TW200525851A - A system and a method of driving a parallel-plate variable micro-electromechanical capacitor - Google Patents

Abstract

A method of driving a parallel-plate variable micro-electromechanical capacitor (110-2, 130, 130-1) includes establishing a first charge differential across first and second conductive plates (135, 135-1, 140) of a variable capacitor(110-2, 130, 130-1) in which the first and second conductive plates (135, 135-1, 140) are separated by a variable gap distance (145, 145-1), isolating the first and second plates for a first duration, decreasing the charge differential to a second charge differential which is less than the first charge differential and in which the second charge differential corresponds to a second value of the variable gap distance (145, 145-1).

Description

200525851 IX. Description of the invention: The technical field to which the invention belongs] This application is a part of US Patent Application No. 10 / 437,522, filed on April 30, 2003, "Micro-Electro-Mechanical Device Charge Control Technology". The case, the entire content of the case is for reference. The present invention relates to a system and method for driving variable microelectromechanical capacitors in parallel plates. BACKGROUND OF THE INVENTION 10 Micro-Electro-Mechanical Systems (MEMS) is a system 'developed using thin-film technology and includes electrical and micro-mechanical components. MEMS devices are used in various applications' such as: optical display systems, pressure sensors, flow sensors, and charge control actuators. MEMS devices use electrostatic forces or energy to move or monitor micromechanical components. In a form 15 of the micro-electromechanical device, in order to achieve the desired result, the gap distance between the electrodes is controlled by balancing the electrostatic force and the mechanical return force '. Typically, digital MEMS devices use two discrete gap distances, while analog MEMS devices use variable gap distances. Such MEMS devices have been developed using various methods. In one method 20, a deformable flexible diaphragm is placed on an electrode and electrostatically attracted to the electrode. Other methods use silicon or aluminum flaps or beams to form the top conductive layer. For optical applications, the conductive layer is reflective, and the flexible diaphragm is deformed, using electrostatic forces to guide light incident on the conductive layer. One method for controlling the gap distance between electrodes is to apply a continuous control voltage to the electrodes, in which the control voltage is increased to decrease the gap distance, or the control voltage is decreased to increase the gap distance. However, this method suffers from electrostatic instability, which greatly reduces the usable operating range that can effectively control the gap distance. In addition, the rate of change of the gap distance is mainly determined by the physical characteristics of the batch-capturing device. When the voltage changes, as the MEMS device stabilizes in its final position, the change in the gap distance between these electrodes lags behind the change in voltage. [Summary of the Invention] SUMMARY OF THE INVENTION The method for driving a flat plate variable microelectromechanical capacitor includes: establishing a first charging difference across the first and second conductive plates of the variable capacitor, wherein the first and second conductive plates are The variable gap distance is separated, isolating the first and second conductive plates for a first period of time, and then reducing the charging difference to a second charging difference that is less than the first charging difference, and wherein the second charging difference corresponds to the first of the variable gap distance. Binary. 15 Brief Description of the Drawings These drawings illustrate various embodiments of the device and method of the present invention and are part of the brother's book. The embodiments described above are merely examples of the apparatus and method of the present invention 'but do not limit the scope of the apparatus and method of the present invention. 20 FIG. 1 is a simple block diagram illustrating a micro-electromechanical (MEMS) device according to an exemplary embodiment of the present invention; FIG. 2 is a cross-sectional view illustrating a micro-electromechanical device according to an exemplary embodiment of the present invention; FIG. 3A FIG. 3B is a schematic diagram illustrating a micro-electromechanical device when a charging difference is removed from a variable capacitor according to an exemplary embodiment of the present invention; FIG. 3B is a schematic diagram illustrating an operation period before charging according to the exemplary embodiment of the present invention. MEMS device; FIG. 3C is a schematic diagram illustrating a MEMS device during a 5 charge pulse operation according to an exemplary embodiment of the present invention; FIG. 3D is a schematic diagram illustrating a typical MEMS device during a steady operation Figure 3E is a schematic diagram illustrating a typical micro-electromechanical device during a charge removal operation; and Figure 4 is a block diagram illustrating a typical MEMS device having a plurality of MEMS cells in an MXN array. I: Detailed description of the preferred embodiment 3 The method for driving a flat plate variable microelectromechanical capacitor includes: establishing a first charging difference across 15 first and second conductive plates of the variable capacitor, wherein the first and The second conductive plate is separated by a variable gap distance to isolate the first and second conductive plates for a first time period, and then reduces the charging difference to a second charging difference that is less than the first charging difference, and wherein the first charging difference corresponds to The second value of the variable gap distance. 20 As used herein and in the scope of the accompanying application, the meaning of this “electric crystal” and “switch” can be broadly understood as any device or structure that can be selectively activated in response to a signal. In the following description, various details are listed for the purpose of explanation to provide a thorough understanding of the method and apparatus of the present invention. However, it will be apparent to those skilled in the art 200525851 that such details may not be required to implement the method and apparatus of the present invention. The meaning of "one embodiment" or "an embodiment" in the specification means that the special features, structures, or characteristics described in this embodiment are included in at least one embodiment. In this embodiment, The phrase "an embodiment" appearing in 5 places in the description does not necessarily refer to the same embodiment. Code structure Figure 1 is a block diagram illustrating a typical embodiment of a micro-electromechanical system (MEMS) (100) The MEMS (IOO) includes: a charging control circuit (105) and a micro-electromechanical device (device) (11). The charging control circuit (105) further includes a variable power source (115), a controller (120), And a switching circuit (125). The MEM device (11) further includes a variable capacitor (130), which includes a first conductive plate (135) and a second conductive plate (130) separated by a variable gap distance (145). 140). The charge control circuit (105) is designed to supply the selected voltage to the variable capacitor 15 (130), and the voltage level is: compared to charging the variable capacitor (丨 30) to the second or last Value must be higher. This process can be referred to as accelerating this voltage It assists in moving the first and second conductive plates (135, 14) to their last mechanical position faster, as will be discussed in more detail below. According to a typical embodiment, this variable power source (115) is variable The voltage source 20 is designed to receive a voltage selection signal from the controller (120) via the path (150). This power source (115) provides the selected voltage to the switching circuit (125) via the path (155) according to the voltage selection signal. ). The variable gap distance (145) between the separated first conductive plate (135) and the second conductive plate (14) is a function of the amount of charge 200525851 stored on the variable capacitor ⑽. In order to adapt to the first The relative movement between the conductive plate (135) and the second conductive plate (14) allows one conductive plate to be fixed while the other conductive plate is movable. For ease of explanation, 'the second conductive plate can be made according to this exemplary embodiment. The plate (140) is considered to be a fixed plate. This variable gap distance (145) can be maximized by placing the first and second conductive plates (135, 14) 5 in the same initial electromechanical state. This initial state Is the minimum, or the charge on these boards It can be established by connecting each of the first and second boards (135, 140) to the respective voltages, as will be discussed in detail below. It is possible to charge the control circuit (105) by simply The selection voltage provided by the variable power source (115) between the second conducting board (135, 140) is applied for a preset period, so that a desired amount of stored charge is accumulated on the variable capacitor (13). As previously discussed, this charge stored on the variable capacitor (13) corresponds to the electrostatic attraction between the first and second conductive plates (135, 14). Therefore, this is on the variable capacitor (130) The greater the amount of stored charge, the greater the electrostatic attraction between the first and second conductive plates (135, 140). In addition, the design switching circuit (125) receives the enable signal for a preset period via the path (160). In response to this enable signal, the selected voltage level is applied to the MEMS device (11) via the path (165) during a preset time, so 20 is made to accumulate the desired amount on the variable capacitor (13). Store charge. In a typical embodiment, the switching circuit (125) is designed to receive a clear signal from the controller (120) via the path (170), and in response to the clear signal, the potential stored on the variable capacitor (130) Stored charge removed. After removing the stored charge, the variable capacitor (130) is brought to a known charge level before applying the reference voltage of 200525851 having the selected voltage level. This initially selected voltage applied to the variable capacitor (130) can provide more charge to the MEMS device (110) than the charge associated with the last desired gap. In other words, the selected applied voltage on the variable capacitor (130) 5 may cause a larger amount of initially accumulated charge, which is greater than the desired final charge value, and therefore greater than the corresponding final variable value. Clearance distance (145). The charge stored in the variable capacitor (130) is in response to a charging signal from the controller (120) to the switching circuit (125) via the charge control path (175). This variable capacitor can be moved to its last mechanical position more quickly by: 10 increasing the voltage level initially applied to the variable capacitor (130) and subsequently removing a preselected amount of charge. According to a typical embodiment, a selected amount of charge is removed from the first and second plates (135, 140) in response to a charge adjustment signal that is then used to clear the signal via the same path (170). As previously discussed, this reference voltage applied to the first 15 and second plates (135, 140) corresponds to: a relatively large amount of charge is initially stored on the first and second plates (135, 140), which corresponds to The last gap value. This charge adjustment signal causes removal of a preselected amount of charge from the first and second plates (135, 14). When this variable capacitor (130) has a relatively large amount of charge stored on it, it moves toward each other faster than if it were charged with only the last charge value. When this variable gap distance (145) approaches the desired final value, the pre-selected amount of charge is removed. The first and second plates (135, 140) are then allowed to mechanically stabilize at a variable final gap distance (145). As an alternative to using the clean-up signal to remove the selected amount of charge 10 200525851, the selected amount of charge can be removed by adjusting Vref to the acceleration drive compensation voltage, after which the enable and charge enable signals can be applied. In these cases, Vref is used to charge the variable capacitor with an accelerated drive charge and to remove the selected amount of charge. 5 Typical implementation of public works Figure 2 is a diagram illustrating the typical embodiment of a MEMS device (110- 丨). In a typical embodiment, the MEMS device (110-1) at least partially displays: pixels that can display an image. The MEMS device (110-1) includes: a top reflector (200), a bottom reflector (210), a Sex piece (220), and impeachment mechanism 10 (230). The resonant optical cavity (240) is defined by reflectors (200, 210). The two reflectors (200, 210) are separated by a variable gap distance (145-1). This top reflector (200) may be translucent or semi-reflective and may be used in conjunction with the bottom reflector (210) ' It may be south-reflective or total-reflective, or vice versa. The elastic yellow mechanism (230) can be made of any suitable flexible material such as polymer, which has linear and non-linear spring functions. The optical cavity (240) can be adjusted using optical interference to select a visible light wavelength of a particular intensity. Depending on the structure of the MEMS device (110-1), the optical cavity (240) reflects or transmits wavelengths at a desired intensity. This means that the nature of the optical cavity (240) can be reflective or transmissive. According to 20 examples of this typical implementation, the optical cavity (240) does not generate light. Instead, this MEMS device (iio-i) relies on ambient light or external light sources (not shown). The optical cavity (240) can transmit visible wavelengths, and its intensity depends on the gap distance (145-1) between the top and bottom reflectors (200, 210). Therefore, the optical cavity (240) can be adjusted to the desired wavelength of 200525851 by controlling the gap distance (145-1). When an appropriate amount of charge is stored on the reflectors (200, 21), the flexible member (220) and the spring mechanism (230) allow to change the gap distance 0454). So that the desired wavelength can be selected at the desired intensity. This final charge and its corresponding voltage are determined according to the following formula, which provides an attractive force between the reflectors (200, 210). Therefore, the parallel plate capacitor formed by the reflector (200, 21) and the variable gap distance (145-1) does not consider the fringe electric field.

Formula I

2d2 ε〇 is the dielectric constant of free space. , V is the voltage across the reflectors (200, 21), A is the area of each reflector (200, 210), and 4 is the instantaneous gap distance (145-1). Therefore, with a gap distance (145-1) of 0.25 micron Q0-6m), this one volt voltage across 70 square micron pixels can generate an electrostatic force of 7x10-? Newton (N).

Therefore, the amount of charge corresponding to the small voltage between the reflectors (200, 210) provides enough power to move the top reflector (200) and keep it against gravity and other things such as body vibration force. This electrostatic charge stored in the reflectors (200, 210) is sufficient to keep the top reflector (200) in place without the need for additional power. The electrostatic force defined in Equation 1 is balanced with the linear elastic force provided by the spring mechanism (23). The characteristic of this spring force is determined by the second formula. Formula II: F = k (d〇-d) 12 200525851 where k is the linear elastic constant of the spring mechanism (230), dO is the initial value of the gap distance (145-1), and d is the instantaneous gap distance (145-1 ). As previously discussed, this range is where the force produced by Equation 1 and the force produced by Equation 2 are in a stable equilibrium state, and is used when the value of (d0-d) is between 0 and 5 c1d / 3 Generated by voltage control. When (d.-d) is greater than do / 3, the electrostatic force of Formula 1 exceeds the spring force of Formula 2, so that the reflectors (200, 210) are suddenly joined together. This occurs because when the variable gap distance is less than do0 / 3, the excess charge is attracted to the reflector (200, 210) due to the increased capacitance, which in turn causes the reflector (200, 210) according to Equation 1 The increase in attraction between the two causes the two reflectors to be attracted together. However, the attraction between the reflectors (200, 210) of this formula 1 can instead be written as a function of the charge according to formula 3.

Formula III 2εΑ 15 where Q is the charge on the capacitor. F is a function of the charge Q instead of d. It can be seen that the entire gap, for example, from almost 0 to d0, can be controlled by controlling the amount of charge on the reflector (200, 21) instead of voltage. While controlling the variable gap distance (145-1). In addition, the MEM device (110-1) has a mechanical time constant, which causes a delay in the movement of the reflector (200) due to a change in the charge Q on the variable capacitor. This mechanical time constant can be controlled, among other things, by the materials used in the bomb mechanism (230) and the operating environment of the MEMS device (110-1). For example, the mechanical time constant of the MEM device (110-1) is one value when it is operated in air and the other value is when it is operated in a helium environment. This charging control circuit (105) uses each of the above features to control the gap distance (145-1) over substantially the entire gap range. By applying a selectable control voltage to the MEM device according to the time period of the enable signal 5 and the period is less than the mechanical time constant of the MEM device (110-1), the variable capacitance of the MEM device (11 (M) , It seems to be “fixed” during the time of applying the reference voltage. Therefore, it can be determined by the fourth formula: this is what is generated on the reflector (200, 21) due to the application of the selected reference voltage 1〇 the required accumulated charge Q. Formula IV:

Q = CintVrEF where VREF is the selected reference voltage and Cint is the initial capacitance of the mem device (110-1). 15 Therefore, applying a relatively high reference voltage to the top and bottom reflectors (200, 210) causes a large initial charging difference. The large charging difference originally established between the top and bottom reflective Is (200, 210) results in a larger suction bow force between the top and bottom reflectors (200, 210). This larger attractive force causes the top and bottom 20 reflectors (200, 21) to move toward each other correspondingly as the value of the variable gap distance (145-1) decreases. When this variable gap distance (145-1) approaches its desired or desired value, a pre-selected or final charge is established between ^ and the bottom reflector (200, 210). Once the final charging value is established on the top and bottom reflectors (200, 210), the 1MEM device (1HM) is floating or three-state, so preventing the charging state from fluctuating greatly from 14 200525851, and further enabling effective control of the gap distance The direct voltage control of the bean relative to the MEM device ⑴Ο-D is an increased control range. Due to the increased charging difference between the reflectors (200, 210), these reflectors (200, 210) can be moved to their final positions, and the period of time for this movement 5 is substantially less than: Time required for the MEM device (110-1) to mechanically stabilize after the initial reference voltage. Although the above paragraphs are explained in the context of an ideal parallel plate capacitor and an ideal linear elastic recovery force, those skilled in the art understand that the principles described can be applied to other MEM devices, including but not limited. Yu: Display devices based on interference or diffraction, parallel plate actuators, non-linear springs, and other forms of capacitors. Figures 3A to 3E are schematic diagrams of the MEMS (100-1), which allows the first and second plates of the variable capacitor (130-1) to be moved faster, 14o_υ. This net plate (135-1, 140-1) is charged between the first and second plates (315-1, 140-1) by 15 voltages applied to the variable capacitor (130-1). The difference drives faster and moves to its final position faster. FIG. 3A is a schematic diagram of the MEMS (100-1) in the initial state. The MEMS includes a clearing transistor (300), a first or enabling transistor (310), a first and a second clearing node (320-1, 320-2), a second or a charging enabling transistor 20 (330), and a variable capacitor (130-1). Switch-type devices can be used instead of transistors, and as discussed earlier, the initial state can be established after placing the MEMS in a known state of charge. In the initial state, this top or first plate (135-1) is connected to the first clear node (320_1) by the clear transistor (300), and the second or bottom plate (140-1) is connected to the second clear node 15 200525851 (320-2). More specifically, in the illustrated implementation, this first board (丨 milk- 丨) is connected to a first clearing node (320-1), which is set to a first clearing voltage by providing a path therebetween. In the MEMS (100-1) illustrated in FIG. 3A, the 5 clear transistor (300) and the enable transistor (310) are turned on, and the charge enable transistor (330) is turned off. Therefore, the first board (130-1) is connected to the first clear node (320-1), which is set to the first clear voltage. As explained previously, the second board or backplane (140-1) is connected to node 320-2, which is set to the second clear voltage. The first and second clear voltages 10 are at substantially the same voltage level, so that connecting them to the first and second boards (135-1, 14 (M) will connect the first and second boards ( 135-1, 140-1) are placed in substantially the same state of charge. In this case, where there is no charging difference between the first and second plates (135-1, 140-1), this variable gap difference (145-1) is at its maximum value. 15 In some cases, it may be desirable to clear the MEMS device to a known charge state other than a state where there is no charge difference between the two boards. In these states, it can be independently controlled at The first and second clearing voltage levels on the nodes (320-1, 320-2), and the first and second plates (135-1, 140-1) are placed: corresponding to a known variable gap distance (145-1) is known. 20 Figure 3B is a schematic diagram of the MEMS (100-l) when the input node (340) is precharged. After the variable capacitor (130-1) is reset The input node (340) is precharged. By turning off the enable transistor (310) and the clear transistor (300), and turning on the charge enable transistor (330), the The input node (340) is pre-charged to the selected acceleration drive reference voltage. The size of this pre-charge is larger than this charging value, which corresponds to the value between the first and second boards (135-1, 140-1). The desired final variable gap distance (145-1). This input node (340) is charged because: as mentioned earlier, the clear transistor (300) and the enable transistor (310) are cut off. Therefore, The drain of the clear transistor 5 (300) and the source of the enable transistor (310) are isolated from the capacitor node (110-2) and the first clear node (320-1). The current of the accumulated charge It is represented by the big arrow (A). Figure 3C is a schematic diagram of the MEMS (100-1) when the charge is pulsed to the variable capacitor (130-1). As shown in Figure 3C, charging is enabled 10 The transistor (330) is turned on like the enabling transistor (310), which causes the enabling transistor (310) and the charging enabling transistor (330) to serve as conductors. Therefore, the Vref (350) and the first conductive device are conductive. A path is established between the plates (135-1). As previously discussed, Vref (350) is accelerated so that the first and second plates (135 The charging difference between -1, 140-1) is greater than the desired final charging value. 15 This final charging value directly corresponds to the desired variable gap distance (145-1). Because this clears the transistor (3 〇〇) is cut off to prevent the potential of this input node (340) from falling to the first clear voltage existing on the first node plus ^. Therefore, the charge accumulated on the input node (34〇) can flow, Or pulsed to the variable capacitor (130-1). The charge of this pulse flows across the enabling transistor (310) to the first plate (135-1). The time during which the enabling transistor (310) is turned on or held in a conductive state is called a pulse period. As explained above, the time period of this pulse period is smaller than the mechanical time constant of the MEM device (110-2). In addition, this pulse period can be at least as long as: the electrical time constant or 17 200525851 RC time constant of the variable capacitor and the corresponding MEE (100-1) circuit. As previously discussed, this mechanical time constant causes a delay in the movement of the first and second plates (135-1, 14 (H), which is caused by a change in charge on the variable capacitor (130-1). Therefore By applying a selectable control voltage from VREF (350) to the surface device according to the time period of the enable signal, Q-2Wb During the reference voltage application, the variable capacitance of this MEM device (no-2) appears to be " Fixed ". 10 15 20

In addition, by accelerating the reference voltage (350) to drive the enable signal for a period of time, 'the charging difference between the first plate and the second plate (135-i, 14 (M) is greater than the variable gap distance. (145_υ required to move to the final value. This larger charge causes two plates (丨 丨 ~ 丨, 14〇_υ has a larger attraction. As previously discussed, this larger suction force causes two plates (135 small 14 (M) move faster towards each other. Figure 3D is a schematic diagram of the MEMS (1G (M) after applying the acceleration drive reference voltage (35)) to the variable electric coupling (130 1) Disconnect the variable capacitor from node ⑽) by cutting off the enabling transistor (310).

, Σ AC capacitor (13G-1) and other circuits include the charge control power s (12 ± 5-1). #This variable capacitor (⑽— 丨) is in an isolated / middle% two plates (135-Bu 140-1) move towards each other in response to the _th plate and the second plate (135_Bu 14 (M) The attractiveness caused by the difference in charging. When this first and second plate (135 ′ and 14 (M) are moved towards each other j, their relative movement rates are as previously discussed by the elastic force of the variable capacitor ⑽_ The balance of static electricity is related to the magnitude of the force. Therefore, this is more decisive than ^ P gravitational force that the first plate and the second plate (m, "㈠" are facing each other). Therefore, these plate calls correspond to their unaccelerated Driven by 18 200525851, the shapes move toward each other at a greater rate. Tian Tian's first and second plates (135—i, 14—D move towards each other on the day 'this variable gap distance ⑽— 丨) is close to the desired The final value. If allowed, it will be maintained during the acceleration drive charging on the container (13 (M) at noon: if the length is 5 and the electric valley is a mechanical time constant of (130- 丨), then this variable gap The distance (145 1) can be smaller than the desired final value. Moving the variable gap distance to the desired final value can be changed from the variable capacitor ⑽_υ Remove the pre-selected amount of charge and move the first and second plates (1354, 140-1) to the desired final value of the owable gap distance (145-1), as will be discussed in more detail in the following. —Figure 3E is a schematic diagram of MEM (100__υ) when a preselected amount of charge is removed from the first conductive plate (135-1) of the variable capacitor (丨 刈 一 丄). The conductive plate ⑽-1) removes a preselected amount of charge. Here, the first plate (135-1) and the first clearing node (320443) establish a path for a predetermined amount of time. This node is set to the acceleration drive compensation voltage at this time. This path is established according to the same process as described with reference to Figure 3A, except that the first plate of the variable capacitor (110-2) is not raised to the same voltage as the second plate (140-1) Instead, the first clearing node ⑽— ^ is set to the acceleration drive compensation voltage. This acceleration drive compensation voltage is set to a one-digit 20 level, which corresponds to the pre-selected amount of charge that is removed. By setting the charging transistor ( 310) is turned on with the clear transistor (300), and A conductive path is formed between the-plate (135-1) of the (130-1) and the -clear node (32 ()-υ). Then, after a period corresponding to the removal of a preselected amount of charge, the charging transistor is removed by (31〇) cut off this conductive path. 19 200525851 removes a preselected amount of charge from the first plate ⑽]), resulting in a difference in charge between the first plate and the second plate (135-Bu14 (M) , Which corresponds to the final value of the variable gap distance ⑽-1).-Once this county selects the number of charges from the first plate (135 1), as described with reference to the figure, the variable capacitor is crying 5 (1 Plus _1) is electrically isolated from other circuits again. In summary, Figures 3A to 3E show the outline of the circuit, in which Vref (35〇) is accelerated to reduce the movement of this first board and the second board (1351, ΐ4〇ι) to the final variable gap distance ( 145-1) Time required for separation distance. This required time can be reduced by accelerating the drive of VREF (350), and thus accelerating by 10 to accumulate charge on the first board, to allow the boards (135-1, 140-1) to move quickly towards each other in response to Charging difference between the first and second boards. After the first plate (135-1) has completed its part towards the desired final mechanical state, 'a predetermined amount of remaining charge is removed from the variable capacitor (130-1), so that the charging difference corresponds to the final available The variable gap distance (Milk- 丨), and I5 allows the variable gap distance (145-1) between the first plate and the second plate (135-1, 140-1) to stabilize at its final value. More specifically, the VREF (350) is connected to the first board (135-1) for a preset time to accelerate the charging difference between the first board and the second board (135-1, 140-1). The variable capacitor (130-1) is then electrically isolated from other circuits. When the variable capacitor (130-1) is electrically isolated from other circuits, this acceleration drive charging difference causes: the first board and the second board (135-1, 140-1) move toward each other faster. When the variable gap distance (145-1) between the first plate and the second plate (135-1, 14 (M) is close to the desired final value, the top plate (135-1) and the first plate Clear the node (320-1) connection and remove the excess charge 20 200525851. This node is now set to accelerate the drive compensation voltage. Then, the variable capacitor (130-1) is isolated from other circuits again, and this first The variable gap distance (145-1) between one plate and the second plate (135-1, 140-1) is stable at its final value. 5 As discussed earlier, accelerating the voltage drive can reduce: Time required for the variable gap distance (145-1) between the two plates (135-1, 140-1) to move to the final value of the variable gap distance (145-1). For example, according to a typical embodiment, this will The typical time required to move the variable gap distance from the initial gap distance of 4000A to the desired gap distance of 959A ± 50A is about 3.145 // S. 10 This time is a diffracted ray with an area of 800 // m2 Device (DLD) typical required time. Moving the first and second boards by the voltage acceleration driving method can reduce this time to 1.045 // s or less. In optical imaging applications, these MEM devices are used as light modulators. By reducing the moving time of these first and second plates (135-1, 140-1), the unwanted images are artificially 15 Minimize the effect. Figure 4 is a block diagram illustrating a typical micro-electromechanical system (MEMS, 400). This MEMS (400) includes MEM units (410) of M columns x N row arrays. Each MEM unit (4Ί0) includes: MEM Device (110-3) and switch circuit (125-2). Although it is not shown for a while, 'Each MEM device (110-3) further includes 20 first and second conductive plates. Variable capacitors separated by variable gap distance, as shown in Figures 3A to 3D. Design each switching circuit (125-2) to control: stored on the variable capacitor of the mem device (110-3) The amount of charge, so control the variable gap distance. Also design each switching circuit (125-2) to provide the charge, whose number 21 200525851 is greater than the number of charges corresponding to the final value of the variable gap distance. Also design each switching circuit ⑽- 2) Take the pre-selected amount of charge from _device ⑽-3) so that it The remaining charge corresponds to the final variable gap distance between the conductive plates. 5 Each row of this array ^ is connected with & each clear (㈣, enable (430), and charge (440) 仏. All switch circuits (125-2) of the given row receive substantially the same Clear and enable signals. Each row of the array is received: the individual reference voltages (Vref, 450) for a total of N reference voltage signals.

10 In order to store the desired charge or, write, or each MEM device (11 ~ 3) of a given column of MEM cells (410), provide this acceleration drive reference voltage with the selected value to Each of the N lines, and each of the financial reference voltage signals may have different selection values. These clear signals (42 °) and enable signals (43 °) are first pulsed to cause each switching circuit (125-2) of this given column to place 15 sets of MEM (110-3) in a known charge Status. As previously discussed, these clear # numbers (420) and enable signals (43) can remove or clear any possible stored charge from their associated mem device (110-3). The charge removal signal (460) is set to the first clear voltage at node 320-1 (Figure 3A), and the charging difference between the first board and the second board is placed in a known charging state. Then 20 gives a charge enable signal (440) for a given column, and the input nodes of each relevant MEM device (110-3) are precharged. Then, the enabling signal (430) "for each given row is pulsed to cause each switching circuit (125-2) of the given row to apply its relevant reference voltage to the relevant MEM device (110- 3) A predetermined period of time. For example, 22 200525851 isolation. As discussed previously, this reference voltage will accelerate the charge accumulated on the variable capacitor. Therefore, this amount is greater than the electricity based on the last charge value = there is a relevant The variable capacitor is forced, so the variable gap distance is forced toward the final value. Then, when this is accelerated by the charge, the electric board is moved towards the desired position ^ will be set (UG_3) to other circuits

Reapply clearing ㈣⑽) and enable signal () again to remove the selected amount of charge from the conductive plate. This clear pulse results in the same effect as the first clear pulse, but with a shorter pulse duration, only a selected amount of charge is removed from the variable capacitor U). Therefore, the charge removal signal is set to the acceleration driving compensation voltage during the second clear pulse. The selected amount of charge is removed from the variable capacitor, leaving a difference in charge present on the conductive plates, which corresponds to a variable final gap distance between the conductive plates. After removing this selected amount of charge, these conductive plates are allowed to mechanically stabilize to their final value. Repeat this procedure for each column of this arrow, and write the desired charge to each MEM cell (410) of the array. In the embodiments discussed with reference to Figures 1 to 4, design these switching circuits ( 125, 125-1, 125-2) to control the voltage. In other embodiments, these switching circuits (125, 125-1, 125-2) can be designed to control the current. 20 In this embodiment, This switching circuit can be a transistor that functions as a current source. For example, in the triode region, the enabling transistor can function as a resistor to control the current. In addition, the enabling transistor can directly act as a current source in the saturation region. Will accumulate a current pulse on the input node (340). Then pulse this pulse current to the variable capacitor, as previously discussed in 23 200525851 to charge the variable capacitor. The above description is only provided to describe and illustrate the method of the invention And device. But its intention is not exhaustive, or to limit this method and device to any exact form disclosed. Because the above disclosure can make many modifications and 5 changes to it. Its intention is to The scope of the definition is defined by the scope of the following patent applications. T Brief description of the diagram 3 Figure 1 is a simple block diagram illustrating a micro-electromechanical (MEMS) device according to a typical embodiment of the present invention; 10 Figure 2 is a cross section FIG. 3A illustrates a microelectromechanical device according to an exemplary embodiment of the present invention; FIG. 3A is a schematic diagram illustrating a microelectromechanical device when a charging difference is removed from a variable capacitor according to an exemplary embodiment of the present invention; FIG. 3B is an overview Figure 3 illustrates a micro-electromechanical device during operation before charging according to a typical embodiment of the present invention; Figure 3C is a schematic diagram illustrating a micro-electromechanical device during charging pulse operation according to a typical embodiment of the present invention; The figure is a schematic diagram illustrating a typical micro-electro-mechanical device during stable operation; FIG. 3E is a schematic diagram illustrating a typical micro-electro-mechanical device during charge removal operation; and FIG. 4 is a block illustrating a typical MEMS device. In the figure, this device has multiple MEMS cells in the MXN array. [Description of Symbols of Main Components] 24 200525851 100 ... Micro-electro-mechanical system 100-1 ... Micro-electro-mechanical system System 105 ... Charge control circuit 110 ... Micro-electro-mechanical device 110-1 ... Micro-electro-mechanical device 110-2 ... Micro-electro-mechanical device 110-3 ... Micro-electro-mechanical device 115 ... Variable power source 120 ... Controller. 125 ... Switching circuit 125-1 ... Switching circuit 125-2 ... Switching circuit 130 ... Variable capacitor 130-1 ... Variable capacitor 135 ... First conductive plate 135-1 ... First conductive plate 140 ... Second conductive plate 140-1 ... Second conductive plate 145 ... Variable gap distance 145-1 ... Variable gap distance 150 ... Passage 155 ... passage 160 ... passage 165 ... passage 170 ... passage 175 ... charge control circuit 200 ... top reflector 210 ··· Bottom reflector 220 ... Flexible 230 ··· Spring mechanism 240 ·· Optical cavity 300 ··· Clear transistor 310 ··· Enable transistor 320-1 ··· First clear node 320 -2 ... Second clear node 330 ... Charging enable transistor 340 ... Input node 350 ... Reference voltage 400 ... Micro-electro-mechanical system 410 ... Micro-electro-mechanical system unit 420 ... Clear Signal 430 ... Enable signal 440 ... Charging signal 450 ... Reference voltage 460 ... Remove charging signal

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Claims (1)

200525851 Scope of patent application: Method, which includes the following-a step of driving a parallel plate variable micro-electromechanical capacitor step '5 10 15 20 across the first and the first of the variable capacitor-Tian 4 Le-cold spin plate to establish the first charge Difference, wherein the first and second lightning guides are separated; ¥ ^ * 板 疋 精 isolates the first and second plates by a variable gap distance for a first time period, and reduces the charging difference to less than the first The last of a charging difference = electrical difference, and wherein the second charging difference corresponds to a second value of the variable gap distance. 2. The method according to item 1 of the patent application, further comprising isolating the first-second board from the second board for a second time period after reducing the charging difference. 3. The method according to the third aspect of the patent application, wherein establishing the first charging difference includes: connecting the first conductive plate to a reference voltage source, and connecting the second conductive plate to a clearing voltage. 4 · If the scope of patent application is the first! The method of claim, wherein the first charging difference causes an initial attractive force between the first and second conductive plates, which is greater than a second attractive force corresponding to the second value of the variable gap distance. 5 · If the scope of patent application is the first! The method of this item, wherein the parallel plate variable MEM electric benefits include: an optical modulation device mainly based on diffraction. 6 · —A method of driving a diffraction-based optical modulation device, including the following steps: Establishing an initial known state of charge of the first and second conductive plates of the variable capacitor, wherein the first and second conductive plates The plates are separated by a gap distance of 26 200525851; a first charge difference is established across the first and second conductive plates of the variable capacitor to force the first and second conductive plates to move toward each other; One from the second conductive plate for the first time period; and the 5th charge difference is reduced to less than the second charge difference from the first charge difference ', and wherein the second charge difference corresponds to a second value of the variable gap distance; And isolating the variable capacitor for a second time period to allow the first 1 and the second plate to stabilize at the second value of the variable gap distance. 7. The method of claim 6, wherein establishing the known state of charge includes: connecting the first conductive plate to a first clearing voltage, and connecting the second conductive plate to a second clearing voltage. 8. A charge control circuit comprising: a variable power supply; and a 15 switching circuit designed to transfer accelerated drive pulse charges from the voltage source to a variable capacitor ϋ, to isolate the variable capacitor for a preset time period, and The selected amount of the accelerated driving charge is removed from the variable capacitor so that the charge remaining on the variable capacitor substantially corresponds to the second state of charge. 20 Q • The charge control circuit according to item 8 of the patent application scope, wherein the switching circuit further includes a first clearing node, wherein the first clearing node selectively switches between the first clearing voltage and the compensation voltage, so that the The variable capacitors are connected to the first clearing node. When the first clearing node is at the first clearing voltage, the variable capacitor is placed in the state of charge 27 200525851 originally known, and the variable A capacitor is connected to the first clearing node, and when the first clearing node is at the compensation voltage, the selected amount of the accelerated driving charge is removed. ίο. —A micro-electromechanical system, comprising: 5 arrays of micro-electromechanical units of XN rows, each of which includes a micro-electromechanical device (MEM device) having a first conductivity separated by a variable gap distance The variable capacitance formed by the plate and the second conductive plate is that a switching circuit has an input node, which is designed to receive a reference voltage at a selected acceleration driving voltage level, and is designed to respond to this charging signal to accelerate The driving pulse charge pre-charges the input node to the selected accelerated driving voltage level, and the switching circuit is designed to respond to the enable signal and apply the selection across the first and second boards of the variable capacitor of the MEM device. The accelerating driving voltage level has undergone this period of 15 times, thus causing the accelerating driving pulse charge to accumulate on the variable capacitor, and wherein the switching circuit is designed to respond to the charge removal signal and remove the selected amount from the first conductive plate. Of its charge.