Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF HTML

VIPER20B Datasheet(PDF) 12 Page - STMicroelectronics

Part No. VIPER20B
Description  SMPS PRIMARY I.C.
Download  17 Pages
Scroll/Zoom Zoom In 100% Zoom Out
Maker  STMICROELECTRONICS [STMicroelectronics]
Homepage  http://www.st.com
Logo 

VIPER20B Datasheet(HTML) 12 Page - STMicroelectronics

Zoom Inzoom in Zoom Outzoom out
 12 / 17 page
background image
consumption and also provided to the external
capacitor connected to the VDD pin. As soon as
the voltage on this pin reaches the high voltage
threshold VDDon of the UVLO logic, the device
turns into active mode and starts switching. The
start up current generator is switched off, and the
converter should normally provide the needed
current on the VDD pin through the auxiliary
winding of the transformer, as shown on figure
12.
In case of abnormal condition where the auxiliary
winding is unable to provide the low voltage
supply current to the VDD pin (i.e. short circuit on
the
output
of
the
converter), the
external
capacitor discharges itself down to the low
threshold voltage VDDoff of the UVLO logic, and
the device get back to the inactive state where
the internal circuits are in standby mode and the
start up current source is activated. The converter
enters a endless start up cycle, with a start-up
duty cycle defined by the ratio of charging current
towards discharging when the VIPer20B tries to
start. This ratio is fixed by design to 2 to 14,
which gives a 13% start up duty cycle while the
power dissipation at start up is approximately 1W,
for a 230 Vrms input voltage. This low value of
start-up duty cycle prevents the stress of the
output rectifiers and of the transformer when in
short circuit.
The external capacitor CVDD on the VDD pin must
be sized according to the time needed by the
converter to start up, when the device starts
switching. This time tSS depends on many
parameters, among which transformer design,
output
capacitors,
soft
start
feature
and
compensation network
implemented
on
the
COMP pin. The following formula can be used for
defining the minimum capacitor needed:
CVDD
>
IDD tSS
VDDhyst
where:
IDD is the consumption current on the VDD pin
when switching. Refer to specified IDD1 and IDD2
values.
tSS is the start up time of the converter when the
device begins to switch. Worst case is generally
at full load.
VDDhyst is the voltage hysteresis of the UVLO
logic. Refer to the minimum specified value.
Soft start feature can be implemented on the
COMP pin through a simple capacitor which will
be also used as the compensation network. In
this case, the regulation loop bandwidth is rather
low, because of the large value of this capacitor.
In case a large regulation loop bandwidth is
mandatory, the schematics of figure 13 can be
used. It mixes a high performance compensation
Figure 12: Behaviour of the high voltage current source at start-up
FC004 22
Ref.
UNDERVOLTAGE
LOCK OUT LOGIC
15 mA
1mA
3mA
2mA
15 mA
VDD
DRAIN
SOUR CE
VIPer
Auxilia ry prima ry
wind in g
VDD
t
VDDoff
VDDo n
Sta rt up dut y cycle ~ 10 %
CVDD
VIPer20B / VIPer20BSP
12/17


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17 


Datasheet Download



Related Electronics Part Number

Part NumberComponents DescriptionHtml ViewManufacturer
VIPER20A-ESMPS primary I.C. 1 2 3 4 5 MoreSTMicroelectronics
VIPER50SMPS PRIMARY I.C. 1 2 3 4 5 MoreSTMicroelectronics
VIPER100BSMPS PRIMARY I.C. 1 2 3 4 5 MoreSTMicroelectronics
VIPER20SMPS PRIMARY I.C. 1 2 3 4 5 MoreSTMicroelectronics
STR-F6600SMPS PRIMARY IC 1 2 3 4 Sanken electric
STR-F6612SMPS PRIMARY IC 1 2 3 4 Sanken electric
STR-A6100LOW POWER OFF-LINE SMPS PRIMARY SWITCHER 1 2 Sanken electric
VIPER12ADIPLOW POWER OFF LINE SMPS PRIMARY SWITCHER 1 2 3 4 5 MoreSTMicroelectronics
VIPER22ADIPLOW POWER OFF LINE SMPS PRIMARY SWITCHER 1 2 3 4 5 MoreSTMicroelectronics

Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ]  

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Alldatasheet API   |   Link Exchange   |   Manufacturer List
All Rights Reserved© Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn