王串联型开关线性复合结构包络线跟踪电源中多电平变换器优化设计

(航空航天大学，江苏OptimizedDesignoftheMultilevelConverterinSeries-formSwitch-LinearHybridEnvelope-TrackingPowerSupply(NanjingUniversityofAeronautics&Astronautics,Nanjing :Inmodernradiocommunications,theenvelopeofradiofrequency(RF)signalfeatureswithlargepeaktoaveragepowerratio(PAPR).Thisnecessitatestheadoptionoflinearpoweramplifiers(PAs).InordertoachieveahighefficiencyforlinearPAs,envelopetracking(ET)techniqueisemployed,whichprovidesPAswithasupplyvoltagethattrackstheenvelopeofthetransmittedRFsignalinsteadofaconstantvoltage.Thispaperfocusesontheseries-formswitch-linearhybridETpowersupply,wheretheswitching-modeconverterusesamultilevelconverter.Themethodtoselectthesettingvoltagesunderthepremiseofvaluesandnumberofthevoltagelevelsofthemultilevelconverterareoptimizedusingapreciselossmodelbasedontheprobabilitydensityfunction(PDF)oftheenvelopesignal.Besides,thepulse-blankmethodisproposedtoimprovethesystemefficiencyfurther.Finally,aprototypeisbuiltaimingfortrackingtheenvelopesignalofwidebandcodedivisionmultipleaccess(WCDMA),with5MHzbandwidth,12V~27Voutputvoltage,4Waverageand10Wpeakoutputpower.TheexperimentalresultsshowthattheoutputvoltageoftheETpowersupplytracksthereferenceaccurayandthesystemefficiencycanreach76%.:Envelopetracking,lossmodel,multilevelconverter,optimizeddesign,poweramplifier：放大。包络线(EnvelopeTracking,ET)技术给线性功放提结构包络线电源，介绍了其工作原理并给出了各电平之间切换点电平的。为优化多电平变换器中电平值及

法进一步提高系统的效率。最后，本文以一台5MHz带10W的原理样机进行实验验证。实验结果验证了所提方案的有效性，电源整体效率为76%。：包络线损耗模型多电平变换器优化设计功相移键控(QuadraturePhaseShiftKeying,QPSK)及(QuadratureAmplitudeModulation,QAM)等复杂的调制方式[1]，此类调制方式会造成射频(RadioFrequency,RF)输入信号的包络线幅值不(PeakToAveragePowerRatio,PAPR)RF信AAB类等线性功放(LinearPowerAmplifier,LPA)。然而，LPA在恒压供LPA效率，一种较为有效的方法是RFLPA供电，如图1所示。包络 供包络 供t图1包络 2ET此技术即为包络线(Envelopetracking,ET)技术[2−3]2ET技术的原理框图，其中检的输出给LPA供电。ET电源可以大致分为以下三类：单开关变换器结构[4]，多开关变换器结构[5−7，开关线性复合点，已成为主流结构。SLHET电源可分为串联和并SLHETRLdET电V1V2Vn；电平vsw去初步拟合输出电A类放大状态，采样网络的输出与信为了保证Qlin工作性放大状态(对应三级管的线MOS管的饱和区)，vswvo；又因为线从损耗的角度，vswvo。本文在保

相同。但是此方法忽略了RF输入信号包络线的分布平数越多，vsw拟合输出电压的程度越好，即线性放如前所述，vswRF输入信号包络线的点电平值相接近，vsw将会产生短电压脉冲。本文提本文针对串联型HTF来指导多电平变换器中电平值和电平数的选取。另5z1~2V40WT串联型SLHET+_ vo

<

<…<

=

3SLHET =2,3,…,n)为选通管，Dk为阻断二极管。为了避 D1BuckBuckn-BuckD1BuckBuckn-Buck__

4

+_+__+_

MOSvDS_b，以虚线形式表示。在分界线上有VGD等于MOS管开启电压VGS(th)，因此vDS_b可表示为：vDS_bvGSvGDvGS 两个不同的电压源并联，D2至Dn-1分别和SW2

i GS DOvoiDVset2~Vsetn(Vset2<Vset3<…<Vsetn)进行比较，其iD

vDS_b D3D3D2 2 Comp33n

………………

vsminvsmax。为了保证在5 whenv when vwhen vvsw

(2kn whenv

A3，v

6N沟道MOSFETR (v ovv QRloss_lin

Vsetkk2,3,n)，根据上述分析，VsetkVsetkVk-1v

iiD

VsetkvoVset(k+1)(2kn)Vk向负Vsetk(k2,3n)

)floor(Vsetkvo_min)

vo

7vsw和vo之间不同压差时vsw多电平变换器中电平值和电平数

vo(j)vo_min(j1)

结合式(7)~(9)Vkk2,3,n)向负载提

vo(i)V(v whenk

Rij RPjVv

(v when2k

R

ij(V j(v)v V(v whenk 络信号的概率密度分布函数(ProbabilityDensity

ij(Vsetk Function,PDF)，其用于表征随机信号落在某段区 V2 区间长度定义为vPDF可通过下

变换器工作于电流连续模式(continuousConduction(vM(vx N DV iVinVkD 8WCDMAPDF，其中

LkL感电流有效值irms_Lk分别为：

irms_Qk

1T1Tk0.5i kts kLk2k

vo rms_Qk

1

j(v

ontoff

ij(vo_min

Ploss_lin(vo(i))(vo

因此，系统总损耗Ploss_total

VVk(1D Vkk1,2n)和包络信号PDF F V2 V

irms_LkkRack

RRR

eqk

初始化V1vo_minV2V1+Vn1V1+(n2),Vn=Vin。R

d

4)更新Vn1Vn1，若Vn1Vin d24

4d

步骤3，否则更新Vn2Vn2,Vn1Vn22频率处的深度。

至V1Vinn1)5)在迭代结果中查找系统损耗Ploss_total最小时k

V1=vo_min,V2=V1+λ,YNVn−2=Vn−2+λ,NYYLOOPNPcon_lsPdri_lsPsw_ls，以及二极管的导通损耗PD_ls，分别计算如下：j(v)v(i) (v con

ij(Vset2)

RLd

dri_lsg_lsk 1n )Vsetk(VV) k-1 k j(V)Vvo(i)(v F ij(v 为选通管的导通电阻；Qg_ls为总的门级电荷；Vdri_ls为驱动电压；ton_lstoff_ls分别为开通和关断时间。

结合式(2)和式(7)，线性放大器的平均损耗 图9选取最优电平值的迭代流程表1 221,20,20.5,318,24,17.5,21,18.5,22.5,416.5,25.5,17,19.5,18.5,26.5,515.6,22.8,26.4,16,18,20,18.5,21,27,615,18,24,27,15.5,17,20.5,23.5,18.5,21,27,28,趋势。但是系统的复杂度随着电平数的增加而增加。值有很大概率较低。相应的串联型SLHET电源的技

10vsw输入电压：Vin30输出电压范围：12V~27包络信号带宽：5表1给出了在不平选择方法下，线性放大器

V Vinvo_min (k1,2,..., 以线性放大器效率最优方法[9]选取电平值可通过最

11(b)所示，且输出电压降低的对于实际信号，通常采用标幺化的方差(normalizedmeansquareerror,NMSE)[7]VV电平数n=4较为合适。

(b)上切脉冲消除后图11上切脉冲消除前后主要波形的对比图在容许的范围之内。NMSE的计算如下：(e

NMSE

(v

oi1

NMSE来衡

21%~2%e(i)e(i)

0f0.032 v 极大值点处。vchop可通过下式计算：vchopvo_m m

ff0m2NMSE m2

13m为在输出电压畸变区域中总的输出电压采样

表2V2chopV2

通过消除阶梯波中存在的下切短电压脉冲可以2b

2342345

t

t

SMU200A矢量信号发生器产生。3切换点电平选取之前(Vsetk=Vk-1vsmax,k=2, (b)下切脉冲消除 图12下切脉冲消除前后主要波形的对比Ploss_multi代表C2:vsw[10C1:vref[1C3:vo[10Time:[214SLHET电源原理样机

C1:vref[1C2:C1:vref[1C2:vsw[10C3:vo[10Time:[2C2:v[10C1:C2:v[10C1:vref[1C3:vo[10 Time:[2

17(a)

7别为优化选取切换点电平前后的效率对比。由图可6。Ploss_linearPloss_multiPloss_totalPloss_linearPloss_multiPloss_total23454平416.5,21,25.5,417,19.5,23,419,22.5,26,点电平根据负载大小动态的调整可取得更高的系统效率；基于RF为zARaabFH,AsbeckP,CrippsS,KeningtonPB,PopovicZB,PothecaryN,SevicJF,SokalNO.PoweramplifiersandtransmittersforRFandmicrowave[J].IEEETransactionsonMicrowaveTheoryTechniques,2002,50(3):814826.BondadeR,ZhangY,MaD.Alinear-assisteddc-dchybridpowerconverterforenvelopetrackingRFpoweramplifiers[C].Proc.IEEEECCE,2014:5769-5773.ChinH,AndingZ,YanJJ,DraxlerP,KimballDF,LanfrancoS,AsbeckPM.Digitallyassisteddual-switchhigh-efficiencyenvelopeamplifierforenvelope-trackingbase-stationpoweramplifiers[J].IEEETransactionsonMicrowaveTheoryTechniques,2011,59(11):29432952.HaningtonG,ChenP,AsbeckPM.High-efficiencypoweramplifierusingdynamicpower-supplyvoltageforCDMAapplications[J].IEEETransactionsonMicrowaveTheoryTechniques,1999,48(8):14711476.WuPY,MokPKT.Atwo-phaseswitchinghybridsupplymodulatorforRFpoweramplifierswith9%efficiencyimprovement[J].IEEEJournalofSolid-StateCircuits,2010,45(12):25432556.RodriguezM,Fernandez-MiajaP,RodriguezA,SebastianJ.Amultiple-inputdigitallycontrolledbuckconverterforenvelopetrackingapplicationsinradiofrequencypoweramplifiers[J].IEEETransactionsonPowerElectronics,2010,25(2):369-381.MiajaPF,RodriguezA,SebastianJ.Buckderivedconvertersbasedongalliumnitridedevicesforenvelopetrackingapplications[J].IEEETransactionsonPowerElectronics,2015,30(4):2084–2095.KimballDF,JinhoJ,ChinH,DraxlerP,LanfrancoS,NagyW,LinthicumK,LarsonLE,AsbeckPM.High-efficiency

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