cupoftea
Advanced Member level 5
Hi,
We are doing a 48W DCDC flyback SMPS, 24 in and out, 150kHz. PQ20/16 core set.
I wound the transformer NP/NS = 10/15.
The sec was in two series "halves", (one 8, and one 7 turns) which "sandwich" the primary.
When I wound the prototypes, I just wound the three layers, and then soldered the two ends of each primary half together
,and layed this solder Joint on top of the tape which covers the "top" coil.
..However, I believe it will not be realistic to expect the production winders to do it like that. It would
be too fiddley to do on mass production basis.
Therefore, for the production spec, I will bring each of the primary "half" coils
out to a pin-pair, and do it like that.
Would you agree , this is the best course of action , ie , will be cheaper to produce like that?
We will than just have to connect the primary half coils on the PCB with a PCB trace.
_________________________--___________________________
Also, as you know, with any flyback transformer, the coils should be wound such that all the "dotted" ends are at the same side of the bobbin. This will reduce common mode noise. Why dont people bother doing this?
Also, to ease manufacture, all coils should be wound clockwise.
Clockwise is easy to understand on a vertical bobbin'd PQ20/16 core, but which way is clockwise on eg, an EFD15 bobbin.? It depends which way you hold it.
You would think there would be a "method", whereby clockwise on an EFD15 is with the way its clockwise when you hold it with bobbin axis pointing to you, and pin 1 nearest you....but many bobbins dont even have numbered pins.
________________________--_____________________________
Also, suppose you are doing a 24vin to 24vout flyback SMPS.
Suppose that the two secondary halves sandwich the primary.
Also, that the primary is wound with one single coil which
covers 2 layers.
Do you bother to put tape between the two primary layers?
(after all , its only 24v). I realise you can get "nicked" coils,
but the taping is an extra production measure, and its cheaper
to do without it.
On that note, if you do put tape between the 2 primary layers, then do you prefer to wind them
as separate coils, which subsequently get connected on the PCB, or just wind one layer, put the
spool on a mandrel, then add the tape, then do the next layer?
Obviously doing two separate coils makes it easier (and likely cheaper) to do the
taping. (that's if you bother with the taping?)
We are doing a 48W DCDC flyback SMPS, 24 in and out, 150kHz. PQ20/16 core set.
I wound the transformer NP/NS = 10/15.
The sec was in two series "halves", (one 8, and one 7 turns) which "sandwich" the primary.
When I wound the prototypes, I just wound the three layers, and then soldered the two ends of each primary half together
,and layed this solder Joint on top of the tape which covers the "top" coil.
..However, I believe it will not be realistic to expect the production winders to do it like that. It would
be too fiddley to do on mass production basis.
Therefore, for the production spec, I will bring each of the primary "half" coils
out to a pin-pair, and do it like that.
Would you agree , this is the best course of action , ie , will be cheaper to produce like that?
We will than just have to connect the primary half coils on the PCB with a PCB trace.
_________________________--___________________________
Also, as you know, with any flyback transformer, the coils should be wound such that all the "dotted" ends are at the same side of the bobbin. This will reduce common mode noise. Why dont people bother doing this?
Also, to ease manufacture, all coils should be wound clockwise.
Clockwise is easy to understand on a vertical bobbin'd PQ20/16 core, but which way is clockwise on eg, an EFD15 bobbin.? It depends which way you hold it.
You would think there would be a "method", whereby clockwise on an EFD15 is with the way its clockwise when you hold it with bobbin axis pointing to you, and pin 1 nearest you....but many bobbins dont even have numbered pins.
________________________--_____________________________
Also, suppose you are doing a 24vin to 24vout flyback SMPS.
Suppose that the two secondary halves sandwich the primary.
Also, that the primary is wound with one single coil which
covers 2 layers.
Do you bother to put tape between the two primary layers?
(after all , its only 24v). I realise you can get "nicked" coils,
but the taping is an extra production measure, and its cheaper
to do without it.
On that note, if you do put tape between the 2 primary layers, then do you prefer to wind them
as separate coils, which subsequently get connected on the PCB, or just wind one layer, put the
spool on a mandrel, then add the tape, then do the next layer?
Obviously doing two separate coils makes it easier (and likely cheaper) to do the
taping. (that's if you bother with the taping?)
Last edited:
