TEC Driver Problem

[DDM]

Hello.

I am trying to stabilise the current sent to a TEC for a 1480 nm laser diode pump made by Fitel. The TEC comes packaged with the diode and thermistor in a 14 pin butterfly form. I am using a Newport 8325D TEC module driver.

My problem is that the current sent to the TEC, climbs by 0.01 amps every second and never stops. The set temparture does stabilise but not the current. I have a 10k Ohm resitor and some specifications for the TEC such as maximum current and voltage.

Also, I tried to work out coefficients for the thermistor, by manually measuring the resistance of the thermistor under different temperatures, but the current supplied to the TEC continues to increase about 0.01 amps per second. This occurs also after changing the default coefficients from the TEC module to the new calculated ones by using a 1st order polynomial (as high accuracy is not needed for my application) as described in the User Manual document provided by Newport.

I will appreciate your comments.

 

[HIMNL9]

Does this happen with the LD in working state ?

If yes, have you considered that this can be normal ? (increasing the current on TEC from the temperature stabilizing circuit, when the heat increase from the LD working, i mean)

Also, the "hot" part of the TEC (LD case) is efficently heatsinked ? (when the heat on the case/heatsink increase, the TEC plate need to work more for keep the same temperature inside)

 

[DDM]

Yes, I forgot to mention the LD is on when this occurs.

The main problem is that once the TEC current reaches its limit, the TEC driver automatically turns off, leaving the LD with no cooling.

Thanks for your comment.

 

[HIMNL9]

Uhm, this may mean that the driver is not good for your TEC type, ot hhat there's something not working good in the circuit or in the setup ..... any pic of the setup ?