TPS55010: TPS55010

Hello Wojciech,

Thanks for sending your queries.

First, I assume that you use the transformer calculation shown in section 9.4.2 of the datasheet. Is it correct?

In the Flybuck converter, the energy is stored on the center leg of the transformer. Hence, an air gap is typically necessary to avoid transformer saturation. You can use the formula below to calculate the max flux density (Bmax) to determine if the transformer will not saturate at max output power (Bmax < Bsat). Bmax specs are dependent on the core type.

Best regards,

Excel

hello,
not exactly, there is no point 9.4.2 in my datasheet.
I have calculate Lpri(max) from 14 equation in 9.2.4 point.
Next, I have take from ferrite core datasheet max flux = 300mT, Effective area Ae=10,7mm2.
I take frequency about 350kHz (dt=~1,4us) and Upri=0,5*Uin (Upri=2,5V).
From equation Npri=((Uin-Upri)*dt)/(dB*Ae) i have calculated number of primary turns, necessery to avoid core saturation.
I have rounded number of turns up, then I calculate number of secondary turns. I obtain new value of primary voltage. And Its all :-).

Hello Wojciech,

I made a typo error, and it should be 9.2.4. It looks like the transformer is designed properly. Hence, an air gap might not be necessary.

By the way, you can also counter-check if there is transformer saturation by measuring the current waveform across the primary winding at full load and overload/short circuit condition. Please refer to the figure below.

Transformer waveform in saturation

Best regards,

Excel