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.

Solid-state voltage reference providing a regulated voltage having a high magnitude

Abstract: A two transistor voltage reference circuit controls the ratio of the current densities of two transistors by a negative feedback loop. A voltage corresponding to the difference in the base-to-emitter voltages of the two transistors is developed which has a positive temperature coefficient (TC) and which is connected in series with the base-to-emitter voltage of one of the two transistors having a negative TC. The circuit parameters are selected so that the resultant combined voltage has a predetermined, composite TC. A zener diode is included in the negative feedback loop and arranged to have a TC which cancels the predetermined composite TC to develop a reference voltage having a high magnitude that has minimal variation with temperature change.

Voltage doubler application in isolated resonant converters

Abstract: Two basic conditions of voltage-doubler adopted in isolated DC/DC converter are analyzed. According to the basic conditions, that voltage-doubler can be both adopted in LC series resonant converter and LLC multi-resonant converter. Operation characteristic of voltage-doubler adopted in isolated DC/DC converter is described in detail based on the analysis of voltage-doubler rectifying LLC multi-resonant converter. Advantages of voltage-doubler rectifying LLC multi-resonant converter are described in detail as follows, structure of transformer, in which one winding is involved on its secondary side, is simple, voltage stress of output capacitor is half of output and extra voltage balancing circuit is excluded. Two rectifier diodes are included on output end, voltage and current stress of diodes respectively equal output voltage and current. Therefore, the topology is a preferable candidate for such application as low-medium power level DC/DC converter with high output voltage. In addition, principle of automatic voltage balancing for output capacitor is presented, moreover design of key parameter is specified as well. Presented characteristics of the very topology are verified by a prototype, whose output is 500 V and efficiency of full load reaches 92.3%.

Decrease in the double layer capacitance by faradaic current

Abstract: This study describes the reverse of the well-known double layer effects on charge transfer kinetics in the relationship between a cause and an effect. The reversible redox reaction of a ferrocenyl derivative decreased the capacitive values of the double layer impedance up to negative values, corresponding to an inductive component. This observation was disclosed by the subtraction of the real admittance from the imaginary admittance, which can extract the net double layer capacitance from the Warburg impedance. The inductance-like behavior is caused due to two reasons: (i) the double layer capacitance in the polarized potential domain is determined by the low concentrations of the field-oriented solvent dipoles that are considered as the conventionally employed redox concentrations and (ii) the double layer capacitance is caused by the orientation of the dipoles in the same direction as that of the electric field, whereas the redox reaction generates charge in the direction opposite to the field. The faradaic effect was demonstrated via the ac-impedance data obtained for the ferrocenyl compound in a KCl solution in the unpolarized potential domain between 1 Hz and 3 kHz frequency. The negative admittance was proportional to the frequency. The theory of negative capacitance was presented by combining the mirror-image surface charge with the Nernst equation.

A unified impedance model of voltage-source converters with phase-locked loop effect

Abstract: This paper proposes a unified impedance model for analyzing the effect of Phase-Locked Loop (PLL) on the stability of grid-connected voltage-source converters. In the approach, the dq-frame impedance model is transformed into the stationary αβ-frame by means of complex transfer functions and complex space vectors, which not only predicts the stability impact of the PLL, but reveals also its frequency coupling effect in the phase domain. Thus, the impedance models previously developed in the different domains can be unified. Moreover, the impedance shaping effects of PLL are structurally characterized for the current control in the rotating dq-frame and the stationary αβ-frame. Case studies based on the unified impedance model are presented, which are then verified in the time-domain simulations and experiments. The results closely correlate with the impedance-based analysis.

Family of zero-voltage transition pulse width modulation converters with low auxiliary switch voltage stress

Abstract: A new family of zero-voltage transition (ZVT) pulse width modulation (PWM) converters is introduced. In this converter family there is no additional voltage stress on the main switch in comparison to the hard switching counterpart. Also, the voltage and current rating of the auxiliary switch is low. The proposed zero-voltage transition PWM buck converter is analysed and design considerations are discussed. A prototype converter is implemented and the experimental results are presented.