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Should i try using an ultracap?

Former Member

Im currently having the pleasure of working on a project where the cost of components is of little importance.

It's fun to work in this new way, but i find myself having trouble choosing components now that "the entire market is open to me"..

 

Here's the setup:

 

I'm designing a product that is to be powered by a regular switchmode DC supply. Minimum is 12Volts and 1 ampere (actually closer to 600mA)

 

The thing that's tricky is that the product has to retain it's power for 30 seconds after removal of the DC supply.

 

Meaning that i need a battery or supercapacitor that can supply at minimum 12V @ 600mA for 30 seconds.

 

I've already found a LiPo battery that can supply this. But am missing several key points in this particular design (charge circuit, power source chooser, step-up conversion to 12V and so on)

 

It would be so much easier if i could just put a super-cap in parallel with the supply, and let that take care of the 30 seconds of extra power, but i have no idea how to dimension a supercapacitor.

and, quite frankly, they scare me...

 

Any suggestions?

 

Regards

-Mark

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  • Hello Mark, usually the best way is place an small battery in the output for get the perfomance of 30 seconds hold up time for output load current requeriment, I think the same of Jonathan.

     

    The ULTRAcaps or SUPERcaps are complex for charguing and need best way form constant current method. It depend on your controller for PWM control, can make overload protection and can see hiccup mode due the current demand the ultracap is high if not are controlled by any IC.

     

    Regards,

     

    José Antonio

  • in reply to Former Member

    Hi Mark,

     

    Lowering your holding time to 10s would mean an capacitor of about 1500uF/400V. Still a large container. You could bring it down to 1000uF if the output voltage is somewhat higher (450Vdc), but that would mean a lot of tweaking....

     

    A pitty that the 600mA is not open for discussion.

     

    Jonathan, A PFC-controller does not mind having a large capacitor at its output. The input current of the circuit will always be nicely matched to the input volatge.

     

    Best regards, Enrico Migchels

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  • in reply to Former Member

    Hi Mark,

     

    Lowering your holding time to 10s would mean an capacitor of about 1500uF/400V. Still a large container. You could bring it down to 1000uF if the output voltage is somewhat higher (450Vdc), but that would mean a lot of tweaking....

     

    A pitty that the 600mA is not open for discussion.

     

    Jonathan, A PFC-controller does not mind having a large capacitor at its output. The input current of the circuit will always be nicely matched to the input volatge.

     

    Best regards, Enrico Migchels

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