VIPER17 STMicroelectronics, VIPER17 Datasheet - Page 25

• Manufacturer Part Number: VIPER17
• Description: VIPerPlus family: fixed frequancy high performance off line high voltage converter
• Manufacturer: STMicroelectronics

VIPER17
7.13
2
The VIPER17 is protected against short circuit of the secondary rectifier, short circuit on the
secondary winding or a hard-saturation of fly-back transformer. Such as anomalous
condition is invoked when the drain current exceed the threshold I
page 7
To distinguish a real malfunction from a disturbance (e.g. induced during ESD tests) a
“warning state” is entered after the first signal trip. If in the subsequent switching cycle the
signal is not tripped, a temporary disturbance is assumed and the protection logic will be
reset in its idle state; otherwise if the I
switching cycles a real malfunction is assumed and the power MOSFET is turned OFF.
The shutdown condition is latched as long as the device is supplied. While it is disabled, no
energy is transferred from the auxiliary winding; hence the voltage on the V
decays till the V
The start up HV current generator is still off, until V
V
and the converter switching restarts if the V
the device enters in auto-restart mode. This behavioral results in a low-frequency
intermittent operation (Hiccup-mode operation), with very low stress on the power circuit.
See the timing diagram of
Figure 32. Hiccup-mode OCP: timing diagram
DD(RESTART)
V
nd
DD
(RESTART)
I
V
DRAIN
level overcurrent protection and hiccup mode
V
V
Vcc
DRAIN
V
).
DD
DD
I
DMAX
DD
on
off
. After this condition the V
DD
under voltage threshold (V
Secondary diode is shorted here
Secondary diode is shorted here
Figure 32
Doc ID 14419 Rev 7
.
DMAX
DD
capacitor is charged again by 600 µA current,
DDon
threshold is exceeded for two consecutive
DDoff
occurs. If the fault condition is not removed
), which clears the latch.
DD
voltage goes below its restart voltage,
DMAX
Operation descriptions
(see
DD
Table 8 on
capacitor
25/31
t
t
t
t
t
t