OSCILLATION TYPE INERTIA FORCE SENSOR

• US 20130192366A1
• Filed: 08/08/2012
• Published: 08/01/2013
• Est. Priority Date: 02/17/2010
• Status: Active Grant

• Current Assignee: Asahi Kasei Microdevices Corporation (Asahi Kasei Corporation), Murata Manufacturing Co Limited
• Original Assignee: Asahi Kasei Microdevices Corporation (Asahi Kasei Corporation), Murata Manufacturing Co Limited
• Inventors: KATO, Yoshitaka, MORI, Akira, NARITA, Makoto
• Granted Patent: US 9,021,879 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/56 Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719

Abstract

An inertia force sensor that shortens a time from power activation until inertia force can be detected includes an oscillator, an oscillation circuit unit, and a detection circuit unit. The oscillation circuit unit functions as a closed loop self oscillation circuit with the oscillator as a resonant element, and includes a CV conversion circuit converting a monitor signal based on electrostatic capacitance according to an oscillating state of oscillator into a monitor signal based on a voltage corresponding to an amount in change of the electrostatic capacitance, and an automatic gain control circuit controlling gain based on the monitor signal converted at the CV conversion circuit to generate a driving signal, and supplying the driving signal to the oscillator. The CV conversion circuit includes an amplifier that amplifies a monitor signal with an amplification factor for a predetermined period after power activation.

Claims

1. An oscillation type inertia force sensor comprising:

an oscillator that is used to detect inertia force;

an oscillation circuit unit that supplies a driving signal to the oscillator; and

a detection circuit unit that detects inertia force of the oscillator;

wherein

the oscillation circuit unit is a self oscillation circuit of a closed loop with the oscillator defining a resonant element, and the oscillation circuit includes;

a signal conversion circuit that converts a monitor signal based on electrostatic capacitance according to an oscillating state of the oscillator into a monitor signal based on a voltage corresponding to an amount of change of the electrostatic capacitance; and

an automatic gain control circuit that controls gain based on the monitor signal converted at the signal conversion circuit to generate the driving signal, and that supplies the driving signal to the oscillator;

wherein

the signal conversion circuit includes an amplifier that amplifies the monitor signal with a predetermined amplification factor for a predetermined period after power activation.

2. The oscillation type inertia force sensor according to claim 1, wherein the signal conversion circuit includes an operational amplifier circuit including a feedback capacitor, and the amplifier amplifies a monitor signal by switching a level of the feedback capacitor for the predetermined period after power activation.

3. The oscillation type inertia force sensor according to claim 1, wherein, when an amplification factor of an amplification circuit in the automatic gain control circuit has a negative property to a control signal controlling gain of the automatic gain control circuit, the predetermined period is a period during which the gain based on the control signal becomes less than or equal to a maximum gain of the amplification factor of the amplification circuit in a range where the gain varies corresponding to a change of the control signal after power activation.

4. The oscillation type inertia force sensor according to claim 1, wherein, when an amplification factor of an amplification circuit in the automatic gain control circuit has a positive property to a control signal controlling gain of the automatic gain control circuit, the predetermined period is a period during which the gain based on the control signal becomes greater than or equal to a maximum gain of the amplification factor of the amplification circuit in a range where the gain varies corresponding to a change of the control signal after power activation.

5. The oscillation type inertia force sensor according to claim 2, wherein the amplifier switches a level of the feedback capacitor based on a control signal controlling gain of the automatic gain control circuit.

6. The oscillation type inertia force sensor according to claim 5, wherein

the feedback capacitor includes a first feedback capacitor and a second feedback capacitor;

the first feedback capacitor is constantly connected to the operational amplifier circuit; and

the second feedback capacitor is at least one capacitor connected to the operational amplifier circuit based on the control signal.