www.powerint.com

A

7/03

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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:

+886-2-2659-4570

Fax:

+886-2-2659-4550

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 Construction Information.

Figure 2. Efficiency vs. Output Power.

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 and DPA-Switch are trademarks of Power Integrations, Inc. ©Copyright 2003, Power Integrations, Inc.

Key Design Points

• For the nominal under-voltage set point V

R1 = (V

V

• For highest efficiency designs: use continuous conduction

mode operation designed at approximately 0.4 K

minimize turns in the transformer while keeping AC flux

density (BM) < 3000 Gauss; fully fill a single layer for each

winding to minimize leakage inductance and maximize

copper fill factor; use a Schottky rectifying diode (D2) with

a low forward drop (in this case, the SL23 diode has a

V

• Resistor R3: the PIXls spreadsheet calculates the peak

current (IP) of the power supply. Resistor R3 is chosen to

set the internal current limit 10% to 15% above the calculated

IP value. This limits overload power (worst case is at high

input line).

• Set resonant frequency of post-filter (L2, C12) beyond

crossover frequency (typically 5% to 10% of switching

frequency).

• For main secondary current loop from transformer pin 8 to

diode D2 and capacitors C10, C11 and back to pin 6 of the

transformer: ensure identical path length for C10 and C11

to guarantee they equally share the ripple current.

• Due to the very tight size constraints on this power supply,

the drain voltage traces should be kept as short as possible

and where possible, shielded by surrounding them with

source potential traces. This will prevent noise coupling to

the low-voltage signal pins of the DPA-Switch.

TRANSFORMER PARAMETERS

Core Material

Bobbin

EDF-10 8 pin

(or equivalent)

Winding Order

(pin numbers)

Primary Inductance

Primary Resonant

Frequency

Leakage Inductance

EFD-10

Ferroxcube 3F3

2

1/2 Primary (1-FL), Tape, Bias

(4-3), 5 V (5-8),

Tape, 1/2 Primary (FL-2), Tape

4.7 MHz (minimum)

174 µH ± 10%

1.0 µH (minimum)

13

4

25

Pout (W)

80

79

76

78

77

75

81

82

83

85

84

36 VDC

48 VDC

72 VDC