STMicroelectronics Double output SMPS for power line application using ALTAIR04-900 primary controller EVLALTAIR900-M1 EVLALTAIR900-M1 Ficha De Dados
Códigos do produto
EVLALTAIR900-M1
Application information
ALTAIR04-900
20/29
Doc ID 18211 Rev 2
5.9
Hiccup mode OCP
The device is also protected against short circuit of the secondary rectifier, short circuit on
the secondary winding or a hard-saturated flyback transformer. A comparator monitors
continuously the voltage on the R
the secondary winding or a hard-saturated flyback transformer. A comparator monitors
continuously the voltage on the R
SENSE
and activates a protection circuitry if this voltage
exceeds 1 V.
To distinguish an actual malfunction from a disturbance (e.g. induced during ESD tests), the
first time the comparator is tripped the protection circuit enters a “warning state”. If in the
subsequent switching cycle the comparator is not tripped, a temporary disturbance is
assumed and the protection logic will be reset in its idle state; if the comparator is tripped
again a real malfunction is assumed and the device is stopped.
first time the comparator is tripped the protection circuit enters a “warning state”. If in the
subsequent switching cycle the comparator is not tripped, a temporary disturbance is
assumed and the protection logic will be reset in its idle state; if the comparator is tripped
again a real malfunction is assumed and the device is stopped.
This condition is latched as long as the device is supplied. While it is disabled, however, no
energy is coming from the self-supply circuit; hence the voltage on the V
energy is coming from the self-supply circuit; hence the voltage on the V
CC
capacitor decays
and cross the UVLO threshold after some time, which clears the latch. The internal start-up
generator is still off, then the V
generator is still off, then the V
CC
voltage still needs to go below its restart voltage before the
V
CC
capacitor is charged again and the device restarted. Ultimately, this results in a low-
frequency intermittent operation (Hiccup-mode operation), with very low stress on the power
circuit. This special condition is illustrated in the timing diagram of
circuit. This special condition is illustrated in the timing diagram of
Figure 18.
Hiccup-mode OCP: timing diagram
V
DS
Vcc
ON
Vcc
OF F
Vcc
rest
Secondary diode is shorted here
t
t
t
V
SOU RCE
1 V
Two switching cycles
V
CC
Vcs
dis