Showing papers on "Negative impedance converter published in 1994"

Analysis and design of LCL-type series resonant converter

Abstract: A series resonant converter modified by adding an inductor in parallel with the transformer primary (or secondary) is presented. This configuration is referred to as an "LCL-type series resonant converter". A simplified steady-state analysis using complex AC circuit analysis is presented. Based on the analysis, a simple design procedure is given. Detailed experimental results obtained from a MOSFET-based 640 W converter are presented to verify the analysis. A narrow variation in switching frequency is required to regulate the output voltage for a very wide change in load, and the converter has load short-circuit capability. It is shown that by placing the parallel inductor on the secondary side, the parasitics of the high-frequency transformer can be used profitably. >

Fuel cell voltage generator

Abstract: The invention relates to a voltage generator including a fuel cell, a d.c. converter and a storage battery, the input terminals of the d.c. converter being connected to the fuel cell terminals and the output terminals of the d.c. converter being connected on the voltage generator terminals in parallel with those of the battery. A microprocessor regulates the maximum intensity value of the current going through the d.c. converter responsive to the voltage measured at the terminals of the fuel cell in order to maintain the voltage near a preset reference value.

Resonant power factor converter

Abstract: The present invention is directed to a novel converter for interposition between an AC power source and a DC load capable of maintaining a substantially unity power factor independent of the impedance of the load. According to the invention, the converter has rectifying circuit to provide DC power to a DC power output circuit from an AC source, circuit for varying the impedance seen by the AC source in the DC output circuit, and circuit responsive to a shift in AC input current away from an in-phase relation with the voltage of the AC source under loading of the DC power output circuit for controlling said impedance varying circuit in a direction to return the AC current towards in-phase relation with the AC voltage. More particularly, according to the preferred form of the invention, the circuit for varying the impedance seen by the AC source in the DC output circuit includes a resonant circuit interposed between the rectifying circuit and the DC output circuit and connected to deliver DC power thereto. The converter includes a control circuit responsive to the DC voltage of the DC output circuit and the phase between the AC voltage and AC current. The control converter also includes a variable impedance responsive to the resonant circuit current for controlling the phase angle between the resonant circuit current and voltage across the resonant circuit.

Negative impedance peak power tracker

Abstract: A peak power tracker apparatus is used for controlling the negative impedance of converter for transferring maximum power from a solar array source to a battery and load typically used in space vehicles, by capacitive differentiation sensing the solar array source voltage for sensing the peak power point at which the source voltage first begins to become unstable and collapses, and then providing a step down control signal which controls a current mode pulse width modulator to control the converter to vary the negative impedance into the solar array then reserving back to a stable point at which the tracker then provide a linear ramp signal to the modulator to control the converter to drive the source voltage again to the peak power point, so as to alternate the feedback loop and source voltage between a stable point and the peak power point so as to transfer maximum power while preventing the source voltage to pass through an unstable point for discontinuous but stable operation at peak power transfer which is independent of array performance and is adaptable to a wide range of power sources.

Steady-state analysis including parasitic components and switching losses of buck and boost DC-DC PWM converters under any operating condition

Abstract: A detailed analysis of DC-DC buck and boost converters operated both in continuous and discontinuous current modes is reported. Expressions for the voltage transfer functions and efficiencies of these two basic topologies have been derived in a closed form. These equations describe the converter behaviour for both constant output voltage and constant input voltage operation. Voltage transfer functions are derived so that the load regulation characteristics of the converters are closely described, including those for continuous current mode operation. Because of this, they can be effectively used to design a converter circuit responding to any given design specification. Both the equations for the efficiencies and voltage transfer functions are general and the values of the parasitic parameters to be introduced can be found on the component data sheets or derived from simple measurements. Because of this, results of the analysis presented can be effectively used in the optimization of the converter circuit...

Overload protection of switch mode converters

Abstract: A switch mode power converter having an overload protection system is disclosed. The system includes an input stage having an input voltage source. A switching circuit for coupling said input source to an output stage is provided. The output stage further includes a first filter circuit providing an output current to a load circuit. A second filter circuit is coupled to the output stage providing a voltage proportional to the output current and to internal temperature of the switch mode converter. An error amplifier responsive to the voltage derived by a second filter and a reference voltage, generates an error signal proportional to the difference of the voltage applied to the error amplifier. The error signal adjusts the operating parameters of the switching circuit.

An integrated device having MOS transistors which enable positive and negative voltage swings

Abstract: A semiconductor circuit integrated with CMOS circuits for receiving a TTL input voltage and generating a large negative and positive voltage swing with respect to p-type or n-type substrate is disclosed. This invention is based on elimination of the electro-static discharge (ESD) protection circuit which is a requirement for any integrated circuit. Eliminating the ESD protection circuit also eliminates the clamping feature of the ESD protection circuit and therefore the circuit can be driven to negative voltages for PMOS circuits and to positive voltages for NMOS circuits. This provides the possibility of connecting the drain of a a P-channel type metal oxide silicon field effect (PMOS) transistor, which is fabricated on a p-type substrate within an n-well, to a voltage below the the substrate voltage. Also, in a n-channel type metal oxide silicon field effect (NMOS) transistor which is fabricated on a n-type substrate within a P-well, the drain can be connected to voltages higher than the substrate voltage. Utilizing this feature of a MOS transistor provides a way to design an integrated circuit which can handle negative voltage swings as well as positive voltage swings.

An NIC-based negative resistance circuit for microwave active filters

Abstract: This article presents a method for synthesizing a negative resistance in MMIC technology. The circuit employed is a classical negative impedance converter (NIC) that has been terminated in an RLC one-port specially designed to compensate for the parasitics of the active and passive elements. The procedure, which effectively translates a nonideal NIC design task into a well-defined one-port synthesis problem, is demonstrated in computer simulation for a four-transistor MMIC network which achieves a purely real input resistance of −100 Ω over 1.5–2.5 GHz. An important application for NIC-based circuits of this type is in the design of microwave active filters. © 1994 John Wiley & Sons, Inc.

Method for limiting the frequency of a voltage-controlled oscillator in a control circuit of a resonant converter switched-mode power supply, and control circuit for a resonant converter switched-mode power supply

Abstract: A method for limiting the frequency of a voltage-controlled oscillator in a control circuit of a resonant converter switched-mode power supply includes adjusting a delay time of a delay element disposed in a feedback branch of the voltage-controlled oscillator with a signal indicating a transition from negative to positive values of a current through an oscillating circuit of the switched-mode power supply. A resonant converter switched-mode power supply has an output voltage and an oscillating circuit with a current. A control circuit for the resonant converter switched-mode power supply includes a control amplifier being acted upon by the output voltage and by a reference voltage. A voltage-controlled oscillator is connected to and triggered by the control amplifier. A comparator detects a transition from positive to negative values of the current in the oscillating circuit. A flip-flop has a setting input being connected to and triggered by the voltage-controlled oscillator and has a reset input being connected to and triggered by the comparator. A delay element has a variable delay time and is triggered by a signal indicating a transition from negative to positive values of the current in the oscillating circuit.

Alternating current generator for controlling a plasma display screen

Abstract: In a plasma display screen there is a circuit which alternately applies a positive and negative voltage to the general capacitance of the screen or panel for a reset process. In the current path there is an inductance to ensure the recovery of the energy to the total capacity. The aim is to improve the drive and the erase process of a pixel in such a circuit. The capacity (Cp) is cyclically connected via a third switch (T3) to such a third operating voltage that the voltage (UCp) at the capacitance (Cp) has a period of zero voltage between those of positive and negative voltage. Especially for a control circuit for a plasma display screen for a television receiver.

High precision DC-DC converter

Abstract: A high precision DC-DC converter circuit having improved efficiency is disclosed. The DC-DC converter circuit includes a low accuracy switching regulator circuit for driving a switching field effect transistor (FET) on and off. A high accuracy output voltage regulator circuit is inserted into the feedback loop between the output of the DC-DC converter circuit and the sensing input of the switching regulator circuit such that the accuracy of the output voltage regulator circuit primarily determines the precision of the DC-DC converter. The DC-DC converter also includes a quick shut-off circuit coupled to the gate and source of the FET for driving the gate of the FET negative when the FET is switched off such that switching losses are minimized. A second embodiment of the high precision DC-DC converter is used to convert from 5.0 to 3.3 volts. The second embodiment includes a transformer, one winding of which is used as an output inductor. The second winding is used as part of a multiplying bootstrap circuit that approximately triples the 5.0 volt input voltage to drive the gate of an n-channel switching FET. The second embodiment also includes a circuit for extending the duty cycle of the switching regulator in response to a load transient on the output.

DC/DC converter for a variable voltage load

Abstract: The invention relates to a circuit for converting input source energy into output load energy, for example a flyback converter for charging a storage capacitor for defibrilation from a low-voltage battery in an implantable defibrilator. The invention allows the input current to pass through the flyback inductor for a fixed duration and it allows the output current to pass for a duration which is directly proportional to the average voltage of the battery and inversely proportional to the voltage of the capacitor which is charged. When the invention is used in proximity to an electromagnetic communications system, a control circuit, in order to avoid interference, enables and inhibits the converter with a maximum frequency which is substantially below the operating frequency of the system. Moreover, the control circuit drives the converter in such a way that the cycles of energy transfer from the source to the storage capacitor take place at a minimum fundamental frequency which is substantially above the frequency of the system.

Voltage generator circuit generating stable negative potential

Abstract: The voltage generator circuit according to the invention has a first negative potential generator circuit to generate a first clock signal going negative and oscillating at negative voltage in response to a first clock signal oscillating at positive voltage, a second negative potential generator circuit to generate, in response to a second clock signal oscillating at positive voltage, a second clock signal going negative and oscillating at negative voltage and having an amplitude greater than the amplitude voltage of the first clock signal going negative, and an output circuit to deliver the lowest voltage of the first clock signal in response to the second clock signal going negative.

Closed-loop characteristics of voltage-mode-controlled pwm boost dc-dc converter with an integral-lead controller

Abstract: A complete analysis of a voltage-mode-controlled pulse-width-modulated (PWM) boost DC-DC power converter is presented using a previously derived small-signal model for continuous conduction mode (CCM). All parasitic components such as the equivalent series resistance (ESR) of the filter capacitor, the ESR of the inductor, the transistor on-resistance, and the diode forward resistance and offset voltage are included in the model. A design procedure for an integral-lead controller including the loading effect of the voltage divider in the feedback loop is given. The Bode plots of the closed-loop control-to-output transfer function, input-to-output transfer function, input impedance, and output impedance are determined and illustrated for three values of the duty cycle. Step response plots of the PWM boost converter in the open-loop and closed-loop cases are shown for changes in line voltage and duty cycle.

A bidirectional load current sense circuit for a H-bridge

Abstract: The present invention relates to a current sense device for a load arranged in a diagonal of a H-bridge comprising MOS transistors (M1, M2, M3, M4) and operating in class AB, characterized in that it includes sensor, independent from the H-bridge, for measuring the current flowing in the load. A current-voltage converter converts the current measured by said sensor into a voltage proportional to said current. The voltage is applied to a sense amplifier that determines the transconductance gain of a control amplifier of the transistors of the H-bridge.

A/D converter system and method with temperature compensation

Abstract: An A/D circuit to convert an analog signal to a digital signal. The circuit includes a low noise analog-to-digital conversion chip and a precision voltage reference source. The voltage reference source includes a diode with two terminals and a passive attenuation circuit. The attenuation circuit and the diode are coupled in parallel between the two terminals to provide a voltage reference signal for use by the analog to digital conversion chip. The analog to digital chip uses the voltage reference signal to set the full scale input range for the signal conversion, and the voltage reference signal is attenuated to correspond to the full scale range of the analog signal. The A/D converter circuit has a passive temperature compensation feature to substantially eliminate or reduce the effects of thermal drift and of operating at different temperatures. Also, the A/D converter circuit can be coupled to a plurality of transducer inputs, such that the A/D converter circuit can measure voltage, current and resistance input signals.

Apparatus for controlling power converter based on output current

Abstract: A control apparatus for controlling a power converter includes a plurality of switching devices and enabling converted AC output to be obtained to supply arbitrary AC outputs to a load. A voltage command value generating device for generating a voltage command value is provided to command voltage to be transmitted from the power converter. A voltage control device is provided for controlling a plurality of switching devices of the power converter in accordance with a command voltage level. An electric current detection device is included for detecting an output electric current to be supplied from the power converter to the load. An electric current limiting device is provided for restricting the command voltage level to be supplied to the voltage control device in accordance with a value detected by the electric current detection device.

Single-phase composite PWM voltage source converter

Abstract: This paper proposes a novel circuit of a single-phase voltage source converter. A pulsewidth modulation (PWM) strategy is utilized to obtain a sinusoidal input current. The proposed circuit has an auxiliary arm for the bridge circuit and can be operated by a composite PWM strategy which contributes to reduce the ripple in the current. Moreover, the novel circuit has an LC series resonance circuit in the DC side. The DC capacitance necessarily installed in the converter can be greatly reduced by applying the resonance circuit and the constant DC voltage is achieved. The experimental and the theoretical results in the rectifier operation of the converter are shown. The steady state waveforms in the inverter operation with the photovoltaic in the DC side are given. The experiments show that the proposed converter can be used for a single-phase utility interactive photovoltaic system. >

Abnormality detector for a/d converter

Abstract: PURPOSE:To surely detect the abnormal state of an A/D converter by applying equality discrimination between the normal output value of the A/D converter stored in advance corresponding to a voltage or the current of a test signal and an actual output. CONSTITUTION:In the abnormality discrimination mode, a 1st reference voltage EREF1 from a 1st reference voltage generating circuit 5 is given to an A/D converter 21 by applying selection control to MPX4, 7 by a peripheral IF 25. A CPU 22 reads the conversion value at that time and the value is compared with a predetermimed 1st reference value (normal output of the A/D converter 21 at the input of the voltage EREF1) stored in a memory 23. When they are equal, a 2nd reference voltage EREF2 from a 2nd reference voltage generating circuit 6 is given to the A/D converter 21, the AD-converted value is read and it is compared with a 2nd predetermined reference value similarly. When they are equal, it is regarded that the A/D converter 21 is normal to reset an abnormal flag. If either of two discrimination results is unequal, the abnormality flag is set. Thus, the abnormality detection result of the A/D converter 21 is set as a state of the abnormality flag in this way.

Variable frequency LC oscillator using variable impedance and negative impedance circuits

Abstract: A variable frequency oscillator which can be implemented entirely in a semiconductor chip, which is variable over a broad frequency range and which has relatively low phase noise, includes a variable impedance circuit, a reactive load connected to an output terminal pair of the variable impedance circuit, and a negative impedance circuit having an output terminal pair connected to the output terminal pair of the variable impedance circuit. In one embodiment, the negative impedance circuit has an input terminal pair connected to an input terminal pair of the variable impedance circuit to serve as a positive feedback path for the variable impedance circuit. In another embodiment, the negative impedance circuit includes a pair of level shifters which ensure that the variable impedance circuit is properly biased and works in a forward active region.

Implantable defibrillator/pacer using negative voltage supplies

Abstract: A configuration for generating single capacitor multiphasic shocks is disclosed, using an H-bridge with four switches to connect an energy storage capacitor to a load with selectable polarity. The improvement concerns referring the negative side of the shock generator to a supply voltage which is negative with respect to pacing and sensing ground, and to connect the battery positive terminal to this same ground. This configuration permits operating the low side switches in the H-bridge, the pace/sense circuits, and the control circuitry from negative supplies derived without inversion from the negative battery terminal.

Control apparatus for power converter

Abstract: The input voltage VR is detected by means of a voltage detecting device and the phase .PHI. of the input voltage is detected by means of a phase synchronizing circuit. The detected phase is input to an AC sine wave reference oscillating circuit in order to obtain an AC sine wave reference signal having the same phase as input voltage. The output of an amplitude instruction generating circuit is multiplied by an AC sine wave reference signal by means of a multiplier in order to obtain a converter current instruction IA*. On the other hand, the input current IR detected by means of a current detecting device is differentiated by means of an approximation differentiator and only the resonance frequency component is detected by means of a band-pass filter. The detected resonance frequency component is multiplied by the gain K by means of a proportion device and the output is subtracted from the converter current instruction IA* by means of a subtracter. The current control amplifier and PWM modulating circuit control a converter so as to make the output from the subtracter agree with the converter current IA* detected by a current detecting device.

Opto-coupling device between a modem and a telephone line

Abstract: An opto-coupling device lies between an analog input circuit, such as a telephone line, and a processing apparatus, such as a modem. The device has a high impedance circuit; this is, its impedance is high with respect to the input impedance of the analog input circuit. This high impedance circuit has a voltage/current conversion circuit. The variations of the current flowing through the conversion circuit are directly induced by the variations in the voltage of the analog input signal. The high impedance circuit is in series with a constant current source, and is connected to the analog input circuit. The inputs of the opto-coupling device are in parallel with the voltage/current conversion circuit.

Chopper type DC-DC converter

Abstract: The DC-DC converter is disclosed, which has an output terminal connected to an external load, and produces a desired output voltage at the output terminal. An output capacitor in the converter has a first electrode connected to the output terminal and a second electrode. The charge/discharge regulator controls electrical connection between a DC power supply and the output capacitor to permit the capacitor to be charged or discharged. The DC-DC converter includes a first detecting circuit for detecting a change in the output voltage at the output terminal, and a second detecting circuit for detecting a variable load current flowing into the converter from the load via the output terminal. A voltage control circuit is provided in the converter, and controls a potential of the second electrode of the capacitor in such a manner as to nullify a variation in the output voltage, based on a result of detection of the output voltage by the first detecting circuit and on a result of detection of the load current by the second detecting circuit.

Zero level setting circuit for A/D converter in a magnetic disk drive

Abstract: In a magnetic disk drive in which an analog signal having symmetrical positive and negative odd levels with respect to a zero-level is read out of a magnetic disk by a head, the read analog signal is processed by an AGC circuit and a low pass filter, the processed analog signal is converted into a digital signal by an A/D converter, and the digital signal is demodulated by a demodulator, a zero-level setting circuit for the A/D converter is comprised of: a reference voltage generator for the A/D converter; a zero-level error detector between the read signal and the reference voltage; an accumulator for accumulating the zero-level error from the zero-level error detector; and an equalizer for equalizing the zero-level of the A/D converter to the reference voltage in accordance to an output signal from the zero-level error accumulator. As a result, the conversion accuracy of the A/D converter is improved while employing a small number of bits.

Switchable impedance circuit

Abstract: A switchable impedance circuit and method for maintaining a controlled signal line (e.g. RF transmission line) impedance at a circuit node includes a circuit and method for connecting a switchable impedance in shunt or series, or in a shunt and series combination. The switchable impedance can be selectively switched, e.g. "on" or "off", when the circuit is being powered up or down, or both, so as to maintain the desired, e.g. characteristic, impedance at the node of the signal line to which it is connected, for example by providing the complex conjugate of, or vectorially matching, any complex impedance present at such node, thereby advantageously helping to minimize undesirable transient signal effects, such as circuit ringing or oscillator frequency pulling.

Switching converter with current limitation

Abstract: Switched converter having current limiting, having a current sensor which is arranged in the main circuit and having a comparator with whose aid it is possible to initiate limiting of the current flowing in the main circuit. In order not significantly to exceed the rated output current in the event of overcurrent or a short-circuit, an integrating circuit (which is connected to the control output of the control circuit) is connected to the output of the nominal-voltage (required-voltage) source. The reference voltage which is applied to the required-value input of the comparator thus falls when the output current rises. The switched converter can advantageously be used for supplying devices for electrical telecommunications technology.

HF surgical appts. with load dependent performance control - has feed source controlled by combination of negative and positive feedback of electrode voltage and current

Abstract: The appts. contains surgical electrodes, a generator supplying HF energy to the electrodes, and a controllable source (2) feeding the generator. The source is controlled in dependence of the impedance between the electrodes. The source control depends on a combination of a negative feedback of a voltage at the electrodes, and a positive feedback of a current flowing through the electrodes. Pref. the rate of the positive current feedback is adjustable for taking into account the size of the tissue portion engaged by the surgical step. The negative feedback adjustment may be proportional to voltage level at the electrodes. USE/ADVANTAGE - For coagulation surgery, with low-cost reliable design.

Electric energy measuring circuit and digital wattmeter

Abstract: PURPOSE: To reduce an error generated by excitation energy for exciting a current transformer in a wattmeter for measuring electric energy by using the current transformer for converting a negative current signal to a voltage signal and digitizing, multiplying, and integrating an electric circuit voltage signal and a negative current signal. CONSTITUTION: A rectifier 105 outputs a signal obtained by superposing a voltage signal corresponding to a load current on a voltage signal corresponding to a signal with a frequency which is not correlated to an electric circuit frequency. The signal passes through an amplification circuit 102, a filter 103, and an A/D converter 104 and is converted into a digital signal. Then, the signal is multiplied by a digitized voltage signal by a multiplication circuit 109, is integrated by an accumulation adder/subtractor 109b, is converted into pulses by a pulse conversion circuit 110a and is counted by a processing circuit 110b, and at the same time, is multiplied by an arbitrary coefficient, and is outputted to a display 111.

Method and device of displaying electric capacity of circuit breaker

Abstract: PURPOSE:To provide a display device that can be used in common even when the rated current of a main circuit differs by detecting the first converter output current for activating the overcurrent relay of a circuit breaker by a second converter, and whereby displaying the detection result. CONSTITUTION:A first converter 4A is interposed on a main circuit 2A, and the overcurrent relay 5 of a circuit breaker 1 is activated through the converter 4A. The output current of the converter 4A is detected by the second converter 70 of a current display device 60, and is displayed by a display part 90 through a converter 9. In this structure, the display device of a circuit breaker that can be used in common even when the rated current of the main circuit differs, is thus provided.