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续流用的，开关和电感同时作用，/ k+ }3 Z2 }8 |$ t
With the PFET on, the input supply charges COUT and
9 z Y7 R L1 g! S/ U) k- a6 ssupplies current to the load via the series path through the
# V$ a7 g1 x' w4 l+ VPFET and the inductor. Current through the Inductor ramps
" q- `8 q/ W" Y, i4 Yup linearly and the output voltage increases. As the FB voltage
* O- Z- ~7 k4 C- H) M% mreaches the upper threshold, which is the internal reference! Z/ U6 W" x9 u! F; j* H0 x* z
voltage plus 10mV, the output of the comparator
a$ I5 U! d5 z7 ^& d5 Dchanges from low to high, and the PGATE responds by turning
( F4 S; t) U% Athe PFET off. As the PFET turns off, the inductor voltage
/ f1 N3 ?0 N) a% t4 qreverses, the catch diode turns on, and the current through) e# v) p3 J4 Q
the inductor ramps down. Then, as the output voltage reaches
, m3 d: m( W7 X1 |$ [8 u3 Kthe internal reference voltage again, the next cycle starts |
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发表于 2011-6-10 10:08
