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
7.3
Power-up and soft-start up
If the input voltage rises up till the device start threshold, V
begins to grow due to the I
high voltage start up circuit. If the V
page
6) the power MOSFET starts switching and the HV current generator is turned OFF.
See
Figure 23 on page
The IC is powered by the energy stored in the capacitor on the VDD pin, C
the self-supply circuit (typically an auxiliary winding of the transformer and a steering diode)
develops a voltage high enough to sustain the operation.
C
capacitor must be sized enough to avoid fast discharge and keep the needed voltage
VDD
value higher than V
switching operation before the controller receives any energy from the auxiliary winding.
The following formula can be used for the V
Equation 1
The t
is the time needed for the steady state of the auxiliary voltage. This time is
SSaux
estimated by applicator according to the output stage configurations (transformer, output
capacitances, etc.).
During the converter start up time, the drain current limitation is progressively increased to
the maximum value. In this way the stress on the secondary diode is considerably reduced.
It also helps to prevent transformer saturation. The soft-start time lasts 8.5 ms and the
feature is implemented for every attempt of start up converter or after a fault.
Figure 18. I
current during start-up and burst mode
DD
V
V
V
V
V
V
FBbm
V
DRAIN
I
(-3 mA)
DDch
current (see
Table 7 on page
DDch
voltage reaches V
DD
16.
threshold. In fact, a too low capacitance value could terminate the
DDoff
DD
I
DDch
C
=
----------------------------------------
VDD
V
DDon
DD
DDon
DDoff
V
FB
FBolp
FBlin
I
DD
I
DD1
I
DD0
START- UP
NORMAL MODE
Doc ID 15028 Rev 4
Operation descriptions
, the V
DRAIN_START
6) coming from the internal
threshold (see
DDon
VDD
capacitor calculation:
×
t
SSaux
V
DDoff
t
V
FBbmhys
t
t
t
BURST MODE
NORMAL MODE
voltage
DD
Table 7 on
, until when
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