VIPER25LN STMicroelectronics, VIPER25LN Datasheet - Page 23

• Manufacturer Part Number: VIPER25LN
• Description: IC OFFLINE CONV PWM OVP 7DIP
• Manufacturer: STMicroelectronics
• Series: VIPer™ plusr

Specifications of VIPER25LN

• Output Isolation: Isolated
• Frequency Range: 122 ~ 150kHz
• Voltage - Input: 8.5 ~ 23.5 V
• Voltage - Output: 800V
• Power (watts): 24W
• Operating Temperature: -40°C ~ 150°C
• Package / Case: 8-DIP (0.300", 7.62mm), 7 Leads
• Input Voltage: 8.5 V to 23.5 V
• Switching Frequency: 136 KHz
• Mounting Style: Through Hole
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-9074-5

VIPER25
7.8
Double blanking time
The blanking time, T
value) and the higher one is 6,3 μs (typical value). The value is linked to the voltage V
sampled during the time T
relevant
< 1V or it has the higher value if is detected V
Figure 30 on page 23
The higher value of the blanking time is normally activated during the start-up phase or in
case of output short circuit; when the output voltage of the converter is quite lower than the
regulated value. In this condition can happens that during the demagnetization of the
transformer, the V
V
higher frequency and in continuous mode. This false trigger is inhibited by the selection of
the higher value of T
During the normal operation, in steady state condition, the voltage V
demagnetization is higher than 1V and the selected T
Figure 30
Figure 30. Double T
(pin 3)
0.6V
T
ZCDTth
0.8V
Vaux
ZCD
T
ST RO BE
1V
BL ANK
A
C
F
D
0
) and the ZCD circuit can be erroneously trigged, leading the system to work at
Section 7.11 on page 26
shows the typical waveforms during the power up and the linked T
1. 5
6.3μs
ZCD
BLANK
BLANK
.
is very close to the arming and triggering thresholds (V
BLANK
STROBE
, can have two different values: the lower one is 2,5 μs (typical
when V
4
Mosfet swit ched on by the starter
F
timing diagram
OSC
0. 5
Doc ID 15585 Rev 4
lim
). The time T
defined as for the over voltage protection (see the
ZCD
is lower than 1 V.
ZCD
BLANK
> 1V, refer to
has the lower value if is detected V
BLANK
2.5μs
value is the lower one. The
Delay
Table 8 on page 8
Quasi Resonant Operation
Operation description
ZCD
during the
BLANK
ZCDAth
and
selection.
and
ZCD
23/40
t
t
t
t
t
t
t
t
ZCD
,