Power supply apparatus capable of multi-mode operation for an electrophoretic display panel

• US 4,947,159 A
• Filed: 04/18/1988
• Issued: 08/07/1990
• Est. Priority Date: 04/18/1988
• Status: Expired due to Fees

• Current Assignee: AU Optronics Corporation
• Original Assignee: 501 Copytele Incorporated
• Inventors: Krusos, Denis A., Di Santo, Frank J.
• Primary Examiner(s): Oberley, Alvin
• Application Number:
  US07/182,436
• Time in Patent Office: 841 Days
• Field of Search: 340/787, 340/788, 340/805, 350/362
• US Class Current: 345/107
• CPC Class Codes: G09G 2300/06 Passive matrix structure, i.e. with direct application of both column and row voltages to the light emitting or modulating elements, other than LCD or OLED
• CPC Class Codes: G09G 2310/061 for resetting or blanking
• CPC Class Codes: G09G 2310/068 Application of pulses of alternating polarity prior to the drive pulse in electrophoretic displays
• CPC Class Codes: G09G 2330/02 Details of power systems and of start or stop of display operation
• CPC Class Codes: G09G 3/3446 with more than two electrodes controlling the modulating element

Abstract

There is disclosed a multi-mode power supply for biasing an electrophoretic display and particularly for biasing the anode electrode of such a display. The supply contains first and second supply means each of which can operate as a constant voltage or constant current supply. The first and second supplies are respectively coupled to the anode electrode of the electrophoretic display so that during the Write Mode the display is operated with a constant current at a first polarity and operates with a constant current at a second polarity during the Erase Mode. Additional modes are shown where AC voltages are applied to the anode electrode either directly as in the case of a Slow Erase Mode or via a capacitor in the case of a Time 60 Cycle Mode for a given time period. In these modes the supplies are operated as constant voltage sources to enable suitable magnitude voltages to be applied to the anode electrode in order to provide optimum operating conditions for the electrophoretic display.

Claims

1. In an electrophoretic display of the type having an anode electrode associated with an X-Y matrix manifesting grid and cathode electrodes to provide a display by causing pigment particles to be transported to said anode electrode during a Write Mode according to drive signals applied between said grid and cathode electrodes, the improvement therewith comprising:

constant current source means coupled to said anode electrode to provide a constant current to said anode electrode during said Write Mode and of a given polarity necessary to transport said particles to said anode electrode.

2. The electrophoretic display according to claim 1, wherein said constant current source means being coupled to said anode electrode and operative to provide a constant current to said anode electrode of an opposite polarity sufficient to direct said particles away from said anode electrode, indicative of an Erase Mode.

3. The electrophoretic display according to claim 2, further including controllable switching means coupled to said anode electrode and capable of operating in a first mode wherein said constant current of said given polarity is applied to said anode electrode indicative of said Write Mode and operative in a second mode where said constant current of said opposite polarity is applied to said anode electrode indicative of said Erase Mode.

4. The electrophoretic display apparatus according to claim 3, wherein said constant current source means a first constant current source for providing constant current at given polarity at an output with said output coupled to said switching means, and

a second constant current source for providing constant current at said opposite polarity and coupled to said switching means and,

means for operating said switching means in said first and second modes wherein said first mode said current source of said given polarity is coupled to said anode electrode and wherein said second mode and current source of said opposite polarity is coupled to said anode electrode.

5. A power supply apparatus for biasing the anode electrode of an electrophoretic display panel, said electrophoretic display having an X-Y grid manifesting cathode and grid electrodes which when driven and biased enable pigment particles to be transported and packed on the anode electrode according to drive signals applied between said grid and cathode electrodes during a Write Mode when said anode electrode is biased at a first polarity and to remove said particles as packed on said anode electrode during an Erase Mode where said anode is biased at a second polarity, said power supply comprising:

switching means having an output terminal coupled to said anode electrode and operative in a first mode where said output terminal is connected to a first input terminal and in a second mode where said output terminal is coupled to a second input terminal,

a first power supply means having an output coupled to said first input terminal of said switching means for providing a first polarity biasing signal for said anode electrode when said switching means is operated in said first mode,

a second supply means having an output coupled to said second input terminal and operative to provide a second polarity biasing signal when said switching means is operated in said second mode,

with each of said first and second supply means including separate means for monitoring the current through said anode electrode with respect to a reference level to maintain a constant output current according to said monitored current when said first or second supply means is connected to said anode electrode by said switching means, whereby when said first supply means is connected to said first input terminal said associated means for monitoring is operative to maintain a constant current from said first supply means and when said second supply means is connected to said second input terminal said associated means for monitoring is operative to maintain a constant current from said second supply means.

6. A power supply apparatus for applying operating potential to the anode electrode of an electrophoretic display panel, comprising:

a first supply means capable of being selectively operated as a constant current supply in a first mode and a constant voltage supply in a second mode, switching means coupling said anode electrode to said first supply means during a Write Mode and means for selecting said first supply means to operate as a constant current supply during said Write Mode.

7. The power supply apparatus according to claim 6, further including:

a second supply means capable of being selectively operated as a constant current supply in a first mode and a constant voltage supply in a second mode,

said switching means coupling said anode electrode to said second supply means during an Erase Mode and means for selecting said second supply means to operate as a constant current supply during said Erase Mode.

8. The power supply apparatus according to claim 7, further including means coupled to said switching means for operating said switching means at a given rate,

means coupled to said first and second supply means for operating said supplies as constant voltage supplies whereby the voltage outputs of said first and second supply means are respectively applied to said anode electrode at said given rate to provide a Slow Erase Mode for said panel.

9. The power supply apparatus according to claim 8, wherein said given rate is between 1 to 3 HZ.

10. The power supply apparatus according to claim 9 further including means coupled to said switching means for selectively AC coupling said switching means to said anode electrode,

means coupled to said switching means for operating said switching means at another given rate,

with said selector means operative to cause said first and second supply means to operate as constant voltage supply means whereby said first and second supply means are respectively applied to said anode electrode via a to provide an AC coupled signal to said anode electrode when said anode electrode is AC coupled to said first and second supply means.

11. The power supply apparatus according to claim 10 wherein said another given switching rate is approximately 60 HZ.

12. In an electrophoretic display panel of the class having an anode display electrode, at least one cathode electrode located apart from said anode electrode and directed in a given plane and at least one grid electrode insulated from said cathode electrode and positioned transverse thereto with the space between said anode, grid and cathode electrodes filled with charged pigment particles suspended in a dye solvent wherein said particles can be transported to said anode electrode according to driving potentials applied between said grid and cathode electrodes indicative of a desired pattern during a Write Mode where said anode electrode is biased at a first polarity operating level and where said particles are removed from said anode electrode during an Erase Mode where said anode electrode is biased at a second polarity operating level, the combination therewith of power supply apparatus for biasing said anode electrode during said Write and Erase Modes comprising:

constant current source means coupled to said anode electrode for providing said first polarity operating level at a constant current during said Write Mode whereby said anode current is maintained relatively constant during said Write Mode and,

said constant current source means being responsive to said display being operated in said Erase Mode to provide said second polarity operating level to said anode electrode at a constant current during said Erase Mode.

13. The apparatus according to claim 12, wherein said means responsive to said display being operated in said Erase Mode includes switching means coupled to said anode and wherein said constant current source means includes a first current source applied to said anode during a first mode of said switching means indicative of said Write Mode and a second current source applied to said anode during a second mode of said switching means indicative of said Erase Mode.

14. The apparatus according to claim 12, further including means for selectively AC coupling said anode electrode to first and second voltage sources via common switching means and for operating said switching means at a given rate to selectively apply said first and second voltages to said anode electrode at said given rate.

15. The apparatus according to claim 14, including means coupled to said switching means for selectively operating said switching means at a lower given rate and including means coupled to said first and second current sources to operate said first and second current sources as first and second voltage sources to enable voltage outputs of said first and second voltage sources to be applied directly to said anode electrode at said lower given rate.

16. The apparatus according to claim 15, wherein said lower given rate is between 1-3 HZ per second.

17. The apparatus according to claim 14, wherein said given rate is approximately 60 HZ.