Piezoelectric vibrator driving circuit

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 PLL circuit section having a phase comparator and a VCO;
• a driving pulse generator configured to generate a driving pulse based on an output of the PLL circuit section;
• an 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 clamping current Iy from the detected driving current Iz to thereby calculate a series resonance current Ix flowing through the LC series resonance circuit;
• and
• a driving voltage phase detector configured to detect the driving voltage Ve applied to the piezoelectric vibrator,
• wherein the phase comparator of the PLL circuit section includes one input terminal to which an output of the series resonance current calculator is input and the other input terminal to which an output of the driving voltage phase detector is input, and the PLL circuit section performs a phase adjustment so that a phase difference between inputs to the both input terminals becomes approximately 0.

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, illation frequency thereof being variable;
• a driving pulse generator configured to generate a driving pulse in synchronization with the oscillation frequency;
• an 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;
• and
• 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 though the LC series resonance circuit,
• wherein an output of the driving current phase detector or the series resonance current calculator is fed back to the oscillation circuit section, and a phase adjustment is performed so that a phase difference between the output of the driving current phase detector or the series resonance current calculator and the driving voltage Ve becomes approximately 0, and
• wherein there is further provided a series resonance current detector configured to detect an amplitude of the output of the series resonance current calculator, and a width of the driving pulse is controlled so that an output of the series resonance current detector becomes constant.

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;
• an 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,
• wherein an output of the driving current phase detector is fed back to the oscillation circuit section, and the oscillation frequency of the oscillation circuit section is synchronized with a vibration frequency of the piezoelectric vibrator, and
• wherein there is further provided a phase shift circuit section inserted into any point of a signal path leading from an output terminal of the driving 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 detected driving current Iz or a calculated series resonance current Ix flowing through the LC series resonance circuit and the driving voltage Ve becomes approximately 0.