VIPER15

Manufacturer Part NumberVIPER15
DescriptionVIPerPlus family: quasi-resonant high performance off line high voltage converter
ManufacturerSTMicroelectronics
VIPER15 datasheet
 


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VIPER15
7.8
Double blanking time
The blanking time, T
value) and the higher one is 6,3 μs (typical value). The value is linked to the voltage V
sampled during the time T
Section 7.11 on page 26
has the higher value if is detected V
page 23
.
The higher value of the blanking time is normally activated during the start-up phase or in
case of output short-circuit; when the output voltage of the converter is quite lower than the
regulated value. In this condition can happens that during the demagnetization of the
transformer, the V
V
) and the ZCD circuit can be erroneously trigged, leading the system to work at
ZCDTth
higher frequency and in continuous mode. This false trigger is inhibited by the selection of
the higher value of T
During the normal operation, in steady state condition, the voltage V
demagnetization is higher than 1V and the selected T
Figure 30
shows the typical waveforms during the power up and the linked T
Figure 30. Double T
Vaux
0
ZCD
(pin 3)
1V
0.8V
0.6V
1. 5
T
ST RO BE
A
T
BL ANK
6.3μs
C
D
F
, can have two different values: the lower one is 2,5 μs (typical
BLANK
defined as for the overvoltage protection (see the relevant
STROBE
). The time T
has the lower value if is detected V
BLANK
> 1V, refer to
ZCD
is very close to the arming and triggering thresholds (V
ZCD
when V
is lower than 1 V.
BLANK
ZCD
timing diagram
BLANK
Mosfet swit ched on by the starter
0. 5
4
F
OSC
lim
Doc ID 15455 Rev 5
Operation description
< 1V or it
ZCD
Table 8 on page 8
and
Figure 30 on
ZCDAth
during the
ZCD
value is the lower one. The
BLANK
selection.
BLANK
Quasi Resonant Operation
2.5μs
Delay
,
ZCD
and
t
t
t
t
t
t
t
t
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