Kodi PWM ndi chiyani?

PWM imayimira Pulse Width Modulation. Mukuyatsa ndi kuzimitsa mphamvu yamagetsi pafupipafupi, kusintha chiyerekezo cha-nthawi yozimitsa-kuchepetsa mphamvu yamagetsi. Ndichoncho. Zina zonse ndikungolimbana ndi zotsatira zake.

Tengani magetsi a 12V akuyendetsa LED yomwe ikufunika 3V. Nthawi zambiri mumagwiritsa ntchito choletsa kapena chowongolera mzere, kuyatsa 9V ngati kutentha. Kutaya kopusa. Ndi PWM mumayatsa ndi kuzimitsa 12V yonse mofulumira moti mphamvu yotentha ya LED imapangitsa kuti ituluke. 25% pa ntchito yanu imakupatsani pafupifupi 3V yofanana. Kuwala kwa LED kumawona 12V → 0V → 12V → 0V mwina 1kHz, koma sikungathe kuziziritsa ndikutentha kwambiri, kotero kuwala kumakhala kosasintha.

Mafupipafupi amafunikira. Pang'onopang'ono (pansi pa 100Hz) ndipo mumayamba kuwoneka. Anthu ena amawona kuthwanima mpaka 200Hz. Nthawi zambiri ndimagwiritsa ntchito dimming ya LED pa 20kHz kuti ndikhale wotetezeka-imapangitsanso kuti isamamveke ngati pali makina olumikizana. Kusintha liwiro kumakhudzanso zotayika, koma tifika pamenepo.

Masamu: ngati nthawi yanu ili T ndipo-nthawi ndi t, duty cycle D=t/T. Zosavuta. Mphamvu yoperekedwa ndi pafupifupi D × V_supply × I_load, kuchotsera zotayika. Kutayika kumeneko ndi kumene zinthu zimakhala zosangalatsa.

Chifukwa choyamba: magwiridwe antchito. MOSFET mu machulukidwe akutsikira mwina 0.1-0.2V pamafunde oyenera. MOSFET imachotsa ma microamp. Chifukwa chake mwina mukutaya (0.1V × pano) kapena kwenikweni palibe. Yerekezerani izi ndi chowongolera chowongolera chomwe chikugwetsa 9V nthawi zonse. Kusiyana kwa moyo wa batri ndi 40-50x nthawi zina, osati kukokomeza.

Chachiwiri: mutha kugwiritsa ntchito magetsi otsika mtengo. Mukufuna kuyendetsa galimoto ya 48V pa liwiro losinthika? Ndi chiwongolero cha analogi mumafunika mtengo wosiyanasiyana wa 0-48V. Ndi PWM mumagwiritsa ntchito 48V yokhazikika (yotsika mtengo) ndi MOSFET (komanso yotsika mtengo). Zatheka.

Chifukwa chachitatu palibe amene amalankhula: kugula. Yesani kupeza ma analogi abwino osinthira kuchuluka kwake. Nthawi zotsogola ndizochepera masabata 26 kuchokera kwa opanga abwino. MOSFETs? Zonse zili m'gulu la Digikey. Pamene kupanga kukukuwa, izi ndizofunikira kuposa mtengo wa BOM.

PWM

EMI idzakuwonongani. Nthawi yoyamba yomwe ndinapanga -PWM board yapamwamba (120A ya DC motor), idapha basi ya CAN pagalimoto yomweyo. Mapaketi osavunda-akufa kotheratu. Ndinazindikira kuti kulira kwa chipata changa kunali kulumikiza pansi, ndikupangitsa ma 40V spikes pa CAN kusiyana. Mikanda yowonjezeredwa ya ferrite, malo osunthira mozungulira, akadali ndi zovuta. Pamapeto pake ndinafunika kuwonjezera sefa ya pi pamagetsi amagetsi ndi kulekanitsa ndege zapansi ndi njira imodzi-yolumikizira. Anatenga ma rev board atatu.

Kuyendetsa pachipata ndikovuta kuposa momwe kumawonekera. Mumafunika kutsekereza pang'ono kuchokera pa dalaivala wanu kupita kuchipata cha MOSFET-kufufuza zinthu pa high di/dt. Ndawonapo 10nH ya trace inductance imayambitsa ma 50V voltage spikes panthawi yosintha (V=L × di/dt). Ndikokwanira kumenya MOSFET 60V. Anthu amatsutsana za masamu koma ndaziwonapo: 3A / ns kusintha kwamakono kukhala 10nH kumakupatsani 30V spike. Onjezani magetsi operekera ndipo mwadutsa mulingo woyenera kwambiri.

Ndiye pali kuwombera{0}}kupyola mu H-milatho. MUYENERA kukhala ndi nthawi yofikira pakati pa kuzimitsa-mbali FET yotsika ndi kuyatsa -mbali yapamwamba (ndi mosemphanitsa). Zero deadtime imatanthauza kuti ma FET onse amayenda nthawi imodzi-kudumphira pang'onopang'ono kuchokera ku FET kupita pansi kudzera mu FET channel resistances. 50A mpaka 0.01Ω kawiri akadali 1000A kwa ma microseconds zinthu zisanaphulike. Njira yolephereka ndi yochititsa chidwi: crater yaying'ono mu silicon, FET imapita mwachidule, imatulutsa china chilichonse mu unyolo.

Koma nthawi yochuluka kwambiri komanso diode ya thupi imachita panthawi yakufa. Ma diode amthupi ndi oopsa-kutsika patsogolo (1-2V), kuchira mochedwa. Mumataya mphamvu ndikupanga kutentha kwambiri. Kusinthanitsa nthawi zambiri kumakhala nthawi ya 100-500ns kutengera momwe FET yanu imasinthira.

Chidziwitso choyamba cha aliyense: ma frequency apamwamba=ma inductors ang'onoang'ono/ma capacitor=otchipa. Nthawi zina zoona. Koma kutayika kwa kusintha kumachulukira pafupipafupi-umataya mphamvu nthawi iliyonse FET ikusintha. ESwitching ≈ 0.5 × Vsupply × Iload × (trise + tfall) × fsw. Pawiri pafupipafupi, kuwirikiza kawiri kutayika kosintha.

Pamagalimoto amagalimoto, 20kHz ndiyofala. Pamwamba pa zomveka, zokhazikika zamakina sizisamala. Koma mumagetsi a laputopu mumawona 300kHz-1MHz. Chifukwa chiyani? Maginito ang'onoang'ono. 1MHz inductor ndi thupi 1/50th kukula kwa 20kHz imodzi yokhala ndi inductance yomweyo. Ndicho chachikulu kwa zipangizo kunyamula. Kugulitsa kumafunikira ma FET othamanga (otsika Qg), masanjidwe abwinoko, kapangidwe kake koyendetsa bwino.

Audio (Class D amps) imayenda ndi 250kHz-1MHz. Pansi pa 200kHz ndipo mutha kumva ma frequency a wonyamula ngati kulira kwamphamvu-. Pamwamba pa 1MHz ndikuyamba kumenyana ndi kusokoneza wailesi ya AM. Mapangidwe ambiri amakhazikika pa 400-500kHz, fyuluta yotsika pang'ono mwina 50kHz kuchotsa chonyamulira.

Chitsanzo chenicheni: adatembenuza buck 500kHz kamodzi, adayesa kupita ku 1MHz kuti achepetse bolodi. Kuchita bwino kwatsika 4% (88% mpaka 84%). Ndiko kutentha kwa 8W mumtundu wa 200W. Pamafunika heatsink yayikulu, idataya malo onse osungidwa kuchokera ku inductors yaying'ono. Amakhala pa 500kHz.

PWM

8-bit PWM (masitepe 256) zimamveka bwino mpaka mutayesa kuzimitsa kuwala kwa LED kuchokera pa 100% kufika pa 0%. Pansi pa 10% yozungulira ntchito mumapeza masitepe owoneka bwino. Diso laumunthu ndi logarithmic-lokhudzidwa kwambiri ndi kusintha kwa kuwala kochepa. Mufunika 12-bit (masitepe 4096) osachepera kuti muchepetse kuwala konsekonse.

Koma nazi: 12-bit pa 20kHz zikutanthauza kuti mufunika 20kHz × 4096=81.92MHz timer wotchi. Si ma micros onse omwe angachite zimenezo. Ndipo ngati mukufuna njira zingapo zodziyimira pawokha za PWM pa 12-bit, mukuyang'ana zotumphukira zodzipatulira kapena FPGA.

Njira yogwirira ntchito: gwiritsani ntchito 8-bit PWM koma sinthani ma frequency mwachangu. Pakuwala kwambiri thamangani 20kHz, pakuwala kochepa kumatsika mpaka 100Hz. Zimakupatsirani masitepe abwinoko pomwe mukuwafuna. Koma tsopano muli ndi ma frequency-frequency EMI oti muthane nawo. Palibe chaulere.

Industrial VFDs (ma frequency frequency drives) amasintha mazana a ma amp pa 480VAC. Dongosolo lowongolera ndilovuta kwambiri-kusinthasintha kwa ma vekitala, magawo-wongoyang'anira, zilizonse-koma pansi pake PWM ikusinthabe ma IGBT asanu ndi limodzi mu -mlatho wa magawo atatu.

Kusiyana pamlingo uwu:

Oyendetsa zipata amafunikira zida za 15V zakutali. Ndizinthu 6 zokhazokha zomwe zikuyandama mosiyanasiyana mpaka 680VDC (yokonzedwa 480VAC). Dalaivala aliyense amafunikira mphamvu yakeyake, chopinga chake cha pachipata (0.5-2Ω chodziwika bwino), chitetezo chake chambiri.

Nthawi yakufa imakwera mpaka 2-5µs chifukwa ma IGBT amachedwa kuposa ma MOSFET

Zosefera za dv/dt zomwe zikutulutsa chifukwa kuchuluka kwa ma chingwe cha mota komanso kusinthasintha kofulumira kumapangitsa-mafunde ambiri. Ndayezera 20A za common-mode current pa 5HP motor cable, zosiyana kotheratu ndi motor current. Ndicho chifukwa chake mukufunikira zingwe zotetezedwa ndi malo oyenera.

Kutentha: ngakhale 2% kutaya pa 50kW ndi 1kW kutentha. Kuziziritsa kwamadzi ndi masiwichi oyenda ndi zolumikizira kutentha. Ngati madzi ozizira atsikira pansi, chowongolera chimalepheretsa zotuluka nthawi yomweyo. Makina owoneka akuyaka chifukwa wina wayiwala kuyang'ana mulingo wozizirira.

Kusankhidwa kwa zigawo kumakhala kodabwitsa. IGBT yovotera 100A mosalekeza imatha kugwira 80A pa 50 digiri yozungulira, 60A pa digirii 70. Koma kuyambitsa mota yayikulu imakoka 6x ovotera pano kwa masekondi angapo. Chifukwa chake mumakula kwambiri, osakhazikika,{9}}ndiyeno sinthani kutentha. Khalani ndi 300A IGBT pa ntchito ya "100A". Mtengo wa BOM umapangitsa kugula zinthu kukhala kosasangalatsa.

STM32 timer: ambiri ali ndi 16-bit PWM, mitundu ina imapita ku 32-bit koma simusowa. Chofunikira kwambiri ndi kuchuluka kwa ma tchanelo ofananitsa ndi zotulutsa zowonjezera. TIM1 ndi TIM8 pamndandanda wa F4 ali ndi njira zinayi zofananira iliyonse yokhala ndi zotulutsa zowonjezera komanso kuyika kwanthawi yofa. Zabwino kwambiri pakuwongolera magalimoto.

Vuto: mayendedwe onse a PWM pa timer imodzi amalumikizidwa ku kauntala yomweyo. Ngati mukufuna ma frequency odziyimira pawokha, mufunika zowerengera zosiyana. Ndipo pali zowerengera nthawi zambiri zomwe zili ndi zida zapamwamba. Pa STM32F4 mumapeza TIM1, TIM8 yowongolera mwapamwamba. TIM2-5 ya PWM yoyambira. TIM9-14 ndi 16-bit popanda m'badwo wakufa. Mumatha mwachangu ngati pulogalamuyo ikufuna ma sign a PWM angapo akutali.

Mwawona mapangidwe omwe amalepheretsa{{0}kung'anima kwa PWM mu mapulogalamu chifukwa adasowa matchanelo owerengera nthawi. Lingaliro loyipa. Jitter, CPU pamwamba, inversion patsogolo pamene ena amasokoneza moto. Ingolipirani $2 yowonjezera pa kachipangizo kakang'ono kokhala ndi nthawi zambiri kapena gwiritsani ntchito PWM IC yakunja (monga PCA9685). Tsogolo lanu lidzakuthokozani.

ESP32 ili ndi mayendedwe 16 a PWM pogwiritsa ntchito zotumphukira za LED PWM. Zikumveka bwino, kupatula zonse zimachokera ku wotchi imodzi ya 80MHz APB ndikugawana ogawa m'magulu. Mukufuna ma frequency osiyanasiyana? Ndikukhulupirira kuti ndi ma ratioti onse. Komanso kusinthaku kumachepa ngati ma frequency akuchulukira chifukwa ikugwiritsa ntchito wotchi yoyambira yomweyi. Pa 20kHz mumapeza 12-bit, pa 40kHz muli pansi mpaka 11-bit, ndi zina zotero.

Kufalitsa-sipekitiramu PWM: m'malo mokhazikika, mumasokoneza ±10% mwachisawawa. Imafalitsa EMI kudutsa ma frequency angapo, imachepetsa kutulutsa kwakukulu. Imathandizira kuyesa kwa FCC / CE popanda zida zosefera zambiri. Tchipisi zambiri zamakono za SMPS zili ndi izi. Cypress PSoC imakulolani kuti muwongolere mawonekedwe a dithering-sawtooth, triangular, pseudo{7}}mwachisawawa.

Interleaved PWM: thamangitsani otembenuza angapo kuchokera pagawo. Ma converter awiri pa 180℃phase shift amatanthauza kuti capacitor yolowera imawona theka lamphamvu yapano. Ma converters anayi pa 90 degrees phase shift-kota pa ripple. Koma tsopano mufunika kulumikizana kolondola kwa gawo pakati pa ma tchanelo ndi kusanja kwa katundu kuti agawane pano mofanana. Nthawi zambiri amafunikira IC yodzipatulira pokhapokha ngati yaying'ono yanu ili ndi zothandizira zokwanira.

Ma GaN FET amatha kusintha mkati mwa 10ns. Imatsegula ma frequency a 10MHz+ PWM-ma inductors amakhala ang'onoang'ono, pafupifupi ma PCB okha. Koma: mawonekedwe a board ndi ofunikira, kuyendetsa pachipata kumafunikira chidwi kwambiri, kuwongolera kulikonse kumayambitsa kuphulika kwakukulu. Osati kwa oyamba kumene. Munawona mphete yopangira GaN ku 2x VDD chifukwa wina adagwiritsa ntchito woyendetsa pachipata wokhala ndi 5cm kutalika kwake. FET sinapulumuke.

PWM

Pazinthu zambiri: 20kHz, hardware timer PWM, 10{{5}bit resolution. Zambiri zowongolera ma mota ndi dimming ya LED. Onjezani woyendetsa pachipata IC (2A pachimake chocheperako), zotchingira za ceramic zotsika za ESR pamtsinje wa FET, ndege yamafuta. Yang'anani masinthidwe osinthika ndi kuchuluka kwa mawonekedwe oyamba, yembekezerani kubwereza kamodzi.

Pachilichonse pamwamba pa 10A mosalekeza, kayeseleledwe kachabechabe musanayambe masanjidwe. Ndimagwiritsa ntchito ANSYS koma ngakhale FEA yoyambira imagwira mavuto ambiri. Tumizani kunja zigawo zamkuwa zotayika monga magwero a kutentha, ikani malire, fufuzani ngati chirichonse chikugunda 125 digiri pa mphambano kutentha pa max ambient. Nthawi zambiri amafunikira ma heatsinks kapena mpweya wokakamizidwa ngati mukusintha kuposa 50W.

Ndipo yesani kutentha. Kuyeza kutentha m'chipinda kumagwira mwina 60% yazovuta. Bokosi lotentha- lokhala ndi 70 digiri ambient kwa maola 8 limapeza zotsalazo-zothamanga kwambiri, gate threshold shift, capacitor ESR kuwonjezeka. Zinandiwonongera sabata kamodzi pomwe mapangidwe adagwira ntchito bwino pa digiri ya 25 koma FET idakhazikika pa digiri ya 65 chifukwa sindinawerengere kuchuluka kwa kutentha kwamagetsi.

Ndi PWM. Lingaliro losavuta, tsatanetsatane wopanda malire.

Chomaliza: ngati mukuchita -zinthu za PWM zoyendetsedwa ndi batri, musachepetse ma cell. Sanayesepo-kutchula ma lithium packs kamodzi-sinatha kugwira ntchito ndi ma ripple current, mphamvu yamagetsi yachepa, makina onse adazimitsidwa. Kusintha koyeneraionic lithiamu batirema module okhala ndi C-yabwinobwino, vuto latha. Zowonjezera $ 15 pa paketi zimandipulumutsa ku mafoni atatu othandizira pa sabata.