EPR-54 Datasheet, PDF (29/40 Pages) Power Integrations, Inc. – Engineering Prototype Report for EP 54 - 2.75 W Charger/Adapter Using LNK520P

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
1
1
2
2
3
1
4
1
5
1
6
1
7
1
8
4
9
1
10 1
Reference
U1
C1, C2
C3
C4
C5
C6
C7
D1-4
D5
D6A
Description (Type)
LinkSwitch
4.7 µF, 400 V (SHD Series)
4.7 µF, 380 V
1 µF, 50 V, general purpose
1000 pF, 1000 V
220 nF, 50 V
330 µF, 16 V, 117 mΩ
470 pF, 50 V
Rectifier 1 A, 600 V
Rectifier Glass Passivated
1 A, 600 V
1 A, 600 V, Fast recovery,
t_rr = 200 ns
P/N, Type
LNK520P
380VB4R7M8X11C
380VB4R7M8X11L
ECA-1HHG010
Ceramic
Ceramic
EEU-FC1C331
Ceramic
1N4005
1N4007GP
1N4937
Manufacturer
Power Integrations
Sam Young
UCC
Panasonic (or generic)
Any
Any
Panasonic
Generic
Diodes, Inc. (or generic)
Any – generic
Diodes, Inc.
(or generic)
Page 29 of 40
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