Abstract:
A method of driving a multiphase brushless motor with N windings connected in a star or in a polygonal configuration and driven according to a certain periodic voltage profile includes cyclically keeping for a certain time interval at least one of the N windings in a fixed state of low or high saturation by 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 electric period, in which said 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 definition of conversion of a digital value in a PWM signal using an N-bit up/down counter is improved by increasing the dimension of the input datum to N+2 bits, using the two lsb of the N+2 input datum for selecting one among three intermediate levels between two consecutive values of an N-bit dynamic, according to a predefined table of combinations. The converter may still use an N-bit comparator.
Abstract:
The present invention relates a Pulse Width Modulation (PWM)/linear driver for an electromagnetic load by a bridge circuit (15) of the type having a signal input (Vm, GND) and a signal output (OutM, OutP) and at least two conduction control inputs (C1, C2) for driving a voice coil motor (VCM) in a linear mode and in a pulse width modulation (PWM). The bridge circuit (15) is driven by a PWM converter (16) coupled to one (C1) of said two control inputs and by a linear amplifier (17) coupled to the other (C2) of said two control inputs.
Abstract:
The control of the current in PWM mode through independently controlled windings of a multiphase motor driven in a "bipolar" mode is implemented by employing only two sense resistors and related control loops, regardless of the actual number of windings.
Abstract:
Usually the control power signal lines of a positioning voice coil motor (VCM), driven in a PWM or PSM mode, and the relatively low power signal lines of a read/write (R/W) head runs parallel to each others along a unique flat cable that connects the VCM moved arm carrying the head to the related drive control and signal processing circuitries of a disk storage device. When controlling the VCM at relatively low current levels, both PSM drive signals approach the 50% duty cycle and therefore the PSM commutations become so close each others that may practically be considered concurrent. In these conditions of operation, switching energies sum and reach a level that may be sufficient to inject switching noise from the VCM power lines in adjacent low level signals lines of the connection flat cable. A way of preventing concurrent commutations of a pair of PSM drive signals of an output bridge stage driving a voice coil motor (VCM), consists in establishing a certain threshold level of programmed current to be forced the voice coil motor and when the level of the programmed current to be forced through the voice coil motor drops below said threshold, enhancing the time offset between commutation edges of the two PSM drive signals by a certain minimum time. This is accomplished either by phase shifting one of the signals from the other signal or by broadening the width of the pulses of one of the two PSM drive signals and by narrowing the width of the pulses of the other PSM drive signal, while maintaining constant the individual duty-cycle of each drive signal.