Patent ID: 7940020

Claim:
A system for controlling a brushless DC motor, including: a commutation circuit having first and second input terminals for coupling the commutation circuit respectively to a high voltage terminal and a low voltage terminal of a DC power supply; the commutation circuit further having a plurality of output terminals adapted for coupling individually to a plurality of stator windings corresponding to different motor phases of a brushless DC motor to couple the commutation circuit to the DC motor; the commutation circuit further including a plurality of switching elements coupled between the input terminals and the output terminals, operable with respect to each output terminal to apply one of several alternative states including: (i) a first active state for biasing the output terminal to a high voltage to drive an associated stator winding at the high voltage; (ii) a second active state for biasing the output terminal at a low voltage to drive the associated stator winding at the low voltage; and (iii) an inactive state in which the associated stator winding is not driven; a plurality of voltage control functions individually associated with different ones of the output terminals, each control function being operable to bias its associated output terminal at an alternate voltage between the high voltage and the low voltage; and a controller operatively coupled to the commutation circuit to apply the alternative states selectively to the output terminals to generate a commutation cycle comprised of a sequence of primary steps, the controller further being operatively coupled to the voltage control functions to selectively actuate the control functions during transitional steps of the commutation cycle between pairs of adjacent primary steps, the controller being specifically operable with respect to a selected one of the output terminals undergoing a change in state between a given one of the primary steps and a succeeding one of the primary steps to bias the selected output terminal to the alternate voltage during a given transitional step between the given and succeeding primary steps.