VIPER15

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


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Page 26/40

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Operation description
Figure 32. ZCD pin typical external configuration
7.11
Overvoltage protection (OVP)
The VIPER15 has integrated the logic for the monitor of the output voltage using as input
signal the voltage V
the voltage from the auxiliary winding tracks the output voltage, through the turn ratio N
N
.
SEC
The ZCD pin has to be connected to the auxiliary winding through the diode D
resistors R
and R
OVP
the voltage V
ZCD
Table 8 on page 8
converter enters the auto-restart mode.
In order to bypass the noise after the turn off of the power MOSFET, the voltage V
sampled inside a short-window after the time T
Figure 33 on page 27
digital signal and increments the internal counter. The same counter is reset every time the
signal OVP is not triggered in one oscillator cycle.
Referring to the
Figure 32
Equation 5
26/40
during the OFF time of the power MOSFET. This is the time when
ZCD
as shows the
Figure 32 on page 26
LIM
exceeds, four consecutive times, the reference voltage V
) the overvoltage protection will stop the power MOSFET and the
STROBE
. The sampled signal, if higher than V
, the resistors divider ratio k
V
k
=
-------------------------------------------------------------------------------------------------- -
OVP
N
AUX
(
--------------
V
OUTOVP
N
SEC
Doc ID 15455 Rev 5
OVP
. When, during the OFF time,
OVP
, see the
Table 8 on page 8
, trigger the internal OVP
OVP
will be given by:
OVP
OVP
) V
+
V
DSEC
DAUX
VIPER15
/
AUX
and the
(reported on
is
ZCD
and