Sgs-Thomson Microelectronics Limited

Stmicroelectronics Gmbh

Scott W Cameron

Karl M Schlager

Axel Alegre De La Soujeole

Francesco Carobolante

The present application discloses an innovative improved circuit, in which the long transient at write-to-read transitions is avoided by using a shorting switch to short the inputs of the first amplifier stage together when the read amplifier is activated. This speeds up write-to-read transition. Moreover, since read mode can now be entered more quickly after a power-down condition, this circuit also permits the use of other power-saving tricks to idle the read amplifier momentarily.

Input stage with reduced transient time for use in multiplexing transducers that require a switched DC bias

A method and integrated circuit for providing drive signals to a polyphase dc motor. The integrated circuit is fabricated on a semiconductor substrate for providing drive signals to a polyphase dc motor. The circuit includes a coil drive circuit for connection to drive coils of the motor to selectively supply drive currents thereto in a predetermined sequence. A sequencer circuit commutatively selects the drive coils to which the drive currents are selectively supplied, and a motor, speed controlling circuit controls the speed of the motor by controlling the speed of commutation. A temperature sensing element, such as a diode, is fabricated in the substrate to indicate the temperature of the substrate, and a temperature measuring circuit is connected to the temperature sensing element and to the motor speed controlling circuit to operate the motor speed controlling circuit to slow the speed of the motor when the temperature of the substrate exceeds a first predetermined temperature. If desired, temperature measuring circuit can include a circuit for measuring a second temperature higher than the first predetermined temperature to operate a shut down circuit to turn off the motor if the substrate temperature is too high.

Overtemperature warning cycle in operation of polyphase DC motors

An innovative differential amplifier circuit, which can control the midpoint potential of a load which does not itself have any midpoint connection. This is achieved by using a proxy load element in parallel with the primary load. The proxy load is of much higher impedance value than the primary load, and does have a center tap. The potential of the center tap of the mirrored load is used for a feedback connection to a control loop which regulates the output to both the primary load and the proxy load.

Differential amplifier with proxy load for control of output common mode

An innovative disk drive system which provides a regulated bias current to a magnetoresistive read head, and controls the voltage of the magnetoresistive read head terminals so that the CENTER of the resistor is at ground. This halves the peak magnitude of the head-to-disk voltage.

Symmetrical resistive transducer biasing circuit and method

An innovative circuit for driving the write head. All of the driving transistors are NPN, and are prevented from saturation. This is achieved by shifting and scaling down the differential drive applied to the pull-up transistors, to drive the pull-down transistors with levels such that the pull-down transistors cannot reach saturation. This provides a very simple circuit in which all four of the drive transistors are NPN, and all are kept out of saturation. Moreover, the peak write current applied to the head is precisely limited.

Differential high speed inductive driver with a bidirectional current

A method and circuit for braking a forward rotation of a rotor of a polyphase DC motor. A commutation sequencer is incremented by several phases to produce an incremented commutation sequence to produce a magnetic flux vector that lags a magnetic pole of the motor. Driving currents are applied to coils of the motor in accordance with the incremented commutation sequence to brake the rotor. The method is implemented in a circuit that has a sequencer for incrementally generating sets of commutation signals to select stator coils for energization to rotate the rotor. A power stage to which the commutation signals are applied energizes the selected coils in accordance with the commutation signals. A circuit interrupts the energization of the selected coils and the commutation sequence is altered to produce a sequence that produces a negative torque on the rotor. Circuits are also provided to inhibit application of the altered commutation sequence until recirculation currents in the power stage caused by the coils in response to the reduction of the input voltage have fallen below a predetermined level, and to inhibit application of the altered commutation sequence until a voltage on a sense resistor between the power stage and a reference potential has fallen below a predetermined level after an operation of the circuit for interrupting the energization of the selected coils.

Method and circuitry for drag braking a polyphase DC motor

In a method for aligning a rotor of a polyphase dc motor in preparation for starting the motor. a first energization signal is applied to field coils of the motor in a first predetermined phase for a first predetermined time. Then, a second energization signal having a second predetermined phase displaced from the first phase by a predetermined amount is applied to the field coils for a second predetermined time period. In one embodiment, the second energization signal is applied to produce a maximum torque upon the rotor when the rotor is positioned at a location determined by the first energization signal. In the case of a three phase motor, the second energization signal is displaced by two commutations from the first energization signal. Circuitry for aligning a rotor of a polyphase dc motor in preparation for startup is also presented having circuitry for applying a first signal to selected field coils of the polyphase dc motor having a first commutative phase for a first predetermined time, and circuitry for applying a second signal to other selected field coils of the polyphase dc motor having a second commutative phase for a second predetermined time.

Method and apparatus for starting polyphase dc motor

A circuit and method for operating a polyphase dc motor of the type having a plurality of driving coils connected together at a center tap current input node. Each driving coil have a current input node at an end opposite the center tap connection. A plurality of pairs of switches are arranged for connection in series across a power supply voltage. Each pair have a connection node between each switch connected to a respective one of the current input nodes. A sequencer individually operates the switches to cause a driving current to be passed between sequentially selected only single ones of the driving coils and the center tap current input node.

Circuit and method for operating a 3-phase motor with a uni-coil phase

A method and circuit for operating a polyphase dc motor having a plurality of driving coils is presented. In one of the available operating modes, drive current supplied to the driving coils is chopped, in PWM fashion to control the maximum current delivered thereto by turning the drive current on and off. Zero crossings of a back emf voltage of the driving coils that are connected into a floating state are detected for producing a commutation signal, and the detection of zero crossings is inhibited for a predetermined time after the drive current is turned off during the chopping step to avoid detecting a false zero crossing. In normal operation, detected back emf sampled voltages are forwarded to back emf detection circuitry responsive to a high frequency clock.

Method and apparatus for operating polyphase DC motors using a PWM

A method and apparatus for operating a polyphase dc motor selectively in dual-coil or uni-coil commutation modes. The motor has a plurality of 'Y' connected driving coils connected together at a center tap. Each driving coil has an input node at an end opposite the center tap, and is driven by a switch pair. Each switch pair is arranged for connection in series across a power supply voltage, and has a node between each switch connected to a respective one of the coil input nodes. An additional pair of switches are provided for connection in series across the power supply with a connection node between each switch connected to the center tap. A circuit is provided to operate the switches to cause a driving current to be passed between sequentially selected pairs of the driving coils for an initial start-up time. Also, a circuit to operate the switches after the initial start-up time is provided to cause a driving current to be passed between sequentially selected only single ones of the driving coils and the center tap current input node. The apparatus also has a circuit for detecting a zero crossing of a bemf signal of a floating one of the driving coils and a delay circuit for establishing a delay between a zero crossing and a commutation of driving signals to the coils. A circuit operates the delay circuit to provide a first predetermined delay in dual-coil mode and a second predetermined delay in uni-coil mode.

Method and apparatus for starting a sensorless polyphase DC motor in

A circuit and method for operating a polyphase dc motor of the type having a plurality of driving coils that are commutatively energized in a predetermined sequence to rotate a rotor has a zero crossing detector connected to determine when a back emf of a floating driving coil crosses zero. A generator for generating commutation sequence signals controls which of said driving coils are energized a delayed time after said zero crossing detector detects that a back emf of a floating driving coil has crossed zero. A mask circuit inhibits said zero crossing detector for a delayed time after a commutation change, in dependence upon an acceleration of the rotor. Also, a circuit is provided for adjusting the commutation delay time after a back emf of a floating one of said coils crosses zero, in dependence upon the acceleration of the rotor.

Method and apparatus for detecting velocity profiles of a spinning rotor

Pulse Width Modulation (PWM) techniques, often used to reduce the power dissipation in polyphase motors, chop the current in the coils of the motor at their peak current levels, to achieve maximum torque, to allow rapid accelerations, and to reduce the power dissipated in the chip to a level proportional to the duty cycle. During the time the current is switched off, the current which has been established in the coils of the motor is allowed to be dissipated. Accordingly, when the switching transistors of the active coils are turned off during PWM mode chopping, a non-rectifying ground return path is provided for flyback energy in the active driving coil. This non-rectifying ground return path is provided by switching transistors in parallel with flyback diodes, operated in a form of synchronous rectification. This gives an alternate current path for the coil current to reduce the voltage drop across the diodes, and thereby reduce the power dissipation and heat in the chip.

Synchronous rectification method for reducing power dissipation in motor

A circuit for operating a polyphase dc motor includes first circuitry for determining when the back emf of the floating driving coils crosses zero. A first counter counts a time period between a first set of zero crossings, and a second counter is loaded with the count reached by the first counter. The second counter counts a time period between a subsequently occurring set of zero crossings. If the second counter reaches zero before the occurrence of a third zero crossing, a warning signal is generated. A method for determining if a deceleration rate of a polyphase dc motor exceeds a predetermined threshold includes measuring a first period between a first set of zero crossings of the back emf of the floating driving coils, and comparing the measurement of the first period with a subsequent period between a subsequent set of zero crossings. If the subsequent period is larger than the first period by a predetermined amount a warning signal is produced. The first period is measured by counting up from zero at a first predetermined rate from a first zero crossing until a second zero crossing occurs. The comparison of the measurement of the first period with a subsequent period is done by counting down at a second predetermined rate from the count reached in the up count when the second zero crossing occurred. And the warning signal is produced if the down count reaches a zero before a third zero crossing occurs.

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Milpitas, CA, United States of America

Scott W Cameron