NCP1011 ONSEMI [ON Semiconductor], NCP1011 Datasheet - Page 13

• Manufacturer Part Number: NCP1011
• Description: Self-Supplied Monolithic Switcher for Low Standby- Power Offline SMPS
• Manufacturer: ONSEMI [ON Semiconductor]

Lowering the Standby Power with Skip−Cycle
power by skipping unwanted cycles at light loads.
However, the recurrent frequency in skip often enters the
audible range and a high peak current obviously generates
acoustic noise in the transformer. The noise takes its origins
in the resonance of the transformer mechanical structure
Skip−cycle offers an efficient way to reduce the standby
Figure 18. A more detailed view of the NCP101X offers better insight on how to
Permanent
Figure 19. The burst frequency becomes so low that it is difficult to keep
Latch
NCP1010, NCP1011, NCP1012, NCP1013, NCP1014
Vclamp = 8.7 V typ.
VCC
VCC
ON
OFF
= 8.5 V
= 7.5 V
an adequate level on the auxiliary V
+
+
properly wire an auxiliary winding.
+
−
−
+
u30 ms
−
+
http://onsemi.com
+
13
I > 7.4m
(Typ.)
Startup Source
Ground
which is excited by the skipping pulses. A possible
solution, successfully implemented in the NCP1200 series,
also authorizes 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.
V
CC
Drain
+
CVcc
Rlimit
CC
. . .
+
Caux
D1
Laux