Switching Converters, Regulators & Controllers VIPer28 Rugged 800V Fixed freq 115 kHz

VIPER28HE

Manufacturer Part NumberVIPER28HE
DescriptionSwitching Converters, Regulators & Controllers VIPer28 Rugged 800V Fixed freq 115 kHz
ManufacturerSTMicroelectronics
VIPER28HE datasheet
 


Specifications of VIPER28HE

Output Voltage800 VOutput Current3 A
Output Power20 WInput Voltage8.5 V to 23.5 V
Switching Frequency115 KHzOperating Temperature Range- 40 C to + 150 C
Mounting StyleThrough HolePackage / CaseSDIP-10
Lead Free Status / RoHS StatusLead free / RoHS Compliant  
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VIPER28
When the feedback pin voltage reaches the threshold V
starts to charge the feedback capacitor (C
threshold, the converter is turned off and the start up phase is activated with reduced
V
FBolp
value of I
to 0.6 mA, see
DDch
During the first start up phase of the converter, after the soft-start up time, t
voltage could force the feedback pin voltage to rise up to the
off the converter itself.
To avoid this event, the appropriate feedback network has to be selected according to the
output load. More the network feedback fixes the compensation loop stability. The
on page 22
and
Figure 29
The time from the overload detection (V
(V
=
) can be set by C
V
FB
FBolp
formula:
Equation 5
In the
Figure
28, the capacitor connected to FB pin (C
as well as it needs to activate the overload protection (see equation 5).
After the start up time, t
capacitor could not be at its nominal value and the controller interprets this situation as an
overload condition. In this case, the OLP delay helps to avoid an incorrect device shut down
during the start up phase.
Owing to the above considerations, the OLP delay time must be long enough to by-pass the
initial output voltage transient and check the overload condition only when the output voltage
is in steady state. The output transient time depends from the value of the output capacitor
and from the load.
When the value of the C
ensure enough OLP delay, an alternative compensation network can be used and it is
showed in
Figure 29 on page
Using this alternative compensation network, two poles (f
introduced by the capacitors C
The capacitor C
FB
is usually used to compensate the high frequency zero due to the ESR (equivalent series
resistor) of the output capacitance of the fly-back converter.
The mathematical expressions of these poles and zero frequency, considering the scheme
in
Figure 29
are reported by the equations below:
Equation 6
) and when the feedback voltage reaches the
FB
Table 7 on page
6.
show the two different feedback networks.
=
V
FB
FBlin
value (see
Figure 28 on page 22
FB
×
T
C
=
OLP delay
FB
, during which the feedback voltage is fixed at
SS
capacitor calculated for the loop stability is too low and cannot
FB
22.
and C
and the resistor R
FB
FB1
introduces a pole (f
) at higher frequency than f
PFB
1
=
f
ZFB
⋅ π
2
C
FB
Doc ID 15028 Rev 4
Operation descriptions
an internal current generator
FBlin
, the output
SS
threshold that switches
V
FBolp
) to the device shutdown
and
Figure
29), using the
V
V
FBolp
FBlin
--------------------------------------- -
3μA
) is part of the compensation circuit
FB
, the output
V
FBlin
, f
) and one zero (f
PFB
PFB1
.
FB1
and f
ZB
PFB1
R
1
FB
1
Figure 28
) are
ZFB
. This pole
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