Abstract: A driving circuit of a DC motor includes a control circuit for providing a control signal, and a motor drive circuit commanded by the control circuit for providing respective command signals for the switches of an output power stage connected to the DC motor. The output power stage is connected to a power supply line and drives the windings of the DC motor. The driving circuit prevents generation of voltage surges having a significant magnitude on the power supply line because the driving circuit has logic circuits for preventing any substantial inversion in the direction of current flow in the supply lines when the DC motor operates as a current generator.

Abstract: A method for detecting a zero-cross event of an induced back electromotive force (BEMF) or of a nullification instant of a periodic current in a PWM driven winding, by circuits generating an analog signal representative of the induced BEMF or of the nullification instant of the periodic current, comparing the analog signal with zero and producing a first logic signal, generating a PWM driving signal, and storing a time between two consecutive zero-cross events, is provided. The method may include storing a time between a last two zero-cross events and synchronizing the PWM driving signal from a last zero-cross event having a duration equal to a difference between an established time based upon the stored time interval and a first time. If a new zero-cross event is not detected within the established time, switching of the PWM driving signal may be disabled for a time having a maximum duration equal to a second time or until a new zero-cross event is detected.

Abstract: A start-up procedure for a multiphase brushless motor to be accelerated until reaching a certain speed includes determining the starting position of the rotor and performing an excitation phase including forcing a drive current in the phase windings of the motor for an established period of time. This is done according to a switching sequence for inducing a rotation in the desired direction. Furthermore, the method may include sensing the position reached by the rotor at the end of each excitation phase. The start-up procedure is eventually interrupted when the established speed has been reached or exceeded. Additionally, the duration of a next phase of excitation may be increased or reduced, and the switching sequence may be modified, based upon the number of consecutive times in which the current position is found to be the same or different from the previously detected position, respectively.

Abstract: A circuit to establish an accurate instantaneous position of a DC motor rotor includes an input terminal to receive a rotor position signal. A first counter circuit counts to a value between two successive rotor position signals at a slow clock rate, and stores this count value in a register. Then a second counter begins counting from zero at a system clock rate, which is faster than the slow clock rate. The first counter circuit and the second counter circuit are evaluated by a comparator, and when the counters equal one another, the instantaneous position signal is generated. Alternately, the second counter can be a down-counter that is initially loaded with the count value, and the instantaneous position signal is generated when the second counter reaches zero.

Abstract: A start-up routine is provided for a multiphase brushless DC motor having one or more rotor position sensors insufficient to provide for an angular resolution as high as the angular resolution of the synchronized driving system of the motor. The start-up routine includes setting at least an angular check zone having a certain arc length angularly correlated to the one or more rotor position sensors, assuming a certain initial rest position of the rotor, and exciting for fixed time intervals the phase windings in a sequence for rotating the rotor toward an angular position next to the initial position. This routing is performed in the desired direction while masking the signals from the one or more rotor position sensors for a preestablished masking time.

Abstract: A method of detecting the relative position of the rotor of a sensorless DC brushless motor driven in a tripolar mode includes the step of monitoring the voltage difference between the drive voltage that is applied to at least one winding of the motor and the voltage drop on a resistive portion of the drive current path through the same winding. The voltage drop may be detected between the two current terminals of an MOS power device of the driving bridge of the winding. The monitoring of the voltage difference is used to signal a perturbation from a pre-existing condition of correct synchronization of the phase switchings during a driving phase in a tripolar mode of the motor. Such information may be used by the driving system to switch to one of a bipolar mode, a unipolar mode or a tripolar mode with momentary drive interruptions, until restoring a correct synchronization condition and/or attain a correct rotating speed.

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: The sensing of the rotor position for synchronizing the drive of a multi-phase brushless motor when driven in a "multi-polar" mode is carried out by interrupting the driving current in at least one of the windings of the motor coupled with a zero-cross sensing circuit of the BEMF signal. This done by using a first logic signal, enabling a logic gate for asserting a zero-cross event detected by the circuit by a third logic signal, and simultaneously resetting the first signal and the third signal after a certain period of time from the instant of interruption.

Abstract: The sensing of BEMF signals in the motor's windings for synchronizing the phase switchings, in driving a brushless and sensorless motor with predefined constant voltage or current values or predefined voltage or current profiles stored permanently in a memory, is greatly simplified through a reconstruction technique that avails itself of the knowledge of the predefined drive values. The sensing does not require access to the center star point and is performed by sensing either the voltage difference between the terminals of two windings or of the current flowing in two windings, depending on whether a current or voltage mode is employed.

Abstract: Pre-defined driving profiles for the distinct phase-windings of an electronically controlled brushless motor are continuously reconstructed for each switching phase and forced in the form of a drive current or voltage on the respective windings, in synchronism with a signal indicative of the rotor position, from just a first complete sequence and at least a first sample of the successive sequence of a number of sequences, each of N samples, equal to the number of switching phases of the motor, in which is divided a complete digitized pre-defined profile. The digital samples are stored in a nonvolatile memory and that are scanned at a continuously regulated clock frequency and with varying order and direction of scanning for reconstructing the instantaneous driving profiles for all the windings.