power electronics_CH2-power devices2.pptVIP

Power Electronics Devices Shanghai JiaoTong University E.E Department Wang Yong Contact: wangziqian2006@ Copyright partly from John Wiley Sons,Inc and from PEREC The concept of power electronic devices The electronic devices that can be directly used in the power processing circuits to convert or control electric power Features of power electronic devices The electric power that power electronic device deals with is usually much larger that the information electronic devices does. Usually working in switching states to reduce power losses. Need to be controlled by the information circuits. Drive circuits are always necessary to interface the information circuit and the power devices Special package and heat sink are necessary to dissipate the power loss  Uncontrolled device — power diode   Semi-controlled device – thyristor Typical fully-controlled devices BJT,Mosfet, IGBT,GTO 3 types of power devices Power Diodes Uncontroled power device Diodes static characteristic On and off states controlled by the power circuit Analysis: Case 1: VDVF forward conduction--large current Case 2: VBRVD0 (reverse bias before breakdown)--leakage current Case 3: VDVBR breakdown--no damage when operated inside rating Diode dynamic characteristic More detailed diode dynamic characteristic in Chinese reference book 1) Maximum average forward current IF(AV) 2）Forward voltage UF 3）Recurrent peak reverse voltage URRM 4）Reverse recovery time trr 5）Operating temperature TJM 6) Peak forward surge current IFSM Key parameters of power diode Thyristors tq=trr+tgr For successful turn-off, reverse voltage required for an interval greater than the turn-off interval IL: latching current, should be added, which is a special period of holding current. Thyrisotor family Full controlled power devices block forward and reverse voltage with zero current conduct large currents with zero voltage drop switch