dreed75

I need to make an H-Bridge that will be used basically as a heavy duty servo which is hooked to my microcontroller. It needs to be able to drive a motor that is about 20A @ 12V (wiper motor). I have searched for days on how to build one but I can't find one that is over 2A. I will probably have to make my own so I need some help.

I found this page to be very helpful
http://www.dprg.org/tutorials/1998-04a/
but I can't find any PNP MOSFETS that are equal to a NPN MOSFET that I find.

Does anybody know of a PNP, NPN combo that will work for me?

Thanks

falleafd

Try with IR630. I dont remember which it is, but you can search for its application notes. It may drive upto 50A motors.

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dreed75

I searched for that chip on findchips.com but it wasn't found. Also on Yahoo, there was no matches.

motion

The correct part number is IRF630N. Here's the link.

http://ec.irf.com/v6/en/US/adirect/i...ductID=IRF630N

You should also consider a lower voltage (100V) but higher current rated device (23A), the IRF540N.

http://ec.irf.com/v6/en/US/adirect/i...ductID=IRF540N

also

http://ec.irf.com/v6/en/US/adirect/ir?cmd=advFrame

International Rectifier also has half-bridge MOSFET drivers to go with these devices.

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varkeychaya

i don't know if it will serve your purpose but you could check out the hbridge at the site Robot room, you'll get resources for other circuits as well

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pkshima

I guess for that high amperage you should use a relay based H-Bridge and have controll of it with ULN2003.

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crust

No, I would not use relays. I would do as suggested and use some very high current (read low RDSon) discrete mosfets. Building an h-bridge is very straightforward. I would pick the lowest voltage you are comfortable with and then find one with sufficient current handling.

Oznog

"npn" and "pnp" is a term for bipolar. MOSFETs are called n-channel and p-channel, or PMOS/NMOS.

You would want to hook your two PWM channels to the n-channels pulling the outputs to ground. The p-channel is at 12V so the gate can't be switched directly, you will use a small MOSFET or npn to pull down the gate and a pullup pulls it back up.

PMOS is inherently lower gain and higher rds than NMOS. Not that you can't find PMOS with a lower rds than an NMOS, but in the end the biggest one PMOS you're going to find is worse than the NMOS, at least for a particular price. Go to http://www.digikey.com Seach for MOSFET, select p-channel, click "Apply Filters", then select the current you want AND, using the shift key, select every current higher than what you want.

crust

You can also build a purely NMOS h-bridge. That reduces the number of different components and for equivalent RDSon values, N channel parts are lower cost and more readily available. All of mine are NMOS only. The trick is to use a small voltage doubler circuit to raise the gate voltage to 2Vcc so that the n-channel parts at the top of the bridge turn on. You have to be running high enough voltage so that the gate is 4 to 7 or more volts beyond the voltage at the drain node. For instance, with a 12V motor, you would generate 24V which is enough for the mosfets to work. You can use any of the ICL7660 doubler circuits. Alternatively, there are special parts such as the HIP4081 (i might be wrong about the part number) that is specifically designed to interface directly to an all n-channel h-bridge.