Changes in DI-139
Hi,
I would like to use SMPS based on LNK304DN. I need two outputs: 3.3v@50ma and 12v@120ma. Those requirements are very close to a design idea you published (DI-139). What changes do I need to perform in order to adjust the outputs?
(From 3.3v@70 to 3.3@50ma, and from 12v@80ma to 12v@120ms)
Good day,
Nir
Comments
Hi Wesley,
Thank you for the quick reply.
First, please notice that there is an error in the website regarding to the components values: If you perform "parametric search" and click on the schematics of DI-139, the values of C1, C2 and L1 are mF, mF and mH, instead of uF, uF and uH.
Second, I'm considering adding Diode Bridge at the input stage of DI-139. What will be the effect on the mains influence, output ripple and general circuit performance?
Third, can you recommend (part number or spec) of L1 in DI-139?
Best regards,
Nir
Yes you are correct about the component values. It seems the greek symbols are were not correctly drawn.
If you add a bridge diode the lowest DC voltage will be greater than that with just a half wave rectifier. The RMS input current should go down a more sinusoidal AC input current waveform (since you know are keeping the input capacitors charged each half of the line cycle the peak current will be lower). This may affect EMI performance negatively. You'll have to see empirically. The overall performance of the circuit shouldn't change much.
Something like the Coilcraft RFB0807-102L would be a good choice for L1.
Hope this helps.
-Wesley
Absolutely none unless there is some aspect of the supply performance you are not happy with. This is because your load requirements are below those of the specifications and thus the supply can easily supply the current and voltage necessary.