15W Amplifier Circuit Build - Help Needed

[Mike75]

Hi,


I’m seeking advice on a diy portable speaker project. I would like to power a single ~15W speaker driver with a battery and custom built amplifier circuit. I have a basic knowledge in electronics but also have the help of a friend for tinkering/assembly.


I’m looking for a combination of efficient amplifier IC and a circuit that will allow for the longest possible battery life.


I’m thinking of using a series of 3.7v Li-Pol batteries in order to supply the power needed (I presume to be around 12v).


A few queries I have (though there may be others I have yet to think of) are:


-What would be a suitable 15W amp IC with lowest possible power consumption.


-The best way to step up the battery voltage to reach the Voltage input for the amplifier.


-The best way to integrate the battery/ies for charging at 5v and discharging at 12v.


-Any other tips in creating a simple and efficient circuit design.


Thanks in advance,

Mike

 

[Tekko]

You cannot build a class d amplifier unless you have good knowlege in the RF field, unless you go for a premade kits that you just solder together, such as the kits on 47hz.com

 

[Mike75]

Hi,

Thanks for the reply. My friend has a fairly good working knowledge of electronics and will be able to help out when it comes to things like RF field.

I am looking to build form scratch and would appreciate any pointers in the right direction.

 

[Neil Davis]

Hi,
Thanks for the reply. My friend has a fairly good working knowledge of electronics and will be able to help out when it comes to things like RF field.

I don't agree with the comment about needing good RF knowledge. RF emission or susceptibility is just not a major problem in the 15W class D range, particularly for the newer "filterless" chips. You are going to be keeping wires short in a portable device, so radiation will be minimal. You might need simple choke filtering if the wires to the speaker are long, but all of the chip vendors provide adequate guidance that obviates complex RF engineering.

You would do well to look at this thread: http://www.diyaudio.com/forums/class-d/190571-purpose-built-boominator-pcb-project.html. This thread covers all of the issues for a portable boombox design--there is a lot of good info. The ADAU1592 amp in that thread is no longer available, but the design can be adapted to use ADI's current offering--the SSM3302, or else use one of the new TI or Maxim chips.

I've got a board that has part of the circuitry you need: it has the DSP (ADAU1701) and two SSM3302 chips (for stereo active 2-way speakers). It works, and right now I'm in the long process of finalizing the software to manage the ADAU1701. The board doesn't have the battery charging or solar cell management circuitry, so it doesn't solve your problem. Also, it's got a microprocessor that monitors the chip temperature and programs the ADAU1701, and interfaces to a PC, so it has complexity you don't need to deal with. But you can see how simple the amp circuitry can be--the four power amp channels are those two chips at the bottom of the board.

The SSM3302 is a good choice for your project because of the high efficiency and low distortion. However, it is a little pricey. If budget is a concern then the TI TPA3110 series of chips could do the job. Or look at the Maxim MAX98400 chips. Also, Sure electronics has those low-cost TPA3110 boards ($9 at Parts Express) that would work well for this application.

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[Tekko]

And twisting the speaker wires also reduces radiated EMI with these "filterless" class d ic's.