電源技術-電源IC資料(英文)(pdf 16頁)

The NCP1215 is a controller for low power off-line flyback
Switched Mode Power Supplies (SMPS) featuring low size, weight
and cost constraints together with a good low standby power
performance. The operating principle uses switching frequency
reduction at light load by increasing the OFF Time. Also, when OFF
Time expands, the peak current is gradually reduced down to
approximately 1/4 of the maximum peak current to prevent from
exciting the transformer mechanical resonances. The risk of acoustic
noise is thus greatly diminished while keeping good standby power
performance.
A low power internal supply block also ensures very low current
consumption at start-up without hampering the standby power
performance.
A special primary current sensing technique minimizes the impact
of SMPS switching on control IC operation. The choice of peak
voltage across the current sense resistor allows dissipation to be
further reduced. The negative current sensing technique offers
advantages over a traditional approach by avoiding the voltage drop
incurred by traditional MOSFET source sensing. Thus, the IC drive
capability is greatly improved.
Finally, the bulk input ripple ensures a natural frequency dithering
which smooths the EMI signature.……
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