An angular velocity sensor, comprising:
- a piezoelectric vibrator having first and second drive electrodes, and first and second dejection electrodes, for outputting a drive current from the first drive electrode by exciting a vibration in a specific direction if an AC drive voltage is applied to the second drive electrode, and for outputting Coriolis output detection currents from the first and second detection electrodes if an angular velocity is applied from outside, by detecting an electric charge depending on the angular velocity by the first and second detection electrodes;
- a temperature compensation function generating section for generating a temperature compensation function having an opposite temperature coefficient for compensating an oscillation characteristic and a detection characteristic of the piezoelectric vibrator;
- a correction coefficient setting section for setting a correction coefficient for correcting a production unevenness of a device configuration;
- an oscillator section for creating a temperature compensated voltage provided by converting the drive current to a voltage, and for supplying to the second drive electrode by creating the AC drive voltage from the temperature compensated voltage;
- a synchronous pulse forming section for amplifying the temperature compensated voltage based on the correction coefficient and then performing a phase adjustment, and for creating and outputting a synchronous pulse for a synchronous detection;
- and
- a Coriolis output detection section for performing the synchronous detection of the Coriolis output detection currents based on the synchronous pulse, and for creating and outputting a DC detecting signal depending on the angular velocity;
- wherein the oscillator section includes:
- a first current/voltage converter circuit for converting the drive current to a voltage, and for outputting a conversion drive voltage;
- a first temperature compensation circuit for creating and outputting the temperature compensated voltage by performing a temperature compensation of the conversion drive voltage based on the temperature compensation function;
- a startup detection circuit for outputting a startup detecting signal, based on the AC drive voltage by detecting a startup state of the piezoelectric vibrator;
- a gain switching circuit for switching a gain large at the startup of oscillation, and for switching a gain so that a loop gain of the oscillator section enters an appropriate range at a steady-state oscillation, to the temperature compensated voltage and based on the startup detecting signal;
- a frequency bandwidth-limiting section for limiting a frequency bandwidth of an output voltage of the gain switching circuit, and for amplifying at an amplification degree that depends on the correction coefficient;
- and
- an automatic gain control section for calculating an error difference between an amplitude value of the AC drive voltage and a pre-determined amplitude value after finishing the startup of the piezoelectric vibrator, for controlling a gain of an output voltage of the frequency bandwidth-limiting section so that the error difference is zero, and for maintaining the amplitude value of the AC drive voltage constant;
- and wherein the Coriolis output detection section includes:
- a second current/voltage converter circuit for converting to a voltage the Coriolis output detection current output from the first detection electrode, and for outputting a first detection voltage;
- a third current/voltage converter circuit for converting to a voltage the Coriolis output detection current output from the second detection electrode, and for outputting a second detection voltage;
- a first voltage adjustment circuit for adjusting an amplitude and a phase of a common-mode component of the first detection voltage, based on the correction coefficient;
- a second voltage adjustment circuit for adjusting an amplitude and a phase of a common-mode component of the second detection voltage, based on the correction coefficient;
- a differential amplifier circuit for performing a differential amplification of output voltages of the first and second voltage adjustment circuits, for removing a common-mode component, and for extracting a Coriolis component which is a reversed-mode component;
- a second temperature compensation circuit for limiting a frequency bandwidth of an output voltage of the differential amplifier circuit, and for performing a temperature compensation based on the temperature compensation function;
- a detection section for detecting a direction and a magnitude of the Coriolis force, for limiting a frequency bandwidth by performing a synchronous detection of an output voltage of the second temperature compensation circuit based on the synchronous pulse, and for outputting a DC detection voltage by extracting a DC component;
- an adjustment compensation circuit for performing a sensitivity setting of the DC detection voltage based on the correction coefficient, and for performing a temperature compensation of the sensitivity being set based on the temperature compensation function;
- and
- an offset adjustment circuit for performing a zero point drift temperature compensation of an output voltage of the adjustment compensation circuit based on the temperature compensation function, and for outputting the DC detecting signal.