Voltage-controlled filter

About: Voltage-controlled filter is a research topic. Over the lifetime, 5514 publications have been published within this topic receiving 70872 citations. The topic is also known as: VCF.

Method and apparatus for high-order bandpass filter with linearly adjustable bandwidth

Abstract: A method and apparatus for linearly adjusting the bandwidth of a high-order bandpass filter. A high-order bandpass filter is formed by cascading together two or more low-order bandpass filters. The bandwidths and center frequencies of each individual low-order bandpass filter is adjusted. The center frequency of some low-order bandpass filters are adjusted so as to achieve linear adjustment of the bandwidth of the high-order bandpass filter.

Active control apparatus using adaptive digital filter

Abstract: An active control apparatus using an adaptive IIR digital filter includes a coefficient control portion for updating the filter coefficient of adaptive IIR digital filter so as to minimize an output error signal level, and a coefficient control portion for updating the filter coefficient of a recursive portion so as to minimize the output level of recursive portion. The filter coefficient of recursive filter is updated by these two coefficient control portions and in parallel or in a time-dividing manner.

Input Filter Damping Design for Control Loop Stability of DC-DC Converters

Abstract: An input filter is often employed for EMI noise reduction between a dc-dc converter and its power source. However, its presence, in turn, often results in degradation of dynamic performance and instability of the system even if the filter attenuation is brilliantly designed. The detrimental interaction between an input filter and a switched mode converter is a function of the input filter parameters as well as the supply voltage. This paper addresses the instability problem in dc-dc converters under strong influence of input filter interaction and suggests a systematic design procedure to damp the input filter using R-C parallel damping in order to stabilize the whole filter- converter system without over sizing or under sizing. It is then possible to define a dc-dc converter's stable operating region based on the input filter's damping circuit parameters. A buck converter under voltage-mode control is used as an illustrative example. Computer simulations and experimental results validate theoretical results of this paper.

A Subhertz Nanopower Low-Pass Filter

Abstract: This brief presents a first-order low-pass filter topology capable of providing cutoff frequencies down to 2 mHz with power consumption of 5 nW. The circuit is intended for signal conditioning applications, particularly for use with very low frequency physiological signals in low-power portable medical equipment. To achieve a low-frequency cutoff, the filter is based around the use of a clocked transconductor, which provides low transconductance while using a relatively high bias current level. The circuit is implemented in a 0.35-μm technology with a 1-V supply and has 32- μVRMS measured noise and a 64-dB dynamic range. In terms of power consumption and cutoff frequency the reported filter outperforms previous filters from the literature.

Design of harmonic current detector and stability analysis of a hybrid parallel active filter

Abstract: A promising method to solve harmonic problems in power systems is by using a hybrid parallel active power filter. This filter is composed of both active and passive filters. The active filter will suppress low-order harmonic currents of the power system and the remaining high-order harmonic currents in the system will be reduced by a high-pass passive filter. In this hybrid structure, one has to consider both the detection method for harmonic current to be compensated by the active filter and the stability in the presence of the passive filter. In this paper, the authors present a new design method for a harmonic current detector which will detect, precisely, the low-order harmonic currents (5/sup th/, 7/sup th/) using a band-pass filter built on the rotating frame of the fundamental frequency (50 Hz). In addition, stability analysis of the whole system when the point of detection is located at various positions is investigated. Experimental results shown in the paper indicate the effectiveness and validity of the method proposed.