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图33-17至图33-23","","文档围绕PFC电流环路稳定性与最小失调电压Vomin的推导及工程实现展开。内容给出占空比与电流环路稳定/不稳定条件，并说明前沿调制配合斜坡补偿时稳定性可在任意占空比下维持。进一步比较8引脚CM6803/04、ML4803与改进的CM6805/CM6903/04方案，讨论电阻、电容与二极管的取舍，给出RAc选取原则、启动时间估算，以及IsENSE与IAc信号叠加关系与轻负载高电网电压下THD影响。",{"@graph":69,"@context":122},[70,84,105],{"@type":71,"itemListElement":72},"BreadcrumbList",[73,77,79,82],{"item":74,"name":75,"@type":76,"position":8},"https://docshare.wps.com","Home","ListItem",{"item":78,"name":9,"@type":76,"position":14},"https://docshare.wps.com/document/",{"item":80,"name":20,"@type":76,"position":81},"https://docshare.wps.com/document/exam/",3,{"item":83,"name":65,"@type":76,"position":19},"https://docshare.wps.com/document/design-notes-on-minimum-offset-voltage-for-cm680304-and-ml4803-figures-33-17-to-33-23/559977/",{"url":83,"name":65,"@type":85,"image":86,"author":91,"headline":65,"publisher":94,"fileFormat":97,"inLanguage":63,"description":67,"dateModified":98,"datePublished":99,"encodingFormat":97,"isAccessibleForFree":100,"interactionStatistic":101},"DigitalDocument",{"url":87,"@type":88,"width":89,"height":90},"https://docshare.wps.com/thumbnails/design-notes-on-minimum-offset-voltage-for-cm680304-and-ml4803-figures-33-17-to-33-23/559977.png","ImageObject",300,407,{"name":92,"@type":93},"Jacob","Person",{"url":74,"name":95,"@type":96},"DocShare","Organization","application/pdf","2026-11-10","2026-10-12",true,{"@type":102,"interactionType":103,"userInteractionCount":14},"InteractionCounter",{"@type":104},"ViewAction",{"@type":106,"mainEntity":107},"FAQPage",[108,114,118],{"name":109,"@type":110,"acceptedAnswer":111},"电流环路稳定与否如何与占空比D对应？","Question",{"text":112,"@type":113},"当D大于50%时电流环路稳定；当D小于50%时电流环路处于不稳定状态。采用具备斜坡补偿的前沿调制电路后，无论占空比如何变化电流环路都将维持稳定。","Answer",{"name":115,"@type":110,"acceptedAnswer":116},"文中提到的最坏工况是什么，以及此时电感电流变化率如何处理？",{"text":117,"@type":113},"最恶劣条件出现在占空比D=0且Vn=380V。此时给出了电感电流i的变化率表达式，用于后续失调电压与斜坡补偿差异分析。",{"name":119,"@type":110,"acceptedAnswer":120},"CM6805/CM6903/04相较ML4803的关键外部电路调整有哪些？",{"text":121,"@type":113},"通过修改后可降低Boost输出电容Ca、Cs的额定耐压，并去掉ML4803原引脚3外接的3个电阻、2个电容和1个二极管，同时也去掉原C2、C₆、R₂、R₇、R₆等元件，并修改U₂、R₁₈电路；此外在PFC系统中不再需要负极性的充电泵电路，改用RAc连接到电网整流输出端与集成电路9引脚IAc之间。","https://schema.org",{"og:url":83,"og:type":124,"og:title":65,"og:site_name":95,"og:description":67},"article",{"robots":126,"canonical":83},"index,follow",{"doc_id":128,"site_id":62},559977,1791801747,{"code":4,"msg":5,"data":131},{"doc_id":128,"user_id":132,"nickname":92,"user_avatar":133,"doc_module":4,"category_id":19,"category_name":20,"doc_title":65,"doc_description":67,"doc_content":134,"file_id":135,"file_url":136,"file_type":137,"file_size":138,"view_count":14,"is_deleted":4,"is_public":8,"is_downloadable":8,"audit_status":8,"page_count":24,"language":139,"language_code":63,"site_id":62,"html_lang":140,"table_of_contents":141,"faqs":142,"seo_title":143,"seo_description":67,"update_tm":129,"read_time":144,"preview_page_count":4},962084931830,"https://ap-avatar.wpscdn.com/davatar_a8503ba1806abce46bf441b54a3ca4cd","D大于50%,说明电流环路是稳定的；当占空比D小于50%时，则电流环路处于不稳定状态。而当电流模式变换器采用具备斜坡补偿的前沿调制电路时，那么无论占空比的数值如何变化，电流环路都将维持稳定。  \n在下面9个A、A₁、A₂、B、B₁、B₂、H和h之间的关系式中，可推导得到下列的公式，但它们并不代表相应的物理特性  \nA=A₁+A₂B=B₁+B₂H-h=(A₂+B₂)m  \n根据在电感器电流斜坡中的这些关系式，补偿斜坡和电感器电流的差异为  \n对于一个稳定的电流环路，存在下述方程式  \n并且  \nm>0.5×m₁  \n只用8引脚CM6803/04和ML4803时，最恶劣的条件出现在当占空比D=0和Vn=380V时。此时的电感电流i变化率为  \n式中：RF、CF分别是滤波电阻、电容。所以，当频率为70kHz时  \n式中：最小失调电压值Vomin波形可由图33-17表示。  \n引脚1外接电阻器电路如图33-18所示。  \n图33-17最小失调电压值波形  \n图33-18引脚1外接电阻器电路  \n图33-19采用ML4803的原设计电路  \n对于8个引脚的CM6803/04和ML4803最小失调电压为  \n图33-19是采用ML4803的原设计电路。它的Boost输出电容C、C₃需要额定耐压值高达DC500V。当采用新修改的CM6805和CM6903/04主芯片后，就可以把Ca、Cs的额定电压降低到DC400V;并应当去掉原ML4803引脚3外接的3个电阻、2个电容和1个二极管，也去掉原C2、C₆、R₂、R₇、R₆等；并修改U₂、R₁₈电路。  \n对于8个引脚的CM6803/04和ML4803,当电源处于轻负载和电网高电压条件时，最小的失调电压Vomin是反比于PFC栅极信号脉冲的占空比。对于IsENsE脚的失调电压有影响的IC外部电路元器件如图33-20所示。  \n图33-20对Isse脚失调电压有影响的IC外部电路元器件  \n当采用新改进的CM6805和CM6903/04后，不需再使用泄放电阻器，而是改用RAc接在电网整流输出端与集成电路9引脚IAc之间。另外，在PFC系统也不需要再用负极性的充电泵电路。  \n在集成电路IAc脚设计RAc电阻值时应注意：根据经验数据，当采用的Boost电感器数值大于500μH时，可以工作的RAc值取800kΩ。如果Rc=500kΩ,那么起动时间为  \nTsu up≈15VCvα[(VInms min/800kΩ)—100μA]  \n若Cvα=10μF,并且VINme nin=AC80V,那么起动时间约为2.5s。  \n在IsENSE脚的电流输出为  \nIsENSE-OUT=Asin(2πft)  \n而在IAc脚的电流信号为  \nIAc=Bsin(2πft)  \n因此这两个信号叠加后则为  \n(IsENSE-OLT)+IAc=(A+B)sin(2πft)  \n在IC两引脚的输入信号叠加波形如图33-21所示。注意在轻负载和高电网电压条  \n件下工作时，IAc会使电源的总谐波失真(THD)增大。  \n+  \n图33-21在IC两引脚的输入信号叠加波形  \n另外，对于复合PFC/PWM芯片CM6800系列或者CM6903系列，VB脚和VEAc脚的外部电路结构与内部GMv单元相关连线，如图33-22所示。  \n图33-22 VB和VEAc两引脚外电路  \n因为  \n所以，环路增益可由下式得到  \n当采用CM6800系列芯片时  \n△VEAO=6V—0.625V=5.375V  \n当采用CM6903/04和CM6503/04时  \n△VEAO=(6V一0.625V)/4=1.34V  \n在CM6803/04/05和CM6903/04的脉宽调制PWM控制电路中，还增加了  \n1.5V精密电流比较器CMP和10ms数字式软起动电路。CM6903/04外部电路如图33-23所示。  \n图33-23 CM6503/04外部电路","cbCaiq5RhpxmPN7f","https://ap.wps.com/l/cbCaiq5RhpxmPN7f","pdf",658491,"Chinese","en","# 稳定性判据与斜坡补偿影响\n# A、A₁、A₂、B、B₁、B₂、H与h关系推导\n# 最恶劣条件下的Vomin与电感电流斜率\n# 图33-17至图33-19：最小失调电压波形与原设计电路\n# CM6805/CM6903/04改进方案与元件取舍\n# IsENSE与IAc叠加、轻负载高电压THD影响\n# RAc选取与启动时间估算\n# VB与VEAc外电路及环路增益计算\n# PWM控制电路：CMP与软起动电路","[{\"question\":\"电流环路稳定与否如何与占空比D对应？\",\"answer\":\"当D大于50%时电流环路稳定；当D小于50%时电流环路处于不稳定状态。采用具备斜坡补偿的前沿调制电路后，无论占空比如何变化电流环路都将维持稳定。\"},{\"question\":\"文中提到的最坏工况是什么，以及此时电感电流变化率如何处理？\",\"answer\":\"最恶劣条件出现在占空比D=0且Vn=380V。此时给出了电感电流i的变化率表达式，用于后续失调电压与斜坡补偿差异分析。\"},{\"question\":\"CM6805/CM6903/04相较ML4803的关键外部电路调整有哪些？\",\"answer\":\"通过修改后可降低Boost输出电容Ca、Cs的额定耐压，并去掉ML4803原引脚3外接的3个电阻、2个电容和1个二极管，同时也去掉原C2、C₆、R₂、R₇、R₆等元件，并修改U₂、R₁₈电路；此外在PFC系统中不再需要负极性的充电泵电路，改用RAc连接到电网整流输出端与集成电路9引脚IAc之间。\"}]","CM6803/04和ML4803最小失调电压及PFC环路设计要点 - 图33-17至图33-23 | PDF",13]