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An analog pulse‐width‐modulation (A‐PWM) Micro‐LED (μLED) pixel circuit based on low‐temperature‐polysilicon (LTPS) thin‐film transistors (TFTs) for mobile displays is proposed. The progressive‐emission mode is implemented using a single Sweep (SW) signal by in‐pixel logic operation circuits. By adjusting the emission time of the progressive‐emission mode, the μLED is biased with the maximum quantum efficiency (EQE). Consequently, the static power consumption of proposed pixels is reduced by 29.2%, compared with conventional schemes. [ABSTRACT FROM AUTHOR]

A compact gate driver using p‐type low‐temperature polycrystalline silicon (LTPS) thin‐film transistors (TFTs) was proposed for Micro‐Light Emitting diodes (μLEDs) display using progressive emission analog pulse‐width modulation (A‐PWM) approach. The gate driver contains a simple waveform shaping module and outputs multiple sweep signals, including SW[n], EM[n], and S[n], by reusing the bootstrap node. Compared with conventional schemes, the proposed gate driver renders static power consumption reduction of the μLED display by 29.2%. [ABSTRACT FROM AUTHOR]

A pulse‐width‐modulation (PWM) pixel circuit for Micro‐LED display based on low‐temperature poly‐silicon and oxide (LTPO) thin‐film transistor (TFT) is proposed. The PWM falling‐time is reduced to 10 μs, which is only 1/10 of conventional PWM pixel schematics, thanks to the high gain dynamic CMOS inverter for converting data voltage to PWM waveforms and an independent diode‐connected compensation structure for generating constant driving current. The maximum error of PWM conversion and driving current of Micro‐LED is less than 1%, despite VTH shift of oxide TFT ±2 V or VTH variation of LTPS TFT ±1 V. Furthermore, high display resolution above 270 PPI is obtained as the pixel layout reduced to 94 μm×94 μm due to the simplified pixel structure. [ABSTRACT FROM AUTHOR]

A pulse-width-modulation (PWM) pixel circuit for Micro-LED displays is proposed based on low-temperature poly-silicon and oxide (LTPO) thin-film transistors (TFTs). The pixel circuit features fast PWM transition, as the PWM falling-time is less than 20 μs thanks to the high-gain dynamic inverter. Furthermore, the proposed pixel circuit can compensate the degradation and non- uniformities of TFT characteristics of LTPO TFTs through auto- zeroing configuration of the dynamic inverter and a diode- connected threshold voltage compensation structure. The error rate of luminous time is less than 3.2% and the error rate of current is less than 1% under VTH shift of oxide TFT ±2 V or LTPS TFT ±1 V. [ABSTRACT FROM AUTHOR]

For large-area electronic applications, the mechanism of the leakage current in oxide-semiconductor thin-film transistors (TFTs) has become a critical issue. In this work, the impact of the irradiation location on the photo-leakage current of zinc oxide (ZnO) TFTs is investigated. The photo-leakage current of the ZnO TFTs is not only dependent on the light irradiation but it is also dependent on the parasitic capacitance between the drain electrode and the floating gate metal. The photo-leakage current of the source-half irradiation TFT is larger than that of the drain-half irradiation TFT. To explain this phenomenon, the profile of the electric potential and the electron concentration is analyzed by two-dimensional device simulation. It is found that the floating gate metal plays the dominant role in the photo-leakage current. This research provides insight into TFT structure optimization and high-performance TFT process development. [ABSTRACT FROM AUTHOR]

This paper demonstrates a novel low‐temperature‐poly‐Si thin‐film transistors (LTPS TFTs) gate driver with tunable width for low‐grey level brightness adjustment of active‐matrix organic light‐emitting diode (AMOLED) display. The width of output pulses can be tuned accordingly by changing the number of input pulses, to avoid changing the frequency, duty ratio, or increasing the numbers of the external clock‐lines. The proposed circuit still works well when outputting 10 ms pulse with leakage current above 1.45 nA. [ABSTRACT FROM AUTHOR]

An OLEDoS microdisplay system is proposed in this paper, which includes a voltage‐driving pixel circuit, an OLED threshold voltage detection method, and a fast‐progressive compensation scheme. The measurement result shows that the range of the programming display voltage of the proposed voltage‐driving pixel circuit is 5.15 times larger than the gate‐source voltage difference of the driving transistor. The measured lowest current of a pixel can be as low as 2.89 pA. [ABSTRACT FROM AUTHOR]

In this work, we proposed a voltage‐programmed AMOLED pixel circuit using amorphous InGaZnO thin‐film transistors (a‐IGZO TFTs). For every display frame, thanks to the capacitive coupling method, the gate‐source voltage of the driving transistor is programmed through a zero to a positive value process, i.e. a unipolar sweeping direction is maintained for the driving transistor, to suppress the electrical hysteresis effects. In addition, the threshold voltage variation of the driving transistor can also be compensated through a source follower structure. Simulation results indicate that the relative current error is less than 30% for threshold voltage variations of ± 0.4 V. [ABSTRACT FROM AUTHOR]

A 31-inch 4K flexible active-matrix organic light-emitting diode (AMOLED) display integrating with gate driver on the array (GOA) technology has been proposed and fabricated on a polyimide substrate. The GOA circuits, composed of two series-connected thin-film transistors (TFTs) and dual low-voltage power structure, are introduced to decrease the leakage current in TFTs. They are arranged symmetrically along the sides of the display. Inkjet printing (IJP) OLED process is used to reduce the number of sub-pixels from four (R/G/B/W) in commercial white OLED process to three (R/G/B) and a high pixel density in the display (144 pixels per inch) is achieved. Moreover, top-gated (TG) amorphous indium-gallium-zinc oxide (IGZO) TFTs with good electrical and mechanical reliability, have been successfully utilized to decrease the capacitance load in the display and improve signal transfer speed in GOA. Finally, this 31-inch flexible AMOLED display was operated for 500h under accelerating test conditions of 60°C and 90% humidity. [ABSTRACT FROM AUTHOR]

This paper presents a proposed capacitance readout circuit that enables a quadrupled (x4) output strength. A symmetric cross-coupling structure is proposed to amplify the voltage difference between two adjacent channels; hence, the detected signal can be integrated twice every clock cycle. Compared with conventional schematics, the proposed readout circuit shows an increased output strength for integration times within dozens of μs. In addition, the measurements show that the integrator resistors should be less than 1 kΩ to suppress the resistance–capacitance delay effects. Although the proposed capacitance readout circuit is implemented using discrete transistors, it has a good signal integrity at an operating clock cycle of 100 µs. Therefore, the proposed readout circuit is a promising way to detect small capacitance variations with short integration times. [ABSTRACT FROM AUTHOR]

A new pixel circuit is proposed for the realization of high resolution and high uniformity organic light-emitting diode on silicon (OLEDoS) microdisplays in this article. A compensation scheme is adopted to mitigate the influence of threshold voltage variation of the driving transistor on display uniformity. Furthermore, two coupling capacitors are used to reduce the voltage at the gate terminal of the driving transistor in order to extend the data voltage range. The performance of the proposed pixel circuit is verified in an industrial 0.18- $\mu \text{m}$ CMOS process. Simulation results show that the data voltage of the proposed pixel circuit ranges from 0.5 to 3.12 V, which is up to $4.37\times $ wider than the previously published pixel circuits. The emission current error of the proposed pixel circuit varies from −2.1% to 2.08%, under the condition of ±5 mV threshold voltage variation for the driving transistor. The maximum emission current error changes from −10.36% to −2.62% when the OLED turn-on voltage is increased by 5 to 20 mV due to device aging. Furthermore, the proposed pixel circuit only occupies a layout area of $8.1\,\,\mu \text{m}\,\,\times {4}\,\,\mu \text{m}$. [ABSTRACT FROM AUTHOR]

In this work we present a DC‐DC converter based on metal oxide thin film transistors (TFTs) for passive radio frequency identification (RFID) tags. To increase the voltage conversion ratio, the cross‐coupled structure with positive feedback from adjacent stages is proposed. Compared with conventional DC‐DC converter with separation block, the proposed circuit features the decreased threshold voltage drop, the reduced on‐resistance of switch transistor, the improved driving capability and the increased power efficiency. The simulated results reveal that the output voltage and maximum power efficiency for proposed two‐stage DC‐DC converter are 16.6 V and 52% at a output current of 550 µA, which are 12.6 V and 42% at a output current of 250 µA for conventional designs. [ABSTRACT FROM AUTHOR]

A readout circuit for large sized capacitive touch screens is presented in this letter. Being different from the conventional readout circuit, the phase conversion module is inserted between the differential sensing structure and the integrating amplifier, to take advantage of both the positive and negative edge of the touch sensing signal for the following integrator. Thus, the sensing output value can be increased as the touch signals are integrated by twice for every clock cycle. Both simulation and measurement results verify that, thanks to the insertion of the proposed phase conversion module, the amplitude of touch sensing circuit’s output is increased from 1.4 to 2.8 V. In addition, compared with the frequency increasing method, the proposed scheme features an increase of 40% in the sensing output voltage. [ABSTRACT FROM AUTHOR]

Using low-temperature poly-silicon thin-film transistors (LTPS TFTs) as a basis, a pixel circuit for an active matrix organic light-emitting diode (AMOLED) with narrow bezel displays was developed. The pixel circuit features mono-type scanning signals, elimination of static power lines, and pixel-integrated emitting control functions. Therefore, gate driver circuits of the display bezel can be simplified efficiently. In addition, the pixel circuit has a high-resolution design due to an increase of the pulse width of the scan signal to extend the threshold voltage and internal–resistance drop (IR drop) detection period. Further, regarding the influences of process–voltage–temperature (PVT) variation in the pixel circuit, comparison investigations were carried out with the proposed circuit and other pixel circuits with mono-type scanning signals using Monte Carlo analysis. The feasibility of the proposed pixel circuit is well demonstrated, as the current variations can be reduced to 2.1% for the supplied power reduced from 5 V to 3 V due to IR drop, and the current variation is as low as 10.6% with operating temperatures from –40 degrees to 85 degrees. [ABSTRACT FROM AUTHOR]