super capacitor

Status
Not open for further replies.
R

raman00084

Full Member level 6
Joined
Nov 29, 2010
Messages
362
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,298
Activity points
4,006
I am having a 24v smps with 3 amps current rating. If power is off i need a backup time of 5 sec with 1 amps current rating.
what capacitor can i add any circuit available kindly help.
 

its i = C.dv/dt

If you want to keep voltage at 24V whilst 1A is delivered, then you may need an extra SMPS to do this for you aswell.
 

For a crude estimate, use the RC time constant. Your load calculates as 24 ohms (24V divided by 1A). Suppose you choose 1 Farad for your backup capacitor. Then your RC time constant is 24 seconds. Voltage drops 63 percent in that time by definition.

Therefore in 5 seconds it drops about 13 percent. If your circuit continues to operate then a 1F capacitor is satisfactory. Or else 2F lets voltage drop 6 percent in 5 seconds. Etc.
 

    R

    raman00084

    Points: 2
    Helpful Answer Positive Rating
Hi,

Or calculate the energy.

Generally a capacitor will immediately drop voltage .... the drop rate V/t is proportional to current.
Thus it's impossible for a capacitor to keep voltage constant (24V) when you draw current.

Currently we see just "24V", no valid range in voltage or %.
You urgently need to decide this to find a suitable solution.

Klaus
 

It might be that you'd be better off with a battery
(capable of >1A discharge). Supercapacitors are
not especially cheap, but simple. Many modern
batteries are not overcharge-tolerant and so
would need charge control and a capable
switch (could be just diodes, if you're lucky).

If you architected your supply around the need
for hold-up, could be easier - line to battery is
one section, pretty common charger design with
enough upside current to handle the
through-load-current when line is up, and then
battery to output as a regular ol' buck?
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…