AN1539 STMicroelectronics, AN1539 Datasheet - Page 4

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

Figure 2: Transformer pin out
The design of the transformer windings has been done according to (1). Once the primary inductance
value and turns ratio N
per-turn value, can be calculated. Then, all the other turn values are given by (2).
WHERE
related to the k
adjust the related output voltage.
1.2 OUTPUT RECTIFIER DIODES SELECTION
The selection of the output rectifier diodes has been done considering reverse voltage and forward
current rating, as defined in (3) and (4).
(Cu SIDE)
V
D
is the diode forward voltage drop, i.e. 0.7V for PN diodes and 0.4V for Schottky diodes, k is
th
output. Either kind of diodes, fast recovery PN or Schottky barrier, are used in order to
p
/N
1.3
10
V
I
OL
k
k
±0.1
, between primary and lowest voltage output, is selected, V
max
max
2
V
V
1
N
Ok
t
Ok
I
Ok
11
D
V
max
7 6
12
max
OL
V
V
13
N
Ok
DC
OL
14
V
V
max
4
4
t
15
D
±0.1
V
3
16
D
2
17
N
N
Ok
p
32
AN1539 - APPLICATION NOTE
20
±0.1
t
parameter, volt-
(3)
(1)
(2)
(4)
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