H-Bridge design question

[Dannyx]

Good day folks. I'm going to need to build an H-bridge to run some electric car windows (won't go into details as to WHY I need an H-bridge for that just yet, so let's just pretend it's a normal motor) and I'd like some advice on this. First off, the design: I know what H-bridges do and how they operate, but I ran into a bit of confusion when I came across this schematic.


Most other schematics show an H-bridge built out of 2 N-channel FETs and 2 P-channel FETs, however this one is all N-channels (all the arrows on the symbols are pointing inwards), so that's basically my first question: would such a thing work ? My basic electronics knowledge taught me that N-channels are dropped between the negative rail and the load, whereas P-channels are dropped between the positive rail and the load, so will those N-channels work between the load +12v as well like the schematic depicts them ? :| The transistors I'm going to use are IRF3710 only because I found 4 of them in my junk drawer (datasheet here). Also, I can't tell for sure how much power a car window motor actually draws. They have 30A fuses in the fuse box of my vehicle, so I can imagine they pull quite some amps, so I hope the 40A worst temperature scenario rating of the IRF transistors seems to cut it.

[Dannyx]

Re: H-Bridge design question

Duuh...should've read my wikis more carefully.....

[Dannyx]

Re: H-Bridge design question

Just realised that while an all-N channel H bridge does exist and can work, it's not practical at all to replicate in a car, since I'd have to drive the gates above the voltage at the drains of the high side FETs, which is already 12v (14v with the engine running) so I'd have no way of going higher than that (requires charge pumps, boost converters and just......naah). However, the N-P combination is still possible, so now I'm trying to find some good candidates for the P ones...suggestions would be great Found this IPB180P04P4L which has a low on resistance, but might be expensive...

[budm]

Re: H-Bridge design question

https://www.ametherm.com/blog/inrush...FURufgodT1QDcQ

http://www.ni.com/white-paper/14921/en/
https://www.electrical4u.com/startin...e-of-dc-motor/

[Dannyx]

Re: H-Bridge design question

https://www.ametherm.com/blog/inrush...FURufgodT1QDcQ

http://www.ni.com/white-paper/14921/en/
https://www.electrical4u.com/startin...e-of-dc-motor/

You're right, designing something like this obviously takes a LOT of math and formulas to get it right, as in perfect, industry-standard. However I'm not really into all of that (nor do I actually know any numbers about the motors installed in my car's doors), so I prefer the hands-on approach. We'll start small-scale with this one: since it's not physically possible for me to remove one of the motors from the car door to bring it to the workbench to prototype stuff (nor do I have a garage to prototype stuff IN the car either), I found a drill motor which will act as my dummy motor. Next, get a bunch of FETs, rig up the circuit and at least make sure it works to change direction. One thing I DO have is a car battery and charger so those will come in handy too. I figured the best approach is to have "excess" current in the upper limit of the transistors....sure, not AT ALL the way to go, since there are many other factors concerned, but I'll first go "junk-drawer" and THEN proceed to buying stuff

[budm]

Re: H-Bridge design question

Well it has nothing to do with hands on approach without at least knowing something about the load to be able to defy what you circuit requirement will be.
You wouldn't unknowingly hook up a 5V 100A load to your 5V 1A power supply just to do hands-on to find out what will happen, would you?
If you read the article, it has to do with inrush current.