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续流用的，开关和电感同时作用，
( H+ N1 ?1 p+ Q0 ]" i9 K: IWith the PFET on, the input supply charges COUT and
' T S @) a; W; @supplies current to the load via the series path through the
+ H% L% ~, s' t- o6 xPFET and the inductor. Current through the Inductor ramps7 v! Q) S" i( \' ^' P
up linearly and the output voltage increases. As the FB voltage* b ^8 q( a# J* r4 y$ g
reaches the upper threshold, which is the internal reference
. {( H0 Y" w: M/ k' Cvoltage plus 10mV, the output of the comparator3 {6 Q) n7 b* P% l/ t
changes from low to high, and the PGATE responds by turning& O& G' O! r7 r: }: s8 ?. j
the PFET off. As the PFET turns off, the inductor voltage* y f) {. E& ~- U ]( p7 Q
reverses, the catch diode turns on, and the current through
" S# z) x* ~1 \. Xthe inductor ramps down. Then, as the output voltage reaches
* D0 d) V$ N+ y' O$ Qthe internal reference voltage again, the next cycle starts |
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发表于 2011-6-10 10:08
