www.powerint.com

DI-76

A

7/04

Power Integrations

5245 Hellyer Avenue

San Jose, California 95138

MAIN PHONE NUMBER

APPLICATIONS HOTLINE

APPLICATIONS FAX

For a complete listing of worldwide sales offices,

+1 408-414-9200

+1 408-414-9660

+1 408-414-9760

please visit 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

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.

For the latest updates, visit

www.powerint.com

Table 1. Transformer Design Parameters.

Figure 3. Efficiency vs. Output Current Curves.

Figure 2. Output Regulation vs. Load Current Curves.

TRANSFORMER PARAMETERS

Core Material

TDK PC40 EE13,

A

2

Bobbin

EE13 Horizontal 8-pin

Winding Details

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

Winding Order

(pin numbers)

Shield 1: (3-Float), Primary-1

(1-4), Primary-2 (4-3),

Secondary (6-5)

Primary

Inductance

2484 µH ±10%

Primary Resonant

Frequency

500 kHz (minimum)

Leakage

Inductance

70 µH (maximum)

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

16

18

12

14

Load (mA)

0

2

4

6

8

10

200

100

0

300

400

MIN

MAX

105 VDC

150 VDC

315 VDC

370 VDC

70

80

Load (mA)

40

50

60

150

100

50

0

300

250

200

105 VDC

150 VDC

315 VDC

370 VDC

• 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.