US 7,321,210 B2
Sensorless brushless direct current motor drive using pulse width modulation speed control at motor frequency
Peter N Wood, Rolling Hills Estates, Calif. (US)
Assigned to International Rectifier Corporation, El Segundo, Calif. (US)
Filed on Apr. 03, 2006, as Appl. No. 11/396,758.
Claims priority of provisional application 60/668897, filed on Apr. 05, 2005.
Prior Publication US 2006/0222345 A1, Oct. 05, 2006
Int. Cl. H02P 1/18 (2006.01)
U.S. Cl. 318—254  [318/138; 318/439; 318/599] 22 Claims
OG exemplary drawing
 
1. 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.