Power supply with LinkSwitch

Posted by: ajpic on 05/06/2011

Hi,

I'm just building small power supply using LNK304 switcher and my schematics looks like below:

http://ajpic.zonk.pl/temp/sch/lnk304-ps-sch.pdf

PCB topology:

http://ajpic.zonk.pl/temp/sch/lnk304-ps-pcb.pdf

I'd like to ask if it's possible to have some stable +5V or it's too small voltage?

When I measure this voltage with no load (only 3.3k resistor) the voltmeter shows me about 5.25V (R1 = 3.9K) but when I load it with some 47R resistor the voltage drops to 4.38V (0.87V dropout).

Second test I did was with 12V on the output (R1 = 12K), and the results was following:

- no load: 12.04V
- 100R load: 11.17V (0.87V dropout)

So the dropouts are exactly the same. What should I do to have some more stable output or what I did wrong?

Best Regards,
Adam

Comments

Pls. measure the output voltage with the following loads:

1%
2%
5%
10%
20%
50%
100%

The regulation will typically show a downward slope at light load, flattening out to a very constant voltage.

Hi,

I removed standard output resistor 3.3k and did some different load measurement with 12V output, here are results:

http://ajpic.zonk.pl/temp/pdf/lnk304-load.measure.pdf

Thanks for comment,
Adam

Hi,
Can I have any comment for this topic?

Adam