Dɛn ne PWM?- Polinovel .

PWM gyina hɔ ma pulse trɛw modulation. Woredan voltage wɔ na woredum wɔ frequency a wɔahyɛ da ayɛ so, woresakra ratio a ɛwɔ ON{1}}bere ne Off-bere a wode bedi tumi a wɔde ma no so. Ɛno ara ne no. Nea aka no yɛ nea ebefi mu aba no ho dwuma ara kwa.

Fa 12V supply a ɛma LED a ehia 3V. Mpɛn pii no na wode resistor anaa linear regulator bedi dwuma, hyew 9V sɛ ɔhyew. Nkwaseasɛm a wɔsɛe no. PWM wo dane 12V no nyinaa ON na dum no ntɛmntɛm araa ma LED thermal mass averages no fi. 25% duty cycle no ma wo bɛyɛ 3V equivalent. LED no hu 12V → 0V → 12V → 0V wɔ ebia 1kHz, nanso entumi nnwo na ɛhyew saa ntɛmntɛm no, enti hann kɔ so yɛ nea ɛkɔ so daa.

Frequency ho hia. Ɛyɛ brɛoo dodo (ɛwɔ 100Hz ase) na wunya flicker a wotumi hu. Nnipa binom hu flicker a ɛkɔ 200Hz. Me taa tu mmirika LED dimming wɔ 20kHz kɛkɛ sɛnea ɛbɛyɛ a ahobammɔ-san nso ma ɛnyɛ nea wɔte no sɛ mfiridwuma mu nkitahodi bi wɔ hɔ a. Switching speed nso ka losses, nanso yɛbɛkɔ saa.

Nkontaabu no: Sɛ wo bere yɛ t na ɛwɔ-bere no yɛ t, asɛyɛde kyinhyia d=t/t. Tiawa. Tumi a wɔde ma no bɛyɛ D × V_Supply × I_Load, a wɔahwere. Saa adehwere no ne baabi a nneɛma yɛ anigye.

Nea edi kan nti: Efficiency. MOSFET wɔ saturation mu no so tew ebia 0.1-0.2V wɔ currents a ntease wom mu. MOSFET OFF twetwe microamps. Enti wore dissipating (0.1V × current) anaasɛ titiriw no hwee. Fa toto ho ma linear regulator a ɛtɔ 9V wɔ full current so kɔ so. Battery nkwa nsonsonoe yɛ 40-50x wɔ tebea horow bi mu, ɛnyɛ nea ɛboro so.

Nea ɛto so abien: wubetumi de anyinam ahoɔden a ne bo yɛ mmerɛw adi dwuma. Ɛsɛ sɛ woka 48V motor wɔ ahoɔhare a ɛsakra mu? Na analog control wo hia variable a ne bo yɛ den 0-48V supply. Sɛ wode PWM di dwuma a, wode 48V a ɛyɛ pintinn (cheap) ne MOSFET (a ne bo yɛ mmerɛw nso) di dwuma. Mawie.

Nea ɛto so abiɛsa nti a obiara nka ho asɛm: adetɔ. Bɔ mmɔden sɛ wubenya variable analog supply pa bi wɔ volume mu. Lead times yɛ adapɛn 26 a ɛba fam koraa fi wɔn a wɔyɛ nneɛma a ɛfata hɔ. MOSFETS? Biribiara wɔ stock mu wɔ Digikey. Sɛ production reteɛteɛm gu wo so a, eyi ho hia sen BOM ka no.

PWM

EMI bɛbɔ wo. Bere a edi kan a meyɛɛ-mprempren PWM board (120A ma DC motor) no, ekum can bɔs no wɔ kar koro no ara so. Ɛnyɛ packets a asɛe-awu koraa. Ɛbɛdaa adi sɛ na me gate drive ringing no refa chassis asase no so, na ɛde 40V spikes aba can differential pair no so. Ferrite beads a wɔde kaa ho, a wɔde wɔn ho hyɛɛ mu no, na ɛda so ara wɔ nsɛmnsɛm. Awiei koraa no na ɛsɛ sɛ wode pi filter ka motor supply no ho na wode-point nkitahodi no tetew fam plane ahorow no mu. Ɔgyee board revs mmiɛnsa.

Gate drive yɛ den sen sɛnea ɛte. Wo hia impedance a ɛba fam fi wo draiver no so kɔ MOSFET gate-trace inductance ho nsɛm wɔ DI/DT a ɛkorɔn. Mehunuu sɛ 10nh a ɛwɔ trace inductance mu no de 50V voltage spikes ba bere a woresakra (V= L × DI/DT). Ɛno ara dɔɔso sɛ ɛbɛbɔ 60V rated MOSFET. Nkurɔfo gye akyinnye wɔ akontaabu no ho nanso mahu no wɔ scope no so: 3A/NS switching current into 10NH ma wo 30V spike. Fa supply voltage no ka ho na woaboro absolute maximum rating no so.

Afei shoot-ɛnam H-bridges so wɔ hɔ. Ɛsɛ sɛ wowɔ deadtime ntam dum a ɛba fam-fã FET na wodan kɔ soro-fã (ne nea ɛne no bɔ abira). Zero deadtime kyerɛ sɛ FETs abien no nyinaa yɛ adwuma bere koro mu-Tirect short fi supply to ground through the FET channel resistances. 50a through 0.01Ω mprenu da so ara yɛ 1000A ma microseconds ansa na nneɛma apae. Failure mode no yɛ nwonwa: Crater ketewa bi a ɛwɔ silicon no mu, FET kɔ tiawa koraa, yi biribiara a aka wɔ nkɔnsɔnkɔnsɔn no mu.

Nanso bere a awu dodo na nipadua diode no di akɔneaba wɔ bere a awu no mu. Nipadua diode yɛ hu-akɔ anim a ɛkɔ soro (1-2V), sanba a ɛyɛ brɛoo. Wohwere adwumayɛ yiye na ɛma ɔhyew pii ba. Trade-off taa yɛ 100-500ns awu a egyina wo FET no switching su so.

Obiara ne awosu a edi kan: frequency a ɛkorɔn= inductors nketewa/capacitors=a ne bo yɛ mmerɛw. Ɛtɔ mmere bi a, ɛyɛ nokware. Nanso switching losses kɔ soro bere a frequency-worehwere ahoɔden bere biara a FET no bɛsakra no. Eswitching ≈ 0.5 × vSupply × iload × (nsɛm a ɛyɛ dɛ + tfall) × FSW. frequency no mmɔho abien, bɔ switching loss no mmɔho abien.

Wɔ motor drives ho no, 20KHz abu so. Wɔ soro a wɔte, mfiri bere constants mfa ho. Nanso wɔ laptop tumi mu no wuhu 300kHz-1MHz. Adɛn? magnetics nketewa. 1MHz inductor yɛ honam fam 1/50th a ne kɛse yɛ 20kHz biako a ɛwɔ inductance koro no ara. Ɛno yɛ kɛse ma mfiri a wotumi fa so. Trade-off yɛ wo hia FETs a ɛyɛ ntɛm (lower QG), layout a eye, ahwɛyiye kɛse draiver design.

Audio (adesuakuw D amps) no tu mmirika 250kHz-1MHz. Ase hɔ 200kHz na wobɛtumi ate carrier frequency sɛ a ɛkorɔn-pitched whine. Wɔ soro 1mhz na wo hyɛ aseɛ ko ne AM radio interference. Nsusuiɛ dodoɔ no ara si wɔ 400-500kHz, low-pass filter wɔ ebia 50kHz de yi carrier no.

Nhwɛsoɔ ankasa: yɛɛ 500KHz buck converter pɛnkoro, bɔɔ mmɔden sɛ ɛbɛkɔ 1MHz akɔ shrink board no so. Efficiency so tewee 4% (88% kɔɔ 84%). Ɛno yɛ 8W extra heat wɔ 200W supply mu. Na ehia heatsink kɛse, hweree ahunmu sikakorabea nyinaa fii inductor ketewa no mu. Ɔtenaa hɔ wɔ 500kHz.

PWM

8-bit PWM (256 anammɔn) nnyigyei yɛ papa kosi sɛ wobɛbɔ mmɔden sɛ wobɛma LED an so ayɛ mmerɛw afi 100% kosi 0%. Ase hɔ 10% duty cycle wo nya anammɔn a wotumi hu wɔ hyerɛn mu. Onipa aniwa yɛ logarithmic-ɛyɛ mmerɛw kɛse wɔ nsakrae a ɛba wɔ hann a ɛba fam no ho. Hia 12-bit (4096 anammɔn) a ɛsua koraa ma dimming a ɛyɛ mmerɛw wɔ ne nyinaa mu.

Nanso ɛha na catch no wɔ: 12-bit wɔ 20kHz kyerɛ sɛ wuhia 20kHz × 4096=81.92MHz timer dɔn. Ɛnyɛ micros nyinaa na ebetumi ayɛ saa. Na sɛ wo hia PWM akwan pii a ɛde ne ho wɔ 12-bit a, worehwɛ dedicated timer peripherals anaa FPGA.

Workaround: Fa 8-bit PWM di dwuma nanso sesa frequency no dynamically. Wɔ hyerɛnn a ɛkorɔn run 20kHz, wɔ low brightness drop to 100Hz. Ɛma wo anammɔn a ɛyɛ fɛ wɔ baabi a wuhia. Nanso seesei wowɔ variable-frequency EMI a ɛsɛ sɛ wodi ho dwuma. Biribiara nni hɔ a ɛyɛ ahofadi.

Industrial VFDs (variable frequency drives) sesa amps ɔhaha pii wɔ 480VAC. Control strategy no yɛ complex-Space vector modulation, field-oriented control, nea ɛte biara-nanso ɛda so ara wɔ PWM ase a ɛresakra IGBT asia wɔ abiɛsa-fase bridge mu.

Nsonsonoe a ɛwɔ saa nsenia yi mu:

Gate karkafo hia 15V a wɔatew wɔn ho. Ɛno yɛ nneɛma 6 a atew ne ho a ɛrehuruhuruw wɔ tumi ahorow a ɛkɔ soro kodu 680VDC (rectified 480VAC). Ofirikafo biara hia n’ankasa tumi, n’ankasa gate resistor (0.5-2Ω typical), n’ankasa ahobammɔ a ɛboro so.

Deadtime kɔ soro kodu 2-5μs efisɛ IGBT ahorow no yɛ brɛoo sen MOSFET .

DV/DT filters wɔ output no so efisɛ motor cable capacitance plus fast switching edges no de common kɛse-mode currents ba. Mesusuu 20A a ɛyɛ common-mode current wɔ 5hp motor cable so, a ɛyɛ soronko koraa wɔ motor current no ho. Ɛno nti na wuhia shielded cables ne grounding a ɛfata no.

Thermal: mpo 2% a ɛyera wɔ 50kW yɛ 1kW ɔhyew. Nsu a ɛyɛ nwini a nsu a ɛsen ne ɔhyew a ɛwɔ mu no yɛ adwuma. Sɛ coolant flow kɔ fam sen threshold a, controller no ma outputs no yɛ adwuma ntɛm ara. Seen systems hyew efisɛ obi werɛ fii sɛ ɔbɛhwɛ sɛnea coolant no te.

Component selection nya weird. IGBT a wɔakyerɛ sɛ ɛyɛ 100A a ɛkɔ so no betumi adi 80A ho dwuma wɔ 50℃ambient, 60A wɔ 70℃. Nanso motor kɛse bi a wubefi ase no twetwe 6x rated current wɔ sikan pii mu. Enti wo size ma peak, ɛnyɛ steady-tebea, afei derate ma temperature. Fa 300A IGBT ma "100A" application no ba awiei. Bom ka no ma adetɔ no yɛ anigye kɛse.

STM32 timers: dodow no ara wɔ 16-bit PWM, ebinom models kɔ 32-bit nanso wo ntaa nhia. Nea ɛho hia kɛse ne dodow a wɔde toto akwan ne nneɛma a wɔde yɛ adwuma bom. Tim1 ne Tim8 a ɛwɔ F4 series no so no wɔ akwan anan a wɔde toto ho a emu biara ne nsɛm a ɛka ho a ɛka ho ne deadtime a wɔde hyɛ mu a wotumi yɛ ho nhyehyɛe. Ɛyɛ pɛpɛɛpɛ ma motor control.

Ɔhaw: PWM akwan a ɛwɔ timer biako so no nyinaa yɛ synchronized wɔ counter koro no ara so. Sɛ wuhia frequencies a ɛde ne ho a, wuhia timer ahorow a ɛsono emu biara. Na timers pii wɔ hɔ a ɛwɔ advanced features nkutoo. Wɔ STM32F4 no so no wunya TIM1, Tim8 ma advanced control. Tim2-5 ma mfitiase PWM. Tim9-14 yɛ 16-bit a enni awufo awo ntoatoaso. Wo run out fast sɛ application no hia PWM signals pii a atew ne ho a.

Seen seen designs where they bit-Bang PWM in Software efisɛ timer channels no sae. Adwene a ɛyɛ hu. Jitter, CPU overhead, priority inversion bere a ogya afoforo twa ogya mu. Kɛkɛ a, tua $2 a ɛka ho no ma micro a ɛwɔ timer pii anaasɛ fa abɔnten PWM IC (te sɛ PCA9685) di dwuma. Wo daakye ho asɛm no bɛda wo ase.

ESP32 wɔ PWM akwan 16 a wɔde LED PWM peripheral di dwuma. Ɛte sɛ nea ɛyɛ kɛse, gye sɛ ne nyinaa fi 80MHz APB dɔn biako mu na wɔkyɛ divisors wɔ akuw mu. Wopɛ frequencies ahorow? Anidaso sɛ wɔyɛ integer ratios. Afei nso resolution no so tew bere a frequency kɔ soro efisɛ ɛde base clock koro no ara na ɛreyɛ adwuma. Wɔ 20kHz wo nya 12-bit, wɔ 40kHz wo down to 11-bit, etc. Datasheet mma eyi nna adi.

Trɛw-SPECTRUM PWM: Sɛ́ anka wobɛhyehyɛ frequency a wɔahyɛ da ayɛ no, wo dither no ±10% randomly. Trɛw EMI no mu wɔ frequency range a ɛtrɛw so, ɛtew peak emissions so. Ɛboa ma wɔfa FCC/CE sɔhwɛ a enni filtering hardware pii. Nnɛyi SMPs chips dodow no ara wɔ eyi mu.Cypress PSOC mpo ma wutumi di dithering pattern-sawtooth, triangular, pseudo-Random so.

Interleaved PWM: tu mmirika pii converters fi phase. Converters mmienu wɔ 180℃phase shift kyerɛ sɛ input capacitor no hu ripple current no fã. Nsakraeɛ anan a ɛwɔ 90℃phase shift-afã no yɛ ripple no ho fã. Nanso seesei wo hia pɛpɛɛpɛ phase synchronization ntam channels ne load balancing enti wɔkyɛ current pɛpɛɛpɛ. Mpɛn pii no ehia sɛ wode controller IC a wɔatu ho ama gye sɛ wo micro no wɔ nneɛma a ɛdɔɔso.

Gan FETs tumi dannan ne ho wɔ 10ns ase. Bue 10MHz + PWM frequencies-Inductors bɛyɛ nketenkete, ɛkame ayɛ sɛ PCB traces kɛkɛ. Nanso: Board nhyehyɛe ho hia, gate drive hia sɛ wɔde wɔn adwene si so anibere so, inductance biara de overshoot kɛse ba. Ɛnyɛ wɔn a wɔrefi ase no de. Seen a gan design ring to 2x VDD ɛfiri sɛ obi de standard gate draiver a ne tenten yɛ 5cm dii dwuma. FET no antumi antra ase.

PWM

Wɔ nneɛma dodow no ara ho: 20KHz, hardware timer PWM, 10-bit resolution. Plenty ma motor control na LED dimming. Fa gate driver IC (2A peak current minimum), low-ESR ceramic caps ka ho wɔ FET drain no so pɛɛ, fat ground plane. Hwɛ switching waveforms no a scope wɔ prototype a edi kan no so, hwɛ kwan sɛ wobɛ iterate pɛnkoro.

Wɔ biribiara a ɛboro 10A continuous, thermal simulation ansa na layout. Me de ANSYS di dwuma nanso mpo basic FEA kyere ɔhaw dodow no ara. Export kɔbere layers ne losses sɛ ɔhyew fibea, set boundary tebea, hwɛ sɛ biribiara hits 125℃junction temp wɔ max ambient. Mpɛn pii no, hia heatsinks anaa mframa a wɔhyɛ sɛ woresakra bɛboro 50W.

na wɔasɔ ahwɛ wɔ ɔhyew mu. Room temp testing kyere ebia nsɛm 60%. Hot-adaka a ɛwɔ 70℃ambient mu nnɔnhwerew 8 no hu nea aka no-Thermal runaway, gate threshold shift, capacitor ESR kɔ soro. Cost me dapɛn biara bere a design bi yɛɛ adwuma yiye wɔ 25℃nanso FET latched up wɔ 65℃efisɛ manbu akontaa wɔ threshold voltage temperature coefficient ho.

Ɛno ne PWM. Adwene a ɛnyɛ den, nsɛm a enni awiei.

Adeɛ a ɛtwa toɔ: sɛ woreyɛ battery-Powered PWM nneɛma a, nnyɛ cheap out wɔ cells so. Wɔasɔ no bi-din lithium packs no din pɛnkoro-antumi anni ripple current no ho dwuma, voltage sagged wɔ load ase, nhyehyɛe mũ no nyinaa ayɛ bruu. Wɔdan kɔɔ nea ɛfata so .ionic lithium batere .Module ahorow a ɛwɔ C-rating, ɔhaw no yerae. $15 a ɛka ho a wɔde ma wɔ pack biara mu no gyee me fii mmoa a wɔfrɛ no abiɛsa mu dapɛn biara.