• State TI Thinks Resolved
  • Locked Locked
  • Replies 15 replies
  • Answers 7 answers
  • Subscribers 32 subscribers
  • Views 1552 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.

TPA3110D2: output calculation for audio amp

user021864
Intellectual 2145 points
Part Number: TPA3110D2

Hi, 

May I ask that how can we calculate the output power for the audio amp? 

And if there are any document is discussing about this. 

the capture output of amp is shown in attach, please let me know if there are a better way. 

.

Thank you

  • 0
    TI__Genius 10830 points
    Hello,

    We have noticed your post and another teammember will feedback to you soon.


    Dylan
  • 0
    TI__Mastermind 24835 points

    Hi Pei-yuan,

    Do you have AP instrument(https://www.ap.com/)? It's very easy to measure the output power by this insturment. If it's not available, you could also measure the RMS voltage(U) on the load(R) by multimeter and calculate the power by U*U/R. Obvioulsly the second way is only a raugh measurement.

    Best regards,

    Shawn Zheng  

  • 0 in reply to Shawn Zheng
    Prodigy 160 points

    Hi Shawn Zheng,

          I plan to use a RC filter (1K ohm & 4700pF) on output than I will get a sine wave, based on this sine wave, I can measure the RMS and calculate the power, is it a precision result?

    webber

  • 0 in reply to Webber Chang
    TI__Mastermind 24835 points
    Hi Webber,
    I guess you are applying a sinewave on the AMP input. If you want a sinewave on the output, please use 22uH+0.68uF for FB5/FB6+C117/C169. With ferrite bead + cap in the output filter, you can't see the sinewave.
    Please use AP instrument to get accurate power measurement. The multimeter only gives rough result.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 160 points

    Hi Shawn,

        Thanks for your help, I have other questions, please refer to below

    1. The output power are the same between L+C filter and Bead+Cap filter, am i right?

    2. Due to I don't have 22uH, I would like use 15uH+1uF(fc = 41.1KHz) or 33uH+1uF(fc = 27.7KHz), please advise one is better? thanks.

    webber

  • 0 in reply to Webber Chang
    TI__Mastermind 24835 points
    Hi Webber,
    Please find my answer below:
    Q1: it depends. The sum of power comsumption on the output filter(LC or bead+cap) and the load should be close. But we only care about the power consumption on the load. So the power consumption on the load could be different between the two cases. One simple way for bead filter is to measure the RMS voltage value on the load and calculate the power consumption by U*U/R, as I mentioned above.
    Q2: For 1kHz input signal, they are both OK. Usually we prefer ~40K BW LPF for the output filter.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 160 points

    Hi Shawn,

        Regaridng measure the RMS voltage value on the load by multimeter, I will use the method like below photo, Am I right?

    webber

  • 0 in reply to Webber Chang
    TI__Mastermind 24835 points
    Hi Webber,
    Your understanding is correct.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 160 points

    Hi Shawn,

        Based on the test result, I can't use only Plimit to set output power, I had to limit input voltage together, for example,

    Plimit is 2V means output is around "5W", amp gain is 20 dB, Load is 4 ohm

    If input P-P is 3.44V, output RMS at load  is 6.9V-->output is 11.9W (over Plimit's setting, it's not acceptable)

    if input P-P is 1.4V, output RMS at load is 4.29V-->output is 4.6W  (it's acceptable)

    I assume that I had keep input in some range to make Plimit is working,

    Is there any formula to calculate which input is reasonalbe?

    thanks

    webber

    TPA3110D2 schematic.pdf

  • 0 in reply to Webber Chang
    TI__Mastermind 24835 points
    Webber,
    Please don't use the data in the Table 2 directly, it needs the totally same setup. You can calculate the voltage on the PLIIMT pin by the formula in the section 9.3.4 in the datasheet. From your SCH and description, you are using 12V PVCC and 4ohm load. right? So the voltage on the Plimit pin should be around 1.6V, but you could fine tune it.
    Please be noted that the PLIMIT fucntion is a very rough protect on the speaker. It only limits the virtual power rail to limit the output power. You have to limit the input signal amplitude to protect the speaker.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 160 points

    Hi Shawn,

         Could you teach me how to calculate the reasonable input signal amplitude? due to I don't have the AP instrument, I am thinking the actual output should 90% of speaker capability for protect it , for example, max output is 4.5W for 5W speaker, do you agree with me? thanks.

    webber 

  • 0
    TI__Mastermind 24835 points
    Hi Webber,
    If AP instrument is not available, please use multimeter to estimate the output power.
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 160 points

    Hi Shawn,

         Got it, thanks.

    I want to study how does the speaker working with filter free audio AMP, i am interested the speaker working without sine wave, could you share some related document? thanks.

    webber

  • 0 in reply to Webber Chang
    TI__Mastermind 24835 points
    Hi Webber,
    The ferrite beads filters are actually used for EMI supression, which means that the speaker can work normally without the ferrite beads.
    The speaker includes large indcutance itself, so your can still hear the sound by connecting the AMP output to speakers directly.
    Here is a document about LC filter design, hope it helps your understanding: www.ti.com/.../slaa701a.pdf
    Best regards,
    Shawn Zheng
  • 0 in reply to Shawn Zheng
    Prodigy 160 points

    Hi Shawn,

        Got it, thanks.

    webber