Methods for driving electro-optic displays
A variety of methods for driving electro-optic displays so as to reduce visible artifacts are described. Such methods include (a) applying a first drive scheme to a non-zero minor proportion of the pixels of the display and a second drive scheme to the remaining pixels, the pixels using the first drive scheme being changed at each transition; (b) using two different drive schemes on different groups of pixels so that pixels in differing groups undergoing the same transition will not experience the same waveform; (c) applying either a balanced pulse pair or a top-off pulse to a pixel undergoing a white-to-white transition and lying adjacent a pixel undergoing a visible transition; (d) driving extra pixels where the boundary between a driven and undriven area would otherwise fall along a straight line; and (e) driving a display with both DC balanced and DC imbalanced drive schemes, maintaining an impulse bank value for the DC imbalance and modifying transitions to reduce the impulse bank value.
1. A method of driving an electro-optic display having a plurality of pixels using a first drive scheme, in which all pixels are driven at each transition, and a second drive scheme, in which pixels undergoing a zero white to white transitions are not driven, the method comprising:
performing a first update of the display by applying the first drive scheme to a non-zero minor proportion of the pixels undergoing a zero white to white transition, with the second drive scheme being applied to the remaining pixels; and
performing a second update following the first update by applying the first drive scheme to a different non-zero minor proportion of the pixels undergoing a zero white to white transition, with the second drive scheme is applied to the remaining pixels.
2. A method according to claim 1 wherein the first drive scheme is a global complete drive scheme, wherein a drive voltage is applied to every pixel in the region to which the global complete update drive scheme is applied, and the second drive scheme is a global limited drive scheme, wherein a drive voltage is applied to all pixels except those undergoing a zero, white-to-white transition.
3. A method according to claim 1 wherein the display is divided in groups of contiguous pixels and one pixel in each group has the first drive scheme applied during each transition.
4. A method according to claim 3 wherein the pixels using the first drive scheme at each update are arranged on a parallelogram or pseudo-hexagonal grid.
5. A method according to claim 1 wherein the first drive scheme is a global complete drive scheme, wherein a drive voltage is applied to every pixel in the region to which the global complete update drive scheme is applied, and the second drive scheme is a partial update drive scheme, wherein a drive voltage is applied to all pixels undergoing a non-zero transition.