Variable capacitance device
First Claim
1. A variable capacitance device comprising:
- a fixed plate including a first driving electrode and a first variable capacitance electrode;
a movable plate including a second driving electrode facing the first driving electrode and a second variable capacitance electrode facing the first variable capacitance electrode;
a driving voltage applying unit that applies a driving voltage between the first driving electrode and the second driving electrode;
a reference capacitor having a predetermined capacitance;
a capacitance detection signal generation unit that applies a capacitance detection pulse signal to a driving capacitance portion including the first driving electrode and the second driving electrode and to the reference capacitor; and
a voltage change comparator that compares a voltage change of the driving capacitance portion and a voltage change of the reference capacitor caused by the capacitance detection pulse signal and outputs a comparison result;
whereinthe driving voltage applying unit controls the driving voltage based on the comparison result.
1 Assignment
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Accused Products
Abstract
A variable capacitance device that achieves a desired capacitance even when factors causing varied capacitances are generated is configured such that a capacitance detection pulse signal is applied from a capacitance detection signal generation unit to a driving capacitor and a reference capacitor of a MEMS mechanical unit. The device voltage of the driving capacitor based on the capacitance detection signal and a driving voltage is applied to the inverting input terminal of a comparator. The device voltage of the reference capacitor based on the capacitance detection signal and the driving voltage is applied to the non-inverting input terminal of the comparator. The comparator generates a comparison output signal including “Hi” and “Low” values from the difference between these device voltages, and applies the output signal to a driving voltage generation unit. The driving voltage generation unit increases or decreases the driving voltage based on the comparison output signal.
6 Citations
5 Claims
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1. A variable capacitance device comprising:
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a fixed plate including a first driving electrode and a first variable capacitance electrode; a movable plate including a second driving electrode facing the first driving electrode and a second variable capacitance electrode facing the first variable capacitance electrode; a driving voltage applying unit that applies a driving voltage between the first driving electrode and the second driving electrode; a reference capacitor having a predetermined capacitance; a capacitance detection signal generation unit that applies a capacitance detection pulse signal to a driving capacitance portion including the first driving electrode and the second driving electrode and to the reference capacitor; and a voltage change comparator that compares a voltage change of the driving capacitance portion and a voltage change of the reference capacitor caused by the capacitance detection pulse signal and outputs a comparison result;
whereinthe driving voltage applying unit controls the driving voltage based on the comparison result. - View Dependent Claims (2, 3, 4, 5)
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Specification