Pixel Drive Circuit Brightness Uniformity via Energy Storage
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Solution Overview
Problem
In AMOLED display devices, differences in distance between OLEDs and the power supply cause variations in driving current, leading to non-uniform brightness across the display screen.
Innovation Solution
A pixel drive circuit with specific switch circuits and an energy storage circuit is used to regulate the driving current, ensuring it is independent of the power supply voltage by boosting the voltage during the reset and writing phases, allowing the driving current to be controlled by data voltage in the emitting phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the power supply voltage is applied directly to each OLED through lines of different lengths, then the power supply can provide driving current to all OLEDs, but the voltage drops differ due to different distances, resulting in non-uniform brightness
Solution Approach 1:
The patent applies preliminary action by charging the energy storage circuit (capacitor) in advance during the reset phase before the writing and light-emitting phases. This pre-charging ensures that each pixel receives a consistent voltage level regardless of its distance from the power supply, thereby compensating for voltage drops and achieving uniform brightness across the display screen.
Solution Approach 2:
The energy storage circuit acts as an intermediary between the power supply and the light-emitting control circuit. It stores electrical energy and releases it to maintain a stable voltage at the control end, isolating the light-emitting control circuit from voltage fluctuations caused by varying distances from the power supply, thus ensuring uniform driving current and brightness.
2Illumination intensity
If the driving current is directly controlled by the power supply voltage, then the circuit is simple, but the driving current varies with distance from the power supply, affecting brightness uniformity
Solution Approach 1:
The energy storage circuit is charged in advance during the reset phase to a predetermined voltage level. This preliminary charging action ensures that during the subsequent writing and light-emitting phases, the control end of the light-emitting control circuit maintains a stable voltage regardless of distance from the power supply, thereby achieving uniform brightness without requiring complex real-time voltage compensation circuits.
Solution Approach 2:
The energy storage circuit serves itself by automatically charging during the reset phase and then autonomously maintaining the voltage level at the control end during the light-emitting phase. This self-service mechanism compensates for voltage drops without requiring external intervention or complex control logic, thus improving brightness uniformity while keeping the circuit relatively simple.
3Reliability
If the energy storage circuit is charged in the reset phase, then the voltage at the control end is boosted to reduce voltage difference, but additional switch circuits are required
Solution Approach 1:
The switch circuits are designed to perform multiple functions: the first switch circuit not only controls the charging of the energy storage circuit during the reset phase but also serves as part of the light-emitting control circuit during the light-emitting phase. The second and third switch circuits similarly participate in both reset/charging operations and light-emitting control. This multi-functionality reduces the need for separate dedicated circuits, thereby improving voltage stability while limiting the increase in overall circuit complexity.
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
This solution reduces the difference in driving current among OLEDs, resulting in improved uniformity of brightness across the display screen.
Implementation Method 1
an energy storage circuit, the data input circuit is electrically connected to a control end of the light-emitting control circuit through the energy storage circuit, and the energy storage circuit is configured to store electric energy
Data Source
AI summary
A pixel drive circuit, including a data input circuit, an energy storage circuit, a light-emitting control circuit, a first switch circuit, a second switch circuit and a third switch circuit. An end of the first switch circuit is connected with a control end of the light-emitting control circuit, and another end of the first switch circuit is connected with an input of the light-emitting control circuit that is connected to a power supply. An end of the second switch circuit is connected with an output of the data input circuit, and another end of the second switch circuit is grounded, and an output of the light-emitting control circuit is connected to an anode of a light-emitting device. The first switch circuit and the second switch circuit are switched on in a reset phase, and the third switch circuit is switched on in a light-emitting phase.