ReviewQuestions1. What are power electronics?2. What is the gating characteristic of an IGBT?3. What is the gating characteristic of a MOSFET?4. What is a reverse recovery time of diodes?5. What is a reverse recovery current of diodes?
Review Questions 1. What are power electronics? 2. What is the gating characteristic of an IGBT? 3. What is the gating characteristic of a MOSFET? 4. What is a reverse recovery time of diodes? 5. What is a reverse recovery current of diodes?
2. Loss of power DevicesThree states of a power devicesONTransitionOFFCtrlsignal个v(t)i(t)Ploss=P(ON)+P(OFF)+P(turning-on)+P(turning-ff)+P(driving)+P(Snubber)Pswitching loss = P (tuming-on)+P (turning-of)
2. Loss of power Devices Three states of a power devices Ctrl signal v(t) i(t) ON Transition OFF Ploss=P(ON)+P(OFF)+P(turning-on)+P(turning-off)+P(driving)+P(Snubber) Pswitching loss=P(turning-on)+P(turning-off)
Pswitching loss=P(turning-on)+P(turning-f)(a)SwitchcontrolsignalOnoffApproximatecalculation:Oftot(Vp I。ton fs)P(turning-on)=uniVV.oP.(turning-f)=otaotr0thitre→d(on)c(oft)tdon)pr(t)ValeWdonyValoteon)Wdon) aVotelon)Won
Pswitching loss=P(turning-on)+P(turning-off) Approximate calculation: P(turning-on) 2 = D o on S 1 (V I t f ) P(turning-off)= ( 1 2 V I D o toff fS )
Pswitching loss=P(turning-on)+P(turning-of)Generally,Calculationforswitchinglossshouldscrutinizemanyparameters and curves of the datasheet of this devices, and considertherelationshipofdrivingresistanceanddynamiccharacteristicsThe best approach is to measure them under the conditions ofeverydesignedparametersandstatus
Pswitching loss=P(turning-on)+P(turning-off) Generally, Calculation for switching loss should scrutinize many parameters and curves of the datasheet of this devices, and considerthe relationship of driving resistance and dynamic characteristics. The best approach is to measure them under the conditions ofevery designed parameters and status
2.1 How to lower power loss(1) New generation devicesFromSi-baseddevicestoGaN-basedorSiC-basedDevicesAdvantages of new G devices:1. Lower voltage or resistance of ON-state;2. Almost eliminated reverse recovery of diode;3. Lower parasitic capacitance4. Faster switching time5. High operating frequencyNew devices havemuchless of both ON-state andtransition-statelosses
2.1 How to lower power loss (1) New generation devices From Si-based devices to GaN-based or SiC-based Devices Advantages of new G devices: 1. Lower voltage or resistance of ON-state; 2. Almost eliminated reverse recovery of diode; 3. Lower parasitic capacitance; 4. Faster switching time 5. High operating frequency New devices have much less of both ON-state and transition-state losses