VIPER15

Manufacturer Part NumberVIPER15
DescriptionVIPerPlus family: quasi-resonant high performance off line high voltage converter
ManufacturerSTMicroelectronics
VIPER15 datasheet
 


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Page 31
32
Page 32
33
Page 33
34
Page 34
35
Page 35
36
Page 36
37
Page 37
38
Page 38
39
Page 39
40
Page 40
Page 32/40

Download datasheet (2Mb)Embed
PrevNext
Operation description
7.14
Burst-mode operation at no load or very light load
When the load decrease the feedback loop reacts lowering the feedback pin voltage. If it
falls down the burst mode threshold, V
switched on. After the MOSFET stops, as a result of the feedback reaction to the energy
delivery stop, the feedback pin voltage increases and exceeding the level, V
V
, the power MOSFET starts switching again. The burst mode thresholds are
FBbmhys
reported on
Table 8
where power MOSFET is switching to period of time where power MOSFET is not switching;
this device working mode is the burst mode. The power delivered to output during switching
periods exceeds the load power demands; the excess of power is balanced from not
switching period where no power is processed. The advantage of burst mode operation is
an average switching frequency much lower then the normal operation working frequency,
up to some hundred of hertz, minimizing all frequency related losses. During the burst-mode
the drain current peak is clamped to the level, I
Figure 37. Burst mode timing diagram, light load management
V
COMP
V
+V
FBbm
FBbmhys
V
FBbm
I
DD
I
DD1
I
DD0
I
DRAIN
I
D_BM
7.15
Brown-out protection
Brown-out protection is a not-latched shutdown function activated when a condition of mains
under voltage is detected. The Brown-out comparator is internally referenced to V
threshold, see
Table 8 on page 8
is below this internal reference. Under this condition the power MOSFET is turned off. Until
the Brown out condition is present, the V
V
and the UVLO thresholds, as shown in the timing diagram of
DDon
voltage hysteresis is present to improve the noise immunity.
The switching operation is restarted as the voltage on the pin is above the reference plus the
before said voltage hysteresis. See
The Brown-out comparator is provided also with a current hysteresis, I
has to set the rectified input voltage above which the power MOSFET starts switching after
brown out event, V
switched off, V
INoff
be set separately.
32/40
, the power MOSFET is not more allowed to be
FBbm
and
Figure 37
shows this behavior. Systems alternates period of time
D_BM
Burst Mode
, and disables the PWM if the voltage applied at the BR pin
voltage continuously oscillates between the
DD
Figure 5 on page 10
, and the rectified input voltage below which the power MOSFET is
INon
. Thanks to the I
, see
Table 8 on page 8
BRhyst
Doc ID 15455 Rev 5
+
FBbm
, reported on
Table 8
.
BRth
Figure 38 on page 33
.
. The designer
BRhyst
, these two thresholds can
VIPER15
time
time
time
. A