《電子技術應用》
您所在的位置:首頁 > 模擬設計 > 設計應用 > 單電源電路測量-48V高端電流
單電源電路測量-48V高端電流
摘要: 標稱-48V的電源廣泛地用于無線基站和其他網絡中心站的通訊設備,能在-48V到-60V范圍內變化。測量其電流典型地需要±15V雙電源供電的器件。不使用負電源可以減少系統的復雜程度和費用。本設計方案使用Analog Devices公司的AD629差分放大器和AD8603運算放大器,測量-48V到-60V的電流,且僅需要單一正電源供電。
Abstract:
Key words :

  這個電路使用單一正電源測量-48V高端電流

  標稱-48V的電源廣泛地用于無線基站和其他網絡中心站的通訊設備,能在-48V到-60V范圍內變化。測量其電流典型地需要±15V雙電源供電的器件。不使用負電源可以減少系統的復雜程度和費用。本設計方案使用Analog Devices公司的AD629差分放大器AD8603運算放大器,測量-48V到-60V的電流,且僅需要單一正電源供電(參考文獻1和2)。

  圖1顯示了AD629和AD8603如何在-48V共模電壓面前測量電流。下面的公式表明AD629差分放大器能調節超過電源范圍的電壓:VCOM_MAX=20×(VS–1.2)–19×VREF, 和VCOM_MIN=20×(–VS+1.2)–19×VREF。共模輸入范圍為–71到+121V,帶一個5V參考電壓。電流I流過分流電阻Rs,由差動放大器形成微分電壓。AD629固定為1倍增益,那么輸出電壓為I×RS+VREF。AD8603執行減法器的功能,所以可以抵消共模電壓VREF,將增益應用到有用信號I×RS。以20因數放大信號到ADC的2.5V全量程范圍。

AD629和AD8603如何在-48V共模電壓面前測量電流

  本設計方案使用AD8603,因為其具有低輸入偏置電流和低偏移量漂移。此外,軌對軌輸出允許其和ADC分享同一個電源。這個階段,減法器抵消了電壓參考的5V共模信號。形成減法器的四個電阻必須具有與獲得最大共模抑制比相匹配的比例。如果不能得到適合的匹配電阻,可以使用AD623單電源儀表放大器替代AD8603,確保高共模抑制比。

  兩個放大器的偏移量、輸入偏置電流和共模抑制比誤差,導致AD8603輸出的最大誤差為163mV。這個計算假設電阻為0.01%的匹配率。該電路經歷過并聯50、100和200mΩ的Rs來檢證。

  英文原文:

  Single-supply circuit measures –48V high-side current

  This circuit measures ?48V high-side current using a single positive supply.

  Wenshuai Liao, Analog Devices, Beijing, China; Stephen Lee, Analog Devices, Wilmington, MA; and Yanhui Zhao, Beihang University, Beijing, China; Edited by Charles H Small and Fran Granville -- EDN, 2/21/2008

  The nominal –48V rail, which finds wide use in wireless base stations and other telecommunications equipment in network central offices, can vary from –48 to –60V. Measuring its current draw typically requires components that operate on ±15V dual supplies. Eliminating the negative supply would reduce system complexity and cost. This Design Idea uses an AD629 difference amplifier and an AD8603 operational amplifier, both from Analog Devices, to measure current at –48 to –60V and operates from a single positive-power supply (reference 1 and reference 2).

  Figure 1 shows how the AD629 and AD8603 measure current in the presence of a –48V common-mode voltage. The following equations demonstrate how the AD629 difference amplifier can condition voltages beyond its supply ranges: VCOM_MAX=20×(VS–1.2)–19×VREF, and VCOM_MIN=20×(–VS+1.2)–19×VREF. With a 5V reference, the common-mode input range is –71 to +121V. The current, I, flows through the shunt resistor, RS, causing a differential voltage, which the difference amplifier senses. The AD629 has a fixed gain of one, so the output voltage is I×RS+VREF. The AD8603 functions as a subtractor so that it can reject the common-mode voltage, VREF, and apply gain to the signal of interest, I×RS. A factor of 20 amplifies the signal to span the 2.5V full-scale range of the ADC.

 

  This Design Idea uses the AD8603 because it has low input-bias current and low offset drift. In addition, the rail-to-rail output allows it to share the same supply as the ADC. In this stage, the subtractor rejects the 5V common-mode signal from the voltage reference. The four resistors that form the subtractor must have matched ratios to obtain maximum common-mode rejection. If you cannot obtain tightly matched resistors, you can use an AD623 single-supply instrumentation amplifier in place of the AD8603, ensuring high common-mode rejection.

  Offset, input-bias-current, and common-mode-rejection errors from both amplifiers result in a 163-mV maximum error at the output of the AD8603. This calculation assumes resistors with a 0.01% ratio match. The circuit was verified on the bench using 50-, 100-, and 200-mΩ shunts for RS.

  References

  “High Common-Mode Voltage, Difference Amplifier AD629,” Analog Devices, 1999 to 2007.

  “Precision Micropower, Low Noise CMOS Rail-to-Rail Input/Output Operational Amplifiers AD8603/AD8607/AD8609,” Analog Devices, 2005.
 

此內容為AET網站原創,未經授權禁止轉載。
主站蜘蛛池模板: 埃及艳后h版2性传奇 | 久久成人a毛片免费观看网站 | 黄视频在线免费看 | 免费观看亚洲视频 | 九九在线观看免费视频 | 久久精品国产72国产精福利 | 欧美69式囗交视频 | 青草视频在线观看免费 | 四虎成人在线视频 | 欧美男女性生活视频 | 婷婷亚洲天堂 | 久久久国产精品视频 | 狠狠躁夜夜躁人人爽天天3 欧美日日夜夜 | 99久久国产视频 | 娼年中文字幕 | 国产一级国产一级碟片60分钟 | 秋霞午夜鲁丝片午夜精品久 | 成人综合久久综合 | 国产综合第一页在线视频 | 开心激情播播网 | 欧美亚洲视频一区 | 蜜桃视频一区二区三区 | 欧美日韩亚洲成人 | 欧美日韩中文在线观看 | 日韩精品在线观看视频 | www.亚洲成人.com | 99视频免费在线 | 丁香激情综合色伊人久久 | 午夜精品久久久 | 精品女同一区二区三区免费站 | 伊人免费视频 | 国产亚洲福利一区二区免费看 | 免费久久精品 | 中国一级毛片视频免费看 | 国产成人综合久久精品亚洲 | 欧美女人性生活视频 | 国内自拍区 | 国产精品公开免费视频 | 久久免费视频精品 | 免费看成人毛片 | 激情五月黄色 |