Driving of electrowetting displays
The invention relates to a method of driving an electrowetting display which includes a plurality of electrowetting elements, the display comprising at least one first fluid and a second fluid immiscible with each other, each of the electrowetting elements comprising at least one surface area. In a first, relatively low voltage, driving state of an electrowetting element the second fluid tends to cover the at least one surface area, and in a second, relatively high voltage, driving state of an electrowetting element the first fluid tends to cover the at least one surface area. The method comprises: providing a voltage booster circuit to generate a voltage signal to be applied across one or more selected ones of the plurality of electrowetting elements; and during driving of the one or more selected elements in the second driving state, selectively switching the voltage booster circuit on and off such that the voltage booster circuit is operative only some of the time and the voltage signal includes a voltage ripple variation. The invention further relates to electrowetting display apparatus adapted to perform the method of the invention.
1. A method of driving an electrowetting display having a high quality display mode and a low power mode, the display including a plurality of electrowetting elements and comprising at least one first fluid and a second fluid immiscible with each other, each of said electrowetting elements comprising at least one surface area, wherein in a first, relatively low voltage, driving state of an electrowetting element said second fluid tends to cover said at least one surface area, and in a second, relatively high voltage, driving state of an electrowetting element said first fluid tends to cover said at least one surface area,
the method comprising:
providing a voltage booster circuit to generate a voltage signal to be applied across one or more selected ones of said plurality of electrowetting elements; and
during driving of said one or more selected elements in said second driving state, selectively switching said voltage booster circuit on and off such that said voltage booster circuit is operative only some of the time and said voltage signal includes a voltage ripple variation;
a magnitude of the voltage ripple variation being larger in the low power mode than in the high quality display mode.
2. A method according to claim 1 , wherein said voltage booster circuit is operative less than half of the time, on average.
3. A method according to claim 2 , wherein said voltage booster circuit is operative less than a quarter of the time, on average.
4. A method according to claim 3 , wherein said voltage booster circuit is operative less than one tenth of the time, on average.
5. A method according to claim 1 , wherein said voltage booster circuit is switched on and off according to a fixed scheme.
6. A method according to claim 1 , wherein said voltage booster circuit is switched on and off according to a variable scheme.
7. A method according to claim 6 , wherein said variable scheme is controlled in dependence on one or more control signals which are dependent on feedback from an output of said voltage booster circuit.
8. A method according to claim 6 , wherein said variable scheme is controlled in dependence on one or more control signals which are not dependent on feedback from an output of said voltage booster circuit.
9. A method according to claim 1 , wherein said electrowetting display is a segmented display in which said electrowetting elements are arranged in image regions and each of said image regions corresponds with a different segment of the display, said selected elements corresponding to selected segments.
10. A method according to claim 1 , wherein a plurality of said electrowetting elements are fluidly interconnected and arranged such that said first fluid is capable of conveying said voltage signal to each of said plurality of interconnected electrowetting elements.
11. Electro-optic display apparatus adapted to perform the method of claim 1 .