
NCL30001
a fault event. Figure 50 shows double hiccup mode
operation. A soft ? start sequence is initiated the second time
V CC reaches V CC(on) . If the controller is latched upon
reaching V CC(on) , the controller stays in hiccup mode.
During this mode, V CC never drops below V CC(reset) , the
controller logic reset level. This prevents latched faults to be
cleared unless power to the controller is completely
removed (i.e. unplugging the supply from the AC line).
V CC
V CC(on)
V CC(off)
t
DRV
t
Fault Timer
(internal)
Overload
applied
t
t OVLD
Figure 50. V CC Double Hiccup Operation with a Fault Occurring while the Startup Circuit is Disabled
An internal supervisory circuit monitors the V CC voltage
to prevent the controller from dissipating excessive power
if the V CC pin is accidentally grounded. A lower level
current source (I inhibit ) charges C CC from 0 V to V inhibit ,
typically 0.85 V. Once V CC exceeds V inhibit , the startup
current source is enabled. This behavior is illustrated in
Figure 51. This slightly increases the total time to charge
V CC , but it is generally not noticeable.
Figure 51. Startup Current at Various V CC Levels
The rectified ac line voltage is provided to the power stage
to achieve accurate PFC. Filtering the rectified ac line
voltage with a large bulk capacitor distorts the PFC in a
single stage PFC converter. A peak charger is needed to bias
the HV pin as shown in Figure 52. Otherwise, the HV pin
follows the ac line and the startup circuit is disabled every
time the ac line voltage approaches 0 V. The V CC capacitor
is sized to bias the controller during power up.
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