Parasitic capacitance

About: Parasitic capacitance is a research topic. Over the lifetime, 10029 publications have been published within this topic receiving 110331 citations.

Probe for measuring surface roughness by sensing fringe field capacitance effects

Abstract: A capacitance sensing probe is disclosed for taking measurements of features on a workpiece surface. The probe has two electrodes (E 1 , E 2 ) spaced apart in the direction of movement of the probe with the electrodes being disposed in an attitude normal to the surface. Only the edge of the electrodes are exposed to the surface and an electric circuit (EC) is provided for determining the effect of the surface on the fringe field capacitance between the electrodes. Guard electrodes are used to reduce the stray capacitance being measured. Various embodiments are shown with different numbers and arrangements of electrodes.

Forward-flyback converter with active-clamp circuit

Abstract: The present invention discloses a forward-flyback converter with active-clamp circuit. The secondary side of the proposed converter is of center-tapped configuration to integrate a forward circuit and a flyback circuit. The flyback sub-circuit operating continuous conduction mode is employed to directly transfer the reset energy of the transformer to the output load. The forward sub-circuit operating discontinuous conduction mode can correspondingly adjust the duty ratio with the output load change. Under the heavy load condition, the mechanism of active-clamp flyback sub-circuit can provide sufficient resonant current to facilitate the parasitic capacitance of the switches to be discharged to zero. Under the light load condition, the time interval in which the resonant current turns from negative into positive is prolonged to ensure zero voltage switching function. Meanwhile, the flyback sub-circuit wherein the rectifier diode is reverse biased is inactive in order to further reduce the power losses.

Oscillator circuit having trimmable capacitor array receiving a reference current

Abstract: An oscillator circuit includes a current generator which supplies current to input terminals of capacitors in a trimmable capacitor array. The input terminals of the capacitors are held at a relatively constant voltage, and thus all of the current from the current generator passes through the desired capacitors of the capacitor array, thus minimizing the effect of parasitic capacitance.

A switched-capacitor charge-balancing analog-to-digital converter and its application to capacitance measurement

Abstract: An analog-to-digital converter is developed based on the charge-balancing principle. It consists of a switched-capacitor integrator, comparator, and digital logic circuit. Driven by the two phase clock, the integrator accumulates consecutively the incremental signal charge while extracting the quantized reference charge from the accumulated signal charge each time its output becomes positive, to keep their charge balance. The ratio between the accumulated and extracted frequencies for a given period of time then provides the digital representation of an input analog signal. A conversion accuracy higher than 14 bits can be expected from its integrated realization because the offset voltage and the finite open-loop gain of an op-amp and the parasitic capacitance have no effect upon the conversion process. It also features a small device-count integrate onto a very small chip area. Some applications are also presented to demonstrate its validity.

A model of artefacts produced by stray capacitance during whole body or segmental bioimpedance spectroscopy

Abstract: We have developed a novel model for the simulation of artefacts which are produced by stray capacitance during bioimpedance spectroscopy. We focused on whole body and segmental measurements in the frequency range 5-1000 kHz. The current source was assumed to by asymmetric with respect to ground as is the case for many commercial devices. We considered the following stray pathways: 1, cable capacitance; 2, capacitance between neighbouring electrode leads; 3. capacitance between different body segments and earth; 4, capacitance between signal ground of the device and earth. According to our results the pathways 3 and 4 cause a significant spurious dispersion in the measured impedance spectra at frequencies > 500 kHz. During segmental measurements the spectra have been found to be sensitive to an interchange of the electrode cable pairs. The sensitivity was also observed in vivo and is due to asymmetry of the potential distribution along the segment with respect to earth. In contrast to previously published approaches, our model renders possible the simulation of this effect. However, it is unable to fully explain the deviations of in vivo measured impedance spectra from a single Cole circle. We postulate that the remaining deviations are due to a physiologically caused superposition of two dispersions from two different tissues.