A compact gate driver with bifunctional capacitor for in‐cell touch mobile display

A thin-film transistors (TFTs) integrated gate driver circuit with bifunctional capacitors for in-cell touch with horizontal blanking display mode is proposed in this paper. The coupling capacitor, which conventionally enables low-level-maintaining parts in display periods, is reused to store transfer charges during touch detection periods. Consequently, only nine TFTs and two capacitors are used for a single stage of the proposed gate driver for in-cell touch display. Furthermore, the bifunctional capacitor scheme not only avoids the driving TFT from long-time voltage stress but also suppresses the transfer charges leakage effectively. Therefore, the variation ratios of rising/falling time between adjacent gate driver stages are suppressed within 6%. For a 5.7-in. display with HD+ resolution, the layout of a single gate driver stage is 623 mu m (width) x 171 mu m (height). The proposed gate driver circuit has been prepared with the state-of-the-art hydrogenated amorphous silicon (a-Si:H) TFT manufacturing process. The measured results verified the circuit functions. The gate driver output waveforms are well maintained and being almost independent of touch detection time interval from 100 to 300 mu s.