www.powerint.com

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11/02

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Table 1. Transformer Construction Information.

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

higher efficiency than an RCD clamp, maximizing available

output power for the Blue Angel 5 W input power limit.

A secondary shunt regulator (U3) together with R6, R7, R9,

R10 and R11 are used to sense both the 3.3 V and 5 V outputs.

Control loop compensation is accomplished with capacitor

C7, R5 and C5. Resistor R6 sets the DC gain while R7

provides bias to the TL431 (U3). The values shown provided

satisfactory phase margin and bandwidth.

Key Design Points

• Decoupling capacitor (C1) should be used if the standby

supply is far from the main input bulk capacitor.

• The value of R1 is set according to the equation:

R1 = (V

•Minimize secondary trace leakage inductance to improve

output cross regulation.

• Y1 capacitor (CY1) should be connected between secondary

return and primary positive DC rail to minimize potential

coupling into the TOPSwitch-GX SOURCE pin during

common mode line surge events.

• Connect bias winding return past SOURCE pin to route

common mode surge currents away from TOPSwitch-GX.

•A soft-finish capacitor (C8) eliminates output start-up

overshoot.

• Capacitor C2 should be located close to U1.

TRANSFORMER PARAMETERS

Core Material

EEL19 (Nippon Ceramic NC-2H)

A

2

Bobbin

EEL19 8 pin

(TDK BE-9-118CPH or equivalent)

Winding Details

Primary: 147T x 34 AWG

Bias: 17T x 34 AWG

3.3 V: 4T x 3 x 27 AWG T.I.W.

5.0 V: 2T x 3 x 27 AWG T.I.W.

(T.I.W. = Triple Insulated Wire)

Inductance

Primary: 2.3 mH ±10%,

Leakage: 75 µH (maximum)

Primary Resonant Frequency

650 kHz (minimum)

Winding Order

(Pin Numbers)

Primary (1-2), tape,

3.3 V (7, 8-6), 5 V (5-7, 8), tape

Bias (3-4), tape

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 (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, Inc.

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