Scan Driver Leakage Current Reduction via Clock-Controlled Transistors
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Solution Overview
Problem
In large-size organic light emitting diode (OLED) displays, characteristic deviations between driving transistors and resistance increases due to deterioration, leading to moiré patterns and uncompensated leakage currents, affecting scan and light emitting signals, which can result in abnormal voltage output and uncompensated deviations.
Innovation Solution
A scan driver and light emitting driver design incorporating p-channel field effect transistors with specific transistor configurations and capacitors to manage clock signals and power source voltages, reducing leakage currents by ensuring uniform voltage levels and compensating for transistor deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the application time of scan signal and light emitting signal is increased to compensate characteristic deviation, then the compensation accuracy is improved, but leakage current increases affecting signal output
Solution Approach 1:
The patent applies dynamic control by using clock signals to periodically switch transistors on and off, and by dynamically adjusting the timing of signal application. The scan driver and light emitting driver use clocked transistor switching to maintain signal integrity while limiting the duration of voltage application, thereby reducing leakage current effects while preserving compensation accuracy through controlled timing sequences.
Solution Approach 2:
The patent changes the temporal parameters of signal application by using clock signals to control the duration and timing of transistor switching. By adjusting the clock signal frequency and phase, the system optimizes the balance between maintaining sufficient signal application time for accurate compensation and minimizing the total time transistors remain conductive, thus reducing leakage current accumulation.
2Reliability
If p-channel transistors are used to reduce leakage current, then signal output stability is improved, but device complexity increases
Solution Approach 1:
The patent employs p-channel transistors that serve multiple functions: they act as switching elements controlled by clock signals, function as voltage transmission gates, and provide inherent leakage current reduction. This multi-functionality allows the same transistor type to address both signal control and leakage mitigation without requiring additional specialized components, thereby limiting the increase in device complexity.
Solution Approach 2:
The patent introduces clock signals as intermediary control elements that mediate between the power source and the transistors. These clock signals coordinate the switching of multiple p-channel transistors, providing a unified control mechanism that simplifies the overall device architecture while enabling complex timing sequences necessary for reducing leakage current effects.
Data Source
AI summary
A scan driver includes: a plurality of scan driving blocks including an output terminal outputting a scan signal to a scan line; a first transistor transmitting a voltage of a power source to the output terminal; a second transistor transmitting a clock signal to the output terminal; and a third transistor including a gate electrode connected to a node formed with a gate-on voltage turning on the second transistor, one terminal connected to the power source, and the other terminal connected to the gate electrode of the first transistor. The scan driver may reduce the influence of a leakage current even though application of the scan signal is increased, and a scan signal of a uniform voltage level may be output.