Pixel Circuit Compensation for OLED Power-On Stability
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Solution Overview
Problem
Conventional organic light-emitting diode displays often exhibit abnormal images during the first frame period after power-on due to unstable power supply voltage, causing abnormal operation of pixel circuits and affecting display quality.
Innovation Solution
A pixel circuit is designed with a compensation circuit that selectively transfers a compensated reference voltage based on the instantaneous power supply voltage, stabilizing the voltage at key nodes to maintain consistent drive current, comprising diodes and capacitors to manage voltage changes and ensure stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power supply voltage is applied directly to the pixel circuit during power-on, then the circuit can operate, but the unstable voltage causes abnormal operation and display defects
Solution Approach 1:
The pixel circuit performs preliminary actions by pre-charging capacitors and initializing nodes before normal operation. The reset circuit activates first to set initial voltages, and the compensation circuit pre-adjusts reference voltages to account for upcoming power supply changes, ensuring stable operation during power-on transitions
Solution Approach 2:
The compensation circuit implements feedback by continuously monitoring the power supply voltage and adjusting the reference voltage accordingly. When the power supply voltage changes, the compensation circuit detects this change and modifies the reference voltage to maintain constant drive current through the light-emitting device, eliminating the need for manual intervention
2Speed
If the power supply voltage climbs rapidly from 0V to 4.6V, then power-on is achieved, but this causes abnormal operation of pixel circuits and affects display effect
Solution Approach 1:
The pixel circuit performs preliminary actions by pre-charging capacitors and initializing nodes before normal operation. The reset circuit activates first to set initial voltages, and the compensation circuit pre-adjusts reference voltages to account for upcoming power supply changes, ensuring stable operation during power-on transitions
Solution Approach 2:
The compensation circuit provides beforehand cushioning by pre-adjusting the reference voltage to compensate for the upcoming rapid power supply voltage change. This anticipatory adjustment cushions the impact of the voltage climb on the pixel circuit operation, preventing display abnormalities while maintaining fast power-on speed
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
The solution effectively stabilizes the drive current, preventing the 'splash phenomenon' caused by power supply voltage fluctuations, thereby ensuring consistent and normal display operation even during power-on transitions.
Implementation Method 1
a compensation circuit configured to selectively transfer an uncompensated reference voltage or a compensated reference voltage to a third node, the compensated reference voltage being determined by the uncompensated reference voltage and a compensation voltage, the compensation voltage being related to a rated value of a power supply voltage
Implementation Method 2
provide a path along which a drive current flows from the first power supply terminal to a second power supply terminal through the light-emitting device
Implementation Method 3
a drive circuit configured to control a magnitude of the drive current based on the voltage at the second node and the power supply voltage
Data Source
AI summary
A pixel circuit includes a light-emitting device, a reset circuit, a write circuit, a compensation circuit, a light emission control circuit, and a drive circuit. The compensation circuit is configured to selectively transfer an uncompensated reference voltage or a compensated reference voltage to a third node, the compensated reference voltage being determined by the uncompensated reference voltage and a compensation voltage, the compensation voltage being related to a rated value of a power supply voltage. The light emission control circuit is configured to transfer a voltage at the third node to a first node to cause a change in voltage at the second node. The drive circuit is configured to control a magnitude of a drive current flowing through the light-emitting device based on the voltage at the second node and the power supply voltage.