E第1章 电力电子器件概述2.ppt

1、1,1.3 Half-controlled deviceThyristor,Another name: SCRsilicon controlled rectifier（晶体闸流管半控型器件，可控硅整流器） Thyristor opened the power electronics era 1956, invention, Bell Laboratories 1957, development of the 1st product, GE 1958, 1st commercialized product, GE Thyristor replaced vacuum devices in almo

2、st every powerprocessing area. Still in use in high power situation. Thyristor still has the highest power-handling capability.（能承受的电压和电流容量最高，工作可靠，在大容量的场合具有重要地位）,History,2,Appearance and symbol of thyristor,Stud and plate 3 terminals 螺栓型封装,通常螺栓是阳极,能与散热器紧密连接且安装方便 平板型晶闸管可由两片散热器将其夹在中间,3,Static静态 charac

3、teristics of thyristor,Blocking when reverse biased, no matter if there is gate current applied 当反向偏置为阻断状态，不管门极是否施加触发电流，也不开通 Conducting only when forward biased and there is triggering current applied to the gate. Once triggered on, will be latched on 仅仅1、当正向偏置，2、门极施加触发电流 管子导通 一旦导通之后 持续导通状态 Conducti

4、ng even when the gate current is no longer applied 导通之后 门极触发电流撤销仍旧导通 Turning off: decreasing current to be near zero with the effect of external power circuit 通过外电路 把流过晶闸管的电流减小 接近维持电流以下 晶闸管视为关断,Gate V-I characteristics,Holding Current,(晶闸管一旦导通，门极就失去控制作用),雪崩击穿,4,Static characteristics of thyristor,（1

5、）Forward Conducting When IG=0，if the anode voltage is made positive with respect to the cathode, only a small forward leakage current flows through the device, then SCR is said to be in the forward blocking, or off- state. 1 With the increasing of the amplitude of gate current，the forward break-over

6、 voltage decreases. 2 The voltage drop is small, typically, about 1V.,The thyristor will be turned on by increasing the forward voltage beyond Ubo 3,5,Static characteristics of thyristor,(2)Reverse blocking Similar to that of diode. In reverse blocking state, only very small reverse leakage current

7、flows the device. When the reverse voltage reaches the reverse breakdown voltage, the device will be in the thermal deterioration. 1,Conclusions： The conducting condition of SCR： UAK0 and UGK0 The condition from on-state to off-state of SCR：to make the forward anode current be below the holding curr

8、ent. (一般通过减小EA,直至EA0来实现。）,6,Structure and equivalent circuit of thyristor,Structure,Equivalent circuit: A pnp transistor and an npn transistor interconnected together(等效为两个晶体管V1和V2串级而成),7,Physics of thyristor operation,After Triggering, Regenerative effect or Positive feedback Can not be turned off

9、by control signal Half-controllable,Working process ： UGK0 generates IG V2 is turned on generates IC2 V1 is turned on IC1 IC2 Strong Positive feedback occurs，terminal G loses the function of control，V1and V2 are in complete saturation state ，then SCR is in on-state.,通过SCR的电流由R确定为EA/R。UAK之间的压降约为1V。此时

10、，将IG调整为0，即UGK0，也不能解除正反馈，G极失去控制作用。,8,Quantitative description of thyristor operation,Where 1 and 2 are the common-base current gain of V1 and V2, respectively；ICBO1 and ICBO2 are the common-base leakage current of V1 and V2, respectively。,阻断状态：此时流过晶闸管的漏电流稍大于两个晶体管漏电流之和。,开通状态： IA很大. 但IA实际上由于外电路负载的限制，会维

11、持有限值。,9,Other methods to trigger thyristor on,High voltage across anode and cathodeavalanche breakdown High rising rate of anode voltagte du/dt too high High junction temperature Light activation(光触发:当强光直接照射在硅片上，产生电子空穴对，在电场的作用，产生触发SCR的电流。) 光触发可以保证控制电路与主电路之间的良好绝缘而应用于高压电力设备中，称为光控晶闸管（LTT） 只有门极触发是最精确、迅速

12、而可靠的控制手段。,10,Switching characteristics of thyristor,Turn-on transient Delay time td(0.51.5s) Rise time tr(0.53s) Turn-on time tgt =td+ tr Turn-off transient Reverse recovery time trr:正向电流降为零到反向恢复电流衰减至接近于零的时间 Forward recovery time tgr:晶闸管要恢复其对正向电压的阻断能力还需要一段时间 Turn-off time tq =trr+tgr,11,Specificatio

13、ns of thyristor,Peak repetitive forward blocking voltage(断态重复峰值电压)UDRM 在门极断路而结温为额定值时，允许重复加在器件上的正向峰值电压。 Peak repetitive reverse blocking voltage(反向重复峰值电压)URRM 在门极断路而结温为额定值时，允许重复加在器件上的反向峰值电压。 Peak on-state voltage(通态（峰值）电压)UTM 晶闸管通以某一规定倍数的额定通态平均电流时的瞬态峰值电压。,Notice: Usually take minUDRM,URRM as the rate

14、d voltage of SCR。 选用时，一般取额定电压为正常工作时晶闸管所承受峰值电压23倍。,12,Specifications of thyristor,Average on-state current(通态平均电流) IT(AV) 在环境温度为40C和规定的冷却状态下，稳定结温不超过额定结温时所允许流过的最大工频正弦半波电流的平均值。标称其额定电流的参数。 使用时应按有效值相等的原则来选取晶闸管。 实际使用时应留一定的裕量，一般取1.52倍。 电流平均值(average value )： 指一个周期内的电流算数平均值； 电流有效值(effective value )： 指一个周期内的

15、电流的方均根值(root mean square )。 波形系数(form factor )： Kf = I / IT(AV),13,Specifications of thyristor,SCR产品参数给出的额定电流是平均值，应根据实际电路计算有效值来选定SCR。(SCR管芯的发热效应是与流过电流的有效值有关系的) 在实际选用SCR时，根据电流有效值相等原则。即： 实际波形的电流有效值I1SCR额定电流IT(AV)对应的电流有效值I 由于测量IT(AV) 的电路为正弦半波电路。此时额定有效值I与IT(AV)之间的关系为：I= IT(AV)*1.57 。 则I1 IT(AV)*1.57 ，因此

16、,选用SCR可以采用以下公式来确定额定电流： IT(AV)(M *I1)/1.57 其中， IT(AV)为选用SCR的额定电流（未知）；M为裕量系数(Margin Factor)，一般为1.52； I1为实际电路的电流有效值(已知)。,14,Example1-1The waveform of a rectifier circuit is in the following, the average current of it IT(AV) =20A，please choose SCR（M=1.5)。,i,积分公式,Key:,15,Specifications of thyristor,Holdi

17、ng current(维持电流) IH 使晶闸管维持导通所必需的最小电流。 Latching up current(擎住电流) IL 晶闸管刚从断态转入通态并移除触发信号后， 能维持导通所需的最小电流。对同一晶闸管来说，通常IL约为IH的24倍。 Peak forward surge current(浪涌电流)ITSM 指由于电路异常情况引起的并使结温超过额定结温的不重复性最大正向过载电流,16,Specifications of thyristor,du/dt(断态电压临界上升率) 指在额定结温和门极开路的情况下，不导致晶闸管从断态到通 态转换的外加电压最大上升率。电压上升率过大，使结电容充

18、电电流足够大，造成晶闸管误导通 。 di/dt(通态电流临界上升率) 指在规定条件下，晶闸管能承受而无有害影响的最大通态电流上升率。如果电流上升太快，可能造成局部过热而使晶闸管损坏。,17,The family of thyristors,Fast switching thyristorFST,包括所有专为快速应用而设计的晶闸管，有快速晶闸管和高频晶闸管。 开关时间以及du/dt和di/dt耐量都有明显改善。 普通晶闸管关断时间数百微秒，快速晶闸管数十微秒，高频晶闸管10s左右。 高频晶闸管的不足在于其电压和电流定额都不易做高。 由于工作频率较高，不能忽略其开关损耗的发热效应。,18,The

19、family of thyristors,Triode AC switch(双向晶闸管)TRIAC (Bi-directional triode thyristor),可认为是一对反并联联接的普通晶闸管的集成。 有两个主电极T1和T2，一个门极G。 在第和第III象限有对称的伏安特性。 通常用在交流电路中，不用平均值而用有效值来表示其额定电流值。 与一对反并联晶闸管相比是经济的，且控制电路简单，在交流调压电路、固态继电器（SSR）和交流电机调速等领域应用较多.,19,The family of thyristors,Light-triggered (activited) thyristor L

20、TT,Reverse-conducting thyristor(逆导晶闸管) RCT,将晶闸管反并联一个二极管制作在同一管芯上的功率集成器件。 具有正向压降小、关断时间短、高温特性好、额定结温高等优点。 常应用于各类逆变器和斩波器的应用中。,又称光触发晶闸管，是利用一定波长的光照信号触发导通的晶闸管。 光触发保证了主电路与控制电路之间的绝缘，且可避免电磁干扰的影响。 因此目前用在高压大功率的场合。如高压直流输电和高压核聚变装置中，占据重要的地位。,20,Homework,Requirements: Translate the following questions and then answe

21、r them。,1.使晶闸管导通的条件是什么？ 2.如图为调试晶闸管的电路，在断开Rd测量输出电压Ud是否正确可调式，发现电压表读数不正常，接上Rd后一切正常，为什么？ 3. 用万用表怎么区分晶闸管的阳极、阴极与门极？判断晶闸管好坏有哪些简便实用的方法？ 4.用万用表测量晶闸管门极时，为什么正反向电阻不同？是否阻值越小越好？,21,1.4 Typical fully-controlled devices,1.4.1 Gate- turn-off thyristor GTO 1.4.2 Giant transistor GTR 1.4.3 Power metal-oxide-semiconduc

22、tor field effect transistor Power MOSFET 1.4.4 Insulated-gate bipolar transistorIGBT,Features IC fabrication technology, fully-controllable, high frequency Applications Begin to be used in large amount in 1980s GTR is obsolete and GTO is also seldom used today. IGBT and power MOSFET are the two majo

23、r power semiconductor devices nowadays.,22,1.4.1 Gate-turn-off thyristorGTO,Major difference from conventional thyristor : GTO is kind of power integrated device with multiple-units，and it contains dozens of , even hundreds of small GTO units in common-anode，whose the cathodes and gates are parallel

24、 connected in GTO The gate and cathode structures are highly interdigitated(交叉排列),Structure,Symbol,各单元的阴极、门极间隔排列的图形,并联单元结构断面示意图(PNPN),23,Physics of GTO operation,The basic operation of GTO is the same as that of the conventional thyristor. The principal differences lie in the modifications in the st

25、ructure to achieve gate turn-off capability. Large 2(使晶体管V2控 制灵敏，易于GTO关断) 1+2 is just a little larger than the critical value 1(导通时饱和不深接近临界饱和，有利门极控制关断，但导通时管压降增大). Short distance from gate to cathode makes it possible to draw current out of gate(多元集成结构使GTO元阴极面积很小，门、阴极间距大为缩短,使得P2基区横向电阻很小，能从门极抽出较大电流).,

26、24,Physics of GTO operation,Turn-off process： A strong positive feedback exists in itif a large negative pulse current is applied in the gate, which will draw currents out of the gate, then Ib2 , which makes IK and Ic2，the decreasement of Ic2 makes IA and Ic1 ，which decreases the base current of V2

27、further；,when the decreasement of IA and IK makes 1+21，GTO exits saturation and then is turned off； multiple-units and integrated structures make GTO have a shorter turn-on time, and the ability of bearing di/dt is also stronger than SCR.,25,Characteristics of GTO,Static characteristic Identical to

28、conventional thyristor in the forward direction Rather low reverse breakdown voltage (20-30V) Switching characteristic,Turn-on transient：is the same as that of SCR Turn-off transient ：different from that of SCR Storage time ts，使等效晶体管退出饱和。 Fall time tf Tail time tt 残存载流子复合。,Usually tfts。 门极负脉冲电流幅值越大，

29、ts越短。,26,Specifications of GTO,Most GTO specifications have the same meanings as those of conventional thyristor. Specifications different from thyristors Maximum controllable anode current(最大可关断阳极电流)IATO GTO额定电流 Current turn-off gain(电流关断增益)off 最大可关断阳极电流与门极负脉冲电流最大值IGM之比称为电流关断增益。 off = IATO/ IGM off

30、一般很小，只有5左右，这是GTO的一个主要缺点。1000A的GTO关断时门极负脉冲电流峰值要200A 。 Turn-on time(开通时间)ton 延迟时间与上升时间之和。延迟时间一般约12s，上升时间则随通态阳极电流的增大而增大。 Turn-off time(关断时间)toff 一般指储存时间和下降时间之和，不包括尾部时间。下降时间一般小于2s。,27,1.4.2 Giant TransistorGTR,GTR is actually the Bipolar Junction Transistor that can handle high voltage and large current

31、. So GTR is also called power BJT (电力晶体管), or just BJT.,Basic structure,Symbol,NPN,See also Chapter 4 in P122 of textbook,28,Structures of GTR different from its information-processing counterpart,Multiple-emitter structure,Darlington configuration,The major features include high voltage, large curr

32、ent and good switching characteristics. Darlington-unit configuration to obtain a larger effective current gain beta.(单管GTR的 值比小功率的晶体管小得多，通常为10左右，采用达林顿接法可有效增大电流增益。目前更多地使用GTR模块) Adopt IC techniques to make these units being parallel connected The operation principles of Power GTR is the same as that

33、of conventional BJT,29,Static characteristics of GTR,Typical I-V characteristics in common emitter connection： cut-off region, amplifying region and saturation region.,In power electronics circuits, GTR works in switching states。,30,Switching characteristics of GTR,Turn-on transient Turn-on delay ti

34、me td Rise time tr Turn-on time ton Turn-off transient Storage time ts Falling time tf Turn-off time toff,31,Second breakdown of GTR,Primary breakdown：集电极电压升高至击穿电压时，Ic迅速增大,出现雪崩击穿。 只要Ic不超过限度，GTR一般不会损坏，工作特性也不变。 Second breakdown：一次击穿发生时，如不能有效的限制电流，Ic突然急剧上升，电压陡然下降。常常立即导致器件的永久损坏，或者工作特性明显衰变 。,32,Safe oper

35、ating area (SOA) of GTR,SOA 最高电压UceM、集电极最大电流IcM、最大耗散功率PcM、二次击穿临界线PsB限定。,33,1.4.3 Power metal-oxide-semiconductor field effect transistorPower MOSFET,A classification,Basic structure,Symbol,insulated gate,N Channel,oxide,34,Structures of power MOSFET,Power MOSFET: Depletion-type当栅极电压为零时漏源极之间就存在导电沟道。

36、Enhancement-type对于N（P）沟道器件，栅极电压大于（小于）零时才存在导电沟道。,Unipolar device: Only majority carriers participate the conducting conduction mechanism is the same as that of low power MOS， but power MOSFET differs vastly from MOS in the structures 采用多元集成结构，不同的生产厂家采用了不同设计。,35,Physics of MOSFET operation,P-N- juncti

37、on is reverse-biased(漏源极间加正电源，栅源极间电压为零,P基区与N漂移区之间形成的PN结反偏，漏源极之间无电流流过)。 off-state voltage appears across n- region,Off-state(截止),36,Physics of MOSFET operation,p-n- junction is slightly reverse biased positive gate voltage induces conducting channel(在栅源极间加正电压UGS,当UGS大于UT时，P型半导体反型成N型而成为Inversion layer

38、s(反型层)，该反型层形成N沟道而使PN结消失，漏极和源极导电 ) drain current flows through n- region and conducting channel,On-state(导电),on resistance = total resistances of n- region,37,Static characteristics of power MOSFET,I-V Characteristics of Drain（Output Characteristics ） Cut-off area（对应于GTR的截止区） Active area（对应于GTR的ampli

39、fication area） Ohmic area（对应GTR的saturation area） Works in switching states, i.e., it converts and reconverts between cut-off area and ohmic area。,On-resistance has a positive temperature coefficient，which is advantageous to current sharing in parallel connection of devices (Because if the current, t

40、hen temperature , at last on-resistance ，then the increasement of current is limited),38,The body diode of power MOSFET,The body diode,Equivalent circuit,漏源极之间有寄生二极管，漏源极间加反向电压时导通。可看为是逆导器件。在画电路图时，为了不遗忘，常常在MOSFET的电气符号两端反向并联一个二极管,39,Switching characteristics of power MOSFET,Turn-on transient Turn-on de

41、lay time td(on) Rise time tr,Turn-off transient Turn-off delay time td(off) Falling time tf,Test circuit b) Switching curves up脉冲信号源，Rs信号源内阻，RG栅极电阻， RL负载电阻，RF检测漏极电流,40,Switching characteristics of power MOSFET,Turn-on transient,开通延迟时间td(on) 从Up前沿时刻到UGS=UT并开始出现iD的时刻间的时间段 上升时间tr UGS从UT上升到MOSFET进入非饱和区的栅压UGSP的时间段,iD稳态值由漏极电源电压UE和 漏极负载电阻决定； UGSP的大小和iD的稳态值有关； UGS达到UGSP后，在Up作用下继续升高直至达到稳态，但iD已不变。 开通时间ton开通延迟时间td(on)与上升时间tr之和,41,Switching characteristics of power MOSFET,Turn-off transient,关断延迟时间td(off) 从Up下降到零起，栅源极输入电容Cin通过Rs和RG放电，到UGS按指数曲线下降到UGSP，iD开始减小止的时间段 下降时间tf UGS从UGSP继续下降起，iD减小，到uGSUT时沟道消失，iD下