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Parallel MOSFETs for switching power supply.

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BlackHelicopter

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Is it typically bad practice to run multiple MOSFETs in parallel to handle the load current of a switching power supply? Are there any tricks to performing this safely?
 

andre_teprom

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Due to production scale factor, a sigle Power Mosfet is much more expensive than a set of minor size ones in a set array.
That´s one of the higher reason to be very common that configuration.

Other point, is that just one device, have more complex heatsink requirements , due dissipated energy will be concentrated, generating higher thermal gradient profile.

+++
 

BradtheRad

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Paralleling of mosfets and transistors is feasible. You should use identical part numbers of course.

Advice says to put a current matching resistor in series with each mosfet. Otherwise one mosfet could hog the most current, due to mismatched characteristics.

Typically the resistances only need to be a fraction of an ohm. Unfortunately this wastes a certain amount of power.

However here's a webpage where someone says he tests mosfets in parallel to find which ones match. This eliminates the need for current matching resistors.

Simple rig to match mosfets?
 

ea.arun

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some designs which directs a marginal heatrsinks uses parallel MOSFETs.......along with the stratic conditions(like RDSon) it is also mandatory to validate the switching characteristics because paralleling mosfets can increase the parasitic capacitance.......
 

boldstone

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You cannot parallel MOSFET except isolate them by a very low resistor to prevent of multi voltage at single point. Due to each part has a tolerance with other one (even if they have same P#).
 

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