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MOSFET (Si/SiC) Forum Discussions

kagarwal37
Level 2
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Level 2

Hi,

I couldn't find any switching losses ratings in the datasheet for the CoolMOS part number: IPAW60R180P7SXKSA1. How can I use the datasheet to ensure that this device can handle the switching losses experienced in my application?

Also what is the recommended gate drive voltage for this part? Is +10V, 0V good enough for turn on and turn off?

Sincerely,
Kartavya Agarwal.

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Pablo_EG
Moderator
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Moderator

Hello Kartavya Agarwal,

Thank you for posting on Infineon Community.

Our Power MOSFET datasheets typicaly do not include information about the switchin losses.
This is because these losses vary greatly with:
-Driving voltage (Vgs)
-Gate resistors (Rgon/Rgoff)
-Drain current (Id)
-Blocking voltage (Vds)
-Junction temperature (Tj)
-The parasitics of the circuit.
-At high gate resistance or weak gate driving, it may also vary when at high frequency (Fsw)

We offer very accurate simulation models in PSpice language, here you can find the link for your device:
https://www.infineon.com/cms/en/product/power/mosfet/n-channel/500v-950v/ipaw60r180p7s/#!simulation

By setting up a double pulse simulation, you can tune the circuit parameters to match your application.
This way, you can asses with high accuracy if the switching losses are acceptable for your application.
With the Level 3 models (included in the library) you can also asses the temperature rise in the MOSFET.


Regarding the driving voltage, judging by the output characteristic graph form the datasheet, yes, 10V/0V is enough for the driving scheme.

Pablo_EG_0-1648170559696.png

The MOSFET will not go into the saturation region when in conduction.

Best regards,
Pablo

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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello Kartavya Agarwal,

Thank you for posting on Infineon Community.

Our Power MOSFET datasheets typicaly do not include information about the switchin losses.
This is because these losses vary greatly with:
-Driving voltage (Vgs)
-Gate resistors (Rgon/Rgoff)
-Drain current (Id)
-Blocking voltage (Vds)
-Junction temperature (Tj)
-The parasitics of the circuit.
-At high gate resistance or weak gate driving, it may also vary when at high frequency (Fsw)

We offer very accurate simulation models in PSpice language, here you can find the link for your device:
https://www.infineon.com/cms/en/product/power/mosfet/n-channel/500v-950v/ipaw60r180p7s/#!simulation

By setting up a double pulse simulation, you can tune the circuit parameters to match your application.
This way, you can asses with high accuracy if the switching losses are acceptable for your application.
With the Level 3 models (included in the library) you can also asses the temperature rise in the MOSFET.


Regarding the driving voltage, judging by the output characteristic graph form the datasheet, yes, 10V/0V is enough for the driving scheme.

Pablo_EG_0-1648170559696.png

The MOSFET will not go into the saturation region when in conduction.

Best regards,
Pablo

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kagarwal37
Level 2
25 sign-ins 10 replies posted 10 sign-ins
Level 2

Hi Pablo,

Thank you very much for your response. A quick follow up question, on a very high level, can I use the total power dissipation rating of MOSFETs to figure out if the device will survive by calculating the switching and conduction losses and ensuring that the sum of the two is sufficiently below the Pd rating reported in the datasheet?

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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello Kartavya Agarwal,

The power dissipation rating given in the datasheet only gives the maximum power dissipation.
This would be in an ideal situation where the case of the MOSFET is constantly at 25C.
Therefore, this metric should not be used in your case.

If you are considering steady-state power dissipation, you can use the conduction losses, added to the switching losses (averaged to the switching period).
Then, use the thermal resistance provided in the datasheet to calculate the maximum power loss permitted for your application:

Pablo_EG_0-1648427591358.png

With no heatsink:

Pmax = (150 - Tamb)/Rth_jA

With heatsink:

Pmax = (150 - Tamb)/(Rth_jc + Rth_tim + Rth_heatsink)

Where: Tamb = max ambient temperature of your application, Rth_jA = junction to air resistance, Rth_jc = junction to case resistance, Rth_tim = thermal interface material resistance, Rth_heatsink = heatsink base to air resistance

Once Pmax is known, the operating power losses have to be kept well under this limit.

Assuming that Tamb = 50 and not hetsink, Pmax you be 1.613 W.

This is 16 times less than the "power dissipation" rating.

I hope this explanation helped.

Bets regards,

Pablo

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kagarwal37
Level 2
25 sign-ins 10 replies posted 10 sign-ins
Level 2

Hi Pablo,

Thank you very much for the detailed explanation, that really helps! A quick follow up, as of now, my calculated losses based on my application's topology is 2.2W accounting for both conduction and switching losses. This already puts me above the 1.613W limit calculated at 50C, and I expect the ambient temperature to be higher than 50C at this point.

In light of the above information, is it recommended that I find another part that can allow for higher dissipation?

Also, I want to clarify why we are using the Rth_ja value? Is that to be conservative? Because, if we can maintain the external case temperature at 100C, this would result in a power dissipation rating of 10.37W, using the same equation with Rth_jc. This is significantly higher than the calculation result when using Rth_ja.

Sincerely,
Kartavya Agarwal.

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Pablo_EG
Moderator
Moderator 250 sign-ins 250 replies posted 25 likes received
Moderator

Hello Kartavya Agarwal,

As you are already using a TO220 package, it is unlikely that you can find a P7S family part that has better power dissipation (Rth_jA).

The reason why I did the example with Rth_jA, is because I was assuming that in the application there is no heatsink attached to the MOSFET.
If there is a heatsink attached to the MOSFET, then the thermal resistance will be greatly reduced.
Therefore, you can either attach a heatsink to the device, or you can solder the backplate to the PCB.
The PCB will act as a heatsink, not as good as a proper heatsink, but better than leaving the backplate to air.

We could assume that the case stays below 100C, but how can we ensure that?
The air around it may be at 100C, but the case itself will be at a higher temperature.
Therefore, if there is no heatsink attached, it is recommended that Rth_jA be used.

If conduction losses are the main problem, you can select a lower Rdson part, to reduce the conduction losses.

Best regards,
Pablo

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kagarwal37
Level 2
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Level 2

Hi Pablo,

Thanks a lot for the detailed response. I'm actually in the initial PCB design phase and so may have the flexibility to select a different part, although that may not be ideal since I may have to redesign the gate driver. But I would prefer to go with a part that I know will survive in the worst case.

My main concern is with switching losses. In light of this information would your recommendation to use the same part change?

Sincerely,
Kartavya Agarwal.

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Pablo_EG
Moderator
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Moderator

Hello Kartavya Agarwal,

As mentioned in a previous response, you can increase the thermal conductivity by using a heatsink or attaching the backplate to the PCB.

However, you could change the gate structure so that the turn on and turn off are faster, thus reducing the switching losses.
This in turn will increase oscillations and noise, so it has to be designed carefully.

Another point could be that the part you have selected may not fit your application.
The CoolMOS P7S family that you have selected is tailored towards low switching frequencies such as active AC rectification (50Hz~60Hz).
If your application is an SMPS with a switching frequency in the kHz range, then I would recommend the P7 family.
You can expect lower switching losses.

Best regards,
Pablo

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kagarwal37
Level 2
25 sign-ins 10 replies posted 10 sign-ins
Level 2

Hi Pablo,

I have two applications with the following specifications:

1. Switching frequency = 200 kHz; Vds = 400V; Continuous drain current = 4 A

2. Switching frequency = 200 kHz; Vds = 40V; Continuous drain current = 12 A

Would you be able to recommend any particular family of Infineon products for the above two applications?

Sincerely,
Kartavya Agarwal.

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Pablo_EG
Moderator
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Moderator

Hello Kartavya Agarwal,

Your applications would not be suitable for the P7S you chose as per my previous comment.

For your first application, you could consider P7 family.

For the second one, you could search for a suitable part within the Optimos 5 80V family.
Please refer to the portfolio for further details:
https://www.infineon.com/cms/en/product/power/mosfet/n-channel/optimos-and-strongirfet-latest-family...

Pablo_EG_0-1648775297276.png

I would like to ask for your permission to close this thread, as it has drifted from the original request.
If you have further questions feel free to raise another ticket.

Best regards,
Pablo

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