OSCILLATION TYPE INERTIA FORCE SENSOR

• US 20120291550A1
• Filed: 08/08/2012
• Published: 11/22/2012
• 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, KOIZUMI, Yoshihiko
• Granted Patent: US 9,003,884 B2
• Time in Patent Office: Days
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5776 Signal processing not specific to any of the devices covered by groups G01C19/5607 - G01C19/5719

Abstract

An oscillation type inertia force sensor includes an oscillator, an oscillation circuit unit, and a detection circuit unit. The oscillation circuit unit functions as a self oscillation circuit of a closed loop with the oscillator as a resonant element, and includes an AGC circuit. The AGC circuit includes a VGA circuit, a comparison circuit comparing a predetermined reference voltage with a voltage of the monitor signal to output a control signal based on the compared result, and a pulse width modulation circuit modulating the control signal to a pulse width modulation signal. Based on the pulse width modulation signal, the driving signal is modulated with the output of the VGA circuit switched between an ON state and OFF state to control the degree of the amplification factor of the VGA circuit.

Claims

1. An oscillation type inertia force sensor comprising:

an oscillator 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 includes an automatic gain control circuit that amplifies a monitor signal according to an oscillating state of the oscillator to generate and supply to the oscillator the driving signal;

the automatic gain control circuit includes;

an amplification circuit that amplifies the monitor signal;

a comparison circuit that compares a predetermined reference voltage with a voltage of the monitor signal to output a control signal to control a degree of an amplification factor of the amplification circuit based on a compared result; and

a pulse width modulation circuit that modulates the control signal output from the comparison circuit into a pulse width modulation signal having a frequency higher than the frequency of the monitor signal;

wherein

based on the pulse width modulation signal modulated at the pulse width modulation circuit, the driving signal is modulated with an output of the amplification circuit switched between an ON state and OFF state to control the degree of the amplification factor of the amplification circuit.

2. The oscillation type inertia force sensor according to claim 1, further comprising a demodulation circuit at a succeeding stage of the amplification circuit to demodulate the driving signal modulated with the output of the amplification circuit switched between an ON state and an OFF state based on the pulse width modulation signal.

3. The oscillation type inertia force sensor according to claim 1, wherein, when the comparison circuit amplifies a difference between a predetermined reference voltage and a voltage of the monitor signal with a predetermined amplification factor of a control signal to output the control signal, an absolute value of a slope of the amplification factor of the amplification circuit to a ratio between a voltage of the monitor signal and a predetermined reference voltage is less than or equal to about 320 dB.