Topic 4Main contentsLast lecture reviewLoss of power devicesDC-DC Switch-Mode ConvertersBuck converter
Main contents • Last lecture review • Loss of power devices • DC-DC Switch-Mode Converters • Buck converter Topic 4
DiodeGTOIGCT1Thyristor-11111BJT1SiCBJT111-1Gen.2Gen.6IGBT+Max.6500VMax.600v111MOSFET-1VSJ11n-1MOSFET1-SICJFET-11-SiCMOSFET-Sic diode11--GaNHEMTThyristor&MOSFETeraSiIGBTeraSiCand/orGaNera??19701990201020202013VOIE
GaNGaNSicHighendMOSFETTriacsIGBTBipolarThyristorIGCT格n品Lowend.Industry,EnerHomeappliances600Vorless200V120oVormore3.3kVandmoreMasstransportationConsumersystemsVoltageIGBTisgaining shares in highvoltage lowend solutionsandlowvoltagehighsolutions,thankstoitspriceerosion.SiC is to become thehighend solution inmedium and highvoltage.It is still uncertain to position GaN on this graph
IGBT is gaining shares in high voltage low end solutions and low voltage high solutions, thanks to its price erosion. SiC is to become the high end solution in medium and high voltage. It is still uncertain to position GaN on this graph
1SummaryDiode(1) Uncontrolled devicethvristor（晶闸管or(2) Half-controlled deviceSiliconcontrolledRectifier（可控硅turned-on by a control signal and turned-off bythe power circuit(3) Fully-controlled devicePowerMOSFETIGBI, BJT, GTO, IGCTThe on and off states of the device arecontrolled by control signals
⑴ Uncontrolled device —— Diode 1 Summary ⑵ Half-controlled device ——thyristor (晶闸管)or Silicon controlled Rectifier (可控硅) turned-on by a control signal and turned-off by the power circuit ⑶ Fully-controlled device——Power MOSFET, IGBT, BJT, GTO, IGCT The on and off states of the device are controlled by control signals
Other classificationsV Current-driven (current-controlled) devicesVVoltage-driven (voltage-controlled) devices (Field-controlled devices)>Pulse-triggered devices>Level-sensitive (level-triggered)devices.Unipolardevices（单极型器件）（Majoritycarrierdevices)·Bipolardevices（双极型器件）（Minoritycarrierdevices)·Compositedevices（复合型器件）6
6 Other classifications ✓Current-driven (current-controlled) devices ✓Voltage-driven (voltage-controlled) devices (Fieldcontrolled devices) ➢Pulse-triggered devices ➢Level-sensitive (level-triggered) devices ⚫Unipolar devices (单极型器件) (Majority carrier devices) ⚫Bipolar devices (双极型器件) (Minority carrier devices) ⚫ Composite devices (复合型器件)
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