# Precaution and Rules to Paralleling Power MOSFETs

I'm going to use a Full Bridge Inverter for my application.

The problem is that the current which flows through the MOSFETs when they are ON can reach 70A RMS and the power dissipation is too high. In fact using a IPW65R019C7 MOSFET (home page, datasheet) one obtains:

Pd = Rdson*Ieff^2 = 0.019*50^2 = 47.5 W

I would like to reduce this power loss by using two MOSFETs in parallel. In this way the current is divided by 2 and one obtains:

Pd = Rdson*Ieff^2 = 0.019*25^2 = 11.8 W

The question is: Are these calculations correct? Do you know the rules and precautions to ensure that the current flows half in one MOSFET and half in the other one?

I thought to use an L6491 (home page, datasheet) as a MOSFET driver. Can I use just one MOSFET driver to drive both of them or do I need one driver for each MOSFET?

Thank you.

• How fast must you switch these MOSFETS, to respect the Safe Operating Area self-destruction region? Regarding current sharing, can you afford to insert 10 milliOhms in each Source pin? That would be 20 squares of copper foil, at room temperature. – analogsystemsrf Sep 5 '18 at 11:38
• @analogsystemsrf power MOS have (large) positive temperature coefficient on rds(on), it easily doubles over operating temperature range. No need for extra resistance – carloc Sep 5 '18 at 12:59
• I'm going to work at 100kHz. – Fabio Sep 5 '18 at 13:27
• There are various documents that you can find if you google "paralleling MOSFET". – Long Pham Sep 5 '18 at 14:41
• @Fabio: "I would like to reduce this power losses making two MOSFETs in parallel. In this way the current is divided by 2 and one obtain ..=11.8 W." Note that what you have calculated is the power dissipation per transistor. I.e. total power dissipation is still 23.6W, because you have now 2 transistors. – Curd Sep 5 '18 at 15:01