Patent ID: 6710564
Filing Date: 2004-03-23
Classification: H02P

Abstract:
A method for controlling a brushless motor having an inverter providing a current to said brushless motor, said inverter comprising:a first plurality of switching elements connected between a first terminal of a DC power source and a phase terminal of each coil of said brushless motor; a second plurality of switching elements connected between a second terminal of said power source and a phase terminal of each coil of said brushless motor; and a drive control device for selecting a state of said first plurality of switching elements and of said second plurality of switching elements, whereby either said state of said first plurality of switching elements or said state of said second plurality of switching elements is controlled by a pulse width modulation (PWM) control, so that said drive control device controls a rotational speed of said brushless motor; wherein said method comprising the steps of: determining whether a combined voltage of a first transient voltage and a second transient voltage exceeds a voltage limit; and altering the switching of said state of said first plurality of switching elements by said PWM control, such that said combined voltage is less than a voltage limit of said first plurality of switching elements or said second plurality of switching elements; and wherein said first transient voltage is generated between an input terminal and an output terminal of each of said second switching element in said off-state, when said state of said second plurality of switching elements is switched; and wherein said second transient voltage is generated between an input terminal and an output terminal of each of said first switching element in said off-state, when said first plurality of switching element is switched.