Region-selective shift register by a single output enable signal for a multiple refresh frequency driving scheme

Many low-power technologies have been developed for high-performance displays. One method is to vary the refresh rate according to the input image, where frequencies are reduced over still images and slow-moving videos. To support the variable refresh rate scheme, the programmable gate driver circuit should be integrated. This paper proposes a thin-film transistor (TFT) shift register of which output pulse is simply controlled by an enable signal. Because the output pulse generation is directly adjusted without the previous programming period, various output pulse sequences are possible with the high flexibility. The shift register is composed by adding six TFTs and one capacitor to a conventional circuit that provides a carry pulse to a next stage. The simulation program with integrated circuit emphasis (SPICE) simulation ensures that gate pulses for any numbers of lines in any regions can be generated within one frame only by applying the enable signal at the corresponding timing, resulting in multiple refresh frequencies in a screen. In addition, it is verified that additional TFTs and capacitor contribute to only the negligible increase in power consumption by 2.1%, compared to a conventional shift register.