Increasing peak curent from a power supply

[Sceadwian]

You know, I can't find it anywhere in this post, what's the voltage of this supply?

 

[jwriter]

It would be so much easier just to buy a power supply with enough current. Power (Watts/$) is so cheap these days...

Yes, but 0.5 F caps are cheap now too! There are cases, especially for low voltages and oddball voltages where it might be cheaper to use passives. Plus this technique can no doubt be extended to higher pulse current, lower duty cycle situations. For example, you may not want to pay for 10x higher current rating if you have 10x pulses. And (lastly) some power supplies do not support high ripple current at high frequency. I have some Meanwell data that says you can't pull 80% current pulses continuously above 1 kHz. Think about the electrolytic on the output of the supply, which has its own ripple current ratings. So the LC has its place. Warning: for those who want to try this, I have looked at the ripple specs for supercaps and you should not use them for this purpose. You would probably want to put another, lower value, lower ESR, standard electrolytic in parallel with the supercap. More research needed.

Yes it does work at higher frequencies. I've re-run the sim. Ignore my previous comment about not reaching full load current (Sorry, I think I must have been looking at a zoomed graph or something). Looks ok at 1kHz, but how high do you want to go? As the graph in post #15 shows, it takes over 1 sec for the inductor/supply current to stabilise at 5A. In the meantime it can briefly reach 9A or so. Is that going to be a problem?

Stabilization shouldn't be a problem if I use a current limited supply. Thanks for checking higher frequencies. I would like to go as high as 5 kHz if possible. I would say that an LC filter would be required in this situation, as the switcher alone almost certainly wouldn't like high frequency, high current pulses. Getting the right combination of caps with proper ratings would be the ticket.

Alec, any chance you could post your net list so we can experiment with it?

 

[jwriter]

You know, I can't find it anywhere in this post, what's the voltage of this supply?

You're right, all I know at this point is that it's low voltage. However, this should work for a wide range of voltages, just need to model it.

 

[Sceadwian]

You're right, all I know at this point is that it's low voltage. However, this should work for a wide range of voltages, just need to model it

You mean you don't know? Low voltage is relative, there is no hard line, that's why specifications are important.

 

[jwriter]

You mean you don't know? Low voltage is relative, there is no hard line, that's why specifications are important.

Would you like to design my system? Sounds like you know more about it than I do. (humor)

 

[ronv]

Spice file

Here is the spice file I used. I did it a little different than alec. I used a current limit of 5 amps on the supply and a crude voltage regulator for the voltage.
But without a spec anything will work.

 

[alec_t]

...and here's my LTSpice file.

 

[jwriter]

Thanks ronv and alec. Really appreciate everybody's help in this thread, I have what I need a this time. Regarding voltage, Alec used 10 volts and that is close enough. I assume that the model can be easily scaled to any common voltage. May start a followup topic later regarding selecting high capacitance, high ripple capacitors. I have "discovered" Sprague 36D aluminum electrolytics and need to find out how they will work. Also, will be selecting a Spice program that will run on my Mac, so I can run your simulations.

https://www.electro-tech-online.com/threads/choosing-a-spice-model.111365/

Thanks again for the help.

 

[Sceadwian]

jwriter... I was just asking what the voltage was, it's no where in this post.