Need the topology for a current to current SMPS, not voltage to voltage SMPS

That's because you work on gear that isn't really mass production oriented. I work for numerous clients who are all in very different markets. This keeps our jobs interesting. But after talking to automotive designers I'd be bored stiff if I had to do their job for more than a year.

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http://www.analogconsultants.com/
Reply to
Joerg
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Joerg, You're always pinching pennies in your designs.

In automotive designs you're pinching _tenths_ of cents... which can really tax your imagination on how to get a job done. ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

Really? A couple of million units a year isn't mass production?

Perhaps but I think you have a pretty small view of that world. However, I've been involved in many different markets at many different levels, over the years. It's a *big* field. There is no reason to do the same thing for forty years. Impossible, actually.

Reply to
krw

I dunno, Joerg. Isn't brewing sort of like watching paint dry? My desire is that you poke something and can get an almost immediate response. I obviously don't have your patience. Which is also my shortcoming.

Reply to
John S

[...]

I've done that kind of job as well. Where we had to ease resistor tolerance to 10% and for some to 20% (non-trimmed). Can be fun but it does get old.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

Oops, I probably mixed you up with someone else. I thought it was stage electronics for rock bands and stuff.

Nope. Medical devices for hospitals, low cost medical devices for consumers (over-the-counter), aircraft electronics, spacecraft stuff, chemical pump controllers, power generation, oil/gas exploration electronics, NDT, commercial automotive (trucks), and so on.

Not impossible. I met people who worked in one particular field such as engine control units for over 30 years. I'd have a hard time doing that, after being a consultant for this long.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg
[...]

For brewing one must have patience. Occasionally stuff has to just sit there for a couple of weeks, your gear must be squeaky clean and sterilized, you can't cut corners. Else you might ruin a day's worth of work in minutes. When we brewed beer back in my university days we were rather busy for a whole day and then again when it was time to bottle. But we made sure there was a crate left over from last time and that none of us had to drive that evening.

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

Yeah, I know. But, I can't sit still for a day let alone a couple of weeks. I would die from boredom. I'm just not up to it. Others see it as a challenge. It is why we are so diverse. Thanks, Momma (Nature), for that.

Reply to
John S

That was the last job. ;-) I've done a few career changes in the last 10 years. Before that, one employer, oneish (perhaps two) markets, but very different jobs every five to eight years.

You have a very small view of the automotive market. That is for sure.

ECUs have changed more than a little in 30 years. They will change drastically, again, over the next ten. Hell, you'd have a hard time showing up for work with your pants on, after being a consultant that long. ;-)

Reply to
krw

I was going to say it looked a bit like what I drew for a current boost. But I had the diode and inductor switched around.

+----+--FET--+-LLL--+ | | | | ^ C _ R I C ^ R | | | | +----+-------+------+

Something like that,

George H.

Reply to
George Herold

lt-spice crashed before I coiuld save it. when I had it start with the switch open it'd put 15GV on the capacitor

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Reply to
Jasen Betts

Thanks, George. It believe this is a standard buck switcher without the output filter capacitor.

Reply to
John S

No matter what you do, you will never get more current out of the circuit than the amount of peak current in the inductor at the moment your FET switch opens.

Reply to
John S

That's probably because your input is a current source and you waited too long to close the switch.

Reply to
John S

Bwahahahahahaha >:-} ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Reply to
Jim Thompson

[...]

5-8 years would be a bit much for me.

I see it from two view points. One is the actual product and that often doesn't look very good, both from a quality point of view and sometimes also from an engineering point of view (flickering LED backlights anyone?). Then from a people perspective and here talking to folks who actually work in that field helps. Pretty much all of them reported extreme pressure to keep NRE and R&D schedules down, which explains a lot of the quality issues. To the point I wouldn't want to work there. As a consultant maybe but niot if they'd demansd unrealistic timelines like they often do from their employees.

There are automotive electronics that work quite well, mostly in Japanese cars. In the end it boils down to the reliability ratings of the various entities in the know.

Sure, incremental change. Same in medical ultrasound which is my home turf. But ... after we built a flagship product in the late 80's and the satellite R&D location was closed afterwards I wasn't too unhappy that I could jump into consulting for the first time, and do something else.

As a consultant I get to wear shorts all summer long. When a web conference with bigshots is coming up I have a "dress shirt on duty" hanging in the lab closet :-)

--
Regards, Joerg 

http://www.analogconsultants.com/
Reply to
Joerg

Hi John, Here's the current to current buck that I drew... from upstream

formatting link
I guess I could try simulating these, if I ever get 'free' time.

George H.

Reply to
George Herold

Hi, Robert -

The thread has grown more to than I can re-read to capture all your requirements. However, here are my thoughts...

Max allowed input voltage: 100V Input current capability: 50mA Output voltage required: 5V Output current required: .8A

Rather than thinking about this as a current-to-current topology, think about how much power you can put into the topology within your constraints. You can't get more power out than your input capability and limits. But, you know that.

A normal buck switching topology will provide all this. One thing to note is that you cannot get more than 5W out if your max input voltage is limited to 100V and your (constant) current is .05A. So, you can forget the 10W requirement because of your 100V limit.

It seems to me that, using the standard buck topology, you will need to adjust your control loop (and thinking) as follows:

-Never let the input voltage get above 100V. As it approaches that limit, increase the duty cycle. This is equivalent to current limit. After all, if you are able to reduce the voltage while the current remains the same, input and output power is reduced. Note that this requires some kind of load just as in a current transformer.

-If the load is reduced, the voltage will tend to rise. Increase the duty cycle even more to hold the voltage. By increasing the duty cycle to a much higher value, you will cause the input voltage to plummet which will reduce the available input power.

What is your maximum load resistance?

-If it can be open or very high, then you need to provide another device at the input, perhaps a depletion FET capabale of about 100mA at a few hundred volts to stop things when the duty cycle is commanded to be at

100% or a bit less.

Just some thoughts. I apologize if I have stepped on any toes.

Reply to
John S

Yes, thank you, George. I saw it. But your image and your ASCII drawing above do not agree. Your ASCII drawing is a standard buck without an output filter capacitor. I agree with your ASCII (with, possibly, the requirement for an output filter capacitor) for a scheme which could work.

Reply to
John S

You've got the gist of the problem. I made up some of the numbers and didn't notice they didn't quite correlate. But you see the premise for the problem.

To maintain some semblance of efficiency, I can't simply 'shunt' unused power off.

Reply to
RobertMacy

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