www.powerint.com

DI-89

A

11/05

Power Integrations

5245 Hellyer Avenue

San Jose, California 95138

MAIN PHONE NUMBER

APPLICATIONS HOTLINE

APPLICATIONS FAX

For a complete listing of worldwide sales offices,

+1 408-414-9200

+1 408-414-9660

+1 408-414-9760

please visit 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. 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, EcoSmart, Clampless, E-Shield, Filterfuse,

PI Expert and PI FACTS are trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies.

©Copyright 2005, Power Integrations, Inc.

For the latest updates, visit

www.powerint.com

Key Design Points

• The PI Xls spreadsheet calculates all of the parameters

required to specify and build transformer T1.

• Thepowertransformermusthaveatwolayerprimarywinding

to ensure that its intra-winding capacitance is sufficient for

Clampless

operation.

• The reflected output voltage (V

< 90 V (74 V) for Clampless operation.

• Since this supply has a Clampless drain node, it must be

verified that the maximum drain voltage does not exceed

650 V when the flyback voltage spike occurs.

• The primary current ripple-to-peak ratio (K

be > 1 (ensures discontinuous conduction mode operation)

to minimize conducted EMI.

• The maximum operating flux density (B

< 1500 Gauss to eliminate audible.

Figure 3. Harmonized (EPA, CEC) Active-Mode Efficiency vs.

Output Power (25, 50, 75 & 100%).

Figure 2. No-load Input Power Consumption vs. Input Voltage.

0

50

150

100

250

200

300

Input Voltage (VAC)

0.12

0.1

0.08

0.06

0.04

0.02

0

-20

-10

0

-10

20

30

40

50

60

70

80

0.15

1

10

30

Frequency (MHz)

Figure 4. Conducted EMI Scan to EN55022B Limits: Full-Load,

115 VAC, 60 Hz Input, with Artificial Hand.

0

0.5

1

2

1.5

2.5

Output Power (W)

68

66

64

62

60

58

56

54

85 VAC

115 VAC

230 VAC

265 VAC

EPA Std