24v upto 40Amp H bridge DC motor driver schematics

In comp.robotics.misc 40Amp wrote: : Where can I find 24v upto 40Amp H bridge DC motor driver schematics?

Google?

Google like the other chap said. Here is one

to the bottom of the page. Regards, John Crighton Sydney

That one is overly complex with poor performance, and has a fatal flaw to boot. Not recommended.

What would you recommend?

["Followup-To:" header set to sci.electronics.design.] On Wed, 29 Sep 2004 22:10:25 +1000, wrote in Msg.

I'd build one around the HIP4081A. Look at the data sheets and app notes on the Intersil website.

--Daniel

A 1kW H-bridge is not a good choice for a high-power-novice copy-the-schematic project (making no assumptions about you).

I'd begin with my favorite HIP4081A H-bridge driver IC, add some large MOSFETs, evaluate snubbers and filters, and move on to considering protection and controller schemes. Hmm, perhaps that's backward, and one should start by evaluating recent motor-controller ICs first, and move on FETs, etc.

Harris and IR probably both do drivers and app notes.

Graham

Heh. Stephen King just wrapped up a seven-book series with a polite request to readers to refrain from looking up his address and driving over for a visit to debate the merits of the ending.

For your own peace of mind, this habit you have of citing "bad" circuits without revealing their flaws may require a similar notice in the preface to AoE 3rd ed.

Just sayin', 's all.

-- jm

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Nah, folks are more than welcome to come visit me anytime at my lab and debate circuits, lift a brew, or whatever! But as for Stephen King, after stringing along as a paying customer on his online novel experiment, one delayed chapter at a time, and getting jilted unable to read the ending, I realize he has a very serious crybaby problem.

whined and crossposted to 3 groups:

and if I ever catch you cross-posting again, you go in my permanent killfile. Pick one, and post. If you get ignored, then you picked the wrong group. Be polite, or you get completely ignored.

On Wednesday 29 September 2004 03:13 pm, Winfield Hill did deign to grace us with the following:

Was Stephen King the one who did "Pet Sematery?" Or was that Spielberg?

I saw "It," and was really disappointed with that sewer clown/spider thing.

Other than that, I think the crowning moment of King's glory was the line: "I'll be dipped in shit if that ain't a meteor!"

Cheers! Rich

OK, I'll bite! I can't see the fatal flaw. Why is this circuit a poor performer?

A pal of mine up in Newcastle, is gathering parts to build this particular motor controller, so if there is anything flawed, we would like to know about it.

Is it the choice of parts that you don't like? Remember, here in Australia and NZ the parts available to choose from are limited, compared to the vast array of components available at low prices in the USA.

Getting back to that particular circuit, I thought the designer in New Zealand hand done a good job. The Fet driver circuit looks good, there is a safety interlock and over current feature. What don't you like about this controller?

Regards, John Crighton Sydney

I'm not the original poster that said to be a flaw and never came back with the flaw, but took some minutes to take a look at the circuit and saw 2 possible points of failure: the low speed diodes in the bridge and the high side driver. Both could burn the FET's. I really think it would be better to use some bootstrap from IR or some other (IR2104 comes to mind, but it may be too weak for driving mosfets with 40A). Most of the times the MOSFET internal diode is enough. IGBT can be purchased with internal diode as well. If the internal diodes aren´t enough, be sure to use high speed ones and to give dead time to the switches longer than the reverse recovery of the diode and the turnoff+fall time of the switch.

Regards, Ricardo.

The fonts used in that schematic made my eyes go funny, and double and triple lines here and there made me feel a bit drunk, also for some reason adobe seemed to take forever just to scroll acros it .. so i havnt managed to look for any flaws.

Colin =^.^=

If thats an open invitation i might be interested in taking you up on exept for the fact that ive not been wel enough to go out for the last few years, however i find im only realy interested in circuits that are on the edge of posibility, wich means i dont often produce anything that usefull, just as well its only a hobby now i gues, unless of course i managed to actualy do something that realy is (was) imposible.

I think the bad circuits idea in AoE are a good idea and not having an explanation gets ones mind working till the flaw is found, and also maybe gives you an idea of how good you are if you can find each ones flaw without any help.

Colin =^.^=

Further looking at it revealed C5 wrong way round,lower gate drive circuits could be a lot simpler with just 2 transistors each, top ones cld be done with 3 or posibly 2, overcurent should have some sort of hystereseis/time latch on it, otherwise the transistors could be switched on and off very rapidly under overcurent conditions for wich the slow antiparalel diodes used would cuase serious problems. im not sure about the wiseness of paraleling such a lot of the circuitry for more power.

As a note, reverse and forward seem to be negative logic inputs, and it might be preferable to force an all off/fualt condition if both are active.

There's more, much more.

Someone else mentioned the slow diodes in the bridge and the high side driver, but tbh i assume this isnt going to be switched at a very high rate, - or sudenly switch from forward to reverse instantly, its just so obviously not designed for it, but maybe it could use some dead time control, just in case, a few tens of microseconds at least, then the diodes would have plenty of time to recover before they were reverse biased, is obviously not designed to handle the kenetic energy of the motor being dumped back into it, so the bridge diodes just have to handle inductive turn off transient, in fact i asume the mosfet internal diodes will be able to handle that anyway, although thinking about it again the emf from the free wheeling motor might reverse bias them imediatly after the curent has droped to zero, im not sure the 0.1 uf capacitors would help much with the curents involved, but its not like its 100v or more.

The supply to the high side driver could do with being modified slightly, high transient curents flow through c8/c11 also d1/d4 wich is probably not forseen.

Apart from the choice of power transistors im not sure what else there is left to criticise perhaps it could do with an on/off switch maybe. or maybe im missing something bigger? the 100k resistors in series with the scmit trigers seem dubious, and perhaps some supply decoupling.. there doesnt seem to be any at all for the main supply.

Colin =^.^=

I'm able to spot a few things I don't like in this one as well, at a glance.

First I think the rectifier diodes across the mosfets are supposed to be schottkys, of a few amps but that can block full rail to rail voltage.

Second is the method I see used to control dead time, slowing the turn on rate of one side over the other by using different sized gate resistors. I think you'd want to have one side to switch just as fast as the other, only delayed in time. What we have here is switching like: | on one side and / on the other, so one side will be alot less efficient as well.

Perhaps this was done in a misunderstood attempt at speeding up turn off?

Those same resistors should be removed from the circuit during turn off to allow fast discharge of the gate capacitances. Easiest done with a back diode in this case, possibly better done by only using one resistor per driver, placed at the emitter of the NPN turn on transistor. That will also help with gate step induced spurrious turn on by presenting a lower impedance to the reverse miller charge, it'll have a straight path to ground through the PNP's emitter. Said PNP could also be beefed up in size over the turn on NPN transistors. The more current it can sink the better.

Last, for everyone who said something about "less transistors on the bottom" etc, I would think you'd want matched drivers for all FETS in order to preserve any delays induced?

I don't think there's much reason to double up the output mosfets, just select the right ones for the job, and it will switch that much faster for the given driver.

What else, would have been nice to look over the rest of it more but that text made my eyes bleed.

Cheers Chris