Driving Peltier Device through L298N to control Temperature

[sachin2611]

Hi,

I want to drive peltier element to control temperature of one module. Peltier specifications are:
Imax = 9A and Vmax = 3.75V.

Such 4 peltiers are connected in series to control to module temperature.

I am planning to use L298N for driving it. As shown if I connect L298N two pins in series then I will be able to drive current upto 4A. But, to control my module temperature, Peltier is sinking average 4A current.
So, It I can't use single L298N IC as it will heat too much and also it will damage.

So, I want to know whether it is possible to use two L298N ICs in parallel to give higher current.
If so then please advice me for input and output pin connections.

Thanks & Regards,
Sachin Panchal

 

[jiripolivka]

I do not think it is a good idea to use two regulators in parallel. They can and will oscillate. As the load needs 9A DC current, you can use a power transistor or MOSFET (or several those devices in parallel) driven by the regulator. See data sheet of L298N where a recommended solution should be given. Or check LM317T data sheet, there is a recommended schematic.

For good results, find ARRL Radio Amateur's Handbook, there are descriptions of high-power AC/D converters you can use.

 

[sachin2611]

Hi Jivipolivka,

9A and 3.75V are maximum rating of my peltier device. So, I have to limit both at arroung 6A and 3V.
If I use MOSFET then I think complete 12V will drop across peltier and It will damage it. Also, L317 can give current max. up to 1.5A. And I want to average current around 5A.

So, please provide me any other option.

Thanks,
SAchin

 

[jiripolivka]

Hi Jivipolivka,

9A and 3.75V are maximum rating of my peltier device. So, I have to limit both at arroung 6A and 3V.
If I use MOSFET then I think complete 12V will drop across peltier and It will damage it. Also, L317 can give current max. up to 1.5A. And I want to average current around 5A.

So, please provide me any other option.

Thanks,
SAchin

Please read again my advice above. You cannot run regulators in parallel but you can use them to drive several MOSFETs or e.g.2N3055 transistors in parallel. Details can be found in data sheets and the ARRL handbook.

 

[dick_freebird]

The Peltier modules' Imax is just that, a maximum rating.
You should respect it and work lower. You will benefit a
lot more from cooling airflow (delta-T on the module is
the big deal) than the last bit of current.

Series connected TECs are simple to control and if you
have a 12V source you may not need to control them
at all (provided the heat-throw at 3V apiece is adequate).
Then your "control" could just be a snap-action
thermostat.

Maybe you should step away from your insistence on a
particular DC-DC, look for a buck-boost converter that
has an OK input voltage and output current range, and
use that.

I've found the TECA modules to be pretty tolerant of abuse
but don't know what yours are, mfr / vintage / spec margin.
I've put them on an electric stove burner and used them
to generate power. As long as you don't melt the nuggets
(bismuth antimonide?) you're probably OK. You might want
to add some protection like a hot-side thermostat to make
sure a cooling-airflow defecit / blockage doesn't drive the
assembly into sustained overtemperature.

 

[sachin2611]

Hi,

One more requirement is added to my project and that is to make temperature controller such that instead of 4 series peltier if I connect one, two or three then also I should work.

So, Old idea to drive it with direct 12V such that 4 peltiers have drop of 3V will not work.

Means, My new requirement is to fix voltage below 3V for any number of peltier and current up to 6A.

Please suggest me.

Thanks & Regards,
Sachin

 

[dick_freebird]

I think that you will encounter current sharing problems
as the modules heat up differently, if you parallel them.
Is the requirement one of fault tolerance, or just optional
quantity / configuration?

How much efficiency can you afford to throw away to
enforce module power matching?

A current mode boost converter could run 1-N in series
at identical current, but a single open fault would mess
things up. Perhaps you could do something like a boost
topology, discontinuous mode, maybe even interleaved,
with a matched on-time and matched inductor you would
get matched current more or less; if your choice of 1, 2,
3, 4 is allowed to be by jumper (say), then you can cut
wasted power easily enough. There might be some scheme
that's sort of like a boost but would go to zero current on
open circuit (like B+ - TEC - inductor - LSS with a back
diode from (inductor - LSS) back to B+ that would make
a circulating path for the current but an open TEC would
leave the LSS switching nothing but a reverse diode. I
don't know a name for this scheme and haven't seen it
used, it just occurs to me.