Showing papers on "Constant current published in 1987"

Determination of biomass

Abstract: Apparatus for the determination of biomass in a suspension and its use in a fermentation apparatus. The apparatus comprises electrodes to be placed in the suspension and the following other components: a) means for applying an alternating voltage between the electrodes; b) means for providing a current signal indicative of the current in the current electrode circuit; c) means for providing a voltage signal indicative of the voltage between the voltage electrodes; and d) means for determining the ratio between the value of the voltage signal and the value of a quadrature component of the current signal, or vice versa, to provide a capacitance dependent signal.

Method and device for controlling a short circuiting type welding system

Abstract: A method and device for controlling a power supply for arc welding in a manner to reduce spatter when the power supply is employed for depositing metal from a welding wire or electrode onto a workpiece by the short circuiting transfer mode wherein a welding current causes the welding wire to alternate between a short circuit condition and an arc condition with metal transfer occurring during a short circuit condition. This method and device includes the concept of shifting the welding current to a background current value in response to a short circuit condition, holding the welding current generally at the background current level for a preselected time, then allowing the welding current to reach the normal unimpeded current level, and causing the holding step to be terminated before the selected time in response to a detected arc condition. This concept provides a predetermined low current condition immediately upon establishing a short circuit between the welding wire or electrode and the workpiece, which low current condition is retained long enough to convert what otherwise would be a spatter-laden momentary short circuit to a short circuit where metal is transferred to the workpiece. Further, the method and device detects the slope of the welding current or voltage and shifts the welding current to the low background current level when the welding current reaches its maximum value just before breakage of the metal from the wire thus reducing the spatter energy when the molten metal breaks from the wire.

Electronic ballast circuit for fluorescent lamps

Abstract: An electronic ballast circuit for fluorescent or other gaseous discharge lamps includes a resonant half-bridge inverter circuit. The source voltage to the inverter is a full-wave rectified line voltage together with a DC carry-over voltage for supplying power in the inter-cusp period of the recitified line voltage. A negative feedback circuit is responsive to lamp current to vary the inverter drive frequency and thereby regulate lamp current. The frequency response of the feedback loop is high enough and the gain-versus-frequency response of the inverter is such that lamp current and voltage are regulated to reduce the crest factor of lamp current to compensate for variation in the amplitude of the voltage across the semi-conductor switches.

Electropneumatic transducer system

Abstract: A temperature compensation circuit is provided which can be used for span temperature compensation in an electropneumatic transducer system and which includes a constant current generator circuit coupled to a bridge of piezo resistances in a pressure transducer to supply a constant current through one piezo resistance of the bridge to common. The Electropneumatic Transducer System includes a zeroing circuit, a voltage chopping circuit, a linearity correction circuit, a low-current shut-off circuit, and a high-current shut-off circuit to provide hard turn-ons and hard turn offs of the system at the lower and upper ends of the pressure output range or span. The Electropneumatic Transducer System also includes a voltage railsplitting circuit arrangement to minimize the operating currents and voltages. With these features, the Electropneumatic Transducer System is particularly adapted for use in hazzardous combustible atmospheres where Intrinsic Saftey and accuracy are required.

Controlled switching CMOS output buffer

Abstract: An output buffer initially operating its output transistors in a constant current mode in response to an input signal transition and subsequently operating its output transistors in a constant voltage drive mode as the output approaches the desried output level. The control electrode of the output transistor is controlled by a switchable voltage divider or current mirror. The control of an output transistor may not be activated until the other output transistor is turned off to prevent having both output devices on at the same time.

Analog-to-digital converter

Abstract: PURPOSE:To ensure the excellent differential linearity even in case the clock frequency is increased to increase the converting speed, by delaying the start time point for discharge of a constant current within a prescribed range of the clock number and subtracting the number of delayed clocks from the count value of a counter. CONSTITUTION:A waveheight/time converting means 2 consists of a sample holding circuit 2a incorporating a charging/discharging capacitor, a peak zero detecting circuit 2b, a constant current discharge control circuit 2c, etc. which are combined together. while a discharge start delaying means 6 contains an offset counter 6a which decides periodically the number of clocks to delay the start time point of discharge of the constant current set by the means 2 and delivers successively these decided clock numbers and a delay counter 6b which delays the start time point for discharge of the constant current by an amount equal to the number of clocks indicated by the counter 6a. A substractor 7 subtracts digitally the number of delayed clocks from the count value of a counter 5.

Low-voltage, temperature compensated constant current and voltage reference circuit

Abstract: The reference circuit includes a current mirror for providing first and second current paths for the conduction of respective first and second currents. The current mirror imposes a current level relationship between the first and second currents. A load, preferably resistive, is provided in the first current path for predominantly establishing a predetermined level of the first current. A transistor having a temperature coefficient of a predetermined polarity and a resistor having a temperature coefficient of a complimentary polarity are provided in the second current path for providing temperature compensation. Finally, a load compensation stage is provided in the first and second current paths to provide a thermal compensation feedback path from the transistor and resistor compensation elements to permit stabilization of the first current level with respect to temperature.

Wide dynamic range a.c. current sensor

Abstract: Various combinations of three elements are disclosed for use in accurate measurement of power through current measurement over a wide dynamic range, namely, a current shunt which is preferably an isothermal current shunt, a current transformer, which is preferably a high initial permeability current transformer, and a low-impedance burden load, which in the preferred embodiment includes an active negative impedance element which causes the removal of the effects of excitation current by canceling secondary winding resistance of the current transformer. In a specific embodiment of an isothermal current shunt according to the invention, a very linear device is achieved by construction out of copper in such a manner that the poor resistance versus temperature coefficient of copper does not affect the accuracy of measurement. Specifically, the shunt is constructed in an unbalanced isothermal bridge configuration, so that heat-induced variations are suppressed. Further, a very small current transformer is used having a core optimized for high initial permeability.

Stabilized welding power source including a series-resonant current-regulated converter using a transformer having an air-gapped core

Abstract: A pulse arc welding power supply incorporating one or more series resonant converters (SRC) for converting D.C. power to A.C. power which is then rectified to supply welding current. Each series resonant converter includes a series resonant tank circuit consisting of a capacitor, an inductor and the primary winding of a transformer whose secondary winding supplies current to the welding arc. The undesirable secondary output capacitor of the prior art is eliminated, as all the capacitance in the series resonant circuit is located on the primary side of the transformer. Current sensors sense the ringing current in the resonant circuit and also the load current and produce respective feedback signals which are used to control the switching frequency of an SCR bridge in the tank circuit, thereby maintaining the welding current at a desired value. Inner and outer current regulating loops, including a ramp generator, compensate for non-linearity in the continuous conduction mode of the SRC by limiting the switching frequency of the SCRs. a fault-predicting circuit also further limits the switching frequency in the continuous current mode for additional protection.

Differential to single-ended converter

Abstract: A differential to a single-ended converter circuit includes linearizing PN junctions that compensate for input signal voltage loss in the input stage. A variable voltage source and a resistor are provided for adjusting the voltage produced across these junctions by varying the current through these junctions. The converter circuit also includes a shunt feedback amplifier for inverting half the differential output voltage so that it sums with the differential voltage of opposite phase to produce the single-ended output signal. The shunt feedback amplifier is operated at a constant current to minimize error voltages. Bootstrapping is employed to linearize thermal distortion of the PN junctions and means are provided for compensating for the resulting thermal distortion.

Feedback-controlled current output driver having reduced current surge

Abstract: An output pad driver circuit for an integrated circuit chip architecture incorporates a controllably switched current mirror circuit in the circuit path between an output pad driver input terminal to which a digital signal produced by the signal processing circuitry of the chip is applied and an output terminal from which an output signal produced by the output pad is produced. The controllably switched current mirror circuit is coupled to a reference current terminal to which a source of reference current is applied. Coupled between the input terminal and the current mirror circuit is a first switching transistor which controllably causes the controllably switched current mirror circuit to apply a controlled current to the output terminal in response to a prescribed change in the logic level of an input signal that is applied to the input terminal. A second switching transistor is coupled in a feedback path between the output terminal and the current mirror circuit, and causes the current mirror circuit to terminate the supply of controlled current to the output terminal in response to the voltage level at said output terminal reaching a prescribed threshold. A third switching transistor is coupled between the input terminal and the current mirror circuit, so as to prevent the current mirror from applying a controlled current to the output terminal until the state of the input signal undergoes the prescribed logic level change.

Current difference current source

Abstract: A current difference current source which provides a stable current as operating conditions change. Two MOS transistors operate as two current sources. A difference current is obtained by subtracting the two transistor currents. The two current sources are configured to vary similarly as conditions change, such that their difference remains constant. In the alternative the difference current is forced to decrease as current increases in the transistors, wherein a reverse compensated current is provided. The difference current is used to drive a current mirror which functions as a compensated current source.

Method for powering telephone apparatus and telephone apparatus powered directly from the telephone line without external power

Abstract: A telephone apparatus powered directly from the telephone lines without external power includes a current converter in which current from a telephone line is limited by a transistor, current-sense resistor, and optical coupler acting together as a constant current device. This limited current is then converted from direct current (d.c.) to alternating current (a.c.) at the primary of a current transformer by power switching transistors driven by a flip-flop which is in turn driven by a free-running constant frequency oscillator. The alternations are symmetrical and their period or timing controlled so the current transformer does not saturate, thus maintaining maximum efficiency of conversion. The transformer outputs, after being rectified and filtered, are isolated from the primary, and provide d.c. current to maintian the charge on a battery across one output and to power telephone circuitry within a telephone device connected to the d.c. outputs. An optical coupler acting as an isolated current switch turns the constant current device off and on to facilitate pulse dialing. The current converter boosts the low telephone line current to a higher current or voltage for use by telephone devices such as pay phones, key phones, modems, or other telephone line connected devices.

Family of noise-immune logic gates and memory cells

Abstract: A new family of memory cells and digital-logic gates use an enhancement-mode driver, a voltage-level shifter, and a current regulator to provide improved noise margins and large logic swings. The voltage-level shifter and the current regulator are connected in series between an input and the control electrode of the driver. The voltage-level shifter establishes a voltage drop which is independent of current, while the current regulator establishes a constant current in the series path to the control electrode which is independent of voltage. The driver is an enhancement-mode device, such as a JFET, MESFET, or BJT.

Constant current circuit

Abstract: A constant current circuit includes a first FET providing an input reference current flow, a second FET providing an output current flow and a non-linear impedance element connected between the drain and the gate of the first FET. By setting a parameter of the non-linear impedance element and a parameter of the first FET to have a specific relationship with each other, the output current can be maintained at a substantially definite value irrespective of relatively large variations of the input reference current.

Current limiter for constant current for switching driving devices

Abstract: The switching driving device with current limitation, operating reliably even with high switching frequencies, comprises a drive stage (10) receiving at the input a timing clock signal (MCl) at a preset frequency and generating at the output a drive signal synchronized with the timing clock signal, a power element (11) connected at the input to the drive stage, receiving therefrom the drive signal and generating a load supply signal, a load (14) fed by the power element, and a current sensor (16,17) generating an overload signal when the current in the load has reached a preset threshold. The current limitation is obtained through a memory element (21) connected to the current sensor (16,17) and disabling the drive stage (10) in the presence of the overload signal. In order to obtain a reliable operation, in the presence of the overload signal the drive stage is controlled at a switching frequency which is lower than the preset frequency of the timing clock signal.

Pulsed Current Electromigration Failure Model

Abstract: The electromigration failure rate in conductors carrying rectangular current waveforms is a function of temperature, stress current density, period, and duty cycle or total on-time. This study used constant current lifetests to determine activation energy and current density acceleration, and correlated this lifetime to that obtained during pulsed current stress. A time-average current density, JDC, has been determined in an Al1%Si metal system for current densities between 0.3 and 2.0 MA/cm2 and duty cycles between 20 and 100% at 500 kHz and 175°C. The median time-to-failure for a rectangular waveform was best expressed as t50 = Ao(JDC)-n eEA/KT for a duty cycle between 20 and 100% at 500kHz and 175°C.

Drive circuit for light emitting element

Abstract: PURPOSE: To eliminate the fluctuation of an optical output of a light emitting diode array by using a digital signal to control the output current of a drive circuit driving the light emitting element in multiple stages CONSTITUTION: Constant current control utilizes a current mirror circuit comprising a bipolar transistor TR 0 functioning as a reference component and a bipolar TRC functioning as an output component Reference currents I 0 ∼I n for controlling the output current are given by a digital current control signal, which is of n bits and the reference currents I 0 ∼I n corresponding to each bit differ from each other and the output current is specified by the sum of the said reference currents I 0 ∼I n The n-bit current control signal gives 2n-way of reference currents I 0 ∼I n and the output current is controlled in 2n stages of the same number Thus, the drive current correcting the optical output dispersion of the light emitting diode array LED is found out easily from the control range Thus, the unevenness in optical output is suppressed lower COPYRIGHT: (C)1988,JPO&Japio

Constant voltage generating circuit

Abstract: PURPOSE:To obtain a constant current generating circuit which is quickly restarted even though a cut-off state is caused by a sudden drop of the power supply voltage, etc, by adding a start circuit consisting of a depression type transistor CONSTITUTION:A MOS transistor Tr-T5 has its threshold value lower than that of a MOS Tr-T3 When a constant voltage generating circuit is normally biased, the Tr-T5 is nonconductive since the threshold value of the Tr-T5 is set less than that of the Tr-T3 If the constant voltage generating circuit is cut off by some reason, the gate-source potential of the Tr-T3 drops Here the gate-source potential of the Tr-T5 is set less than its threushold value and turned on Thus a current flows in a route of Tr-T3 T5 T2 and the bias currents are recovered with both Tr-T3 and T2 Then the constant voltage generating circuit is restarted

Station line interface circuit for a telecommunication network

Abstract: A telephone station subscriber line interface circuit for connecting a telephone subscriber station to a telecommunications transmission line comprises a loop current sensing circuit for providing an output signal proportionately representative of DC resistance in the telecommunications transmission line. A ring-side driving circuit is coupled to the loop current sensing circuit and is responsive to the output signal for providing an alternating current voltage source and a direct current voltage source to a transmit amplifier in periods of high constant DC resistance in the telecommunications transmission line, the ring-side driving circuit maintaining the output of the alternating current voltage source constant to the transmit amplifier and automatically transferring from a constant direct current voltage source to a constant direct current current source in the event of a decrease in the DC resistance in the telecommunications transmission line sensed by the loop curent sensing circuit.

Regulated deuterium arc supply system

Abstract: An improved power supply system of smaller size and lower cost than prior art supplies is described for starting and maintaining the running of a deuterium arc lamp at a constant current level; by use of switching circuitry with solid-state components the necessity of transformers, relays and timing circuits has been obviated with a resultant major reduction in size, cost and cooling requirements of the supply; an improved starting sequence lengthens lamp cathode life.

Voltage controlled oscillator and phase-locked loop using it

Abstract: A voltage controlled oscillator is provided which includes a pair of gain stages constituting a positive feedback path, a pair of buffer stages in cross connection with the gain stages, a pair of loads connected with the corresponding gain stages, each having a parallel connection of an active device resistor and a clamping diode, and a pair of voltage controlled current sources connected with the corresponding gain stages, for supplying constant currents to the gain stages. A timing capacitor is connected with the input sides of both voltage controlled current sources, and is charged or discharged by the constant currents from the current sources. The oscillator further includes a pair of variable bias generating means, connected with the corresponding buffer stages, for generating variable bias voltages are provided, each of which varies the bias voltage to be applied to the corresponding active device in accordance with the output of the corresponding buffer stage in such a manner that the bias voltage is properly set in accordance with the constant current value of said constant current source so as to set the on-resistance of said active device to a suitable value corresponding to the constant current value. With this arrangement the loop gain of the VCO is made constant regardless of the constant current value.

Low power differential ECL line driver

Abstract: A low power, differential ECL line driver has a switching network that applies a constant current source as the emitter load to only one of the output transistors at a time while applying a constant current source to the base of the other output transistor.

Magneto resistive current sensor with improved fidelity

Abstract: The present invention is a current sensor employing a magneto resistive sensor having high fidelity of output This current sensor includes a magnetic flux concentrator substantially encircling the electrical conductor having magnetic sensing, a magnetic device generating a magnetic field component along an axis offset from the principle axis, a magneto resistive device disposed in the magnetic sensing region, a constant current source supplying a predetermined constant current to said magneto resistive device, and a voltage sensing circuit connected to said magneto resistive device for measuring resistance by measuring a difference voltage induced by said constant current This measured voltage corresponds to the current through the conductor The magneto resistive device is formed as a Wheatstone bridge having a first and second pair of opposite terminals The constant current source provides a predetermined constant current whereby the change with temperature in the differential voltage between said second pair of terminals is equal and opposite to the change in voltage of the total bridge resistance with temperature and the change in the bridge offset voltage with temperature

Cyclic controlled electrolysis apparatus

Abstract: Method and apparatus for cyclic control of both potential and current in electrolysis, called Cyclic, Controlled-potential, controlled current Electrolysis. The method can be used with a two-electrode cell (W and C), or a three-electrode set-up using a reference electrode R to form two half cells. The method involves supplying a controlled current, preferably a constant current, to the W and C electrodes to operate the electrolysis within well-defined upper and lower potential limits. In a first embodiment (called the constant-current, preset-voltage mode), when a predetermined voltage is reached, the current is reversed until a second predetermined voltage is reached. The cycle is then repeated continously. In a second embodiment (called the preset-voltage, preset-time mode) the current is maintained constant until the predetermined voltage is reached. Then the voltage is maintained constant by reducing the current until a predetermined time of operation has elapsed. Then the current is reversed and the cycle repeats. In the case of both embodiments, the cell operates as above for a preset period of time after which the preset voltage and/or cycle time control is switched with respect to W and C electrodes, the role of the electrodes thus alternating over a longer time period. By this cyclic electrolysis method, improved removal in hemodialysis or peritoneal dialysis of urea, uric acid, creatinine and other wastes is achieved. Better electrode surface regeneration, which occurs sequentially while electrolysis is continuous, is obtained. Production of undesirable or toxic substances such as chloramine, hypochlorite, nitrogen oxides, cyanide, ammonia, and the like are prevented. No electrode poisoning is observed. Both in vitro and also in vivo electrolysis is achieved by the method and apparatus of the invention. Physiologic electrolyte balance can be maintained.

A method for connecting a plastic pipe end to a plastic welding sleeve

Abstract: By a method for connecting a plastic pipe end (4 and 4ʹ, respectively) to a plastic welding sleeve (1) a heater (3) of annealed expanded metal is initially mounted on the pipe end (4 and 4ʹ, re­spectively), whereafter the welding sleeve (1) is pushed over said pipe end. Subsequently the plastic welding sleeve (1) is pressed downwards to abut the heater (3) in question by means of a known clamping device and heat supplied from the outside. The heater (3) is then connected to a welding generator and a microprocessor measuring and controlling the current through the heater and the voltage across the heater (3) during the entire heating phase. During the first phase of the heating process the heater (3) is supplied with a constant current, and when the microprocessor registers that the increase in voltage per time unit has dropped below a prede­termined level corresponding to a specific temper­ature, said microprocessor computes the ohmic re­sistance of the heater corresponding to a desired predetermined final welding temperature. This final welding temperature is kept constant for a period thereafter. In this manner a method is provided for connecting a plastic pipe end to a plastic welding sleeve by means of an extensible heater. During the fully automatized welding operation this heater is situat­ed in the welding area, whereby a uniform distri­ bution of heat is ensured and results in a welding of high strength and quality.

Voltage regulator start-up circuit

Abstract: A start-up circuit for a voltage regulator having a first current mirror for providing start-up current and a second current mirror responsive to voltage output from said regulator for turning off said first current mirror when said regulator is close to regulation. The circuitry providing start-up current and the circuitry turning off the start-up current having substantially the same temperature coefficients.

Distributed channel-bipolar device

Abstract: A merged channel and bipolar device which exploits the distributed character of the device generates useful electronic characteristics by controlling the current and voltage inputs to the four or more terminals attached to the device, said electronic characteristics being useful for affecting the ac and dc current gain of the device, its transconductance, non-linearities, the electronic output characteristics as a function of input signals, electronic switching, gain control, output limiting, heterodyning, harmonic generation and voltage references. Other applications which employ non-linear behavior include distributed amplification of traveling waves, multiple methods for chemical sensing and other sensor applications. The device behavior can be strongly affected by the device's distributed nature with bipolar behavior and FET behavior substantially different in different regions of the device, and the onset and distribution of this heterogenious behavior being affected directly by the input electrical voltages and currents. Channel geometry and conductivity and gate shape (where a gate is employed) can be used to affect the desired electrical performance. Sensing applications can be affected by intentional modification of surface parameters such as surface recombination, velocity, and by choice of gate materials and gate shape where a gate is used. Applications of the device encompass electrical parameter generation useful for circuit applications. An example is the generation of an accurate reference voltage V thg and constant current values, and transducing and sensing applications for sensing chemicals, magnetic fields, forces, pressure, and other tranducing stimuli.

Precision current rectifier for rectifying input current

Abstract: A current rectifier is provided and generally comprises: a p-channel transistor and an n-channel transistor having common gates connected to ground and common sources connected to an input current Iin ; and a first current mirror with its input connected to the drain of the n-channel transistor, and its output connected to the drain of the p-channel transistor. The current rectifier preferably also includes a second current mirror with the drain of the p-channel transistor as an input to the second current mirror and the rectified output current Iout as an output of the second current mirror. If an offset to the rectified current is desired, a third current mirror having a bias or offset current as an input and the output of the second current mirror as an output may be included.