AN1539 STMicroelectronics, AN1539 Datasheet - Page 3

• Manufacturer Part Number: AN1539
• Description: VIPOWER: LOW COST UNIVERSAL INPUT SMPS FOR DIGITAL SET-TOP BOX BASED ON VIPER50
• Manufacturer: STMicroelectronics

out is shown in Figure 2. The reflected voltage has been set to 70V, in order to have room for leakage
inductance spike. The transformer is a slot type manufactured by OREGA. In this demo board an ETD29
core has been used, allowing further increase of the output power, but a smaller core, e.g. ETD20, is
suitable for the considered power level.
Table 2: Transformer features
Figure 1: Transformer layout
Core
Al
Primary inductance
Leakage inductance
Windings specs
Output 2.5V
Output 5V
Output 12V
Output 22V
Output 30V
Aux
DC INPUT
GROUND
DRAIN
V
CC
PRIMARY SIDE
2
4
7
6
3
ETD29
180 nH
832uH
16uH (typical)
10%
SECONDARY SIDE
12
13
17
15
11
14
16
+30V
+22V
+12V
GROUND
+5V
+2.5V
GROUND
AN1539 - APPLICATION NOTE
Thomson B2
68 turns
2 turns
4 turns
8 turns
7 turns
20 turns
9 turns
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