dependency of short circuit capability with some factors

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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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First like received Welcome! First question asked
The short-circuit time should derating with the bus voltage, gate voltage and temperature increase ,
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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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User17671
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5 questions asked First question asked First reply posted
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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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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