Physical quantity measuring apparatus and electronic device

• US 8,186,218 B2
• Filed: 02/27/2009
• Issued: 05/29/2012
• Est. Priority Date: 02/29/2008
• Status: Active Grant

• Current Assignee: 138 East LCD Advancements Limited (Vector Capital Corporation)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Nozawa, Toshiyuki
• Primary Examiner(s): Kwok, Helen C.
• Application Number:
  US12/395,359
• Publication Number:
  US 20090217757A1
• Time in Patent Office: 1,187 Days
• Field of Search: 735/041.2, 735/040.4, 735/040.2, 735/041.4, 735/041.5, 735/041.6
• US Class Current: 73/504.12
• CPC Class Codes: G01C 19/5607 using vibrating tuning forks double-ended tuning forks using planar vibrating masses suspended at opposite ends G01C19/5719

Abstract

A physical quantity measuring apparatus includes an oscillation drive circuit that forms an oscillation loop together with a physical quantity transducer and excites a drive oscillation of the physical quantity transducer, and a detection circuit that detects an analog detection signal outputted from the physical quantity transducer using a detection circuit first and then converts the signal that has been detected into a digital signal using an A/D converter to output the digital signal. The oscillation drive circuit has a drive amplitude detection circuit that detects amplitude of the drive oscillation. A voltage level of a reference of the A/D converter included in the detection circuit is controlled on the basis of a detection output signal of the drive amplitude detection circuit.

Claims

1. A physical quantity measuring apparatus, comprising:

an oscillation drive circuit that forms an oscillation loop together with a physical quantity transducer and excites a drive oscillation of the physical quantity transducer; and

a detection circuit that detects an analog detection signal outputted from the physical quantity transducer using a synchronization detection circuit first and thence converts the signal that has been detected into a digital signal using an A/D converter to output the digital signal, wherein;

the oscillation drive circuit has a drive amplitude detection circuit that detects an amplitude of the drive oscillation; and

a voltage level of a reference of the A/D converter included in the detection circuit is controlled on the basis of a detection output signal of the drive amplitude detection circuit.

2. The physical quantity measuring apparatus according to claim 1, wherein:

the voltage level of the reference of the A/D converter is controlled so that a variance width of the A/D converter is proportional to the amplitude of the drive oscillation.

3. The physical quantity measuring apparatus according to claim 1, wherein:

the oscillation drive circuit has an AGC circuit to maintain the amplitude of the drive oscillation constant and the drive amplitude detection circuit is one of circuits that form the AGC circuit.

4. The physical quantity measuring apparatus according to claim 1, wherein:

at least one of the detection output signal of the drive amplitude detection circuit and a signal obtained by inverting a voltage level of the detection output signal is used as the reference of the A/D converter.

5. The physical quantity measuring apparatus according to claim 1, wherein:

given a signal obtained by adjusting a voltage level of the detection output signal of the drive amplitude detection circuit as a first signal and a signal obtained by inverting a voltage level of the first signal as a second signal, then at least one of the first signal and the second signal is used as the reference of the A/D converter.

6. The physical quantity measuring apparatus according to claim 4, wherein:

the detection circuit has an offset adjusting circuit that compensates for an offset voltage superimposed on the detection output signal of the drive amplitude detection circuit.

7. The physical quantity measuring apparatus according to claim 1, wherein the drive amplitude detection circuit has:

a rectifying circuit that rectifies an oscillation signal of the oscillation loop; and

a smoothing circuit that smoothes out an output signal of the rectifying circuit.

8. The physical quantity measuring apparatus according to claim 1, wherein:

the drive amplitude detection circuit is formed of a rectifying and integrating circuit formed by integrating a rectifying circuit that rectifies an oscillation signal of the oscillation loop and an integrating circuit that integrates a rectified signal into one piece.

9. The physical quantity measuring apparatus according to claim 1, wherein:

the oscillation drive circuit has an amplitude limiting circuit that is provided instead of an AGC circuit to maintain the amplitude of the drive oscillation constant in order to limit at least one of an upper limit and a lower limit of the amplitude of the drive oscillation.

10. An electronic device, comprising:

the physical quantity measuring apparatus set forth in claim 1; and

a movable mechanism that operates concurrently with the physical quantity measuring apparatus.

11. The physical quantity measuring apparatus according to claim 1, wherein:

the physical quantity measuring apparatus is a gyrosensor; and

the physical quantity transducer is an oscillatory gyroscope element in which the drive oscillation is excited by the oscillation drive circuit and that generates a detection signal having amplitude corresponding to an angular velocity.

12. An electronic device, comprising:

the physical quantity measuring apparatus set forth in claim 1; and

a movable mechanism,

wherein an operation period of the physical quantity measuring apparatus overlaps an operation period of the movable mechanism.

13. The electronic device according to claim 12, wherein:

the movable mechanism includes a mechanical movable component.

14. The electronic device according to claim 12, wherein:

the movable mechanism is an impact source that generates an impact.

15. The electronic device according to claim 12, wherein:

the movable mechanism is an oscillation source that generates an oscillation.