OLED Pixel Driving Circuit With Vth and Vdd Compensation
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Solution Overview
Problem
OLED display panels experience uneven display due to variations in threshold voltage and power supply voltage, leading to inconsistent brightness across the panel.
Innovation Solution
A display driving circuit and method that includes a compensation unit to write reference voltage, power supply voltage, and threshold voltage into a storage unit, compensating for these variations to stabilize the driving current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If current-driven method is used to drive OLED, then brightness can be controlled by driving current, but threshold voltage variations of driving transistors cause uneven display
Solution Approach 1:
The patent applies preliminary action by measuring and storing the threshold voltage of each driving transistor before the display operates normally. During an initialization phase, the circuit writes the measured threshold voltage into a storage unit (capacitor), so that during normal operation, the stored voltage compensates for transistor variations, ensuring uniform display brightness across all pixels.
Solution Approach 2:
The patent implements feedback by measuring the actual threshold voltage of each driving transistor and using this measured value to adjust the driving current. The storage unit holds the measured threshold voltage, and this information feeds back into the driving circuit to compensate for variations, creating a closed-loop system that maintains display uniformity.
2Power
If power supply voltage Vdd is transmitted through metal lines, then power can be delivered to OLEDs, but voltage drop during transmission causes uneven display especially in large-sized panels
Solution Approach 1:
The patent applies preliminary action by measuring and storing the power supply voltage at each pixel location before normal operation. During the initialization phase, the actual power supply voltage (accounting for expected voltage drops) is written into the storage unit, so that during display operation, the stored voltage value compensates for the voltage drop, ensuring uniform brightness across large panels.
Solution Approach 2:
The patent implements feedback by measuring the actual power supply voltage at each location and using this information to adjust the driving current. The storage unit holds the measured voltage, and this feedback information is used to compensate for voltage drops in the metal lines, maintaining consistent display quality across the entire panel.
3Manufacturing precision
If film quality is made uniform during manufacturing, then transistor performance can be consistent, but achieving absolute uniformity is difficult in practice
Solution Approach 1:
The patent applies self-service by having each pixel circuit automatically measure and store its own driving transistor's threshold voltage and the local power supply voltage. Each circuit compensates for its own variations without requiring external intervention or complex manufacturing processes, making the system self-correcting and easier to manufacture at scale.
Solution Approach 2:
The patent changes the operating parameters by storing voltage values that represent the actual state of each transistor and power supply location. By measuring and storing these parameters (threshold voltage and power supply voltage) during initialization, the system adapts to manufacturing variations without requiring perfect manufacturing uniformity.
Data Source
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AI summary
A display driving circuit (100), a display driving method and a display panel. The display driving circuit (100) comprises a first transistor (110), a storage unit (120), a first light-emitting control unit (150), a compensation unit (140), a data writing unit (130) and a second light-emitting control unit (160), wherein the storage unit (120) is connected to a first node (A) and a second node (B); the first light-emitting control unit (150) is connected to a first light-emitting control line (350), a voltage drain drain high-voltage end (370) and the first node (A); the compensation unit (140) is connected to the second node (B), a third node (C), a fourth node (D), a first scan line (310) and a reference voltage line; the data writing unit (130) is connected to the first scan line (310), a data line (330) and the third node (C); the second light-emitting control unit (160) is connected to a second light-emitting control line (360), the fourth node (D), and an anode of a display light-emitting unit (200); and a cathode of the display light-emitting unit (200) is connected to a voltage drain drain low-voltage end (380). A threshold voltage (Vth) and a voltage drain drain (Vdd) are compensated by the compensation unit (140), such that the influence of the threshold voltage (Vth) and the voltage drain drain (Vdd) on a driving current is eliminated, and thus the problem of uneven display of the display panel is improved.