Patent ID: 7518285
Filing Date: 2009-04-14
Classification: H02N

Abstract:
1. A starting-process controller for starting a piezomotor, comprising: a voltage-controlled oscillator (VCO), a power output stage, a resonance converter, a phase comparator, a phase-locked loop filter and an adjustable time-delay element, wherein the VCO generates the control signals required for the power output stage, the power output stage provides stepped output voltage, the resonance converter converts the stepped output voltage from the power output stage into a motor voltage for driving the piezomotor, the motor voltage being sinusoidal and having an associated motor current when the piezomotor is driven, the phase comparator compares the motor current with the phase of the motor voltage, and provides a phase-difference signal representing a measure of the phase difference between motor current and the motor voltage, the phase-locked loop filter is configured to smooth the phase-difference signal so as to provide a smoothed signal that controls the VCO, and the adjustable time-delay element providing for controlled reduction of the phase difference between the motor voltage and the motor current in a start-up process for starting up the piezomotor from a large starting angle at initiation of the start-up process towards a smaller operating angle at an operating point, the adjustable time-delay element effecting the reduction in the form of one of: (i) a preset linear gradient, the linear gradient having a preset starting delay, a preset final delay and a preset, fixed change in delay per selected time increment over the duration of the start-up process, such that, at initiation of the start-up process, the starting delay applies to generate a start-up phase angle toward enabling reliable start up of the piezomotor and, at the operating point, the final delay applies to generate an operating phase angle toward enabling reliable operation of the piezornotor, or (ii) a preset progressive curve, the progressive curve having a preset starting delay, a preset final delay and a preset, varying change in delay per selected time increment over the duration of the start-up process, such that, at initiation of the start-up process, the starting delay applies to generate a start-up phase angle toward enabling reliable start up of the piezomotor, and, as the operating point is neared, the change in delay per selected time increment becomes progressively smaller and, at the operating point, the final delay applies to generate an operating phase angle toward enabling reliable operation of the piezomotor, or (iii) a preset combination of a linear gradient and a progressive curve, wherein an output of the adjustable time-delay element is directly connected to an input of the phase comparator.