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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Power Integrations may make changes to its products at any time. Power Integrations has no liability arising from your use of any information, device or circuit
described herein nor does it convey any license under its patent rights or the rights of others. POWER INTEGRATIONS MAKES NO WARRANTIES HEREIN AND
SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATIONS, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS. The products and applications illustrated herein (including circuits external to the
products and transformer construction) may be covered by one or more U.S. and foreign patents or potentially by pending U.S. and foreign patent applications
assigned to Power Integrations. A complete list of Power Integrations' patents may be found at www.powerint.com.
The PI logo, TOPSwitch, TinySwitch, LinkSwitch and EcoSmart are registered trademarks of Power Integrations. PI Expert and DPA-Switch
are trademarks of Power Integrations. Copyright 2004, Power Integrations
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