LNK304 issue

Posted by: victorcanoz on 11/30/2015

Hello,

We are experiencing some issue with LNK304. Schematic and oscilloscope screenshot of the output are attached to this post.

We are supplying the board with 100 to 230V AC. The targeted output voltage is 5.5V but we only get 150mV once per second and after the LNK restarts.

It doesn't work neither at 100V nor 230V.

We don't know where to begin. Any ideas?

Thank you for your help, kind regards

Victor

Files

Altium Schematic. Transformer starting point wrong in schematic But corrected in PCB design (42.25 KB)

Output voltage (target : 5.5V) (4.31 MB)

Comments

Hi,

R3 value in your schematic is too high, FB pin won't have enough bias current with such higher resistance.

Limit the R3 value to 2K and recaluclate the R4 value based on your output voltage.

For more information read AN-37 page 10.

https://ac-dc.power.com/sites/default/files/product-docs/an37.pdf

Regards,

PI-NANO

Hello,

We are experiencing difficulties trying to make a LinkSwitch-TN supply work. This supply is supposed to work on 230VAC and deliver 5V @ 300mA. It is caught in the Auto-restart loop, where the voltage goes up for 50msec, and then the output is off for 750msec. I have tried many things to attempt to fix this, but nothing seems to work. I will give the values according to Fig 5 in the datasheet.

RF1=10Ω; D3,D4=ACGRKM4005-HF; C4,C5=8.2µF; L2=680µH

U14=LNK306DG; C1=100nF; R3=2.00kΩ; R1=4.02kΩ; D1,D2=RFN1L6STE25; C3=10µF; L1=680µH; C2=18µF; R4=1.5kΩ

I loaded the output with 100Ω to try to help, but it didn't work. I also tried to "slow-down" things as mentioned in the AN-37 (page 10) with a 10µF capacitor across R1, and then a 33µF capacitor across R1. Always the same result - auto-Restart loop.

Please give advice.

Thanks,

Pete K.

Hi,

This is someone else's post, coupld you plese post it as a seperate question.

At what load level do you see the problem. Does it work at no load or do you have the porble at no load as well.

Your output capacitor value seems to be too low. Could you please increase the capacitor value to at leaset 100uF.

Regards,

PI-NANO