Patent ID: 6906485

Claim:
A method for commutating a multiphase spindle motor having a plurality of phases, each phase having a high and a low switching element, the high switching elements each connected in series with a voltage source and the low switching elements each connected in series with a sense resistor, the method comprising: detecting a selected commutation state of the spindle motor; initiating a timer to measure a selected elapsed time; applying a desired magnitude of current to the spindle motor during the elapsed time by sourcing current to a first selected phase and sinking current from a second selected phase associated with the selected commutation state, wherein the desired magnitude of current is maintained by providing a commanded current value indicative of the desired current magnitude and applying control signals to the switching elements associated with the first and second selected phases in response to a voltage detected across the sense resistor; deactivating the switching elements associated with the first and second selected phases at the conclusion of the elapsed time so that substantially zero current flows through the spindle motor tapering the current from the desired magnitude to substantially zero current along a noninstantaneous gradient at the conclusion of the elapsed time by providing a sequence of current command values of successively decreased magnitude in accordance with a desired tapered current profile; and repeating the detecting, initiating, applying and deactivating steps for the next detected commutation state.