DER-50
Set Top Box Design using TOP245R
April 20, 2005
7.5 Transformer Construction
Bobbin Preparation Place 3mm of Margin tape on each side of the EF25 Bobbin.
Fix the bifilar item [3] to PIN 2. Wind 16 bifilar turns from left to right
covering a single full layer. Finish winding at PIN 1. Unwrap the other end
of the winding from PIN 2 and leave that end inside.
1 layer of item [6] for mechanical fixing.
Core Shield
Tape
Start at Pin 3. Wind 30 turns of item [3] in approximately 1 layer from
right to left. Bring finish lead back to start. Finish on Pin 2.
1 layer of item [6] for basic insulation.
Starting at Pin 4, wind 9 bifilar turns of item [3] from right to left. Spread
turns evenly across bobbin. Finish at Pin 5.
½ Primary
Basic Insulation
Bifilar Bias Winding
Insulation
Use 3 layers of item [6] for safety insulation.
Start at Pin 8. Wind 2 turns of copper foil [4]. Bring termination wire out
onto pin 6. Continue with one further copper foil turn and finish with
termination on pin 7.
3V3 and 5V
Windings
Tape
1 layer of item [6] for mechanical fixing.
Start at Pin 10. Wind 3 turns of 2 parallel strands of item [5] from right to
left. Terminate on pin 9. Continue with 7 further turns of 2 parallel strands
of item [5]. Finish on pin 8.
18V and 23V
Windings
Start at Pin 2. Wind 30 turns of item [3] in approximately 1 layer from left
to right. Bring finish lead back to start. Finish on Pin 1.
Wrap windings with 2 layers of tape item [6].
½ Primary
Outer Wrap
Assemble and secure core halves so that the tape wrapped E core is at
the bottom of the transformer. Varnish impregnate (item [9]).
Final Assembly
Power Integrations
Tel: +1 408 414 9200 Fax: +1 408 414 9201
www.powerint.com
Page 14 of 31
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