Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: A circuit for operating a polyphase dc motor, for example of the type having a plurality of "Y" connected stator coils, has circuitry for unambiguously determining the actual instantaneous position of the rotor of the motor, circuitry for determining a desired rotor position precedent to executing a desired commutation sequence, and circuitry for executing the desired commutation sequence when the circuit for determining the actual instantaneous position of the rotor detects that the rotor is actually in the desired rotor position. The circuitry for unambiguously determining the actual instantaneous position of the rotor includes a back emf amplifier switchably connected to at least one floating coil in accordance with sequence signals received directly from a sequence generator, and circuitry for determining when the voltage received by the back emf amplifier crosses zero from a predetermined direction.

Abstract: A circuit for resynchronizing the rotor of a polyphase dc motor having "Y" connected stator coils and a moving rotor has circuitry for determining the actual instantaneous position of the rotor, and circuitry for determining a desired rotor position precedent to executing a desired commutation sequence.