eDesignSuite Actual Vout (meaning)

[ppereira]

Posted on November 07, 2016 at 14:07

When designing as PowerConversion -> Power Supply -> AC/DC -> Isolated -> QRFlyback (so that we can control Vout ripple) - we see on EDesign Suite avalue (on the left) for the Actual VOut. The Actual Voutis a measure before or after the output rectifying diode?. Because whenwe select different diodes (on Design Refinements) the Actual Vout valuedoesn't change, so we suspect it's before the diode (between thetransformer secondary winding and the diode) and not after the outputdiode. Perhaps someone can clarify that for us. Thanks in advance.

#actual #vout #edesignsuite

[Patrizia BELLITTO]

Posted on November 07, 2016 at 17:30

Hello,

I suppose you are using the HVLED001 device inside the available QR flyback AC/DC converters.

The actual output voltage shown on the left is calculated according the ZCD circuitry, and the value depends by the IC VrefPsr, Rzcd, Rzcd_su, Rfb and the transformer turn ratios.

So it is completely independent by the selected diode.

For further information, please check this application note:

http://www.st.com/content/ccc/resource/technical/document/application_note/fa/3e/8f/7e/1a/3d/44/c7/DM00189143.pdf/files/DM00189143.pdf/jcr:content/translations/en.DM00189143.pdf

Best regards,

Patrizia Bellitto

eDesignSuite developers team

[ppereira]

Posted on November 07, 2016 at 19:13

Hi There Patrizia,

Thanks for your reply. You are correct - we are using HVLED001. If actual Vout only depends on the IC VrefPsr, Rzcd, Rzcd_su, Rfb and the transformer turn ratios, that means that if we need a stable 25V (3% ripple) on the load, our actual Vout has to be:

25V + Vdrop (on schottky diode - let's assume 0.6V) = 25,6V. Correct?

[Patrizia BELLITTO]

Posted on November 08, 2016 at 09:34

Hello Pedro,

HVLED001 and HVLED001A have an internal structure (ST patented), that recognizes the output voltage so to exclude the diode voltage drop.

Then the actual Vout is exactly the value calculated through the ZCD network with PSR, and not Vout + Vf as in other designs.

Best regards,

Patrizia 

[ppereira]

Posted on November 08, 2016 at 11:31

Hi There Patrizia,

Thanks for the help, but it really seems odd how the HVLED001 can ''sense'' if we use a 0,3V Vf Diode or a 1V Vf Diode on the output stage, since it hasn't any components ''sensing'' the load output, only the auxiliary winding. We will trust your judgement and info and design our power source considering that the actual Vout is Vout (on the load - after the diode).

Once again thanks for the help.