VIPER15 STMicroelectronics, VIPER15 Datasheet - Page 26

• Manufacturer Part Number: VIPER15
• Description: VIPerPlus family: quasi-resonant high performance off line high voltage converter
• Manufacturer: STMicroelectronics

Operation description
7.11
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Figure 32. ZCD pin typical external configuration
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
The ZCD pin has to be connected to the auxiliary winding through the diode D
resistors R
the voltage V
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
Equation 5
SEC
.
OVP
ZCD
and R
Figure 32
exceeds, four consecutive times, the reference voltage V
) the overvoltage protection will stop the power MOSFET and the
ZCD
LIM
. The sampled signal, if higher than V
during the OFF time of the power MOSFET. This is the time when
as shows the
k
, the resistors divider ratio k
OVP
=
Doc ID 15455 Rev 5
-------------------------------------------------------------------------------------------------- -
N
--------------
N
AUX
SEC
⋅
Figure 32 on page 26
(
V
OUTOVP
STROBE
V
OVP
+
V
DSEC
OVP
, see the
) V
will be given by:
–
OVP
. When, during the OFF time,
DAUX
, trigger the internal OVP
Table 8 on page 8
OVP
OVP
(reported on
ZCD
and
VIPER15
and the
AUX
is
/