TPS23758: Recommended transformer for 3.3V Ouptut

Hi Daniel,

PD Apps expert Diang is out of office, please expect a delay in his response. Thanks for your patience!

Regards,

Brandon

Hi Daniel,

Thanks for reaching out!

1. What is the output current?

2. What is the requirement about load regulation and output voltage accuracy? If you want to use TPS23758 and primary side regulation (PSR), the load regulation and output voltage accuracy may not be as good as secondary side regulation (SSR) (TPS23753A is recommended when using SSR).

Below are some 3.3V rated flyback converter transformers. But they may not be designed for PSR. If they are not for PSR, the load regulation and output voltage accuracy may not be very good (depending on your application requirement). 

Best regards,

Diang

Hi Diang,

It appears that those transformers you mentioned are missing a secondary output that you would need for the sync output fet.  I found HA3801 and DA2257.  Would either of those 2 work?  I am very concerned with power efficiency at around 1A output on the 3.3V rail as we don't have active cooling.

Thanks,

Dan

Hi Daniel,

Our apologies for the delay. Please give Diang some time to respond to your query.

Hi Dan,

Sorry for the late response.

You can use both of them and make the converter work. DA2257 has two outputs 5V and 3.3V. You may have one unused winding if you want to go with it. DA2257 has low inductance which makes more DCM.  HA3801 could be a better one between these two. 

My biggest concern is how well load regulation and output voltage accuracy you want to achieve? Since you want to use TPS23758 which uses PSR, which normally has worse load regulation and output voltage accuracy, especially if the flyback transformer is not designed for PSR. If you use SSR, the transformer requirements will be not as high as PSR transformer, and TPS23753A is more suitable for SSR.

Best regards,

Diang

Hi Diang,

Are there any transformers that you have validated to work with the TPS23758 for low power applications (2-4W) which give good efficiency?  If the output voltage is greater than 3.3V I can add fairly efficient buck regulators to get all the different voltages I need for my design.  I noticed the HA3801 looks like it has a fairly high leakage inductance which will probably translate to worse efficiency.

Thanks,

Dan

Hi Daniel,

Thanks for your reply. I did not have test experience with TPS23758 at 3.3V. I could find two efficiency data with TPS23753A. Among them, TPS23753AEVM-004 has a slightly better efficiency. 

TPS23753AEVM-002, POE70P-33L or 835-01045FC was used:

TPS23753AEVM-004, HA3801-BL or 835-01040FC was used:

Best regards,

Diang

Hi Diang,

Do you have a recommended transformer for the TPS23758 which improves efficiency at lower powers?  I can use an output voltage between 3.3V and 5.5V?  The output power I am looking for is 2-4W. I will be using buck regulators on the output to generate voltages my system needs so the regulation accuracy isn't too critical.

Thanks,

Dan