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Estimate the total power consumption of a PCB board..

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flote21

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Hello folks!! I have a question....imagine you want to estimate the minimum power to supply a PCB board with several digital components. These components are divided in two groups. 5Volt components and 3.3Vol components. The theoretical power consumptions for both voltages according to those components are: 5V/2A and 3.3V/1A. If the PCB is supply with 24V. Which is the minimum current from the 24V source you will need to reach the total power requirements?

Is there any good simulator to estimate the general power consumption of a PCB board according to the individual power consumption of every PCB board device?

Greetings!
 

CONSERVATION OF POWER

Are you using a linear regulator or a switcher? If you are using a linear regulator, then your total current is just the sum of all your currents, regardless of voltage. If you are using a switcher, then you need to know the efficiency to calculate required current.
 
I am using switching regulators with a 97% of efficiency at maximum power...how can affect this parameter to the final calculations? Can you give me a math example, please?
 

Total power consumed by the PCB is

5 x current consumed on the 5V supply plus
3.3 x current consumed on the 3.3V supply.

That gives you the total demanded by the board in Watts. If you assume 100% regulator efficiency the same power will be drawn from 24V so the current would be (I = W/24) in Amps. The regulator being less efficient than 100% means more power has to go in at 24 than comes out at 5V and 3.3V so multiply the input current by 1 + (100/efficiency) to find the current from 24V. Note that the 97% you quoted is probably a best case figure under full load, it may be less efficient at lower loads which means the current may be higher than anticipated.

Brian.
 
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