Showing papers on "Constant current published in 1981"

Method and apparatus for transcutaneous electrical stimulation

Abstract: A method and apparatus for monitoring and obtaining actual bio-electrical characteristics of a subject under predetermined conditions of evoked response stimuli, and by interaction with a computer, applying cutaneous electrical stimulation to the subject, using a signal generator to modify current amplitude and frequency in a direction to achieve bio-electrical characteristics in the subject related to the actual bio-electrical characteristics monitored. The signal generator uses a sinusoidal waveform output, with battery power passed through a transformer to power a transconductance amplifier to obtain constant current output despite resistance changes in the line with the subject, and with the transformer not placed in the signal path of the sinusoidal waveform. The signal may be obtained from a sinusoidal oscillator of wide frequency having switched integrator sections connected to an inverting amplifier, pulse generator and gating.

Oscillator having capacitor charging and discharging controlled by non-saturating switches

Abstract: An oscillator which includes a DC voltage source, a differential amplifier having a hysteresis characteristics, a current source circuit producing a predetermined constant current, a current sink circuit flowing therein substantially one half of the predetermined constant current, and first and second current switching circuits controlled by the output of the hysteresis amplifier to charge/discharge a capacitor by the current from current source/sink circuits, thereby to produce an output pulse signal.

Transient Stability Analysis of Multi-Machine AC/DC Power Systems Via Energy-Function Method

Abstract: In this paper, the direct method of stability analysis using energy functions is applied for single and multi-machine AC/DC power systems. The system loads including the terminal characteristics of the DC link are represented as constant current type loads, and their effects on the generators at the internal nodes are obtained as additional bus power injections using the method of distribution factors, thus avoiding transfer conductance terms. Using the center of angle formulation, a modified form of the energy-function method is used for the swing equations and the DC link dynamical equations to compute the critical clearing time for a given fault. Numerical results of critical clearing time for a single and multi-machine system using the energy-function method agree well with the step-by-step method.

Automated alternating polarity direct current pulse electrolytic processing of metals

Abstract: Disclosed is a method and apparatus for electrolytic processing of a metal surface which, in a preferred embodiment, is anodization of an aluminum or aluminum alloy surface. An apparatus and method is provided which automatically senses the process voltage applied to the surface to be anodized and adjusts the duration of anodizing current pulses accordingly. Direct current anodizing pulses are interrupted by non-anodizing pulses which may be either zero current or reverse current pulses. The ratio of anodizing to non-anodizing pulse power is varied during anodizing such that the anodizing to non-anodizing time power ratio is reduced. In a preferred embodiment, a microprocessor follows the process voltage necessary to maintain a constant current flow to the metal surface and reduces the anodizing to non-anodizing time power ratio in a predetermined manner.

Electrically induced osteogenesis: relationship between charge, current density, and the amount of bone formed: introduction of a new cathode concept.

Abstract: A study was performed exploring the relationship between charge, current density, and the amount of new bone formed in the medullary canal of the intact rabbit tibia. The results indicate that the amount of bone formed in the vicinity of a cathode is directly related to both current density and charge. Utilizing stainless steel cathodes delivering a constant current of 20 muamps, the optimum current density was found to be 1.06 X 10(3) muamps/mm2 and the optimum charge, 36.29 coulombs. The amount of bone formed with pulsed current approached that formed with constant current only as the total charge delivered by the pulsed current approached that delivered by the constant current. Based on these findings, a new cathode is designed with eight active ports evenly distributed along its length and providing two and one-half times the amount of bone formed by a conventional cathode. This cathode is now in the early stages of clinical evaluation in patients with acquired nonunion.

Pulse arc welding method and device in which pulse current and background current have a constant current characteristic

Abstract: A pulse arc welding device includes a power source which produces a background current and pulse current imposed on it. A voltage drop across the arc is measured and when such a voltage drop deviates from a predetermined level, either one of background current, frequency of the pulse current and pulse duration of the pulse current is controlled to maintain the voltage drop across the arc constant.

Solid-state load protection system having ground fault sensing

Abstract: A solid state load protection system whereby the current supplied to a load is monitored enabling ground fault sensing to be used. A current sensor is utilized so as to produce an output current which is proportional to the current in the electrical circuit. Attached to the current sensing function is a resistive load which converts the current produced by the current sensing function to a voltage which is also proportional to the current utilized by the motor. Attached between two resistors which comprise the resistive load is a ground fault resistor which has its remaining end connected to the neutral leg of the current transformers of the current sensing function. The ground fault sensor monitors the voltage across the resistors in the resistive load and the current in the neutral leg of the current sensors. A ground fault condition is indicated when a current in the neutral leg of the current sensor is detected and thereby causes voltages across each of the resistive load resistors to be unequal to each other. If this condition is in excess of a predetermined level, for a predetermined period of time a trip signal to the output function is initiated, in turn causing a light-emitting diode to conduct and indicating a ground fault condition. The output function upon receiving a trip signal causes a second light-emitting diode to conduct and also de-energizes a contactor through which a current source is connected to a load.

Temperature detecting device

Abstract: A temperature detecting device comprises a semiconductor diode temperature sensor having a resistance characteristic which varies with variations in temperature, and a constant current circuit connected in series. A power source is connected in parallel with the series circuit and connected in parallel with a constant voltage circuit. A resistance ladder circuit is connected between an output terminal of the constant voltage circuit and one terminal of the power source, and an output terminal of the resistance ladder circuit is connected to a first input terminal of a differential amplifier. A second input terminal of the differential amplifier is connected to a connection point of the semiconductor diode and the constant current circuit. In operation, the voltage drops across cumulatively successive resistors of the resistance ladder circuit are compared with the voltage drop across the semiconductor diode temperature sensor by the differential amplifier and in response to a favorable comparison, the output logic state of the differential amplifier changes to thereby provide an output temperature signal.

Solid state digital-to-analog converter

Abstract: A digital-to-analog converter comprising an IC switch module providing four switch transistors and associated switch-control buffering circuitry. The emitter areas of the switch transistors are binarily weighted to provide equal current densities. The IC substrate also is formed with a fifth transistor to serve as a reference transistor for adjusting the supply voltage as necessary to maintain constant current through the switch transistors. To construct a digital-to-analog converter having a high bit resolution, a number of such "quad" switch modules may be combined, for example in a printed circuit card assembly including a thin-film resistor module providing binarily-weighted resistors on a glass substrate to set the current levels through the switch transistors.

Hot wire type arc welding device

Abstract: PURPOSE: To make the reduction in size at a low cost possible by flowing wire heating current and arc current from one unit of an electric power source by the use of transistors CONSTITUTION: Arc current I 1 flows in a route of an electric power source 13, a transistor TR 1 , base materials 3, a molten pool 8, a non-consumable electrode 1 and a shunt 18, and generates the arc 4 Wire heating current I 2 flows in the route of the power source 13, a transistor TR 2 , a power feed tip 7, a wire 5, the pool 8, the arc 4, the electrode 1, and the shunt 18, and heats the wire 5 These currents are controlled by the TR 1 , TR 2 so that the applied voltage V for wire heating of constant voltage characteristics and the full arc current I 0 of constant current characteristics are obtained COPYRIGHT: (C)1983,JPO&Japio

Telephone line feed

Abstract: The direct current line feed for a telephone subscriber's line is derived from a variable voltage source connected to the line. In one case, the source is series connected in one leg of the line while in the other case it is connected across the line. In the first case there is a constant current source across the line while in the second case the voltage source is a constant current device. In both cases a pair of matching resistors is connected across the line with the center tap grounded to provide a high resistance balanced termination for the line. In both cases a high impedance monitor is connected across the line to monitor the voltage conditions on the line, and this, via a control circuit controls the voltage source and the separate constant current device if provided. This enables line voltage to be adjusted to take account of line length without introducing undesirably large dissipation.

Current mirror arrangement

Abstract: A current source arrangement which may be constituted by a current mirror or by a multiple current source, having a first current circuit and a second current circuit, each equipped with a semiconductor device in series with a resistor. For the purpose of noise reduction the difference between the voltages across the two resistors is negatively fed back to the second current circuit.

Demand reduction system for regulated electric utility distribution circuits

Abstract: A circuit for automatically introducing a component of negative resistance line drop compensation into the control circuitry of a conventional voltage regulator to reduce the regulated voltage level on and, consequently, the load current level in a single phase primary electric distribution circuit during periods of peak load. The subject circuit automatically removes the negative resistance component from the regulator control circuitry during off-peak periods when the energy demand or loading on the distribution circuit is relatively low. A current transmitter is connected to a current transformer of the regulator to sense when the distribution circuit load current increases to a first predetermined level at or near peak load levels whereupon the transmitter actuates switching circuitry to introduce the negative resistance component into the regulator control circuitry after which the transmitter deactivates the switching circuitry to remove the component from the regulator control circuitry when the distribution system load current decreases to a second predetermined level below the first level. A switching circuit for demand reduction on a three phase electric distribution circuit is also disclosed.

Field effect current mode logic gate

Abstract: Disclosed is a field effect current mode logic gate comprised of a current source for supplying a constant current, and a differential amplifier having first and second branches for passing respective portions of the constant current. The first branch includes a plurality of parallel-coupled or serially-coupled enhancement field effect transistors having a positive threshold voltage and having respective gates for receiving respective input logic signals; and the second branch includes a depletion field effect transistor having a negative threshold voltage, and a grounded gate. The magnitudes of the current portions in the first and second branches are representative of the magnitude of the input logic signals relative to the positive threshold voltage plus the absolute value of the negative threshold voltage.

Pulse arc welding method

Abstract: PURPOSE:To eliminate the over-thrust at the starting and to cause transfer to the arc in a short time by setting >=1 of the respective set values of the peak current, background current, pulse width and pulse frequency of the pulses at the arc starting larger than the set values in a steady time. CONSTITUTION:Before a wire 1 arrives at base materials 3, the pulse-like voltage of which only the set value of the background current is set larger than the set value in a steady time is applied to the wire and the wire feeding is started. When the wire 1 short-circuits to the base materials 3, the set value of the background current in particular is set larger and therefore the input heat to be applied upon the wire 1 is larger than that in the prior art, whereby the wire 1 is melt-cut easily and is transferred to the arc in a short time. In the case when the pulse width and the pulse frequency are increased similarly, the heat input upon the wire 1 is also increased and the wire 1 is easily melt-cut and is transferred to the arc in a short time. According to these methods, the wire feed troubles such as buckling of the wire owing to the failure in the arc starting are eliminated.

Non-dissipative battery charge circuit

Abstract: A non-dissipative battery charging circuit utilizing pulse width modulated constant current charging signals and having unregulated charging voltage stepped down by the use of a switching transistor and series inductor is described. Charging current is sensed and fed back to cause control of the charging cycle. Battery voltage is sensed and compared to a reference level for terminating charging when the battery is determined to be fully charged. A clocking and control system responsive to the feedback signals and the sensed voltage levels is described for controlling the activation and duration of application of charging current signals.

Solid state control for motor-generator welder.

Abstract: A solid state control circuit (30) is connected to the output of an engine (14) or motor driven alternator (12) to provide a direct current output primarily for welding purposes. The control circuit (30) includes gate controlled thyristors (SCRs) (25) which are gated on at precise times within each cycle in order to provide an output having desired characteristics, such as constant current or constant voltage. Synchronizing windings (Fig. 3) associated with the alternator provide signals (36) used to control the time of gating for the SCRs. Circuit means (60, 70, 75) are included to insure that the control signals will be unaffected by any disturbances generated within the synchronizing signals due to the operation of the SCRs, and one such means includes an amplifier (U-7) having a feedback circuit (R48) providing a hysteresis greater than any voltage change in the synchronizing signal caused by the operation of the SCRs.

Rechargeable flashlight combined with a constant current battery charging circuit

Abstract: Apparatus for charging rechargeable batteries includes a constant current regulator connected in combination with a current limiting resistor to provide constant current for charging the rechargeable battery and a pair of light emitting diodes are used to indicate the charging status of the rechargeable battery.

Method for determining current efficiency in galvanic baths

Abstract: A method for determining current efficiency in a galvanic bath employs a measuring cell within which a sample is introduced from the galvanic bath. In this sample, onto a preferably rotating electrode metal is precipitated. A negative voltage is applied at constant current during a first predetermined time during the precipitating. Thereafter, the precipitated layer is anodically eroded by use of a suitable electrolyte solution upon pole-reversal of the DC voltage. The current efficiency is then calculated.

Glow plug control system for a Diesel engine

Abstract: A glow plug control system which includes a controller connected to a battery through an ignition switch, an indicator lamp and a glow plug relay connected to the controller and a parallel combination of four glow plugs connected to the battery through normally open contacts of the relay. The controller includes a comparator having its two inputs connected across the parallel glow plugs, and a constant current circuit for supplying a constant current to the parallel combination of the glow plugs for sensing the resistance of the glow plugs. The controller senses the resistance of the glow plugs due to their temperature through the comparator and permits the battery to supply a current to the parallel combination of the glow plugs for a time determined in response to the sensed resistance.

Constant energy transfer rate strobe source

Abstract: A strobe light power source transfers a constant amount of energy to a capacitor bank for each flash of a strobe lamp by maintaining a constant energy transfer rate between a power source and the capacitor bank and allowing the capacitor bank to charge for a set period of time. The effective value of the input current to a charging circuit connected between the power source and the capacitor bank can be maintained at a constant value to provide an approximately constant energy transfer rate. Such constant current control is most effective for a source having a relatively constant output voltage. In sources where the output voltage varies over time, both the input current and voltage to the charging circuit are monitored, combined and integrated to generate a duty cycle output signal which controls the charging circuit. A timer circuit is provided to set time periods during which the capacitor bank is charged at the constant rate to provide constant energy for each flash of the strobe light. The timer circuit can trigger or activate the strobe lamp and also prevent recharging of the capacitor bank for afterglow protection of the strobe lamp.

Self-powered ammeter

Abstract: A self-powered ammeter is disclosed. A metering circuit receives an a-c current to be tested and then generates a d-c voltage whose magnitude is proportional thereto. A display circuit receives the d-c metered voltage and provides a visual indication of the magnitude of the measured current. The current to be measured also drives a current transformer which, in turn, has an output burden circuit which produces a regulated power supply for the metering and display circuit components.

High frequency line ripple cancellation circuit

Abstract: In circuits such as voltage regulators and the like where parasitic currents may be generated as a result of high frequency ripple on the supply line, means are provided to cancel the effects of the parasitic current. A capacitor having a capacitance substantially equal to the parasitic capacitance is adapted to receive the supply voltage excursions and generate a current substantially equal to the parasitic current. A current mirror circuit or the like is employed to either divert this second current from the base of the output transistors or to reduce the drive current to the base of the output transistors by an amount equal to the second current.

Dc arc welding device

Abstract: PURPOSE: To perform stable arc welding with less spatters in all electric current ranges by selecting the plural time delaying elements provided in an arithmetic circuit in accordance with output currents. CONSTITUTION: The set signal for output voltage from an output voltage setter 10 and a feedback signal for output voltage are compared and amplified in an amplifier 12. If the output signal of the amplifier 12 is small (if the output current is small), the terminal voltage of a resistor 19 is small and a transistor (TR) 21 does not conduct. Therefore, an arithmetic circuit 11 deals with the abrupt fluctuations in the feedback signal with the time delay determine by a capacitor 16, thus making the rising characteristics of the output current relatively acute. On the other hand, if the output signal is large, the terminal voltage of the resistor 19 increases and the TR21 conducts. The arithmetic circuit deals with the abrupt fluctuations in the feedback signal with the time delay determined by capacitors 23 and 21, thus making the rising characteristics of the output current relatively gentle. The rising characteristics of the output current are changed at arbitrary points by regulating the resistance ratios between the resistors 19 and 20 in the above-mentioned way. COPYRIGHT: (C)1983,JPO&Japio

Bipolar linear current source driver amplifier for switching loads

Abstract: A circuit for driving an electrical load such as an electric motor, by a pulse width modulated current includes a saturable current driver connected to the load. The circuit includes a linear transconductance amplifier with current-sensing feedback for applying a pulse-width modulated control current to the driver. The feedback preserves the extent of saturation and of cut-off by providing current pulses which are invariant with respect to thermally induced changes in circuit parameters. Amplitude and offset control circuitry are also provided for setting the range of current values during the current pulsing to optimize the operation of the driver. In an alternative simplified circuit, a low-level switching circuit drives complementary output transistors operating in a linear fashion, and producing current pulses which are invariant with respect to the saturable driver parameters.

Ground fault interrupter circuit

Abstract: A ground fault interrupter (GFI) circuit for interrupting alternating current delivered in a power distribution system whenever a ground fault current exceeding a prescribed level is sensed. The GFI circuit includes a differential current sensing apparatus for sensing the presence of a ground fault current and generating a control signal that assumes a first condition whenever the ground fault current exceeds the prescribed level and for assuming a second condition whenever the ground fault current is less than the prescribed level. A charging circuit is charged with an electrical charge during a fixed portion of each cycle of the alternating current if the control signal has assumed the first condition. If the control signal has assumed the second condition, the charging circuit is discharged during a fixed portion of each cycle of the alternating current, thereby preventing any substantial charge from being stored in the charging circuit. A trigger circuit generates a trigger signal whenever the accumulated charge in the charging circuit exceeds a threshold level, which threshold level is reached within one cycle of the alternating current. Conventional switch means are used to interrupt the current flow in the power distribution system in response to this trigger signal.

Transistor circuit for reducing gate leakage current in a JFET

Abstract: A transistor circuit is provided comprising a primary JFET whose gate leakage current is required to be minimized, and a reference current generator means connected to the source of the primary JFET for deriving a drain-to-source current to be applied to the source of the primary JFET. The drain-to-source current has a value which forces the gate leakage current to be minimized. The reference current generator means comprises either a trimmed adjustable current source, a current source JFET, or a scaled reference source. These current devices are connected to the source of the primary JFET either directly or through a current mirror means to minimize the gate leakage current of the primary JFET.

Ignition coil energizing circuit

Abstract: An ignition coil energizing circuit is provided which has a signal generator for generating an output signal having a frequency corresponding to an engine rotational speed, a switching circuit connected to an ignition coil, a current detector for detecting a current flowing through the ignition coil, a duty control for supplying to the switching circuit a control signal having a duty cycle corresponding to a duty cycle of an output signal from the signal generator and controlling a conduction state of the switching circuit, and a current control circuit for controlling the switching circuit in response to an output signal generated from the current detector and maintaining a current flowing through the current detector at a predetermined value. The ignition coil energizing circuit also has a timer for generating an output signal when the switching circuit is detected to be on over a predetermined period of time and a current supply circuit for supplying a gradually increasing current to the current detector in response to an output signal of the timer.