Coordinated top electrode - drive electrode voltages for switching optical state of electrophoretic displays using positive and negative voltages of different magnitudes

A system for driving an electrophoretic medium, comprising:

• an electrophoretic display including,
• a light-transmissive top electrode at a viewing surface,
• a first drive electrode,
• a second drive electrode,
• an electrophoretic medium disposed between the top electrode and the first and second drive electrodes;
• a power source capable of providing a positive voltage and a negative voltage, where the magnitude of the positive voltage and the negative voltage are different relative to ground;
• a controller coupled to the top electrode driver, the first drive electrode driver, and the second drive electrode driver, wherein the controller is configured to cycle the top electrode between the positive voltage, the negative voltage, and ground, while coordinating driving the first drive electrode and the second drive electrode, wherein the controller is configured to provide:
• in a first frame, the positive voltage to the top electrode, the negative voltage to the first drive electrode, and the positive voltage to the second drive electrode,
• in a second frame, the negative voltage to the top electrode, the negative voltage to the first drive electrode, and the negative voltage to the second drive electrode,
• in a third frame, the ground voltage to the top electrode, the ground voltage to the first drive electrode, and the positive voltage to the second drive electrode, and
• in a fourth frame, the positive voltage to the top electrode, the positive voltage to the first drive electrode, and the positive voltage to the second drive electrode,
• such that, after four frames, the first drive electrode has received a drive impulse having a magnitude equal to the sum of the magnitudes of the positive and negative voltages while the second drive electrode has received a drive impulse having a magnitude equal to the magnitude of the positive voltage, and the first drive electrode and the second drive electrode received the respective impulses at different times.