Foldback (power supply design)

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In power supply design, foldback is a function whereby a constant voltage power supply's output current is reduced under overload conditions, generally to reduce power dissipation in a load. Most power supplies employ simple current-limiting protection; foldback goes one step further by reducing the output current limit linearly as output voltage decreases.

In many power supplies, foldback current limit is also used to limit the thermal stress on its internal components. With foldback current limiting, the current limit will reduce if an over-current event happens and output voltage is pulled down by the overcurrent.

By reducing the maximum thermal dissipation of the pass device, foldback often allows a given device to pass a higher max current during non-fault conditions.

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