OLED Pixel Driving Circuit Reducing Gate Driving Time
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Solution Overview
Problem
The display effect of conventional AMOLED display panels is affected by the long gate driving time in the display phase, which impacts the performance of transistors T1, T5, and T6.
Innovation Solution
The OLED pixel driving circuit includes a novel configuration with five P-type thin film transistors (T1 to T7) and a capacitor, where specific control and connection arrangements between the transistors and the OLED reduce the number of required control signals from six to four (Scan[n−1], Scan[n], EM, and Vdd), and the charging time of the capacitor is shortened by short-circuiting certain transistor ends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional 7T1C pixel driving circuit is used with six control signals, then the circuit can complete all driving functions, but the gate driving time in display phase becomes very long (about 16.7 milliseconds) which affects display effects
Solution Approach 1:
The patent segments the gate driving function by separating the gate driving transistor (first transistor) from other transistors, and further segments the control signals into four specific signals (Scan[n-1], Scan[n], EM, and Vdd) instead of using six control signals. This segmentation allows the gate driving operation to be optimized independently, reducing the gate driving time in display phase while maintaining complete driving functions.
Solution Approach 2:
The patent implements dynamic control of the gate driving transistor through selective connection to different scan signals (Scan[n-1] or Scan[n]) based on the driving phase. During display phase, the transistor is controlled to minimize on-time, while during preparation and compensation phases, it is controlled appropriately for those operations. This dynamic adjustment reduces the overall gate driving time in display phase.
2Loss of time
If gate driving time is reduced to improve display effects, then display quality improves, but the charging time of capacitor may be insufficient affecting data storage
Solution Approach 1:
The patent performs capacitor charging in advance during the preparation phase (t1) and compensation phase (t2) when the first transistor is properly controlled to charge the capacitor fully. By completing the charging operation before the display phase begins, the transistor can be turned off or minimized during display phase without affecting the capacitor's charged state, thus maintaining data storage reliability while reducing display phase gate driving time.
Solution Approach 2:
The patent uses periodic control signals (Scan[n-1], Scan[n], EM) to periodically charge the capacitor during preparation and compensation phases, then maintains the charge during display phase by minimizing transistor on-time. This periodic charging action ensures the capacitor is fully charged before display phase while allowing gate driving time to be reduced during the actual display period.
Data Source
AI summary
An organic light emitting diode (OLED) pixel driving circuit and a display panel are disclosed. The OLED pixel driving circuit is a 7T1C type pixel driving circuit consisting of a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a sixth transistor, a seventh transistor, a capacitor, and an organic light emitting diode. Each of the first, second, third, fourth, fifth, sixth, and seventh transistors has a control end, a first end, and a second end, wherein the control end and the second end of the seventh transistor are coupled, the control end and the second end of the fourth transistor are coupled, and the second end of the fourth transistor and the second end of the seventh transistor are not connected to each other.