DI-25
• At zero load, maximum input voltage, the bias voltage
across C4 should be ≥8 V (12 V to 15 V under nominal
conditions).
• Good layout practices should be followed:
- LocateC5,C6andR4closetoU1withgroundsreturned
to the SOURCE pin.
OUTPUT INDUCTOR PARAMETERS
RM6ILP
Ferroxcube 3F3 material
Gap for ALG of 278 nH/T2
Core
Main: 6T, 4x26 AWG
Bias: 15T, 32 AWG
Winding Details
Bobbin
- Primary return should be connected to the DPA-Switch
tab, not the SOURCE pin.
RM6ILP 8 pin
(EPCOS B-65821-A6008-T1 or equivalent)
- Minimize the primary and secondary loop areas to
reduce parasitic leakage inductance.
Winding Order
(pin numbers)
Bias (1-2), tape,
Main Winding (7,8-5,6), tape
• Consult AN-31 for additional design tips and information.
• Choose C17 to provide adequate gate charge to Q2 at low
line (typically 5 V) and to limit Q2 gate to a safe voltage at
high line (typically less than 20 V).
Inductance
8 µH ±10%
Table 2. Output Inductor Construction Information.
100
90
TRANSFORMER PARAMETERS
EFD20 Ungapped
Ferroxcube EFD20-3F3
Core
EFD20 10 pin
Bobbin
80
(B&B B-052 or equivalent)
V
V
V
= 36 VDC
= 48 VDC
= 72 VDC
IN
IN
IN
Primary: 8T + 8T, 25 AWG
Secondary: 4T, 0.002" Cu Foil
Winding Detail
70
Primary (5-3), tape,
Winding Order
Secondary (6,7-9,10), tape,
(pin numbers)
Primary (3-1), tape
60
50
Inductance
Primary: 307 µH ±25%, Leakage: 1 µH (max.)
Primary Resonant
Frequency
3 MHz (minimum)
0
5
10
15
20
25
30
Table 1. Transformer Construction Information.
Output Power (W)
Figure 2. DPA-Switch 30 W, 5 V Synchronous
Rectifier Efficiency vs. Output Power.
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PowerIntegrationsmaymakechangestoitsproductsatanytime. PowerIntegrationshasnoliabilityarisingfromyouruseofanyinformation, deviceorcircuitdescribed
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 LIMITATION, 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, DPA-Switch and EcoSmartare registered trademarks of Power Integrations. PI Expertand
PI FACTS are trademarks of Power Integrations. Copyright 2004, Power Integrations
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12/04
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