Showing papers on "Negative impedance converter published in 1988"

A comparison of half-bridge resonant converter topologies

Abstract: The half-bridge series-resonant, parallel-resonant, and combination series-parallel resonant converters are compared for use in low-output-voltage power supply applications. It is shown that the combination series-parallel converter, which takes on the desirable characteristics of the pure series and the pure parallel converter, avoids the main disadvantages of each of them. Analyses and breadboard results show that the combination converter can run over a large input voltage range and a large load range (no load to full load) while maintaining excellent efficiency. A useful analysis technique based on classical AC complex analysis is introduced. >

A self-terminating low-voltage swing CMOS output driver

Abstract: A CMOS output pad driver circuit is described that automatically series-terminates a driven line in the line's characteristic impedance. The circuit has advantages in speed, power, and size over conventional designs. The key idea is the use of emitter-coupled logic (ECL) compatible low-voltage swings for signaling, combined with the use of the driver transistor as both a switch and as a termination resistor. An on-chip measurement circuit dynamically adjusts the impedance of the driver to match the impedance of an external reference impedance standard, allowing the circuit to compensate for both chip and board level fabrication variations. >

The CMOS negative impedance converter

Abstract: The authors describe the negative impedance converter, a simple analog building block which can be readily implemented in CMOS. They present a circuit based on the inverse-function approach, providing precise temperature-compensated linear operation. Applications include single-pin crystal oscillators, zero-impedance current sensing, and wideband integration. Simulated and measured characteristics are in good agreement, and show that useful negative resistance can be obtained to over 10 MHz. >

Impedance measurement circuit

Abstract: A protection circuit for a defibrillator that prevents a defibrillator pulse from being generated if the impedance between the defibrillator's electrode leads is not characteristic of the impedance between a pair of defibrillator electrodes properly connected to the defibrillator. The impedance measuring circuit applies a current to the electrode leads and the resulting voltage is measured to provide an indication of the electrode's impedance. The current is applied between the electrodes at about 33 kHz to approximate the impedance between a pair of defibrillator electrodes during a defibrillation pulse. The output of the measurement circuit is converted to an 8 bit word by an analog-to-digital converter and read by a microprocessor which compares the measured impedance to various impedance values in order to either generate an enable signal for the defibrillator or display messages indicative of open or short circuited electrode leads or a patient monitoring electrode connected to the electrode leads. The impedance measurement circuit operates in either of two ranges which are selected by the microprocessor on the basis of the measured impedance values.

Cascaded resonant bridge converters

Abstract: A converter for converting a low voltage direct current power source to a higher voltage, high frequency alternating current output for use in an electrical system where it is desired to use low weight cables and other circuit elements. The converter has a first stage series resonant (Schwarz) converter which converts the direct current power source to an alternating current by means of switching elements that are operated by a variable frequency voltage regulator, a transformer to step up the voltage of the alternating current, and a rectifier bridge to convert the alternating current to a direct current first stage output. The converter further has a second stage series resonant (Schwarz) converter which is connected in series to the first stage converter to receive its direct current output and convert it to a second stage high frequency alternating current output by means of switching elements that are operated by a fixed frequency oscillator. The voltage of the second stage output is controlled at a relatively constant value by controlling the first stage output voltage, which is accomplished by controlling the frequency of the first stage variable frequency voltage controller in response to second stage voltage. Fault tolerance in the event of a load short circuit is provided by making the operation of the first stage variable frequency voltage controller responsive to first and second stage current limiting devices. The second stage output is connected to a rectifier bridge whose output is connected to the input of the second stage to provide good regulation of output voltage wave form at low system loads.

Power converter control circuit

Abstract: A control circuit for an a.c. to d.c. power converter, in which the load current of the power converter is detected and averaged, and it is added to the voltage control signal of the voltage control system which controls the converter output voltage to be constant, so that the converter control is less affected by the ripple of the load current.

Controller for instantaneous output current and/or voltage of 3-phase converter

Abstract: A control circuit for a 3-phase converter which is provided to control the 3-phase converter having an output filter provided with a current minor loop which controls an instantaneous value of the output current on the basis of a feedback signal obtained by converting the output current of the converter to d axis and q axis components by a synchronous revolutional coordinate system and a voltage major loop which controls the instantaneous value of the output voltage on the basis of a feedback signal obtained by converting the output voltage of the output filter to the d axis and q axis components; and realizes protection from overcurrent due to short-circuit of output.

Voltage level detecting circuit having a level converter

Abstract: A voltage level detecting circuit includes a resistance voltage divider, a level converter and an MOS driver arranged such that the detection characteristics are immune to temperature variations. The voltage divider has two resistive elements serially connected to each other to produce a divided voltage. The two resistive elements have different resistance variations to temperature change. The level converter has a threshold voltage and converts a divided voltage which is more than the threshold voltage from the voltage divider into a binary signal. The MOS driver produces a control signal on receipt of a binary signal from the level converter.

A novel frequency-domain model for a parallel-resonant converter

Abstract: A steady-state analysis of the parallel-resonant converter is presented using a novel frequency-domain model. Various circuit variables are determined by simple expressions for both the frequency and the phase control techniques, simplifying the steady-state analysis. The existence of a multiple conduction mode is pointed out. The variations of output voltage, turn-off time, output power, and converter efficiency are studied. >

Pipelined serial-parallel A/D converter

Abstract: An A/D converter of this invention includes a first A/D converter for A/D-converting the input signal and determining upper bits of the n-bit binary code, first and second sample-hold circuits, which are alternately switched each time the first A/D converter samples the analog input signal, for sampling and holding the analog input signal, in synchronism with a sampling timing of the first A/D converter, and a second A/D converter. The second A/D converter is constituted by a reference voltage generator for generating reference voltages, based on contents of the binary code obtained by the first A/D converter, a voltage comparator for comparing the reference voltage with a voltage value of the analog input signal held in one of the first and second sample-hold circuits, which sample and hold the analog input signal corresponding to the binary code, and an encoder for encoding a comparison result output from the voltage comparator and determining lower bits of the n bits.

Dynamic characteristics of the digitally controlled DC-DC converter

Abstract: The dynamic characteristics of the digitally controlled DC-DC converter is analyzed theoretically an experimentally. The stability condition and the indicial response for the changes of the input voltage and the load are defined as a function of the circuit parameters and variables of the digital control circuit and the power stage. By taking account of the overshoot or undershoot of the output voltage with the step changes of the input voltage and the load and of the ripple instability, the optimum PID (proportional-integral-derivative) coefficients of the digital control circuit are examined. >

Mos current mirror with high output impedance and compliance

Abstract: A circuit which employs a pair of MOS transistors operating at equal gate and sources voltages, and nearly equal drain voltages, to produce an accurately ratioed current mirror. The gate voltage of the transistor pair is controlled by a simple current mirror operating at a small fraction of the total output. The latter current mirror also functions as a wideband negative impedance converter. A comparable bipolar circuit is also discussed.

Salinity measuring system

Abstract: A salinity measuring apparatus utilizes a specialized probe with dual electrode pairs, one of the pairs being used to pass current through the electrolyte, while the other picks up voltage drop across a region in the electrolyte and feeds it back to the current producing amplifier, which adjusts the current output until a stabilized, predetermined voltage difference occurs across the voltage electrodes. The circuit which drives the current between the current electrodes produces a positive pulse, and an ensuing negative pulse, which are sequentially applied across the electrodes so that two separate measurements are made using pulses of opposite polarity to cancel out electrode polarizations. An amplifier circuit receives a pulse from the voltage source and applies it to the electrodes. A second amplifier circuit picks up a voltage across a voltage dropping resister in series with the resistance of the electrolyte between the current electrodes, and amplifies this voltage drop for outputting to a signal register and processing means. A polarity reversal system is used at the output of the second amplifying circuit so that all of the processed pulses which output from the system have the same polarity despite the fact that internally in the apparatus the polarity is reversed. The pulse is transferred to the first amplifier circuit by a capacity charged transfer technique so that the system is electrically isolated from the pulse generator, and a second capacity transfer at the system output isolates the system from the output signal register and processing device.

Temperature compensated voltage generator

Abstract: A temperature compensation circuit for a device with a voltage output affected by temperature in a predetermined manner and a null output for which the voltage is zero regardless of temperature comprises a voltage to current converter responsive to the generated voltage to produce a proportional current, a current generator comprising elements responsive to the temperature of the device to generate a pair of compensation currents varying therewith in a predetermined manner so that the ratio of the compensation currents embodies a desired temperature compensation, and a transconductance multiplier effective to multiply the proportional current by the ratio of the compensation currents to generate a compensated output current. It may further comprise a current to voltage converter responsive to the compensated output current to produce a compensated output voltage.

Variable duty cycle window detecting analog to digital converter

Abstract: A high resolution analog to digital (A/D) converter amplifies and filters a magnitude difference between a pulse width modulated offset voltage and an input voltage to produce an amplified filtered difference voltage, the duty cycle of offset voltage modulation being adjusted such that the magnitude of the difference voltage is within a narrow input voltage range of a recirculating remainder A/D converter. The amplified, filtered difference voltage is converted to representative digital data by the recirculating remainder A/D converter. A microprocessor, which controls the offset voltage, combines the result with the magnitude of the offset voltage to produce a comparatively high resolution digital representation of the input voltage.

Improved resonant converter with high conversion efficiency and low output impedance

Abstract: An improved resonant converter, designed so as to switch at zero current without using discrete elements and so as to eliminate the effect of asymmetries which may lead to the saturation of the transformer, by appropriately selecting the conduction time of the input switches and the time for which said switches are simultaneously open. The converter has high conversion efficiency and low output impedance.

Device and method for maintaining a voltage level in a control circuit

Abstract: A device and method for temporarily maintaining a voltage level in a control circuit for auxiliary devices in a textile spinning machine, winding machine or the like wherein the control circuit is connected to an intermediate direct current circuit that is in series between a line voltage and the drive motors of the machine. The method includes reversibly supplying current from the intermediate circuit to the motors and inversely supplying current generated by the residual inertial energy of the motors to the intermediate circuit. The supplying of reversible current is controlled in response to a drop in line voltage to maintain the voltage level of the intermediate circuit and therefore of the control circuit supplying auxiliary devices. The controlling includes sensing a drop in line voltage and generating and transmitting control signals to reversibly supply current. The device functions to perform the method by providing a two-way converter for supplying current to the motors under normal operation and reversibly supplying current generated by the residual inertial energy of the motors in response to a drop in line voltage, a sensing device senses a drop in line voltage, and another component generates control signals for transmitting to the two-way converter for reversing thereof.

Interrupter arrangement for high-frequency signals

Abstract: A PIN diode is in series in a high-frequency signal path between an input and an output, and is controllably biased either on or off by a control signal supplied thereto from the output of a control circuit in response to a command voltage. The control circuit derives the control signal from a positive voltage source when the diode is to be turned on and from a negative voltage source when the diode is to be turned off. The negative voltage must be a relatively high value, which can cause excessive power dissipation in the control circuit due to charging of the bypass capacitance present at the output terminal thereof for shunting high frequencies. To prevent that, the control circuit includes an overvoltage circuit which produces a short duration trigger pulse in response to change-over from the positive voltage source to the negative voltage source and which supplies a current pulse of brief duration for charging the bypass capacitance.

Parallel operation equipment for ac output converter

Abstract: PURPOSE: To suppress a cross current at the time of trouble of an apparatus, by applying the command value of a voltage major loop and that for the allotted load current of each converter as command values of a minor loop. CONSTITUTION: No.1 inverter 1 supplies a load 4 with power while operating in parallel with No.2 inverter 2 of the same constitution as that of the No.1 inverter 1 through a bus 3. The inverter body is switched at a high frequency and controlled by a PWM circuit 134. Also, the inverter body is provided with a current minor loop to send a control signal to the PWM circuit 134 in such manner that a fed-back output current coincides with a current command from a limiter 123. Then, an output bus voltage is added from a sensor 132 to the output of a current control 121, further PLL 130 makes a sine-wave voltage reference 129, and a voltage control 126 generates a correction current signal which the inverter is to output for correcting the deviation of output voltage from the reference 129. Thus, a cross current can be suppressed at the time of trouble of other converter. COPYRIGHT: (C)1989,JPO&Japio

Pulsed power supply device

Abstract: Pulsed power supply devices deliver one or more DC voltages, there being a distinction to be made between the basic types of isolating converter and forward converter. It is intended to produce both low (e.g. 5 volt) and high (e.g. 100 volt) DC voltages stably for various load fluctuations. It is proposed to provide an isolating converter circuit for producing the high voltage, whereas for producing the low voltage, a forward converter circuit has a transductor coil (L1) which is connected to a regulator (R2) which delivers a regulating signal for regulating the output voltage (U3) of the forward converter circuit. Power supply devices.

Improved differential 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.

Analysis and design of current-resonant converter

Abstract: A practical current-mode quasi-resonant forward converter circuit is analyzed. The authors show that the circuit constants can be determined from the constraints obtained from the analysis. A DC-DC converter is built to demonstrate the approach, and its characteristics are compared with those of a conventional forward converter. >

Efficient circuit implementations of current conveyors, negative impedance converters and nonlinear impedance converters using operational transconductance amplifiers

Abstract: This paper points out that a commercially available dual-operational trans-conductance amplifier package (CA3280) can be efficiently used as both positive and negative second-generation current conveyors, floating negative impedance converters and floating nonlinear impedance converters. In many situations, no other active devices are required to implement the above circuit functions.

Method for the electrical representation of a physical measured variable in the form of an impedance change

Abstract: The invention relates to a method in which a first physical effect variable has a consequent impedance change of a measuring impedance as measured variable, simultaneous compensation being carried out of undesired, superimposed impedance changes as a result of further physical effect variables, that is to say disturbances. The method is intended to deliver all the information required for measured value acquisition with a low expenditure and a high measuring accuracy. According to the invention, it is proposed that, apart from the actual active measuring impedance which is exposed to all physical effect variables, a second, passive measuring impedance is provided. The second, passive measuring impedance is advantageously connected in series with the first and is exposed only to the disturbances. The currents flowing across the two impedances generate a voltage drop, which corresponds to an external desired value, across the passive impedance. The difference between the two voltages across the active and the passive impedance corresponds to the measured value.

Electrical characteristics of SRO-miss devices and their applications

Abstract: The electrical characteristics of the Metal-Insulator-Semiconductor - Switch (MISS) device with Silicon-Rich-Oxide (SRO) as the semi-insulating material have been comprehensively studied at room temperature in an exploratory way. The SRO films were deposited by atmospheric pressure chemical vapour deposition (APCVD) at 650oC with SiH(_4) and N(_2)O reactant gases and N(_2) carrier. The react ant gas phase ratio R(_o) varying from 0.09 to 0.25 and the deposition time varying from 0.6 to 2 min. Some preliminary investigations on SRO-MIS devices were also carried out in order to understand the electronic process in the structure. Various parameters which governed the switching behaviour of an MISS were investigated. In general the switching characteristics are similar to those of the tunnel oxide MISS. The geometrical dependence of the switching behaviour in the tunnel oxide MISS has been extended to the present device by looking at the effects of electrode area, junction area, electrode perimeters and of a metal guard ring. Other effects, such as SRO deposition time, work function difference, gold doping, heat treatment, light illumination and film ageing were also observed. The dynamic characteristic of the device was studied using a double pulse technique. The characteristics of the three-terminal SRO-MISS were studied in both forward and reverse bias. The former exhibited a thyristor-like characteristic and the latter a transistor-Hke characteristic. A preliminary study on the MIS-emitter transistor was carried out with different emitter areas. In general the characteristics are the same as for the equivalent tunnel oxide devices. However it was also found that if the n-type epilayer is very thin the transistor characteristics exhibits an N-type negative resistance. The negative resistance region of the two-terminal MISS has been shown to be stable and the stability has been analysed in terms of equivalent circuit elements. The reason for the stability is that the device also has an negative capacitance. This has been proved experimentally and it is a new property of the MISS structure which never been reported before. The negative capacitance has been measured as a function of electrode area, SRO type and light illumination. An important circuit application for the negative capacitance has also been suggested and demonstrated

Power amplifying apparatus for optical disk apparatus

Abstract: A power amplifying apparatus for amplifying an input signal to drive a load, includes an amplifier for amplifying the input signal so as to generate an output signal for driving the load and a current/voltage converter for current/voltage converting the output signal generated by the amplifier and feeding back the converted voltage to the amplifier. The converted voltage is used to control the amplitude of the output signal which flows into the load. The power amplifying apparatus further includes a circuit for determining a current-to-voltage conversion ratio of the current/voltage converter. The amplitude of the converted voltage converted by the current/voltage converter may be varied in accordance with the current-to-voltage converting ratio determined by the determining circuit.

Low-harmonic GTO converter for power factor compensation

Abstract: A low-harmonic gate-turn-off (GTO) AC-to-DC converter is proposed. The converter can be used as a fundamental input-power-factor compensator in any energized load system. The effect of pulsewidth-modulated (PWM) current pulse number on the harmonic contents and converter output voltage control range is investigated. Lower-order input-current harmonics are eliminated over a wide range, using a specially designed PWM current pattern. >

Controlled DC-DC converter

Abstract: In known converters, a supply voltage, which is supplied from a battery or is produced by immediate rectification of the mains AC, and which is applied as the input voltage to a series circuit consisting of a primary winding of its converter transformer and a switching transistor, may lie within a wide range of variation. In this case, as a result of the regulation of the output voltage to a constant level, different pulse widths occur. In this case, the constancy of the associated secondary voltages and the converter efficiency vary severely, the object of the invention being to improve this. The converter input has added to it the sum of the supply voltage and an additional voltage, the latter being generated by the converter itself in the same manner as the main output voltage. This additional voltage is formed in a rectifier circuit which is supplied from a dedicated secondary winding or even from a primary winding of the converter. This results in a significantly smaller range of variation of the converter input voltage, as a result of which short pulse widths are avoided and both the efficiency of the converter and the constancy of the secondary voltages are increased. DC-DC converters, which are operated with highly differing or varying supply voltages.

Variable impedance circuit for high voltage application

Abstract: PURPOSE: To apply the circuit even to a high voltage application by connecting plural field effect transistor(TR) in series and operating TRs other than one TR with a bias. CONSTITUTION: N-channel gate field effect TRs 1 1 to 1 n-1 connected in series are operated by self-bias through voltages balance resistors 7 1 to 7 n and 8 1 and 8 n to operate the TR 1 n of the lowest stage with a constant current at a low voltage and the circuit copes with a high positive voltage inputted between terminals 13. Similarly, P-channel gate field effect TRs 2 2 to 2 m connected in series are operated by self-bias through voltage balance resistors 7 1 to 7 m and 8 1 to 8 m to operate the TR 2 1 of the uppermost stage with a constant current at a low voltage and the circuit copes with a high negative voltage inputted between terminals 14. Thus, the high voltage variable impedance circuit for both positive and negative potentials is formed inexpensively with small size. COPYRIGHT: (C)1989,JPO&Japio

Control apparatus for cascaded converter circuit

Abstract: A converter circuit includes three-phase unit converters connected in cascade in two stages for supplying electric power to a load. In a region in which the converter output voltage ratio is small, the firing phases of both converters are so set that a phase difference of 120° makes appearance therebetween, while in a region in which the converter output voltage ratio is large, the firing phases are so set as to have a phase difference of 60° therebetween, whereby an angular difference of 90° to 30° is caused to occur constantly between the phases of voltage ripple components of the unit converters. Power factor of a power supply source is improved while ripple in the output voltage of the converter circuit is reduced.