Abstract: A non-linear integrator of a closed loop integration system selectively modifies the gain of the closed loop integration system in order to avoid system saturation while still experiencing high gain in a desired linear portion of the system. A non-linear integrator structure and method allow the gain of the closed loop integration system to be selectively modified in order to avoid saturation while experiencing high gain. The non-linear integrator includes an amplifier, a current source element which generates a bias input signal, a bias circuit which provides the bias input signal to the amplifier and allows the bias input signal to be selectively modified, a storage element coupled to the amplifier, and a gain element, coupled to the storage element, which produces an output signal determined by voltage on the storage element. A voltage input signal and a bias input signal are supplied to the amplifier which generates an amplifier output signal.

Abstract: A current mirror uses an operational amplifier to control the collector voltage of two mirroring transistors during operation. The operational amplifier is coupled to the collector of each mirroring transistor such that a differential in voltage between the collector will produce an output voltage which drives a MOS transistor. The MOS transistor, responsive to the output of the operational amplifier, adjusts the voltage at the collector of one of the mirroring transistors to restore equilibrium.

Abstract: A circuit for operating a polyphase DC motor, such as the type having a plurality of "Y" connected stator coils, has circuitry for charging the coils at a rate which will reduce EMI and other noise, while maintaining an acceptable charge rate. The gate of a selected high side driving transistor is charged at a relatively high rate during a ramping phase. During the ramping phase, the gates of the selected transistor is charged to a voltage near the voltage needed to form a channel in the transistor for conduction. After the ramping phase, the gates are charged at a lesser rate in order to control the rate of charging of the stator coils to prevent noise.

Abstract: A motor drive system, and method for operating the same, which includes current mirror load current sensing, is disclosed. Sensed current is used in the well known manner to control the low side drive of the motor. The disclosed motor system operates in a bipolar mode on startup, and in a unipolar mode during full speed operation. In unipolar mode, a current mirror transistor is provided to sense the load current through the center tap drive transistor in a continuous manner. Ripple in the sensed current is avoided, as the center tap drive transistor is not commutated during motor operation in unipolar mode. In bipolar mode, current mirrors are provided for both of the high side and low side drive transistors in each leg, with the currents summed for each coil at a sum node, and with the summed current applied to a cumulative sum node; the summed current never drops to zero, as only one drive transistor changes in each phase change in the commutation sequence.

Abstract: A stator coil driver circuit for a brushless DC motor, which minimizes torque ripple by keeping the current in the commutating phases constant, is disclosed. The circuit includes a slew rate control circuit for ramping up the current or ramping down the current during commutation. The slew rate control circuit consists of a capacitor, a first current source for charging the capacitor, and a second current source for discharging the capacitor. The circuit also includes a sense resistor or a sensefet and an operational transconductance amplifier for providing feedback control.

Abstract: The invention is used in a disk drive and comprises a feedforward circuit connected between the head position circuit and the speed control loop circuit. The feedforward circuit precompensates the speed control loop for changes in rotation drag due to movements in the head of a disk drive. The feedforward circuit may include one or more deadband amplifiers and may include filter circuit. The invention disclose the method for controlling the speed of a spindle motor in a disk drive which includes the step of precompensating the speed control loop circuit with a processed head positioning signal.

Abstract: A phase-locked loop (or frequency-locked loop) based circuit for controlling the drive applied to a DC polyphase motor is disclosed. The disclosed circuit includes a clamp circuit, connected to the input of the motor drive amplifier, for limiting the current applied to the drive amplifier, in order to ensure that the power supply is not overloaded. According to one embodiment of the invention, the clamp circuit includes a buffer amplifier having a source leg and a sink leg. During a current control mode, both the source leg and sink leg of the buffer amplifier are enabled to drive the input of the motor drive amplifier; the buffer amplifier is a differential amplifier and applies a feedback signal from the drive amplifier input to control the current applied thereto according to an input limit signal.

Abstract: A constant velocity head parking circuit is disclosed. The circuit includes a voice coil motor, a sense resistor, a park voltage source, and a feedback loop. The feedback loop includes a scaling circuit which can be constructed with an op amp and two resistors. The scaling circuit adds a voltage to the park voltage so that any voltage loses in the voice coil motor are compensated for.

Abstract: This application discloses circuit and method for reducing the turn-off time of a power transistor driving an inductive load. The circuit clamps the gate to source of a power transistor by using two field effect transistors as the current path across the gate and source of the power transistor. A zener diode connected from the source to gate of the two field effect transistors is used to provide high voltage protection.

Abstract: A method and circuit for implementing a frequency lock loop circuit in a disk drive is disclosed. The circuit includes the motor control elements of a direct current motor plus a coarse counter, a fine counter, and a digital to analog converter. The coarse counter is used to count down from a programmed coarse count. The fine counter begins to count down from a fine count when the coarse counter reaches zero. The count in the fine counter, when a zero crossing occurs, represents the difference between the expected period and the actual period and is loaded into a digital to analog converter which converts the difference to an analog voltage which is used by the coil drive circuit to either speed up or slow down the motor. The digital to analog conversion may be realized by a charge pump circuit.

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: Circuitry for selectably connecting the body node of drive transistors of a motor control circuit. In particular, those transistors that are turned off when operating the motor in a unipolar mode have their body nodes switched so as to be connected to a reference voltage, such as ground, during unipolar mode, and to be connected to the transistor source during bipolar mode (i.e., when the transistors are active). The circuitry also is operable to briefly connect the body nodes of the transistors to their source when the opposing drive transistor is commutated, in the unipolar mode. In this way, forward biasing of inherent diodes in the drive transistor is avoided in unipolar mode, except when useful to clamp the inductive kick of the motor coils.

Abstract: A circuit for operating a polyphase dc motor that has a plurality of driving coils has circuitry for receiving the back emf of at least one of the driving coils at a time when the at least one of the driving coils is in a floating state prior to the desired commutation sequence. Circuitry is provided for determining an anticipated direction the back emf will cross a reference voltage based upon the desired commutation sequence. And circuitry is also provided for determining if the back emf received by the circuitry for receiving the back emf crosses a reference voltage from other than the anticipated direction.In addition, a method for operating a polyphase dc motor having a plurality of driving coils includes determining the actual instantaneous position of the rotor of the motor by determining when the back emf of at least one coil at a time when the at least one coil is in a floating state prior to the desired commutation sequence crosses a reference voltage from a predetermined direction.

Abstract: A kelvin current sensing circuit in an integrated control circuit that controls the current flowing through the driving coils of a polyphase DC motor. The invention provides for adjusting the voltage to the lower driver transistors of the control circuit by having the kelvin current sensing occur internally within the chip. A ground compatible differential amplifier circuit is used in one embodiment. Each of the lower transistors are connected to the base of respective PNP transistors, the emitters of which being connected together to control one side of the differential amplifier. A control voltage is applied to the other side of the differential amplifier. The output of a comparator, that is connected to the differential amplifier, is used to control the operation of the lower driver transistors. Therefore all of the sensing is done internally in the semiconductor chip. The voltages are taken at the source of each of the lower transistors.

Abstract: A circuit and method for detecting when the back emf of a motor coil passes a predetermined level includes circuitry for providing a voltage proportional to the back emf of the motor coil, and circuitry for providing a voltage proportional to a reference potential. A first bias voltage is added to the voltage proportional to the back emf to produce a first added voltage, and a second bias voltage is added to the reference potential when the back emf of the motor coil is expected to change in a predetermined direction to produce a second added voltage. A comparator produces an output change when the first added voltage becomes larger than the second added voltage at the predetermined level.

Abstract: A circuit for increasing the reverse breakdown voltage of a bipolar transistor that provides drive current to an inductor has a voltage control transistor connected between the collector and base of the bipolar transistor, having a control element connected to one end of the inductor. The circuit can be fabricated as a portion of an integrated circuit formed on a single semiconductor substrate. Also disclosed is a method for increasing the emitter-collector breakdown voltage of a bipolar transistor in which the base and collector of the bipolar transistor are shorted when the emitter-collector voltage exceeds the breakdown voltage by turning on a transistor connected between the base and collector of the bipolar transistor.

Abstract: A circuit for sensing the current delivered to a load, or multiple loads, such presented by a polyphase DC motor, without significantly dissipating the energy delivered to the load, has a predriver circuit and a power delivery circuit for each load. The predriver circuit is connected in a series path between a voltage source and a control element of the power delivery circuit, and the power delivery circuit is connected between a connection node and a respective one of the loads. A sensing element is connected in a series path between the source of voltage and the power delivery circuit connection node. In a preferred embodiment, the sensing element is a resistor, the predriver circuit is a PNP transistor, and the power delivery circuit is an NPN transistor. The PNP and NPN transistors are connected to form a pseudo-Darlington transistor pair, with the collectors of the NPN transistors interconnected to enable a single sense resistor to be used to sense the current in each of the loads.

Abstract: A circuit and method are provided for automatically adjusting a commutation delay from events indicating a position of a polyphase dc motor. The circuit includes a driver to supply drive current to selected stator coils of said motor. A sequencer is connected to control the driver to apply drive current to selected motor coils to rotate the motor. Motor position detecting circuitry is connected to detect the events indicating the position of the motor. A commutation delay circuit is connected to increment the sequencer in response to the detection of the events indicating the position of the motor detected by the motor position detecting circuitry. A circuit for adjusting the delay of said commutation delay circuit between each event and each sequencer commutation provides optimum motor commutation for maximum power efficiency.According to the method, drive current is supplied to selected stator coils of said motor in predetermined commutated sequences to rotate the motor.

Abstract: A circuit and method for driving an inductive load has a first transistor with a current flow path connected to provide drive current at an output node to the inductive load, and a control element for controlling the current in the first current flow path. The control element is adapted for connection to receive a control signal for turning the current in the first current flow path of the first transistor on and off. A second transistor has a current flow path connected between the output node and the control element of the first transistor, and has a control element for controlling the current in the current flow path. A capacitor is connected between the control element of the second transistor and a reference potential, the capacitor being much larger than an inherent capacitance at the control element of the first transistor divided by a current gain of the second transistor. Finally, a rectifier is connected between the output node of the first transistor and the capacitor.

Abstract: A high side driver circuit and method for controlling the turnoff slew rate to an inductor of a motor is presented. The inductor is selectively connected between a supply voltage on a high side and a reference potential on a low side. The driver circuit has a power transistor having a current control path connected in series between the high side of the inductor and the supply voltage to connect selectively the inductor to the supply voltage. An amplifier has an output connected to a control element of the power transistor. A capacitor connected between a non-inverting input of the amplifier and the reference potential and a current source connected between the non-inverting input of the amplifier and the reference potential are switchably connected between the supply voltage and the non-inverting input of the amplifier for turning on and off the circuit. A feedback path is connected between the high side of the coil and an inverting input of the amplifier.