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    ac consumption in a adapter

    hi,

    a basic question in electronics.
    I have a DC device with input rating 12V--2A which means it consumes 12x2= 24 Watt DC
    does it consume same amount of AC (by adapter) also while using AC to DC adapter?

    thanks

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    Re: ac consumption in a adapter

    Hi,

    In ideal case: Yes.

    But in real world:
    * The AC adapter will have some power loss = heating.
    * or in other words: the AC adapter will have a power efficiency of less than 1.

    AC_input_power = DC_output_power + AC_DC_Converter_loss

    or:
    AC_DC_Converter_efficiency = DC_output_power / AC_input_power

    Klaus
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    Re: ac consumption in a adapter

    Hi,

    That is the maxum power that your load consumes. At low load, it would consume less anyways.

    Your adapter has an efficiency curve against load demand. Your adapter efficiency is highest at peak load. As load decreases, the efficiency decreases.

    I hope this is what you asked for.

    - - - Updated - - -

    ADD:

    Your adapter if properly designed will have a small power loss compared to the power that your load consumes.
    -------------
    --Akanimo.



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    Re: ac consumption in a adapter

    So, just like Klaus has mentioned, you will lose some power during the AC_DC conversion. You need more than 24W at the AC_DC adapter input. The maximum power that you need at adapter input would now depend on the efficiency of your adapter.
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    Re: ac consumption in a adapter

    where can i see this efficiency factor in adapter description?
    take an example of smartphone's adopter. on adapter it is no where mentioned about its efficiency. however company claims that smartphone rewires 5 watts of DC.



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    Re: ac consumption in a adapter

    Hi,

    We can't see it, because we don't have your datasheet.

    But maybe it is not printed at all.
    Why do you need it?

    Klaus
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    Re: ac consumption in a adapter

    Quote Originally Posted by KlausST View Post
    Hi,

    We can't see it, because we don't have your datasheet.

    But maybe it is not printed at all.
    Why do you need it?

    Klaus
    i have to install 100 cctv of each 6 watt dc. (hikvision) need to know how much AC is consumed actually.



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    Re: ac consumption in a adapter

    Without knowing the exact specification of the power adapters nobody can tell you exactly.

    A GUESS would be:
    100 adapters at 6W each = 600W DC load

    If the adapters use conventional transformers and linear regulators, assume an efficiency of 75% so the total power needed would be 600 * (100/75) = 800W.
    If the adapters use switch mode supplies, assume an efficiency of 90% so the total power needed would be 600 * (100/90) = 667W.

    As you can see, the adapter efficiency makes a big difference to the total. If you are lucky the adapter manufacturer will tell you how efficient it is but in many instances you don't even get to choose which adapter is supplied and you could even get a mix of different ones for the same purpose. Distributors know it has to supply 6W output but they will send you any adapter that meets or exceeds that rating.

    Brian.
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    Re: ac consumption in a adapter

    Quote Originally Posted by ravi.2k17 View Post
    i have to install 100 cctv of each 6 watt dc. (hikvision) need to know how much AC is consumed actually.
    Get one of these: https://www.amazon.com/P3-P4400-Elec...s%2C205&sr=1-8

    and measure the power consumed by the adapter when it's powering the load.



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