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续流用的，开关和电感同时作用，7 Z3 S9 `1 O) x8 B1 H
With the PFET on, the input supply charges COUT and b$ h7 R7 M; u* Y) B# t
supplies current to the load via the series path through the( M A9 Q# H. K
PFET and the inductor. Current through the Inductor ramps
8 |/ F% W! a1 t- M1 E0 k- E- F. @up linearly and the output voltage increases. As the FB voltage% S( G1 v$ @5 L& O7 w' L
reaches the upper threshold, which is the internal reference
8 m% Z- ~0 E7 ?( G* Evoltage plus 10mV, the output of the comparator
( f7 J1 h. p. P% b, zchanges from low to high, and the PGATE responds by turning8 d1 j3 ^8 S1 S# j1 G8 E, [
the PFET off. As the PFET turns off, the inductor voltage
0 Y y. M( d9 s" \2 Greverses, the catch diode turns on, and the current through% `* `/ v% n# f9 \0 T" C9 [
the inductor ramps down. Then, as the output voltage reaches) ~" L8 V4 o% q) f/ N
the internal reference voltage again, the next cycle starts |
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发表于 2011-6-10 10:08
