IGBT driving aspect

1. IGBT driving aspect Zhou Yizheng

2. IGBT driving • Driving voltage level • Effect of turn on/off • Rge, Cge, Lg • Driving capability • Isolation • Thermal • Protection • Parasitic turn on • Over voltage • Short circuit/over current

3. Tvj=125C Tvj=125C Driving voltage level • Positive voltage Effect to Vcesat Vge，Vcesat note：max. allowed Vge is 20V Effect to short cicuit Vge，Isc（tsc）

4. Driving voltage level • Negative voltage • To guarantee safety off state, avoid parasitic miller turn on • Turn on delay increase (dead time) • Slightly reduce tf and Eoff • Increase driving power Miller capability effect

5. Effect of turn on/off • Rgon Control of dv/dt and di/dt with gate resistor Turn-on with smaller than nominal gate resistor: dv/dt = 1.4kV/µs di/dt = 8.7kA/µs ICpeak = 2.7kA Eon = 544mWs Turn-on with nominal gate resistor (datasheet value): dv/dt = 0.9kV/µs di/dt = 6.4kA/µs ICpeak = 2.4kA Eon = 816mWs Turn-on with larger than nominal gate resistor: dv/dt = 0.3kV/µs di/dt = 3.0kA/µs ICpeak = 1.8kA Eon = 2558mWs

6. Effect of turn on/off • Rgoff Control of dv/dt and di/dt with gate resistor • dv/dt is controllable with gate resistor. A larger resistor will result in a smaller dv/dt. • di/dt is only controllable if the gate voltage doesn’t drop below the Miller Plateau level before IC starts to decrease. This is in general the case for a gate resistor value close to the datasheet value. With larger resistors a control of di/dt starts to work.

7. Effect of turn on/off • Cge Independently control of dv/dt and di/dt

8. For similar Eon, we can: 1.7ohm200nF 4.6ohm0nF

9. For similar di/dt, we can: 1.7ohm46nF 2.6ohm0nF

10. Rge vs. Cge • Using Cge shows better Eon*di/dt coefficient • Using Cge can significantly increase driving power P=∆U*(Qge+Cge*∆U)*f • Using Cge can significantly increase driving peak current, require more powerful driver (output peak current capability) • The tolerance of Cge should be taken care when used in IGBT paralleling application • Using Cge may cause gate current oscillation, which leads to higher gate peak voltage.

11. Cable length influence With long cable With short cable

12. For similar Eon, we can: • With fixed Cge • With fixed Rge

13. Cable length influence • Cable length (Lg) shows similar Eon*di/dt coefficient as Rge, This mainly due to Lg effect both during di/dt period and dv/dt period (same as Rge) • Long cable significantly induce the turn on delay time • Long cable is a EMI receiver, which can cause Vge spike and unstable. • Loosing gate cable inductance will significantly increase Eon, which should especially paid attention in active adaptor design. Long cable should be avoid to be used. But loosing gate inductance should also be paid attention

14. Effect of turn on/off • Driving capability • Peak current capability • Power capability • Maximum driver peak currentU = 30V @ 15V switching • Driver power Slow down turn on/off speed Driver losses Vge goes down Power supply losses

15. 3 2 2000 ! 1 IR(t) [A] ! 1000 0 2 locus iR(t)*vR(t) 0 1 0 3 0 1000 2000 3000 VR(t) [V] Effect of turn on/off • Turn on/off criteria Redundant information on di/dt and dv/dt Diode SOA

16. Isolation

17. Isolation • Isolation transformer • Isolation test • Partial discharge test • Parasitic capacitor (Primary - secondary)

18. Thermal • Influenced parameters • Module case temperature • Driving power (switching frequency, Qg) • Driving peak current • Sensitive parts • Gate resistor • Booster • Power supply • Fiber

19. Thermal • If system internal ambient temperature is known. • From delt Tca, we can check temperature rise due to module itself heating • Adding temperature rise due to driving signal, real driver board temperature can be gotten. System cooling can significant improve driver cooling condition

20. Protection • UVLO • Interlock / generating deadtime • Vge over voltage • Parasitic turn on • Short circuit protection • Over voltage protection (for short circuit off) • Active Clamping • DVRC (Dynamik Voltage Raise Control) • di/dt-Feedback • Soft-Shut-Down • Two-Level Turn-off

21. Protection • UVLO • Avoid driving IGBT with low voltage causing thermal issue • Avoid series break down • Interlock / generating deadtime • Avoid short through by software mistake • Hardware deadtime should be shorter than software deadtime

22. Protection • Limitation of increase of gate voltage due to positive feedback over CGC and due to di/dt • Limitation of short circuit currents • Vge over voltage Methode 1 Gate-Supply Clamping Methode 2 Gate-Emitter Clamping

23. Protection • Parasitic turn on • minus voltage off • separate gate resistors, using small Rgoff and big Rgon • Additional gate emitter capacitor to shunt the Miller current • Active Miller clamping

24. Ic Vce Vce SC II OC Ic SC I Protection • Short circuit protection • Desaturation detect

25. Protection • Short circuit protection • Desaturation detect Based on variable reference voltage Based on fixed reference voltage

26. Protection • Short circuit protection • Desaturation detect • Over current protection? • Noise immunity is poor • Blanking time hard to set for fixed reference voltage concept, especially for high voltage module • Current protect point hard to be accurate • Directly detect collector current • Digital controller to detect di/dt • By system current sensor

27. Protection • Over voltage protection • Active clamping

28. dic/dt=11kA/µs uGE(t) @ Tj=25°C iC(t) RG=3.6W EOFF=0.9J uCE(t) uGE(t) dic/dt=3.4kA/µs @ Tj=25°C iC(t) 100pF UF4007 RG=13W uCE(t) 3xSM6T220A EOFF=1.95J IRFD 120 47R UF4007 UAC 4xSM6T220A +16V RMOS 56 BYD77 ZPD16 URAC 44H11 MFP-D RAC=15W FZ2400R17KE3 PWM 15R RG=1.5W 45H11 BYD77 MFN-D -16V Protection • Over voltage protection • DVRC (Dynamic Voltage Raise Control)

29. Protection • Over voltage protection • di/dt protection

30. Protection • Over voltage protection • Soft shut down

31. Protection • Over voltage protection • Two level turn off VGE VGE Driver Out Driver Out VCE VCE IC IC With Two-Level Turn-OffVCE reduced to 640V Without Two-Level Turn-OffVCE reaches 1000V