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Current Sensor Peak Detection is Not working

aviral mishra
Prodigy 30 points
Other Parts Discussed in Thread: TINA-TI, OPA347, TLV9062

I am sensing current using ACS712-20A version with i/p frequency of 23Khz, that is working fine, 

now i am trying to detect peak of ACS712 Sensor Vout using OPA as peak detector but i am getting some strange o/p from OPA as Peak detector, 

Please help me out.

Here i am attaching few screen shots of CRO Readings, and Schematic.

  • 0
    TI__Genius 15410 points

    Hi Aviril,

    For the peak detector to work I believe you will need something to "hold" the peak voltage at the output of the op amp. This is typically done with a capacitor.

    I recommend taking a look at Figure 49 in AN-31 for a recommended peak detector circuit. In the document you can download the simulation file by clicking the work "schematic" below the figure to open up a pre configured TINA-TI file so you can simulate the circuit. This gives a good starting point in designing your circuit.

    After simulating if you are still having issues please send us some scope shots of your measurement with each channel in the scope shot labeled (Vout, Vin, etc.) and also please provide the TINA file you used to simulate (if you have it).

    Thank you,

    Tim Claycomb

  • 0 in reply to Tim Claycomb
    Intellectual 755 points
    Hi Tim,
    In the final schematic, we have had added a capacitor of .1uF 50v but the response seems quite the same. Is there any chance that the OP347 circuit that we have drawn does not suit this application.
  • 0 in reply to Tony Philip45
    TI__Genius 15410 points

    Hi Tony,

    Does your schematic now match what is shown in AN-31? If not, please provide the schematic. 

    I put the OPA347 into the circuit shown in AN-31 into TINA-TI to simulate and I get the expected output in simulation. Have you tried simulating your circuit? If so, can you attach the simulation file? 

    I have attached the working peak detector circuit using the OPA347 for your reference.

    Thank you,

    Tim Claycomb

    OPA347 AN_31 Peak Detector.TSC

  • 0 in reply to Tim Claycomb
    Prodigy 30 points

    Hi,

    I have tried the same circuit (That you referred from AN-31, FIG 49),  but is still not working as peak detection

    Here i am attaching the schematic diagram, please have a look.

    I/P Parameter 230V, 110Amp Peak to Peak, 20khz freq.

    Thanks

  • 0 in reply to aviral mishra
    TI__Genius 15410 points
    Hi Aviral,

    The schematic appears to match what is shown in AN-31. Can you post oscilloscope shots of your input, output and supply voltage?

    Can you apply a 2Vpp sine wave signal to the input of the peak detector? Then please post oscilloscope shots with the known input signal. This helps eliminate the input signal as a potential source of the issue.

    I also recommend adding decoupling capacitors to the TLV9062 if they are not already there.

    Thank you,

    Tim Claycomb