Bimodal controller for a multi-phase brushless DC motor

A controller for a multi-phase brushless DC motor which is selectively operable in either full wave or half wave modes for maximizing either the output torque or output speed, respectively, of the motor. One terminal of each phase winding is connected to the terminals of a DC voltage source via upper and lower legs of a full wave bridge circuit, while the other winding terminals are mutually connected to a common terminal which is selectively isolated from or returned to a terminal of the source. When relatively high motor output torque is required to drive a relatively heavy load, the winding common terminal is isolated from the source and the bridge circuit is operated in the full wave mode to energize the motor windings with bidirectional current. When load to be driven is relatively light and higher motor speed is desired, the winding common terminal is connected to a terminal of the source and the bridge circuit is operated in the half wave mode to energize the motor windings with unidirectional current.