Starting-process controller for starting a piezomotor

Abstract

A starting-process controller for starting a piezomotor, having a voltage-controlled oscillator, a power output stage, and a resonant converter. The oscillator generates the control signals required for the power output stage and the resonance converter converts the stepped output voltage from the power output stage into a sinusoidal voltage at the output. The resonance converter drives the piezomotor with the voltage. The motor current that flows when the piezomotor is driven is measured and compared with the phase of the drive voltage in a phase comparator. The comparison output signal is a measure of the phase difference at the time between current and voltage. A phase-locked loop filter smoothes the phase-difference signal for controling the oscillator. The controller includes a start-assisting circuit element that fixes the output voltage from the phase-locked loop filter at start-up and thus applies a constant voltage to the input of the voltage-controlled oscillator.

1 . A starting-process controller for starting a piezomotor, the starting-process controller comprising:
 a voltage-controlled oscillator, a power output stage, and a resonance converter and an adjustable time-delay element, wherein   the oscillator generates the control signals required for the power output stage,   the resonance converter converts the stepped output voltage from the power output stage into a sinusoidal voltage at its output,   the piezomotor is driven by the sinusoidal voltage from the resonance converter,   wherein motor current that flows when the piezomotor is driven is measured and compared with the phase of the drive voltage in a phase comparators,   an output signal from the phase comparator is a measure for a phase difference signal at the time between current and voltage,   a phase-locked loop filter smoothes the phase-difference signal,   the smoothed signal controls the oscillator, and   a start-assisting circuit element fixes an output voltage from the phase-locked loop filter at start-up and thus applies a constant voltage to an input of the voltage-controlled oscillator, wherein an output of the adjustable time-delay element is directly connected to an input of the phase comparator.   
   
   
       2 . The starting-process controller as claimed in  claim 1 , wherein the start-assisting element comprises a switching element, a voltage source, and a resistor, which are switchable into parallel with the loop filter. 
   
   
       3 . The starting-process controller as claimed in  claim 2 , wherein the resistor is connected in series with the voltage source. 
   
   
       4 . The starting-process controller as claimed in  claim 2 , wherein the switching element switches a resistor into parallel with the loop filter. 
   
   
       5 . The starting-process controller as claimed in  claim 1 , wherein the length in time of a signal for activating the switching element is set to a fixed duration from the beginning of start-up. 
   
   
       6 . The starting-process controller as claimed in  claim 1 , wherein an activating signal causes the motor to break away. 
   
   
       7 . The starting-process controller as claimed in  claim 1 , wherein an activating signal is triggered by power-on of the starting-process controller. 
   
   
       8 . The starting-process controller as claimed in  claim 1 , wherein an activating signal is generated by a digital counter or a state machine. 
   
   
       9 . The starting-process controller as claimed in  claim 1 , wherein an activating signal is generated by a digital processor. 
   
   
       10 - 22 . (canceled)