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, 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 09/06

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

Table 1. Transformer Design Parameters.

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

Elimination of the optocoupler and Y1 capacitor allowed the

necessary printed circuit board (PCB) clearance and creepage

to be obtained to withstand a 10 kV surge. The use of triple

insulated wire for the secondary winding that terminates onto

the PCB as flying leads (J4 & J5) allows the necessary creepage

from primary to secondary. Figure 2 shows the PCB layout.

Key Design Points

• Verify maximum drain voltage is <650 V at high

line, maximum overload. For EMI repeatability, the

transformer must be manufactured consistently. This is

especially important in designs with no Y-capacitor.

• Using a fast diode for D1 improves EMI.

• Make sure the PCB layout provides 10 mm clearance

and 15 mm creepage distance (use a slot in the PCB to

increase creepage distance).

• Provide a path for surge discharge currents to go around

sensitive electronic components (see spark gap (B) in

Figure 2).

• To prevent arcing, keep the PCB surfaces clean. Remove

flux and any other contaminants.

TRANSFORMER PARAMETERS

Core Material

EE16, gap for A

2

Bobbin

4+4 pin horizontal

Winding Details

Bias/Shield: 29T, 2

× 37 AWG

Primary: 176T, 37 AWG

Shield: 15T, 2

×32 AWG

Secondary: 17T, 30 AWG TIW

Winding Order

(pin numbers)

Bias/Shield (3-4), tape, primary

(2-1), tape, shield (NC-1), tape,

7.7 V (FL-FL), tape

Inductance

Primary: 3.5 mH ±10%

Leakage: 105

µH (max)

Primary Resonant

Frequency

250 kHz (min)

Figure 3. Typical Output Characteristics.

Figure 2. PCB Layout – Extended Clearance and Creepage

Provided by Slot (A). Spark Gap Provided to Route High

Currents Back to Input and Around Electronics (B).

0

0.2

0.1

0.3

0.4

0.5

0.6

0.7

Output Current (A)

12

10

8

6

4

0

2

85 VAC

265 VAC