Novel voltage programming n-channel TFT pixel circuit for low power and high performance AMOLED displays

• A novel 7T1C pixel circuit is proposed for high resolution, high frame rate, and low power AMOLED displays.
• The whole line time is in use only for charging the data voltage.
• The current non-uniformity is reduced to 2.5% at a 240 Hz full-HD AMOLED display.
• The average compensated voltage error is reduced to 0.18 V, compared to 0.75 V of 5T2C.
• The initialization power consumptions are 98 mW and the dynamic power saving is 98.7% over 5T2C.

This paper proposes a novel pixel circuit for high resolution, high frame rate, and low power AMOLED displays that is implemented with one driving n-channel TFT, six switching n-channel poly-Si TFTs, and a storage capacitor. The proposed pixel circuit adopts the voltage programming scheme for threshold voltage compensation. Because the whole line time is in use only for charging the data voltage, this pixel circuit is applicable to high resolution and frame rate displays. In addition, it compensates voltage variation of OLEDs and voltage drop of supply lines at lower power consumption. On the average, the non-uniformity of a proposed circuit is reduced to 2.5%, compared to 7.1% of the previous one at a 240 Hz full-HD display. On the other hand, the compensation voltage error, which is caused by feed-through and charge injection noises from falling control signals of switching TFTs, is much less in the proposed scheme than in the previous 5T2C structure. The average error of the proposed circuit is reduced to 0.18 V, compared to 0.75 V of the previous one. The initialization power consumption of the 7T1C circuit is reduced to 98 mW, compared to 530 mW of the 5T2C circuit and the average dynamic power saving ratio of data drivers is estimated in the 7T1C pixel as 98.7% over the 5T2C one for 24 test images.