How to create spiral traces for embedded planar transformer in Altium

Thread Starter

SiCEngineer

Joined May 22, 2019
299
On page 8 of this document https://www.ti.com/lit/ug/tidub83/t...349&ref_url=https%3A%2F%2Fwww.google.co.uk%2F

The planar transformer can be constructed with spiral traces in Altium. Does this require some kind of add on which someone can pass me into the right direction for? Any other documents that focus primarily on the step by step creation of a plane transformer focusing on the actual PCB design rather than the transformer design? I am quite comfortable with the physics of the transformer itself but not sure where to start with the PCB design.
 

prepka

Joined Oct 5, 2020
7
On page 8 of this document https://www.ti.com/lit/ug/tidub83/tidub83.pdf?ts=1607194268349&ref_url=https%3A%2F%2Fwww.google.co.uk%2F

The planar transformer can be constructed with spiral traces in Altium. Does this require some kind of add on which someone can pass me into the right direction for? Any other documents that focus primarily on the step by step creation of a plane transformer focusing on the actual PCB design rather than the transformer design? I am quite comfortable with the physics of the transformer itself but not sure where to start with the PCB design.
The only way I know to do this is to create the spiral with multiple arc traces of increasing
or decreasing radius. Not sure if there is a function in Altium for this spiral but that is how to do it in Protel its predecessor.. You may need to change the settings to allow for 1 mil points and to adjust spacing between traces to and trace width for current density and have correct dielectric between turns. Good luck
 

ronsimpson

Joined Oct 7, 2019
1,125
Do not know how but: In Eagle CAD years ago.......
Set the grid to match the lines/cm (inch) you need in the transformer.
Draw just the straight horizontal lines (not the corners).
Draw just the straight vertical lines.
Set "draw rounded lines". Connect the H and V lines. Eagle will do nice rounded corners.
1609113414959.png
Select the transformer area and set line to line spacing to some thing small and set the line width to fill up the rest of the area.
----------------------
In another CAD (not to be named) I can not do rounded corners in copper but I can do it in silkscreen. "graphics mode" Then I can move objects from one layer to another. I moved the circles to a copper layer and it worked.
 

Thread Starter

SiCEngineer

Joined May 22, 2019
299
Do not know how but: In Eagle CAD years ago.......
Set the grid to match the lines/cm (inch) you need in the transformer.
Draw just the straight horizontal lines (not the corners).
Draw just the straight vertical lines.
Set "draw rounded lines". Connect the H and V lines. Eagle will do nice rounded corners.
View attachment 226051
Select the transformer area and set line to line spacing to some thing small and set the line width to fill up the rest of the area.
Interesting, do you recommend always setting line width to fill the area rather than sizing it for current carrying capacity? Is there any effect on D.C. or AC resistance if they are set too thick? I also see people often set the width of traces so that it is just above the skin depth of the trace at operation frequency.

Bit of side question - As you know my work is high voltage. Although the transformers only generate 600V. Is there any special requirement for the spacing between the traces? Is there a risk of arc-over from trace to trace? I’ve seen some high voltage transformers generating over 10kV with only 0.5mm spacing between the traces...
 

ronsimpson

Joined Oct 7, 2019
1,125
Somewhere on the internet there are calculators to get volts/mm spacing. Most of my transformers have 1V/turn or maybe 5V/turn so turn to turn spacing is not a problem. Also inter layers have better spacing. I left extra spacing on the edges. Lets say you have 600V from one end to the other end of the winding and 10 layers you will have 60V/layer and at some point 600V from copper to the core. I want to allow for the core to touch the PCB and have spacing. (at 1000V the core is conductive)

I have not done high voltage on a planar transformer because I think it is best for high current and low voltage.

My best transformer, I put all the primary turns in a 4 layer board with the IC & MOSFETs. The secondary(s) were made on two boards, one on top and one on bottom of the main board. Also 4 layer. So I had 4p+4s+4p=12 layers. The secondary diodes are on the secondary boards so no AC leaves the transformer. Pins go through all the PCBs to connect the traces.

I have only one turn/layer. The traces must be about 0.5" wide. High current. People told me there will be eddy current problems but it run cool. The core was a little hot but I knew that.
 
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