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Gate Driver Requirement. IGBT Gate Driver Calculation. What is the most important requirement for an IGBT driver ?. Gate Peak current. Which gate driver is suitable for the module SKM 200 GB 128D ?.

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what is the most important requirement for an igbt driver

What is the most important requirement for an IGBT driver ?

Gate Peak current

slide3

Which gate driver is suitable for the module SKM 200 GB 128D ?

reverse recovery current Diode should be -

1.5 x I diode by 80 degree case

130A x 1.5 = 195A

Design parameters:

fsw = 10 kHz

Rg = ?

Gate resistor in range of “test – gate resistor”

Conditions for a safety operation

how to find the right gate resistor

195A – max reverse recovery current

Rg = 7 Ohm

Two gate resistors are possible for turn on and turn off

Ron = 7 Ohm

Roff = 10 Ohm

How to find the right gate resistor ?
difference between trench and spt technology
Trench Technology needs a smaller Gate charge
    • Driver has to provide a smaller Gate charge
  • SPT Technology needs more Gate charge compared to Trench Technology
    • Driver has to provide a higher Gate charge
Difference between Trench- and SPT Technology
slide8

The suitable gate driver must provide the required

    • Gate charge (QG) – power supply of the driver must provide the average power
    • Average current (IoutAV) – power supply
    • Gate pulse current (Ig.pulse) – most important
  • at the applied switching frequency (fsw)

Demands for the gate driver

slide9

Gate charge (QG) can be determined from fig. 6 of the SEMITRANS data sheet

The typical turn-on and turn-off voltage of the gate driver is

VGG+ = +15V

VGG- = -8V

15

 QG = 1390nC

-8

1390

Determination of Gate Charge

slide10

Calculation of average current:

  • IoutAV = P / U V = +Vg + [-Vg]
  • with P = E * fsw = QG * V * fsw
  •  IoutAV = QG * fsw

= 1390nC * 10kHz = 13.9mA

Absolute value

Calculation of the average current

power supply requirements
Gate charge
    • The 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)
  • Average current
    • Is related to the transformer
Power supply requirements
slide12

Examination of the peak gate current with minimum gate resistance

    • E.g. RG.on = RG.off = 7
    • Ig.puls≈ V / RG + Rint= 23V / 7 + 1 = 2.9 A

Calculation of the peak gate current

pulse power rating of the gate resistor
P total – Gate resistor
    • Ppulse Gate resistor = I out AV x V
    • More 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.

Pulse power rating of the gate resistor
slide14

The absolute maximum ratings of the suitable gate driver must be equal or higher than the applied and calculated values

    • Gate charge QG = 1390nC
    • Average current IoutAV = 13,9mA
    • Peak gate current Ig.pulse = 2.9 A
    • Switching frequency fsw = 10kHz
    • Collector Emitter voltage VCE = 1200V
  • Number of driver channels: 2 (GB module)
    • dual driver

Choice of the suitable gate driver

slide15

According to the applied and calculated values, the driver e. g. SKHI 22A is able to drive SKM200GB128D

Calculated and

applied values:

  • Ig.pulse = 2.9 A@ Rg = 7 + R int
  • IoutAV = 13.9mA
  • fsw = 10kHz
  • VCE = 1200V
  • QG = 1390nC

Comparison with the parameters in the driver data sheet

slide17

Simple

  • Adaptable
  • Expandable
  • Short time to market
  • Two versions
    • SKYPER™ (standard version)
    • SKYPER™ PRO (premium version)

Driver core for IGBT modules

slide18

SKYPER

  • Driver board
  • SEMIX 3 IGBT half bridge
  • with spring contacts

Assembly on SEMiXTM 3 – Modular IPM

slide19

take 3 for 6-packs

with adapter board

solder directly in your main board

modular IPM using SEMiX®

SKYPER™ – more than a solution

slide22

vGE,T1(t)

vGE,T2(t)

VGG+

T1

D1

VGE, Io

VGE(th)

0

t

vCE,T1(t)

iC,T1(t)

VCC

T2

D2

IO

iv,T2

0

t

vCE,T2(t) =vF,D2(t)

iF,D2(t),iC,T2(t)

VCC

IO

  • Why changes VGE,T2 when T1 switches on?

0

t

Cross conduction behavior

slide23

When the outer voltage potential V changes, the load Q has to follow

  • This leads to a displacement current iV

IGBT - Parasitic capacitances

slide24

vCE,T2(t)

VCC

vGE,T2(t)

VGG+

VGE(th)

0

t

0

iC,T2(t)

iv,T2(t)

t

0

t

iC,T2

CGC,T2

iv,T2

vCE,T2

RGE,T2

vGE,T2

  • Diode D2 switches off and takes over the voltage
  • T2 “sees” the voltage over D2 as vCE,T2
  • With the changed voltage potential, the internal capacitances change their charge
  • The displacement current iv,T2 flows via CGC,T2, RGE,T2 and the driver
  • iv,T2 causes a voltage drop in RGE,T2 which is added to VGE,T2
  • If vGE,T2 > VGE(th) then T2 turns on (Therefore SK recommends: VGG- = -5…-8…-15 V)

Switching: Detailed for T2

gate clamping how

Z18

PCB design because no cable close to the IGBT

Gate clamping ---- how ?
problem 4 short circuit
Over voltage
    • 1200V ----- is chip level ---- consider internal stray inductance
    • +/- 20V----- gate emitter voltage ---- consider switching behavior of freewheeling diode
  • Over current
    • Power dissipation of IGBT (short circuit current x time)
    • Chip temperature level
Problem 4 ---------------------------- Short circuit
dead time explanation31
Example:
    • Dead time = 3 us logic level
      • Turn on delay 1 us
      • Turn off delay 2.5 us
        • Td – toff delay + ton delay = real dead time
        • Real dead time: 3us – (2.5us+1us) = 1.5 us
Dead time explanation
our final recommendation
IGBT driver must provide the peak Gate current
  • The stray inductance should be very small in the gate driver circuit
  • Gate/Emitter resistor and Gate/Emitter capacitor (like Ciss) very close to the IGBT
  • Turn off status must have a very low impedance
  • High frequency capacitors very close to the IGBT driver booster
  • Don’t use bipolar transistors for the booster
  • Protect the Gate/Emitter distance against over voltage
  • Don’t mix;
    • Peak current
    • Gate charge
Our final recommendation