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Discrete based constant "power" dummy load (NOT constant current)

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Again, its not constant current dummy load, but constant power/wattage dummy load and adjustable too.

Has anyone ever built, designed or encountered such circuit design ?

Preferred discrete components based, rather than using micro controller, and the sole reason is only for improving skill and understanding in analog realm.

I've been thinking for quite sometime to build it if I can find any schematic, and it will be a nice addition at the bench measurement tools families. Not overly ambitious, maybe under 100 watts, DC based and at  few amps with max voltage something around 12 or 24 volt would be nice.

Not sure, probably my "google-fu" is not good enough, still can not find it at the net.

Really appreciate if you ever designed one or even better made one and of course if you don't mind share it here please.

An LED buck or boost driver will sort of do this. Such drivers are designed to supply a constant current into a load with a constant voltage drop. That makes their power consumption on the input side almost constant, allowing for varying converter efficiencies.

You need to multiply amps and volts in your load to sense the power you are trying to control.

Analog multipliers are a bit finicky and old-school, however, there are some modern battery power monitoring chips which include one.

Look up the Linear Tech LT2940. The data sheet has a couple of constant power load application circuits.

Maxim do a similar chip, there may be others.

Conrad Hoffman:
IMO, it's a pretty good idea. I know adjustable electronic loads (Google that term in quotes) have been around for a long while, but I don't know if they offer a constant power feature. I wouldn't be surprised if they did. (OK, opened another tab and found http://www.hotektech.com/EPSFK.htm ).


If I'm not mistaken, Elektor did an article that is exactly what are you looking for (search for high power adjustable load). For constant power, instead of using a constant voltage for the reference, it used a voltage derived from the load input to control the current.


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