efficiency vs switching frequency

Hi Ankush,

The WEBENCH model for the TPS54340 is a good starting point to estimate what happens when changing the switching frequency. This efficiency in this model matches well with a real circuit.

The largest change in power loss with switching frequency are switching losses. The loss can be estimated with equation 50 on page 33 of the datasheet. This equation shows a direct relationship between switching frequency and switching power losses. In other words higher switching frequency increases switching losses while a lower switching frequency decreases switching losses.

Let me know if this helps answer your question.

Best Regards,
Anthony

thanks anthony,

i have seen the webench model. with that i have simulated different designs for my different requirement.

when i was working on it, one more surprising thing was there, when i am increasing the input voltage range, keeping all other parameter constant effeiciency of the system decreases. why is it so?

for example 1st i designed for 14-20V input volt and 5V, 3.5A output rating for maximum efficeiency, then efficiency was higher. when i designed for 14-30V input range efficiency comes down? why is it so? can you please explore on it?

thanks in advance,

with regards,

ANkush agrawal

With all other variable constant, efficiency decreases with higher input voltage.  That is due to switching losses in the FETs.