6T1C AMOLED Pixel Driver Circuit Threshold Voltage Compensation
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Solution Overview
Problem
The instability of threshold voltage in AMOLED pixel driver circuits due to fabrication process variations and aging of TFT materials leads to non-uniform current flow through OLEDs, causing display non-uniformity and instability.
Innovation Solution
A 6T1C AMOLED pixel driver circuit structure is introduced, comprising multiple TFTs and a capacitor, with specific signal phases for initialization, threshold voltage detection, and light-emitting phases to compensate for threshold voltage drift, ensuring current independence from TFT threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a 2T1C pixel driver circuit is used, then the device complexity is low, but the threshold voltage drift of the driving TFT cannot be compensated leading to display non-uniformity
Solution Approach 1:
The pixel driver circuit is divided into multiple functional modules: a driving TFT (first TFT) for current control, a compensation TFT (second TFT) for threshold voltage detection, and additional control TFTs (third, fourth, fifth TFTs) for different operating phases. This segmentation allows independent optimization of driving function and compensation function, resolving the contradiction between circuit simplicity and threshold voltage stability.
Solution Approach 2:
The compensation phase is performed before the light-emitting phase to detect and store the threshold voltage of the driving TFT in advance. By measuring the threshold voltage in the compensation phase and storing it in the capacitor, the circuit prepares the necessary compensation data before actual light emission, ensuring stable current control during the light-emitting phase without requiring complex real-time adjustment mechanisms.
2Reliability
If multiple TFTs and signal phases are added for compensation, then the threshold voltage drift is compensated and current stability is improved, but the device complexity increases
Solution Approach 1:
The capacitor in the circuit serves multiple functions: it stores the threshold voltage during the compensation phase and maintains the gate voltage of the driving TFT during the light-emitting phase. This multi-functionality reduces the need for additional dedicated components, allowing the circuit to achieve current stability while limiting the increase in device complexity.
Solution Approach 2:
The circuit operates in periodic phases including initialization phase, compensation phase, and light-emitting phase. Each phase performs a specific function: initialization resets the circuit state, compensation measures and stores threshold voltage, and light-emitting uses the stored voltage to drive stable current. This periodic operation allows complex compensation functions to be achieved through time-multiplexed simple operations, managing device complexity while improving current stability.
Data Source
AI summary
The invention provides an AMOLED pixel driver circuit and pixel driving method. The AMOLED pixel driver circuit has a 6T1C structure, comprising a first thin film transistor (TFT) (T1), a second TFT (T2) forming mirror relation with the first TFT (T1), a third TFT (T3), a fourth TFT (T4), a fifth TFT (T5), a sixth TFT (T6), a capacitor (C1), and an organic light-emitting diode (OLED) (D1), and receiving a first scan signal (Scan1), a second scan signal (Scan2), a third scan signal (Scan3), a light-emitting signal (EM), a data signal (Data), and a reference voltage (Vref). The circuit can effectively compensate the threshold voltage of the driving TFT to solve the problem of unstable current flowing through the OLED caused by the threshold voltage drift to ensure uniform luminance of the OLED and improve the display quality.