NCP1340_16 Datasheet, PDF (25/39 Pages) ON Semiconductor – High-Voltage Quasi-Resonant, Controller Featuring Valley Lock-Out Switching

VHV
V_{BO(start )}
V_{BO(stop )}
V_{HV(discharge )}
Timer
t_{line (removal )}
t_{line(discharge /detect )}
NCP1340
X2 Capacitor
Discharge
AC Line Unplug
AC
Timer
Starts
AC
Timer
Restarts
AC
Timer
Expires
DRV
t_{line (removal )}
t_{line (discharge )}
AC Detected
time
time
X2 Discharge
Current
I_{start 2}
I_CC
I_{CC(discharge )}
I_{CC 3}
I_{start 2}
V_CC
V_{CC (X2_reg )}
V_{CC (on )}
Device is stopped
X2 Discharge
time
t_{delay (start )}
time
time
Figure 21. Line Removal Timing with AC Reapplied
An over temperature protection block monitors the
junction temperature during the discharge process to avoid
thermal runaway, in particular during open/short pins safety
tests. Please note that the X2 discharge capability is also
active at all times, including off−mode and before the
controller actually starts to pulse (e.g. if the user unplugs the
converter during the start−up sequence).
Dedicated Fault Input
The NCP1340 includes a dedicated fault input accessible
via the Fault pin (8−pin and 9−pin versions only). The
controller can be latched by pulling up the pin above the
upper fault threshold, V_Fault(OVP) (typically 3.0 V). The
controller is disabled if the Fault pin voltage is pulled below
the lower fault threshold, V_{Fault(OTP_in)} (typically 0.4 V).
The lower threshold is normally used for detecting an
overtemperature fault. The controller operates normally
while the Fault pin voltage is maintained within the upper
and lower fault thresholds. Figure 22 shows the architecture
of the Fault input.
The Fault input signal is filtered to prevent noise from
triggering the fault detectors. Upper and lower fault detector
blanking delays, t_delay(OVP) and t_delay(OTP),are both
typically 30 ms. A fault is detected if the fault condition is
asserted for a period longer than the blanking delay.
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