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TPA3255EVM: Maximum power

Mustafa Acun
Prodigy 20 points
Part Number: TPA3255EVM
Other Parts Discussed in Thread: TPA3255

We are trying to drive Shaker with the TPA3255EVM board.

We tried to BTL output configuration. We measured 5.6 A at the output and 75 g at the Shaker.

   

We tried to PBTL output configuration. We measured 5.6 A at the output and 50 g at the Shaker.

   

When we tried SE configuration mode, we measured 5.6 A at the output regardless of the input signal. We did not connect the capacitors visible in the figure below. Could we have experienced this problem because we did not connect the capacitors?

   

What is the configuration where we can get the maximum power for a single load?

  • 0
    TI__Genius 15440 points

    hi

    that cap is for blocking DC at the output.

    for single-end output, it is necessary. otherwise, the speaker might cannot suffer the DC voltage.

    for there is DC bias, the output become easy to clip which make the output cannot get the max output power.

    about your question, what is the meaning of 50g, 75g, you mean weight? or watt?

    tks 

    jesse

  • 0
    TI__Genius 14640 points

    Hello Mustafa,

    The highest output power is in PBTL the TPA3255 can push up to 600W into a 2 ohm load. Please refer to Page 28 in the datasheet on the schematic configuration and make sure you modify the necessary mode selection pins.

    best regards,
    Luis

  • 0 in reply to Jesse Ji
    Prodigy 20 points

    By "g" I mean gravitational acceleration. 

    I was expecting to get the maximum power in the PBTL configuration but it didn't work.

    I wanted to try the SE configuration but I couldn't succeed. There is an input signal connection, while the amplitude of the input signal is 0V, we measured 5.6A at the amplifier output.

  • 0 in reply to Mustafa Acun
    TI__Genius 15440 points

    hi Mustafa

    let us clear something about your configuration.

    1.your load is not the speaker, it is Shaker, i am not very clear what it is, do you know the load resistance for the Shaker.

    2.what is your pvdd voltage, driving large power, also need large pvdd power supply. 

    3.when you input is 0v, you can get the output current is 5.6A, can you measure the output waveform, then we can check what kind of signal is outputted.

    tks

    jesse

  • 0 in reply to Jesse Ji
    Prodigy 20 points

    Hi Jesse,

    1.The load resistance of the shaker is approximately 8 ohm.
    2.We see a maximum of 44 V at the amplifier output.

    3.I haven't analyzed the output wave yet, but I will.

  • 0 in reply to Mustafa Acun
    TI__Mastermind 40190 points

    Hi Mustafa

       Your PVDD voltage and load resistance is limiting the current. The maximum possible peak current you could get, is 44V / 8ohm. No matter what circuit you are using, the current can't be larger.

  • 0 in reply to Shadow He
    Prodigy 20 points

    Clearly in our last tests we saw 70 V at the amplifier output but the current is 2A.
    As far as I understand we can get max 300 W for 8 ohm load resistance.

  • 0 in reply to Mustafa Acun
    TI__Mastermind 40190 points

    Hi Mustafa

      The supply voltage is only 44V, right? The 70V, do you mean the Peak to Peak voltage? We may need to use RMS value for both voltage and current to do the calculation.

      The device doesn't have method to limit the current. If you see the current is smaller than expectation, it's quite possible your load value is not 8ohm.

  • 0 in reply to Shadow He
    Prodigy 20 points

    Hi Shadow

    At the output of the amplifier for the Shaker supply we saw mostly 44 V and appr. 6 A. It is RMS value.

    These are my test results.

    Configuration Input Output g (Max) Amp. A(RMS) Shaker A(RMS) V Input (V)
    BTL SE DE 84 4,16 - 44 4
    BTL DE DE 97 5,13 - 44 2,5
    BTL with blower DE DE 102 5,74 - 44 2,5
    BTL with blower SE DE 97 - 6,21 44 3
    PBTL with blower SE DE 94 - 6,12 44 3
    PBTL with blower DE DE 101 - 6,5 44 3

    The load resistance is approximately 8 ohms. There is a contradiction here, but we haven't found out why.

    • Total Output Power at 10%THD+N

    – 315-W Stereo into 4 Ω in BTL Configuration

    – 185-W Stereo into 8 Ω in BTL Configuration

    – 600-W Mono into 2 Ω in PBTL Configuration

    • Total Output Power at 1%THD+N

    – 260-W Stereo into 4 Ω in BTL Configuration

    – 150-W Stereo into 8 Ω in BTL Configuration

    – 480-W Mono into 2 Ω in PBTL Configuration

  • 0 in reply to Mustafa Acun
    TI__Mastermind 40190 points

    Hi Mustafa

       The datasheet value is tested with a pure resistor, and if you are using a real resistor to test, should able to get the same data. When 44V RMS output you get, and 8ohm load, the current would be 5.5A. If the current is different, it means your load is not precise 8ohm.