Apparatus for driving actuator

Information

  • Patent Application
  • 20080012449
  • Publication Number
    20080012449
  • Date Filed
    March 13, 2007
    18 years ago
  • Date Published
    January 17, 2008
    17 years ago
Abstract
An apparatus for driving an actuator includes a power unit, a sensing unit, and a first outer capacitor. The power unit provides first and second power in mutually reverse phases to first and second activating vibration plate, respectively. The sensing unit senses a displacement of a suspended vibration plate according to a result of sensing by a sensing plate. The first outer capacitor is disposed between a first power terminal connecting the power unit to the actuator and a sensing terminal connecting the sensing plate to the sensing unit.
Description

BRIEF DESCRIPTION OF THE DRAWINGS


FIG. 1 is a graph illustrating an example of a signal-to-noise ratio of a related art apparatus for driving an actuator.



FIG. 2 is a block diagram illustrating an apparatus for driving an actuator according to an exemplary embodiment of the present invention.



FIG. 3 is a diagram illustrating an actuator and a power unit according to an exemplary embodiment of the present invention.



FIG. 4 is a graph comparing an improved signal-to-noise ratio of the apparatus illustrated in FIG. 2 with the related art.





DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

An apparatus for driving an actuator according to an exemplary embodiment of the present invention will now be described more fully with reference to the accompanying drawings.



FIG. 2 is a block diagram illustrating an apparatus for driving an actuator according to an exemplary embodiment of the present invention. The apparatus includes a power unit 100, an actuator 120 and a sensing unit 140.


As illustrated in FIG. 3, the actuator 120 includes a first activating vibration plate 121, a second activating vibration plate 122, a suspended vibration plate 123 and a sensing plate 124. The actuator 120 includes a general electrostatic actuator such as a comb type micro actuator or a conventional parallel plate type micro actuator.


A first power capacitor C1 in the actuator 120 in FIG. 2 represents changes in the capacitance between the first activating vibration plate 121 and the suspended vibration plate 123 due to vibration of the plates, and a second power capacitor C2 represents changes in the capacitance between the second activating vibration plate 122 and the suspended vibration plate 123 due to vibration of the plates. Also, a sense capacitor C3 represents changes in the capacitance between the sensing plate 124 and the suspended vibration plate 123 due to vibration of plates.


The power unit 100 illustrated in FIG. 3 provides power to the actuator 120, and has an inverter 101. The power unit 100 directly provides a first power to the first activating vibration plate 121 of the actuator 120 and provides a second power, which is in a reverse phase compared to the first power provided to the first activating vibration plate 121 to the second activating vibration plate 122 of the actuator 120 via the inverter 101.


The sensing unit 140 senses a displacement of the suspended vibration plate 123 according to a result of sensing by the sensing plate 124.


The power provided to the first activating vibration plate 121 and that provided to the second activating vibration plate 122 are in reverse phases to each other so that an electrostatic force is generated at the first activating vibration plate 121 and the second activating vibration plate 122 respectively. Here, an AC considered as noise is transmitted to the sensing unit 140 by a parasitic capacitance in the actuator 120. Since the noise is also reversed in phase, it is offset and the signal-to-noise ratio is improved. However, in order to maximize the effect of the noise offset, the difference between a first parasitic capacitance formed by the first activating vibration plate 121, the suspended vibration plate 123, and the sensing plate 124 and a second parasitic capacitance formed by the second activating vibration plate 122, the suspended vibration plate 123, and the sensing plate 124 should be minimized. In order to gain the effect of the noise offset, a first outer capacitor Ce1 and a second outer capacitor Ce2 may be provided since the first parasitic capacitance and the second parasitic capacitance do not generally coincide.


The first outer capacitor Ce1 is provided between a first power terminal T1, which connects the power unit 100 to the actuator 120 in order to provide the first power, and a sensing terminal T3, which connects the sensing plate 124 of the actuator 120 to the sensing unit 140.


The second outer capacitor Ce1 is provided between a second power terminal T2, which provides the second power and connects the power unit 100 to the actuator 120, and the sensing terminal T3.


In order to minimize the noise made by the difference between the first parasitic capacitance and the second parasitic capacitance in the actuator 120, capacitance of one or both of the first outer capacitor (Ce1) and the second outer capacitor (Ce2) is adjusted so that the first parasitic capacitance and the second parasitic capacitance are similar. The adjustment may be done by means of a repeated test according to a result of sensing by the sensing unit 140 during the designing stage of the apparatus for driving the actuator 120.



FIG. 4 is a graph comparing an improved signal-to-noise ratio of the apparatus illustrated in FIG. 2 with the related art.


{circle around (1)} in FIG. 4 illustrates a result of the signal-to-noise ratio according to the related art. When power in a reverse phase is provided to two activating vibration plates, respectively, the signal-to-noise ratio (SNR=0.42 dB) is small because of the difference between a first parasitic capacitance and a second parasitic capacitance.


{circle around (2)} in FIG. 4 illustrates a result of the signal-to-noise ratio according to an exemplary embodiment of the present invention. When power in a reverse phase is provided to two activating vibration plates, respectively, the signal-to-noise ratio (SNR=12.2 dB) is large because the difference between a first parasitic capacitance and a second parasitic capacitance is minimized by a first outer capacitor Ce1 and a second outer capacitor Ce2. The fact that the signal-to-noise ratio is large signifies excellent detection ability.


The apparatus for driving the actuator 120 is provided so that an apparatus may form an image by using a device such as a printer or a scanner.


The apparatus for driving the actuator 120 according to the present invention, improves the signal-to-noise ratio by adding the outer capacitor that allows the parasitic capacitances to be similar to each other in order prevent an activating vibration signal mixing with a sensing signal, which generates noise through parasitic capacitance caused by the construction of the actuator 120 and vibration characteristics. Also, since the sensing unit 140 is embodied by using a simple capacitance detecting type circuit the cost of manufacturing the driving apparatus can be reduced.


While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.

Claims
  • 1. An apparatus for driving an actuator which comprises a first activating vibration plate, a second activating vibration plate separated from the first activating vibration plate, a suspended vibration plate, and a sensing plate, the apparatus comprising: a power unit which provides first and second power in mutually reverse phases to the first and second activating vibration plates, respectively;a sensing unit which senses a displacement of the suspended vibration plate according to a result of sensing by the sensing plate; anda first outer capacitor which is disposed between a first power terminal which connects the power unit to the actuator to provide the first power, and a sensing terminal which connects the sensing plate to the sensing unit.
  • 2. The device of claim 1, further comprising a second outer capacitor disposed between a second power terminal which connects the power unit to the actuator to provide the second power, and the sensing terminal.
  • 3. The device of claim 1, wherein the power unit comprises an inverter, provides the first power directly to the first activating vibration plate and provides the second power in a reverse phase with respect to the first power, to the second activating vibration plate via the inverter.
  • 4. The device of claim 1, wherein the actuator is one of a comb type micro actuator and a parallel plate type micro actuator.
  • 5. The device of claim 2, wherein a capacitance of the first outer capacitor and a capacitance of the second outer capacitor are adjusted to offset a noise caused by a parasitic capacitance in the actuator.
  • 6. An image forming apparatus comprising an apparatus for driving an actuator which comprises a first activating vibration plate, a second activating vibration plate separated from the first activating vibration plate, a suspended vibration plate, and a sensing plate, the apparatus for driving an actuator comprising: a power unit which provides first and second power in mutually reverse phases to the first and second activating vibration plates, respectively;a sensing unit which senses a displacement of the suspended vibration plate according to a result of sensing by the sensing plate; anda first outer capacitor which is disposed between a first power terminal which connects the power unit to the actuator to provide the first power, and a sensing terminal which connects the sensing plate to the sensing unit.
  • 7. The image forming apparatus of claim 6, further comprising a second outer capacitor disposed between a second power terminal which connects the power unit to the actuator to provide the second power, and the sensing terminal.
  • 8. The image forming apparatus of claim 6, wherein the power unit comprises an inverter, provides the first power directly to the first activating vibration plate and provides the second power in a reverse phase with respect to the first power, to the second activating vibration plate via the inverter.
  • 9. The image forming apparatus of claim 6, wherein the actuator is one of a comb type micro actuator and a parallel plate type micro actuator.
  • 10. The image forming apparatus of claim 7, wherein a capacitance of the first outer capacitor and a capacitance of the second outer capacitor are adjusted to offset a noise caused by a parasitic capacitance in the actuator.
Priority Claims (1)
Number Date Country Kind
10-2006-0065074 Jul 2006 KR national