US Patent 7126577 Electrophoretic active matrix display device

The invention relates to a display device comprising electrophoretic particles, a display element comprising a pixel electrode and an associated counter electrode, between which a portion of the electrophoretic particles is present, and a controller for supplying a drive signal to the electrodes to bring the display element to a predetermined black or white state, corresponding to the image information to be displayed. In order to improve the refresh time of the display, the controller is further arranged to supply a preset signal preceding the drive signal comprising a preset pulse representing an energy which is sufficient to release the electrophoretic particles at a first position near one of the two electrodes corresponding to a black state, but is too low to enable the particles to reach a second position near the other electrode corresponding to a white state.