摘要:
A control circuit providing a driving current to a voice coil motor to position a reading and writing head of a disk memory system is described. The circuit comprises a first and a second class AB amplifiers the outputs of which are connected to the terminals of a first resistor in series with the voice coil motor so that a current passes through the voice coil motor and through the first resistor. The circuit comprises a sense amplifier the input terminals of which are coupled with the terminals of said first resistor, a device at the input of which is present a signal which is a sum of an external signal and of an output signal of the sense amplifier. The first amplifier and the second amplifier being driven in inverted phase by an output signal produced by the device. The circuit comprises means for inserting a second resistor in series with the first resistor so that said current passes through the series of said first and said second resistors and so that said sense amplifier has the input terminals coupled with the terminals of said series of resistors.
摘要:
A voltage ramp generator for a driver circuit is provided to give an output that is highly linear between zero and a maximum voltage has a combination of current sources or generators for charging and discharging a capacitor, with discharging performed by sequencing two different types of current sources. A first current source on the discharge side of the capacitor has transistors in cascode connected current mirrors and takes the capacitor voltage to a low value but not as low as zero. A second current source of a basic or simple current mirror then takes the capacitor voltage substantially to zero. The voltage ramp generator meets the requirements of high performance, integrated, driver circuits, particularly for achieving complete turn-off of a power device such as a DMOS transistor in a high side cascoded transistors goes up to a threshold near the full supply driver. It is optional to have two current sources for charging, also, where a first source with voltage and than a second source, in a basic current mirror, continues charging substantially to the supply voltage.
摘要:
A preslewing circuit to rapidly drop a voltage on the gate of a power device in a power stage has a combination of a bipolar transistor and CMOS transistors. The gate voltage is brought down by the preslewing circuit to a level at which an output voltage can begin to change. The combination has high conduction and can be integrated readily, with good internal isolation, in a small chip area, thus having qualities desirable for high performance, integrated, driver circuits.
摘要:
A power down brake latch circuit for dynamically braking a spindle motor in a disk drive system is disclosed. The power down brake latch circuit includes a reservoir capacitor, a smoothing capacitor, a timing circuit, and a logic circuit. The timing circuit includes a voltage divider and a bandgap comparator. The smoothing capacitor absorbs a BEMF voltage from the spindle motor as it rotates after losing power. The timing circuit generates a first signal when a voltage on the smoothing capacitor falls below a threshold. The logic circuit brakes the spindle motor in response to the loss of power and the generation of the first signal.
摘要:
A circuit for controlling the slew rate at a motor coil during turn-on in a commutation sequence is disclosed. The disclosed circuit includes a comparator for comparing the output of error amplifier to the input of the input buffer amplifier. The comparator connects the output of the error amplifier to the input of the buffer amplifier only after the input has been charged at a controlled rate. The integrating buffer amplifier includes an amplifier with a feedback capacitor, and a current source connected at its input, for reducing the voltage slew rate during turn-on of the transistor.
摘要:
An electronic circuit for controlling an analog quartz clock, particularly for installation in automobiles, has first and second counters for generating control pulses at different rates according to whether the clock is to be operated in a normal mode, or a time-setting mode. In addition, a single 11-bit counter allows "fast" or "slow" resetting of the time by a single push button.
摘要:
A method for starting a polyphase DC motor having a rotor. The position of the rotor is detected by initiating current in each of the phases of the motor and measuring a time period between the initiation of current in the coil and an instant when the current exceeds a threshold current. The phase in which the current reaches the threshold in the shortest amount of time is the phase closest to the position of the rotor. A phase closest to the position of the rotor is identified in each of an odd number of trials, and a starting phase is selected as the phase identified in the majority of trials. The motor is started by providing current to the starting phase.
摘要:
.�.A circuit comprising a switch series connected to a load; a first and second current recirculating branch alternately connectable parallel to the load, for reducing the current in the same; and a logic control unit for opening and closing the switch and recirculating branches, so that the load is supplied with a current rising to a peak value and then falling rapidly to and oscillating about a lower hold value; a transistor being provided for reducing the voltage supplied to the load by the first recirculating branch at the end of the fast fall phase, so as to eliminate uncontrollable operating zones and prevent the load current from falling below the hold value..!..Iadd.A device for driving an inductive load such as a fuel injector includes a drive switch and a voltage regulator that are coupled to the inductive load. The device also includes a control circuit that is coupled to the voltage regulator, the drive switch, and the inductive load. The control circuit receives a drive signal and in response to the drive signal controls the voltage regulator and the drive switch. Initially, the switch closes and draws a charge current through the inductive load. When the charge current reaches a peak level, the switch opens to allow a discharge current to flow through the inductive load. The voltage regulator regulates the discharge voltage across the inductive load such that the discharge current falls at a first rate. When the discharge current reaches a first value, the voltage regulator regulates the discharge voltage across the inductive load so as to decrease the rate at which the discharge current falls. When the discharge reaches a second value, the control circuit controls the drive switch to generate a hold current through the inductive load. .Iaddend.
摘要:
A driver circuit with an amplifier operated in a switching mode has threshold detectors with devices to compare the amplifier input and output voltage respectively to predetermined minimum and maximum levels representing fully off and fully on conditions for the driver circuit. The circuit provides signals to enable the amplifier to draw current from a supply only during transitions between the threshold levels and to otherwise disable the amplifier. The circuit is beneficial particularly when operating the amplifier from a voltage supply of very limited current capability, such as a charge pump voltage in an integrated circuit. The switching mode amplifier can be applied in high performance driver integrated circuits alone or in combination with innovative techniques for slew rate control and for preslewing the amplifier output that also provide high performance in compact circuit configurations.
摘要:
A circuit comprising a switch series connected to a load; a first and second current recirculating branch alternately connectable parallel to the load, for reducing the current in the same; and a logic control unit for opening and closing the switch and recirculating branches, so that the load is supplied with a current rising to a peak value and then falling rapidly to and oscillating about a lower hold value; a transistor being provided for reducing the voltage supplied to the load by the first recirculating branch at the end of the fast fall phase, so as to eliminate uncontrollable operating zones and prevent the load current from falling below the hold value.