gate stress when the display device is turned on again, improving image quality and user experience.
Implementation Method 1
a capacitor arranged between a gate electrode and a source electrode of the driving transistor
Implementation Method 2
control the switching element to be in an on state, thereby to enable the capacitor to be discharged completely toward the signal line
Data Source
AI summary
The AMOLED display device includes a light-emitting source and a display screen provided with a plurality of subpixels. Each subpixel includes a driving transistor, and a capacitor arranged between a gate electrode and a source electrode of the driving transistor and connected to a signal line via a switching element. The shutdown controlling method includes: determining whether or not a shutdown signal has been detected; performing a first control operation when the shutdown signal has been detected, so as to control a voltage on the signal line to be in a first voltage state; and performing a second control operation when the shutdown signal has been detected, so as to control the switching element to be in an on state, thereby to enable the capacitor to be discharged completely toward the signal line in the first voltage state via the switching element.