Showing papers on "Negative impedance converter published in 1984"

High-Frequency Resonant Transistor DC-DC Converters

Abstract: Transistor dc-dc converters which employ a resonant circuit are described. A resonant circuit is driven with square waves of current or voltage, and by adjusting the frequency around the resonant point, the voltage on the resonant components can be adjusted to any practical voltage level. By rectifying the voltage across the resonant elements, a dc voltage is obtained which can be either higher or lower than the input dc voltage to the converter. Thus, the converter can operate in either the step-up or step-down mode. In addition, the switching losses in the inverter devices and rectifiers are extremely low due to the sine waves that occur from the use of a resonant circuit (as opposed to square waves in a conventional converter); also, easier EMI filtering should result. In the voltage input version, the converter is able to use the parasitic diode associated with an FET or monolithic Darlington, while in the current input version, the converter needs the inverse blocking capability which can be obtained with an IGT or GTO device. A low-power breadboard operating at 200-300 kHz has been built. Two typical application areas are switching power supplies and battery chargers. The converter circuits offer improvements over conventional circuits due to their high efficiency (low switching losses), small reactive components (high-frequency operation), and their step-up/stepdown ability.

Ac current control system

Abstract: In an AC current control system for controlling multi-phase AC currents supplied from a power converter to a load, the currents are detected and coordinate-transformed into orthogonal two-axis current values i d , i q in a rotating coordinate rotating at an angular frequency ω, and then compared with the references. The deviations are used to determine two-axis voltage values e d *, e q *, which are coordinate-transformed into multi-phase voltage values determining the output voltages of the power converter. The system is characterized in that the voltage value e d * is determined not only from Δi d but also from the product of ω and Δi q , while the voltage value e q * is determined not only from Δi q but also from the product of ω and Δi d . This arrangement makes it possible to provide a voltage component corresponding to the voltage drop across the inductive component of the load which is 90° in advance of the current.

Apparatus for measuring impedance

Abstract: The apparatus comprises: a comparator for comparing the voltage at which the constant current pulses are being supplied to the load with an increasing reference voltage; a counter for counting the number of voltage pulses that are greater in magnitude than the increasing reference voltage over a sampling period; and signal processing circuitry for correlating the count of pulses over the sampling period with the impedance of the load required to generate that number of constant current pulses at the voltage required for same.

Balanced Feedback Oscillators

Abstract: The oscillator circuit comprises an amplifier having a pair of inputs, a positive feedback path producing a positive feedback ratio to one of the inputs, and a negative feedback path including a series resonant circuit producing a negative feedback ratio to the other of the inputs. The positive and negative feedback paths are independent such that the current in each of the paths can be adjusted independently. In this manner, a high Q multiplier effect is achieved. Also, the circuit has an output path which is separate from the input path so that a high output signal level can be achieved while maintaining a low current through the series resonant circuit.

Switched-capacitor circuit analog-to-digital converter

Abstract: A switched-capacitor analog-to-digital converter implements a conversion scheme involving execution of an algorithmic technique of successive-approximation comprising a number of iterations dependent upon the conversion resolution desired. The algorithm used requires analog processing to produce an output voltage that is two times the output voltage resolved to realize the previous bit. The "times two" function is realized by adding the voltage of the last iteration to itself (i.e., V+V=2V). This is accomplished by storing the output voltage resolved into the previous bit and separately storing a voltage corresponding to that voltage. Both stored voltages are then transferred to an integrator circuit which adds the two voltages and produces the output voltage to be resolved into the next bit.

Voltage-to-current converter circuit

Abstract: A voltage-to-current converter circuit for outputting a current accurately proportional to the input signal voltage, which converter circuit includes an operational amplifier for providing an output corresponding to a difference between the input signal and a feedback signal, and includes a feedback circuit for detecting the output current in the form of a voltage by making the output current flow through the reference resistor and for feeding back the detected voltage. Further, the feedback circuit includes a polarity inverting circuit which holds the voltage detected by the reference resistor and inverts the polarity of the voltage, and then feeds back to the operational amplifier.

Temperature compensated voltage reference

Abstract: A temperature compensated voltage reference circuit in which a compensation current is generated by establishing a current through a passive impedance element which varies with temperature in accordance with the transistor voltage equation. This current is proportionately reflected into the output impedance circuit associated with the voltage reference, where it compensates for temperature induced voltage variations. The passive impedance element is adjustable to correct for processing variations, and the compensation circuit requires no voltage supplies other than those typically provided for the reference circuit by itself.

Circuit for generating a temperature stabilized reference voltage

Abstract: A temperature-stabilized voltage is generated based on the positive temperature coefficient difference in the base-to-emitter voltages of a pair of transistors operating at different current densities and a negative temperature coefficient voltage developed from the base-to-emitter voltage of a transistor.

Design and operating experience of an ac-dc power converter for a superconducting magnetic energy storage unit

Abstract: The design philosophy and the operating behavior of a 5.5 kA, +-2.5 kV converter, being the electrical interface between a high voltage transmission system and a 30 MJ superconducting coil, are documented in this paper. Converter short circuit tests, load tests under various control conditions, dc breaker tests for magnet current interruption, and converter failure modes are described.

Integratable circuit for controlling turn-off voltage rate-of-change of non-regenerative voltage-controlled switching semiconductor devices

Abstract: An integratable circuit for controlling the turn-off time-rate-of-voltage-change of a non-regenerative power switching device (such as a field-effect transistor, an insulated gate transistor and the like) uses a single capacitive element, in conjunction with a first current source, to provide a ramp voltage generator which is operative only if a ramp generator terminal is disconnected from a circuit common potential. The circuit uses a second current source and a controlled-conduction device to provide a control electrode drive signal to the at least one power switching device, controlling the flow of current through a load from a unipolarity or bipolarity source. The voltage across the controlled-conduction circuit of the power switching device then active is applied in attenuated form to another input of the ramp voltage generator to control the load voltage time-rate-of-change during load current turn-off.

Remote, inductively coupled, transducer interface

Abstract: An exciter and detector circuit (A1, A2) is inductively coupled (18, 20) with a current conductor (B). The current conductor extends to a remote location at which it is inductively coupled (26, 30) with a remote transducer and encoder circuit (C1, C2). The exciter and decoder circuit supplies a square wave signal of a fixed frequency and amplitude across a primary winding (18) of the inductive coupler. After each half cycle of the square wave as the magnetic field in the inductive coupler is collapsing, a flyback voltage peak is generated which varies with the load applied to the current conductor. At the remote location, a voltage to frequency converter (40) converts variations in the output of the transducer into corresponding variations in a frequency signal. A load modulator (42) is connected with the voltage to frequency converter to apply a load to the rectifier at the frequency of the voltage to frequency converter. This causes the amplitude of the flyback voltage peaks to vary with an envelope frequency which is the same as the frequency of the voltage to frequency converter. A detector frequency to voltage converter (70) converts the envelope frequency into a voltage which varies in proportion to the envelope frequency, hence, to variations in the condition sensed by the transducer.

Intergratable load voltage sampling circuit for R.M.S. load average voltage control apparatus

Abstract: An integratable load voltage sampling circuit utilizes a plurality of current-mirrors. One of the current mirrors is switched into conduction during a load-current conduction time interval, while another current mirror operates during the entire source half-cycle during which the first current mirror is pulsed to conduct. The total current from the plurality of current mirrors is summed and compared to a reference level; the difference in magnitude between the sampled and reference values is integrated, with respect to time, to provide a load conduction-angle adjustment signal having a magnitude varying as the root-mean-square magnitude of the average load voltage.

Circuit for monitoring the position of electrodes

Abstract: To check the position of electrodes on an object which is to be treated, in particular with current supplied from a generator to the electrodes of electrical energy, an electrical test pulse periodically to the electrodes (6, 8) is applied, and the or at by the test pulse or in the transition impedance (10, 11, 12) between the electrodes (6, 8) resulted in voltage or current by means of an evaluation device (21) is checked, wherein a warning signal upon exceeding or falling below a predetermined limit value (22) is released.

Testing circuit of ad converter

Abstract: PURPOSE: To check the accuracy of an AD converter through digital signal processing by providing a digital-analog (DA) converter which outputs the input voltage of an AD converter to be tested, a counter circuit which outputs the input value of the DA converter, and the 1st and the 2nd arithmetic circuits which calculate an error CONSTITUTION: The output value of the counter circuit 1 is latched by latch circuits 4 and 5 successively every time the output value of the AD converter 8 increases by one LSB, and a subtracting circuit 6 calculates the difference between output values of the latch circuits 4 and 5 to find the quantity of variation in the output value of the counter circuit 1 corresponding to one LSB variation in the output value of the AD converter 8 The output value of the subtracting circuit 6 is compared with that of a comparator A which is set previously by a comparing circuit 7 to compare the quantity of variation in input voltage value with the one LSB variation in the output value at each input voltage point of the AD converter 8, thereby checking a differential nonlinear error COPYRIGHT: (C)1986,JPO&Japio

Load cell type weight measuring device and a sensitivity checking method thereof

Abstract: A load cell type weight measuring device includes a load cell which produces an output voltage corresponding to the weight applied thereto, an amplifier circuit for amplifying the output voltage of the load cell, and an A/D converter for converting an output voltage of the amplifier circuit to digital data. This weight measuring device further includes a rated voltage generating circuit for generating an output voltage equal to the output voltage generated from the load cell which is applied with a rated weight; switches for selectively connecting the load cell, the rated voltage generating circuit and the ground terminal to the amplifier circuit; and a microcomputer which gives control signals to the switches and inhibits the output data of the A/D converter from being supplied as effective weight measurement data when it is detected that the difference between two items of output digital data of the A/D converter, which are respectively obtained when the ground terminal and the rated voltage generating circuit are selected, exceeds a predetermined range.

Circuit arrangement for checking the position of electrodes

Abstract: A circuit arrangement adapted for checking the position of electrodes on an object includes a treatment generator for periodically supplying treatment energy and a test impulse independent of the treatment energy to the electrodes. A transfer impedance of a certain magnitude exists between the electrodes; a voltage is developed across, and a current flows through the transfer impedance as a result of the test impulse. An evaluator evaluates the magnitude of the transfer impedance, and includes a test circuit connected to the electrodes for accepting the voltage and/or the current developed across, and flowing through the transfer impedance, respectively, and a warning signal emits a warning signal upon the magnitude of the transfer impedance exceeding or dropping below respective predetermined limit values.

Digital-to-analog converter biasing control circuit

Abstract: A device for controlling the output voltage range of a digital-to-analog (D/A) converter of the type wherein the converter output voltage range is proportional to the magnitude of an applied bias current. The device comprises means to sample and store a selected converter output voltage, means to produce a variable current of magnitude proportional to the stored converter output voltage, and a source of constant current. The constant current and the variable current are summed and applied to the converter as the bias current. The converter output voltage range is dependent on the variable portion of the applied bias current which is in turn dependent on the stored, selected converter output voltage.

DC-DC converter having feedback type switching voltage converting circuit

Abstract: A DC-DC converter having a high conversion efficiency and stable output voltage. A constant current supply circuit, located between the output terminals of the converter, make it possible for the source current to decrease as a function of battery output voltage, resulting in lower current requirements for a lower required voltage boost and hence increased efficiency.

Self-oscillation type current sensor

Abstract: PURPOSE: To decrease the number of parts and to reduce the device in size on the whole by detecting a current through the self-exciting operation of a magnetic semiconductor circuit consisting of a magnetic core with high magnetic permeability and an operational amplifier. CONSTITUTION: When the operational amplifier 9 is saturated positively and a positive voltage Vs developed at a terminal 8, the amplifier 9 keeps on sending a positive saturation voltage Vs to excite the magnetic core 1. The magnetic core 1 decreases in magnetic permeability before magnetic flux density attains to a maximum level and the impedance of winding 3 also decreases; and the voltage at a terminal 3a is inverted into a negative voltage owing to the resonance between a capacitor 6 and the winding 3 and inputted to an uninverted input terminal 10b, so that the voltage at the terminal 8 is switched automatically to a negative DC saturation voltage -Vs. Similarly, the voltage -Vs is changed to +Vs and DC voltages ±Vc applied to the amplifier 9 develop voltages ±Vs alternately at the terminal 8 with a voltage signal induced at the winding 3, and the positive/negative period length ratio of the voltage waveforms is controlled with the current to be measured. COPYRIGHT: (C)1985,JPO&Japio

Controlled parallel converter plant

Abstract: The electrical converter or inverter plant comprises several converter modules arranged in parallel between a power supplying line and a power consuming line. Each converter module includes a power converting unit being controlled by a control circuit which monitors the current and the voltage applied from the module itself to the load line. All functions of the plant are completely distributed among the converter modules so that no central arrangement exists. To coordinate the operation of the different modules there is provided one common current (voltage) balance bus to which all the control circuits are connected. The arrangement is constructed so that the voltage on the common current (voltage) balance bus shall be proportional to the current (voltage) provided to the load line from the module which produces the largest load current (voltage). This is obtained in a simple manner by connecting each control circuit with the common balance bus via an idealized diode.

Inverter driver for X-Ray generator

Abstract: In a square-wave, pulse-width-modulated transistor inverter, each of the transistors is provided with a driver network for turning the transistor on and off in response to control signals from a microprocessor. The microprocessor receives its command signals from both the operator input and a voltage feedback circuit. Positive and negative controlled d.c. voltage levels are provided by a switch-mode power supply with the positive voltage being applied to a turn-on circuit and the negative voltage being applied to a turn-off circuit. In response to control logic signals, the turn-on network provides a positive voltage signal to the base of the power transistor to turn it off, and the turn-off network provides a negative voltage to the transistor base to turn it off. A phase-advance network is included in the turn-off circuit and a pull-down inductive means is included in the turn-off circuit.

Control device for a converter having a DC intermediate circuit

Abstract: A control arrangement for a converter is specified, which consists of a mains-powered converter (1), a DC intermediate circuit (3) and a self-powered converter (5), and supplies an asynchronous machine (6) with a variable voltage and frequency. The control device is used for continuous control of the machine voltage (U) according to the load torque applied to the machine (6), while the speed (n) of the machine (6) is controlled in a predetermined manner. The control device has a higher-level voltage controller (10) whose input receives desired values and actual values for the machine voltage (U) and whose output is connected via a lower-level current regulator (12) to a control set (16) for controlling the mains-powered converter (1). Used for rapid detection of load torque changes and, in particular, for preventing tipping of the machine is a dynamic switch-on element (17) whose input receives the actual value of the intermediate circuit voltage (Udcist) and whose output emits a dynamic additional signal (Udyn), corresponding to the timed derivation of the intermediate circuit voltage, to the input of the voltage controller (10).

Current/voltage converter

Abstract: PURPOSE: To offer a current/voltage converter having excellent frequency characteristic and linearity without generating a DC offset by constituting the converter with a transistor, the 1st and 2nd constant current circuits and a current voltage converting resistor. CONSTITUTION: A constant current I flows to a resistor 13 through a diode and an input current of a current mirror 11 becomes also I. When an optical signal 1 becomes a current signal and flows to an emitter of a transistor (Tr)10, an emitter current I e and a collector current I c are both I-I s . Since the prescribed current I is fed to a collector of the Tr10 from a current mirror 12, a current IR, that is, a current I s flows to a resistor 14. Thus, an output voltage V s is I s R. Since the impedance of the emitter of the Tr10 is small sufficiently, both the frequency characteristic and the linearity are improved and no offset voltage is generated. COPYRIGHT: (C)1985,JPO&Japio

A Resonant Type Constant Current Converter with Saturable Core

Abstract: This paper presents an improved circuit of a constant current device using series resonance. In the circuit already reported, an excessive increase in the output voltage appears and an overcurrent flows into the resonant circuit when the output impedance becomes high. In this circuit, these defects are removed by making use of saturable core for the inductor of the resonant circuit.

Bi-directional amplifier

Abstract: PURPOSE:To perform the stable working of a bi-directional amplifier without deteriorating the amplification degree by using a negative impedance to connect two signal sources showing approximate natures as loads and then using these two signal sources with each other as the loads for the negative impedance conversion. CONSTITUTION:Signal source impedances 38 and 48 are connected to signal sources 30 and 40 respectively of a bi-directional amplifier, and line impedances 39 and 49 are used to connect the sources 30 and 40 and a negative impedance 45. The impedance 45 has a structure of a 4-terminal circuit containing terminals a-d and contains an operational amplifier 50 having differential input terminals 51 and 52 connected to terminals (a) and (b). Thus a negative impedance converter is obtained. Then the sources 30 and 40 are used mutually as a load for negative impedance conversion to each other. This secures the stable working of a bi-directional amplifier with no deterioration of amplification degree.

Circuit arrangement for voltage control and voltage conversion, particularly of a solar generator

Abstract: The invention relates to a circuit arrangement for controlling the voltage of a generator having an at least partially current-impressing characteristic, particularly a solar generator (1) for outputting a voltage, transformed up to a desired level, to a load (8) with low source resistance or low source impedance. For controlling the voltage, a series two-step controller (2, 3, 7) with capacitive storage (3) is provided, the switch (2) of the two-step controller and the generator (7) being decoupled via a transformer (5) from the capacitive storage (3) and the load (8) which is connected in parallel therewith. The transformation ratio of the transformer (5) is selected in such a manner that a voltage having the desired high level is obtained at the output of the circuit arrangement. In addition, the switching frequency of the switch (2) and the capacitance (C) of the capacitive storage (3) are selected to be high enough for a low source resistance or a low source impedance to be present at the output of the circuit arrangement.

Method and apparatus for negative feedback of movement induced voltage in a loudspeaker

Abstract: The dynamic voltage of a dynamic loudspeaker (3) operated on a voltage-controlled current source (2) is fed back. A voltage proportional to the current is tapped and conducted via a network (4) which simulates the voltage drop across the impedance of the loudspeaker that is locked. Since the network consists of resistors, capacitors and operational amplifiers, a high simulation accuracy up to approx. 50 kHz is possible. The kinetic voltage results after subtracting the output voltage of this network from the speaker terminal voltage. A variant of the method consists in simulating only the linear part of the spring mass system of the loudspeaker by means of a network of the same quality and resonance frequency and coupling the resulting voltage back to the input. The resistance required for current injection can also be compensated for by current feedback. Another variant is to feel the impressed signal current at a high frequency, to query the movement voltage during the switch-off phase and to regenerate it by means of a low-pass filter. Rectangular sound pressure profiles up to approx. 3 kHz are achieved with a loudspeaker box with negative and mid-range channels. The dimensions of the box are kept very small. The mirror source of the woofer is also used.

Negative impedance converter

Abstract: PURPOSE:To extend the frequency usable for an NIC (negative impedance converter), by adding a small capacity of equivalent impedance produced with a definite gain of an operational amplifier for compensating the gain. CONSTITUTION:Resistors R1, R2, the operational amplifier OP-AMP, and a resistor RL for the NIC. If the gain of the operational amplifier is infinite ideally, an input impedance Zin is a negative resistance having a value of -R1RL/R2. The gain, however, is definite, then an inductance proportional to 1/GB is provided where the gain is GB/S. The impedance Zin is a value shown in an equation by connecting a capacitor DELTAC2 in parallel with the resistor R2 as shown in dotted lines. Thus, the inductance component is canceled by selecting a suitable value of the DELTAC2. The same result is obtained by connecting the capacitor in parallel with an input terminal AB.

Modelling and analysis of d.c.-d.c. converter using y-parameters

Abstract: This paper describes an impulse-response method to find the low-frequency y-parameters of d.c. to d.c. switching converters in both the continuous and discontinuous modes. Using an example of a forward converter, the applications of the y-parameters are illustrated by the determination of: the general equivalent circuit; the d.c. output voltage; the critical condition between continuous and discontinuous modes of operation; the equivalent circuit under steady state condition; the transfer function between small change in d.c. input voltage and the resultant change in d.c.output voltage; the transfer function between small change in duty cycle and the resultant change in d.c. output voltage. The y-parameter approach can easily be applied to other types of converter circuits. Its simplicity makes it particularly suitable for more complex types of converters