AN920 D PDF

Publication Order Number: AN/D. AN/D GENERAL DESCRIPTION The MC series is a monolithic control circuit containing all the active functions. And Mc Pwm Controler – Download as PDF File .pdf), Text File .txt) or read online. AN/D for additional design information. The excel spread sheet for thermal considerations is available too. The MC is an extended temperature.

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Thusthecom-cycle,multiplecycles,ormultiplecyclesplusaportion paratorcaninitiateoutputswitchconduction,butcannot terminat i e tandthelatchisalwaysresetwhenCTbeginsofCounrerceyntclliem.

This butfinitetimeofoutputconductionfollowedbyeithera causesittorapidlyreachtheupperoscillatorthreshold,normalorextendedoff-timeintervalprovidedbythe therebyshorteningthetimeofoutputswitchconductionoscillatorramp-downtimeofCT. Operationof theswitchingregulator withaseverelyoverloadedorshortedoutputorhaving inanoverloadorshortedconditionwillcauseaveryshort theinputvoltagegrosslyabovethe nominaldesignvalue.

Inpracticethecurrentlimitcircuitwillsomewhatmod- ifythechargingslopeandpeakamplitudeofCTeach timethe outputswitchisrequiredtoconduct. Thisis becausethethresholdvoltageofthecurrentlimitsense circuitexhibitsasoftvoltageturn-oncharacteristicand hasaturn-offtimedelaythatcausessomeovershoot. Thisallowsthedesignetrheoptionofdrivingthe outputswitchtransistorintosaturationwithaselected forcedgainordrivingitnearsaturationwhenconnected asaDarlington. AseparateVCCpinisprovidedinordertoreduce theintegratedcircuitstandbycurrentandisusefulinlow powerapplicationsiftheoperationalamplifierisnot incorporatedintothemainswitchingsystem.

Thecatch diodeisconstructedfromalateralPNPtransistorandis capableofblockingupto40voltsandwillconductcur- rentsupto1. M4TOROLOABecausetheintegratedcircuitsubstrateiscommon withtheinternalandexternalcircuitryground,thecath- odeofthediodecannotbeoperatedmuchbelowground orforwardbiasingof thesubstratewillresult. Thistotally eliminatesthediodefrombeingusedinthebasicvoltage invertingconfigurationasinFigure15,sincethesub- strate,pin11,iscommontoground.

Thediodecan be consideredforuseonlyinlowpowerconverterappli- cationswherethetotalsystemcomponentcountmust beheldtoaminimum.

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qn920 Thesubstratecurrentwillbeabout 10percentofthecatchdiodecurrentinthestep-upcon- fvioglutraagtieo-innvaenrtdinagbinouwth2i0chppeirnce1n1tiisnctohmemstoenp-tdoothwennaengd- ativeoutput. Thefilteraveragetshesquarewavesproducing adcoutputvoltage thatcanbesettoanylevellessthan theinputbycontrollingthepercentconductiontimeof Qitothatofthetotalswitchingcycletime.

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TheoutputvoltageacrosscapacitorC0willeven- tuallydecaybelownominalbecause itistheonlycom- ponentsupplycurrentintotheexternalloadRL. The voltageacrosstheinductorisequaltoVin Vsat Vout andthepeakcurrentatanyinstantis: Therequiredvaluefor CTcanbedeterminedbyusingtheminimumoscillator chargingcurrentandthetypicalvaluefortheoscillator voltageswingbothtakenfromthedatasheetelectrical characteristicstable.

Theoff-timeis notrelated to theramp-downtimeofCT.

DC-DC Step-Up Converter | Details |

However,apoint ofdiminishingreturnwillbereachedbecausethecom- paratorrequiresafinitevoltagedifferenceacrossits inputstocontrolthelatch. AvalueforthecurrentlimitresistorRsccanbedeter- minedbyusingthecurrentlevelofIpk an92 whenVin. DonotsetRsc toexceedthemaximumlpk switch limitof1. Vin min O,peratio is n attheonset ofcontinuousmodeandtheoutputcurrent capabilitywillbegreaterthan50 mA.

ThenlL pk attainedduringtonmustdecaytozeroduringtoffanda ratiooftontot0ffcanbewritten. Ichg toffldischgton Figure10showsthestep-upswitchingregulatorwave- forms.

Referringtothe C02 capacitorcurrentwaveforms inFigure10, t1isdefined asthecapacitorcharginginterval. Solvingfortiinknown Substitutingfor 1 bk lout 1ok lout termsyields: Co2tpktoff 1ok lout 2toff 21pkC0.

DC-DC Step-Up Converter

Documents Education Rapports de stage. A78S40 are monolithic switching regulator subsystems intended for use as dc to dc con- verters.

These devices represent a significant advance- ment in the ease of implementing highly efficient and yet simple switching power supplies. The use of switching an90 is becoming more pronounced over that of linear regulators because the size reductions In new equipment designs require greater conversion efficiency.

Another major advantage of a9n20 switching regulator is that it has increased application flexibility of output volt- age. The output can be less than, greater than, or of opposite polarity to that of the input voltage.

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The linear regulator consists of a sta- ble reference, a high gain error amplifier, and a variable resistance series-pass element. The error amplifier mon- itors the outputvoltage level,compares it to the reference and generates a linearcontrol signal that varies between two extremes, saturation and cutoff.

This signal is used to vary the resistance of the series-pass element in a corrective fashion in order to maintain a constant output voltage under varying input voltage and output load conditions. Voir plus Voir moins. Documents Education Rapports de stage Switched-mode power supply Current. Article No jsco Available online at http: BasicSwitchingRegulatorConfigurations 9N02Theoff-timetoff,isthetimethatdiodeDlisinconduction anditisdeterminedbythetimerequiredfortheinductor currenttoreturntozero.