Parallel MOSFETs for switching power supply.

[BlackHelicopter]

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_luis]

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]

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]

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]

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#).