PWM-based measurement interface for a micro-machined electrostatic actuator
First Claim
1. A method of varying the position of a micromachined electrostatic actuator using a pulse width modulated (PWM) pulse train, comprising:
- applying one or more voltage pulses to the actuator wherein a voltage changes from a first state to a second state and remains in the second state for a time Δ
tpulse before returning to the first state; and
varying the position of the actuator by varying the time Δ
tpulse.
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Abstract
Methods and apparatus for varying and measuring the position of a micromachined electrostatic actuator using a pulse width modulated (PWM) pulse train are disclosed. One or more voltage pulses are applied to the actuator. In each of the pulses, a voltage changes from a first state to a second state and remains in the second state for a time tpulse before returning to the first state. The position of the actuator may be varied by varying the time Δtpulse. A position of the actuator may be determined by measuring a capacitance of the actuator when the voltage changes state, whether the time t is varied or not. An apparatus for varying the position of a MEMS device may include a pulse width modulation generator coupled to the MEMS device an integrator coupled to the MEMS device and an analog-to-digital converter coupled to the integrator. The integrator may measure a charge transferred during a transition of a pulse from the pulse generator. The integrator may include an amplifier, an integrator capacitor, a hold capacitor, a compensation voltage generator and three switches. The hold capacitor and integrator capacitor may be coupled to a MEMS device. The integrator capacitor, hold capacitor, and compensation voltage generator may be selectively coupled to the amplifier by two of the switches. The MEMS device and hold capacitor may be selectively coupled to ground by a third switch.
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Citations
10 Claims
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1. A method of varying the position of a micromachined electrostatic actuator using a pulse width modulated (PWM) pulse train, comprising:
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applying one or more voltage pulses to the actuator wherein a voltage changes from a first state to a second state and remains in the second state for a time Δ
tpulse before returning to the first state; and
varying the position of the actuator by varying the time Δ
tpulse.- View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for varying the position of a MEMS device, comprising:
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a pulse width modulation generator coupled to the MEMS device an integrator coupled to the MEMS device and an analog-to-digital converter coupled to the integrator. - View Dependent Claims (9, 10)
an amplifier, having at least one input and an output, an integrator capacitor coupled to the MEMS device, a hold capacitor, a compensation voltage generator, and first, second and third switches, wherein the hold capacitor is coupled to the MEMS device, wherein the hold capacitor is coupled to the input of the amplifier wherein the first switch selectively couples the hold capacitor to the compensation voltage generator or the output of the amplifier, wherein the second switch selectively couples input of the amplifier to the output of the amplifier, wherein the third switch selectively couples MEMS device and the hold capacitor to ground.
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Specification