Maximising output power in battery powered application

[jeremiahrose]

Hey there,

I'm designing a portable sound project that runs on a 7-14V LiPo battery.

The TI amplifier I'm planning to use (the TPA3132D2) has a maximum output voltage limited by the supply voltage of the battery, but it can supply enough current for loads down to 1.9Ω, and my battery can supply practically limitless current.

The equation for power is P = V^2/R.

Does this mean that for a fixed battery voltage, the best way to get maximum power out of the amp is to use the smallest load impedance possible?

So if I have 8Ω speakers, I could put a transformer between the speakers and the amp to lower their apparent impedance to 2Ω and that would quadruple the output power?

Thanks in advance!
Jerry

 

[abraxalito]

Assuming no thermal limitations, what you've said is correct. The maximum power is achieved with the minimum recommended load impedance. However practical amps do encounter thermal limitations.

You certainly could use a step-up transformer to present a lower load impedance to the amp when using 8R speakers. Just watch for the leakage inductance of such a trafo - best use a toroidal.

 

[U130421]

You can step-up the power supply up to 36v with these boost converters . For 0.7$ each you can parallel them by adjusting precisely equaled voltage .
XL6009 DC DC boost module Adjustable output of power module Beyond LM2577 regulator module-in Sensors & Switches from Automobiles & Motorcycles on Aliexpress.com | Alibaba Group

 

[29285]

Nowadays it is much cheaper to step up the DC-supply voltage to the desired level than transforming the audio signal.

 

[jeremiahrose]

Thanks everyone, that's a great help.


I was hoping to avoid the complication of laying out a PCB for a second boost converter, but it looks like that is indeed the approach that all modern battery powered systems take. Good quality audio transformers from Cinemag are indeed expensive costing upwards of US$50 per unit plus $20 shipping. This is for their off-the-shelf designs, god know how much a transformer with a custom turns ratio would cost.

 

[JMFahey]

1) so what´s your actual voltage? 7V or 14V? Not the same.

2) what is the battery capacity in A/H?
That puts a realistic top on what can you actually pull from it.

Please answer this to get realistic answers, otherwise it´s a guessing game.

 

[imbra]

I had a similar problem with a TPA3136D2 amp I started working with. It wasn't loud enough, so I ended up getting batteries with higher voltage (6 cell LiPo) and a more powerful amp (TPA3220). I don't know if that is possible in your case, but it turned out very nice.