# How to match the load of a DC-converter?

Hi!

I'm having a few TEG-elements (TEP-1264-1.5) that I want to put best use of and plug them in to a circuit in one end and get a 5V USB in the other end!

They are acting somewhat similar to solar panel and a matched load (in this case 2.0 - 2.8 Ω for each) is needed for optimal performance. They will provide during matched load 2.5-4V and 0.5-1.5A and I'm planning on putting two of them in series.

I have been looking at a MPPT design, but those seem to be based on the fact that they are charging a 12V battery that can accept a wide range of input voltages and therefore it's possible to have a DC/DC converter that just adjusts the conversion.

In my case I wan't exactly 5V but I can accept various currents 300mA - 1000mA, so if I know my Ohms law right I should be able to get a load resistance of ~1 - 16 Ω which is quite far out of range.

Is there any way to design a circuit that has a matched load of 2.0-2.8Ω (or will it be twice if they are in series?) while still being able to give a constant output of 5V?

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steveastrouk3 months ago

LInear Technology have quite a name in MPPT silicon, you should look at their design notes for ideas.

Granstubbe (author)  steveastrouk3 months ago

Can you specify what kind of circuit I'm looking for? Their design notes page http://www.linear.com/designtools/app_notes.php is quite hefty and my electronic design skills are not something I'm proud of.

iceng3 months ago

You do understand that with a variable output voltage, that resistor will also need to change as does the voltage, ergo there is no reasonable single resistor that can fit your need... A TAG like a Solar-panel has variable voltage and available power output..

More to come..

3 months ago

You should also be aware that connecting copper wires to single digit resistors has a small but not negligible series resistance...

Regardless, you need an electronic converter that can generate your chosen voltage.. The available current will be a function of power input up to the maximum the electronic device can deliver...

Granstubbe (author)  iceng3 months ago

Thank you for taking the time, but you have to excuse me but, I have fairly little knowledge in electronics design, what kind of circuit am I looking for?

A single resistor is out of the question since temperatures will change, as will the optimal resistance. As seen here in the attached image , I need to find the "resistance sweet spot" while I still retain 5V output. But how I do that is beyond my knowledge. Is an ordinary buck-converter my best option here?