Super Low Voltage Driving Of Displays

• US 20120182282A1
• Filed: 01/19/2011
• Published: 07/19/2012
• Est. Priority Date: 01/19/2011
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Polymer Vision B.V. (Wistron Corporation)
• Inventors: van Veenendaal, Erik, Huitema, Hjalmar Edzer Ayco
• Granted Patent: US 8,780,103 B2
• Time in Patent Office: Days
• US Class Current: 345/212
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• CPC Class Codes: G09G 2320/0214 with crosstalk due to leakage current of pixel switch in active matrix panels
• CPC Class Codes: G09G 2320/0219 Reducing feedthrough effects in active matrix panels, i.e. voltage changes on the scan electrode influencing the pixel voltage due to capacitive coupling
• CPC Class Codes: G09G 2320/0257 Reduction of after-image effects
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: G09G 3/344 based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167

Abstract

A display device (500) is described with a plurality of pixels (555), each having a pixel state (P) that is driven by a driving voltage differential (V_EP) between a pixel voltage (V_px) applied to a pixel terminal (101) of the pixel and a common voltage (V_CE) applied to a common terminal (102) of the pixel. In a first pixel driving state, wherein pixels are driven to a first colour, a common voltage is provided to the common terminals (102) with a first polarity. In a second pixel driving state, wherein pixels are driven to a second colour, a common voltage is provided to the common terminals (102) with a second polarity opposite to the first polarity. An absolute value of the common voltage (V_CE) in the first and second pixel driving state is higher than a maximum absolute value of the column voltage (V_col) in the corresponding pixel driving state.

Claims

1. A display device (500) comprising:

a plurality of switches (510), each of the switches comprising an operational terminal (D) and controlling a voltage on said operational terminal (D);

a plurality of pixels (555), each having a pixel state (P) that is driven by a driving voltage differential (V_EP) between a pixel voltage (V_px) applied to a pixel terminal (101) of the pixel and a common voltage (V_CE) applied to a common terminal (102) of the pixel, said pixel terminal being coupled to a corresponding operational terminal (D) of the switch;

a common driver (570) for providing a variable common voltage (V_CE) to the common terminals (102); and

a controller (515) controlling the switches (510) for driving the plurality of pixels (555), the controller (515) being arranged to control the common driver in a first pixel driving state (1120), wherein pixels are driven to a first colour, to provide a common voltage to the common terminals with a first polarity and to control the common driver in a second pixel driving state (1140), wherein pixels are driven to a second colour, to provide a common voltage to the common terminals with a second polarity opposite to the first polarity, wherein a swing on the common voltage is larger than a swing on the pixel voltage.

2. A display device (500) according to claim 1 wherein the plurality of switches are semiconductor switching devices (510), each comprising a first operational terminal (S), a switching control terminal (G), and a second operational terminal (D);

the display device further comprising;

a column driver (530) connected to the first operational terminals (S) for providing column voltages (V_col); and

a row driver (520) connected to the switching control terminals (G) for providing a row select voltage switching the semiconductor switching devices of a row to a conductive state and a row non-select voltage switching the semiconductor switching devices of a row to a non-conductive state;

wherein

the pixel terminal of each of the pixels is coupled to the second operational terminal (D) of the corresponding semiconductor switching device and the pixel voltage (V_px) being applied to the pixel terminal (101) by providing a column voltage to the first operational terminal (S) of a corresponding semiconductor switching device being in the conductive state;

the controller (515) is arranged for controlling the operation of the column driver (530), the row driver (520), and the common driver (570) for driving the plurality of pixels (555), such that the swing on the common voltage, is larger than a swing on the column voltage, i.e. an absolute value of the difference between a maximum column voltage and a minimum column voltage, which can be provided by the column driver.

3. A display device (500) according to claim 2, wherein a swing on the row voltage, i.e. an absolute value of the difference between the row select voltage and the row non-select voltage is larger than a swing on the column voltage, i.e. an absolute value of the difference between a maximum column voltage and a minimum column voltage, which can be provided by the column driver during the first and the second driving state, in such a way that the semiconducting switching devices (510) can be switched in their conducting state and in their non-conducting state irrespective of column and pixel voltage levels.

4. A display device (500) according to claim 2, additionally comprising a storage driver for providing a storage voltage (V_st) to a storage capacitor (C_st), connected between the storage driver and the pixel terminal (101) of the pixel, having a storage voltage swing being proportional to a common voltage swing, wherein the storage driver is controlled, by the controller (515) to change the value of the storage voltage with proportional amplitude to and at substantially the same time as the common voltage.

5. A display device (500) according to claim 4, wherein the common driver (570) and the storage driver are controlled, by the controller (515) during a start up phase (1110) for an image update before the first or second pixel driving state, in a first step (1210) to change a value of the common voltage and the storage voltage so that due to the change a value of the pixel voltage is changed to a value that keeps the semiconducting switching device (510) in its non-conducting state, wherein the column driver (520) is controlled, by the controller (515) in at least one reset step (1220) to reset the value of the pixel voltage and wherein the common driver (570) and the storage driver are controlled, by the controller (515) in a second step (1230) to change the value of the common voltage and the storage voltage to the value corresponding to the first or second driving state, which ever is applicable.

6. A display device (500) according to claim 5, wherein the common driver (570) and storage driver are controlled, by the controller (515) during the start up phase, in a third step (1710) to provide a common voltage and storage voltage enabling the provision of a zero voltage over the pixels or a common voltage with a polarity opposite to the polarity of the common voltage during the remainder of the start-up phase.

7. A display device (500) according to claim 4, wherein the common driver (570) and storage driver are controlled, by the controller (515) during a transition phase (1130,1150) from the first to the second pixel driving state or vice versa, to change the value of the common voltage and the storage voltage in a number of steps (1310) from the value corresponding to the first pixel driving state to the second pixel driving state or vice versa, each of the stepwise value changes of the common voltage and storage voltage resulting in a value change of the pixel voltage, wherein the column driver (520) is controlled, by the controller (515) in at least a reset step (1320) between the steps to change the column voltage in such a way that the value of the pixel voltage is changed in a direction opposite to the direction of the value change of the pixel voltage caused by the value change of the common voltage and the storage voltage.

8. A display device (500) according to claim 4, wherein the common driver (570) and storage driver are controlled, by the controller (515) during a shutdown phase (1160) at the end of an image update after the first or second pixel driving state to change the value of the common voltage and the storage voltage in a number of steps to their final values, each of the stepwise value changes of the common voltage and storage voltage resulting in a value change of the pixel voltage, wherein the column driver (520) is controlled, by the controller (515) in at least a reset step between the steps to change the column voltage in such a way that the value of the pixel voltage is changed in a direction opposite to the direction of the value change of the pixel voltage caused by the value change of the common voltage and the storage voltage.

9. A display device (500) according to claim 8, wherein the common driver (570) and the storage driver are controlled, by the controller (515) during the shutdown phase, in a further step (1810) to provide a common voltage and storage voltage enabling the provision of a zero voltage over the pixels or to provide a common voltage with a polarity opposite to the polarity of the common voltage during the remainder of the shutdown phase.

10. A display device (500) according to claim 2 wherein the semiconductor switching device (510) is a TFT.

11. A method for driving a display device (500) comprising:

a plurality of switches (510), each of the switches comprising an operational terminal (D) and controlling the voltage on said operational terminal (D);

a plurality of pixels (555), each having a pixel state (P) that is driven by a driving voltage differential (V_EP) between a pixel voltage (V_px) applied to a pixel terminal (101) of the pixel and a common voltage (V_CE) applied to a common terminal (102) of the pixel, the pixel terminal being coupled to a corresponding operational terminal (D) of the switch;

a common driver (570) for providing a variable common voltage (V_CE) to the common terminals (102);

the method comprising;

controlling the switches for driving the plurality of pixels (555) and controlling the common driver (570) in a first pixel driving state (1120), wherein pixels are driven to a first colour, to provide a common voltage to the common terminals with a first polarity and in a second pixel driving state (1140), wherein pixels are driven to a second colour, to provide a common voltage to the common terminals with a second polarity opposite to the first polarity, wherein a swing on the common voltage, is larger than a swing on the pixel voltage.

12. A method according to claim 11, wherein the plurality of switches are semiconductor switching devices (510), each comprising a first operational terminal (S), a switching control terminal (G), and a second operational terminal (D);

the display device further comprising;

a column driver (530) connected to the first operational terminals (S) for providing column voltages (V_col); and

a row driver (520) connected to the switching control terminals (G) for providing a row select voltage switching the semiconductor switching devices of a row to a conductive state and a row non-select voltage switching the semiconductor switching devices of a row to a non-conductive state;

wherein

the pixel terminal of each of the pixels is coupled to the second operational terminal (D) of the corresponding semiconductor switching device and the pixel voltage (V_px) being applied to the pixel terminal (101) by providing a column voltage to the first operational terminal (S) of a corresponding semiconductor switching device being in the conductive state;

the method comprising the step of controlling the operation of the column driver (530), the row driver (520), and the common driver (570) for driving the plurality of pixels (555), such that the swing on the common voltage, is larger than a swing on the column voltage, i.e. an absolute value of the difference between a maximum column voltage and a minimum column voltage, which can be provided by the column driver.

13. A method according to claim 12, wherein a swing on the row voltage, i.e. an absolute value of the difference between the row select voltage and the row non-select voltage is larger than a swing on the column voltage, i.e. an absolute value of the difference between a maximum column voltage and a minimum column voltage, which can be provided by the column driver during the first and the second driving state, in such a way that the semiconducting switching devices (510) can be switched in their conducting state and in their non-conducting state irrespective of column and pixel voltage levels.

14. A method according to claim 12, comprising the further step of controlling a storage driver of the display device for providing a storage voltage (V_st) to a storage capacitor (C_st), connected between the storage driver and the pixel terminal (101) of the pixel and having a storage voltage swing (Δ

V_st) being proportional to a common voltage swing, to change the pixel voltage (V_px) with proportional amplitude to and at substantially the same time as the common voltage, with proportional amplitude to and at substantially the same time as the common voltage.

15. A method according to claim 14, further comprising controlling the common driver (570) and storage driver during a start up phase (1110) for an image update before the first or second pixel driving state, in a first step (1210) to change the common voltage and the storage value to such a value that a value of the pixel voltage is changed to a value that keeps the semiconducting switching device (510) in its non-conducting state, controlling the column driver (520) in at least one reset step (1220) to reset the value of the pixel voltage and controlling the common driver (570) and storage driver in a second step (1230) to change the value of the common voltage and the storage voltage to the value corresponding to the first or second driving state, which ever is applicable.

16. A method according to claim 15, wherein the common driver and storage driver are controlled during the start up phase, in a third step (1710), which is executed before the first step, to provide a common voltage and a storage voltage, enabling the provision of a zero voltage over the pixels or to provide a common voltage with a polarity opposite to the polarity of the common voltage during the remainder of the start-up phase.

17. A method according to claim 14, further comprising controlling the common driver (570) and the storage driver during a transition phase (1130,1150) from the first to the second pixel driving state or vice versa, to change the value of the common voltage and storage voltage in a number of steps (1310) from the value corresponding to the first pixel driving state to the second pixel driving state or vice versa, each of the stepwise value changes of the common voltage and storage voltage resulting in a value change of the pixel voltage, and controlling the column driver (520) in at least a reset step (1320) between the steps to change the column voltage in such a way that the value of the pixel voltage is changed in a direction opposite to the direction of the value change of the pixel voltage caused by the value change of the common voltage and storage voltage.

18. A method according to claim 14, further comprising controlling the common driver (570) and storage driver during a shutdown phase (1160) at the end of an image update after the first or second pixel driving state to change the absolute value of the common voltage and storage voltage in a number of steps to their final values, each of the stepwise value changes of the common voltage and storage voltage resulting in a value change of the pixel voltage, and controlling the column driver (520) in at least a reset step between the steps to change the column voltage in such a way that the value of the pixel voltage is changed in a direction opposite to the direction of the value change of the pixel voltage caused by the value change of the common voltage and storage voltage.

19. A method according to claim 18, wherein the common driver (570) and storage driver are controlled, during the shutdown phase, in a further step (1810) to provide a common voltage and a storage voltage, enabling the provision of a zero voltage over the pixels or to provide a common voltage with a polarity opposite to the polarity of the common voltage during the remainder of the shutdown phase.