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MOSFET (Si/SiC) Forum Discussions

User17671
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Hello again, can you also tell me what the dependence of short-circuit capability with bus voltage, gate voltage and temperature is? Thanks in advance!
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electricuwe
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Hi AnniLe,

some details on SC (e.g. example waveform) you can find in the following Application note:

https://www.infineon.com/dgdl/Infineon-Introduction_to_CoolSiC_1200V_SiC_MOSFET-ApplicationNotes-v01...

SC withstand time will be significantly reduced for gate voltages above 15 V. Therefore for applications needed SC capability we are recommending to use 15 V gate voltage, whereas applications not needing SC capability
Lower DC-link voltage will increase SC withstandtime approximately inverse proportional
Lower junction temperature before SC will give a slight increase in SC withstand time.

Best regards,
electricuwe

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å__å__
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Moderator First like received Welcome! First question asked
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The short-circuit time should derating with the bus voltage, gate voltage and temperature increase ,
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electricuwe
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Moderator 5 sign-ins 25 replies posted 10 solutions authored
Moderator
Hi AnniLe,

some details on SC (e.g. example waveform) you can find in the following Application note:

https://www.infineon.com/dgdl/Infineon-Introduction_to_CoolSiC_1200V_SiC_MOSFET-ApplicationNotes-v01...

SC withstand time will be significantly reduced for gate voltages above 15 V. Therefore for applications needed SC capability we are recommending to use 15 V gate voltage, whereas applications not needing SC capability
Lower DC-link voltage will increase SC withstandtime approximately inverse proportional
Lower junction temperature before SC will give a slight increase in SC withstand time.

Best regards,
electricuwe
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User17671
Level 1
5 questions asked First question asked First reply posted
Level 1
Hello electricuwe,

sorry for my late response but thanks for your explanation and the hint to the application note! I've an additional question... how can a short circuit protection be provided for a SiC module with short circuit capability of 3µs?

Thanks
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electricuwe
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Moderator 5 sign-ins 25 replies posted 10 solutions authored
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Hi AnniLe,

at first please note that SC withstand time is rated differently for Discrete and module. Discrete devices are specified with 3 us, modules with 2 us. However, SC protection can be provided in both cases. There are two main challenges:

- delay time and tolerances of the detection circuit have to be minimized
- in some applications, e.g. drives, cable or load capacitance lead to significant current spike at every switching event. It has to be ensured that these current spikes do not lead to a SC turn off

For low power applications, SC detection via shunt in the DC- or in the source is feasible. As a fast comparator the comparator inside1ED44176N01F might be used:
https://www.infineon.com/dgdl/Infineon-1ED44176N01F-DS-v02_00-EN.pdf?fileId=5546d46265487f7b01655c2d...

See schematic in the application note:
https://www.infineon.com/dgdl/Infineon-EVAL-M5-E1B1245N-SiC-ApplicationNotes-v01_00-EN.pdf?fileId=55...
We are just updating the application note with test results on this.

For higher power desat-detection is more appropriate. Many newer driver ICs, especially the ones using non-optic isolation technology, have small delay time and tolerance and can be configured to detect an SC within approx. 1.5 us. One device suitable for this is the 1ED020I12-F2: https://www.infineon.com/dgdl/Infineon-1ED020I12-F2-DataSheet-v02_01-EN.pdf?fileId=db3a304330f686060...

Note that due to the fact that in a Mosfet there is no need to wait for conductivity modulation taking place like in an IGBT, shorter blanking times are possible for Mosfets

If the system uses Sigma-Delta current measurement in the output phases, a simple digital circuit can be implemented to observe if the datastream stays at 0 or 1 for more than approx. 1 us, indicating a SC condition.

Best regards,

electricuwe
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