Abstract
With a multiphase converter, the phase-shedding function dedicated to maximizing the power efficiency, in a manner that is dependent on the load current, is always provided by a centralized controller that induces a Single Point of Failure (SPOF). The objective of this study is to obtain a decentralized control approach to implement this function by removing any SPOF. The method consists of using identical local controllers, each associated with a converter phase, that communicate with each other in a daisy-chain structure. Instead of measuring the global output current to determine the optimal number of active phases required, each local controller measures its own leg current and takes a local decision based on threshold crossing management and inter-controller communications. Functional simulations are carried out on a 5-leg 12 V/1.2 V 60 W multiphase converter supplying a modern microcontroller. They demonstrate that the number of active phases is well adjusted, in a dynamic manner, depending on the load current level. Specific events such as load current inrush or the start-up sequence are analyzed to guarantee optimal transient responses. A maximum power efficiency tracking ability is also demonstrated. Finally, it is shown that this control strategy allows phase shedding to be implemented using as many phases as desired, in a modular manner, thereby avoiding any centralized processing.
Highlights
The popularity of multiphase converters for high load applications such as microprocessor power supplies has brought forward the need to improve the efficiency of the converter across a wide range of load currents, from a high level in normal operating mode towards a very light level during standby/sleep mode, for instance
The most popular technique used to achieve good performance is the phase add/drop technique, known as phase shedding, which consists of adapting the number of active phases to always operate close to the maximum efficiency point of each phase for any load current
Further improvements towards an optimal implementation of phase shedding were achieved with digital time-optimal control in [3], average current compensation across phases during phase shedding for fast transient in [4], as well as binary-weighted current sharing for precise coverage of the load range in [5]
Summary
The popularity of multiphase converters for high load applications such as microprocessor power supplies has brought forward the need to improve the efficiency of the converter across a wide range of load currents, from a high level in normal operating mode towards a very light level during standby/sleep mode, for instance. The operating modes of microprocessors generating fast transients require the power supply to provide high current in a very short time without penalizing the voltage regulation In this context, the decentralized phase-shedding function must make it possible to manage particular operating modes for which all the phases must be simultaneously activated as quickly as possible. Each local controller monitors its own phase current, compares it with the minimum and maximum current thresholds, and locally decides to remain active or not depending on the state of its close neighbors This control strategy effectively optimizes the output efficiency across the full load range, as presented in [2], but in a decentralized manner. FFigiguurere22shshoowwssththeesesveverearal leleelmemeenntstsininvvoolvlveeddininththeelolocacal lcoconntrtorollleler.r.AAccuurrrerennt-tm-mooddee vvooltlataggeereregguulalatotor risisimimpplelemmeenntetedd. .AAn nererrorroropo-pa-mamp,p,acatcivtiavtaetdedonolnylyininththeeMMasatsetrerLLCC, , eqequualailziezsesththeeloloaaddvvooltlataggeeVVouotutwwitihthththeerreefeferreenncceessigignnaallVVrerfe.f.ItItggeenneeraratetsesththeessigignnaallVVDD, , wwhhicichhisisccoommppaarreeddtotoththeeoouutptpuuttssigignnaallVVIiIoi fotfhtheepphhasaesecucurrrernent tsesnensosorrtotopprorodduucceeththeeloloccaal l PPWWMMcoconntrtorol lsisgignnala.lT. hTehesigsinganlaslsφφiaannddφφi are generated, including a deadd--ttiimmee DDTT..AA stsatatete-m-maacchhininee, ,ddeeddiiccaatteeddttooiimmpplleementing the phhaassee--sshheeddddiinnggffuunnccttioionn, ,mmaannaaggeessththeestsattau-s tuosf tohfetLhCe ,LiC.e,.,ie.en.a, belneadbolerdnootr, dneopt,enddepinegndonintgheonpatrhaempeaterramvaeltueersvaanlduebsehanavdiobreohfaevxioterrnoaf l exsitgenrnaalsl.sTigonpaelrsf.oTromptehrefoarpmprtohperaiaptpercoopnrtiraotleocfoantmroulltoifpahamseulctoipnhvaesretecr,odnevceerntetra, ldizeecdenPtrWalMizseigdnPaWl inMtesrilgeanvailnigntaenrldeapvhiansgeacnudrrpenhtabsealcaunrcrienngtfbuanlcatniocinnsgafrueninctciloundseadreininthcelusdyesdteimn.tFhoer sythsteesma.kFeoorf tchlaersitaykeanodf ctloarfoitcyuasnodnltyo ofoncuthseopnhlyasoen-sthheedpdhinagsep-sahret,dtdhiensge pfuanrtc,ttihonesseafruennco-t tidoentsaialered ninothdeefitagiulerde.iAn ltlhineffoirgmuraet.ioAnllabinofuotrtmheaitrioinmpableomutenthtaetiironimcpanlebmeefnotuantidoninc[a1n5,b2e0] fofourntdheinin[1te5r]leaanvdin[2g0a]nfodrththeeciunrtreernletabvailnagncaindg,trheespcuecrtrievnetlyb.aAlalnl dcientgai,lrseasbpoeuctivtheelyo.pAelrladtieo-n taoiflsthabeosutattteh-emoapcehrianteioanreofptrhoevsidtaetde-imnaCchianpetearre2.pIrtosvhidoeudldinbCe hnaoptetdert2h.aIt stheoucoldlobrecnoodteedof thFaigt st.h1e acnodlor cisodreespoef cFtiegds.in oarndder2tios hreeslppeinctethdeinunodredresrtatondhienlgpoinf tthheecuonndtreorlsstaynstdeimng(tohfe thinetceor-nLtCrocl osymsmtemun(itchaetiionntsera-rLeCshcoomwnmiunnbicluatei;otnhseaortehsehrocwonnniencbtilounes; tahree oshthoewr ncoinnnreecdt)io. ns are shown in red)
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