AMOLED Pixel Circuit Rapid Charging via Transistor Segmentation
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Solution Overview
Problem
Existing AMOLED pixel circuits suffer from slow charging times, limiting their application scope due to the long charging period in current-driving circuits.
Innovation Solution
An AMOLED pixel circuit with a semi-digital constant-current source and a specific transistor configuration that allows for rapid charging by adjusting the width-length ratio of transistors, enabling different current levels for high and low gray scale states, and controlling the charging and discharging of capacitors to expedite the charging process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current-driving circuit is used to achieve uniform and stable display, then the display quality is improved, but the charging time becomes excessively long
Solution Approach 1:
The charging process is divided into two distinct phases: a first charging period using transistor T2 for normal charging, and a second charging period using transistor T6 for rapid charging. This segmentation allows the circuit to switch between different charging modes based on the gray scale requirements, resolving the contradiction between stable display and fast charging.
Solution Approach 2:
The circuit dynamically switches between different transistors (T2 and T6) and different charging currents based on the gray scale level. For low gray scales, the circuit uses the slower T2 transistor for precise control; for high gray scales, it switches to T6 transistor for rapid charging. This dynamic adaptation allows the circuit to maintain display stability while reducing overall charging time.
2Speed
If the width-length ratio of transistors is adjusted to enable rapid charging, then the charging speed is improved, but the current control precision for different gray scales may be affected
Solution Approach 1:
Different transistors (T2 and T6) are designed with different width-length ratios optimized for different functions. Transistor T2 has a smaller width-length ratio for precise current control in low gray scale modes, while transistor T6 has a larger width-length ratio for rapid charging in high gray scale modes. This local optimization of transistor characteristics allows the circuit to achieve both precision and speed in appropriate operating conditions.
Solution Approach 2:
The circuit dynamically selects which transistor to use based on the required gray scale level. The control circuit determines whether to activate T2 or T6 based on the target brightness level, ensuring that the appropriate transistor characteristics (precision or speed) are applied to each specific charging scenario.
Data Source
AI summary
An AMOLED pixel circuit and driving method are disclosed. The AMOLED pixel circuit comprises a first transistor (T1), a second transistor (T2), a third transistor (T3), a fourth transistor (T4), a fifth transistor (T5), a sixth transistor (T6), a seventh transistor (T7), an eighth transistor (T8), a first capacitor (C1), a second capacitor (C2), a current source and a light-emitting device (OLED). The AMOLED pixel circuit can perform a rapid charging in a low gray scale state; different currents may be provided according to information on a high or low gray scale, and thus the AMOLED pixel circuit may be applied widely; an output current during a light-emitting period is a normal operational current of the light-emitting device; therefore not only a charging process is expedited, but also a normal operation of the light-emitting device is ensured.