Application circuit description

AN2252

12/21

The basic parameters of the power transformer's ferrite core selected from VOGT's ferrite

materials and shapes are shown in Table 3. The gap size was optimized to meet the current

and inductance requirements necessary to provide the nominal output power over the whole

input voltage range.

An overview of the major parameters for each winding can be found in Table 4. Because of

the discontinuous conduction flyback, the winding current has only an AC component, and

so care was taken of minimizing the eddy current loss. For this reason the primary and

secondary windings are made of Litz wire.

As was already mentioned, the ESBT requires a proportional base drive to operate. This

function is provided by current transformer T2. The basic parameters of the current

transformer's ferrite core selected from VOGT's ferrite materials and shapes are given in

Table 5. The physical appearance, dimensions and winding arrangement of the current

transformer are shown in Figure 7.

Figure 7.

Current transformer dimensions and winding arrangement

Table 3.

Power transformer core parameters

Shape

ETD39

Material

Mf 198

132

Table 4.

Power transformer winding parameters

Order

Start Pin

End Pin

No. of

turns

Wire diameter

[mm]

Wire material

Inductance [H]

1

1

2

78

4 × 0.2

CuLL

2

9

16

8

20 × 0.2

CuLL

3

2

4

78

4 × 0.2

CuLL

4

10

15

8

20 × 0.2

CuLL

5

7

8

5

0.2

CuLL