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续流用的，开关和电感同时作用，
9 F: X) @! q6 x: kWith the PFET on, the input supply charges COUT and
' q# B+ p7 X' e* [- `supplies current to the load via the series path through the
6 M' x; S1 m3 N. `/ W9 N4 l2 X+ \4 bPFET and the inductor. Current through the Inductor ramps
3 p6 `( D3 A0 [1 l ]up linearly and the output voltage increases. As the FB voltage3 p% ~7 g6 C& J+ B) W7 ^+ Z+ O; y; a
reaches the upper threshold, which is the internal reference
8 v- f2 w+ q' r, I6 C+ v% c6 Uvoltage plus 10mV, the output of the comparator
. c1 M" _4 ?/ Ichanges from low to high, and the PGATE responds by turning" m3 l* p9 M& P0 c, k( V
the PFET off. As the PFET turns off, the inductor voltage. g" ? J+ z3 _& d9 ?
reverses, the catch diode turns on, and the current through
0 _5 n) X1 k5 `the inductor ramps down. Then, as the output voltage reaches
$ b, e7 R4 {- {, l/ Othe internal reference voltage again, the next cycle starts |
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发表于 2011-6-10 10:08
