Which MOSFET would you choose for a 24 V → 220 V, 100 W, 100 kHz push-pull inver

[cometa_gsm]

Hi everyone,

I’m designing a 24 V DC → 220 V AC, approximately 100 W push-pull inverter operating at around 100 kHz.

I’m currently selecting the MOSFETs for the primary side and would appreciate advice from engineers with practical experience designing high-frequency push-pull converters.

These are the four Infineon OptiMOS 6 MOSFETs I am considering:

IPP089N15NM6: 150 V  8.9 mΩ    Qoss 89 nC    Qg 29 nC
IPP130N20NM6: 200 V  13 mΩ     Qoss 116 nC   Qg 37 nC
IPP175N20NM6: 200 V  17.5 mΩ  Qoss 95 nC     Qg 31 nC
IPP339N20NM6: 200 V  33.9 mΩ  Qoss 48 nC     Qg 15.9 nC

My main question is:

Which of these would be the most sensible choice for minimum total losses and minimum temperature at 100 kHz?

I’m particularly interested in the trade-off between:

- conduction loss from RDS(on)
- switching loss
- Qoss / Coss
- gate-drive loss
- VDS voltage margin
- transformer leakage inductance and drain-voltage ringing
- snubber/clamp losses

The transformer is a P-core ferrite transformer, so leakage inductance and drain-voltage spikes are also a consideration.

The nominal primary voltage is 24 V, so the theoretical drain voltage in a push-pull topology is approximately 2 × Vin, but there will obviously be additional voltage spikes and ringing caused by transformer leakage inductance and parasitic inductances.

I’m not necessarily looking for the MOSFET with the lowest RDS(on) or the lowest Qg individually. I’m trying to understand which device would give the best overall efficiency in this particular application.

For example, the IPP089N15NM6 has by far the lowest RDS(on), but it is only a 150 V device and has higher Qoss than the IPP339N20NM6.

The IPP339N20NM6 has much lower Qoss and Qg, but its RDS(on) is almost 4 times higher.

The IPP130N20NM6 and IPP175N20NM6 seem to be compromises between these extremes.

What would you choose for this application, and why?

Thanks.

[makebit]

Use FETs with...
Low trr
Low Qgd/Qgs ratio
High-as -possible gate threshold voltage.

Remember to slow up the FET turn on enough so that you avoid spurious turn on (of the opposite fet in the leg) , and also dont get too much switching loss.

EG infineon CFD7 series...ie the type of fets that you might use for a phase shift full bridge or LLC converter

And here is an inverter that does the job for you, and its quite simple...

https://drive.google.com/file/d/1Ny6EfSOwureVrnTwOlKvx7Je39Jv5oyq/view?usp=sharing