Query about DAP426R

Posted by: PIMan on 11/18/2013

Can used DPA426R in Flyback Design ? The chip list that support Flyback Design specially delete DPA426R in datasheet , but PI Expert is support DPA426R , Why they are so different ? If DPA426R suit for Flyback Design , why not point out in datasheet ? And if DPA426R is not suit for Flyback Design , why PI Expert support it? OK, the true is I designed a power use PI Expert , the chip is DPA426R, 400KHz. Circult dissipation under 0.15A . DPA426R hot up over 50℃ , is this normal? How can I decrease the hot? Frequence decrease to 300KHz , or replace use DPA425R ? Have any other method?Please help my this foreigner , and forgive my poor English , Thanks.

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1. EPR-68 and EPR-71 are both reference designs for the DPA switch in a Flyback topology.

2. When you say "The chip list that support Flyback Design specially delete DPA426R in datasheet", which datasheet are you referrring to?

3. Did you use PIExpert to implement your DPA design? If yes, could you please send me your PIExpert file?

First thank you for you help . "The chip list that support Flyback Design specially delete DPA426R in datasheet", may be my expression is error , sorry . I can't upload local picture cut out from datasheet , please go to http://www.powerint.com/en/products/dpa-switch-family/dpa-switch , see the "Output Power (Watts)" table at right . And the datasheet I referred is "DPA422-426 PA-Switch™ Family" , datasheet file name is "dpa_family_datasheet" , the link is http://www.powerint.com/sites/default/files/product-docs/dpa_family_datasheet.pdf .

And I tried send my PIExpert file to you , but insert an attachment is not support . How can I send my PIExpert file to you ?

If you look at Table.1 in the DPA spredsheet (http://www.powerint.com/sites/default/files/product-docs/dpa_family_datasheet.pdf), beneath the 'flyback' section, you do not see DPA426; this is because using DPA426 in a flyback topolgy will not provide you with any additional power as compared to the smaller device (DPA425). Read note.6 beneath Table.1. Therefore, you can use DPA426 in PIExpert but will be limited to the maximum output power of the DPA425. Let me know if that helps.

Thank you , Kenobi . I may be understand , DPA426R is just stronger to DPA425R in protect , such as Current limit . I'll try DPA425R , test it will cooler or hotter . And if you will , how can I send my PIExpert file to you ?

Thank you.

PIMan,

At the bottom of the screen, after you hit 'Reply', it says 'File attachments'. You can attach your file there.

Kenobi , I already upload my PIExpert file , thanks.

Hi.

I see several potential problems in the design.

1 - The heat sink area is too big (check DEV_HSINK_AREA on "design results")

2 - You will likely not be able to fit all the windings in the transformer (As mentioned in information section)

The issue is that with such a low minimum input voltage you have a very high primary rms current (3.3A). Your conduction losses alone are (worst case) 3.31*3.31*0.43 = 4.7W (0.43 is the worst case RDSon according to the datasheet). This will make themal management very difficult if this power is not just peak power since the total losses on the mosfet include also switching losses.

If you are in the process of testing this supply pay close attention to the temperature.

HoHo ， Thank you so very much . I don't have a clue before , but now I understand more , like wake up from dreams , all is become bright and clear . Thanks again .