NCP1010, NCP1011, NCP1012, NCP1013, NCP1014

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Figure 20. A more detailed view of the NCP101X offers better insight on how to

properly wire an auxiliary winding.

Startup Source

Drain

+

-

−

+

+

Rlimit

+

-

+

I > 7.4m

(Typ.)

+

+

CVcc

Caux

Laux

Ground

+

Vclamp = 8.7 V typ.

Permanent

Latch

D1

Figure 21. The burst frequency becomes so low that it is difficult to keep

u30 ms

Lowering the Standby Power with Skip−Cycle

Skip−cycle offers an efficient way to reduce the standby

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 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 22 pictures the peak current evolution of the

NCP101X entering standby.