Showing papers on "Constant current published in 1978"

Current sensing transducer for power line current measurements

Abstract: A current sensing transducer includes a conductive current divider including a branch path for conducting a fractional current proportional to a current to be sensed and being applied through the divider. A compensated transformer includes a primary circuit responsive to the fractional current and two secondary windings. An amplifier circuit controls the current input to one secondary winding in response to the output of the other secondary winding so that the flux of the primary circuit is virtually compensated in the core and the secondary winding current is a measure of the current to be sensed.

Constant current arc welder

Abstract: A constant current arc welder of the type in which arc current is regulated by thyristor phase angle adjustment, includes voltage feedback voltage control and current feedback current control, with automatic transfer from the voltage control mode into the current control mode when current has been established in the arc. A time delay allows smooth transfer to the desired current operative level by limiting the current inrush under an initial current reference and with a chosen feedback control dynamic characteristic current boost is also automatically provided when the arc voltage falls below a predetermined level.

Direct access coupler

Abstract: A direct access coupler for connecting a piece of terminal equipment, such as a modem to a telephone line pair, the coupler being of reduced size achieved in part by the use of a miniaturized isolation transformer and a constant current circuit to divert the off-hook current which would otherwise flow through the isolation transformer or a current-shunting choke and by the use of both an optical isolator off-hook circuit and an optical isolator ring detector circuit.

Automatic battery charge apparatus and method

Abstract: An automatic apparatus and method for charging a storage battery from a source of electrical current. The charger includes a current control circuit for conducting regulated charging current through the battery in steps. A voltage monitoring circuit determines when the steps occur by monitoring battery voltage conditions. The steps are sequenced by a ring counter that varies the bias conditions on the current control circuit and voltage monitoring circuit as the steps occur.

Power control circuit and a switching mode power supply employing this circuit

Abstract: A power control circuit for controlling the base current to a switching transistor connected in series with a primary winding of a switching transformer in which a logic circuit controls first and second amplifiers which respectively supply base current to and absorb base current from the switching transistor. The logic circuit blocks base current flow whenever the current flow through the transistor or a secondary winding of the transformer exceeds predetermined values in accordance with timing pulses.

Digital electric energy measuring circuit

Abstract: A digital electric energy measuring circuit for totalizing electrical power and energy usage from an alternating current supply by converting a voltage signal representing the current component into a pulse train signal whose frequency is proportional to the magnitude of the voltage, sampling that frequency to provide a digital value representing the current component, and then converting a voltage signal representing the voltage component into a second pulse train signal whose frequency is proportional to the magnitude of the voltage which is used to control the rate that the digitized value of the current component is successively added which provides an indication of electrical energy that is totalized and displayed

Switched current source for current limiting complementary symmetry inverter

Abstract: A complementary symmetry inverter comprising two field effect transistors and a current mirror amplifier. A constant bias current is supplied to the master path of the current mirror amplifier. The slave path of the current mirror amplifier and one of said field effect transistors are connected to form a switched current source in series with the other of said transistors. The switched current source limits the peak value of the switching current pulse in the inverter in fixed relation to the current in the master path of the current mirror amplifier when the inverter switches between logic states. The switched current source also limits the current between the inverter output and an external device.

Low-power magnetometer circuit with constant current drive

Abstract: The drive signal applied to the drive winding of a magnetometer is provided by a voltage controlled oscillator. The average current flowing through the drive winding is monitored, and a signal representative of the average current is applied to the input of the voltage control oscillator. The sense windings of the magnetometer are connected to a servo-loop which causes a current to flow in the sense windings which produces a magnetic field cancelling the sensed components of the earth's magnetic field. The magnetometer uses a drive signal which saturates the core for only a short duration of time thereby reducing the power required by the magnetometer while ensuring complete saturation of the core.

Alternate constant current or voltage generator for an ultrasonic generator

Abstract: This ultrasonic generator comprises a transducer supplied by an oscillator via a transformer. The oscillator is supplied in parallel by a constant current generator and a voltage generator. Means are also provided to block the voltage generator as long as the impedance of the load remains lower than an adjustable threshold, so that the supply functions as constant current generator and, on the contrary, to block the current generator as soon as the impedance of the load exceeds the adjustable threshold, so that the supply then functions as voltage generator and limits the output power.

Temperature compensated bias circuit for semiconductor lasers

Abstract: Within a power supply circuit for a semiconductor laser, output current is maintained constant at each temperature level over an operating range and the magnitude of that constant current is varied directly with temperature to maintain the light output of the laser substantially constant over the operating temperature range. In the preferred embodiment, the negative temperature coefficient characteristic of the base-emitter junction voltage for bipolar transistors is utilized to compensate for the negative temperature coefficient characteristic of the light output from the semiconductor laser.

Optical memory with injection laser as light source and detector

Abstract: In an optical memory device, such as an optical video disk, an injection laser is used as the source of the light, as the detector of the light reflected from the memory element and as the detector for controlling the proper focus of the light on the memory element The light reflected from the memory element is fed back into the injection laser and variations in certain characteristics of the injection laser, such as the optical output at constant current, the electrical current through the laser at constant voltage and the voltage drop across the laser at constant current, are used to read the memory device and to maintain the focus

Hybrid stimulator for chronic experiments

Abstract: A hybrid stimulator is described which combines constant current and constant voltage characteristics. Pulses are delivered with high output impedance to assure the passage of a predetermined amount of current. During the quiescent periods between pulses, the output changes to low impedance, diminishing the post-pulse charge. Electrode erosion and tissue damage are thus minimized, permitting safe, long term excitation.

High-voltage impulse driver for electromagnetic flowmeter

Abstract: A drive system for an electromagnetic flowmeter wherein the fluid to be metered is conducted through a flow tube to intersect a transverse magnetic field created by an electromagnet having an excitation coil. The resultant voltage induced in the fluid is transferred to a pair of electrodes mounted at diametrically-opposed points on the tube to yield a signal representing flow rate. The drive system, which is powered from an a-c line, includes a full-wave rectifier whose output voltage is applied periodically to the excitation coil at a rate which is low relative to the line frequency. In order to maintain the level of current through the coil at a substantially constant level during the excitation period without, however, consuming an undue amount of energy, the coil is shock-excited by a high voltage surge derived from the rectifier to generate a current flow therein having a substantially constant current level, thereby producing a steady-state flux field minimizing the presence of unwanted components in the output signal of the flowmeter.

Current integrating battery charger

Abstract: The battery charger employs integrator means and current switch means in combination with a control circuit whereby the control circuit receives a synchronizing signal at the start of each cycle as determined by a cyclical supply or pulse generator as well as information about the state of the integrator means which is compared with the predetermined average current such information determining the required control signals for the integrator means and current switch means so as to maintain the value of the average charging current substantially constant throughout the charging time. Current sense means being provided to sense the current flow through battery and supply the integrator means with said sensed current.

Switching regulated power supply apparatus

Abstract: A switching regulated constant voltage power supply apparatus, wherein a direct current voltage obtained through rectification and smoothing of a commercial alternate current power supply input is applied to a direct current/alternate current converting circuit implemented by a blocking oscillator such that the oscillator makes self oscillation upon turning on of the commercial alternate current power supply to provide an output from the converting circuit, the oscillator is adapted to operate in synchronism with the output from a driver circuit which is energized with the output from the converting circuit, and an error detecter is provided to detect an error fluctuation after rectification and smoothing of the output voltage from the converting circuit such that the detected output controls the converting circuit, thereby to provide a direct current constant voltage.

Automatic level control circuit

Abstract: An automatic level control circuit including a current controlled attenuator wherein the amount of attenuation is controlled by a control current, an amplifier for amplifying an output signal of the attenuator, a current rectifier for forming a DC current source in accordance with the amplitude of the output signal voltage from the amplifier, and a current shunt for absorbing an output current fed from the rectifier. The control current is produced as a difference between the current from the rectifier and the current absorbed by the shunt. When the current fed from the rectifier is larger than that absorbed by the shunt, the automatic level control circuit operates in a manner that, when its input signal is at low level, the circuit gain is large and, as the input signal level rises, the circuit gain drops.

Switching power supply having a wide range input capability

Abstract: A switching regulator type power supply, including a series switching element which, when energized, provides a voltage signal to an averaging filter, the output of which is applied to follow-on inverter and filtering circuits to produce a desired output voltage. In the startup mode of the supply, the switching element is energized by a circuit portion functioning as a blocking oscillator. The control action of the blocking oscillator results in a series of incremental increases in the voltage output of the averaging filter, thus avoiding large startup currents. When the output of the averaging filter reaches a predetermined first level, an error amplifier circuit is initiated, which forces the circuit portion to function as a constant current switched amplifier. The switching regulation of the error amplifier also results in a series of incremental increases in the output of the averaging filter, until a steady-state output is reached, at which point the switching element is controlled by normal regulation action.

Control circuit providing constant power source

Abstract: A circuit for starting and operating an arc lamp includes a full wave rectifier having an input connected to a source of alternating current line voltage and a pair of output terminals having a filter capacitor connected thereacross for providing a source of direct current voltage. Connected to one of the direct current terminals is a resonant charging circuit comprising a controlled rectifier switch, an inductor and a capacitor serially connected in a circuit loop. Another inductor, which may comprise the secondary winding of a starting pulse transformer, is connected between the output of the resonant circuit and one of the supply terminals for the arc lamp to provide the dual function of both averaging filter and lamp ballast. The reference terminal of the direct current source is connected to the other arc lamp supply terminal and through a back swing diode to the output of the resonant circuit. A trigger pulse generator is coupled to the resonant charging circuit for intermittently operating the controlled rectifier switch, and a voltage divider is connected across the direct current source for sensing changes in the line voltage and adjusting the pulse rate of the trigger generator in response thereto. In this manner, once the arc lamp is started and operating, the resonant charging circuit maintains a source of constant power to the arc lamp regardless of line voltage variations. Protective sensing circuitry is also provided for controlling the trigger generator output in the event the line voltage is too low, the load current is too high, or the resonant circuit capacitor has not discharged to zero.

Energizing circuit for magnetron using dual transformer secondaries

Abstract: A magnetron energizing circuit preferably uses two transformers of the high leakage reactance type having isolated secondaries with an end terminal of each secondary connection to a common point which is at ground potential.The secondaries are connected to series condensers in two loops which provide leading current flowing in the secondaries at all times while both are connected in the circuit to produce saturation in the respective cores of the secondaries whereby to achieve substantially constant current and good regulation for variations in the primary voltage. A single magnetron is served by the circuit and variations in the loading of the magnetron are also compensated for by virtue of the substantially constant current circuit. A modified form is described which uses a single transformer having two isolated secondaries. The secondaries are connected in opposite phase with respect to the respective capacitors which they serve to charge to obtain a full wave doubler operation when the transformers are both in circuit but with low peak current. The combined secondaries and condensers are connected through a rectifier or rectifiers to a magnetron used for heating purposes, the magnetron participating in the overall operation of the circuit and being of the continuous wave pulsed type so as to achieve heating in cooking ovens or the like. Disconnecting one of the transformers from the circuit converts the circuit into a lower power, but efficient half wave voltage doubler circuit. Isolating rectifiers prevent circulating currents.

CRT Beam current control apparatus

Abstract: In a television picture display device wherein a cathode of a picture display tube is driven by an emitter-follower and a control signal for a beam current reference level control circuit is obtained from the collector circuit of this emitter-follower, measures are taken to compensate for leakage currents from and to the cathode. To this end a blacker-than-black current compensation circuit is provided while furthermore it is ensured that the blacker-than-black curent can be processed by the beam current reference level control circuit.

Switching regulator with reduced inrush current

Abstract: A switching regulator for regulating an input voltage having an alternating current component Closure of the regulator switch is determined by a phase shifted switching signal obtained from a control network In normal operation a varying bias signal coupled to the control circuit varies the phase shift of the switching signal to vary the instant of regulator switch closure During startup, a capacitance coupled to the control circuit and to the input voltage provides an additional bias signal to delay the switching signal to prevent regulator switch closure during the peak magnitude of the alternating current input voltage component to thereby limit the peak inrush current in the regulator circuit

Welding power supply

Abstract: A square wave welding power supply system includes two constant current power sources. The first power source 10 is preferably an SCR controlled power supply having an output connected in an arc circuit 15 through an inverter circuit including SCR-1 through SCR-4 which controls the polarity and duration of the welding current applied to the arc circuit. The second power supply 20 is preferably a reactor power supply for supplying additional welding current during one polarity of the square wave. A shorting means (SCR-5) is connected across the output of the second power supply to maintain current flow therefrom during those intervals when the output of power supply 20 is not connected to the arc circuit. A gating circuit 30 controls the SCRs (SCR-1 through SCR-5) and commutation circuits (C-1 through C-5) connected across each SCR. A diode D1, or SCR, is connected in series with the second power supply output to prevent short circuiting of the arc by SCR-5.

Semiconductor strain gauge with temperature compensator

Abstract: A bridge circuit with four arms including semiconductor strain gauge elements has input terminals for coupling a DC power supply with a pair of diagonally opposite junctions of the bridge circuit per se and output terminals coupled with a pair of remaining diagonally opposite junctions. Initial zero-point temperature compensators each are connected in series and in parallel to each of semiconductor strain gauge elements on adjacent two arms of the bridge circuit. Temperature compensators for zero-point shift adjustment are each provided between the adjacent arms closer to each output terminal. A temperature compensator for span adjustment is provided between one of the input terminals and the DC power source. A constant current control unit for feeding a constant current to the bridge circuit is provided between the other input terminal and the DC power supply.

Efficient bipolar regulated power supply

Abstract: In a bipolar regulated power supply, two pass devices (transistors) are connected in a complementary symmetry circuit, one controlling the current from a positive voltage source and the other the current from a negative voltage source. One pass device connected in a first control loop is controlled by a source of input signals and feedback from the output terminal. A second control loop maintains a constant quiescent current in the two pass devices. In order to maintain this quiescent current in the presence of load current, a second feedback to the second loop, sensing load current, is provided.

Current unit for arc welding

Abstract: An a.c. operated arc welding current supply unit comprises a frequency converter of the series capacitor type and operating with a half period which is substantially less than the average duration of the current and voltage transients caused by short circuits through droplets of weld material during welding. The frequency converter is connected to welding electrodes through a transformer in series with a rectifier to provide direct current for the welding electrodes, and the frequency converter is associated with a control device for controlling the operating frequency of the converter in a manner such that it is substantially inversely proportional to the square of the input voltage of the current supply unit, thereby maintaining the power output of said unit substantially unchanged irrespective of changes in load caused by the welding operation and irrespective of variations in said input voltage.

Pulse generator for metal machining by electric discharges

Abstract: A pulse generator for metal machining by electric discharges, comprising a primary current circuit for producing and transmitting pulse forms to a pair of electrodes A voltage and/or current source is arranged in the low-ohm and low-loss primary current circuit, the voltage of which has a value which is only that much greater than the operating voltage of the pulses flowing through the spark gap as is needed to positively overcome the voltage losses occurring in the primary current circuit A signal generator produces a signal corresponding to the desired current pulse shape or form A comparator, which has a switch arranged in the primary current circuit for regulating the current flow in such primary current circuit, controls the current flowing through the primary current circuit, as a function of the desired pulse form produced by the signal generator and a magnitude of the current flowing in the primary current circuit which is tapped-off by a measuring feeler A magnetic energy storage arranged in the primary current circuit and having a switch in parallel to the work gap produces a voltage having a value greater than the voltage of the current and/or voltage source, and the primary current circuit is designed such that there is only present stray capacitance

Constant voltage circuit

Abstract: PURPOSE: To obtain a constant voltage circuit which is capable of free setting of the output voltage by installing the level shift circuit and the reference voltage generation circuit constituted by short-circuiting the source and the gate of depression MOSFET(DMOST). CONSTITUTION: Reference voltage generation circuit 4 gives a short circuit to the gate and source of DMOST2 to produce the constant current, and then supplies the constant current to MOS load 3 to deliver potential V 1 at connection point P 1 of MOS2 and 3. When the potential of output terminal 9 at the connection point of constant current MOS5 and load MOS6 is changed from 0 to power voltage VSS, the current flowing through MOS5 and that flowing through MOS load 6 become as shown by curve c and d respectively. And potential V 2 at intersection Q 2 of curves c and d becomes the output voltage of terminal 9 in level shift circuit 7. The output voltage V 2 sufficiently higher than output voltage V 1 of circuit 4 is delivered from circuit 7, and at the same time current I 2 flowing through MOS5 is sufficiently more in amount than current I 1 flowing to MOS2. As a result, a sufficient amount of power can be supplied to the load. In the same way, voltage V 3 corresponding to intersection Q 3 between curves c and e can be obtained from output terminal 8. COPYRIGHT: (C)1980,JPO&Japio

Channel selection voltage generator

Abstract: A channel selection voltage generator comprises a tuning voltage generator circuit having a capacitor for supplying a tuning voltage to an electronic tuner, a first constant current source for constantly discharging the capacitor at a first constant current and a second constant current source adapted to be rendered selectively in an operative state and in an inoperative state for selectively charging the capacitor at a second constant current which is higher than the first constant current, a frequency discrimination circuit for producing a discrimination signal representative of the amount of frequency deviation when a tuning voltage deviates from a receiving frequency, a buffer circuit for producing a binary "1" level signal when the discrimination signal is higher than a predetermined value and producing a binary "0" level signal when the discrimination signal is lower than the predetermined value, and a control circuit for causing the second constant current source to assume the inoperative state when the binary signal is at "0" level and causing the second constant current source to assume the operative state when the binary signal is at "0" level, the control circuit serving to maintain the second constant current source in the operative state or the inoperative state irrespective of the level of the binary signal during the frequency sweep.

A circuit for the measurement of instantaneous temperature in heated turbulent flows

Abstract: Measurement of the instantaneous temperature in heated turbulent air flows has often been carried out with cold-wires operating at a constant current supplied by an electronic circuit. A new electronic circuit for such a resistance thermometer offering simplicity with good accuracy, has been developed. The advantages over previous configurations are low voltage drift and simple construction and operation. The circuit is described in detail and measurements in a heated homogeneous shear flow are provided as an application.

Electronic fuel injection control employing gate to transfer demand signal from signal generator to signal store and using discharge of signal store to control injection time

Abstract: An electronic fuel injection system includes a mass flow transducer, an integrator which periodically accumulates a signal corresponding to the total mass of air aspirated into the engine during a preceding fraction of an engine cycle, a signal storage capacitor which is charged periodically to the integrator output voltage under the control of an analog gate, a controlled current source normally giving a constant current, but overridingly controllable by the integrator output at extremes of the range of the integrator output and connected to discharge the capacitor and a comparator sensing the voltage on the capacitor and controlling the length of time for which the injector is open.