LNK304 voltage drop under load

Posted by: jozo.drobilica… on 09/18/2012

Hi all.

I built a power supply from lnk304 datasheet figure 5. Here is the link to datasheet:

http://www.es.co.th/schemetic/pdf/lnk304-306.pdf

Open circuit output voltage is around 13V, but output voltage under load (220 Ohm) drops between 6-8V. I bought 5 lnk304 on ebay. They are not the same. There is a huge difference in output voltage between them. One of them gives 9V under laod while the rest of them give even less than 9V. Is that normal?

All components are as in the figure 5, except R3 which is 2k 1% instead of 2k05 1%

D2 = 1N4007GP instead of 1N4005GP

D1 = UF4007 instead of UF4005 i tried with BYV26C - no difference

L1, L2 = 1mH (11 Ohm)

Does anyone have the same problem as I do?

Please help.

Thank you

Comments

Honestly, It is hard for me to understand why the output is so low with load.

PLS double check the dummy load resistor R4, and make sure R4 is 3.3k. Another possible reason is 4007. These two diodes are very important,and datasheet specifies the reverse recovery time of these diodes. Could you PLS test the power supply with 4005?

Thanks a lot for using PI part.

Best regards

R4 is 3k3 1% resistor

D1 or D2 should I try with 4005?

I will test it with D1 = UF4005 and D2 = 1N4005GP if i manage to get them.

Thank you for your answer.

R4 is 3k3 1% resistor

D1 or D2 should I try with 4005?

I will test it with D1 = UF4005 and D2 = 1N4005GP if i manage to get them.

Thank you for your answer.