Аналіз впливу індуктивності навантаження на спричинені «мертвим часом» нелінійні спотворення підсилювача класу D

Goal. Analysis of the effect of load inductance at the output of the class D amplifier for different values of the duration of «dead time» and assessment of the adequacy of existing mathematical models for calculating the THD at the output of the amplifier depending on the duration of «dead time». Methodology. The study of the effect of «dead time» on the THD was performed using a computer model of the half-bridge converter board EPC9035 from Efficient Power Conversion. This board contains GaN transistors EPC2022 eGaN®, the corresponding control driver and other necessary elements for operation. The use of GaN transistors has made it possible to investigate the operation in a wide range of frequent switching, both to control the motor and to amplify the audio signal. Results. It is established that the value of load inductance affects the level of nonlinear distortions caused by «dead time». At inductance values that provide a constant sign of the output current, a difference arises between the duration of the input and output pulses, which increases the THD. At inductance values, when the choke current changes sign during a pulse, there is no error between the duration of the input and output pulses. Changing the inductance changes the relationship between the error signal and the non-error signal. THD changes accordingly. At high conversion frequencies, the voltage spikes caused by the choke current through the built-in diodes during the dead time are partially compensated by overcharging the output capacitance of the transistors, which also reduces harmonic distortion. Originality. For the first time, the value of the THD at the outlets in the fallowness of the different indices of the inductance of the choke and the theoretical calculation of the value in the results of the computer model was obtained. Practical significance. The dependence of the THD values on the inductance of the choke for converters with a switching frequency range from 1 kHz to 400 kHz, which allows them to be used both to control the motor and to amplify the audio signal.В роботі досліджено вплив індуктивності навантаження підсилювача класу D на значення коефіцієнту гармонічних спотворень (КГС) на виході для різних значень тривалості «мертвого часу» або вимкненого стану вихідних транзисторів. Оцінена адекватність існуючих математичних моделей для розрахунку КГС на виході підсилювача в залежності від тривалості «мертвого часу». Наведено результати комп’ютерного моделювання підсилювача класу D та досліджено значення КГС на виході в залежності від різних номіналів індуктивності вихідного дроселя. Виконано порівняння теоретично обчислених значень з результатами комп’ютерного моделювання. В результаті дослідження встановлено, що КГС, спричинений наявністю «мертвого часу» залежить від індуктивності навантаження. Отриманий у результаті моделювання КГС співпадає з розрахованим за формулою тільки для певних значень індуктивності навантаження. В моделі використано GaN транзистори, що дозволило дослідити роботу підсилювача у широкому діапазоні частот перемикання

Abnormalities of erythrocyte glycoconjugates are identical in two families with congenital dyserythropoietic anemia type II with different chromosomal localizations of the disease gene

We analyzed erythrocyte glycoconjugates in two families with congenital dyserythropoietic anemia type II (CDA-II): family 2 with the typical localization of the disease gene to chromosome 20q11.2 and family 1 in which this localization was excluded. Despite the different genetics, the erythrocyte glycoconjugate abnormalities in the two families were identical suggesting a complex inheritance of CDA-II. We also found that erythrocyte anion exchanger 1 protein is decreased in CDA-II homozygotes and obligate carriers alike

Frequency of congenital dyserythropoietic anemias in Europe.

Congenital dyserythropoietic anemias (CDAs) are rare hereditary disorders characterized by ineffective erythropoiesis and striking abnormalities of erythroblast morphology. The mutated genes are known for the most frequent types, CDA I and II, but data about their frequency do not exist. The objective of this retrospective study was to estimate the frequency of CDA I and II, based on all cases reported in the last 42 yr in publications and identified registries or surveys. Reports were collected of 124 and 377 confirmed cases of CDA I and CDA II cases, respectively. The cumulated incidence of both types combined varied widely between European regions, with minimal values of 0.08 cases ⁄ million in Scandinavia and 2.60 cases ⁄ million in Italy. CDA II is more frequent than CDA I, with an overall ratio of approximately 3.2, but the ratio also varied between different regions. The most likely explanations for the differences are both differences in the availability of advanced diagnostic procedures and different levels of the awareness for the diagnosis of the CDAs. The estimations reported here are most probably below the true incidence rates, because of failure to make the correct diagnosis and to underreporting. Limited data do not suggest differing levels of risk in identified ethnic groups

Desiccation decreases abscisic acid content in hybrid larch (Larix x leptoeuropaea) somatic embryos

International audiencePrevious studies indicated that the high endogenous abscisic acid (ABA) content of hybrid larch (Larix X leptoeuropaea) somatic embryos was correlated with low germination frequency. However, when dried, the germination rate of the somatic embryos improved. Therefore, our present objective was to study the effect of desiccation on the levels of ABA and its glucose ester metabolite. Cotyledonary somatic embryos were subjected to drying treatments at 40C under relative humidities of 98 and 59% for one week and the levels of both ABA and abscisic acid glucose ester (ABAGE) were followed by enzyme‐linked immunoassay (ELISA). During desiccation at 98% relative humidity (RH) both ABA and ABAGE levels decreased in an irregular fashion. Regardless of RH, transient increases in ABA were observed that were paralleled by marked decreases in ABAGE. It is concluded that the desiccation of somatic embryos which leads to a decrease in ABA content, could explain the enhanced germination capacity of such embryos