VIPER16 STMicroelectronics, VIPER16 Datasheet - Page 18

• Manufacturer Part Number: VIPER16
• Description: VIPerPlus family: fixed frequency high performance off line high voltage converter
• Manufacturer: STMicroelectronics

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Open loop failure protection
In case the power supply is built in fly-back topology and the VIPer16 is supplied by an
auxiliary winding, as shown in
converter is protected against feedback loop failure or accidental disconnections of the
winding.
The following description is applicable for the schematics of
Figure 28 on page
If R
voltage, V
output through the secondary-to-auxiliary turns ratio.
As the auxiliary voltage increases up to the internal V
reported on
threshold, I
generated.
In order to distinguish an actual malfunction from a bad auxiliary winding design, both the
above conditions (drain current equal to the drain current limitation and current higher than
I
If R
voltage V
case of isolated fly-back).
Figure 27. FB pin connection for non-isolated fly-back
DDol
H
L
is opened or R
through VDD clamp) have to be verified to reveal the fault.
is opened or R
REF_FB
OUT
DDol
Table 8 on page
, will increase and so the auxiliary voltage, V
R
R
(the value is reported on
H
L
(in case of non isolated fly-back) or to the external TL voltage reference (in
V
OUT
19, respectively the non-isolated fly-back and the isolated fly-back.
L
H
is shorted, the VIPer16 works at its drain current limitation. The output
is shorted, the output voltage, V
FB
C
VDD
7) and the clamp current injected on VDD pin exceeds the latch
V
Doc ID 15232 Rev 5
REF_FB
Figure 27 on page 18
VDD
-
+
E/A
Table 8 on page
C
P
COMP
BUS
C
R
S
S
nR
V
from R
COMPL
and
DD
R
OUT
SENSE
+
-
+
-
active clamp, V
Figure 28 on page
, will be clamped to the reference
7), a fault signal is internally
AUX
Figure 27 on page 18
, which is coupled with the
PWM stop
to PWM
R
AUX
DDclamp
D
AUX
19, the
(the value is
and
V
AUX