Patent ID: 8796903

Claim:
A piezoelectric vibrator driving circuit for driving a piezoelectric vibrator, the piezoelectric vibrator having an equivalent circuit in which an LC series resonance circuit formed by an equivalent capacitor Cx and an equivalent inductor Lx connected in series, an equivalent resistor Rx connected in series to the LC series resonance circuit and a damping capacitor Co connected in parallel to the LC series resonance circuit and the equivalent resistor Rx are provided, the driving circuit comprising: a self-excited oscillation type oscillation circuit section configured to oscillate, an oscillation frequency thereof being variable; a driving pulse generator configured to generate a driving pulse in synchronization with the oscillation frequency; art output driver configured to output a driving voltage Ve to be applied on the piezoelectric vibrator, based on the driving pulse; a driving current phase detector configured to detect a driving current Iz flowing through the entire piezoelectric vibrator; a damping current phase detector configured to detect a damping current Iy flowing through the damping capacitor Co; a series resonance current calculator configured to subtract the detected damping current Iy from the detected driving current Iz to thereby calculate a series resonance current Ix flowing through the LC series resonance circuit; a synchronization section configured to synchronize the oscillation frequency of the oscillation circuit section with a frequency of the calculated series resonance current Ix; and a phase shift circuit section inserted into any point of a signal path leading from an output terminal of the driving current phase detector or the damping current phase detector to an input terminal of the output driver, and configured to perform a phase adjustment so that a phase difference between the calculated series resonance current Ix and the driving voltage Ve becomes approximately 0.