NCP1015 ON Semiconductor, NCP1015 Datasheet - Page 11

• Manufacturer Part Number: NCP1015
• Description: Self-supplied Monolithic Switcher For Low Standby-power Offline Smps W/out Ovp
• Manufacturer: 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 which is
Skip cycle offers an efficient way to reduce the standby
Figure 17. A Detailed View of the NCP1015 with Properly Connected Auxiliary Winding
Figure 18. The Burst Frequency becomes So Low that it is Difficult to
V
V
CC(off)
CC(on)
= 8.5 V
= 7.5 V
Keep an Adequate Level on the Auxiliary V
+
+
+
-
-
+
u30 ms
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NCP1015
11
Startup Source
Ground
excited by the skipping pulses. A possible solution,
successfully implemented in the NCP1200 series, also
authorizes skip cycle but only when the power demand as
dropped below a given level. At this time, the peak current
is reduced and no noise can be heard. Figure 19 shows the
peak current evolution of the NCP1015 entering standby:
V
CC
Drain
+
CVCC
Rlimit
CC
+
CAux
D1
Laux