Chia En Wu

Low-Power Gate Driver Circuit for TFT-LCD Application

This paper presents a novel low-power gate driver circuit fabricated from glass by using hydrogenated amorphous silicon (a-Si:H) technology and a standard five-mask process. The tolerance of the threshold voltage shift of the proposed gate driver circuit can be estimated as 30 V by using an H-SPICE simulator. Measurement results indicate that the rising and falling times of the output waveform are equal to those in the initial state. Moreover, the proposed gate driver circuit can operate reliably at a high temperature (T = 120 °C) for over 360 h. Furthermore, the proposed gate driver circuit reduces power consumption by 77.3% over that of a conventional gate driver circuit.

Low-Power a-Si:H Gate Driver Circuit With Threshold-Voltage-Shift Recovery and Synchronously Controlled Pull-Down Scheme

This paper presents a new low-power gate driver circuit designed by hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs). An attempt is also made to reduce the power consumption resulting from the high-frequency pulldown structure, in which a pair of 0.25-Hz clock signals is used to implement a low-frequency and synchronously controlled pull-down scheme for recovering the threshold voltage shifts of a-Si:H TFTs under the negative gate-to-source voltage and decreasing the used TFTs. Measurement results indicate that the proposed gate driver circuit consumes 98.7 μW/stage, and the output waveforms are very stable without distortion when the proposed circuit is operated at 100 °C for 840 h. Furthermore, the feasibility of the proposed gate driver circuit is demonstrated for the quad-extended-video-graphics-array resolution.

Insertion of Simple Structure Between Gate Driver Circuits to Prevent Stress Degradation in In-Cell Touch Panel Using Multi-V Blanking Method

This letter proposes a simple structure for in-cell touch thin-film transistor liquid crystal displays (TFT-LCDs) that are driven by the multi-V blanking method. The proposed structure is designed to activate the gate driver circuit after the touch sensing period to prevent the driving TFT of the gate driver circuit from exhibiting long-term stress during this period. Measured electrical characteristics of a fabricated hydrogenated amorphous silicon TFT are used to develop a model for the use in a HSPICE simulation. Based on the specifications of a 5.5 in FHD in-cell touch panel, the simulation results demonstrate that when the proposed structure is applied to a gate driver circuit, the error rates of the rising time and falling time between the output waveforms, which respectively precede and follow the touch sensing period, are both less than 2.14%.

Highly Reliable Bidirectional a-InGaZnO Thin-Film Transistor Gate Driver Circuit for High-Resolution Displays

This paper presents a new bidirectional gate driver circuit that utilizes amorphous indium-gallium-zinc oxide thin-film transistors (TFTs). To ensure the compactness of the display system, bidirectional transmission function is implemented by adjusting the sequence of clock signals without extra controlling signal. The lifetime of the proposed gate driver circuit is increased by reducing the drain bias stress of the input TFTs. The measurement results indicate that the proposed gate driver circuit can remain stable for more than 812 h at 70 °C, demonstrating its feasibility and long-term reliability for full high-definition resolution.

Optical Pixel Sensor of Hydrogenated Amorphous Silicon Thin-Film Transistor Free of Variations in Ambient Illumination

This paper presents a primary color optical pixel sensor circuit that utilizes hydrogenated amorphous silicon thin-film transistors (TFTs). To minimize the effect of ambient light on the sensing result of optical sensor circuit, the proposed sensor circuit combines photo TFTs with color filters to sense a primary color optical input signal. A readout circuit, which also uses thin-film transistors, is integrated into the sensor circuit for sampling the stored charges in the pixel sensor circuit. Measurements demonstrate that the signal-to-noise ratio of the proposed sensor circuit is unaffected by ambient light under illumination up to 12 000 lux by white LEDs. Thus, the proposed optical pixel sensor circuit is suitable for receiving primary color optical input signals in large TFT-LCD panels.

Simplified Gate Driver Circuit for High-Resolution and Narrow-Bezel Thin-Film Transistor Liquid Crystal Display Applications

A novel gate driver circuit composed of four thin-film transistors (TFTs) and two capacitors is developed. Three-phase overlapping clock signals are used in multifunction input TFT and driving TFT, so the proposed circuit can have a simple structure. The electrical characteristics of a fabricated amorphous-indium-gallium-zinc-oxide TFT are measured to establish the model of HSPICE simulation. Simulated results confirm that the proposed gate driver circuit generates stable gate pulses according to the specification of a 5.46-in full high-definition panel and the single-stage layout area is 400 μm × 126 μm. These specifications are favorable for high-resolution and narrow-bezel active-matrix liquid crystal displays.

Gate Driver Circuit Using Pre-Charge Structure and Time-Division Multiplexing Driving Scheme for Active-Matrix LCDs Integrated with In-Cell Touch Structures

This paper presents a new gate driver circuit for active-matrix liquid crystal displays with an in-cell touch structure designed by hydrogenated amorphous silicon thin-film transistors. To increase the reporting rate of a touch panel, the proposed circuit can be used to pause display operations to perform touch sensing operations several times per frame. The proposed circuit exploits a pre-charge structure that alleviates the leakage current and long-term stress of a driving TFT during the touch sensing operation. Simulation results confirm that the proposed gate driver circuit can generate a highly uniform output waveform after each touch sensing operation that lasts for 200 μs when the circuit is operate at 85 °C. The variations of the rising and falling time are suppressed below 3.71%, confirming the feasibility of use of the proposed gate driver circuit for an in-cell touch panel.

Hydrogenated Amorphous Silicon Thin-Film Transistor-Based Optical Pixel Sensor With High Sensitivity Under Ambient Illumination

This letter develops an optical pixel sensor that is based on hydrogenated amorphous silicon thin-film transistors. Exploiting the photo sensitivity of the photo TFTs and combining different color filters, the proposed sensor can sense an optical input signal of a specified color under high ambient illumination conditions. Measurements indicate that the proposed pixel sensor effectively reacts to the optical input signal under light intensities from 873 to 12,910 lux, proving that the sensor is highly reliable under strong ambient illumination.

Optical Properties of Hydrogenated Amorphous Silicon Thin-Film Transistor-Based Optical Pixel Sensor in Three Primary Colors

This work investigates the characteristics and optical responses of photo thin-film transistors (TFTs) that are covered with color filters in the three primary colors. The transmission rates of the color filters under the illumination with various wavelengths are presented as a reference for the integration of photo TFTs with conventional color filters. Measurements are made on previously developed white-light photocurrent gating (WPCG) structures with compensating photo TFTs with different aspect ratios to examine the driving capabilities of three photo TFTs. Favorable values of parameters of the applied WPCG structures that yield similar responses are established from the measured outputs of the structures, benefiting the integration of optical input functions with the three primary color optical input signals for large TFT-LCD panels.

Blue-phase pixel circuit design to enlarge operation voltage and combine polarity inversion with a-IGZO thin-film-transistors

This work develops a pixel circuit for in-plane switching blue-phase liquid crystal displays (IPS BPLCDs) integrated with amorphous indium-gallium-zinc-oxide thin-film-transistors (a-IGZO TFTs). The proposed circuit enlarges the range of operation voltage of BPLC by selecting different bias voltage signals to achieve maximum transmittance of BPLCs. Polarity inversion is also combined with the source follower structure. Simulation results show that the proposed circuit increases the operation voltage to -50 V to 50 V and the error voltages over the entire range of operation voltage are all below 1.2 V demonstrating the feasibility and the reliability of the proposed circuit for practical BPLCD applications.