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Halin da aka saba: Injiniyan ƙira yana saka ƙwanƙwasa ferrite a cikin da'irar yana fuskantar matsalolin EMC, kawai ya gano cewa a zahiri yana sa amo da ba a so ya fi muni. Ta yaya hakan zai kasance?
Amsar wannan tambayar tana da sauƙi, amma maiyuwa ba za a iya fahimtar ta ba sai ga waɗanda suke ciyar da mafi yawan lokaci don magance matsalolin EMI. tebur wanda ke lissafin lambar ɓangaren su, rashin ƙarfi a wasu mitar da aka ba (yawanci 100 MHz), juriya na DC (DCR), matsakaicin ƙimar halin yanzu da wasu bayanai masu girma (duba Table 1) Komai kusan daidai yake.Abin da ba a nuna a cikin bayanan ba. takardar ita ce bayanin kayan aiki da kuma daidaitattun halayen aikin mitoci.
Ferrite beads ne m na'urar da za su iya cire amo makamashi daga kewaye a cikin nau'i na zafi.Magnetic beads haifar da impedance a cikin m mitar kewayon, game da shi kawar da duk ko wani ɓangare na maras so amo makamashi a cikin wannan mita mita.Don DC lantarki aikace-aikace (. kamar layin Vcc na IC), yana da kyawawa don samun ƙarancin juriya na DC don kauce wa babban hasara na wutar lantarki a cikin siginar da ake buƙata da / ko ƙarfin lantarki ko tushen yanzu ( asarar I2 x DCR) . Duk da haka, yana da kyawawa don samun high impedance a cikin wasu mitar mitar da aka ƙayyade.Saboda haka, impedance yana da alaƙa da kayan da aka yi amfani da su (permeability), girman girman ƙwanƙwasa ferrite, yawan iska, da tsarin iska. , da karin windings, da mafi girma da impedance, amma kamar yadda jiki tsawon na ciki nada ya fi tsayi, wannan kuma zai haifar da mafi girma juriya na DC.The rated halin yanzu na wannan bangaren ne inversely gwargwado da DC juriya.
Ɗaya daga cikin mahimman abubuwan da ake amfani da su na ferrite beads a cikin aikace-aikacen EMI shine cewa sashin dole ne ya kasance a cikin lokacin juriya. Menene ma'anarsa? A sauƙaƙe, wannan yana nufin cewa "R" (AC resistance) dole ne ya fi "XL" reactance).A mitoci inda XL> R (ƙananan mitar), bangaren ya fi kama da inductor fiye da resistor. mitar da "R" ya fi girma fiye da "XL" ana kiransa "crossover" mita. Ana nuna wannan a cikin Hoto 1, inda mitar crossover shine 30 MHz a cikin wannan misali kuma an yi masa alama da kibiya ja.
Wata hanyar da za a kalli wannan ita ce dangane da abin da bangaren ke aiwatarwa a lokacin inductance da juriya. Kamar yadda yake tare da sauran aikace-aikacen da impedance na inductor ba ya daidaita, wani ɓangare na siginar mai shigowa yana nunawa zuwa tushen. samar da wasu kariya ga kayan aiki masu mahimmanci a gefe na ferrite bead, amma kuma yana gabatar da "L" a cikin kewayawa, wanda zai iya haifar da resonance da oscillation (ringing).Saboda haka, lokacin da magnetic beads har yanzu inductive a cikin yanayi, sashi. na amo makamashi za a nuna da kuma wani ɓangare na amo makamashi zai wuce, dangane da inductance da impedance dabi'u.
Lokacin da ferrite bead yana cikin lokacin juriya, sashin yana aiki kamar resistor, don haka yana toshe makamashin hayaniya kuma yana ɗaukar makamashin daga kewaye, kuma yana ɗaukar shi ta hanyar zafi.Ko da yake an gina shi kamar yadda wasu inductor ke amfani da su. Tsarin iri ɗaya, layin samarwa da fasaha, injina, da wasu kayan aikin guda ɗaya, ƙwanƙwasa ferrite suna amfani da kayan ferrite mai asara, yayin da inductor ke amfani da ƙarancin ƙarfe na Oxygen.
Hoton yana nuna [μ''], wanda ke nuna halin hasarar kayan kwalliyar ferrite.
Gaskiyar cewa an ba da ƙaddamarwa a 100 MHz kuma wani ɓangare ne na matsalar zaɓin. A yawancin lokuta na EMI, rashin daidaituwa a wannan mita ba shi da mahimmanci kuma yana ɓatarwa. Darajar wannan "ma'ana" ba ya nuna ko haɓaka ya karu, raguwa. , ya zama lebur, kuma matsananciyar ta kai ga kololuwar darajarsa a wannan mita, kuma ko kayan yana cikin lokacin inductance ko kuma ya canza zuwa juriya. aƙalla kamar yadda aka nuna a cikin takardar bayanai.Duba Hoto na 3.Dukkan lanƙwasa 5 a cikin wannan adadi na 120 ohm ferrite beads daban-daban.
Sa'an nan, abin da mai amfani dole ne ya samu shi ne madaidaicin magudanar ruwa wanda ke nuna halayen mita na ƙwanƙwasa ƙwanƙwasa. An nuna misalin madaidaicin lanƙwasa na musamman a hoto na 4.
Hoto na 4 yana nuna wata muhimmiyar hujja mai mahimmanci. Wannan ɓangaren an sanya shi azaman 50 ohm ferrite bead tare da mita 100 MHz, amma mitar mitar ta kusan 500 MHz, kuma tana samun fiye da 300 ohms tsakanin 1 da 2.5 GHz. Again, kawai kallon takardar bayanan ba zai bari mai amfani ya san wannan ba kuma yana iya zama yaudara.
Kamar yadda aka nuna a cikin adadi, kaddarorin kayan sun bambanta.Akwai bambance-bambancen ferrite da yawa da ake amfani da su don yin beads. aikace-aikace mita da impedance.
Wata matsalar da ta zama ruwan dare ita ce, masu zane-zanen da'ira a wasu lokuta suna iyakance ga zaɓin ƙwanƙolin ferrite a cikin bayanan da aka amince da su. ba lallai ba ne don kimantawa da amincewa da wasu kayan aiki da lambobi. A cikin 'yan kwanan nan, wannan ya haifar da wasu sakamako masu tsanani na ainihin matsalar hayaniyar EMI da aka kwatanta a sama. Hanyar da ta dace a baya za ta iya amfani da aikin na gaba, ko shi Maiyuwa bazai yi tasiri ba.Ba za ku iya bin hanyar EMI kawai na aikin da ya gabata ba, musamman lokacin da mitar siginar da ake buƙata ta canza ko yawan abubuwan da ke iya haskakawa kamar canjin kayan aikin agogo.
Idan ka kalli magudanar ruwa guda biyu a cikin Hoto na 6, zaku iya kwatanta tasirin abubuwa na sassa guda biyu masu kama da juna.
Don waɗannan nau'o'in guda biyu, ƙaddamarwa a 100 MHz shine 120 ohms. Ga bangaren hagu, ta amfani da kayan "B", matsakaicin matsakaicin shine game da 150 ohms, kuma an gane shi a 400 MHz. Ga bangaren dama. , Yin amfani da kayan "D", matsakaicin matsakaici shine 700 ohms, wanda aka samu a kusan 700 MHz. Amma babban bambanci shine mitar crossover. Babban hasara na "B" abu yana canzawa a 6 MHz (R> XL) , yayin da babban mitar "D" abu ya kasance mai aiki a kusa da 400 MHz. Wane bangare ne daidai don amfani da shi? Ya dogara da kowane aikace-aikacen mutum.
Hoto 7 yana nuna duk matsalolin gama gari waɗanda ke faruwa lokacin da aka zaɓi beads na ferrite da ba daidai ba don murkushe EMI. Siginar da ba ta tace ba yana nuna 474.5 mV da ke ƙasa akan bugun bugun 3.5V, 1 uS.
A sakamakon amfani da kayan rubutu mai tsayi (makircin tsakiya), da rashin daidaito na auna saboda mafi girman adadin saiti na 474.5 mv zuwa 749.8 MV.The Super Hasashe Super Hasashe yana da ƙananan mitar crossover da kyakkyawan aiki.Zai zama abin da ya dace don amfani da shi a cikin wannan aikace-aikacen (hoto a hannun dama) .Ƙararren da ke amfani da wannan ɓangaren an rage shi zuwa 156.3 mV.
Yayin da kai tsaye ta hanyar beads ya karu, ainihin abu ya fara farawa. Ga inductors, ana kiran wannan saturation current kuma an ƙayyade shi a matsayin raguwar kashi a cikin ƙimar inductance. Domin ferrite beads, lokacin da ɓangaren ke cikin lokacin juriya, Sakamakon jikewa yana nunawa a cikin raguwar ƙimar ƙima tare da mita. Wannan raguwa a cikin raguwa yana rage tasirin ferrite beads da kuma ikon su na kawar da EMI (AC) amo. Hoto 8 yana nuna saiti na al'ada na DC bias curves don ferrite beads.
A cikin wannan adadi, an ƙididdige bead ɗin ferrite a 100 ohms a 100 MHz. Wannan shi ne ma'auni na al'ada lokacin da ɓangaren ba shi da halin yanzu na DC. Duk da haka, ana iya ganin cewa da zarar an yi amfani da halin yanzu na DC (misali, don IC VCC). shigarwa), tasiri mai tasiri yana raguwa sosai.A cikin layin da ke sama, don 1.0 A halin yanzu, tasiri mai tasiri yana canzawa daga 100 ohms zuwa 20 ohms. 100 MHz. Watakila ba mahimmanci ba ne, amma wani abu da injiniyan zane dole ne ya kula da shi. Hakazalika, ta hanyar amfani da bayanan halayen lantarki kawai. na bangaren da ke cikin takardar bayanan mai kaya, mai amfani ba zai san wannan abin son rai na DC ba.
Kamar inductor na RF mai girma-girma, jagorar juyawa na coil na ciki a cikin ƙwanƙwasa ferrite yana da tasiri mai girma akan halayen mita na katako. A cikin hoto na 9, an nuna beads ferrite guda biyu 1000 ohm tare da girman gidaje iri ɗaya da kayan iri ɗaya, amma tare da saitunan iska guda biyu daban-daban.
Ƙunƙarar ɓangaren hagu suna rauni a kan jirgin sama na tsaye kuma an tattara su a cikin madaidaiciyar hanya, wanda ke haifar da haɓakawa mafi girma da kuma mafi girman amsawa fiye da sashin da ke gefen dama na rauni a cikin jirgin sama na kwance kuma an ajiye shi a tsaye. zuwa ƙananan capacitive reactance (XC) da ke da alaƙa da rage ƙarfin parasitic tsakanin ƙarshen ƙarshen da na'ura na ciki. Ƙarƙashin XC zai samar da mafi girman girman girman kai, sa'an nan kuma ba da damar impedance na ferrite bead ya ci gaba da karuwa har sai da shi. ya kai mitar girman kai mai girma, wanda ya fi daidaitaccen tsari na bead ɗin ferrite Ƙimar impedance. An nuna maƙallan na biyu na sama 1000 ohm ferrite beads a Figure 10.
Don ci gaba da nuna sakamakon daidaitattun zaɓin bead na ferrite, mun yi amfani da maɓallin gwaji mai sauƙi da allon gwaji don nuna yawancin abubuwan da aka tattauna a sama. "A", "B" da "C", wadanda ke nesa da na'urar fitarwa (TX).
Ana auna siginar siginar a gefen fitarwa na ƙwanƙwasa ferrite a cikin kowane matsayi na uku, kuma an maimaita shi tare da nau'i biyu na ferrite da aka yi da kayan daban-daban. Abu na farko, ƙananan ƙananan hasara na "S", an gwada shi a maki. "A", "B" da "C" Bayan haka, an yi amfani da kayan "D" mafi girma fiye da mita. Ana nuna sakamakon-zuwa-maki ta amfani da waɗannan beads guda biyu na ferrite a cikin Hoto 12.
Ana nuna siginar "ta" ba tare da tacewa ba a cikin layi na tsakiya, yana nuna wasu overshoot da undershoot a kan tasowa da fadowa gefuna, bi da bi. Ana iya ganin cewa yin amfani da madaidaicin abu don yanayin gwajin da ke sama, ƙananan kayan hasara na mitar yana nuna kyakkyawan overshoot. da kuma ingantaccen siginar siginar a kan gefen tasowa da fadowa.An nuna waɗannan sakamakon a cikin layi na sama na Hoto 12. Sakamakon yin amfani da kayan aiki mai mahimmanci zai iya haifar da sautin ringi, wanda ke haɓaka kowane matakin kuma yana ƙara tsawon lokacin rashin zaman lafiya.Wadannan sakamakon gwajin su ne. aka nuna akan layi na ƙasa.
Lokacin kallon ingantaccen EMI tare da mita a cikin babban ɓangaren da aka ba da shawarar (Hoto 12) a cikin hoton kwance wanda aka nuna a cikin Hoto 13, ana iya ganin cewa ga dukkan mitoci, wannan ɓangaren yana rage girman EMI kuma yana rage yawan amo a 30. zuwa kusan A cikin kewayon 350 MHz, matakin yarda ya yi nisa ƙasa da iyakar EMI wanda layin ja ya haskaka.Wannan shine ma'auni na gabaɗaya na kayan aikin Class B (FCC Sashe na 15 a Amurka) Abubuwan "S" da aka yi amfani da su a cikin beads na ferrite ana amfani da su musamman don waɗannan ƙananan mitoci. Ana iya ganin cewa da zarar mitar ta wuce 350 MHz, Kayan "S" yana da tasiri mai iyaka akan asali, matakin amo na EMI wanda ba a tace ba, amma yana rage girman girma a 750 MHz da kusan 6 dB. Idan babban ɓangaren matsalar amo na EMI ya fi 350 MHz, kuna buƙatar. yi la'akari da amfani da mafi girma mitar ferrite kayan wanda iyakar impedance ne mafi girma a cikin bakan.
Tabbas, duk ringing (kamar yadda aka nuna a cikin lanƙwan ƙasa na Hoto 12) galibi ana iya gujewa ta hanyar gwajin aiki na ainihi da / ko software na siminti, amma ana fatan wannan labarin zai ba masu karatu damar ketare kura-kurai da yawa da kuma rage buƙatar yin hakan. zaɓi daidai lokacin ferrite bead, kuma samar da ƙarin "ilimi" farawa lokacin da ake buƙatar beads na ferrite don taimakawa wajen magance matsalolin EMI.
A ƙarshe, yana da kyau a amince da jerin ko jerin ƙwararrun ferrite, ba kawai lamba ɗaya ba, don ƙarin zaɓuɓɓuka da sassaucin ƙira. , musamman ma lokacin da aka yi sayayya da yawa don wannan aikin. Yana da ɗan sauƙi don yin wannan a karo na farko, amma da zarar an shigar da sassan a cikin ma'ajin bayanai a ƙarƙashin lambar sarrafawa, za a iya amfani da su a ko'ina.Abu mafi mahimmanci shi ne cewa aikin mita na sassa daga masu samar da kayayyaki daban-daban yana da kama da juna don kawar da yiwuwar wasu aikace-aikace a nan gaba Matsalar ta faru.Hanya mafi kyau ita ce samun irin wannan bayanai daga masu ba da kaya daban-daban, kuma a kalla suna da kullun impedance. Wannan kuma zai tabbatar da cewa ana amfani da madaidaicin beads don magance matsalar EMI.
Chris Burket yana aiki a TDK tun daga 1995 kuma yanzu shine babban injiniyan aikace-aikacen, yana tallafawa babban adadin abubuwan da ba a so.Burket ya rubuta kuma ya buga takardun fasaha a cikin dandali da yawa.Mr.Burket ya sami haƙƙin mallaka na Amurka guda uku akan maɓallan gani/kanikanci da capacitors.
In Compliance shine babban tushen labarai, bayanai, ilimi da kwarjini ga ƙwararrun injiniyan lantarki da na lantarki.
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