DETECTOR, PHYSICAL QUANTITY MEASURING DEVICE, AND ELECTRONIC APPARATUS

• US 20110062941A1
• Filed: 08/24/2010
• Published: 03/17/2011
• Est. Priority Date: 09/11/2009
• Status: Active Grant

• Current Assignee: Seiko Epson Corporation (Seiko Group)
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: YOSHIDA, Naoki
• Granted Patent: US 8,593,130 B2
• Time in Patent Office: Days
• US Class Current: 324/71.1
• CPC Class Codes: G01H 11/08 using piezoelectric devices

Abstract

A detector is provided that detects a detection signal corresponding to a driving vibration, which excites a vibrator in an oscillation loop, and a physical quantity to be measured. The detector includes an amplifying circuit, a synchronous detection circuit, an impedance conversion circuit, a first low pass filter, and a second low pass filter, wherein each of the first and second low pass filters is formed by a switched capacitor filter circuit, a gain of the first low pass filter is different from that of the second low pass filter.

Claims

1. A detector that detects a detection signal corresponding to a driving vibration, which excites a vibrator in an oscillation loop, and a physical quantity to be measured, the detector comprising:

an amplifying circuit that amplifies a signal corresponding to the driving vibration and the physical quantity;

a synchronous detection circuit that detects the amplified signal of the amplifying circuit in synchronization with an oscillation signal in the oscillation loop;

an impedance conversion circuit that converts an output impedance of the synchronous detection circuit;

a first low pass filter to which an output signal of the impedance conversion circuit is supplied and which outputs a first detection signal; and

a second low pass filter to which the output signal of the impedance conversion circuit is supplied and which outputs a second detection signal,

wherein each of the first and second low pass filters is formed by a switched capacitor filter circuit, and

a gain of the first low pass filter is different from that of the second low pass filter.

2. The detector according to claim 1,

wherein each of the first and second low pass filters includes:

a first integrator formed by a switched capacitor circuit having a first operational amplifier;

a second integrator which is formed by a switched capacitor circuit having a second operational amplifier and which is connected to an output end of the first integrator;

a feedback capacitor circuit having a third feedback capacitor inserted between an output end of the second integrator and a virtual ground end of the first operational amplifier; and

a fourth feedback capacitor connected in parallel to the feedback capacitor circuit,

the first integrator includes;

a first input capacitor circuit connected between an output end of the impedance conversion circuit and the virtual ground end of the first operational amplifier; and

a first feedback capacitor connected between an output end of the first operational amplifier and the virtual ground end of the first operational amplifier, and

the first integrator inputs a voltage difference between the output end of the impedance conversion circuit and the virtual ground end of the first operational amplifier and some charges, which are stored by a plurality of capacitors of the first integrator, to the virtual ground end of the first operational amplifier through a switch, and changes an output potential of the first operational amplifier using the first feedback capacitor, and

the second integrator includes;

a second input capacitor circuit connected between the output end of the first operational amplifier and a virtual ground end of the second operational amplifier; and

a second feedback capacitor connected between an output end of the second operational amplifier and the virtual ground end of the second operational amplifier, and

the second integrator inputs a voltage difference between the output end of the first operational amplifier and the virtual ground end of the second operational amplifier and some charges, which are stored by a plurality of capacitors of the second integrator, to the virtual ground end of the second operational amplifier through a switch, and changes an output potential of the second operational amplifier using the second feedback capacitor.

3. The detector according to claim 1,

wherein a first input capacitor circuit which has a first input capacitor and a second input capacitor, which is set to have the same capacitance value as the first input capacitor, and to which the output signal of the impedance conversion circuit is supplied;

a first operational amplifier which amplifies a signal corresponding to the amount of electric charge charged in the first input capacitor circuit;

a first integrator having a first feedback capacitor inserted between a virtual ground end and an output end of the first operational amplifier;

a second input capacitor circuit which has a third input capacitor and a fourth input capacitor, which is set to have the same capacitance value as the third input capacitor, and which is connected to the output end of the first operational amplifier;

a second operational amplifier which amplifies a signal corresponding to the amount of electric charge charged in the second input capacitor circuit;

a second integrator having a second feedback capacitor inserted between a virtual ground end and an output end of the second operational amplifier;

a feedback capacitor circuit having a third feedback capacitor which is formed so as to be able to be inserted between an output end of the second integrator and the virtual ground end of the first operational amplifier; and

a fourth feedback capacitor connected in parallel to the feedback capacitor circuit,

the first input capacitor circuit transfers electric charge, which is charged in the second input capacitor in synchronization with a second clock with a phase opposite to a phase of a first clock, to the first input capacitor in synchronization with the first clock and transfers electric charge, which is charged in the first input capacitor, to the first feedback capacitor in synchronization with the second clock,

the second input capacitor circuit transfers electric charge, which is charged in the fourth input capacitor in synchronization with the first clock, to the third input capacitor in synchronization with the second clock and transfers electric charge, which is charged in the third input capacitor, to the second feedback capacitor in synchronization with the first clock, and,

the feedback capacitor circuit is inserted between the output end of the second integrator and the virtual ground end of the first operational amplifier in synchronization with the first clock, and discharges electric charge, which is charged in the third feedback capacitor, in synchronization with the second clock.

4. The detector according to claim 3,

wherein the first input capacitor circuit includes:

a first switch inserted between a signal input node, to which the output signal of the impedance conversion circuit is supplied, and one end of the first input capacitor;

a second switch inserted between the one end of the first input capacitor and a reference potential;

a third switch inserted between the signal input node and one end of the second input capacitor;

a fourth switch inserted between the one end of the second input capacitor and the reference potential;

a fifth switch inserted between the other end of the second input capacitor and the reference potential;

a sixth switch inserted between the other end of the second input capacitor and the other end of the first input capacitor; and

a seventh switch inserted between the other end of the first input capacitor and the virtual ground end of the first operational amplifier,

the second input capacitor circuit includes;

an eighth switch inserted between a connection node, to which the output of the first operational amplifier is supplied, and one end of the third input capacitor;

a ninth switch inserted between the one end of the third input capacitor and the reference potential;

a tenth switch inserted between the connection node and one end of the fourth input capacitor;

an eleventh switch inserted between the one end of the fourth input capacitor and the reference potential;

a twelfth switch inserted between the other end of the fourth input capacitor and the reference potential;

a thirteenth switch inserted between the other end of the fourth input capacitor and the other end of the third input capacitor; and

a fourteenth switch inserted between the other end of the third input capacitor and the virtual ground end of the second operational amplifier, and

the feedback capacitor circuit includes;

a fifteenth switch inserted between the virtual ground end of the first operational amplifier and one end of the third feedback capacitor;

a sixteenth switch inserted between the one end of the third feedback capacitor and the reference potential;

a seventeenth switch inserted between the other end of the third feedback capacitor and the reference potential; and

an eighteenth switch inserted between the other end of the third feedback capacitor and the output end of the second operational amplifier.

5. The detector according to claim 4,

wherein each of the first, fourth, sixth, ninth, tenth, twelfth, fourteenth, fifteenth, and eighteenth switches is switching-controlled by the first clock, and

each of the second, third, fifth, seventh, eighth, eleventh, thirteenth, sixteenth, and seventeenth switches is switching-controlled by the second clock.

6. The detector according to claim 3,

wherein shapes and areas of the third and fourth input capacitors and the third feedback capacitor are set to be equal, and the third and fourth input capacitors and the third feedback capacitor are manufactured through a common manufacturing process.

7. The detector according to claim 3,

wherein the ratio of a capacitance value of the first input capacitor and a capacitance value of the third feedback capacitor in the first low pass filter is set to be different from the ratio of a capacitance value of the first input capacitor and a capacitance value of the third feedback capacitor in the second low pass filter.

8. The detector according to claim 7,

wherein the capacitance value of the third feedback capacitor in the first low pass filter is set to be equal to the capacitance value of the third feedback capacitor in the second low pass filter, and

the capacitance value of the first input capacitor in the first low pass filter is different from the capacitance value of the first input capacitor in the second low pass filter.

9. The detector according to claim 8,

wherein in the first and second low pass filters, shapes and areas of elements which form each low pass filter are set to be equal except for the capacitance values of the first and second input capacitors in each low pass filter.

10. The detector according to claim 3,

wherein assuming that a frequency of each of the first and second clocks is T, a Q factor of the first low pass filter is Q, a capacitance value of the third feedback capacitor is 1, and ω

is a cut-off frequency on the s plane, a capacitance value D of the first feedback capacitor and a capacitance value B of the second feedback capacitor have relationship expressed as follows,

11. The detector according to claim 3,

wherein each of the first and second clocks in the first low pass filter has the same phase and frequency as each of the first and second clocks in the second low pass filter.

12. The detector according to claim 1,

wherein the physical quantity is angular velocity.

13. A physical quantity measuring device comprising:

a driving circuit which forms an oscillation loop together with a vibrator and excites the vibrator to perform a driving vibration; and

the detector according to claim 1,

wherein the driving circuit outputs a reference signal, which is obtained by binarizing the oscillation signal, to the detector, and

the synchronous detection circuit detects the amplified signal in synchronization with the reference signal.

14. An electronic apparatus comprising the detector according to claim 1.

15. An electronic apparatus comprising the physical quantity measuring device according to claim 13.