Abstract: A method drives a three-phase motor having first, second, and third coils. The method electrically connects the first coil to a first voltage reference and the second coil to a second voltage reference while leaving the other coil floating during a first driving phase. During a second driving phase, the first coil is electrically connected to the first voltage reference and the third coil is electrically connected to the second voltage reference while the second coil is left floating. During a transition phase that immediately follows the fast driving phase and immediately precedes the second driving phase, the second coil is electrically connected alternately to the first and second voltage references. By alternately connecting the second coil to the first second voltage references and during the transition phase, the method causes the current through the second coil to reduce to zero at a slower rate than prior methods.

Abstract: A method and system produce a PWM signal using a comparator having first and second input terminals and an output terminal at which the PWM signal is produced. The method includes powering the comparator with a supply voltage and receiving a modulating signal at the first input terminal. The method creates a carrier signal with a constant frequency and a maximum amplitude equal to the supply voltage. The comparator receives the carrier signal at the second input terminal and compares the carrier signal to the modulating signal, thereby producing the PWM signal at the output terminal. By creating and using a carrier signal with a maximum amplitude equal to the supply voltage, the PWM signal produced by the method is immune from changes in the supply voltage.

Abstract: A method is for driving a multiphase brushless motor with N windings connected in a star or in a polygonal configuration. The windings are driven according to a certain periodic voltage profile. The method includes cyclically keeping for a certain time interval at least one of the N windings in a fixed state of low or high saturation and applying to the other phase windings instantaneous voltages according to a predefined different periodic voltage profile such that the resultant voltages on the windings are coherent with the certain periodic voltage profile. The number of intervals, in an entire electrical period, in which the fixed high or low saturation state of one winding is produced, depends on the predefined driving profile and upon the number N of windings of the motor.

Abstract: A BEMF detector and method detect the BEMF of a three-phase motor using a fully differential detection system. The motor has a first coil coupled between a first coil tap and a center tap, a second coil coupled between a second coil tap and the center tap, and a third coil coupled between a third coil tap and the center tap. The BEMF detector includes a differential amplifier having first and second inputs and first and second outputs, with the first input being coupled to one of the coil taps and the second input being coupled to the center tap. The BEMF detector also includes a comparator having first and second inputs coupled respectively to the first and second outputs of the differential amplifier and an output at which a BEMF signal is produced that is related to the BEMF of the motor. The differential amplifier may be part of an anti-alias filter structured to fix to a known stable value a common mode at the outputs of the differential amplifier.

Abstract: Monitoring of current flowing through an inductive load driven through a bridge power stage in a PWM mode, comprises sampling the signal output by a sensing amplifier with a Sample & Hold circuit including a sampling switch and a storing capacitor. The average value of the current in the load is monitored by sampling at a half way point of an active driving phase and at a half way point of a current recirculation phase by closing the switch with a synchronizing pulse that coincides with the half way points of these phases of operation. The monitoring uses a pair of complementary periodic reference signals and uses a sensing amplifier to amplify the signal existing on a current sensing resistor functionally connected in series with the load. This produces an amplified signal representative of the current in the load to be fed to an input of an error amplifier driving a power amplifier of the bridge stage.

Abstract: The control of the current in a PWM mode through independently controlled windings of a multi-phase motor driven in a "bipolar" mode is implemented by employing only two sense resistors and related control loops. This is so regardless of the actual number of windings of the motor.

Abstract: A circuit for driving a bridge circuit BR having a signal input I1,I2, and a signal output O1-O2, and at least two conduction control signals C1 and C2 by the PWM procedure. The circuit includes a first virtually-square-wave generator CO1 having an output coupled to one of the two control inputs and a second virtually-square-wave generator CO2 having an output coupled to the other of the two control inputs. In this manner, the bridge is driven by two square waves, the null value of the current at the output )O1-O2 no longer constitutes an intrinsic discontinuity and any value, even around zero, is controllable with relative ease.

Abstract: A circuit and method for driving a brushless sensorless direct current (DC) motor (2), using the steps of: at the beginning of each phase, driving the motor in PWM mode; monitoring the duration (Tc) between successive zero-crossings of the back electromotive force (BEMF), and accordingly predicting the next zero-crossing; and before the next predicted zero-crossing, switching to a linear driving mode only until the actual zero-crossing of the BEMF.