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lnk3024- Output issue

Posted by: Ankeet Gugale on

Hello,

we have used LNK3024 chip into our custom board to get 12V output from universal input(85 to 265V), but due to the size constrain we could not replicate the same circuit given in datasheet.
Attached is the circuit which we have used for which we are getting 3.8V output.
Please suggest how to get 12V output using the current circuit which we have used.

Files

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LNK-302-304.PNG 8.83 KB

Comments

Submitted by PI-Traveler on 11/21/2017

Hi Ankeet Gugale,

Thank you for choosing Power Integrations.

You are getting 3.8 V because the feedback pin resistors R10 and R11 are set to give that output. You have to calculate the resistors such that at 12V ouptut there is 2.0 V on the FB pin. I suggest that you use Power Integrations' design tool to determine your needed resistors. It will also calculate the buck inductor depending on your required output current.

You can find the design too here : https://ac-dc.power.com/design-support/pi-expert/

Some other comments on your schematic:

1. Locate the varistor after the fuse for safety
2. If you cannot use a pi-filter move the inductor L6 to a location between input rectifier and input capacitor. This will prevent the LNK3024 from getting damaged during switching.