www.powerint.com

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9/02

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WORLD HEADQUARTERS

AMERICAS

Power Integrations, Inc.

San Jose, CA 95138 USA

Customer Service:

Phone:

+1 408-414-9665

Fax:

+1 408-414-9765

e-mail: usasales@powerint.com

CHINA

Power Integrations International

Holdings, Inc.

China

Phone:

+86-755-8367-5143

Fax:

+86-755-8377-9610

e-mail: chinasales@powerint.com

SINGAPORE

Power Integrations, Singapore

Republic of Singapore 308900

Phone:

+65-6358-2160

Fax:

+65-6358-2015

e-mail: singaporesales@powerint.com

JAPAN

Power Integrations, K.K.

Keihin-Tatemono 1st Bldg.

Japan

Phone:

+81-45-471-1021

Fax:

+81-45-471-3717

e-mail: japansales@powerint.com

EUROPE & AFRICA

Power Integrations (Europe) Ltd.

United Kingdom

Phone:

+44-1344-462-300

Fax:

+44-1344-311-732

e-mail: eurosales@powerint.com

KOREA

Power Integrations

International Holdings, Inc.

Seoul, Korea

Phone:

+82-2-782-2840

Fax:

+82-2-782-4427

e-mail: koreasales@powerint.com

TAIWAN

Power Integrations

International Holdings, Inc.

Taipei, Taiwan

Phone:

+886-2-2727-1221

Fax:

+886-2-2727-1223

e-mail: taiwansales@powerint.com

INDIA (Technical Support)

Innovatech

Bangalore, India

Phone:

+91-80-226-6023

Fax:

+91-80-228-9727

e-mail: indiasales@powerint.com

APPLICATIONS HOTLINE

APPLICATIONS FAX

World Wide +1-408-414-9660

World Wide +1-408-414-9760

Table 1. Transformer Design Parameters.

For the latest updates, visit our Web site: www.powerint.com

Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability.

Power Integrations does not assume any liability arising from the use of any device or circuit described herein, nor does it convey any

license under its patent rights or the rights of others. The products and applications illustrated herein 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 and EcoSmart are registered trademarks of Power Integrations, Inc.

PI Expert is a trademark of Power Integrations, Inc. ©Copyright 2002, Power Integrations, Inc.

and DC stacking is used to improve the regulation of 12 V,

18 V, and 30 V outputs. Ferrite bead L7 is placed in series with

the 12 V, 18 V and 30 V output windings to improve centering

and cross-regulation of these outputs.

Frequency jittering provides large EMI margins with simple

filtering. Primary soft-start minimizes component stress during

start-up and a soft-finish capacitor (C20) eliminates start-up

output overshoot.

Key Design Points

• Use K

0.4–0.6 for higher efficiency, and tighter cross-regulation.

Use V

optimum performance.

• PCB traces which carry high switching currents should be

short and wide to reduce EMI.

• Reduce leakage inductance and improve cross-regulation

by filling each winding layer across the entire width of the

bobbin.

• Resistor R14 provides a small amount of pre-load on the

33 V output to prevent peak charging due to leakage

spikes.

• R5 and C5 reduce power dissipation in VR1.

Voltage

(V)

Load

Range

(Amp)

3.3

1-3

5

1-3.2

12

0.3-0.6

30

0.01-0.03

Regulation (%)

-8

-7

-6

-5

-4

-3

-2

-1

0

1

2

3

Table 2. Worst Case Output Cross Regulation - Outputs Taken

from Minimum to Maximum Load and Line from 85 VAC

to 132 VAC.

TRANSFORMER PARAMETERS

Core Material

ERL28, Nippon ceramic

NC-2H material or equivalent,

2

Bobbin

ERL28 vertical, 14 pins,

Jinbo Industrial

JB-0039 or equivalent

Winding Details

Primary: 30T + 23T, 25 AWG

Shield: 1T, 0.6" x 0.001" Cu foil

Bias: 7T, 2 x 27 AWG

3.3 V: 2T, 0.6" x 0.005" Cu foil

5 V: 1T, 0.6" x 0.005" Cu foil

12 V: 4T, 2 x 27 AWG

18 V: 3T, 2 x 27 AWG

33 V: 6T, 27 AWG

(2 x 27 AWG = Bifilar 27 AWG)

Inductance

Primary: 356 µH,

Leakage: 11 µH (maximum)

Primary Resonant

Frequency

650 kHz (minimum)

Winding Order

(Pin Numbers)

Apply 3.2 mm tape margin to

both sides of bobbin

Primary (4-3), tape, Shield (1-NC),

tape, Bias (6-7), 3 x tape, 5 V (9-11),

3.3 V (11-10), tape, 12 V (12-8),

18 V (13-12), 33 V (14-13),

3 x tape, Primary (3-1), 3 x tape