TPS55340-Q1: Switching losses estimation

Ivan Goncharov

Part Number: TPS55340-Q1
Other Parts Discussed in Thread: TPS55340

Hi,

TPS55340 is used in SEPIC configuration and I need to estimate IC temperature.

Rds_on is presented in datasheet, so it's possible to calculate power dissipation when internal MOSFET is is open.

But how can I calculate switching losses? I can't find in datasheet nothing useful for this pupouse. Am I missing something?

over 3 years ago

0 Youhao Xi over 3 years ago

TI__Guru 73810 points

Hi Ivan,

Thank you for posting. We will need to check with our design team about the internal FET parameter in order to estimate the losses.

Thanks,

Youhao Xi, Applications Engineering

0 Youhao Xi over 3 years ago in reply to Youhao Xi

TI__Guru 73810 points

Hi Ivan,

Sorry for the delay. We are still working on this by digging into the database, and hopefully we can get the info in the next couple of days.

Thanks,

Youhao

0 Youhao Xi over 3 years ago in reply to Youhao Xi

TI__Guru 73810 points

Hi Ivan,

Our design team gets the answer:

Qg= 3.46nC

Coss = 3.2nF

You need to measure the SW rising time and falling time to get the switching transition (related to external layout and circuit parameters). The switching losses can be estimated as:

Psw = Vin x Qg x Fsw + 2/3 x (Vin +Vout) x Iin x (tr + tf) x Fsw + 1/2 x Coss x (Vin +Vout)^2 x Fsw

Hope this helps.

Thanks,

Youhao

0 Ivan Goncharov over 3 years ago in reply to Youhao Xi

Prodigy 120 points

Thank you very much, it helped a lot.

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TPS55340-Q1: Switching losses estimation