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TINA/Spice/TPS63020: Simulation TEC driver (according to SLVA677) - works in single direction only

Jiri Kolouch34
Prodigy 200 points
Part Number: TPS63020
Other Parts Discussed in Thread: TINA-TI,

Tool/software: TINA-TI or Spice Models

Hello all,

Reading the SLVA677, I considered to make simple TEC driver with TPS63020. I downloaded simulation environment for TPS63020 to TINA-TI - SLIM154, modified schematic according to the app note and run.

When Vin < Vout, it works as expected. Unfortunately, when Vin > Vout, Buck-Boost bridge doesn't recirculate the current flowing through TEC from input to output back to the input.

Could anyone try in TINA-TI and if successful, place there working schematic environment?

Thanks in advance!

Jiri

  • 0
    TI__Expert 3465 points
    Hello Jiri,

    welcome to E2E, it's a pleasure to support you!

    May I ask you how you modeled the TEC in TINA-TI ?

    Regards,
    Emmanuel
  • 0 in reply to Emmanuel Granatello
    Prodigy 200 points
    Hello Emmanuel,
    thanks for reply! Modeling the TEC is quite straightforward - it is more or less resistive load, with small voltage dependency and temperature dependency. So for analysis in TINA, I could just use resistor.
    Could you try for me to simulate the circuit described in SLVA677 using TINA and TPS63020 (www.ti.com/.../slim154)
    Regards, Jiri
  • 0 in reply to Jiri Kolouch34
    TI__Expert 3465 points
    Hi Jiri,

    I am trying out your design simulation. How much is the TEC resistance you are using ?

    Regards,
    Emmanuel
  • 0 in reply to Emmanuel Granatello
    Prodigy 200 points
    Hi Emmanuel,

    We use TE-65-0.6-0.8 module, which is rated to Vmax=8V, Imax=2.1A.
    Equivalent resistance is therefore approx. 4 Ohms, but due to non-linear V-I curve, I assume lowest resistance of 2.8 Ohm.
    We do not use maximum ratings of this TEC (3.5V is enough).

    Looking forward for your reply,
    Jiri
  • 0
    TI__Expert 3140 points

    Hi Jiri,

    Could you please share your .tsc file with us? This will help us to replicate the issue and look into it.

    Thanks & Regards,

    Arpan Gupta

  • 0 in reply to Arpan Gupta
    TI__Expert 3465 points

    Hello Jiri,

    After doing some simulation and researches I'm back with an answer. 

    In the app-note SLVA677, in particular at the end of page 2, it's mentioned:

    "To drive the TEC properly, the buck-boost converter must source and sink current. When using the TPS63020, this is achieved by forcing the converter in fixed frequency operation. This is done by disabling the built-in power-save mode. Since the TPS63020 can source more current than it can sink, it is important how the TEC is connected to the circuit. In general, the devices which should be kept at a controlled temperature generates heat. For this reason, cooling typically requires more power than heating. So in most cases, the TEC is best connected in a way that it is cooling the device while the TPS63020 is sourcing current." 

    Indeed at point 3 the example's characteristics is reported. It shows clearly the effect of the negative current limit when Vctrl is higher then the simmetry point (Which means Vout>Vin).

    So, the result of the simulation should not actually surprise us, given those premises. Although, the TINA simulation does not really fit with the real device behaviour because it is based on a software model. From my simulations, the negative current limit seems to be set a bit higher (closer to 0A).

    To sum up, under my point of view, this application note highlights how you actually can achieve cooling down capabilities, and within a certain extend also warming up, of an apparatus by controlling a simple, cost and space effective buck boost.

    Best regards,

    Emmanuel

     

     

  • 0 in reply to Emmanuel Granatello
    Prodigy 200 points

    Dear Emmanuel,

    thanks for the effort you spent on my support request. To conclude:

    1. Yes, it is documented in SLVA677 that TPS63020 can sink less current than it can source.
    2. Unfortunately, TINA spice model (encrypted) shows close-to-zero sink capability. For spice models in plain text, I can read release notes where model limitations are published. Where can I read the model limitations for TIencrypted model? Will TI provide model update?
    3. If TPS63020 can sink, where can I read how much - meaning guaranteed minimum, not typical values? Otherwise, I can't plug such device to industrial application.

    Waveforms and *.TSC file follows:

    TPS63020-TECdriver_slim154.TSC

    I rely on your further support!

    Kind regards,

    Jiri

  • 0 in reply to Jiri Kolouch34
    TI__Expert 3465 points

    Hello Jiri,

    you are wellcome. We are here to support you. To answer your questions:

    2. TINA-TI model limitations for the TPS63020 are not reported.

    3.   minimum guaranteed current is a parameter which should be included in the datasheet of a device. In the case of the TPS63020 this parameter is not specified.

    Thanks and best regards,

    Emmanuel

  • 0 in reply to Emmanuel Granatello
    Prodigy 200 points
    Hi Emmanuel,

    thanks for reply. As you stated, in case of TPS63020 is minimum value of current sink capability not documented. Bad luck for designers, especially when interesting app-note SLVA677 shows the principle.

    Unfortunately, this leads to the conclusion that I can't use TPS63020 for purpose shown in the SLVA677 and have to check in competitors portfolio.

    I do not know how to properly close this thread - I can't use button "This resolved my issue" :(

    Jiri
  • 0 in reply to Emmanuel Granatello
    Prodigy 200 points
    Stating that SLVA677 shows the principle but " In the case of the TPS63020 this parameter is not specified" doesn't help.
  • 0 in reply to Jiri Kolouch34
    TI__Expert 3465 points
    Hi Jiri,

    the usual application case of a TEC is to regulate the temperature of something that gets warm. That means that in those cases one does not need a full driving capability of the TEC, but only half plane (negative or positive currents). If you really need to also generate heat from the TEC, then I agree with you, SLVA677 guidelines and TPS63020 don't help, but in the opposite case I would consider our solution.

    Thanks and regards,
    Emmanuel