摘要:
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. The BEMF detector also may include one or more fully differential filters positioned between the differential amplifier and the comparator to reduce noise and smooth the BEMF signal output by the comparator. One of the filters can be a linear phase, switched capacitor filter with a stable cutoff frequency.
摘要:
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. This enables the variations of the currents that the two phases in commutation, the second and third coils, to happen in a way that maintains their sum constant, as much as possible. This reduces the torque ripple during the phase commutations and its accompanying acoustic noise.
摘要:
A circuit for the speed recovery of a direct current motor includes an output stage, output stage having a first pair of transistors, a second pair of transistors, and means a first circuit configured to detect a current circulating in the motor. The output stage further includes a second circuit configured to, activate the second pair transistors for a determined first time period so as to short-circuit the motor, and, at the end of the first time period, unbalance the output stage so as to force a maximum current to circulate for a determined second time period as a function of a value detected by the first circuit during the first time period, so as to stop the motor.
摘要:
A circuit estimates speed of an electromagnetic actuator associated with a reading head of a disk storage unit and a digital controller. The circuit includes first and second supply terminals and an output terminal, with the first supply terminal being connected to the electromagnetic actuator. A measuring resistor is connected to the second supply terminal, and is connected in series with the electromagnetic actuator for measuring a current which passes therethrough when a supply voltage is applied between the first and second supply terminals. An adder has an output connected to the output terminal for providing an output voltage, a first input is connected to the first supply terminal, and a second input is connected to the second supply terminal. An adjustable-gain amplifier is connected between the measuring resistor and the second input of the adder for transferring the supply voltage and a voltage across the measuring resistor to the adder. A determination circuit is connected to the adjustable-gain amplifier for determining a gain thereof. The determination circuit includes a coarse setting circuit and a fine calibration circuit controlled by the digital controller.
摘要:
The present invention herein describes a tracking analog-to-digital converter, in particular of the differential input type. In an embodiment thereof the tracking analog-to-digital converter, having a differential analog input including a first analog input and a second analog input, and a digital output at a first number of bits comprising: a back and forth counter having a direction input and an output, with a second number of bits; a digital-to-analog converter having a data input coupled to said output of said converter, a reference input and an output, with a second number of bits; a first comparator having a positive input, a negative input coupled to said output of said digital-to-analog converter and an output coupled to said direction input; characterized in that said reference input is coupled to said first analog input and said positive input of said first comparator is coupled to said second analog input.
摘要:
A positioning system for a read/write head of a disk drive includes a rotatable data disk, a read/write head movable over the disk, a voice coil motor (VCM) connected to the head and a source of digital position signals. A control circuit includes means for generating a VCM control current, a sensor for sensing the VCM current and an amplifier having an inverting input connected to a reference voltage source through a resistor and to a sensor output, a non-inverting input connected to the source of digital position signals through a DAC and an output connected to an input of the drive means.
摘要:
A current sensing circuit for a pulse width modulation (PWM) application may include first and second input terminals to be coupled to ends of a sensing resistance, an output terminal, and first and second internal circuit nodes. The current sensing circuit further may include an input block comprising a first transconductance amplifier to be coupled to a supply voltage. The first transconductance amplifier may be coupled to the first and second input terminals and to the first and second internal circuit nodes. The current sensing circuit may also include an amplifier block comprising an amplifier to be coupled to a reference voltage, and coupled to the first and second internal circuit nodes and the output terminal, and a feedback block comprising a second transconductance amplifier to be coupled to the supply voltage and being coupled to the output terminal and the first and second internal circuit nodes. The input block may further include a third transconductance amplifier coupled in cascade to the first transconductance amplifier and to the first and second input terminals.
摘要:
A current sensing circuit for a pulse width modulation (PWM) application may include first and second input terminals to be coupled to ends of a sensing resistance, an output terminal, and first and second internal circuit nodes. The current sensing circuit further may include an input block comprising a first transconductance amplifier to be coupled to a supply voltage. The first transconductance amplifier may be coupled to the first and second input terminals and to the first and second internal circuit nodes. The current sensing circuit may also include an amplifier block comprising an amplifier to be coupled to a reference voltage, and coupled to the first and second internal circuit nodes and the output terminal, and a feedback block comprising a second transconductance amplifier to be coupled to the supply voltage and being coupled to the output terminal and the first and second internal circuit nodes. The input block may further include a third transconductance amplifier coupled in cascade to the first transconductance amplifier and to the first and second input terminals.
摘要:
A reduced hardware control circuit device includes a current loop for broad band Hard Disk Drive applications. The current loop detects the value of the current flowing on the coils of a voice coil electric motor incorporated in the Hard Disk Drive. A sensing resistance is connected in series with the motor and at least a driving driver for a relative motor coil. Advantageously the current loop is a transconductance loop with a first transconductance amplifier associated with the sensing resistance. A second transconductance amplifier is provided for fixing the current value to be applied to the motor. The circuit device advantageously is deprived of a local compensation in correspondence with the first transconductance amplifier.
摘要:
The method is for controlling a voice coil motor which drives a mechanical arm via a control circuit which sets the output nodes, to which the motor is connected, in a high impedance state for a certain time interval. The method and circuit detect the back electromotive force induced on the motor winding during the time interval, and deliver current pulses for driving the motor. The circuit compares the detected back electromotive force with a certain target value and regulates the amplitude of the driving current pulses as a function of the difference between the detected value of the back electromotive force and a voltage signal representing the desired speed of the arm, according to a pre-established function. A preferred embodiment includes such a function being a pre-established saturated linear characteristic with an offset value.