阅读说明：本技术 一种用于确定致动器的位置的方法 (Method for determining the position of an actuator ) 是由 罗曼·古铁雷斯 王宏宇 于 2015-10-15 设计创作，主要内容包括：系统和方法提供了致动器控制。致动器控制经由与电压控制相反的电荷控制提供。用于驱动致动器的驱动器可以包括用于将电荷注入到致动器的一个或多个电容元件中的电荷泵。驱动器可以进一步包括用于检测致动器的电容元件的电容的电容检测方面以确定致动器的位置。(Systems and methods provide actuator control. Actuator control is provided via charge control as opposed to voltage control. A driver for driving the actuator may comprise a charge pump for injecting charge into one or more capacitive elements of the actuator. The driver may further comprise a capacitance detection aspect for detecting a capacitance of a capacitive element of the actuator to determine the position of the actuator.)

1. A method for determining a position of an actuator, comprising:

continuously charging and discharging an actuator to effect movement of the actuator;

determining a capacitance of the actuator by sensing a voltage at an input of the actuator in order to determine a position of the actuator resulting from movement of the actuator; and is

Measuring a slope of a voltage ramp up or ramp down generated by the continuous charging and discharging with a differentiator circuit and an analog-to-digital converter (ADC), the voltage ramp up being a function of the capacitance of the actuator.

2. The method of claim 1, further comprising adjusting the charging and discharging periods to be longer or shorter relative to each other to allow for a desired movement of the actuator.

3. The method of claim 1, wherein the frequency of the charging and discharging is greater than a mechanical resonant frequency of the actuator to prevent unintentional movement of the actuator.

4. The method of claim 1, wherein the measuring of the voltage ramp comprises measuring a ramp in output voltage.

5. The method of claim 4, wherein the measuring of the voltage ramp further comprises measuring a peak voltage associated with the ramp in output voltage.

6. The method of claim 1, further comprising measuring a time between changes in the output voltage reflected by the voltage ramp up and ramp down with a comparator.

7. The method of claim 1, wherein the determining of the capacitance of the actuator further comprises sampling a voltage induced by successive charging and discharging of the actuator.

8. The method of claim 1, wherein the determination of the capacitance of the actuator comprises generating a varying voltage at an input of the actuator that results in the voltage and sensing the coupling via a capacitor.

Technical Field

The present disclosure relates generally to electromechanical devices and systems, such as microelectromechanical systems (MEMS). More specifically, various implementations of the technology disclosed herein are directed to the use of MEMS actuators via charge control.

Background

MEMS electrostatic actuators or transducers have a number of applications, from accelerometers to gyroscopes, to pressure sensors, microphones, and the like. MEMS typically include components or elements that may be less than 1 μm to several millimeters, where at least some of the elements have some mechanical function or aspect related to them. For example, MEMS-based motion sensors for digital cameras have been developed to address image degradation due to human hand tremor or other blur-induced motion, e.g., MEMS-based gyroscopes can be used to sense camera motion. In response to the sensed motion, an Optical Image Stabilization (OIS) system attempts to move a lens or image sensor to reduce or eliminate motion-induced blur of the resulting image, which may also be achieved using MEMS-based actuators.

One example of a MEMS-based actuator relies on the use of a comb drive having at least two comb structures in opposing orientations similar to interlocking teeth. Attractive electrostatic forces may be generated when voltages are applied to the comb drive, resulting in the comb structures being brought together, where those forces are proportional to the change in capacitance between the comb structures. Such a device is therefore a conventional pressure-controlled device. Further, the operation of the comb drive may be based on granularity or resolution provided, for example, by a digital-to-analog converter (DAC). DACs are commonly used to drive such devices because the associated electrostatic forces are non-linear and therefore an appropriate digital value must be used to provide the appropriate amount of voltage to drive the device.

Disclosure of Invention

Systems and methods are provided in various embodiments for controlling a MEMS actuator via an electrical charge. According to one embodiment of the technology disclosed herein, the driver device includes a charge pump that generates the voltage required to inject charge into the actuator. The driver device further comprises a charge sink through which the actuator can be discharged, wherein the charging and discharging of the actuator effects a movement of the actuator. Still further, the driver device includes a switch for operatively connecting the charge pump and the charge sink to the actuator.

In accordance with another embodiment of the technology disclosed herein, a driver device includes a driver circuit for driving a MEMS actuator via charge control so as to sense a voltage that causes a desired movement of the MEMS actuator while allowing the voltage to change. The driver circuit includes: a charge pump configured to inject charge onto the MEMS actuator; a charge sink configured to sink charge from the MEMS actuator; and a switch configured to switch at least one of the charge pump and the charge sink to the appropriate capacitive element of the MEMS actuator.

In accordance with yet another embodiment of the technology disclosed herein, a method includes continuously charging and discharging an actuator to effect movement of the actuator. The method further includes determining a capacitance of the actuator by sensing a voltage at an input of the actuator in order to determine a position of the actuator due to movement of the actuator.

Other features and aspects of the present disclosure will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with various embodiments. This summary is not intended to limit the scope of the invention, which is defined solely by the appended claims.

Drawings

According to one or more various embodiments, the techniques disclosed herein are described in detail with reference to the following figures. The drawings are provided for illustrative purposes only and merely depict general or exemplary embodiments of the disclosed technology. These drawings are provided to facilitate the reader's understanding of the disclosed technology and should not be considered limiting of its breadth, scope, or applicability. It should be noted that for the purposes of clarity and ease of illustration, the drawings are not necessarily to scale.

Fig. 1A is a perspective view of an exemplary mobile device in which various embodiments of the technology disclosed herein may be implemented.

Fig. 1B is a broken perspective view of the exemplary mobile device of fig. 1A.

FIG. 2 is a top view of an exemplary MEMS actuator utilized in accordance with various implementations of the technology disclosed herein.

Fig. 3 is a schematic diagram of an exemplary camera module including a charge controlled MEMS driver, in accordance with one implementation of the technology disclosed herein.

Fig. 4 is a schematic diagram of an exemplary camera module including a charge controlled MEMS driver, in accordance with another implementation of the techniques disclosed herein.

Fig. 5 is a schematic diagram of an exemplary high voltage only driver of the charge controlled MEMS driver of fig. 4.

Fig. 6 is an exemplary circuit diagram of the high voltage driver only of fig. 5.

Fig. 7 is a circuit diagram of an exemplary charge pump utilized in the high voltage only driver of fig. 5.

Fig. 8 is a circuit diagram of an exemplary charge sink utilized in the high voltage only driver of fig. 5.

Fig. 9 is a circuit diagram of an exemplary switch utilized in the high voltage only driver of fig. 5.

Fig. 10 illustrates exemplary timing waveforms utilized in various implementations of the technology disclosed herein.

Fig. 11 is a circuit diagram of an alternative embodiment of the high voltage only driver of fig. 5.

Fig. 12 is a circuit diagram of another alternative embodiment of the high voltage only driver of fig. 5.

Fig. 13 is a circuit diagram of yet another alternative embodiment of the high voltage only driver of fig. 5.

FIG. 14 illustrates an exemplary chip set that may be utilized in implementing structures and methods for controlling a MEMS actuator using electrical charge in accordance with various embodiments of the technology disclosed herein.

The drawings are not intended to be exhaustive or to limit the invention to the precise forms disclosed. It should be understood that the invention can be practiced with modification and alteration, and that the disclosed technology be limited only by the claims and the equivalents thereof.

Detailed Description

The actuator device may include one or more MEMS actuators or other electrostatic devices/mechanisms, and may be adapted for use in a variety of different electronic devices. For example, the actuator device may be suitable for use in a camera (such as a miniature camera), for example to manually or automatically focus the miniature camera, zoom the miniature camera, or provide OIS for the miniature camera. Further, the actuator device may be used to align optics within a miniature camera, or for any other desired application in an electronic device in which the actuator device may be utilized.

The actuator device may be formed using a unitary or non-unitary construction. For example, modern manufacturing techniques (such as etching and micromachining) may be used to form the actuator device. Various other fabrication techniques are also contemplated. The actuator device may be formed of silicon (e.g., single crystal silicon and/or polycrystalline silicon), or other semiconductors such as silicon, germanium, diamond, and gallium arsenide. The material forming the actuator means may be doped to obtain its desired conductivity. Alternatively, the actuator device may be formed from a metal such as tungsten, titanium, germanium, aluminum, or nickel, or some desired combination thereof. The actuator may be made of an organic material, such as plastic, photoresist, or epoxy, filled or coated with a conductive material to obtain the desired conductivity.

Motion control of the actuator arrangement and/or the items moved by the actuator arrangement may be used to promote desired movement of the items while mitigating undesired movement of the items. For example, motion control may be used to facilitate movement of the lens along the optical axis of the lens while inhibiting other movement of the lens. Thus, motion control may be used to facilitate movement of the lens in a single desired translational degree of freedom while inhibiting movement of the lens in all other translational degrees of freedom and while inhibiting movement of the lens in all rotational degrees of freedom. In another example, motion control may facilitate movement of the lens in all three translational degrees of freedom while inhibiting movement of the lens in all rotational degrees of freedom.

Accordingly, an enhanced compact camera for stand-alone use and for use in an electronic device can be provided. Compact cameras are suitable for use in a variety of different electronic devices. For example, small cameras are suitable for use in electronic devices such as cellular phones, portable computers, televisions, handheld devices, and surveillance devices. However, and again, the various embodiments may be applied to and performed in a myriad of MEMS devices and contexts.

As previously mentioned, conventional systems and methods of controlling movement in an actuator device rely on voltage control to drive one or more MEMS actuators. That is, a desired voltage may be applied to a MEMS actuator, such as a comb drive (an example of a capacitive actuator) to induce movement by utilizing the electrostatic force acting between two conductive combs. When a voltage is applied between the stationary and moving combs, an attractive electrostatic force is generated causing them to come together. The force developed by the actuator is proportional to the change in capacitance between the two combs, increasing the drive voltage, the number of comb teeth and the gap between the teeth. That is, the more voltage applied, the more movement can be induced. However, such systems have a non-linear response and high voltage systems (e.g., requiring 30V, 45V, or even greater voltages) where the comb drive position is proportional to the square of the drive voltage V2 (since force is proportional to the square of the voltage), require a large number of bits to achieve the required resolution when attempting to control movement. Furthermore, when the desired operating voltage exceeds what is referred to as the insertion voltage (insertion refers to an instability phenomenon, so, for example, a moving comb may be inserted laterally into a stationary comb), the instability of the comb drive actuator is a significant design limitation. Eventually, the voltage control of the electrostatic actuator causes the so-called electrostatic spring to soften, which reduces the stiffness of the actuator.

Thus, various embodiments are directed to systems and methods for controlling MEMS actuators using charge control rather than attempting to control drive voltage (as opposed to, for example, resistors (which are considered current or charge dependent devices), where traditional thinking characterized electrostatic devices such as capacitors as voltage dependent or variable devices). It should be understood that the capacitance (C) of the capacitor is equal to the charge (Q) stored on the capacitor divided by the voltage (V). Mathematically, the spring force (associated with the flexure of the comb drive) is equal to the compression distance multiplied by the stiffness factor, and the spring force (absent other forces, such as gravity) is equivalent to the electrostatic force. Thus, as described above, the position of the MEMS actuator is proportional to V2, or to Q2/3, where it can be appreciated that position has a more linear dependence on charge, Q2/3. Thus, when controlling charge rather than voltage, the required resolution is smaller and easier to implement.

Furthermore, stability can be improved in the comb drive design and its motion control system. In particular, when controlling the charge rather than the voltage, the limiting factor on the flexural stiffness requirements may be relaxed, or the maximum voltage may be increased (while still avoiding insertion). In a comb drive where the pawls are horizontally positioned, the mechanical equilibrium position without any applied electric field is: x is 0; y is Δ, where Δ represents the pawl offset. The comb driver pawls may have an initial overlap of 1, and a balance gap g (i.e., zero pawl offset case), where the pawls have a uniform width. This system can be represented as a parallel plate capacitance model, where pawl deformation is negligible. The aforementioned motion control system can be thought of as two independent springs moving in the x and y directions. When comparing drive to charge instead of voltage, the voltage driven comb drive and the charge driven comb drive have the same stiffness ratio requirement for stability purposes if the pawl remains in the center position, i.e., a is 0. Once the pawl is off center, the stiffness ratio of the voltage driven comb drive increases faster than required for the case of the charge driven comb drive as for the case where both the small and large pawls are offset. Thus, and again, driving the MEMS actuator with charge provides significant advantages over driving with voltage.

Further with respect to spring stiffness, control of the charging of the electrostatic actuator causes the electrostatic spring to stiffen in sharp contrast to voltage-controlled electrostatic spring softening. This effect can be advantageously used because the structure can be designed with lower stiffness that requires less force to move, while still operating as if it had higher stiffness, e.g., lower gravitational sag and higher resonant frequency. That is, and when charge control is used on an electrostatic actuator (such as a comb drive), the voltage increases when the capacitance decreases (i.e., the comb drive is off) and decreases when the capacitance increases (i.e., the comb drive is engaged). Thus, the electrostatic actuator has an electrostatic force that holds it in its stable position. This adds to the spring force holding it in place while the voltage remains constant. Again, this electrostatic force is essentially a spring force and may be referred to as an electrostatic spring stiffening force. The electrostatic spring constant is equal to twice the mechanical (or actual physical) spring constant, assuming the comb drive has zero overlap, x is 0 and when the charge is equal to zero, Q is 0.

Still further, control of the actuator via charge may be simpler than implementing voltage control, where an actuator utilizing charge control acts like a stepper motor, where each packet of charge injected results in increased movement. For example, in an OIS control system, a gyroscope is used to sense the rotational speed (θ point). A desired permittivity (C point of t) based on a desired movement of the image sensor is determined to compensate for the rotation speed measured by the gyroscope. The error in capacitance (position) is measured by measuring the capacitance and subtracting the desired capacitance. The time to wait before providing the next charge pulse can be calculated by taking into account the desired change in capacitance, the error in capacitance and the desired permittivity. When the capacitance needs to be increased, a charge command may be sent. When the capacitance needs to be reduced, a discharge command may be sent.

Thus, the MEMS actuator can be controlled by injecting charge. When a voltage is applied to the capacitor, it is actually charging. However, instead of attempting to precisely control the voltage to achieve the desired effect by incorporating voltage feedback and relying on an analog-to-digital converter to set the voltage (e.g., applying a drive voltage of 1/10 of mV and still inducing too much movement), the voltage is no longer considered. Conversely, a charge may be added to a voltage-based device (such as a MEMS actuator) to induce a voltage that causes movement of the MEMS actuator.

FIG. 1A illustrates a perspective view of an exemplary mobile device 11, which may be a mobile phone, including a miniature camera 12 in which various embodiments may be implemented. The miniature camera 12 may employ an image sensor package, such as a moving image sensor package. The miniature camera 12 may implement various functions related to movement of the image sensor, such as OIS, Auto Focus (AF), alignment between the lens and the image sensor, and the like. FIG. 1B illustrates the mobile device 10 of FIG. 1A with a housing/case portion exposed to display a miniature camera 12 in accordance with one embodiment of the technology disclosed herein. It should be noted that while the various embodiments disclosed herein are presented in the context of a miniature camera module for use with a mobile device, such as a mobile phone, tablet Personal Computer (PC), laptop PC, etc., the disclosed techniques may be adapted for use in other devices or contexts that incorporate actuation of MEMS devices.

As mentioned above, various embodiments of the technology disclosed herein may employ OIS functionality (such as three-axis OIS of operation) or may compensate for camera movement including roll, pitch and yaw (yaw) by moving the image sensor. Accordingly, devices such as the camera 12 may include a lens barrel, an Auto Focus (AF) actuator, and a moving image sensor package. The AF actuator may be a Voice Coil Motor (VCM) type actuator, a MEMS actuator, a piezoelectric actuator, a shape memory alloy actuator, or any other type of actuator.

Fig. 2 illustrates a top plan view of an exemplary MEMS actuator 17 with which the aforementioned OIS function may be implemented in accordance with various embodiments of the technology disclosed herein. To enable OIS, the MEMS actuator 17 may be used to move the image sensor inside the image sensor package according to "three degrees of freedom". Some examples of MEMS actuators suitable for moving image sensors are described in U.S. application serial No. 61/975,617, the entire contents of which are incorporated herein by reference.

In one embodiment, the MEMS actuator 17 may include a middle frame 18 with contact pads 19, an outer frame separated into two electrical poles 20, four actuation areas 21, a central anchor 23 with bonding holes 24, and a plurality of electrical connection flexures 22. The number of bonding holes 24 is not limited to one, as there may be a plurality of holes depending on the relevant electrical connection requirements. The bonding apertures 24 may have multiple uses, including, for example, enabling the structural adhesive to mount the MEMS actuator 17 to a carrier substrate by applying a thermal epoxy, and electrically connecting from the MEMS actuator 17 to a conductive trace or substrate by applying a conductive epoxy, solder, metal paste, or other electrical connection method. An external electrical pole 20 may provide a connection between the MEMS actuator 17 and the rest of the moving image sensor package. Contact pads 19 on the intermediate frame 18 may provide electrical connections between the image sensor (not shown) and the MEMS actuator 17.

Each actuation region 21 may comprise an electrostatic comb drive providing motive force in one linear direction. The four actuation areas 21 together provide for movement in the X and Y directions, as well as rotation about the Z axis. Thus, the MEMS actuator 17 can move in two linear degrees of freedom and one rotational degree of freedom to achieve OIS for a compact camera in all three rotational degrees of freedom. The actuation zone 21 is connected to the central anchor 23 by a parallel motion control flexure 43 and to the intermediate frame 18 by a connecting flexure 44 that is rigid in the freedom of motion and flexible in the other degrees of freedom. In one embodiment, the actuation area 21 includes features to limit mechanical movement during descent or shock to reduce stress on the parallel motion control flexures 43 and the connecting flexures 44. In one embodiment, the image sensor is attached to the outer frame 20 and center anchor 23, while the middle frame 18 is attached to the remainder of the mobile image sensor package.

It should be noted that the X/Y dimensions of the MEMS actuator 17 are related to the size of the moving image sensor package. In one embodiment, the outer dimensions of the intermediate frame 18 substantially match the size of the image sensor. In another embodiment, the outer frame 20 has outer dimensions that substantially match the size of the image sensor. In yet another embodiment, the MEMS actuator 17 is about 150 microns thick and has an in-plane dimension of about 8mm in the X dimension and about 6mm in the Y dimension.

Fig. 3 illustrates an exemplary camera module 50 that may include some or all of the foregoing elements of a moving image sensor. Included in the camera module 50 are a Digital Signal Processing (DSP) OIS controller 70 for controlling OIS functions, an image sensor 72, and an OIS gyroscope 74 for detecting movement such as roll, pitch and yaw. Also included in camera module 50 are a MEMS actuator 52, including one or more MEMS arrays 54, and a MEMS driver 56. MEMS driver 56 may control the movement of MEMS actuator 52 by injecting charge into MEMS actuator 52 and, in some embodiments, receiving position feedback from MEMS actuator 52. In one embodiment, the DSP OIS controller 70 and the MEMS driver 56 are integrated together into a single mixed signal Integrated Circuit (IC).

The MEMS driver 56 may drive the MEMS actuator 52 by injecting a charge commensurate with the control signaling from the DSP OIS controller 70. As will be described in more detail below, the MEMS actuator 56 is operated by increasing or decreasing the voltage output (by charging the charge pump 58 (charging capacitor) and discharging the charge sink 60 (discharging capacitor)). As shown in this embodiment, MEMS driver 56 may be a mixed signal Integrated Circuit (IC) or chip. That is, the MEMS driver 56 may have a high voltage portion for driving a high voltage device (e.g., MEMS actuator 52), and a digital signal/low voltage portion (e.g., a serial-to-parallel interface (SPI) interface). According to another embodiment, such as will be described below, the high voltage controller will be implemented separately.

Thus, the MEMS driver 56 may be configured as a high voltage driver while also providing capacitive sensing. That is, the capacitance sensing module 64 may sense the MEMS actuator 52, which may be one or more capacitive comb drive elements, to determine the magnitude of the capacitance, and thus the position of the MEMS actuator 52, which may then be communicated to the DSP OIS controller 70.

Specifically, a high voltage (e.g., 45V) is provided to drive the MEMS actuator 52 by injecting charge using the charge pump 58, the charge pump 58 also being connected with the DSP OIS controller 70 via the SPI (or I2C bus in other embodiments). Charge controlled analog circuits such as those described herein may be used in mixed signal ICs that use SPI instead of a parallel digital interface to reduce pin requirements. Thus, the charge-driven arrangement is suitable for digital control and allows a reduction in the complexity of the resulting electronic device. The switch 62 may switch the charge pump 58 and charge sink 60 circuits to the appropriate devices. With the same connections used to inject and absorb charge, capacitive sensing can be achieved by detecting the appropriate capacitance of MEMS actuator 52 and communicating this information to DSP OIS controller 70 via SPI or I2C. Capacitive sensing can be performed by various methods, including but not limited to sensing the amplitude and phase of the AC signal (varying voltage) fed back through the MEMS capacitor; charging or discharging the MEMS capacitor and paying attention to the time taken to charge or discharge; or charge and discharge the MEMS capacitor and focus on the slope of the voltage with a differentiator. Further, the DSP OIS controller 70 may communicate with the image sensor 72 and the OIS gyroscope 74, for example, via a digital interface.

Fig. 4 illustrates an exemplary camera module 80 that may include some or all of the foregoing elements of a moving image sensor. Included in the camera module 80 are a DSP OIS controller 84 for controlling OIS functions, an image sensor 72, and an OIS gyroscope 74 for detecting movement (such as roll, pitch and yaw). Also included in the camera module 80 are: a MEMS actuator 52 comprising one or more MEMS arrays 54, which may be one embodiment of MEMS actuator 17 of FIG. 2; and a MEMS driver 82, which may be a high voltage only MEMS driver. That is, MEMS driver 82 includes only high voltage driver circuitry without any low power circuitry or digital block.

MEMS driver 82 may control the movement of MEMS actuator 52 by injecting charge into MEMS actuator 52 and drawing charge outside of MEMS actuator 52. The MEMS driver 82 may drive the MEMS actuator 52 by injecting a charge proportional to a clock pulse via Pulse Width Modulation (PWM) and a clock module 86 of the DSP OIS controller 84. As will be described in more detail below, the PWM aspect of PWM and clock module 86 operates to interface with MEMS driver 82 (parallel digital interface) to increase or decrease the voltage output by charging from the high voltage generated by the charge pump or other circuitry that generates the high voltage (e.g., above 45V) and discharging to the charge sink.

Independent of the MEMS driver 84, capacitance sensing is performed in the DSP OIS controller 82, where an AC signal may be sent (via the AC module 88) to a portion of the MEMS driver 82 (described in more detail below) and onto the MEMS actuator 52, which may be one or more capacitive comb drive elements to sense the coupling to determine the magnitude of the capacitance, and thus the position of the MEMS actuator 52. It should be noted that although the figures show ADC 90 and AC generator 88 working together to sense the capacitance of MEMS actuator 52, many other methods of capacitance sensing may be used, using a combination of low voltage DSPOIS controller 84 and high voltage MEMS driver 82. For example, capacitive sensing may be performed by various methods, including but not limited to sensing the amplitude and phase of an AC signal fed back through a MEMS capacitor; charging or discharging the MEMS capacitor and paying attention to the time taken to charge or discharge; or charge and discharge the MEMS capacitor and focus on the slope of the voltage with a differentiator.

Fig. 5 is a schematic diagram of a high voltage only MEMS driver 82 comprising a charge pump 81, a charge sink 83 and a switch 85. The charge pump 81 receives clock signals Φ 1 and Φ 2 and an input voltage Vin (which may be multiplied by a desired amount due to an output voltage Vout (e.g., 45V)). Fig. 6 shows an exemplary circuit diagram of MEMS driver 82 of fig. 5, further showing charge pump 81 connected to switch 85 and in this example to the outputs of 6 MEMS actuators (C _ memsl, C _ MEMSs 2, C _ MEMSs 3.... C _ MEMSs 6). The charge capacitor C _ charge may be about 1pF to achieve a displacement resolution of approximately 0.5 μm. The discharge capacitor C discharge may also be approximately lpF to achieve a displacement resolution of approximately 0.5 μm. The AC signal for capacitive sensing may be a sine wave with a frequency of 10KHz, for example, where capacitive sensing has a resolution of 12 bits. The ADC speed may be, for example, 100KHz, with higher ADC speeds being better. Although there may be a tradeoff in sensing accuracy with capacitance, the smaller the charge/discharge capacitance, the higher displacement resolution that can be achieved. For example, with a 10KHz AC signal, a 100KHz 12-bit ADC, and a 1pF charge/discharge capacitor, achieving 1pF capacitive sensing accuracy may include injecting AC from different paths (e.g., separate capacitive sensing from charging and discharging). Further with respect to capacitive sensing, it should be noted that in order to achieve accurate capacitance measurements, the AC sine wave preferably has a very stable amplitude and frequency, with an amplitude error of less than 0.1%. Furthermore, the AC sine wave frequency (and the frequency of charging/discharging) can be programmed or optimized to avoid hitting any mechanical resonance frequency of the MEMS actuator. The clock for PWM may be about 48 MHz.

Fig. 7 shows a simple example of a charge pump, in this case a 4-stage (x5) Dickson charge pump stage (V1 to V2 to V3 to V4) of a metal oxide semiconductor fet (mosfet) MD1-MD5 with diode wiring, promoting Vin growth, the last capacitor C _ charge, in a chain setting the amount of charge injection that will ultimately be sent to MEMS actuator 52. Other more advanced charge pump designs exist in the art to achieve the desired Vout, e.g., above 45V. As described above, the charge injected into MEMS actuator 52 is controlled according to various embodiments rather than attempting to control the voltage applied to MEMS actuator 52. It should be noted that current control may be added to the charge pump 81.

The charge sink 83 of fig. 5 and shown in more detail in fig. 8 sets the amount of charge absorbed. Charge sink 83 receives clock signal Φ 3 and, when switched to connect to MEMS actuator 54, discharges MEMS actuator 54. Specifically, the FET, MD6, may be used to drain a single capacitor charge. It should be noted that discharge capacitor C _ discharge of charge sink 83 sets the resolution of the amount of charge to discharge from MEMS actuator 54. According to capacitive sensing, an AC signal may be provided during charge and discharge cycles, where the MEMS ground is connected to the digital chip to sense the AC signal delivered to the MEMS actuator 54. It should be noted that current control may be added to the charge pump 81 and the charge sink 83 (as will be described in more detail below).

The charge sink 83 and the charge pump 81 operate in conjunction, wherein during a clock pulse or signal, the capacitor C _ charge of the charge pump 81 is charged and the capacitor C _ discharge of the charge sink 83 is discharged. For MEMS actuator 54, which again is or can be considered a capacitive element, if more charge is desired to effect the desired amount of movement, switch 85 (which can be an array of FETs as shown in fig. 9) can be flipped to connect charge pump 81 (specifically, capacitor C _ charge) to MEMS actuator 54. MEMS actuator 54 and charge pump 81 capacitors will then balance in charging until the two have the same voltage. If it is desired to open the comb, switch 85 can be flipped to connect MEMS actuator 54 to charge sink 83 (specifically, capacitor C _ discharge) so that the charge in MEMS actuator 54 will dissipate until charge sink 83 and MEMS actuator 54 equilibrate to the same voltage. This process may be repeated continuously according to a clock pulse, e.g., 1MHz, 10MHz, 100MHz, etc., where charging and discharging may occur simultaneously. The continuous charging and discharging of the charge pump 81 and the charge sink 83 ensures that the last capacitor of the charge pump 81 is always fully charged and the capacitor of the charge sink 83 is always fully discharged. It should be noted that the respective capacitances of charge pump 81 and charge sink 83 are as small as possible relative to the capacitance of MEMS actuator 54 to obtain the best resolution.

As mentioned above, the AC signal may be injected into charge sink 83 to measure the capacitance of MEMS actuator 54 by monitoring how much AC signal makes it reach MEMS actuator 54.

FIG. 10 illustrates timing pulse waveforms for controlling the above-described circuits according to various embodiments. As shown in fig. 10, when Φ 2 is high, one of the MEMS actuators can be charged by the charge pump capacitor (e.g., C _ charge in fig. 6) by turning on its switch (phi 2 in fig. 6). When Φ 3 is high, one MEMS actuator can discharge through the charge sink capacitor (C discharge) by turning on its corresponding switch (phi 3 in fig. 6). It should be noted that the timing pulse waveform is such that Φ 2 and Φ 3 are not high at the same time, and Φ 1 is Φ 3, and Φ 2 is Φ 4. The clock signal Φ 4 and its corresponding switch phi 4 allow grounding of the discharge capacitor after it has been charged by phi 3 by connecting to the MEMS capacitor. A capacitance may be sensed during charging or discharging, wherein when the capacitance is determined, the particular MEMS actuator being sensed is in a connected state, i.e., such that an amount of AC signal that causes it to reach the MEMS actuator may be determined.

In the foregoing example and figures (e.g., fig. 6), the exemplary circuit diagram is a circuit diagram of a circuit having ten interface ports (including six switches, each controlling the charging and discharging of one MEMS actuator/capacitor). Fig. 11 shows an alternative circuit diagram in which the number of interface ports can be reduced to, for example, seven. The number of control ports for the switches can be reduced to three instead of six by encoding them into a binary format. For example, 111 turns on SW1, 110 turns on SW2, and so on. It should be noted that an inverter would be utilized in the high voltage driver chip. As previously described, digital circuitry may also be incorporated to convert a parallel digital interface to a serial interface (e.g., SPI or I2C) to further reduce pin requirements.

FIG. 12 shows an alternative circuit for sensing capacitance according to another embodiment. Specifically, capacitive sensing in this example includes switching the MEMS capacitor between charging (i.e., Φ 2) and discharging (i.e., Φ 3). The current drawn into and out of the MEMS capacitor is converted to a voltage by a resistor connected to ground at the output of the MEMS capacitor. A Low Pass Filter (LPF) may be implemented on the output to combine the voltages and generate a low voltage signal that may be read by low voltage electronics to determine the capacitance of the connected MEMS actuator. That is, if switching between charging and discharging, the peak-to-peak voltage may be measured to determine the capacitance. When multiple successive charge and discharge pulses are used, the waveform pattern can then be digitized.

Fig. 13 shows a further alternative circuit, in which the continuous charging and discharging of the MEMS capacitor generates a linear ramp up and ramp down of the voltage. The slope of this triangular voltage ramp is measured as a function of the MEMS capacitance using a differentiator circuit and an analog-to-digital converter. Alternatively, the time taken to change the output voltage may be measured using, for example, a comparator and a counter. Current source I1 elements and current sink I2 elements may be used in place of the charge and discharge capacitors (C _ charge and C _ discharge of fig. 6, 11, and 12). The current source I1 may be, for example, a current source of about 10 μ Α, and the current sink may be, for example, a current sink of about-10 μ Α. Again, FET array switches may be utilized to connect the charge and discharge circuits to the MEMS capacitors. In this case, the amount of time that the MEMS capacitor is connected to the current source or sink, as controlled by the length of the PWM control pulse, determines the amount of charge injected or removed from the MEMS capacitor.

A capacitance sensing RC circuit may be provided for each MEMS capacitor, where the capacitance sensing output (cap sense1-6) is sent all to a single output port using, for example, FET switches or by multiplexing. Specifically, appropriate switches (SW1-SW6) may be used to connect to the appropriate/selected MEMS actuator (C _ MEMS1-C _ MEMS6) and the charge switch SW _ charge may be turned on for some charge time, T _ charge (e.g., 250 μ s). Subsequently, the charge switch SW _ charge may be turned off and the discharge switch SW _ discharge may be turned on for some discharge time T _ discharge (e.g., 250 μ s). The voltage across the associated reference resistor R _ ref1-R _ ref6 can be measured. During the charging cycle, the voltage across the reference resistor will stabilize at R _ ref _ I _ source _ C _ ref/(Cmems + C _ ref). The time constant for charging/discharging is R _ ref _ C _ ref _ Cmems/(C _ ref + C _ mem). Thus, the capacitance of the MEMS actuator can be derived from a measurement of the stable voltage of the reference resistor. For example, to measure the capacitance of the MEMS actuator in FIG. 13, where each of Cmes 1-C _ MEMS6 can vary from about 200pf to 500pf (including parasitic capacitance) with 1pf accuracy, the required resolution is 1.3 mV. Therefore, an 11-bit 2V ADC is sufficient. The capacitance of the MEMS actuator can also be obtained by measuring the time constant. To obtain 1pf accuracy over the full range, a system clock of about 72MHz will be utilized. As yet another alternative, the capacitance of the MEMS actuator may be determined by sampling the voltage and then fitting the data to determine a charge time constant or infer a stable voltage without waiting for the voltage to stabilize.

It should be noted that in the context of OIS, to compensate for 20Hz handshaking for example, it may be required to be within 25ms for the full stroke of the three actuators. According to the above example, the time constant would be about 50 μ s. If the actuator is charged for 0.25ms and discharged for 0.25ms, then about 0.5ms would be required in order to measure the capacitance for a single time (although this measurement time could be shortened based on fine tuning certain parameters). To drive the actuator, T _ charge may be lengthened or shortened relative to T _ discharge by some desired period of time, wherein measuring the capacitance of the actuator also includes driving the actuator. To obtain an accuracy level of e.g. 0.5 μm, the control of T _ charge and T _ discharge would require a resolution of 0.25 μ s. As will be appreciated by those skilled in the art, this circuit can be modified in many ways, including reducing the resistance and capacitance of the differentiator and increasing the current to measure the capacitance more quickly, and replacing the passive RC differentiator with an active circuit.

FIG. 14 illustrates a chipset/computing module 90 in which implementations of the techniques disclosed herein may be implemented. Chipset 90 may include, for example, a processor, memory, other image components incorporated in one or more physical packages. By way of example, a physical package includes an arrangement of one or more materials, components, and/or wires on a structural assembly (e.g., a baseboard) to provide one or more characteristics, such as physical strength, dimensional retention, and/or limitations of electrical interaction.

In one embodiment, chipset 90 includes a communication mechanism, such as a bus 92, for passing information among the components of chipset 90. A processor 94, such as an image processor, is connected to bus 92 for executing instructions and processing information stored in a memory 96. A processor may include one or more processing cores, where each core is configured to execute separately. Alternatively or in addition, the processor may include one or more microprocessors configured in series via bus 92 to enable independent execution of instructions, pipeline passing, and multithreading. The processor 94 may also be accompanied by one or more special purpose components to perform certain processing functions and tasks, such as one or more digital signal processors, e.g., DSPs 98, such as OIS DSPs, image sensors, OIS gyroscopes, and/or one or more application specific Integrated Circuits (ICs) (ASICs) 100, such as may be utilized to drive, for example, MEMS actuators for implementing OIS, zoom and/or AF functions. The DSP 98 may generally be configured to process real-world signals (e.g., sounds) in real-time independent of the processor 94. Similarly, ASIC 100 may be configured to perform special-purpose functions not readily performed by general-purpose processors. Other specialized components to help perform the inventive functions described herein include one or more Field Programmable Gate Arrays (FPGAs) (not shown), one or more controllers (not shown), or one or more other specialized computer chips.

The aforementioned components are connected to a memory 96 via a bus 92. The memory 96 includes both dynamic memory (e.g., RAM) and static memory (e.g., ROM) for storing executable instructions that, when executed by the processor 94, DSP 98 and/or ASIC 100, perform the processes of the exemplary embodiments described herein. The memory 96 also stores data associated with or generated by the execution of the process.

As used herein, the term module may describe a given unit of functionality that may be performed in accordance with one or more embodiments of the present application. As used herein, a module may be implemented using any form of hardware, software, or a combination thereof. For example, one or more processors, controllers, ASICs, PLAs, PALs, CPLDs, FPGAs, logic elements, software programs, or other mechanisms may be implemented as component modules. In implementations, the various modules described herein may be implemented as discrete modules or the functions and features described may be partially or fully shared among one or more modules. In other words, after reading this specification, the various features and functions described herein may be implemented in any given application and may be implemented in different combinations and permutations in one or more separate or shared modules, as will be apparent to those of ordinary skill in the art. Even though various features or elements of the functionality may be described separately or as separate modules, those of ordinary skill in the art will appreciate that such features and functionality may be shared among one or more general purpose software and hardware elements, and that separate hardware or software components are not required or implied by the specification to implement such features or functionality.

Where components or modules of an application are implemented in whole or in part using software, in one embodiment, these software elements may be implemented to operate with computing or processing modules capable of performing the functions described herein. One such exemplary computing module is shown in FIG. 10. Various embodiments are described in terms of this exemplary computing module 90. After reading this description, it will become apparent to a person skilled in the relevant art how to implement the application for execution using other computing modules and/or architectures.

In this document, the terms "computer program medium" and "computer usable medium" are used to generally refer to volatile or nonvolatile media, such as memory 96, or other memory/storage units. These and other various forms of computer program media or computer usable media may be involved in carrying out one or more sequences of one or more instructions to a processing device for execution. Such instructions embodied on the medium are often referred to as "computer program code" or "computer program product" (which may be combined in the form of a computer program or other package). When executed, such instructions may enable computing module 90 to perform the features or functions of the present application, as discussed herein.

While various embodiments of the disclosed method and apparatus have been described above, it should be understood that they have been presented by way of example only, and not limitation. Also, the various diagrams may describe example structures or other configurations for the disclosed methods and apparatus, which facilitate understanding of features and functions that may be included in the disclosed methods and apparatus. The disclosed methods and apparatus are not limited to the exemplary constructions or configurations shown, but may be implemented using various alternative constructions and configurations to achieve the desired features. Indeed, it will be apparent to those skilled in the art how alternative functional, logical or physical partitions and configurations can be implemented to perform the desired features of the disclosed methods and apparatus. In addition, many different constituent module names other than those described herein may be applied to the respective sections. Further, with regard to flow diagrams, operational illustrations, and method claims, the order in which the steps are presented herein shall not require that the various embodiments be implemented to perform the recited functions in the same order, unless otherwise indicated by the context.

While the disclosed methods and apparatus have been described above in terms of various exemplary embodiments and implementations, it will be appreciated that the various features, aspects, and functions described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead can be applied, alone or in various combinations, to one or more of the other embodiments of the disclosed methods and apparatus, whether or not such embodiments are described and whether or not such features are presented as being a part of a described embodiment. Thus, the breadth and scope of the claimed invention should not be limited by any of the above-described exemplary embodiments.

The terms and phrases used herein, and variations thereof, unless otherwise expressly stated, should be construed as open-ended as opposed to limiting. As in the above example: the term "comprising" should be interpreted as meaning "including, but not limited to,"; the term "instance" is used to provide an illustrative example of an item in discussion, not a complete or limited list thereof; the terms "a" or "an" should be interpreted to mean "at least one," "one or more," and the like; and adjectives such as "conventional," "traditional," "normal," "standard," "known," and terms of similar meaning should not be construed as limiting the item described to a particular time period or to an item available as of a particular time, but instead should be read to encompass conventional, traditional, normal, or standard technologies available as of any time now or in the future. Also, in this context is meant to be a technology that would be clearly visible or known to one of ordinary skill in the art, including technology that would be clearly visible or known to one of ordinary skill now or at any time in the future.

A group of items linked with the conjunction "and" should not be read as requiring that each and every one of those items be present in the grouping, but rather should be read as "and/or" unless expressly stated otherwise. Similarly, a group of items linked with the conjunction "or" should not be read as requiring mutual exclusivity among that group, but rather should be read as "and/or" unless expressly stated otherwise. Furthermore, although items, elements or components of the disclosed methods and apparatus may be described or claimed in the singular, the plural is contemplated to be within the scope thereof unless limitation to the singular is explicitly stated.

In some instances, the presence of expansion words and phrases such as "one or more," "at least," "but not limited to," or other like phrases is not to be construed as implying that a more limited number of instances is desired or required in instances where such expansion phrases are not present. The use of the term "module" does not imply that all of the components or functions described or claimed in a portion of the module are configured in a common package. Indeed, any or all of the various components of a module, control logic or other components, may be combined in a single enclosure or maintained separately and may further be distributed in multiple groupings or enclosures or across multiple locations.

Furthermore, various embodiments set forth herein are described in terms of exemplary block diagrams, flow charts and other schematic diagrams. After reading this document, the illustrated embodiments and various alternatives thereof may be implemented without limitation to the illustrated examples, as will become apparent to those of ordinary skill in the art. For example, block diagrams and their complementary descriptions should not be construed as requiring a particular architecture or configuration.