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LNK606 is not workin for 6 W

Posted by: mudit Goyal on Sun, 02/12/2012

Dear sir
I am trying to make a LED driver of 6W as you have given in DER 215 using IC LNK606PG, but i only got 5W.
Input Voltage=100V DC
Input current=50mA
Output Voltage=19.20V DC
After half an hour output Voltage: 18.96V DC
Transformer Design:

Primary Turn=150
Secondary turn=50
Air gap=0.08mm

I am attaching circut diagram file and layout file . Please chec it and help me.
I have alredy sent a file for this matter.
I am using load as 6 LEDs of 1W.
Input AC voltage range is 100V to 270V rms.

When i have changed the feed back resistance from 3.9 K to 3K ,there is output voltage is 18.6V DC


Attachment Size
W6.pdf 17.39 KB
W6_LAyout.pdf 143.71 KB
LNK606.pdf 79.79 KB


Submitted by PI-Jono on Mon, 02/13/2012


1. Kindly verify the actual voltage of 6 LED string by using a DC supply.
2. Make a transformer design using the PI-spreadsheet where VO = (voltage of 6 LED string) + 2V
3. Plug the new designed transformer and use the recommended values for RUPPER_ACTUAL (R2) and RLOWER_ACTUAL (R3) from the PI-spreadsheet.
4. Measure the actual no-load voltage
5. Measure the actual output current when LED is connected.
6. If the values are not matching for the target current, use PI-spreadsheet for FINE TUNING (line 97 of the spreadsheet). Key in the actual values of the component used and actual voltage and current output.
7. Verify until desired power or output current is met by performing step 4 to 6 in determining the optimum value for R2 and R3.

Please note that CC mode is the priority in driving the LED, the no-load voltage is just a protection in case load is not connected.