07-May-2004
EPR-54 – LinkSwitch 2.75 W Low Cost Charger / Adapter
11 Appendix A: EE16 Simple, No Foil, Construction
11.1 Introduction
An alternative design utilizing an EE16 transformer with simplified construction is
presented. The transformer uses integral bias and bifilar wound shields. These shields
offer effective EMI attenuation with minimum additional transformer complexity.
Reduced coupling between bias and secondary windings increases load regulation and
no-load output voltage. A secondary snubber is required to reduce high frequency EMI.
Efficiency is increased from 66% to 70%, due to a reduction in transformer primary-to-
secondary leakage inductance.
Appendix A presents schematic, bill of materials, transformer construction details and
limited performance curves (including conducted EMI).
All specification requirements are identical to those presented in Section 2. Unless
specified, the performance of this prototype is similar to those presented earlier; including
output ripple, waveforms and thermal performance.
11.2 Schematic
The alternative EE16 transformer design is pin compatible with the EP-54 printed circuit
board. Bias rectifier (D6B) and jumper (J1) are exchanged to maximize performance of
the transformer bias shield. In addition, transformer primary shield (pin 3) is tied to bulk
DC return.
Component value changes are required to filter the increased leakage spike seen on the
primary bias winding. This includes the clamp circuit (R1, C4) and primary bias circuitry
(R3, R4). Component additions include secondary snubber circuit (R5, C7) and preload
resistor (R6).
11.3 Bill of Materials
Highlighted items are changes to previous design
Item Qty
Reference Description (Type)
P/N, Type
Manufacturer
Power Integrations
Sam Young
UCC
1
2
1
2
U1
LinkSwitch
LNK520P
C1, C2
380VB4R7M8X11C
380VB4R7M8X11L
4.7 µF, 400 V (SHD Series)
4.7 µF, 380 V
3
4
5
6
7
8
9
1
1
1
1
1
4
1
C3
C4
C5
C6
C7
D1-4
D5
ECA-1HHG010
Ceramic
Panasonic (or generic)
Any
1 µF, 50 V, general purpose
1000 pF, 1000 V
220 nF, 50 V
Ceramic
Any
EEU-FC1C331
Ceramic
Panasonic
330 µF, 16 V, 117 mΩ
470 pF, 50 V
Generic
Rectifier 1 A, 600 V
Rectifier Glass Passivated
1 A, 600 V
1N4005
Diodes, Inc. (or generic)
Any – generic
1N4007GP
10
1
D6A
1 A, 600 V, Fast recovery,
trr = 200 ns
1N4937
Diodes, Inc.
(or generic)
Power Integrations
Tel: +1 408 414 9200 Fax: +1 408 414 9201
www.powerint.com
Page 29 of 40
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