A two-stage driving circuit of a one-chip TFT-LCD driver IC for portable electronic devices is proposed. The driving buffers of the new circuit are built in the γ-correction circuit rather than in the source driver. The power consumption,die area, and driving capability of the driving circuit are discussed in detail. For a two-stage driving circuit with 13 driving buffers, the settling time of the driving voltage within 0.2% error is about 19.2μs when 396 pixel-loads are driven by the same grayscale voltage. The quiescent current of the whole driving circuit is 518μ~A,and the power consumption can be reduced by 77%. The proposed driving circuit is successfully applied in a 132RGB × 176-dot,260k color one-chip driver IC developed by us for the TFT-LCD of mobile phone, and it can also be used in other portable electronic devices, such as PDAs and digital cameras.
An area-saving and high power efficiency charge pump is proposed, and methods for optimizing the operation frequency and improving the power efficiency are discussed. Through sharing coupling capacitors the proposed charge pump realizes two DC-DC functions in one circuit, which can generate both positive and negative high voltages. Due to sharing of the coupling capacitors, as compared with a previous charge pump designed by us for a TFT-LCD driver IC, the die area and the amounts of necessary external capacitors are reduced by 40% and 33%, respectively. Furthermore, the charge pump＇s power efficiency is improved by 8% as a result of employing the new topology. The designed circuit has been successfully applied in a one-chip TFT-LCD driver IC implemented in a 0.18 μm low/mid/high mixed-voltage CMOS process.
