AN1539 STMicroelectronics, AN1539 Datasheet - Page 13

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

3.2 SHORT CIRCUIT BEHAVIOUR
Short circuit protection is provided on any output by means of winding coupling for higher voltage outputs
and by means of an auxiliary circuit for 2.5V and 5V outputs (Q1 and Q3 and Figure 3). In the first case
the power supply works in hiccup mode while in the second case the output power is limited driving the
COMP pin through the optocoupler. In Figure 10 drain and V
short-circuited at V
power supply works only for some ms. In Figure 11 start-up voltages are shown under short circuit
condition on 22V output at V
Figure 10: Short circuit at Pout
Figure 11: Short circuit at Pout
in
=110V
ac
in
=110V
and V
max
max
on 22V output (V
on 22V output (V
in
ac
=220V
and V
ac
in
. In both cases the power dissipation is limited since the
=220V
in
in
ac
=110V
=110V
.
ac
ac
DD
and V
and V
voltages are shown as the 22V output is
AN1539 - APPLICATION NOTE
in
in
=265V
=220V
ac
ac
)
)
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