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A

9/03

DI-63

Table 1. Transformer Construction Information.

Figure 3. 6.0 VDC, 800 mA CV/CC Curve.

Figure 2. No-Load Input Power vs. Line Voltage.

Core Material

Bobbin

Winding Order

(pin numbers)

Primary Inductance

Primary Resonant Frequency

Leakage Inductance

TRANSFORMER PARAMETERS

EE16, TDK PC40, or equivalent

A

2

EE16, 10 pin

Core shield (1-3), tape

Primary (1-2), tape

Shield (1-floating), tape

Secondary (10-9), tape

1.25 mH ±10%

500 kHz (minimum)

35 µH (maximum)

Key Design Points

• Secondary feedback bias current and output tolerances

are minimized by using a low current part for VR1

• Primary clamp losses are minimized by keeping the

voltage reflected across the transformer (V

• Picking wire sizes that fill each winding layer produce

transformers with the lowest leakage inductance

• Putting the floating shield winding between the primary

and secondary windings reduces EMI noise

•A high gain opto-coupler (CTR = 200-400) keeps the

CC portion of the output curve more vertical

• R10 should equal the output cable resistance value

85

145

175

115

205

235

265

Input Voltage (VAC)

150

50

100

0

250

200

300

7

5

6

Output Current (A)

0

1

2

3

4

500 600 700 800

400

300

200

100

0

900

85 VAC

265 VAC

Low Limit

High Limit