Negative impedance converter

About: Negative impedance converter is a research topic. Over the lifetime, 5801 publications have been published within this topic receiving 87636 citations.

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.

Voltage Gain Enhancement for a Step-Up Converter Constructed by KY and Buck-Boost Converters

Abstract: In this paper, a novel voltage-boosting converter is presented, which combines one charge pump and one coupled inductor with the turns ratio. The corresponding voltage gain is greater than that of the existing step-up converter combining KY and buck-boost converters. Since the proposed converter possesses an output inductor, the output current is nonpulsating. After some mathematical deductions, an experimental setup with 12-V input voltage, 72-V output voltage, and 60-W output power is used to verify the effectiveness of the proposed converter.

Analysis of voltage and current stresses of a generalised step-up DC-DC converter

Abstract: A non-isolated DC-DC converter with high-voltage gain and low-voltage stress on switches is proposed in this study. For absorption of energy n stages of diode-capacitor-inductor (D-C-L) units are used at the input that results in higher voltage gains. Actually, the proposed converter generalises the voltage lift circuit and combines it with a voltage multiplier cell. Therefore comparing to structures with one stage of D-C-L unit, it will be feasible to achieve supposed voltage gain at lower duty cycles. Lower values of duty cycle will result in increasing of converter controllability and increasing of operation region. The generalised analysis of the voltage and current stresses of the semiconductors and power components is carried out. The circuit performance will be compared with other solutions that were previously proposed for voltage step-up in the terms of voltage gain, switch and output diode voltage stress and number of components. The carried mathematical analysis and circuit performance are validated through both simulation and experimental results that match each other reasonably well.

Active and passive vibration isolation and damping via shunted transducers

Abstract: Many different active control techniques can be used to control the vibrations of a mechanical structure: they however require at least a sensitive signal amplifier (for the sensor), a power amplifier (for the actuator) and an analog or digital filter (for the controller). The use of all these electronic devices may be impractical in many applications and has motivated the use of the so-called shunt circuits, in which an electrical circuit is directly connected to a transducer embedded in the structure. The transducer acts as an energy converter: it transforms mechanical (vibrational) energy into electrical energy, which is in turn dissipated in the shunt circuit. No separate sensor is required, and only one, generally simple electronic circuit is used. The stability of the shunted structure is guaranteed if the electric circuit is passive, i.e., if it is made of passive components such as resistors and inductors.This thesis compares the performances of the electric shunt circuits with those of classical active control systems. It successively considers the use of piezoelectric transducers and that of electromagnetic (moving-coil) transducers.In a first part, the different damping techniques are applied on a benchmark truss structure equipped with a piezoelectric stack transducer. A unified formulation is found and experimentally verified for an active control law, the Integral Force Feedback (IFF), and for various passive shunt circuits (resistive and resistive-inductive). The use of an active shunt, namely the negative capacitance, is also investigated in detail. Two different implementations are discussed: they are shown to have very different stability limits and performances.In a second part, vibration isolation with electromagnetic (moving-coil) transducers is introduced. The effects of an inductive-resistive shunt circuit are studied in detail; an equivalent mechanical representation is found. The performances are compared with that of resonant shunts and with that of active isolation with IFF. Next, the construction of a six-axis isolator based on a Stewart Platform is presented: the key parameters and the main limitations of the system are highlighted.

DC-to-DC converter with fast override feedback control and associated methods

Abstract: A DC-to-DC converter includes a pulse width modulation (PWM) circuit cooperating with at least one power switch for supplying power from a source to a load over a range between a lower limit and an upper limit to thereby control an output voltage for the load. The converter may also include a primary feedback control loop cooperating with the PWM circuit for supplying power to the load between the lower and upper limits based upon the output voltage during normal load transient conditions. The converter may also include at least one override feedback control loop cooperating with the PWM circuit for overriding the primary feedback control loop and supplying power to the load at one of the lower and upper limits based upon the output voltage during a corresponding relatively fast load transient condition. Accordingly, relatively fast load transients can be followed by the converter.