DPRG
DPRG List  



[DPRG] voltage multiplier for NMOS Hbridge

Subject: [DPRG] voltage multiplier for NMOS Hbridge
From: Ted Huntington thunting at uci.edu
Date: Thu Jun 26 11:48:01 CDT 2003

>
> > I think I may simply use a small 6V battery in series with my 2 12V batteries to
> > get 30V to turn on the high side of the h-bridge.  Then I do not have to worry
> > about charge multipliers on each h-bridge.
>
> When you turn on the high side of your h-bridge the gate for the high
> side will be seeing near 30 volts.  I haven't seen a MOSFET that can
> handle that without being dammaged some.

I am using the irfz48n, and I see no gate Volt maximum, no Vgd, only a Vgs max of
+-20V.  I am confusing the Vdss=55V and the Vgs max=20V, so according to the spec is
having a 0 voltage on the gate and 24V on the source out of spec?


> Do it often and it is dead.
> If it fails on then the next time you turn on the low side on that side
> of the h-bridge it also goes from shoot through.  The two FETs are now
> shorting power to ground.  They don't live long when that happens.

I am not sure a FET is ever alive, but perhaps.  Eventually with the continued
evolution and development of robots, there will robots that do every thing humans can
and more.  Then humans probably will call robots "alive".

> >>I don't know about videos but there are good books. I'd highly recommend
> >>"The Art of Electronics" by Horowitz and Hill.
>
> > I just saw this book today and am going to check it out.  I am not sure how much
> > art is involved in electronics, but some great things have crappy titles.
>
> Have you thought about the art of creativity that is needed to come of
> with new and clever designs?  Also what about the skill in putting
> together fundamental circuit blocks to solve problems?  I second the
> reccomendation of this book.  It can be a little steep for some people,
> but it is jam packed with good fundamental information.  It is a college
> level text book.
>

I simply think the word "art" is kind of abstract and has often been used to justify
fascism or is simply an abstract individual opinion.  What one person calls art, a
different person may call useless.  I do appreciate clever designs and creative ideas,
I just think that I would not call that art.

Now I am looking at hbridge drivers and here is what I have learned:
HIP4080 (full bridge driver, no shoot thru protection, supply voltage<=15v, 80v 2.5a
max] $4.95/arrow
LT1162,1160 (60v 1.5a max, has shoot thru protection, but because no charge pump have
to pulse hs) $6/arrow
IR2110 (20V max, high and low side driver, no shoot thru protection) $3/arrow
(perhaps I am reading the spec on this wrong, perhaps the 20V is how much over the
Source Voltage the chip can go?  Maybe somebody can explain this to me.  If that is
true then this chip may be a great choice.)
TD340 (full bridge driver 18v max)

The HIP4080 appears popular because it can handle higher voltages, but there is no
shoot thru.  Plus I guess I would have to use a voltage divider to bring the 24v down
to 12v for the chip, I am not sure if that is as simple as dividing with two equal
resistors or if I have to include the motor resistance (that is low <1ohm as far as I
know).

The LT1162 is a possible choice but what is this about having to pulse the high side?
That sounds like more logic, I hope that post was inaccurate.

The other two are not high enough voltage (24v) for the 24v motors I am using.  I am
not sure that I need shoot thru protection because I am pulsing DC gear motors, so the
logic will always be 00, then 01, 00 to 10 etc...1 transistor will always be off,
although I suppose the 8 bit port I use could get destroyed and have all 1's on the
motor data lines.

Are there any other MOSFET driver chips that are popular?

keep on botting!
Ted

--
Ted Huntington
Programmer Analyst I
Main Library
University of California, Irvine
PO Box 19557
Irvine, CA 92623-9557
emesgs:  thunting at uci.edu
web page:  http://business.lib.uci.edu/webpages/ted.htm
8:00a-12:00p Business Office (949) 824-8926
1:00p-5:00p  Multimedia Resource Center (949) 824-1674
"Stop violence, teach science."



More information about the DPRG mailing list