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Parallel MOSFETs for switching power supply.

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Full Member level 2
Jun 3, 2010
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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?

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.


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?

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.......

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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