Topic 7Main contentsSnubber Circuits OverviewDiodes/SCR/MOSFET/IGBT SnubberTurn-on and turn-off snubberDriver Circuits for Power Switches
Main contents • Snubber Circuits Overview • Diodes/SCR/MOSFET/IGBT Snubber • Turn-on and turn-off snubber • Driver Circuits for Power Switches Topic 7
27-1Induction1 The issues which the switch faced in applications（电力电子器件应用时面临的问题）(1) switching lossVaIf, (te(on) + te(off))2→Switchingloss oc fs,wewant f↑ So L, C sizel, butVdetlosses limit us.fe)Figure 2-6 Ceneric-switch switching characteristics (linearized): (a) simplified clampedinductive-switching circuit, (b) switch waveforms, (c) instantaneous switch power loss
3 27-1 Induction 2 s Vd Io fs (tc(on) + tc(off ) ) P = ⑴ switching loss →Switching loss fs , we want fs↑ So L, C size↓, but losses limit us. 1 The issues which the switch faced in applications (电力电子器件应用时面临的问题)
(2)Overshoots（电压过冲）odi.+dtVdLVswoVsWL1，L2，L3=strayinductance（杂散电感L。=L1+L2+L3
⑵ Overshoots (电压过冲) Io Vd L1 L2 L3 Sw vsw + - i c Vd L dic dt vSW L1 , L2 , L3= stray inductance (杂散电感) Lσ=L1+L2+L3
(3) Safe operating area (SOA)Some devices have limitations on simultaneous voltage+ current applied instantaneously (IGBT, MOSET, etc.)SWTurn-offilocusDevice can operate at Iand can operate at Vin:SOAbut not at same timeswVinVswsw5
5 ⑶ Safe operating area (SOA) Some devices have limitations on simultaneous voltage + current applied instantaneously (IGBT, MOSET, etc.) Device can operate at IL and can operate at Vin, but not at same time isw iL SOA Turn-off locus vsw Vin vsw isw
(4) di/dt or dv/dt limitsAlso, some devices have di/dt or dvldt limits (espthyristortype devices).(5) EMIHigh di/dt, dvldt lead to EMl, affects control circuits.(dvldt→ capacitive coupling, di/dt→ inductivecoupling)
⑷ di/dt or dv/dt limits Also, some devices have di/dt or dv/dt limits (esp. thyristor type devices). ⑸ EMI High di/dt, dv/dt lead to EMI, affects control circuits. (dv/dt→ capacitive coupling, di/dt→ inductive coupling)