• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 65 subscribers
  • Views 850 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS61220 for charging a battery from piezo electric source

jairam surya
Prodigy 50 points
Other Parts Discussed in Thread: TPS61220, TPS61220EVM-319, BQ25504, TPS61200

I am working on piezoelctric energy harvesting, am using TPS61220 to provide constant DC supply to the battery. The output from the piezo transducer is given to bridge rectifier which is in turn given to dc-dc converter and to which a battery is connected. For testing the dc-dc converter am using TPS61220EVM-319. The voltage am getting at rectifier section before the EVM is connected is 2-3volts but after connecting the EVM the input voltage is falling down and the output is never 3.3volts which is expected from the EVM. I am unable to find out the reason for this. Please suggest me if some modifications are to necessary. Thanks in advance. 

  • 0
    TI__Mastermind 36110 points

    Your source impedance is probably too high and can't provide the required power.  Try comparing waveforms between your design and when you use a lab power supply for the input to the TPS61220.  You might consider using the bq25504 for your energy harvesting application.

  • 0 in reply to Matthew Day
    Prodigy 50 points

    Yes sir the piezoelectric is unable to supply the sufficient power to drive the converter. Am able to charge a capacitor with the incoming piezoelectricity . When am connecting the charged capacitor to converter it is working fine. But when the capacitor is connected to converter and am trying to charge it , it is getting charged till 0.7 volts and getting discharged and again not able to get the necessary output. So i think some kind of switching mechanism has to be placed in between the capacitor and the converter which disconnects the capacitor when its voltage is low and should allow only after the capacitor has attained some voltage. Am thinking of placing a NMOS with its gate and source connected to the cap and drain connected to converter input. But NMOS transfers weak 1 so i think there may be some added loss due to it. Can you suggest me if there is any other way to achieve it . thank you. 

  • 0 in reply to jairam surya
    TI__Guru**** 150660 points

    The TPS61200 is a better fit for this application for three reasons.  It has an adjustable UVLO function.  This means that you can set the voltage at which the IC turns on.  So, you can store a lot of energy in your input cap and get it up to some high voltage, then turn the IC on.  It will then convert this stored energy to the output.

    Second, the TPS61200 can operate down to 0.3V on the input.  This allows you to run off of less input power when your source does not produce as much voltage.

    Third, the TPS61220 has a input to output connection through a diode that cannot be disabled.  Thus, the output is always connected to the input (through a diode) even when the IC is off.  This will likely keep loading your input source and not allow it to reach an appropriate voltage where you can operate.  The TPS61200 isolates output from input when it is off.

    All that being said, I would really recommend that you look at the bq25504.  It is an awesome part.