An integrated switching current-mode sigma-delta power stage for hard disk drives

An integrated current-mode switching power stage for hard-disk drive voice-coil motors is presented. In this system the current in the voice-coil is directly regulated by a sigma-delta modulator. Given its nature, the sigma-delta modulator does not need an external control loop and a single loop system is thereby obtained. The output stage employs an H-bridge and uses the zero voltage transition commutation technique to control the slope of the output voltage. Output voltage slope control is a basic application requirement to prevent interference with the hard disk drive´s signal circuitry. Preliminary experimental results on a prototype are presented. The system showed it could work with an output slope of up to 500 V/μs with no significant performance losses.