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| (Source: LG Display) |
LG Display has secured another chance to obtain patent protection for an OLED pixel circuit technology designed to improve image quality by compensating for threshold voltage shifts in drive transistors.
On Aug. 8, the Korean Intellectual Property Trial and Appeal Board (KIPTAB) overturned a refusal by the Korean Intellectual Property Office (KIPO) and remanded the case to the office for further examination. LG Display had filed the appeal in June after KIPO denied registration of its application titled “Pixel Circuit and Display Device Including the Same” (No. 10-2021-0176373), filed Dec. 10, 2021.
The application, which also formed the basis for a divisional filing on Feb. 3, 2025 (No. 10-2025-0013093), covers circuitry for active-matrix OLED and other electroluminescent displays. The invention addresses limitations in source-following compensation schemes, where parasitic capacitance at the gate node can cause voltage loss during threshold voltage sensing, reducing compensation accuracy and range.
LG Display’s design adds three capacitors to the pixel circuit to minimize loss during sensing and transfer, adjust first- and second-stage coupling ratios, and deliver the sensed voltage to the gate node with minimal loss. By tuning capacitor ratios and using a multi-step drive sequence — initialization, sensing, first transfer, data writing, second transfer, boosting and emission — the circuit maintains stable OLED drive current across a wide range of ΔVth values.
According to the company, the invention overcomes structural limits in conventional source-following compensation by optimizing capacitor placement and ratios, enabling more accurate threshold voltage delivery and improved image quality.
By PatenTrip
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