Datasheet

NCP1010, NCP1011, NCP1012, NCP1013, NCP1014
http://onsemi.com
12
Figure 18. A more detailed view of the NCP101X offers better insight on how to
properly wire an auxiliary winding.
Startup S ource
Drain
+
--
--
+
VCC
ON
=8.5V
VCC
OFF
=7.5V
+
V
CC
Rlimit
+
--
+
I > 7.4m
(Typ.)
+ +
CVcc Caux
Laux
Ground
+
Vclamp = 8.7 V typ.
Permanent
Latch
D1
Figure 19. The burst frequency becomes so low that it is difficult to keep
an adequate level on the auxiliary V
CC
...
>30 ms
Lowering the Standby Power with Skip--Cycle
Skip--cycle offers an efficient way to r educe the standby
power by skipping unwanted cycles at light loads.
However, the recurr ent frequency in skip often enters the
audible range and a high peak cur rent obviously generates
acousticnoisein the transfor mer. The noisetakesits origins
in the resonance of the transformer mechanical structure
which is excited by the skipping pulses. A possible
solution, successfully implementedinthe NCP1200 series,
also author izes skip--cycle but only when the power
demand has dropped below a given level. At this time, the
peak current is reduced and no noise can be heard.
Figure 20 pictures the peak current evolution of the
NCP101X entering standby.