Charge control of micro-electromechanical device

• US 20050001828A1
• Filed: 07/28/2004
• Published: 01/06/2005
• Est. Priority Date: 04/30/2003
• Status: Abandoned Application

• Current Assignee: Arthur Piehl, Eric T. Martin, James R. Przybyla, Leslie Louis Jr. Szepesi, Mark Hunter, Matthew Gelhaus
• Original Assignee: Arthur Piehl, Eric T. Martin, James R. Przybyla, Leslie Louis Jr. Szepesi, Mark Hunter, Matthew Gelhaus
• Inventors: Piehl, Arthur, Martin, Eric T., Hunter, Mark, Gelhaus, Matthew, Przybyla, James R., Szepesi, Leslie Louis Jr.
• Application Number:
  US10/902,662
• Publication Number:
  US 20050001828A1
• Time in Patent Office: Days
• US Class Current: 345/204
• CPC Class Codes: G02B 26/001 based on interference in an adjustable optical cavity interference filters G02B5/28; devices or arrangements using multiple reflections in spectrometry or monochromators G01J3/26
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 3/3466 based on interferometric effect
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes

Abstract

A charge control circuit for controlling a micro-electromechanical system (MEMS) device having variable capacitor formed by first conductive plate and a second conductive plate separated by a variable gap distance. The charge control circuit comprises a switch circuit configured to receive a reference voltage having a selected voltage level and configured to respond to an enable signal having a duration at least as long as an electrical time constant constant of the MEMS device, but shorter than a mechanical time constant of the MEMS device, to apply the selected voltage level across the first and second plates for the duration to thereby cause a stored charge having a desired magnitude to accumulate on the variable capacitor, wherein the variable gap distance is a function of the magnitude of the stored charge.

Claims

1-12. -12. (cancelled).

13. A micro-electromechanical system comprising:

an M-row by N-column array of a micro-electromechanical cells, wherein each cell comprises;

a micro-electromechanical system (MEMS) device having a variable capacitor formed by a movable first conductive plate and a fixed second conductive plate separated by a variable gap distance; and

a switch circuit configured to receive a reference voltage having a selected voltage level and configured to respond to an enable signal having a duration at least as long as an electrical time constant of the MEMS device, but shorter than a mechanical time constant of the MEMS device, to apply the selected voltage level across the first and second plates for the duration to thereby cause a stored charge having a desired magnitude to accumulate on the variable capacitor, wherein the variable gap distance is a function of the magnitude of the stored charge.

14. The micro-electromechanical system of claim 13, wherein each of the M rows receives a separate enable signal and all N switch circuits of a given row receive a same enable signal.

15. The micro-electromechanical system of claim 13, wherein each of the N columns receives a separate reference voltage and all M switch circuits of a given column receive a same reference voltage, wherein each separate reference voltage can have a different selected voltage level.

16. The micro-electromechanical system of claim 13, wherein each switch circuit comprises:

a first switch coupled to the micro-electromechanical device and configured to provide the reference voltage to the micro-electromechanical device for the duration of, and in response to, the enable signal.

17. The micro-electromechanical system of claim 16, wherein the first switch comprises:

a p-channel metal-oxide-semiconductor (PMOS) device having a source configured to receive the reference voltage, a gate configured to receive the enable signal, and a drain configured to provide the reference voltage to the micro-electromechanical device based on the enable signal.

18. The micro-electromechanical system of claim 13, further comprising:

a variable power supply configured to provide the reference voltages to the N columns of the array; and

a controller configured to provide the enable signals to the M rows of the array and to control the selected voltage level of the reference voltages provided by the variable power supply to the N columns of the array.

19. The micro-electromechanical system of claim 13, wherein each switch circuit is further configured to discharge a stored charge on the variable capacitor in response to a clear signal.

20. The micro-electromechanical system of claim 19, wherein each of the M rows receives a separate clear signal and all N switch circuits of a given row receive a same clear signal.

21. The micro-electromechanical system of claim 19, wherein each switch circuit further comprises:

a second switch coupled across the first and second conductive plates and configured to discharge the stored charge from the variable capacitor in response to a clear signal.

22. The micro-electromechanical system of claim 21, wherein the second switch comprises:

an n-channel metal-oxide-semiconductor (NMOS) device having a gate configured to receive the clear signal and a drain and source coupled across the first and second conductive plates.

23. The micro-electromechanical system of claim 19, further comprising:

a variable power supply configured to provide the reference voltages to the N columns of the array; and

a controller configured to provide the enable signals and the clear signal to the M rows of the array and to control the selected voltage level of the reference voltages provided by the variable power supply to the N columns of the array.

24-32. -32. (Cancelled).

33. A micro-electromechanical system comprising:

an M-row by N-column array of a micro-electromechanical cells, wherein each cell comprises;

a micro-electromechanical system (MEMS) device having a variable capacitor formed by a movable first conductive plate and a fixed second conductive plate separated by a restoring force providing a variable gap distance; and

a circuit configured to receive a reference voltage having a selected voltage level and configured to apply the reference voltage for a duration shorter than a mechanical time constant of the MEMS device to thereby cause a desired charge to accumulate on the variable capacitor before the reference voltage is removed, wherein the variable gap distance is a function of the magnitude of the stored charge.

34. The micro-electromechanical system of claim 33, wherein each of the M rows receives a separate enable signal to apply the reference voltage and all N switch circuits of a given row receive a same enable signal.

35. The micro-electromechanical system of claim 33, wherein each of the N columns receives a separate reference voltage and all M switch circuits of a given column receive a same reference voltage, wherein each separate reference voltage can have a different selected voltage level.

36. The micro-electromechanical system of claim 33, wherein each circuit comprises:

a first switch coupled to the micro-electromechanical device and configured to provide the reference voltage to the micro-electromechanical device for the duration of, and in response to, an enable signal.

37. The micro-electromechanical system of claim 36, wherein the first switch comprises:

a p-channel metal-oxide-semiconductor (PMOS) device having a source configured to receive the reference voltage, a gate configured to receive the enable signal, and a drain configured to provide the reference voltage to the micro-electromechanical device based on the enable signal.

38. The micro-electromechanical system of claim 33, further comprising:

a variable power supply configured to provide the reference voltages to the N columns of the array; and

a controller configured to provide a set of enable signals to the M rows of the array and to control the selected voltage level of the reference voltages provided by the variable power supply to the N columns of the array.

39. The micro-electromechanical system of claim 33, wherein each circuit is further configured to discharge a stored charge on the variable capacitor in response to a clear signal.

40. The micro-electromechanical system of claim 39, wherein each of the M rows receives a separate clear signal and all N switch circuits of a given row receive a same clear signal.

41. The micro-electromechanical system of claim 39, wherein each circuit further comprises:

a switch coupled across the first and second conductive plates and configured to discharge the stored charge from the variable capacitor in response to a clear signal.

42. The micro-electromechanical system of claim 41, wherein the switch comprises:

an n-channel metal-oxide-semiconductor (NMOS) device having a gate configured to receive the clear signal and a drain and source coupled across the first and second conductive plates.

43. The micro-electromechanical system of claim 39, further comprising:

a variable power supply configured to provide the reference voltages to the N columns of the array; and

a controller configured to provide a set of enable signals and the clear signal to the M rows of the array and to control the selected voltage level of the reference voltages provided by the variable power supply to the N columns of the array.