scholarly journals Comparison of transient states in step-down power converter (BUCK) in continuous and discontinuous conduction mode

2014 ◽  
Vol 62 (4) ◽  
pp. 773-778
Author(s):  
W. Janke ◽  
M. Walczak
Keyword(s):  
Separation Of Variables ◽  
Power Converter ◽  
Order Type ◽  
First Order ◽  
Transient States ◽  
Discontinuous Conduction Mode ◽  
Fast Transients ◽  
Step Down ◽  
Averaged Models ◽  
Conduction Mode

Abstract The object of this paper is a step-down (BUCK) power converter working in the continuous conduction mode (CCM) or discontinuous conduction mode (DCM). Two types of transient states in a converter have been analyzed and observed experimentally: slow transients, described by averaged models of a converter and fast transients, in the course of a single switching period. The averaged models of converter working in CCM, presented in various sources are similar, with some differences concerning only the description of parasitic effects. The averaged models for DCM depend on the adopted modeling method. Models obtained by the switch averaging approach are second-order models (containing two reactive elements in equivalent circuit representation). Models obtained by the separation of variables approach are first-order models. The experimental results given in this paper show the first-order type of transients. Another group of experiments concern fast transients in the course of a single switching period. The oscillations of inductor voltage in the part of a switching period are observed for DCM.

scholarly journals Small-signal input characteristics of step-down and step-up converters in various conduction modes

2016 ◽  
Vol 64 (2) ◽  
pp. 265-270 ◽  
Author(s):  
W. Janke ◽  
M. Walczak
Keyword(s):  
Low Frequency ◽  
Laboratory Model ◽  
Small Signal ◽  
Input Admittance ◽  
Discontinuous Conduction Mode ◽  
Dc Power ◽  
Signal Input ◽  
Analytical Formulas ◽  
Averaged Models ◽  
Conduction Mode

Abstract Small-signal input characteristics of BUCK and BOOST DC-DC power converters in continuous conduction and discontinuous conduction mode have been presented. Special attention is paid to characteristics in discontinuous conduction mode. The input characteristics are derived from the general form of averaged models of converters. The frequency dependence of input admittance and other input characteristics has been observed in a relatively low-frequency range. The analytical formulas derived in the paper are illustrated by numerical calculations and verified by experiments with a laboratory model of BOOST converter. A satisfying level of conformity of calculations and measurements has been obtained.

PLATELET AGGREGATION DOES NOT CONFORM TO SIMPLE PARTICLE COLLISION THEORY

1987 ◽  
Author(s):  
Moideen P Jamaluddin
Keyword(s):  
Platelet Aggregation ◽  
Rate Equation ◽  
Rate Constants ◽  
Kinetic Scheme ◽  
Order Type ◽  
Second Order ◽  
Particle Collision ◽  
Collision Theory ◽  
Rate Law ◽  
First Order

Platelet aggregation kinetics, according to the particle collision theory, generally assumed to apply, ought to conform to a second order type of rate law. But published data on the time-course of ADP-induced single platelet recruitment into aggregates were found not to do so and to lead to abnormal second order rate constants much larger than even their theoretical upper bounds. The data were, instead, found to fit a first order type of rate law rather well with rate constants in the range of 0.04 - 0.27 s-1. These results were confirmed in our laboratory employing gelfiltered calf platelets. Thus a mechanism much more complex than hithertofore recognized, is operative. The following kinetic scheme was formulated on the basis of information gleaned from the literature.where P is the nonaggregable, discoid platelet, A the agonist, P* an aggregable platelet form with membranous protrusions, and P** another aggregable platelet form with pseudopods. Taking into account the relative magnitudes of the k*s and assuming aggregation to be driven by hydrophobic interaction between complementary surfaces of P* and P** species, a rate equation was derived for aggregation. The kinetic scheme and the rate equation could account for the apparent first order rate law and other empirical observations in the literature.

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