Ma muli o ka PCB hoʻonohonoho o ka lako mana, hoʻolauna kēia pepa i ka ʻōnaehana hoʻonohonoho PCB ʻoi loa, nā laʻana a me nā ʻenehana e hoʻonui ai i ka hana o ka module mana switch switch maʻalahi.

Ke hoʻolālā nei i ka hoʻonohonoho lako mana, ʻo ka noʻonoʻo mua kahi o ka loop loop o nā kuapo ʻelua e hoʻololi nei i kēia manawa. 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. I ka loop 1 i hōʻike ʻia ma ke Kii 1, ke komo nei ka mea nona iho i ke komo ʻana o ka capacitor (Cin1) ma o ka MOSFET i ka mea hoʻokomo o loko a me ka capacitor bypass output (CO1) i ka manawa o ka conduction hoʻomau o ka MOSFET kiʻekiʻe loa, a hoʻi hope loa i ka mea hoʻokomo o bypass capacitor.

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

Hōʻike 1 ʻIkepili kiʻi o ka loop i ka mana 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. ʻO ka ikehu i mālama ʻia i loko o ka mea hoʻokomo o loko e kahe ana ma o ka capacitor bypass capacitor a me nā lowOS MOSFEts ma mua o ka hoʻi ʻana i GND (e nānā i ke kiʻi 1). The region where two loops do not overlap each other (including the boundary between loops) is the region with high DI/DT current. ʻO ka capacitor bypass bypass (Cin1) he kuleana nui i ka hāʻawi ʻana i ke alapine kiʻekiʻe i ka mea hoʻololi a hoʻihoʻi i ke alapine kiʻekiʻe i kāna ala kumu.

ʻAʻole lawe ka capacitor bypass capacitor (Co1) i ka nui o ka AC i kēia manawa, akā hana ma ke ʻano he kānana alapine kiʻekiʻe no ka hoʻololi ʻana i ka walaʻau. No nā kumu i luna, pono e hoʻokau i nā mea hoʻokomo a me nā mea hoʻopuka i kahi kokoke loa i kā lākou mau pine VIN a me VOUT ma ka modula. E like me ka mea i hōʻike ʻia i ke Kiʻi 2, hiki ke hoʻoliʻiliʻi i ka inductance i hoʻokumu ʻia e kēia mau pilina e ka hana ʻana i nā uea i waena o nā capacitor bypass a me kā lākou mau pine VIN a me VOUT i ka pōkole a me ka ākea e hiki ai.

Hōʻike 2 loop SIMPLE SWITCHER

ʻO ka hoʻohaʻahaʻa inductance i kahi hoʻolālā PCB he ʻelua mau pono nui. ʻO ka mea mua, hoʻomaikaʻi i ka hana o nā mea e ka hoʻolaha ʻana i ka hoʻoili ikehu ma waena o Cin1 a me CO1. Mālama kēia i ka bypass maikaʻi o ka module, e hoʻoliʻiliʻi i nā piko uila inductive ma muli o ke kiʻekiʻe DI / DT i kēia manawa. Hoʻoemi pū kekahi ia i ke kani o ka hāmeʻa a me ke koʻikoʻi uila e hōʻoia i ka hana maʻamau. ʻO ka lua, hoʻohaʻahaʻa iā EMI.

Hoʻopili nā Capacitors me ka inductance parasite liʻiliʻi e hōʻike i nā ʻano impedance haʻahaʻa i nā alapine kiʻekiʻe, no laila e hōʻemi ana i ka radiation i alakaʻi ʻia. Pākuʻi ʻia nā capacitor pālolo (X7R a i ʻole X5R) a i ʻole nā ​​ʻaoʻao ESR haʻahaʻa ʻē aʻe. Hiki ke pāʻani i nā capacitor hoʻokomo hou inā kau ʻia nā capacitor hou ma kahi kokoke i ka welau GND a me VIN. 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.

Hoʻowahāwahā pinepine ʻia ka hoʻolālā ala kaapuni i kēia manawa, akā he kuleana nui ia i ka hoʻonui ʻana i ka hoʻolālā lako mana. 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.

ʻO nā pine o ka honua (me nā pads ʻōlohelohe), nā mea hoʻokomo a me nā mea hoʻopuka, nā capacitor hoʻomaka palupalu, a me nā mea pale manaʻo i ka module e hoʻopili ʻia i ka papa loop ma ka PCB. Hiki ke hoʻohana ʻia kēia papa loop ma ke ala hoʻi me ke ʻano haʻahaʻa haʻahaʻa loa a me ke ʻano o ka hoʻomehana wela i kūkā ʻia ma lalo.

ANA. 3 Skema kiʻikuhi o ka module a me PCB ma ke ʻano impedance thermal

E hoʻokau ʻia ka mea pale manaʻo ma kahi kokoke loa i ka pin FB (manaʻo pane) o ka modula. 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.

Nā Manaʻo Hoʻolālā Heat Disissation

ʻO ka hoʻonohonoho kaulike o nā modula, ʻoiai e hāʻawi ana i nā pono uila, he hopena maikaʻi ʻole i ka hoʻolālā hoʻoneʻe wela, kahi e hoʻopau ʻia ai ka mana like mai nā wahi liʻiliʻi. 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. Kōkua ka pale e hāʻawi i ka impedance thermal haʻahaʻa loa mai nā MOSFEts kūloko, kahi e hoʻonui ai i ka hapa nui o ka wela, i ka PCB.

ʻO ka impedance pumehana (θJC) mai ka huina semiconductor i ka pūʻolo waho o kēia mau mea ʻo 1.9 ℃ / W. ʻOiai ke hoʻokō ʻana i kahi ʻoihana θJC alakaʻi alakaʻi ʻoi aku ka maikaʻi, kahi manaʻo haʻahaʻa θJC ke kumu ʻole ke koʻikoʻi impedance (θCA) o ka pūʻolo waho i ka lewa! Inā ʻaʻole hāʻawi ʻia kahi ala dissipation heat-impedance haʻahaʻa i ke ea e pili ana, e hōʻiliʻili ka wela ma ka pale kapa ʻole a ʻaʻole hiki ke hoʻopau ʻia. No laila he aha ka mea e hoʻoholo ai iā θCA? The thermal resistance from bare pad to air is completely controlled by the PCB design and associated heat sink.

I kēia manawa no ka nānā wikiwiki ʻana pehea e hoʻolālā ai i kahi PCB maʻalahi me ka ʻole o nā fin, kiʻi 3 e hōʻike ana i ka module a me PCB ma ke ʻano he impedance wela. Ma muli o ke kiʻekiʻe o ka impedance thermal ma waena o ka huina a me ka piko o ka pūʻali waho i ka hoʻohālikelike ʻia o ka impedance mehana mai ka hui ʻana i ka pale kapa ʻole, hiki iā mākou ke nānā ʻole i ke ala dissipation wela θJA i ka manawa o ka manaʻo mua o ke kūpale kūpale mai ka hui ʻana i ka lewa puni (θJT).

ʻO ka hana mua i ka hoʻolālā hoʻoneʻe wela e hoʻoholo i ka nui o ka mana e hoʻopau ʻia. Hiki ke helu maʻalahi ʻia ka mana i hoʻopau ʻia e ka module (PD) me ka hoʻohana ʻana i ka pakuhi hoʻokō (η) i paʻi ʻia i ka papa ʻikepili.

Hoʻohana mākou i nā palena o ke ana wela o ka mahana nui i ka hoʻolālā, TAmbient, a me ke ana wela i helu ʻia, ʻo TJuncTIon (125 ° C), e hoʻoholo ai i ke kūpaʻa wela e pono ai no nā modula i hoʻopili ʻia ma ka PCB.

ʻO ka mea hope loa, ua hoʻohana mākou i kahi maʻalahi maʻalahi o ka nui o ka hoʻoili wela convective ma ka ʻili PCB (me nā ʻāpana keleawe 1-auneki i hōʻino ʻole ʻia a me nā lua poho wela ma nā papa luna a me lalo) e hoʻoholo ai i kahi o ka pā i koi ʻia no ka hoʻopau wela.

ʻAʻole pili ka ʻāpana PCB i koi ʻia i ke ʻano o nā puka dissipation wela e hoʻoili i ka wela mai ka papa metala luna (pili ka pūʻolo i ka PCB) i ka papa hao lalo. Ke lawelawe nei ka papa lalo ma ke ʻano he ʻelua papa o ka honua i hiki i ka convection ke hoʻololi i ka wela mai ka pā. Ma ka liʻiliʻi 8 a 10 mau anuanu e pono e hoʻohana ʻia no ka pili ʻana o kahi o ka papa e kūpono. ʻO ke kūpale kūpale o ka puhi wela e hoʻokokoke ʻia e ka hoʻohālikelike e hiki mai ana.

Pili kēia hoʻokokoke i kahi puka maʻamau o 12 mils diameter me ka 0.5 oz keleawe sidewall. E like me ka nui o nā lua poho wela e pono ai e hoʻolālā ʻia ma ka wahi holoʻokoʻa ma lalo o ka pā ʻaʻohe, a ʻo kēia mau lua wela e hana i kahi hoʻonohonoho me kahi ākea o 1 a 1.5mm.

ka hopena

Hāʻawi ka mana uila SIMPLE SWITCHER i kahi koho i nā hoʻolālā lako mana paʻakikī a me nā hoʻonohonoho PCB maʻamau e pili ana i nā mea hoʻololi DC / DC. ʻOiai ua hoʻopau ʻia nā pilikia o ka hoʻonohonoho ʻana, pono e hana ʻia kekahi hana ʻenekini e hoʻonui i ka hana o ka module me ka bypass maikaʻi a me ka hoʻolālā dissipation wela.