《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: 欧美性开放视频 | 99热成人精品免费久久 | 猛鬼山坟2完整版国语版 | 蜜桃视频一区二区 | 国产精品99久久久久久www | 91社区视频 | 精品九九久久国内精品 | 久久婷婷激情综合中文字幕 | 国产欧美专区在线观看 | 久久天天躁夜夜躁狠狠 | 黄色在线视频观看 | 国产亚洲欧美在线视频 | 久草综合在线视频 | 男女网站在线观看 | 看国产毛片 | 国产免费私拍一区二区三区 | 欧美中文综合在线视频 | 精品四虎免费观看国产高清午夜 | 五月天婷婷精品免费视频 | 青青久久网 | 日韩在线欧美高清一区 | 国产精品一区二区三区久久 | 黄色工厂在线观看 | 色婷婷六月天 | 成人国产亚洲欧美成人综合网 | 亚洲国产精品人人做人人爽 | 成人夜色视频 | 欧美同志网址 | 免费视频不卡一区二区三区 | 国产精品久久人人做人人爽 | 精品999久久久久久中文字幕 | 久草国产在线视频 | 欧美日韩亚洲国产精品一区二区 | 日日摸夜夜摸狠狠摸97 | 五月婷婷综合在线 | 综合精品 | 国产伦精品一区二区三区视频金莲 | 华人永久免费视频 | 欧美国产一区二区 | 成人av电影网站 | 开心激情小说网 |