VIPER25 STMicroelectronics, VIPER25 Datasheet - Page 28
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VIPER25
Manufacturer Part Number
VIPER25
Description
VIPerPlus family: quasi-resonant high performance off line high voltage converter
Manufacturer
STMicroelectronics
Datasheet
1.VIPER25.pdf
(40 pages)
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Operation description
7.12
7.13
28/40
Summary on ZCD pin
Referring to the
implement the following functions:
1.
2.
3.
4.
Chosen R
automatically defined.
Table 9
activate one or more functions associated to the ZCD pin.
Table 9.
Feedback and overload protection (OLP)
The feedback pin (FB) controls the PWM operation, enters the burst mode and manages the
delayed overload protection.
The thresholds V
and the high limit of the PWM operations, where the drain current is sensed trough the
integrated resistor R
the power MOSFET as soon as the sensed voltage is equal to the voltage applied to the FB
pin and trough the integrated resistors network, see the
on page 14
As shows the IC block diagram reported in
comparator there is the OCP comparator that limits the drain current as maximum to the
value I
In case of higher load the voltage V
drain current is limited to I
As soon as the voltage V
protection turns off the IC. After, the auto-restart mode is activated using the low value of the
current I
I
Dlim
Current limit, I
Line feed-forward compensation
Output overvoltage protection (OVP)
Zero current detection for QR operation
OVP and line feed-forward
set point and line feed-forward
Dlim
Function / component
I
I
Dlim
Dlim
refers to the
DDch
Line feed-forward
Line feed-forward
LIM
, reported on
.
I
set point and OVP
reduction+ OVP +
Dlim
ZCD pin configurations
, see
, R
OVP
set point
FF
Figure 32 on page 26
FBbm
Table 7 on page 7
and R
Dlim
SENSE
Figure 32
, set point
and V
Table 8 on page 8
OVP
FB
Dlim
and applied to the comparator PWM. The PWM logic turns OFF
reaches the threshold V
FBlin
as described in previous paragraphs this function are
and the internal current starts the charge of the capacitor C
Doc ID 15585 Rev 4
and list the external resistance combinations needed to
(reported on
FB
.
See
See
See
See
with R
, the circuitry connected to the ZCD pin enables to
increases, when it reaches the threshold V
Equation 4
22 kΩ
22 kΩ
Equation 4
22 kΩ
Equation 4
Equation 4
R
.
LIM
Figure 2 on page 4
FF
=
Table 8 on page 8
∞
FBolp
Required for ZCD
Required for ZCD See
Required for ZCD See
See equation 7
See equation 7
See equation 7
See equation 7
Figure 2 on page 4
, see
R
OVP
, in parallel with the PWM
Figure 36 on page
) are respectively the low
See
See
Not required
Not required
Not required
Equation 3
Equation 3
Equation 3
Equation 3
R
and
FF
Figure 20
FBlin
31, the
VIPER25
D
the
Yes
Yes
Yes
Yes
Yes
Yes
Yes
OVP
FB
.