Scan Inverter Circuit Leakage Reduction for OLED Displays
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Solution Overview
Problem
In low refresh rate organic light-emitting diode displays, leakage paths within row driver circuits cause low voltage signals to be inadvertently driven high, leading to inefficiencies and potential image flicker due to current leakage from the gate terminal of the drive transistor.
Innovation Solution
The implementation of a scan inverter circuit with a leakage reduction circuit, which includes transistors and a mode switching transistor to manage the scan signal and prevent leakage by keeping the drain-to-source voltage low during blanking periods, thereby reducing leakage current through the use of additional transistors and capacitors in the gate driver circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If row driver circuits output low voltage signals during blanking times in low refresh rate displays, then power consumption is reduced and refresh rate is lowered, but leakage paths cause the low voltage signal to be inadvertently driven high leading to image flicker
Solution Approach 1:
A leakage reduction circuit is introduced as an intermediary between the row driver circuit and the display pixels. This circuit includes a first transistor coupled between the output of the row driver circuit and the display pixels, and a second transistor coupled between the first transistor and the low power supply line. The leakage reduction circuit acts as a mediator that prevents leakage current from affecting the display pixels while allowing the row driver circuit to maintain low voltage signals during blanking periods.
Solution Approach 2:
The leakage reduction function is extracted as a separate, dedicated circuit block rather than being integrated into the main row driver circuit. By isolating the leakage compensation function in a separate circuit with its own transistors and control logic, the patent removes the harmful leakage effect without compromising the primary scanning function of the row driver circuit.
2Reliability
If additional transistors and capacitors are added to the gate driver circuit to reduce leakage, then leakage current is suppressed and image stability is improved, but device complexity increases
Solution Approach 1:
The gate driver circuit is segmented into functional modules: the main row driver circuit for scanning control, and a separate leakage reduction circuit for suppressing leakage current. Each module has dedicated transistors and control logic, allowing independent optimization and reducing the complexity burden on the main scanning function while addressing the leakage problem.
Data Source
AI summary
A display is provided that includes an array of display pixels that receive data signals from display driver circuitry and that receive control signals from gate driver circuitry. The gate driver circuitry may include a chain of row driver circuits. Each row driver circuit may include a scan driver circuit and a scan inverter circuit. An enable transistor may be interposed between the scan driver circuit and the scan inverter circuit and may be selectively disabled to decouple the scan inverter circuit from the scan driver circuit to allow the scan inverter circuit to operate independent from the scan driver circuit. The scan inverter circuit may include a transistor that receives a scan pulse signal from the scan driver circuit and may further include additional transistors connected in a negative feedback configuration to reduce a drain-to-source voltage across the transistor to reduce leakage across the transistor during blanking times.