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

Started by RobertMacy October 16, 2013
On Thu, 17 Oct 2013 00:39:23 -0700, Tim Williams <tmoranwms@charter.net>  
wrote:

>> ...snip my stuff... > ...snip question on source... > AC input isn't *quite* a big deal, because you can use a synchronous > switching design, where MOSFET and diode are both replaced with > antiseries > MOSFETs. (A bidirectional synchronous buck, at fixed duty cycle, is > pretty cool -- it's a VARIAC without the iron core!) > > Also... EMI concerns? Can the line be switched directly, or does it need > filtering? (You might recall from the current-to-current buck circuit, > the line will see full switching voltage -- just as a conventional > voltage-to-voltage circuit sees full switching current. Both kinds are > nasty to nearby radios without bypass and EMI filtering.) > > Tim >
Is that component, antiseries MOSFETs, commercially avaialable, or does one have to always 'roll their own' What's the schematic for it? RFI/EMI is always important, but in this case it's make it work, then worry.
On Thu, 17 Oct 2013 06:01:01 -0700, George Herold <gherold@teachspin.com>  
wrote:

>> ...snip... > OK... We haven't done many AC circuit yet.. but I'm guessing the same > sort of thing can be done. > For completeness here's the way a current source buck-boost should look. > > https://www.dropbox.com/s/eey79dkci1sqpp0/DSCF0034.JPG > (I figured out in the shower that the capacitor was in wrong.) > > George H.
Thanks again for the images, surprisingly this time dropbox let me view them - usually doesn't. IN: AC with source current maybe 30-50mA, compliance to 1kV OUT: approx 5Vdc, with variable current, adjusted with time envelope from 0.8A down to 50uA. with source current that low, can't just feed it straight thru. assuming NO losses... with input compliance at 80V and using all 50mA, supply the 5V at 0.8A You see why I first said current to current conversion? After major floundering around [and rather embarrassingly] in front of all of you; I am starting to perceive the final topology as a multi-step: AC to DC at power required, then DC to DC at current required. But even 90% at each step yields a terrible 80% over all, so I was trying for a single step: AC to DC at current required. I can always flip the diode to make it a positive supply. That does look like a 'single' step. Tim's right about paying attention to the RFI/EMI kicking back into that source. Any parasitics and !!! It's going to be fun trying to filter out that 50V ON/OFF appearing across the MOSFET terminals let out into the world through that inductor at 1MHz.
On Wed, 16 Oct 2013 21:15:39 -0700, RobertMacy
<robert.a.macy@gmail.com> wrote:

>On Wed, 16 Oct 2013 09:43:03 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: > >>> ...snip... >> So SMPS SHUNT regulator ?:-} >> >> ...Jim Thompson > >If the shunt is linear, it will eat power; but if it is a switched >shunt..., got to think about that. > >However, I forgot to mention something really important here. The input is >AC, which [I think] I do NOT want to allow to go maximum compliance. >ARRRGG! Usually right after I post a question the answer is obvious, but >not this time. I must not even have a handle on the problem yet. My >question is coming out like drivel. It's just I have this sense that the >solution is an 'invrsion' of a normal solution, and I must turn my >thinking 'wrong-side' out. > >I could allow full compliance and then tap off what's necessary, but >allowing the full compliance voltage and only tapping off to what is >needed raises the spectre of what-ifs. One should ALWAYS allow for >potential operation ANYWHERE within a supply loop. I remember the days >when power supply designers neglected to consider 'brown outs'.
I'm not quite understanding your requirement. You can send me details in private if you like. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Wed, 16 Oct 2013 09:43:03 -0700, Jim Thompson  
<To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:

>> ...snip... > > So SMPS SHUNT regulator ?:-} > > ...Jim Thompson
Alas, the compliance current is around 50mA with a compliance voltage as high as 1kV, which is destructive. A 'straight' shunt regulator either shorts out the incoming 50 mA or let's it pass thru, but in this case I sometimes need 800mA at a small 5Vdc. So, need some 'multiplication' of the current - a capacitor. There is sufficient power if the system operates with the compliance at around 80V at 50mA just have to somehow convert that to 5Vdc at 800mA. But, in this case it will be super necessary to monitor compliance voltage so it won't EVER go above 100V in order to NOT kill parts. In this supply that protection circuit, or 'voltage limit', is the corollary of the standard 'current limit' in a voltage supply! So far it appears a variation of George Herold's approach may get me there. the current charges a cap, which then supplies large amount of power. Aain, corollary, using cap instead of inductor for the energy storage/conversion.
On Thu, 17 Oct 2013 07:55:22 -0700, Jim Thompson  
<To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote:

>> ...snip... > I'm not quite understanding your requirement. You can send me details > in private if you like. > > ...Jim Thompson
Thank you for your kind offer. I am being vague for two reasons: 1. purposely obfuscating the actual application/techniques under cloak of NDA. 2. inadvertantly floundering around, albeit embarrassingly, but in my defence, this is NEW territory here.
On Thu, 17 Oct 2013 08:04:25 -0700, RobertMacy
<robert.a.macy@gmail.com> wrote:

>On Thu, 17 Oct 2013 07:55:22 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: > >>> ...snip... >> I'm not quite understanding your requirement. You can send me details >> in private if you like. >> >> ...Jim Thompson > >Thank you for your kind offer. I am being vague for two reasons: >1. purposely obfuscating the actual application/techniques under cloak of >NDA. >2. inadvertantly floundering around, albeit embarrassingly, but in my >defence, this is NEW territory here.
BTDT ;-) MANY of the projects I take on are new territory... that's what makes them fun. ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | San Tan Valley, AZ 85142 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
"RobertMacy" <robert.a.macy@gmail.com> wrote in message 
news:op.w43rffpy2cx0wh@ajm...
> Is that component, antiseries MOSFETs, commercially avaialable, or does > one have to always 'roll their own'
Yes... and yes. Commonly available with a photovoltaic gate "drive" as the smaller AC/DC SSRs. They switch in miliseconds. You'll need an isolated gate driver for each switch, plus whatever coupling (optos?) and control (PWM something or other?) to make it go.
> What's the schematic for it?
http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Antiseries_MOSFET_Switch.gif Obviously, substitute 9V and switch with whatever driver is suitable :) Tim -- Seven Transistor Labs Electrical Engineering Consultation Website: http://seventransistorlabs.com
On Thu, 17 Oct 2013 08:18:09 -0700, Tim Williams <tmoranwms@charter.net>  
wrote:

>> ...snip.... > Commonly available with a photovoltaic gate "drive" as the smaller AC/DC > SSRs. They switch in miliseconds. > > You'll need an isolated gate driver for each switch, plus whatever > coupling (optos?) and control (PWM something or other?) to make it go. > >> What's the schematic for it? > > http://webpages.charter.net/dawill/tmoranwms/Circuits_2008/Antiseries_MOSFET_Switch.gif > > Obviously, substitute 9V and switch with whatever driver is suitable :) > > Tim >
milliseconds?! arrrgggg, need submicroseconds! Thanks for the .gif
On Thu, 17 Oct 2013 07:58:24 -0700, RobertMacy
<robert.a.macy@gmail.com> wrote:

>On Wed, 16 Oct 2013 09:43:03 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: > >>> ...snip... >> >> So SMPS SHUNT regulator ?:-} >> >> ...Jim Thompson > > >Alas, the compliance current is around 50mA with a compliance voltage as >high as 1kV, which is destructive. A 'straight' shunt regulator either >shorts out the incoming 50 mA or let's it pass thru, but in this case I >sometimes need 800mA at a small 5Vdc. So, need some 'multiplication' of >the current - a capacitor. There is sufficient power if the system >operates with the compliance at around 80V at 50mA just have to somehow >convert that to 5Vdc at 800mA. But, in this case it will be super >necessary to monitor compliance voltage so it won't EVER go above 100V in >order to NOT kill parts. In this supply that protection circuit, or >'voltage limit', is the corollary of the standard 'current limit' in a >voltage supply!
Your monitor could just be a 5W zener diode across the input (or a small zener + BJT).
> >So far it appears a variation of George Herold's approach may get me >there. the current charges a cap, which then supplies large amount of >power. Aain, corollary, using cap instead of inductor for the energy >storage/conversion.
What the heck source are you working with, if you can talk about it?
On Thursday, October 17, 2013 10:58:24 AM UTC-4, Robert Macy wrote:
> On Wed, 16 Oct 2013 09:43:03 -0700, Jim Thompson =20 >=20 > <To-Email-Use-The-Envelope-Icon@on-my-web-site.com> wrote: >=20 >=20 >=20 > >> ...snip... >=20 > > >=20 > > So SMPS SHUNT regulator ?:-} >=20 > > =09 >=20 > > ...Jim Thompson > Alas, the compliance current is around 50mA with a compliance voltage as =
=20
> high as 1kV, which is destructive. A 'straight' shunt regulator either =
=20
> shorts out the incoming 50 mA or let's it pass thru, but in this case I =
=20
> sometimes need 800mA at a small 5Vdc. So, need some 'multiplication' of =
=20
> the current - a capacitor. There is sufficient power if the system =20 > operates with the compliance at around 80V at 50mA just have to somehow =
=20
> convert that to 5Vdc at 800mA. But, in this case it will be super =20 > necessary to monitor compliance voltage so it won't EVER go above 100V in=
=20
> order to NOT kill parts. In this supply that protection circuit, or =20 > 'voltage limit', is the corollary of the standard 'current limit' in a =
=20
> voltage supply! >=20 > So far it appears a variation of George Herold's approach may get me =20 > there.=20
Whoa! Hey, a big word of caution Robert. I've not built a spms in my life= . I'm taking this web course "Fundamentals of power electronics" by Robert= Erickson. (Colorado U.) I've done two weeks of lectures and HW. So your = question sparked the theoretical part of my brain. Which is great for me. = But for a practical circuit, I'd feel a lot better if one of the smps guru= 's signed off on it. Putting in your numbers, you're hoping for a current = gain of ~16 at greater than 80% efficiency. The few curves I've looked at = for voltage smps show that losses start to really bite into the efficiency = with higher gains. So you'll need to put in some real numbers. =20 (We've only started serious loss calculations this week.. so I'll know more= after the weekend :^)* =20 Maybe a combo of transformer followed by current smps would work? Anyway good luck... and not to worry about floundering around on SED. That= 's what's great about it. Throw out some crazy idea and see what sticks. George H. =20 *Dr. Erickson seems to know his stuff. In this weeks lecture he was modeli= ng switching losses and at one point paused and reminisced, (para phrasing) "We wasted several years with this model, because it lead u= s to try and switch current and voltage separately in time and that just di= dn't lead to any improvement in efficiency. Things are more complicated, b= ut this model is a good starting point." I just love that sort talk. It s= hows that everyone goes down dead ends. =20 the current charges a cap, which then supplies large amount of =20
> power. Aain, corollary, using cap instead of inductor for the energy =20 >=20 > storage/conversion.