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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.

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complete list of Power Integrations' patents may be found at

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Rev. A 09/06

Power Integrations

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voltage via R6 and R7 and drives the optocoupler. However,

the control shifts to CC mode of operation when the voltage

across R3 exceeds the forward drop of the photo-diode in U2.

TinySwitch-III

allowsthissimpleCCsensingschemetobeused,

while still meeting active mode efficiency requirements.

Key Design Points

• Verify that the maximum drain voltage is <650 V at high

line and maximum overload condition. Adjust the values of

R1 and C4 as necessary. However, avoid making the clamp

circuit too large (ie. low value of R1 and high value of C4),

as this will increase the no-load power consumption.

• Selecting a fast diode vs. an ultra-fast diode for D5 will

improve efficiency by recovering leakage energy. If glass

passivated (1N4007GP) is unavailable a FR107 may be used.

• For consistent EMI performance in production,

manufacturing variations in transformer T1 must be

minimizedfromunittounit. Thisisespeciallyimportant

in designs that do not use a Y-capacitor.

• Placetapebetweentheprimarywindinglayerstoreduce

intra-winding capacitance. This will help reduce the

no-load consumption.

Table 1. Transformer Design Parameters.

T.I.W.: Triple Insulated Wire, NC: No Connection

TRANSFORMER PARAMETERS

Core Material

EE16, NC-2H material or equiv-

alent, gap for A

2

Bobbin

5+5 pin horizontal

Winding Details

Shield: 28T, 2

×33 AWG

Primary: 120T, 33 AWG

Shield: 8T, 2

×27 AWG

5.7 V: 10T, 25 AWG T.I.W.

Winding Order

(pin numbers)

Shield (3-NC), tape,

primary (2-1), tape,

shield (NC-3), tape,

5.7 V (10-7), tape

Inductance

Primary: 2.25 mH

±12%

Leakage: 45

µH (max)

Primary Resonant

Frequency

850 kHz (min)

Figure 2. Worst-Case Conducted EMI (Output RTN Connected

to Artificial Hand Input of LISN).

1.0

EN55022B Limits

0.15

10.0

100.0

-20

-10

0

10

20

30

40

50

60

80

70

MHz

QP

AV

0

200

100

400

300

500

700

800

600

900

Output Current (mA)

6.5

6

5.5

5

4.5

3.5

4

3

2.5

2

1.5

1

0.5

0

115 VDC

230 VDC

Low Limit

High Limit

Figure 3. Typical Output Characteristics.