Patent ID: 7321210

Claim:
A variable speed brushless direct current (BLDC) motor drive circuit comprising: a plurality of high-side and low-side controlled switches coupled in a three-phase bridge configuration for commutating a BLDC motor having a motor frequency of operation, each phase of the bridge being connected to a corresponding phase of the motor; a controller for providing a drive signal to drive each of the high-side and low-side switches; and a speed control loop for controlling the motor by PWM of a DC bus voltage to achieve a constant motor speed, the speed control loop including: a pulse circuit receiving the drive signals provided from the controller for controlling the high-side switches and for providing a pulse signal that is related to a desired motor speed, a plurality of high-side drivers for driving the high-side switches, each high-side switch being coupled to a respective high-side driver, and a plurality of gating circuits each receiving the pulse signal from the pulse circuit and a drive signal for a respective high-side controller from the controller for generating a pulse width modulation (PWM) control signal at the motor frequency having a pulse duration determined by said pulse signal from said pulse circuit to thereby drive each of the high-side drivers to modulate their corresponding high-side switches.