AMOLED Pixel Circuit Shutdown Residual Image Control
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Solution Overview
Problem
AMOLED display devices experience residual images due to slow natural discharge of data voltage after shutdown and lack of continuous turn-on voltage for scanning drive chips, which affects the discharge speed and leads to shutdown residual images.
Innovation Solution
A circuit with a third transistor and a voltage comparator is introduced to control the shutdown sequence of voltages, ensuring a discharge path for residual charges by determining the shutdown state based on gamma and data drive voltages, and using a shutdown time sequence controller to manage voltage turn-offs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the AMOLED display device is shut down, then power consumption is reduced, but residual images occur due to slow discharge of data voltage
Solution Approach 1:
The patent applies preliminary action by introducing a discharge transistor that is turned on before the data voltage completely discharges naturally. The control circuit detects when the data voltage drops below a threshold and activates the discharge transistor to accelerate the discharge process, preventing residual images before they can form. This resolves the contradiction by preparing a discharge path in advance while maintaining low power consumption during normal operation.
Solution Approach 2:
The patent uses an intermediary approach by introducing a discharge transistor as a mediator between the data voltage node and ground. This transistor acts as a controlled discharge path that is activated only when needed (when shutdown is detected and voltage threshold is crossed), providing a mechanism to accelerate discharge without requiring continuous power consumption or modifying the entire drive chip architecture.
2Loss of time
If the switching transistor is turned off before data voltage completely discharges, then shutdown response time is improved, but discharge path is blocked and residual images occur
Solution Approach 1:
The patent applies preliminary action by having the discharge transistor activated before the data voltage fully discharges naturally. The control circuit monitors the data voltage and triggers the discharge transistor when the voltage drops below a predetermined threshold, ensuring the discharge path is established in advance to prevent residual images while maintaining fast shutdown response.
Solution Approach 2:
The patent ensures continuity of useful action by maintaining the discharge path through the discharge transistor after the switching transistor turns off. The discharge transistor remains conductive until the data voltage is fully discharged, providing continuous discharge capability that prevents the formation of residual images while allowing rapid shutdown initiation.
3Device complexity
If no discharge path is provided during shutdown, then circuit complexity is reduced, but residual images occur due to trapped charges
Solution Approach 1:
The patent applies the extraction principle by isolating the discharge function into a separate discharge transistor and control circuit, independent from the main drive chip architecture. This extracted discharge mechanism can be integrated with minimal complexity changes to the existing AMOLED display device, providing residual image elimination without requiring a complete redesign of the drive chip.
Solution Approach 2:
The patent uses an intermediary approach by introducing a discharge transistor as a dedicated component that handles the discharge function separately from the switching transistor. This intermediary element provides a specialized discharge path without requiring modification of the entire circuit architecture, maintaining low complexity while effectively eliminating residual images.
Data Source
AI summary
Disclosed are a circuit and a method for driving an AMOLED pixel. The circuit includes a first transistor, a second transistor, and a grayscale storage capacitor. The circuit further comprises a third transistor. A source of the third transistor is connected to a drain of the first transistor; a drain thereof is connected to ground; and a gate thereof is configured to receive a shutdown control signal. The third transistor is turned on under control of the shutdown control signal and a predetermined shutdown sequence of voltages of respective portions of the circuit.