VIPER15  

Manufacturer Part Number  VIPER15 
Description  VIPerPlus family: quasiresonant high performance off line high voltage converter 
Manufacturer  STMicroelectronics 
VIPER15 datasheet 

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Operation description
7.12
Summary on ZCD pin
Referring to the
Figure 32 on page 26
implement the following functions:
1.
Current limit, I
2.
Line feedforward compensation
3.
Output overvoltage protection (OVP)
4.
Zero current detection for QR operation
Chosen R
, R
LIM
FF
automatically defined.
Table 9
refers to the
activate one or more functions associated to the ZCD pin.
Table 9.
ZCD pin configurations
Function / component
I
set point
Dlim
OVP
Line feedforward
I
set point and OVP
Dlim
OVP and line feedforward
I
set point and line feedforward
Dlim
I
reduction+ OVP +
Dlim
Line feedforward
7.13
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
, reported on
Dlim
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 autorestart mode is activated using the low value of the
current I
, see
DDch
28/40
, the circuitry connected to the ZCD pin enables to
, set point
Dlim
and R
as described in previous paragraphs this function are
OVP
Figure 32
and list the external resistance combinations needed to
R
LIM
See
Equation 4
22 kΩ
22 kΩ
See
Equation 4
with R
=
FF
22 kΩ
See
Equation 4
See
Equation 4
and V
(reported on
Table 8 on page 8
FBbm
FBlin
and applied to the comparator PWM. The PWM logic turns OFF
SENSE
Figure 2 on page 4
Table 8 on page 8
.
increases, when it reaches the threshold V
FB
and the internal current starts the charge of the capacitor C
Dlim
reaches the threshold V
FB
Table 7 on page 7
.
Doc ID 15455 Rev 5
R
R
OVP
FF
Required for ZCD
Not required
See
Equation 7
Not required
Required for ZCD See
Equation 3
∞
See
Equation 7
Not required
See
Equation 7
See
Equation 3
Required for ZCD See
Equation 3
See
Equation 7
See
Equation 3
) are respectively the low
Figure 2 on page 4
and
, in parallel with the PWM
, see
Figure 36 on page
FBolp
VIPER15
D
OVP
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Figure 20
the
FBlin
.
FB
31, the
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