Comments on: H-Bridge Fundamentals

By: arash

arash — Sun, 24 Jan 2010 21:45:42 +0000

hello
my friend
please help me
please send pdf or shematic file circuit driver dc motor 24 v for automatic door(left or right fasrt speed and low speed by pwm and countering rpm by shaft encoder ) by mosfet and L99H01 chip or masfet and ir 2102 chip

thank you

please send now
i am a waiting

By: genotio

genotio — Tue, 19 Jan 2010 20:47:08 +0000

Note that you can put 2 or more mosfets in paralell. Rdson will be smaller, but driver will be more loaded.

By: John Essen

John Essen — Wed, 13 Jan 2010 05:40:15 +0000

A clearly written article on this subject, it answered all my questions.
Thanks Roko

By: Martin Kynde

Martin Kynde — Sun, 13 Dec 2009 13:28:20 +0000

Hallo Roko

I think you have right. Sorry for the confusing

By: Roko

Roko — Wed, 02 Dec 2009 16:47:05 +0000

Hi Martin,

I believe you’re confusing the operation of P and N channel FETs. As the paragraph below figure 3.2 states, the P and N channel fets are activated by opposite polarities.

Thus, the interface circuit is correctly set up to provide a high signal to Q4, and a low signal to Q1 to switch them both on, while ensuring that the others are off.

By: Martin Kynde

Martin Kynde — Wed, 02 Dec 2009 11:52:48 +0000

Hallo

I am studying electronics. The interface circuit would not work! Q1 and Q4 has to work together, and Q2 and Q3, else the motor would not turn in any direction. Just swap Q1 with Q2 on figure 3.2, then it would work

By: XTL

XTL — Mon, 16 Nov 2009 11:01:17 +0000

“Turning either A or B high will cause the motor to rotate in one direction or the other. If they are both high or both low at the same time, then the motor will actively bake.”

That line really made my day.

By: Guy

Guy — Mon, 16 Nov 2009 03:35:09 +0000

So should I some how amplify the signals from the micro to the Mosfets to match that of the load?

Would that work?

By: Guy

Guy — Mon, 16 Nov 2009 03:30:01 +0000

Thanks man,

Its just a small area of confusion.

By: Roko

Roko — Sat, 14 Nov 2009 19:08:49 +0000

Hi Guy,

You are correct that by itself a 5 volt MCU would have trouble switching a 12v bridge. To get around this, a mosfet driver should be used to translate the low current 5v signal to a higher current signal capable of sourcing 12v to the fets.

I briefly mention this on page 4, but when I get a chance I’ll elaborate upon this in the article. Thanks for the note!