Power Sources and Supplies: World Class Designs

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Chapter 3

during a very small interval. The current can therefore overshoot the set current

limit threshold by a v

ery large amount, thereby endangering the switch. That is

why, especially when we come to off-line applications, it is actually customary to

select a core large enough to avoid saturation at the current limit threshold. And

that usually gives enough time for the current limit circuitry to act— before the

slope of the current has gone completely out of control.

Note, however, that the copper windings still only need to be proportioned to handle

the continuous current (i.e., based on the maximum operating load). ...