A 3.3V power supply with LNK3202
I want to convert the schematics of the design note DER-507 (https://ac-dc.power.com/design-support/reference-designs/design-examples/der-507-175-mw-constant-voltage-universal/) to a 3.3V power supply. As far as I understand, the only thing I need to do is to replace the voltage divider R3 and R4 to an appropriate value. I am planning to keep R3 equal to 2K and changing R4 to 1.3K. With this change, the voltage divider should give me a ratio of 0.606. This number should be sufficient since 0.606 * (5V) = 2V. Are these calculations correct? Would these changes convert the power supply in the design note to a 3.3V power supply?
Thanks!
Victor Oliveira
Comments
Thank Kryten!
Hi again (:
I've just built the power supply using the design note DER-507 and the appropriate resistor divider to have a 3V3 output voltage.
While I was using it in my project, an issue keeps happening again and again. The input resistors R1 and R2 are burning out even though I am using equivalent resistors as recommended in the design note. The part number I've chosen for R1 and R2 is ERJ-P06J221V.
I am also sending the schematics of my project for inspection. In this case, GNDA is connected to LINE. AC input is 220V/60Hz.
Do you think I need to use resistors with greater power rating?
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I created a new topic because it is a different issue.
Link: https://ac-dc.power.com/forum/low-power-design/2019/issue-emi-filter-der-507-design-note/
Hello,
Thank you for considering Power Integrations for your power supply application.
That is correct. R3 and R4 are the parameters that need to be changed in order to get a FB pin voltage of 2V at your desired operating voltage. The value of resistors that you have calculated would give you a 3.3 V operating voltage.
Best Regards,
PI-Kryten