Electrophoretic display driving scheme
View Patent ↗A system and method are disclosed for reducing reverse bias in an electrophoretic display. The system and method include the application of varying levels of voltages across an array of electrophoretic display cells of the electrophoretic display to move the cells towards a stable state in a driving cycle. In addition, the system and method disconnect the voltages from the electrophoretic display cells at a time duration prior to reaching step transitions of the voltages during the driving cycle. Pre-driving approaches apply a first pre-driving voltage at a first polarity to the display cells before driving the display cells with a second driving voltage at a second, opposite polarity. Varying the time duration and amplitude of the pre-driving signals produces further beneficial reduction in reverse bias.
1. A method for driving an electrophoretic display, the method comprising:
applying a first nonzero voltage, having a first polarity, across an array of electrophoretic display cells of the electrophoretic display for a duration of time before initiating a driving cycle; followed immediately by
applying a second nonzero voltage, having a second polarity opposite the first polarity, across the array of the electrophoretic display cells to move the electrophoretic display cells towards a stable state in the driving cycle.
2. The method according to claim 1 , further comprising:
disconnecting the second voltage from the electrophoretic display cells for a first time duration prior to reaching step transitions of the voltages during the driving cycle.
3. The method of claim 2 , further comprising:
maintaining the disconnection between the second voltage and the electrophoretic display cells for a second time duration in addition to the first time duration.
4. The method of claim 3 , further comprising:
discharging the stored charges in the electrophoretic display within the first time duration and the second time duration before reestablishing connection between the second voltage and the electrophoretic display cells.
5. A method, comprising:
applying a first nonzero voltage, having a first polarity, across an array of electrophoretic display cells of an electrophoretic display, for a first time period, followed immediately by
applying a second nonzero voltage, having a second polarity opposite the first polarity, to the array of electrophoretic display cells for a second time period to move the electrophoretic display cells towards a stable state; and
applying about a zero voltage to the array of electrophoretic display cells for a third time period while the electrophoretic display cells remain at the stable state.
6. A method as recited in claim 5 , wherein the first time period is longer than the second time period.
7. A method as recited in claim 5 , wherein the first voltage has a first amplitude and the second voltage has a second amplitude and the first amplitude is greater than the second amplitude.
8. A method as recited in claim 5 , wherein the first time period is longer than the second time period, and wherein the first voltage has a first amplitude and the second voltage has a second amplitude and the first amplitude is greater than the the second amplitude.
9. A method as recited in any of claims 5 , 6 , 7 , or 8 , further comprising applying a reset signal to the display before applying the first voltage and second voltage.
10. A method as recited in claim 5 , wherein the electrophoretic display comprises a first plurality of display pixels that display in a first color and a second plurality of display pixels that display in a second color, wherein the first color contrasts with the second color, the method further comprising:
driving all of the pixels using a third voltage that clears the display to a second color state; and thereafter,
performing the steps of applying the first voltage and applying the second voltage to the first plurality of pixels.
11. A method as recited in claim 10 , further comprising:
(a) performing the steps of applying the first voltage and applying the second voltage to the pixels of the first color; and thereafter,
(b) performing the steps of applying the first voltage and applying the second voltage to the pixels of the second color, wherein the first polarity that is applied in step (a) is opposite to the first polarity that is applied in step (b), and wherein the second polarity that is applied in step (a) is also opposite the second polarity that is applied in step (b).
12. A method as recited in claim 11 , wherein in step (b) the first time period is shorter than the second time period.
13. A method as recited in claim 10 , further comprising:
(a) performing the steps of applying the first voltage and applying the second voltage to the pixels of the second color; and thereafter,
(b) performing the steps of applying the first voltage and applying the second voltage to the pixels of the first color, wherein the first polarity that is applied in step (a) is opposite to the first polarity that is applied in step (b), and wherein the second polarity that is applied in step (a) is also opposite the second polarity that is applied in step (b).
14. A method as recited in claim 11 , wherein in step (a) the first time period is shorter than the second time period.