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续流用的，开关和电感同时作用，
( y, {9 W' T/ \0 T! O" q& LWith the PFET on, the input supply charges COUT and1 k" l0 f8 Q. q- F: }
supplies current to the load via the series path through the0 a! W5 F# m2 N$ C) h0 j
PFET and the inductor. Current through the Inductor ramps
' J& \; m3 S$ P! @7 X7 S& S( h% @up linearly and the output voltage increases. As the FB voltage
6 A+ Z! y3 m, O1 H3 v9 [reaches the upper threshold, which is the internal reference
# i8 V$ [ M( C3 t/ [" o5 i- L E7 wvoltage plus 10mV, the output of the comparator7 W3 p9 @! z# q& X% y
changes from low to high, and the PGATE responds by turning
8 H9 _; U3 X2 g' b! dthe PFET off. As the PFET turns off, the inductor voltage
I. v! l: X9 W" Y* ireverses, the catch diode turns on, and the current through
% h& D( I8 e; Q p0 z2 G$ I qthe inductor ramps down. Then, as the output voltage reaches
6 { M# R. ?8 t$ H& U: qthe internal reference voltage again, the next cycle starts |
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发表于 2011-6-10 10:08
