| 摘要 |
PURPOSE:To always obtain a stable actions by executing the driving of a piezoelectric element in a separate excitation system, detecting the resonance point of the piezoelectric element from the waveform of a driving voltage and controlling the feedback of a driving frequency according to the detected result. CONSTITUTION:An output from a voltage controlled sine wave oscillator 1 is shaped 2 to a driving pulse PL so as to drive the piezoelectric element 5. A voltage comparator 6 compares the output from an emitter follower circuit 4, that means the driving voltage VL of the piezoelectric element 5, with a reference voltage VTM and detects the stop period of the driving current IL of the piezoelectric element 5. A frequency control circuit 7 detects the error between the driving period of the driving pulse PL and the resonance period of the piezoelectric element 5 from a timing relation between the output pulse PE of the voltage comparator 6 and the driving pulse PL and converts it into a control voltage VC. Thus the stable actions can be always obtained without being influenced by the wiring between the piezoelectric element and the driving circuit.
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