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#1 Apr 1, 2021
magnataiwan
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#### how to use "PowerDissipation_mW" at toggle measurement results window

hi

dose anyone know how to use "PowerDissipation_mW" at toggle measurement results window

the user manual describe PowerDissipation_mW(1,period)

1=V(load)*I(load)  but what is exact period meaning  that is simulation setting >>run to time ? or can i type in what period i want ?

Mon, 2021-04-12 20:43
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To view the script that performs that measurement, go to Trace => Measurements. From the list, click on "PowerDissipation_mW" to select and do Edit. Then you'll see this code:

PowerDissipation_mW(1, Period) = (y1-y2)*1000/(x1-x2)
*#Desc#* Total Power dissipation in mW during the final 'Period' of time.
*#Desc#* Find the difference between the final Y value of the trace and
*#Desc#* the Y value one period before that.
*#Desc#* (Can be used to calculate total power dissipation in mW, if the
*
*#Arg2#* Period
*
* Usage:
*
{
1|Search forward xvalue(100%) !1
Search backward /x1/ xvalue(.-Period) !2;
}

So it looks like the talk about the "s()" function is about integratings. I assume s is the integral because an integral sign kinda looks like an s.

The period is a lookback period from the end of the sim, I guess so that you can cut out the first part if it's not at steady state yet. Maybe use something like half the sim time for the period. The other thing I noticed experimenting with this function is you get the same results using the power function w() as you do using V()*I(), so I am using that instead like so:

Input Power:

PowerDissipation_mW(S(W(Vin)),9u)

Output Power:

PowerDissipation_mW(S(W(RLp)),9u)

Efficiency:

PowerDissipation_mW(S(W(RLp)),9u)/-PowerDissipation_mW(S(W(Vin)),9u)

Hope that helps

Tue, 2021-04-13 10:52 (Reply to #2)
magnataiwan
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thank you for give me the reference  , but i am still confused with "period"

i assume my simulaiton running time is 1.5ms and would like to calculate W during 1.1000ms to 1.1001ms. it is impluse wavefrom and occurs in short time

here are expressions i am used of

1.PowerDissipation_mW(S(W(R13)),1.100m-1.1001m)=87.65m

2.PowerDissipation_mW(S(W(R13)),1.100m)=119.53m

3.PowerDissipation_mW(S(W(R13)),1.5m)=87.65m

which expression is correct?

Tue, 2021-04-13 12:56
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It looks like the period starts from the end of the sim and goes backwards, so none of those will work. If you want W during 1.1000ms to 1.1001ms then you'll need to set your simulation running time to 1.1001ms and then set your period to 0.0001ms I think. Does that make sense?

Wed, 2021-04-21 03:46
magnataiwan
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