Raws li cov PCB txheej txheem ntawm cov khoom siv hluav taws xob, daim ntawv no qhia txog PCB txheej txheem txheej txheem zoo tshaj plaws, piv txwv thiab cov txheej txheem txhawm rau ua kom muaj txiaj ntsig zoo ntawm kev hloov pauv lub zog hloov pauv yooj yim.

Thaum npaj phiaj xwm phiaj xwm hluav taws xob, thawj qhov kev xav yog thaj tsam lub cev ntawm ob qhov kev hloov pauv tam sim no. Although these loop regions are largely invisible in the power module, it is important to understand the respective current paths of the two loops because they extend beyond the module. Hauv lub voj 1 qhia hauv daim duab 1, tam sim no tus kheej ua tus coj los hla tus capacitor (Cin1) dhau los ntawm MOSFET mus rau sab hauv sab hauv thiab tso tawm bypass capacitor (CO1) thaum lub sijhawm txuas mus tas li ntawm qib siab MOSFET, thiab thaum kawg rov qab los rau qhov input bypass capacitor.

Schematic diagram of loop in the power module www.elecfans.com

Figure 1 Schematic diagram of loop in power module

Loop 2 is formed during the turn-off time of the internal high-end MOSFEts and the turn-on time of the low-end MOSFEts. Lub zog khaws cia hauv lub tshuab hluav taws xob sab hauv ntws los ntawm qhov tso tawm hla lub tshuab hluav taws xob thiab qis kawg MOSFEts ua ntej rov qab mus rau GND (saib Daim Duab 1). The region where two loops do not overlap each other (including the boundary between loops) is the region with high DI/DT current. Cov tswv yim hla dhau lub tshuab hluav taws xob (Cin1) ua lub luag haujlwm tseem ceeb hauv kev muab cov khoom siv hluav taws xob siab tam sim no rau lub hloov pauv thiab rov ua qhov siab tam sim no rau nws txoj hauv kev.

Cov zis hla dhau lub tshuab hluav taws xob (Co1) tsis nqa ntau AC tam sim no, tab sis ua raws li cov lim dej siab rau hloov suab nrov. Rau qhov laj thawj saum toj no, cov tswv yim thiab tso tawm cov khoom tso tawm yuav tsum tau muab tso kom ze li sai tau rau lawv cov VIN thiab VOUT pins ntawm tus qauv. Raws li tau qhia hauv daim duab 2, qhov inductance tsim los ntawm cov kev sib txuas no tuaj yeem ua kom tsawg dua los ntawm kev ua cov thaiv ntawm qhov hla hla lub tshuab hluav taws xob thiab lawv cov VIN thiab VOUT tus pin luv thiab dav li sai tau.

Daim duab 2 SIMPLE SWITCHER lub voj

Kev txo qis inductance hauv PCB txheej txheem muaj ob qhov txiaj ntsig tseem ceeb. Ua ntej, txhim kho kev tiv thaiv kev ua haujlwm los ntawm kev txhawb zog hloov pauv ntawm Cin1 thiab CO1. Qhov no ua kom ntseeg tau tias tus qauv muaj hf zoo hla, txo qis qhov hluav taws xob nce siab vim siab DI/DT tam sim no. Nws kuj tseem txo qis suab nrov ntawm lub tshuab thiab kev ntxhov siab kom ntseeg tau tias ua haujlwm tau zoo. Qhov thib ob, txo EMI.

Cov capacitors txuas nrog cov kab mob tsawg dua inductance ua rau pom cov yam ntxwv tsis muaj zog mus rau qhov ntau zaus, yog li txo kev ua hluav taws xob. Ceramic capacitors (X7R or X5R) or other low ESR type capacitors are recommended. Cov tswv yim txuas ntxiv tuaj yeem tsuas yog nkag los ua si yog tias muaj lub peev xwm ntxiv tso ze ntawm GND thiab VIN xaus. The Power module of the SIMPLE SWITCHER is uniquely designed to have low radiation and conducted EMI. However, follow the PCB layout guidelines described in this article to achieve higher performance.

Txoj kev npaj txoj hauv kev tam sim no feem ntau tsis quav ntsej, tab sis nws ua lub luag haujlwm tseem ceeb hauv kev ua kom zoo tsim cov khoom siv hluav taws xob. In addition, ground wires to Cin1 and CO1 should be shortened and widened as much as possible, and bare pads should be directly connected, which is especially important for input capacitor (Cin1) ground connections with large AC currents.

Cov pins hauv av (suav nrog cov ntaub qhwv tsis muaj ntaub qhwv), cov tswv yim nkag thiab tso tawm lub zog, lub zog pib lub zog, thiab cov lus tawm tswv yim tiv thaiv hauv tus qauv yuav tsum txhua tus txuas nrog txheej txheej ntawm PCB. Cov txheej txheej no tuaj yeem siv ua txoj hauv kev rov qab los nrog qhov tsis tshua muaj inductance tam sim no thiab raws li cov khoom siv cua sov uas tau tham hauv qab no.

TIG. 3 Schematic daim duab ntawm tus qauv thiab PCB raws li kev tiv thaiv cua sov

Cov lus tawm tsam tus neeg tawm tsam yuav tsum tau muab tso kom ze li sai tau rau FB (tawm tswv yim) tus pin ntawm tus qauv. To minimize the potential noise extraction value at this high impedance node, it is critical to keep the line between the FB pin and the feedback resistor’s middle tap as short as possible. Available compensation components or feedforward capacitors should be placed as close to the upper feedback resistor as possible. For an example, see the PCB layout diagram in the relevant module data table.

For AN example layout of LMZ14203, see the application guide document AN-2024 provided at www.naTIonal.com.

Kev Tsim Txom Thaum Tshav Kub Kub

Kev teeb tsa me me ntawm cov qauv, thaum muab cov txiaj ntsig hluav taws xob, muaj qhov cuam tshuam tsis zoo rau kev tsim hluav taws xob cua sov, qhov sib npaug ntawm lub zog tau ploj mus los ntawm qhov chaw me me. To address this problem, a single large bare pad is designed on the back of the Power module package of the SIMPLE SWITCHER and is electrically grounded. Lub ncoo pab muab qhov tsis tshua muaj cua sov tsis zoo los ntawm sab hauv MOSFEts, uas feem ntau tsim kom muaj cua sov feem ntau, rau PCB.

Cov cua sov tsis zoo (θJC) los ntawm cov khoom siv hluav taws xob sib txuas mus rau txheej sab nrauv ntawm cov khoom siv no yog 1.9 ℃/W. Thaum ua tiav kev lag luam-coj θJC tus nqi yog qhov zoo tshaj plaws, tus nqi lowJC qis ua rau tsis muaj kev nkag siab thaum lub cua sov tsis kam (θCA) ntawm cov txheej sab nraud mus rau huab cua zoo heev! Yog tias tsis muaj txoj hauv kev tso cua sov ua kom sov qis rau huab cua ib puag ncig, cua sov yuav nthuav tawm ntawm lub ncoo liab qab thiab tsis tuaj yeem yaj tau. Yog li dab tsi txiav txim siab θCA? The thermal resistance from bare pad to air is completely controlled by the PCB design and associated heat sink.

Tam sim no kom sai saib yuav ua li cas thiaj tsim tau PCB yooj yim yam tsis muaj fins, daim duab 3 qhia txog tus qauv thiab PCB raws li kev tiv thaiv cua sov. Vim tias cov cua sov tsis zoo ntawm kev sib tshuam thiab sab saum toj ntawm pob txheej sab nraud yog qhov sib piv ntau dua li cov cua sov los ntawm kev sib txuas mus rau lub ncoo ncoo, peb tuaj yeem tsis quav ntsej txog θJA cov cua sov ua kom sov thaum thawj zaug kwv yees ntawm qhov kub tsis kam los ntawm kev sib txuas mus rau huab cua ib puag ncig (θJT).

Thawj kauj ruam hauv kev tsim cov cua sov ua kom sov yog txhawm rau txiav txim siab tias lub zog yuav tsum yaj. Lub zog siv los ntawm tus qauv (PD) tuaj yeem suav tau yooj yim siv cov phiaj xwm kev ua tau zoo (η) luam tawm hauv cov ntaub ntawv rooj.

Tom qab ntawd peb siv qhov ntsuas kub ntawm qhov siab tshaj plaws hauv qhov tsim, TAmbient, thiab ntsuas qhov ntsuas kub sib txawv, TJuncTIon (125 ° C), txhawm rau txiav txim siab qhov kub tsis kam uas yuav tsum tau ua rau cov qauv ntim hauv PCB.

Thaum kawg, peb siv qhov kwv yees kwv yees kwv yees qhov siab tshaj plaws ntawm cov cua sov hloov pauv ntawm PCB saum npoo av (nrog rau tsis muaj kev puas tsuaj 1-ooj tooj liab fins thiab ntau lub qhov cua sov tso rau ntawm ob sab saum toj thiab hauv qab hauv qab) txhawm rau txiav txim siab thaj chaw phaj uas xav tau rau kev tso cua sov.

Qhov yuav tsum tau ua rau thaj tsam PCB tsis suav nrog lub luag haujlwm ua los ntawm cov cua sov tso rau qhov uas hloov cov cua sov los ntawm txheej hlau saum toj kawg nkaus (pob tau txuas nrog PCB) mus rau hauv qab txheej hlau. Cov txheej hauv qab ua haujlwm txheej txheej thib ob los ntawm qhov uas convection tuaj yeem hloov cov cua sov los ntawm phaj. Tsawg kawg 8 txog 10 qhov txias yuav tsum tau siv rau thaj tsam thaj tsam kwv yees kom siv tau. Kev tiv thaiv cua sov ntawm lub dab dej kub yog kwv yees los ntawm cov kab zauv hauv qab no.

Qhov kev kwv yees no siv rau qhov raug hla ntawm 12 mils txoj kab uas hla nrog 0.5 oz tooj liab tooj liab. Raws li ntau lub qhov cua sov cua sov qhov ntau li ntau tau yuav tsum tau tsim nyob rau thaj tsam tag nrho hauv qab lub ncoo ncoo, thiab cov cua sov qhov cua qhov yuav tsum tsim ib qho array nrog qhov nrug ntawm 1 txog 1.5mm.

xaus

SIMPLE SWITCHER lub zog hloov pauv muab lwm txoj hauv kev rau cov qauv tsim hluav taws xob nyuaj thiab cov txheej txheem PCB uas cuam tshuam nrog DC/DC hloov pauv. Thaum cov teeb meem teeb tsa tau raug tshem tawm, qee qhov haujlwm ua haujlwm tseem yuav tsum tau ua kom ua kom zoo dua qhov ua tau zoo nrog kev hla dhau thiab tsim cua sov tsim tawm.