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. POWER INTEGRATIONS MAKES NO WARRANTY 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 (transformer construction and circuits external to the products) 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. Power Integrations grants its

customers a license under certain patent rights as set forth at http://www.powerint.com/ip.htm.

The PI logo,

TOPSwitch, TinySwitch,LinkSwitch, DPA-Switch,PeakSwitch,EcoSmart,

Clampless,

E-Shield,Filterfuse,StackFET,PI ExpertandPI FACTS are trademarks of Power

Integrations, Inc. Other trademarks are property of their respective companies. ©2007, Power Integrations, Inc.

For the latest updates, visit

www.powerint.com

Rev. A 02/07

Power Integrations

5245 Hellyer Avenue

San Jose, CA 95138

Phone: 1-408-414-9200

Apps: 1-408-414-9660

Apps Fax: 1-408-414-9760

For a complete listing of worldwide

sales offices, please visit

www.powerint.com

Key Design Points

• WindT1forthelowestleakageinductancebychoosing

wiregaugesizesthatcompletelyfilleachwindinglayer.

• ThePIXlsspreadsheettoolcanbeusedtomodifythis

supplytoallowoperationovertheuniversalACinput

voltagerange(85–265VAC).

Table 2. Transformer Construction Information.

Table 1. Output Cross Regulation at 265 VAC.

TRANSFORMER PARAMETERS

Core Material

EE16

NC-2H or Equivalent, gapped

for A

2

Bobbin

EE16, 8 pin

Winding Details

Primary: 200T, 36 AWG, tape

Secondary 5 V:, 11T, 29 AWG

triple insulated, tape

Secondary 18 V: 26T, 30 AWG

triple insulated, tape

Primary

Inductance

2.77 mH ±10%

Primary

Resonant

Frequency

500 kHz (minimum)

Leakage

Inductance

111

mH (maximum)

Figure 2. No-Load Input Power vs. Line Voltage.

Figure 3. Efficiency vs. Input Voltage at Full Load.

Loading

5 V Output

18 V Output

100% on 5 V and

100% on 18 V

4.94

18.14

100% on 5 V and

10% on 18 V

5.01

19.46

10% on 5 V and

100% on 18 V

5.08

17.99

10% on 5 V and

10% on 18 V

5.14

18.51

185

205

245

225

265

Input Voltage (VAC)

130

120

110

100

80

90

70

185

205

245

225

265

Input Voltage (V)

73

Full Load

72

71

70

• SelectthevaluesofR3andR4sothatwhenthe

5Voutputisinregulation,thereis1.63VontheFB

pin,withacurrentof49mAflowingintotheFBpin.

HigherohmicvaluesforR3andR4willnotimprove

efficiencyandmaydegraderegulationaccuracy.

• FeedbackresistorR4mustbeconnectedbeforethe

LCpost(L1andC6)filterinordertoavoidgroups

ofenabledanddisabledswitchingcyclesfrom

occurring.