Ib, Peb Lub Ntsiab Lus thiab Kev Tshaj Tawm ntawm Kev Sib Txuas Hluav Taws Xob
Kev tsim ntawm electromagnetic cuam tshuam (EMI) yuav tsum muaj peb lub ntsiab lus ib txhij: cuam tshuam qhov chaw, coupling txoj kev, thiab cov khoom rhiab heev. Hauv kev lag luam ib puag ncig, cov peev txheej ntawm kev cuam tshuam muaj xws li:
Inverter: Cov kev sib haum xeeb tam sim no (2-50kHz) tsim los ntawm nws cov PWM kev hloov pauv yog ua los ntawm cov kab hluav taws xob, thaum cov khoom siv hluav taws xob tsim cov kav hlau txais xov kom tawg cov hluav taws xob hluav taws xob ntau zaus (100kHz-30MHz).
Lub cev muaj zog: hluav taws xob hluav taws xob hluav taws xob tsim los ntawm kev sib hloov ntawm txhuam (1-100MHz), nrog rau cov hlau nplaum sib nqus los ntawm kev hloov pauv hauv winding tam sim no (50Hz thiab nws cov harmonics).
Vuam tshuab: Lub siab - siv hluav taws xob hluav taws xob mem tes (0.1-10MHz) tsim los ntawm cov txheej txheem arc vuam tuaj yeem tawg mus txog kaum meters.
Cov khoom siv sib txuas lus wireless: Wi-nkaus / Bluetooth zaus bands (2.4GHz / 5GHz) sib tshooj nrog rhiab zaus bands ntawm LCD tswj circuits.
Kev cuam tshuam invades LCD system los ntawm txoj hauv qab no:
Conductive coupling: Siv lub zog thiab cov kab teeb liab ua cov khoom thauj, cuam tshuam ncaj qha rau hauv Circuit Court.
Radiation coupling: Qhov chaw electromagnetic tsis cuam tshuam qhov cuam tshuam ntawm PCB thaiv lossis cov khoom txuas los ntawm cov kav hlau txais xov.
Common impedance coupling: Muaj ib qho impedance nyob rau hauv grounding circuit, uas ua rau cuam tshuam tam sim no los ntawm cov khoom siv.
2, Kev Tsim Kho Kev Tiv Thaiv Technology System
1. Shielding tsim: Thaiv qhov kev nthuav tawm ntawm electromagnetic tsis
Hlau plhaub shielding: siv aluminium alloy los yog galvanized steel phaj plhaub, nrog ib tug tuab ntawm ntau tshaj los yog sib npaug zos rau 1.5 hli kom ua tau zoo attenuation. Piv txwv li, cov chaw tsim khoom siv tshuaj lom neeg tau ua tiav kev tiv thaiv kev ua haujlwm ntawm ntau dua 40dB hauv 30MHz-1GHz zaus band los ntawm kev ua kom zoo ntawm lub plhaub qauv. Cov ntsiab lus tseem ceeb tsim muaj xws li:
Kev txuas ntxiv ntawm kev tiv thaiv lub cev: Qhov dav ntawm lub plhaub qhov sib txawv yuav tsum tswj tsis pub dhau 0.1 hli, thiab cov ntaub qhwv los yog lub caij nplooj ntoos hlav yuav tsum tau siv rau kev sib txuas hluav taws xob.
Aperture tswj: Lub tshav kub dissipation qhov txais yuav ib tug honeycomb tsim, nrog ib tug aperture ntawm tsawg tshaj li los yog sib npaug rau λ/20 (qhov twg λ yog qhov siab tshaj plaws cuam tshuam zaus wavelength).
Zaub qhov rais ua: Siv ITO conductive iav (nto kuj tsawg dua los yog sib npaug rau 10 Ω / □) los yog hlau mesh shielding, nrog lub teeb transmittance ntawm ntau dua los yog sib npaug rau 85%.
Internal shielding cais: Siv lub zos shielding rau rhiab circuit modules:
Lub ntsiab tswj nti: siv tooj liab ntawv ci shielding npog, grounding kuj tsawg dua los yog sib npaug li 10m Ω.
Fais fab module: Nruab ib lub nplhaib sib nqus nyob ib ncig ntawm DC -DC converter kom txo cov suab nrov.
Lub teeb liab sib txuas: Siv cov khoom siv tiv thaiv (xws li D-sub hom), thiab solder txheej thaiv 360℃rau lub dav hlau hauv av PCB.
2. Lim tshuab: Ncua kev cuam tshuam
Fais fab kawg filtering: Nruab ib lub lim EMI ntawm lub LCD fais fab input kawg, nrog rau qhov yuav tsum tau parameter:
Insertion poob: Ntau dua lossis sib npaug rau 40dB hauv 150kHz-30MHz zaus band
Rated tam sim no: Xaiv raws li qhov yuav tsum tau ua, tawm hauv 20% npoo
Cov dej ntws tam sim no: Tsawg dua lossis sib npaug rau 1mA (raws li IEC 60950 tus qauv kev nyab xeeb)
Cov ntaub ntawv kawm ntawm lub tsheb ntsuas qhia tau hais tias tom qab siv ob -theem LC lim, qhov kev cuam tshuam ntawm cov kab hluav taws xob tau txo qis ntawm 45dB μ V mus rau 20dB μ V.
Cov kab teeb liab lim: Rau cov kab teeb liab video xws li RGB / LVDS, kev sib xyaw ua ke ntawm hom choke coil (CMCC) thiab txawv hom capacitor yog siv los lim:
CMCC inductance: 100-1000 μ H (xaiv raws li lub teeb liab zaus)
Sib txawv capacitance: 0.1-1 μ F (X2 hom kev nyab xeeb capacitor)
3. Kev ua kom zoo ntawm cov av hauv av
Ib qho yooj yim taw tes grounding zoo: Hauv qis- zaus circuits (f<1MHz), all grounding wires are converged to a common grounding point to avoid the formation of a ground loop. A certain power monitoring instrument reduced the common mode interference voltage from 5V to 0.5V by reconstructing the grounding system.
Multi point grounding strategy: In high-frequency circuits (f>10MHz), PCB multi- txheej board tsim tau txais los tsim kom tiav lub dav hlau hauv av:
Cov dav hlau hauv av segmentation: Digital av thiab analog av txuas ntawm ib qho taw tes los ntawm 0 Ω resistor lossis cov hlaws sib nqus.
Grounding ntawm: Tsawg kawg ib qho av ntawm nrog ib txoj kab uas hla ntawm Ntau dua lossis sib npaug li 0.5 hli yuav tsum tau teem caij rau ib square inch ntawm PCB.
Grounding kuj tswj: xyuas kom meej tias cov av tiv thaiv tsawg dua lossis sib npaug ntawm 4 Ω los ntawm kev ntsuas hauv qab no:
Nce tus naj npawb ntawm grounding electrodes (tsawg kawg 3)
Siv cov reducer (resistivity Tsawg dua lossis sib npaug li 5 Ω·m)
Tsis tu ncua xyuas cov av tiv thaiv (pom zoo ib zaug txhua lub hlis twg)
4. PCB tiv thaiv -kev cuam tshuam tsim
layout optimization:
Cov teeb liab tseem ceeb routing: Qhov ntev ntawm lub moos thiab cov kab teeb liab video yuav tsum tswj tsis pub dhau λ/20 (qhov twg λ yog lub teeb liab wavelength).
Lub Hwj Chim / Av Dav Hlau: Txais 4-txheej board qauv (lub teeb liab lub zog hauv av), lub dav hlau fais fab yog nruj ua ke nrog lub dav hlau hauv av.
Device layout: Analog circuits thiab digital circuits yog teem rau hauv ib cheeb tsam sib cais nrog qhov sib nrug ntawm Ntau dua lossis sib npaug li 5 hli.
Cov specifications:
Kev sib txawv routing: Khaws qhov sib npaug ntawm qhov ntev (qhov yuam kev Tsawg dua lossis sib npaug li 50mil), nrog qhov sib nrug ntawm ob zaug ntawm kab dav.
Serpentine routing: siv rau lub moos teeb liab ncua kev sib txuam, nrog amplitude Ntau dua los yog sib npaug rau 3 npaug ntawm kab dav thiab qhov sib nrug Ntau dua lossis sib npaug li 5 npaug ntawm kab dav.
Filter capacitor kev npaj: 0.1 μ F ceramic capacitor yog nyob ze ntawm lub nti fais fab tus pin (tsawg dua lossis sib npaug li 3 hli), thiab 10 μ F tantalum capacitor yog teem rau ntawm lub hwj chim inlet.
3, Kev txheeb xyuas cov ntaub ntawv siv tau zoo
Case 1: Los tiv thaiv kev cuam tshuam tsim cov cuab yeej petrochemical
Lub LCD ntawm qee qhov kev saib xyuas cov roj av tau pom qhov txawv txav thaum lub sijhawm ua haujlwm vuam. Tom qab kev txheeb xyuas, nws tau pom tias:
Kev cuam tshuam qhov chaw: 1-10MHz electromagnetic pulse generated los ntawm lub tshuab vuam
Txoj kev nthuav dav: Qhov chaw hluav taws xob ua ke rau LCD video teeb liab kab
Kev daws:
Ntxiv ib lub nplhaib sib nqus ferrite (μ r=1000) ntawm txheej txheej ntawm kab teeb liab
Video interface hloov mus rau DVI-D digital interface (nrog muaj zog tiv thaiv- muaj peev xwm cuam tshuam rau kev sib kis sib txawv)
Paste conductive roj hmab (ntim qhov muaj zog tsawg dua lossis sib npaug ntawm 0.01 Ω· cm) ntawm qhov sib txawv ntawm lub plhaub
Tom qab kev siv, lub kaw lus tseem tuaj yeem tso saib ruaj khov thaum lub sijhawm ua haujlwm vuam, thiab qhov ua yuam kev tau poob ntawm 10 ⁻³ mus rau 10 ⁻⁶.
Case 2: Optimization ntawm Kov Screen rau Cov Khoom Siv Tsim Nyog
Lub vijtsam kov ntawm qee yam CNC tshuab cuab yeej tsoo thaum lub sijhawm pib lub cev muaj zog, thiab qhov kev kuaj mob tshwm sim yog:
Kev cuam tshuam qhov chaw: Sib nqus teb hloov pauv tshwm sim los ntawm kev hloov pauv sai ntawm servo lub cev muaj zog tam sim no (50Hz thiab nws cov kev sib haum xeeb)
Txoj kev nthuav dav: Tsim hom kev cuam tshuam los ntawm cov qauv hlau ntawm lub txee
Kev daws:
Ntxiv π - hom lim rau lub hwj chim ntawm lub kov nti (L=100 μ H, C=0.1 μ F)
Lub txee yog ua los ntawm cov khoom tsis yog- hlau nplaum hlau nplaum (μ r ≈ 1)
Ntxiv cov ntaub thaiv npog ntawm lub vijtsam kov thiab lub txee (qhov hluav taws xob tawg ntau dua lossis sib npaug li 10kV)
Tom qab kev kho dua tshiab, qhov kov rhiab heev tau nce los ntawm peb zaug, thiab tus nqi kov tsis tseeb tau raug txo los ntawm 15% mus rau 0.5%.
