A
Adam Seychell
- Jan 1, 1970
- 0
Oh dear, of all the hobbies to choose from why did I decide with
electronics. I'm getting headaches from constructing a simple SMPS
transformer. It looks to me there are as many variables in transformer
design as there are in jet engines.
From all the documentaion I have read on transformers I get the
impression most design variables are based on rules of thumb or from
the engineer's past experience, which I own none of. So a few
questions to the SMPS gurus (hello Genome ).
Requirements are; power 100W, primary 200V driven by half bridge,
secondary 6V and feed to synchronous current doubler rectifier, freq.
100 kHz, and should meet isolated standards. I chose ETD29 ferrite
core. This topology uses only one secondary winding and one primary
winding.
What can I expect the ratio of total copper winding cross section area
(both primary and secondary) to the bobbin winding window area ? Does
20% sound typical for an isolated transformer?
What would be conservative value for the total power dissipation for
ETD29 transformer when not relying on forced air cooling ?
Is a core loss power density of 100 mW/cm^3 a good figure to design
for ?
How important is interleaving ? I haven't measure or tried to do any
analysis on leakage inductance, but only disadvantage I can see is
added insulation which takes up precious winding area available for
copper.
What about a copper foil shield layer between adjacent primary and
secondary windings ? Again, this takes up more available winding area,
but does it simplify common mode EMI input filtering ?
Adam
electronics. I'm getting headaches from constructing a simple SMPS
transformer. It looks to me there are as many variables in transformer
design as there are in jet engines.
From all the documentaion I have read on transformers I get the
impression most design variables are based on rules of thumb or from
the engineer's past experience, which I own none of. So a few
questions to the SMPS gurus (hello Genome ).
Requirements are; power 100W, primary 200V driven by half bridge,
secondary 6V and feed to synchronous current doubler rectifier, freq.
100 kHz, and should meet isolated standards. I chose ETD29 ferrite
core. This topology uses only one secondary winding and one primary
winding.
What can I expect the ratio of total copper winding cross section area
(both primary and secondary) to the bobbin winding window area ? Does
20% sound typical for an isolated transformer?
What would be conservative value for the total power dissipation for
ETD29 transformer when not relying on forced air cooling ?
Is a core loss power density of 100 mW/cm^3 a good figure to design
for ?
How important is interleaving ? I haven't measure or tried to do any
analysis on leakage inductance, but only disadvantage I can see is
added insulation which takes up precious winding area available for
copper.
What about a copper foil shield layer between adjacent primary and
secondary windings ? Again, this takes up more available winding area,
but does it simplify common mode EMI input filtering ?
Adam