Eunji Song

Low Power Programmable Shift Register With Depletion Mode Oxide TFTs for High Resolution and High Frame Rate AMFPDs

This paper demonstrates a programmable pulse width shift register using depletion mode oxide TFTs for high resolution and high frame rate displays. The proposed shift register is adopted for a pre-charging scheme in a multi-frame-rate display panel because the gate pulse width is programmable only by adjusting the start pulse width without any additional clock signals and reconfiguration of interconnection. To cope with the depletion-mode issue that TFTs are turned on even at zero gate-source voltage, the modified circuits are introduced, compared to the previous LTPS version of a programmable shift register. In addition, the power consumption is reduced significantly by means of a new inverter circuit. The proposed circuit is verified by SPICE for 50 stages and the estimated power consumption is 5.01 mW in the case of two line time pulse width, which is lower than 9.76 mW of a previous oxide TFT overlap shift register by 48.7%.

Depletion Mode Oxide TFT Shift Register for Variable Frame Rate AMOLED Displays

This letter demonstrates a shift register circuit at the backplane of depletion mode oxide thin-film transistors (TFTs), which can cover variable frame rates for low-power active matrix organic light emitting diode (AMOLED) displays. The proposed scheme focuses on the stable gate control of a pull-up TFT by securing the charging and discharging paths at the wide operating frequency range. In a prototype high-definition (HD: 1366 × 768) AMOLED panel, it is ensured that fabricated shift registers operate at the wide frame frequency range from 1 to 240 Hz. The measured current consumptions are 30, 4, 6, and 5.8 mA for four clock signals, VGH of 24 V, VGL1 of -6 V, and VGL2 of -14 V at a frame rate of 120 Hz.

Low power AMOLED driving scheme based on reduced data supply voltage

This paper demonstrates a new driving scheme which allows reducing the supply voltage of data drivers for low power active matrix organic light emitting diode (AMOLED) displays. The proposed technique drives down the data voltage range by 50%, which subsequently diminishes in the peak power consumption of data drivers at the full white pattern by 75%. Because the gate voltage of a driving thin film transistor (TFT) covers the same range as a conventional one by means of a level-shifting scheme, the low data supply scheme achieves the equivalent dynamic range of OLED currents. The normalized power consumptions have been kept at the lower level than 0.25.