1 Semikron Hong Kong Norbert Pluschke IGBT Gate Driver Calculation Gate Driver Requirement

2 Semikron Hong Kong Norbert Pluschke What is the most important requirement for an IGBT driver ? Gate Peak current

3 Semikron Hong Kong Norbert Pluschke Conditions for a safety operation n Which gate driver is suitable for the module SKM 200 GB 128D ? Design parameters: f sw = 10 kHz Rg = ? reverse recovery current Diode should be x I diode by 80 degree case 130A x 1.5 = 195A Gate resistor in range of “test – gate resistor”

4 Semikron Hong Kong Norbert Pluschke How to find the right gate resistor ? Rg = 7 Ohm Two gate resistors are possible for turn on and turn off Ron = 7 Ohm Roff = 10 Ohm 195A – max reverse recovery current

5 Semikron Hong Kong Norbert Pluschke Difference between Trench- and SPT Technology nTrench Technology needs a smaller Gate charge uDriver has to provide a smaller Gate charge nSPT Technology needs more Gate charge compared to Trench Technology uDriver has to provide a higher Gate charge

6 Semikron Hong Kong Norbert Pluschke Driver performance – different IGBT technologies needs different gate charge nTrench IGBT with same chip current Gate charge is 2.3 uC

7 Semikron Hong Kong Norbert Pluschke Driver performance – different IGBT technologies needs different gate charge nSPT IGBT with same chip current Gate charge is 3 uC

8 Semikron Hong Kong Norbert Pluschke Demands for the gate driver n The suitable gate driver must provide the required è Gate charge (Q G ) – power supply of the driver must provide the average power è Average current (I outAV ) – power supply è Gate pulse current (I g.pulse ) – most important n at the applied switching frequency (f sw )

9 Semikron Hong Kong Norbert Pluschke Determination of Gate Charge n Gate charge (Q G ) can be determined from fig. 6 of the SEMITRANS data sheet  Q G = 1390nC The typical turn-on and turn-off voltage of the gate driver is V GG+ = +15V V GG- = -8V

10 Semikron Hong Kong Norbert Pluschke Calculation of the average current n Calculation of average current: n I outAV = P /  U  V = +Vg + [-Vg] n with P = E * f sw = Q G *  V * f sw n  I outAV = Q G * f sw = 1390nC * 10kHz = 13.9mA Absolute value

11 Semikron Hong Kong Norbert Pluschke Power supply requirements nGate charge uThe power supply or the transformer must provide the energy (Semikron is using pulse transformer for the power supply, we must consider the transformed average power from the transformer) nAverage current uIs related to the transformer

12 Semikron Hong Kong Norbert Pluschke Calculation of the peak gate current n Examination of the peak gate current with minimum gate resistance è E.g. R G.on = R G.off = 7   I g.puls ≈  V / R G + R int = 23V / 7  + 1  = 2.9 A

13 Semikron Hong Kong Norbert Pluschke Pulse power rating of the gate resistor nP total – Gate resistor uP pulse Gate resistor = I out AV x  V uMore information: The problem occurs when the user forgets about the peak power rating of the gate resistor. The peak power rating of many "ordinary" SMD resistors is quite small. There are SMD resistors available with higher peak power ratings. For example, if you take an SKD driver apart, you will see that the gate resistors are in a different SMD package to all the other resistors (except one or two other places that also need high peak power). The problem was less obvious with through hole components simply because the resistors were physically bigger. The Philips resistor data book has a good section on peak power ratings.

14 Semikron Hong Kong Norbert Pluschke Choice of the suitable gate driver n The absolute maximum ratings of the suitable gate driver must be equal or higher than the applied and calculated values è Gate charge Q G = 1390nC è Average current I outAV = 13,9mA è Peak gate current I g.pulse = 2.9 A è Switching frequency f sw = 10kHz è Collector Emitter voltage V CE = 1200V è Number of driver channels: 2 (GB module) è dual driver

15 Semikron Hong Kong Norbert Pluschke Comparison with the parameters in the driver data sheet Calculated and applied values: n I g.pulse = 2.9 R g = 7  + R int n I outAV = 13.9mA n f sw = 10kHz n V CE = 1200V n Q G = 1390nC n According to the applied and calculated values, the driver e. g. SKHI 22A is able to drive SKM200GB128D

16 Semikron Hong Kong Norbert Pluschke n PCB Driver and PCB mountable Driver for single, half bridge, six pack modules n integrated potential-free power supply n switching frequency up to 100kHz n output peak current up to 30A n Gate charge up to 30µC n dv/dt capability up to 75kV/µs n high EMI immunity n TTL- an CMOS-compatible inputs and outputs with potential isolation via opto coupler or transformer (isolation up to 4kV AC ) n protection (interlock, short pulse suppression, short circuit protection via V CE - monitoring, under voltage monitoring, error memory and error feedback) SEMIDRIVER

17 Semikron Hong Kong Norbert Pluschke Product overview (important parameters)

18 Semikron Hong Kong Norbert Pluschke Driver core for IGBT modules Simple Adaptable Expandable Short time to market Two versions  SKYPER™ (standard version)  SKYPER™ PRO (premium version)

19 Semikron Hong Kong Norbert Pluschke Assembly on SEMiX TM 3 – Modular IPM n SKYPER n Driver board n SEMIX 3 IGBT half bridge with spring contacts

20 Semikron Hong Kong Norbert Pluschke SKYPER™ – more than a solution modular IPM using SEMiX ® with adapter board solder directly in your main board take 3 for 6-packs

21 Semikron Hong Kong Norbert Pluschke Selection of the right IGBT driver Advice

22 Semikron Hong Kong Norbert Pluschke Problem Cross conduction Low impedance

23 Semikron Hong Kong Norbert Pluschke Cross conduction behavior v CE,T1 (t) i C,T1 (t) V CC IOIO 0 t v GE,T1 (t) v GE,T2 (t) V GE, Io V GE(th) 0 t V GG+ V CC IOIO 0 t v CE,T2 (t) = v F,D2 (t) i F,D2 (t), i C,T2 (t) T1D1 T2D2 i v,T2 nWhy changes V GE,T2 when T1 switches on?

24 Semikron Hong Kong Norbert Pluschke IGBT - Parasitic capacitances nWhen the outer voltage potential V changes, the load Q has to follow nThis leads to a displacement current i V

25 Semikron Hong Kong Norbert Pluschke Switching: Detailed for T2 i v,T2 v CE,T2 v GE,T2 i C,T2 R GE,T2 C GC,T2 v CE,T2 (t) V CC 0 t 0 t i C,T2 (t) i v,T2 (t) v GE,T2 (t) V GE(th) 0 t V GG+ uDiode D2 switches off and takes over the voltage uT2 “sees” the voltage over D2 as v CE,T2 uWith the changed voltage potential, the internal capacitances change their charge uThe displacement current i v,T2 flows via C GC,T2, R GE,T2 and the driver ui v,T2 causes a voltage drop in R GE,T2 which is added to V GE,T2 uIf v GE,T2 > V GE(th) then T2 turns on (Therefore SK recommends: V GG- = -5…-8…-15 V)

26 Semikron Hong Kong Norbert Pluschke Problem gate protection Z

27 Semikron Hong Kong Norbert Pluschke Gate clamping ---- how ? Z18 PCB design because no cable close to the IGBT

28 Semikron Hong Kong Norbert Pluschke Problem booster for the gate current Use MOSFET for the booster For small IGBTs is ok

29 Semikron Hong Kong Norbert Pluschke Problem Short circuit nOver voltage u1200V is chip level ---- consider internal stray inductance u+/- 20V----- gate emitter voltage ---- consider switching behavior of freewheeling diode nOver current uPower dissipation of IGBT (short circuit current x time) uChip temperature level

30 Semikron Hong Kong Norbert Pluschke Problem 5 – dead time between top and bottom IGBT Turn on and turn off delay must be symetrical

31 Semikron Hong Kong Norbert Pluschke Dead time explanation

32 Semikron Hong Kong Norbert Pluschke Dead time explanation nExample: uDead time = 3 us logic level l Turn on delay 1 us l Turn off delay 2.5 us –Td – toff delay + ton delay = real dead time –Real dead time: 3us – (2.5us+1us) = 1.5 us

33 Semikron Hong Kong Norbert Pluschke Our final recommendation nIGBT driver must provide the peak Gate current nThe stray inductance should be very small in the gate driver circuit nGate/Emitter resistor and Gate/Emitter capacitor (like Ciss) very close to the IGBT nTurn off status must have a very low impedance nHigh frequency capacitors very close to the IGBT driver booster nDon’t use bipolar transistors for the booster nProtect the Gate/Emitter distance against over voltage nDon’t mix; uPeak current uGate charge

34 Semikron Hong Kong Norbert Pluschke