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续流用的，开关和电感同时作用，! |6 Z3 V$ z& W2 S7 u0 x
With the PFET on, the input supply charges COUT and
# x0 E3 r+ t1 ]7 ]3 ysupplies current to the load via the series path through the
+ o8 F; U, h0 b4 XPFET and the inductor. Current through the Inductor ramps9 K8 h; J# i/ @3 x) e' c, o+ h
up linearly and the output voltage increases. As the FB voltage
6 w, i' O+ s0 yreaches the upper threshold, which is the internal reference
, v0 l& a) w: h5 R% L2 o5 Q- Y% t( X; ?voltage plus 10mV, the output of the comparator
: |/ c- W' L% A- Achanges from low to high, and the PGATE responds by turning% r5 L: n$ n0 I+ E" U
the PFET off. As the PFET turns off, the inductor voltage) T# M+ x' [" [0 M1 o
reverses, the catch diode turns on, and the current through! t6 l- n1 {" a7 c; q/ Z( Y6 [1 I
the inductor ramps down. Then, as the output voltage reaches2 {/ A, i3 a5 I4 Y$ r, c
the internal reference voltage again, the next cycle starts |
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发表于 2011-6-10 10:08
