VIPER17_0810 STMICROELECTRONICS [STMicroelectronics], VIPER17_0810 Datasheet - Page 25

• Manufacturer Part Number: VIPER17_0810
• Description: Off-line high voltage converters
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

VIPER17
7.12
Figure 31. Brown-out protection: BR external setting and timing diagram
HV Input bus
Rh
Rl
BR
Brown-out protection
Brown-out protection is a not-latched shutdown function activated when a condition of mains
under voltage is detected.
The Brown-out comparator is internally referenced to V
the PWM if the voltage applied at the BR pin is below this internal reference. Under this
condition the power MOSFET is turned off. Until the Brown out condition is present, the VDD
voltage continuously oscillates between the V
the timing diagram of
noise immunity.
The switching operation is restarted as the voltage on the pin is above the reference plus the
before said voltage hysteresis. See
The Brown-out comparator is provided also with a current hysteresis, I
approach is possible to set the V
choosing the resistors of the divider connect to the BR pin.
Fixed the V
can be established for the calculation of the resistors R
Equation 9
10u
INon
0.1V
0.45V
and the V
Vcc
+
-
+
-
R
V
DD
Figure 31 on page 25
L
=
−
INoff
AC_OK Disable
V
I
BRhyst
BRhyst
levels, with reference to
VinOK
INon
+
Figure 31
threshold and V
V
INon
HV Input bus
HV Input bus
V
. A voltage hysteresis is present to improve the
−
INoff
.
Vin
Vin
V
DDon
I
Vin
Vin
BRhyst
(pin 3)
(pin 3)
VinOK
VinOK
VDS
VDS
INoff
V
Vcc
Vcc
Vout
Vout
OFF
OFF
0.45V
0.45V
15 µA
15 µA
DD
ON
ON
−
BR
V
and the UVLO thresholds, as shown in
−
BRth
INoff
V
Figure 31
BRhyst
BRth
H
and R
thresholds separately, by properly
,0.45 V typ value, and disables
×
L
I
V
BRhyst
, the following relationships
:
BRth
Operation descriptions
BRhyst
.With this
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t
t
t
t
t
t
t
t
t
t
t
t
t
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