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TPS61201: DC DC boost converter_TPS61201_Thermopile

Ritul Patel1
Prodigy 70 points
Part Number: TPS61201
Other Parts Discussed in Thread: TPS61200

Hello,

We are working on a self powered gas valve for water heater application. Thermopile works as a power source only. There is a bulk capacitor for peak current requirement but no primary and secondary battery as backup  Thermopile converts thermal energy into electrical energy when heat is provided from gas burner flame. We are looking for a low power DC DC boost converter which converts electrical energy of thermopile 350 to 850mV open circuit (R_teg=3.2 ohm) to 3.3V @ 30-40mA DC voltage to power up micro controllers and other peripherals of the system.

We have explored DC DC boost converter TPS61201 IC. After reading the datasheet and application note, We have below our queries.

1. We have a requirement to boost power from thermopile as power source but the application note having solar cell information. No battery backup used in our system. Do we require an additional MPPT circuit to control input current as mentioned in the application note?
2. If additional MPPT circuits are required, Do you suggest a TI DC DC boost converter which fulfill our requirement and inbuilt MPPT controller?
3. Please confirm that TPS61201 which can support operating voltage 350mV to 850mV DC thermopile voltage to generate 3.3V @ Approx. 50mA at output. In the datasheet, Required min. i/p voltage at startup : Max. 0.5V but no information about min. voltage.
4. Please review the attached power topology calculation of the system and provide your input about TPS61201 efficiency: 50% @ Vin= 350 to 850 mV, Iout=20mA, Vout =3.3V. Does thermopile capable to provide input current requirement?

 If you require more information, please let me know.

Regards,

Ritul

  • 0
    TI__Genius 9046 points

    Hi Ritul,

    Thank you very much for those detailed explanation of application and questions. Let me go through your materials deeply. It may take a while. I will give you some feedbacks by end of this week.

    -Wenhao

  • 0
    TI__Expert 5180 points

    Hi Ritul,

    1. From my point of view, this external circuit's main purpose is to extend start-up time and decrease inrush current. For solar cells supply, if without this circuit, inrush current of hundreds of mA or even several A will collapse or even short input power supply. If Thermopile used in your applications can support such inrush current without huge voltage drop, this external circuit can be omitted.

    2. For such low input voltage and small output current, I think TPS61200/1 is most suitable no matter whether the external circuit is used.

    3.The min start up voltage should be 0.5V.

    4. Yes, the efficiency at this condition is about 50-60%. I am afraid thermopile cannot afford current requirement. Please notice that the external circuit will also increase power loss, maybe 500mA thermopile is needed.

    Please also notice that TPS61201 cannot use this external circuit because it is fixed output voltage version and TPS61200 can be used.

    Best Regards,

    Eric Yue

  • 0 in reply to Eric Yue
    Prodigy 70 points

    Hi Eric,

    Thanks for the reply.

    1. OK

    2. When we connecting the load thermopile closed loop voltage 200mV to 400mV DC. Does TPS61201 support this input range?

    If not, Please suggest us best suitable part no.

    3. As mentioned point #2, requirement of thermopile open ckt. voltage approx. 750mV DC & closed loop voltage 200mV to 400mV DC. If you have thermopile based application note similar to our requirement, Please share it.

    4. We are working to reduce system load power requirement to meet thermopile electrical specification and exploring higher o/p current capability thermopile. Once we finalize this specification, We will get back to you.  

    Regards,

    Ritul

  • 0 in reply to Ritul Patel1
    TI__Expert 5180 points

    Hi Ritul,

    2. Sorry, as my point of view there is no suitable chip can generate 0.2V to 3.3V. Like previous reply, I think TPS61200/1 is most suitable for this application and the min input is 300mV. I am not familiar with thermopile, since thermopile is closed loop control, is it possible to be controlled between 300-400mV?

    3. I have no specific app note for thermopile power design. TI has an app note about Infrared Thermometer, maybe it can help you by some means.

    Designing a Low-Cost, High-Accuracy Infrared Thermometer

    Best Regards,

    Eric Yue