DI-76
•
•
Output diode D4 needs a sufficient peak inverse voltage
(PIV) rating for high line withstand, requiring an ultra-
fast 200 V type (UF4003). For lower output voltages
(PIV <100 V), Schottky diodes work well and enable
improved efficiency.
The LinkSwitch PIXls spreadsheet tool included in
PI Expert™ Design Software can be used to redesign the
transformer for different output voltages.
Key Design Points
•
•
•
The value of C3 (1 µF) allows time for the output voltage
to develop at startup.
A larger R3 value will provide flatter voltage regulation if
a higher no-load voltage can be tolerated.
A lower R2 value will reduce the output voltage while
proportionally increasing the maximum output current.
20
18
TRANSFORMER PARAMETERS
TDK PC40 EE13,
Core Material
16
14
12
ALG = 199 nH/T2
Bobbin
EE13 Horizontal 8-pin
Shield 1: 55 T, #38 AWG,
1 Layer
Primary-1: 69 T, #34 AWG,
2 Layers
Primary-2: 43 T, #35 AWG,
1 Layer
Secondary: 30 T, #30 T.I.W.,
2 Layers
10
MIN
MAX
105 VDC
150 VDC
315 VDC
370 VDC
8
6
Winding Details
4
2
0
0
100
200
300
400
Load (mA)
Shield 1: (3-Float), Primary-1
(1-4), Primary-2 (4-3),
Secondary (6-5)
Winding Order
(pin numbers)
Figure 2. Output Regulation vs. Load Current Curves.
Primary
Inductance
2484 µH ±10%
Primary Resonant
Frequency
80
70
500 kHz (minimum)
70 µH (maximum)
Leakage
Inductance
105 VDC
150 VDC
315 VDC
370 VDC
60
Table 1. Transformer Design Parameters.
50
40
0
50
100 150 200 250 300
Load (mA)
Figure 3. Efficiency vs. Output Current Curves.
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SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATIONS, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
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are trademarks of Power Integrations. Copyright 2004, Power Integrations
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