Absorb current peaks with supercapa ?

Hello Bryan,

Thanks for the links, sorry, but I still don't understand how to use supercapacitors to help a power supply provide peak current. I have the impression that each scheme suggests using supercapa as backup, a bit like a UPS.

Can you enlighten me a little more please?

Thank you

Best regards

Olivier

Hi Olivier,

Thanks for your feedback. We'll get back to you later today with additional information.

Thank you and best regards,
Bryan

Hi Olivier,

I am sorry you did not get any feedback until now.
Is this request still open?

Do you still have the schematic available that you mentioned in the first request, or is this more like a general question?

Thanks and best regards,
Niklas

Hello Niklas,

Yes I am still interested in an answer. I don't have a particular schematic.

My request remains the same as that described before. that is to say, creating an energy reservoir with supercapacitors to support the power supply in the event of a current peak that it cannot provide.

Best regards

Olivier

Hi Oliver,

Thanks for the update.
A common application for supercaps is indeed a back-up for the main power supply (especially for batteries, which can drop due to coldcrank, etc).
For this, a bi-direction controller is often used to boost the voltage of the supercaps up to the battery voltage level in case the main supply drops, and then recharges the supercaps in the reverse direction if the main supply comes back up.

I hope this is the design idea you are referring.

We have devices for this approach, like LM5177 or LM5170.
If you check on the according product pages, you will also find reference designs on the battery backup approach.

Best regards,
Niklas

Hi Niklas,

Here is a little more detail, at my request. We have an AC/DC which can deliver 13V with 3A maximum. We did not choose this AC/DC and we cannot change it. The instrument we developed has a nominal current of approximately 1.5A.

Unfortunately, in some cases we have a current peak of up to 6A. And so in this case we have a certain part of our electronics which resets.

So I suppose that we can consider this situation as a loss of main power and therefore use the Backup principle? Can you confirm this hypothesis?

If this hypothesis is correct, then tell me if I'm wrong, but could a circuit like PMP9766 be suitable? In my case Vmain = Vsys, I must therefore find a circuit that operates at 13V 6A. Is my reasoning correct?

Do you know a circuit as "simple" as the TPS63020 but with higher voltage and current?

Thank you

Best regards

Olivier

Hello Brigitte,

OK, thank for your suggest. When you talk about adding an output capacity, are you thinking of a supercapacity or a more classic capacity?

In the LM5177 datasheet on page 50 there is a simplified schematic of a bi-directional operation. What do you think of this other solution?

Best regards

Olivier

Hello Hendrickx,

can you be more specific on this peak current of 6A.

How long will this peak last? What it the repeat rate?

Best regards,

 Stefan

Hello Stephan,

It is difficult for me to answer this question precisely. I would say that the peak can last 1 second with a delay between each peak of 1 minute. Then there may be a 30 minute break before a new cycle (peak of 1 second followed by another peak 1 minute later).

Best regards

Olivier

Hello Hendrickx,

OK, so just did some math:

Current from back up = 6A - 1.5A (from system) = 4.5A

Delta T = 1Sec

Assumed Delta V = 1V

C = I * dT / dV = 4.5A * 1s / 1V = 4.5 F

The LM5177 can be configured as backup supply as shown in the datasheet.

You need to consider:

- adding a charging limiter externally with: https://www.ti.com/lit/ab/snvaa69a/snvaa69a.pdf

- adding a startup circuit: the LM5177 needs to have a min voltage of 3.55V at VIN to startup. When using a SuperCap as buffer at VIN this is discharged at the beginning. So you need to provide an initial voltage at VIN to charge up the Cap.

Best regards,

 Stefan