Charge control of micro-electromechanical device

• US 6,829,132 B2
• Filed: 04/30/2003
• Issued: 12/07/2004
• Est. Priority Date: 04/30/2003
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Martin, Eric T., Hunter, Mark, Piehl, Arthur, Przybyla, James R., Gelhaus, Matthew, Szepesi, Jr., Leslie Louis
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): Nguyen, Dao H.
• Application Number:
  US10/428,168
• Publication Number:
  US 20040218341A1
• Time in Patent Office: 587 Days
• Field of Search: 333/174, 333/185, 333/262, 361/115, 361/277, 361/278, 361/282
• US Class Current: 361/278
• 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. A method of controlling a micro-electromechanical system (MEMS) device having a variable capacitor defining a variable gap distance, comprising:

applying a reference voltage having a selected voltage level across the MEMS device for 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 cause a stored charge having a desired magnitude to accumulate on the variable capacitor, wherein the variable gap distance is a function of magnitude of the stored charge.

2. The method of claim 1, further comprising:

removing a stored charge on the variable capacitor prior to applying the reference voltage across the micro-electromechanical device.

3. A method of controlling a MEMS actuator having a pair of plates with a gap therebetween supported by a spring mechanism having a mechanical time constant, comprising:

applying a isolatable voltage to the pair of plates to select a desired gap size by having a reference voltage applied for a duration less than the mechanical time constant then removing the reference voltage after a desired charge has been applied to the pair of plates.

4. The method of claim 3, further comprising:

removing the desired charge accumulated between the first plate and the second plate.

5. A method of controlling a MEMS actuator having a first plate and a second plate with a restoring force applied to a gap therebetween, the second plate coupled to ground, comprising:

switching a reference voltage across the first plate and ground;

accumulating a desired charge on the first plate and second plate for a duration less than a mechanical time constant of the MEMS actuator; and

decoupling the reference voltage from the first plate.

6. The method of claim 5, further comprising:

switching the first plate to ground to remove charge accumulated between the first plate and the second plate.