一种基于FAN6754A的PWM反激式开关电源的设计

介绍了新款峰值电流型PWM控制芯片FAN6754A的工作特性和原理,分析了反激式开关电源的设计原理以及工作过程.针对次级电路结构,设计了一种新型反激式开关稳压电源.着重介绍了反激式开关电源的变压器设计过程,包括电感值的计算、磁芯的选择、绕组匝数的确定以及气隙等.利用三端稳压器TL431配合FAN6754A实现了对电源电...     

Analysis of Protein and Total Usable Nitrogen in Beer and Wine Using a Microwell Ninhydrin Assay

In this study we present a ninhydrin based microwell assay that can be utilized in place of the traditional Kjeldahl method for the determination of the protein content of beer or wine. In addition, the assay is ideal for the determination of free amino acids in beer (FAN), a term understood and used by brewers, and yeast assimilable nitrogen (YAN) used by enologists. The assay only measures alpha amino acids and ammonia so other nitrogen sources are not detected, resulting in a 30% reduction in total protein of a variety of beers compared to the Kjeldahl method, which measures nitrogen from all sources. The results also showed that only 25% of the total “protein” in beer is actually derived from peptides larger than 3,500 Kd. Analysis of beer or wine with the microwell assay for total usable nitrogen was compared to the standard FAN and YAN methods and conditions were determined for maximal efficiency and precision. Superior results were obtained with low reaction volumes and a stable sodium acetate buffered ninhydrin reagent at pH 5.5. As an alternative, for use with cuvettes, a reduced volume FAN assay using the same pH 5.5 sodium acetate buffered ninhydrin reagent gave comparable results. The assay is economical, rapid, accurate and applicable to large numbers of samples.     

DETERMINATION OF FERMENTABLE SUGARS AND NITROGENOUS COMPOUNDS IN WORT BY NEAR- AND MID-INFRARED SPECTROSCOPY

Near-infrared (NIR) and mid-infrared (MIR) spectroscopy techniques were evaluated for the analysis of brewery worts. Good calibrations were obtained for maltose (SEP_NIR 2.6 g/l, SEP_MIR 2.0 g/l), glucose SEP_NIR 0.6 g/l, SEP_MIR 0.4 g/l) and the sum of fermentable sugars (SEP_NIR 2.8 g/l, SEP_MIR 2.6 g/l) with both methods. Satisfactory calibration was obtained for maltotriose (SEP_NIR 1.4 g/l, SEP_MIR 1.5 g/l), nitrogen (SEP_NIR 122 mg/l, SEP_MIR 92 mg/l) and free alpha-amino nitrogen (SEP_NIR 29 mg/l, SEP_MIR 23 mg/l). MIR spectroscopy gave slightly better results, but sample handling was more difficult than in the NIR region. The NIR measurement is simple and rapid and could be used for on-line process control during mashing. No sample preparation other than filtration is needed.     

铁（Ⅱ）－1－（2－吡啶偶氮）－2－萘酚－TritonX－100显色体系的研究及应用

本文研究了ＴｒｉｔｏｎＸ一１００存在下，铁（Ⅱ）与１－（２－吡啶偶氮）－２－萘酚（ＰＡＮ）的显色反应，在ＰＨ值３．０～９．０范围内，配合物的最大吸收波长为７４０ｎｍ，表现摩尔吸光系数ε＝１．６×１０￣４Ｌ·ｍｏｌ￣（－１）·ｃｍ￣（－１），铁量在０～８０ｕｇ／２５ｍｌ范围内遵守比耳定律。该法用于纯铝、铝合金、铝基稀土合金中微量铁的测定，结果准确。     

ACPI双开关控制器FAN5063

FAN5063是美国快捷公司生产的全兼容ACPI控制芯片，当用作ATX电源时，即可为PCI提供双3．3V电源，也可用SDRAM和RAM BUS供电，另外，FAN5063还集成有许多附加的保护功能。文中介绍了FAN5063芯片的功能，并给出了它的应用电路。     

同步整流在串联锂电池组并行充电系统中的应用

在串联锂电池组并行充电系统中,由于各路反激变换器工作在低电压、大电流的输出状态,从而整流二极管的导通压降成为系统设计不得不考虑的因素。为了提高系统的效率,论文从减少外围电路、降低成本、提高电路可靠性等方面改进,设计了一种基于FAN6204控制的锂电池组并行充电系统的同步整流电路,可以对每一路分别进行同步整流控制,并进行了相应的理论分析和实验验证。实验结果表明,应用同步整流电路后,系统的整体效率提高了6%左右。     

一种控制转换装置的自动测试与故障诊断初探

介绍了某控制转换装置测试仪的自动测试和故障诊断的设计思想,讨论了测试仪的硬软件设计中如何实现自动测试,以及利用FAN算法来计算故障定位测试向量的故障诊断思想和方法。该测试仪总体设计可靠性高,还有故障定位的功能,智能化程度高。可以在很大的程度上测试控制转换装置的功能和排除控制转换装置的故障。     

LCD背光照明四灯管CCFL电子变压器

CCFL被广泛用作大尺寸LCD的背光源。文中重点介绍了基于控制器FAN7548的四灯管CCFL电子变压器电路功能、特点及工作原理。     

The Application of Near Infrared Spectroscopy to Evaluate Malting Quality

Near infrared (NIR) spectroscopy is a rapid technique which is used within plant breeding programs for the analysis of many grain traits. This study investigated the application of NIR analysis of wort samples to select malting quality cultivars in a barley breeding program. An automatic sampling and data capture system was developed which consisted of a Perten filter NIR instrument with a flow through cell module operating in transflectance mode interfaced with a computer, peristaltic pump and sample changer. Calibrations for hot water extract, free alpha-amino nitrogen and soluble protein were developed using multiple linear regression analysis based on four wavelength terms for each trait. The correlation coefficients for both calibration and prediction data sets were highly significant (P<0.01) and the standard error of prediction was similar to that obtained by standard methods. Cultivars with known malting quality were included in the experiments and their ranking by NIR was consistent with the standard methods. The reported calibrations have been used for over four years to screen early generation breeding lines for malting quality.     

Changes in Sorghum Malt During Storage

The diastatic power of the freshly kilned sorghum malt at 68.1°WK had a 29% drop after six months of storage. Freshly kilned sorghum malt displayed high wort turbidity (4.9 EBC) which dropped to 0.95 EBC and 1 EBC after 2 and 6 months of storage respectively. The colour of the malt worts faded slightly over the trial period from 7.6 EBC in freshly kilned malt to 6.8 EBC after six months. Extract remained fairly steady throughout the study period most likely due to the use of external amylolytic enzymes during mashing. The protein in extract/protein in grain fluctuated between 46.6% in the freshly kilned malt to 43.2% at the end of six months. The apparent extract after final attenuation (AEFA) indicates more fermentability beginning from two months after storage. Free α‐amino nitrogen (FAN) dropped from 238 mg/L to 194 mg/L after six months of storage. Mash filtration with a micro‐mash filter remained prolonged (86–93 min) throughout the six months of storage.