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 Expert and PI FACTS are trademarks of Power

Integrations, Inc. Other trademarks are property of their respective companies. ©Copyright 2006, Power Integrations, Inc.

For the latest updates, visit

www.powerint.com

Rev. A 11/06

Power Integrations

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Phone: 1-408-414-9200

Apps: 1-408-414-9660

Apps Fax: 1-408-414-9760

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Key Design Points

• TakethevalueofinputcapacitancecalculatedbyPIExpertor

the PI Xls spreadsheet, divide it by two, and round up to the

next standard value to select the values of C15 and C16.

• UsingPIExpertorthePIXlsspreadsheet,designthesupplyfor

the maximum output power at the maximum V

• TheLM358(U1)containstwooperationalamplifiers.Ensure

that the inputs to the second amplifier (pins 5 and 6) are

connected to secondary ground.

Figure 3. Input Voltage (100 V /div) and Current (100 mA/div),

Showing the Effect of the Valley Fill Circuit.

Figure 2. Efficiency vs. Input Voltage at Different Load Levels,

Room Temperature, 50 Hz Line.

Table 1. Transformer Design Parameters.

TIW = Triple Insulated Wire, NC = No Connect, FL = Flying Lead

TRANSFORMER PARAMETERS

Core Material

PC40EF25-Z

Bobbin

EF25 Horizontal bobbin

Winding Details

Primary: 92T, 0.3 mm heavy

nyleze magnet wire

Secondary: 14T 2

× 0.4 mm

Triple Insulated Wire (TIW)

Winding Order

(pin numbers)

Primary (2-4), Secondary (6-10)

Inductance

1.6 mH

185

195

205

215

245

235

225

265

255

Input Voltage (VAC)

86

84

82

80

78

76

74

72

70

100%

75%

50%

25%