IGBT parallelingZhou Yizheng

Set date Page 2Copyright © Infineon Technologies 2010. All rights reserved.

Current sharing

Current sharing

Static current sharing

¬ Affect conduction losses distribution

Dynamic current sharing

¬ Affect dynamic losses distribution and dynamic stress

Set date Page 3Copyright © Infineon Technologies 2010. All rights reserved.

Parameters effecting current balance

Static sharing Dynamic sharing

Commutation loop impedance X

AC loop impedance X

Thermal X X

Driver symmetry X

Module static parameters X

Module switching parameters X

Magnetic field X

Communicating loop: dynamic & static current sharingAC loop: static current sharing

Set date Page 4Copyright © Infineon Technologies 2010. All rights reserved.

Test set up

Module: FZ1500R33HE3.

¬ Channel1 IGBT module1 collector current

¬ Channel 2 IGBT module2 collector current

¬ Channel 3 IGBT module1 gate voltage

¬ Channel 4 IGBT module2 gate voltage

Bus bar symmetry

Stray impedance in the commutation loop influence both dynamic current sharing and static current sharing. (low impedance high current)

Symmetrical Busbar

Additional stray impedance applied

Bus bar symmetry

AC path have no influence to turn on dynamic current sharing, it influence the static current sharing, further influence the turn off dynamic current sharing and current redistribution. (low impedance high current)

Symmetrical AC path Unsymmetrical AC path

Bus bar symmetry

Thermal symmetry influence static current sharing and , but it is not so strong. (high temperature low current). Thermal symmetry have almost no influence to turn on current sharing, but can influence turn off current sharing20 degree

20 degree

20 degree20 degree

20 degree40 degree

20 degree40 degree

Inductor outside the SBInductor Right side in SBInductor Left side in SB

Magnetic field

Driver Outside the SB

Driver inside the SB

Driver Outside the SB

Driver inside the SB

Inductor influence for active board

Inductor influence to passive board

Magnetic field

For FZ+FZ double pulse test setup:

Cable connection inside bus bar influence both static current sharing and current redistribution(created magnetic field influence bus bar impedance), but almost no influence at turn on.

Magnetic filed of inductor can influence current redistribution and driver (if the driver is passive adaptor board based) further influence turn on current sharing and current redistribution.

If active adaptor board based driver is used, magnetic filed of inductor have almost no influence on turn on current sharing

Set date Page 10Copyright © Infineon Technologies 2010. All rights reserved.

Driving conecpt

Isolated

Each IGBT have its own isolated driver core

Active adopt board

One driver core with booster circuit on adaptor board

Passive adopt board(separate Rg)

One driver core with separate gate resistor on adaptor board

Passive adopt board(merged Rg)

With gate resistor on driver core, just cable to connect IGBT module gate

Driving concept

Isolated Active

Merged Rg Separate Rg

Symmetrical bus bar

Driving concept

Isolated Active

Merged Rg Separate Rg

Symmetrical bus bar

Driving concept

Isolated driver

Passive separated Rg

Unsymmetrical bus bar

Cable lengthMerged Rg

Separate Rg

20cm / 20 cm 20cm / 100 cm 101cm / 100 cm

20cm / 20 cm 20cm / 100 cm 101cm / 100 cm

Cable length

Separate Rg

Merged Rg

20cm / 20 cm 20cm / 100 cm 101cm / 100 cm

20cm / 20 cm 20cm / 100 cm 101cm / 100 cmIc1 Right IGBTIc2 Left IGBTVge1 Left IGBTVge2 Right IGBT

Driving

Different driver concept shows almost similar turn on/off performance, at precondition that system is symmetry.

Active board shows a little bit poorer turn on current sharing performance

Passive board shows high amplitude of current redistribution and oscillation frequency

In unsymmetrical system, isolated driver shows better turn on dynamic current sharing and almost similar turn off dynamic current sharing.

Separate Rg shows better dynamic current sharing than merged Rg, if gate cable is unsymmetrical.

Set date Page 17Copyright © Infineon Technologies 2010. All rights reserved.

Module parameters

Vcesat, Vf

Influence static current sharing

Vth, Vp

Influence dynamic current sharing

Set date Copyright © Infineon Technologies 2010. All rights reserved. Page 18

Module parameters

Same Vcesat class Same Vcesat class Different Vcesat class

Module parameters

Different Vcesat class(+/-1) almost show no influence to static current sharing. positive temperature coefficient + round up/down

Different module have quite small influence to module dynamic current sharing(current redistribution).

Vcesat 3.33 3.31

Vth 5.90 5.90

Vp 10.33 10.28

Vcesat 3.34 3.31

Vth 5.86 5.90

Vp 8.93 10.28

Vcesat 3.31 3.37

Vth 5.90 5.90

Vp 10.33 10.23

Set date Page 20Copyright © Infineon Technologies 2010. All rights reserved.

Conclusion

Conclusion

System symmetry is at first priority (including commutation loop symmetry, AC path symmetry and AC output cable position).

Based on symmetrical system, either isolated driver or active adaptor board or passive adaptor board all can get very good current sharing results.

If cable length for passive adaptor is not same, separated Rg and emitter Rg is recommended.

Module influence to current sharing is quite small. IGBT Vcesat class +/-1 is quite Ok for current sharing. It’s better to take same Vf class module.

System magnetic field effect need to be care about