Refugee's modification is completely wrong. He does not understand the operation of this cicruit.
Acutally, if 改成虚线所示, the current sensor no longer monitors or detects Ids of Mp power transistor and of course fails. Originally schematic is correct although it is quite simple and not that much accurate. However, for PWM/PFM transition, the threshold varition +/-20% is acceptable. If used in Current Mode DC-DC, this circuit is not good enough.
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发表于 2009-3-25 10:35:39
