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TPA3221: Need help about Audio amplifier system failure

Part Number: TPA3221


I'm designing an audio public address system, where I use TPA3221 for amplifiers. I attached my design below.
At the output of the amplifier (Port OUT1+ / OUT1-), I connect to a matched audio transformer (this model:
Out+ connect to "4 Ohm" terminal, Out- connect to "Common" terminal. But when I power up the PCB with 24V supply, PVDD pin get smoke and burn out very quickly. (at that moment, the secondary side of the transformer is
left open). I tried with another PCB but It work for few minute and fail again. (I attached failure PCB picture below) (If I connect output of this amplifier directly to a high impedance horn speaker (don't use audio transformer), It work ok (but with 24V supply voltage, the speaker (high impedance, horn speaker) cannot operate at rated power)
Could you please recommend me a solution to this problem? any mistakes in my PCB? Is it correct when I use this design with that transformer to get a 70V line system ?

 Audio Amp.rar

  • Hi Le

    thank you for you question. 

    can we take a try below several issue.

    1. remove the RC filer after LC filter. 1uF seems too large.

    2. transformer hasn't connect the load, am i understanding right? voltage fluctuation might be large if there is no load.

    3. BTL is used, am i correct? BTW, can you show me how you connect the transformer, it seems like no that circuit in your attachment.



  • Hi Jesse

    Thank for your reply.

    1. I will try this and talk to you latter. 

    2. It fails both when connect or not connect to the load. when have load, it work for a few minus

    3. No, I don't use BTL. Just use one channel of TPA3221

    My connection as below

  • Do you have any recommend further? I don't want to fry another PCB to test remove RC filter Head bandage

  • I tried remove RC filter as you recommend. But it still fail.
    Is there any limitation of output inductant or output impedance of TPA3221? I have just got an old transformer with smaller power capacity and it work fine with my PCB. But when I connect to that transformer (EA75 of edcorusa), my PCB smoke imidiately.

    Is there any solution to work with EA75 transformer? 

  • Hi Le

    sorry to hear that.

    From amplifier side, there is no that kind of limitation for output inductance.

    how much current will be consumed when connecting EA75 transformer.

    if the current is too large that exceed OC threshold very much, and the time is also very short that even oc cannot react immediately.

    it might be the reason why amp been burned.