High current voltage controller

[jonfarrugia]

I am working on an application that requires an analog signal (0-10VDC) from a PLC to control the voltage to a 50 amp load between (0-12VDC) respectively. You guys point me in the right direction to design a circuit like this?

 

[IanP]

If you want to source current from +12V to load – use P-channel power MOSFET (or for 50A you may connect several MOSFETs in parallel) .. see attached picture ..
The same thing, if you want to sink current from load (connected to+12V) to GND – use N-channel MOSFET (or MOSFETs connected in parallel) ..

More on this issue you can find here:
**broken link removed**


Rgds,
IanP

 

[jonfarrugia]

Very interesting read!

The document states that the gate voltage must be significantly higher then the source voltage to turn the gate completely on. The voltage of my source will be between 12 and 15 volts. My analog signal from my PLC is 0 to 10 volts. I'm thinking that I'll need some sort of op amp to amplify the analog signal from 0-10 to 0-25 approx. Am I correct?

 

[IanP]

That is correct if you try to switch positive power with N-channel MOSFET , but if you do the same with P-channel MOSFET you don’t need to boost the output from the PLC ..
All what you need to do is to use +12V to switch the P-channel MOSFET OFF, and 0V to switch the P-channel MOSFET ON ..

Rgds,
IanP

 

[jonfarrugia]

my analog signal is 0-10VDC yet my supply voltage can be as high as 15VDC. If I use the P-Channel Mosfet and have the analog signal at 10VDC will it be off? The may be a gate to source difference of 6 volts. Would that difference still allow the mosfet to be off?
I was looking on ebay for some cheap mosfets to play with but I a little uncertain what would work. There are so many to choose from! I'd like to safely control a 50amp load. I would say that a 0.5 voltage drop is ok at that current.
Can you post a link of a mosfet that would work ok in my app?

 

[IanP]

See attached picture on how you may address the issue of 10V vs. 15V ..

Take a look at this one (available from, for example, Farnell):
https://www.onlinecomponents.com/productfiles/mf-FSC/fairchild_FQA47P06.pdf

To switch 50A you may need 2 or 3 of them connected in parallel ..

Rgds,
IanP