help needed in current consumption calculation

EDAboard.com Forum Index -> Electronic Elementary Questions -> help needed in current consumption calculation

Author

Message

ringo888

Joined: 02 Feb 2009
Posts: 13

11 Sep 2009 10:27 how to calculate current consumption

Hi Guys,

I've come abit stuck on this one:

If I had 2 seperate regulators (+5V and +3.3V) and i was getting current consumption of:

250mA @ 5V
and 400mA @3.3V

How would you calculate the current at Vin if Vin was say 12V. This is just a generic question, I don't have a real-world circuit to provide any further information, its just a general question.

As usual, any help would be really appreciated.
Thanks,
Ringo888

pauloynski

Joined: 06 Oct 2004
Posts: 277
Helped: 34
Location: Brazil

11 Sep 2009 20:46 Re: Current consumption calc

If both are linear regulators the output current equals the input current plus the current consumed by the regulator itself. So just add the currents.
If they are buck (SMPS) regulators, calculate the output power of each one, divide them by their respective efficiencies, sum them and divide the result by 12.

Google
AdSense
Google Adsense

11 Sep 2009 20:46 Ads

senthilkumar.b

Joined: 29 Aug 2009
Posts: 54
Location: india

18 Sep 2009 11:27 Current consumption calc

hi,

As per your statement, your source voltage is 12v lets take DC.

There are number of methods available for voltage regulation purpose. that system should consume some power. such a manner you should calculate total power dissipation in that design.

This total power delivered by 12v DC supply.

Now you can easily calculate the source current.

Bye

horzcat

Joined: 24 Jun 2008
Posts: 54
Helped: 2

19 Sep 2009 12:22 Current consumption calc

for dc case, multiply the current and voltage at output to get the power. divide power by input voltage to get input current. Remember to sum the output powers of both the regulators.