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TPA3111D1: Part works very well except for intermittent start-up with a dc output that self-corrects to zero after 10 to 20 seconds.

Allen Blalock
Prodigy 20 points
Other Parts Discussed in Thread: TPA3111D1, TPA3111D1EVM

Our application uses the TPA3111D1 class D audio amp as the heart of an ac current generator operating in the low to mid audio band. After running for several seconds, the current source produces virtually zero dc output component. The output ac current range is up to 5 amps rms into less than 1 ohm. Any dc component in the current-source output is problematic within the application even if short-lived.

Is there an optimum start-up sequence for the TPA3111D1 to minimize the magnitude of  initial differential output dc? I.e., is there a start-up method that prevents the TPA3111 output offset-correcting integrator from initially producing differential output dc offset error?


Best Regards,

Allen

  • 0
    TI__Expert 5000 points

    Hi, Allen

               What is the PVCC value you use? The Load is 1ohm, are you play a continuous sine wave with large output current (>3.5A) .  Could you share the schematic (I only need the part for TPA3111D1)?

  • 0 in reply to Peter Cao
    Prodigy 20 points

    Thanks for the reply, Peter.

    We are running PVCC at 9 volts. We've added an external H-Bridge to provide the needed current gain for driving 5 amps rms periodic sinusoidal waveform into less than 1 ohm load. The lower the PVCC voltage, the higher our efficiency and the lower the compliance voltage of the current source application.

    The TPA3111D1 in our application is connected similar to the Figure 3 schematic of the TPA3111D1EVM Audio Amplifier Evaluation Board user's guide.


    Best Regards,

    Allen

  • 0 in reply to Allen Blalock
    TI__Expert 5000 points

    Hi, Allen

                I am sorry we can't provide more help if we can't see the schematic you use. It is a little strange behavior for ClassD.

    Peter Cao

    peter-cao@ti.com

  • 0 in reply to Allen Blalock
    Genius 3295 points
    Hi Allen,

    Is there any reason you can't AC couple the output of the amp to your H-Bridge? This would remove all DC; you'll need some really good caps...

    Mike Tripoli