l6566bh based flyback converter ground short together

[Kaleeswaran]

hi all,

     i am designing flyback converter based on the l6566bh. i have 2 outputs on the secondary side, both are separate windings (different ground potential) in transformer. can i short together for shared ground reference if isolation is not necessary.

[Peter BENSCH]

It would be best if you could add a sketch as a picture so that people can immediately recognise what you mean.

If you don't need any insulation on the secondary side, you can of course connect the GND there together.

Does it answer your question?

Regards
/Peter

[Kaleeswaran]

 can i short RTN and GND_iso(transformer has separate winding for two outputs), both are isolated from primary side.

[Peter BENSCH]

Yes, the two secondary windings can have a common GND, so you can connect GND_ISO and RTN together.

However, 15V_ISO is then also galvanically (not directly) connected to 12V, so a current can flow from 15V-ISO to 12V if there is something in between.

Regards
/Peter

[Kaleeswaran]

Dear Sir,

The 15V and 12V rails have different ground potentials (in both the transformer windings and the PCB). Can I connect these two grounds externally using a jumper or wire? Will this cause voltage fluctuations?

[Peter BENSCH]

You have not made any statement about what your connected loads look like. If there is a reason for the 15V and 12V rails to have different GND potentials, you can of course not simply connect the GND.