Method of controlling a brushless permanent-magnet motor

A method of controlling a brushless permanent-magnet motor, the method comprising:

• commutating a winding of the motor at times that are retarded relative to zero-crossings of back EMF in the winding;
• dividing each half of an electrical cycle into a conduction period followed by a primary freewheel period;
• dividing the conduction period into a first excitation period, a secondary freewheel period, and a second excitation period;
• exciting a winding of the motor during each excitation period;
• and
• freewheeling the winding during each freewheel period.

A control circuit for a brushless permanent-magnet motor, the control circuit being configured to:

• commutate a winding of the motor at times that are retarded relative to zero-crossings of back EMF in the winding;
• divide each half of an electrical cycle into a conduction period followed by a primary freewheel period;
• divide the conduction period into a first excitation period, a secondary freewheel period, and a second excitation period;
• excite a winding of the motor during each excitation period;
• and freewheel the winding during each freewheel period.