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DI-78

A

11/04

Power Integrations

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Table 1. Transformer Design Parameters.

Figure 3. V-I Output Characteristic.

Figure 2. Conducted EMI Plot, 230 VAC Input, Maximum Load and

Output Return Connected to Artificial Hand Input of LISN.

TRANSFORMER PARAMETERS

Core Material

EP10 (TDK PC40), gapped for

A

2

Bobbin

EP10 Horizontal, 8-pin

Winding Details

Shield 1: 23T, 38 AWG x 2, tape,

Primary: 129T, 38 AWG, tape,

Shield 2: 10T, 31 AWG x 2, tape,

Secondary: 11T, 32 AWG triple

insulated, tape

Primary

Inductance

900 µH ±5%

Primary Resonant

Frequency

900 kHz (minimum)

Leakage

Inductance

70 µH (maximum)

Figure 4. No-Load Input Power vs. Line Voltage.

Key Design Points

• Diode D5 should be a glass passivated type to guarantee a

specified recovery time and should be used with R2 fitted

to limit reverse pull-out current.

• Select the value of C1 and C2 to meet differential line surge

withstand requirements.

1.0

0.15

10.0

70.0

-20

-10

0

10

20

30

40

50

60

80

70

MHz

QP

AV

Average

Quasi Peak

3

4

5

6

Output Current (mA)

0

1

2

160

80

0

400

320

240

Low Limit

High Limit

85 VAC

265 VAC

150

125

200

225

250

175

Input Voltage (VAC)

0

50

25

100

75

150

100

50

0

300

250

200

• Select the initial value of R9 using: R9 = V

adjustments may be made by changing the value of R8.

• Use an optocoupler with a high CTR (300% to 600%) to

improve CC linearity and variability.

• For VR1 select a Zener series with a low test current.

• Inductor L2 and C7 are typically not required for battery

loads.