LM25184-Q1: Selection of switching frequency

Unnimaya V

Part Number: LM25184-Q1
Other Parts Discussed in Thread: LM25184

Hi Expert,

What will be the switching frequency selection criteria?. We have three 12V loads of following power ratings 1W,1W,1,3W with input voltage 9-16V .Is there any specific criteria for selecting the frequency for magnetics.
Could you please suggest the suitable frequency for good efficiency as well as power density?

Thanks and regards
Unnimaya.V

8 months ago

0 Gui He 8 months ago

TI__Genius 17675 points

I will check and get back later.

Thanks and best regards.

0 Gui He 8 months ago

TI__Genius 17675 points

The LM25184 operates under variable-frequency, and it goes through three possible modes of operation as stated in Figure 7-2 in datasheet. The frequency range is 12kHz to 350kHz.

I would recommend using the calculation tool (please see attachment, which you can also find on ti.com) as a start .

4064.LM(2)518x PSR flyback converter quickstart tool revA2.xlsx

Thanks and best regards.

0 Unnimaya V 8 months ago in reply to Gui He

Prodigy 140 points

Hi Gui,

Thanks for the response.

Thanks for the recommendation and Iam already using this TI calculation tool.
In the above example while operating at V_min the frequency will be 260kHz and rest of the V_Nom and V_Max voltages frequency will be 350kHz. So I would like to know at what frequency the magnetics should design 260kHz or 350kHz?

Thanks and Regards
Unnimaya.V

0 Gui He 8 months ago in reply to Unnimaya V

TI__Genius 17675 points

Hi Unnimaya

What spec of magnetic do you want to design using the fsw? The Lm and turns ratio can be obtained using the calculation too. If you want to check the Bmax, The worst condition will be the Vinmin, under which the ipk is maximum.Bmax=(Lm*ipk)/(Nps*Ae) , where Nps is the turns ratio=Np:Ns, Ae is the effective core area.

BR.

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LM25184-Q1: Selection of switching frequency