Problem with output voltage LNK306
Hello, I'm having some problems with the output voltage with voltage supply I attach in this message. Using an LNK306 from 230V/50Hz to 5V, using the values choosen in the documentation can't regulate to 5V, I've got 4.6V aprox. depending on the current doesn't regulate very well, I won't have more than 100mA consumption althought is variable between 50mA and 100 mA.
Regarding the coil although in the schematic is 1500uH, I put 680uA and also tested with 1500uH.
I don't know if it is not the correct schematic for 5V, if I change the Feed Res. for 7V works better than for 5V.
Thanks in advance.
Joaquin
Comments
Hi, I comment the value of the schematic, in any case I used the recommended values.
Rfb = 3.84K
Rbias = 2K
Input filter = 2.2uF / 1000uH / 2.2uF
Diode = US1M
Output cap = 100uF
Cfb = 10uF
Diode_fb = MRA4007
Coil = I tested with 680uH and 1500uH
Output Zener = TPSMA68 (Transient diode at 6.8V, only for protection)
As I said, I don't have the correct voltage, but it's a continuous without ripple, although one thing is not going OK (I think) it that in the feedback pin I don't have a continuon 1.65V signal, it's complete noisi signal (I attack the screenshot)
Thanks for your help.
One more thing, the input voltage is OK, I've got an 300V continuous signal. With almost no ripple.
Regards.
What are the feedback resistor values you're using? Did you design this supply using PI Xls? Could you post a higher quality image of your schematic as well?
-Wesley