Hello,

I am new to the field of power electronics and I have a question regarding reverse polarity protection for high current applications. Specifically, I am working on a system that controls working lights for heavy machinery, with a total current to the PCB of approximately 80A at 12V.

Currently, I am using the reverse polarity protection circuit shown in the image. It functions well up to a current of about 40A, but anything above that causes the MOSFET to become excessively hot. I have attempted to address this issue by using three MOSFETs in parallel, but unfortunately, it has not made significant improvement.

I would appreciate any guidance on whether there is a more effective method for implementing reverse polarity protection, or any suggestions on how I can enhance the current circuit to improve its performance.

Thank you,
Aleksander

 

Hello,
What mosfet are you currently using?

 

Does it need to be self-resetting?

 

Are you using a heatsink for the MOSFET(s)?

 

any suggestions on how I can enhance the current circuit to improve its performance

XPQR3004PB P_dissipation = 1.472 W @80 A
Surface mount with ability of thermal contact to heatsink.

 

I have attempted to address this issue by using three MOSFETs in parallel,

Show the schematic for that.
It should have reduced the dissipated power by a factor of 3 in each MOSFET.

 

Hello,
What mosfet are you currently using?

Hello, I am using this mosfet https://datasheet.lcsc.com/lcsc/2108150330_HUAYI-HYG015N04LS1C2_C2874970.pdf

 

Does it need to be self-resetting?

No, it is only in case if user connect wires of car battery in wrong direction

 

Are you using a heatsink for the MOSFET(s)?

Right now is only mosfet without heatsink

 

XPQR3004PB P_dissipation = 1.472 W @80 A
Surface mount with ability of thermal contact to heatsink.
View attachment 296752

This will probably work. Thank you!
Do you recommend heatsink?

 

Show the schematic for that.
It should have reduced the dissipated power by a factor of 3 in each MOSFET.

 

This will probably work. Thank you!
Do you recommend heatsink?

Of course, because w/o heatsink it can dissipate about 0.5 W only @t_ambient not more than 20°C.

 

Right now is only mosfet without heatsink

Not surprising it cooks at 40A then. The datasheet suggests the case temperature would be 100C at 106A even when the FET is "mounted on a large heatsink".

 

That shows four MOSFETs in parallel, so each should dissipate only about 1/4th that of one.
What is the MOSFET's on-resistance?

 

I will try using a MOSFET with a lower Rdson resistance (the current one has Rdson = 3mΩ), and I will also mount a heatsink on it. This should likely improve the performance.

Thank you to everyone for your help and support!