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IGBT Forum Discussions

Lisa1
Employee
Employee
Hello,

Why does the collector current at high temperature get lower than that at low temperature after a certain value of V_GE?
For instance, as shown in the transfer characteristic curve, Ic, at V_GE below 7.5V, is higher at 150°C than at 25°C. While as V_GE goes above 7.5V 150°C curve has lower Ic value than the 25°C curve.

5161.attach

Thank you!
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1 Solution
Giuseppe_De_Fal
Moderator
Moderator 10 solutions authored 10 replies posted 10 sign-ins
Moderator
Hi Lisa,
the reason of this behavior is related to two different contribution of the IGBT voltage drop, one comes from the channel resistance of the MOS structure and the other comes from the voltage drop in the drift zone.

  • For 'low' VGE, the main contribution of the voltage drop comes from channel resistance, and it has a positive dependence with the temperature (that means that at high temperature the device carries more current for the same VCE).
  • At 'high' VGE, the effect of the drift zone resistance becomes predominant, and this has a negative temperature coefficient (that is, at high temperature the device carries less current for the same VCE).

The boundary between the two regions is often called ZTC (zero temperature coefficient point).

It is very important to guarantee that the IGBT works well inside the region with negative temperature coefficient, especially in applications where multiple devices are parallelized, because it guarantees that the current sharing between the devices is always uniform. In the case of the device in your example, the ZTC is at VGE=7.5V and this is the reason why the recommendation is to operate the device with a VGE that is much higher than 7.5V.


I hope that this helps.

Best Regards,
Giuseppe De Falco

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1 Reply
Giuseppe_De_Fal
Moderator
Moderator 10 solutions authored 10 replies posted 10 sign-ins
Moderator
Hi Lisa,
the reason of this behavior is related to two different contribution of the IGBT voltage drop, one comes from the channel resistance of the MOS structure and the other comes from the voltage drop in the drift zone.

  • For 'low' VGE, the main contribution of the voltage drop comes from channel resistance, and it has a positive dependence with the temperature (that means that at high temperature the device carries more current for the same VCE).
  • At 'high' VGE, the effect of the drift zone resistance becomes predominant, and this has a negative temperature coefficient (that is, at high temperature the device carries less current for the same VCE).

The boundary between the two regions is often called ZTC (zero temperature coefficient point).

It is very important to guarantee that the IGBT works well inside the region with negative temperature coefficient, especially in applications where multiple devices are parallelized, because it guarantees that the current sharing between the devices is always uniform. In the case of the device in your example, the ZTC is at VGE=7.5V and this is the reason why the recommendation is to operate the device with a VGE that is much higher than 7.5V.


I hope that this helps.

Best Regards,
Giuseppe De Falco
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