System for controlling the speed of a voice coil motor (VCM) in order to provide a low noise ramp loading of a hard disk head

摘要

A system controls the speed of a Voice Coil Motor (VCM) in order to perform the ramp loading of hard disk heads with low noise. This system includes a generator for generating a discontinuous PWM drive signal to a power stage. A sampling block is clocked by a synchronization signal issued from the generator and receives as an input a signal related to the electromotive force (Bemf) provided by the VCM motor. An adder node placed at the sampling block output receives a signal related to a reference electromotive force (Bemf_ref). A filtering block placed downstream of the adder node generates a power supply voltage signal to the power stage. The control system further includes a control block having at least one voltage divider and controlled switches. The control block is input the signal issued from the filtering block and control signals from the generator block to selectively operate the controlled switches and set the value of the power-on signal of the power stage.