# Concept Question about Maximum Power Transfer (More than cursory)

Discussion in 'Homework Help' started by snipe, Dec 13, 2010.

1. ### snipe Thread Starter New Member

Dec 13, 2010
1
0
Hi All,
This is my first my first post, but I am a long time fan of the site, and I am running into a wall with a problem at work.

My question is, does Maximum Power Transfer (MPT) apply to DC current sources?

Can a DC current source be damaged, if it is continuously cycled, while NOT achieving MPT?

Further more, will MPT apply to the "apparent resistance" of a series of forward biased PN junctions?

I hope the real questions don't get lost in the problem explanation, but here is an overview of the problem:

There is a DC current source, sourcing 15A, to 54 series connected PN junctions in a forward biased configuration. When applying this circuit, the voltage on the current supply settles at around 39.85 vDC. We are applying this power for a minute or two to slightly heat up the PN junction, and then examining them with an infrared camera, in a mass production environment. So, 15A @ ~40v is a resistance of around 2.6Ohms for all of the PN junctions.

Also, looking at it from the perspective of the PN junctions, if each PN has a voltage drop of 0.707v, times 54 is 38.18v. This is close to what I'm observing. Applying Ohm's law we find that the resistance should be in the range of 38.18v/15A ~= 2.54Ohms. This is also very close to what I'm observing.

So, with this configuration, using a DC current source, would I be able to design a resistive network, or implement a matching transformer, to transfer maximum power to the load? It seems more complicated since a current source model has a large resistance in parallel, while a voltage source has a small resistance in series....

OR.... Am I forgetting a fundamental, and I'm chasing a ghost? Does MPT not apply to DC current sources? I haven't been able to find much information about this situation.

Thanks