Hauv Tthe EMC tsim ntawm PCB, thawj qhov kev txhawj xeeb yog txheej txheej; Cov txheej txheem ntawm lub rooj tsavxwm yog tsim los ntawm cov khoom siv fais fab, txheej av thiab txheej txheej teeb liab. Hauv EMC tsim cov khoom lag luam, ntxiv rau kev xaiv cov khoom sib txuas thiab tsim qauv, tsim PCB zoo kuj yog qhov tseem ceeb heev.

The key to the EMC design of PCB is to minimize the backflow area and make the backflow path flow in the direction we designed. Txheej txheej tsim yog lub hauv paus ntawm PCB, yuav ua li cas thiaj ua tau haujlwm zoo ntawm PCB txheej tsim los ua kom EMC cov txiaj ntsig ntawm PCB zoo dua?

I. Tsim cov tswv yim ntawm PCB txheej

The core of PCB laminated EMC planning and design is to reasonably plan signal backflow path to minimize the backflow area of signal from the board mirror layer, so as to eliminate or minimize magnetic flux.

Tib pawg tsom iav txheej

Daim iav txheej yog txheej txheej txheej tooj liab-txheej txheej dav hlau (txheej txheej txheej txheej, hauv av txheej) nyob ib sab ntawm txheej teeb liab sab hauv PCB. Cov haujlwm tseem ceeb muaj li nram no:

(1) Txo cov suab nrov rov qab: daim iav txheej tuaj yeem muab txoj hauv kev tsis cuam tshuam rau lub teeb liab txheej rov qab, tshwj xeeb tshaj yog thaum muaj qhov ntws loj tam sim no hauv lub zog faib khoom, lub luag haujlwm ntawm daim iav txheej yog pom tseeb dua.

(2) EMI txo qis: qhov muaj txheej txheej iav txo thaj tsam ntawm lub voj kaw uas tsim los ntawm lub teeb liab thiab rov ua haujlwm thiab txo EMI;

(3) txo cov kab sib chaws: pab tswj cov teeb meem kev sib tshuam ntawm cov teeb liab kab hauv cov kab hluav taws xob nrawm, hloov qhov siab ntawm kab teeb liab los ntawm daim iav txheej, koj tuaj yeem tswj cov kab sib chaws ntawm kab teeb liab, qhov siab me dua, me dua lub crosstalk;

(4) Kev tiv thaiv kev tiv thaiv kom tiv thaiv teeb liab.

Xaiv cov iav txheej

(1) Ob qho khoom siv hluav taws xob thiab lub dav hlau hauv av tuaj yeem siv ua lub dav hlau siv, thiab muaj qee yam kev tiv thaiv ntawm cov thaiv sab hauv;

(2) Relatively speaking, the power plane has a high characteristic impedance, and there is a large potential difference with the reference level, and the high-frequency interference on the power plane is relatively large;

(3) Los ntawm qhov kev xav ntawm kev tiv thaiv, lub dav hlau hauv av feem ntau yog av thiab siv ua qhov taw qhia ntawm qib siv, thiab nws cov kev tiv thaiv tiv thaiv tau zoo dua li ntawm lub dav hlau fais fab;

(4) Thaum xaiv lub dav hlau siv, lub dav hlau hauv av yuav tsum raug xaiv, thiab lub dav hlau fais fab yuav tsum raug xaiv thib ob

Two, magnetic flux cancellation principle

Raws li Maxwell qhov sib npaug, txhua qhov kev siv hluav taws xob thiab sib nqus sib cais ntawm lub cev sib cais lossis cov dej ntws tau sib kis los ntawm thaj tsam nruab nrab ntawm lawv, txawm tias nws yog lub tshuab nqus tsev lossis cov teeb meem. In a PCB, the flux is always propagated in the transmission line. If the rf backflow path is parallel to the corresponding signal path, the flux on the backflow path is in the opposite direction to that on the signal path, then they are superimposed on each other, and the effect of flux cancellation is obtained.

Qhov xwm txheej ntawm kev tshem tawm cov hlau nplaum

Lub hauv paus ntawm kev tshem tawm cov dej ntws yog kev tswj ntawm cov teeb liab rov qab, raws li qhia hauv daim duab hauv qab no:

Txoj cai sab xis piav qhia qhov cuam tshuam ntawm kev tshem tawm cov hlau nplaum

Yuav siv txoj cai tes xis li cas los piav qhia txog kev tshem tawm cov dej sib nqus thaum lub teeb liab txheej nyob ib sab ntawm lub stratum tau piav raws li hauv qab no:

(1) Thaum cov dej ntws tam sim no los ntawm cov xaim, yuav ua kom muaj cov hlau nplaum nyob ib puag ncig cov hlau, thiab cov kev taw qhia ntawm cov hlau nplaum tau txiav txim los ntawm txoj cai sab xis.

(2) thaum muaj ob qhov nyob ze ib leeg thiab txuas mus rau cov xaim, raws li tau hais hauv daim duab hauv qab no, ib qho ntawm cov hluav taws xob ua hluav taws xob kom ntws tawm, lwm tus yog tus coj hluav taws xob kom ntws, yog tias hluav taws xob tam sim no ntws los ntawm xaim yog tam sim no thiab nws rov qab teeb liab tam sim no, tom qab ntawd ob qho kev coj rov qab ntawm tam sim no yog sib npaug, yog li lawv cov hlau nplaum sib npaug, tab sis cov lus qhia yog rov qab,Yog li lawv tshem tawm ib leeg tawm.

Tsib, rau pawg thawj coj tsim qauv

Rau rau txheej, phiaj xwm 3 yog qhov nyiam dua

Ntsuas:

(1) Raws li cov teeb liab txheej nyob ib sab ntawm lub dav hlau siv rov ua dua, thiab S1, S2 thiab S3 nyob ib sab rau lub dav hlau hauv av, qhov ua tau zoo tshaj plaws tshem tawm cov hlau nplaum tshem tawm tau ua tiav. Yog li ntawd, S2 yog txheej txheej txheej uas nyiam, ua raws S3 thiab S1.

(2) Lub dav hlau fais fab nyob ib sab ntawm GND lub dav hlau, qhov nrug nruab nrab ntawm lub dav hlau yog me me heev, thiab nws muaj qhov sib nqus zoo tshaj plaws tshem tawm cov nyhuv thiab lub zog qis lub dav hlau tsis cuam tshuam.

(3) Lub hwj chim tseem ceeb thiab nws cov ntaub pua plag sib xws nyob ntawm txheej 4 thiab 5. Thaum txheej tuab tau teeb tsa, qhov sib nrug nruab nrab ntawm S2-P yuav tsum tau nce thiab qhov sib nrug ntawm P-G2 yuav tsum raug txo (qhov sib nrug ntawm txheej G1-S2 yuav tsum raug txo kom tsawg), yog li txhawm rau txo qhov kev cuam tshuam ntawm lub dav hlau fais fab thiab kev cuam tshuam ntawm lub zog hluav taws xob ntawm S2.

Rau rau txheej, xaiv 4

Ntsuas:

Scheme 4 yog qhov tsim nyog tshaj Scheme 3 rau hauv zos, cov lej me me ntawm cov teeb liab xav tau, uas tuaj yeem muab txheej txheej thaiv zoo heev S2.

Qhov phem tshaj EMC, phiaj xwm 2

Kev tshuaj xyuas: Hauv cov qauv no, S1 thiab S2 nyob ib sab, S3 thiab S4 nyob ib sab, thiab S3 thiab S4 tsis nyob ib sab rau lub dav hlau hauv av, yog li cov txiaj ntsig tshem tawm cov hlau nplaum tsis zoo.

xaus

Specific principles of PCB layer design:

(1) Muaj lub dav hlau av tiav (ntaub thaiv npog) hauv qab ntu tiv thaiv thiab vuam nto;

(2) Sim tsis txhob ncaj qha nyob ib sab ntawm ob lub teeb liab txheej;

(3) Txhua lub teeb liab txheej nyob ib sab ntawm lub dav hlau hauv av kom deb li deb tau;

(4) Cov txheej txheem txheej txheem ntawm qhov nrawm, nrawm, moos thiab lwm yam cim tseem ceeb yuav tsum muaj lub dav hlau hauv av nyob ib sab.