Patent ID: 7385362

Claim:
A method for driving a vibrating device for a portable object, the device comprising a moving mass and a coil electromagnetically coupled to the moving mass in order to make said mass oscillate, wherein, in a phase of driving the periodic oscillations of the moving mass, the method comprises providing successive rectangular voltage pulses of alternating polarity to the coil without interruption between pulses using a drive circuit connected to terminals of the vibrating device coil, the width of the successive pulses being modulated in a substantially similar manner during each successive oscillation period in order to define a substantially sinusoidal or pseudo-sinusoidal voltage wave of determined amplitude whose fundamental frequency is adapted to the resonant frequency of the moving mass in order to remove the fundamental frequency harmonics, and wherein the successive rectangular voltage pulses of alternating polarity are arranged to have even symmetry in each oscillation half period in relation to a middle point of the half period, and uneven symmetry in each oscillation period in relation to a middle point of the oscillation period.