Does anyone know were i can get plans (for free) or info on Class D amps? I want to build one for an SPL car im making, so sound quality is not a huge consideration. The amp would only need to go to about 100Hz.
An seggestions would be greatly appreciated.
darn. Well, the Harris appnote was for the HIP4080A class-D amplifier chip that Harris (now Intersil) made. I remember reading it several years ago. When I get home I'll dig through my files, and hopefully the appnote is still there, because it provides a very good overview of class-D technology and all the equations you could stand regarding power output and efficiency etc...
I'll get back to you on this one. BTW, if anyone knows the datasheet and/or appnote I'm referring to, by all means post a link or something. I'd really like to have a copy of it for my archives (if i don't already).
Each chip manufacturer with a Class-D driver chip will usually have some application notes posted. Both TI (TPA005, TPA032 and TPA2000) and Cirrus Logic (CS44210) have Class-D amp chips; you might want to check out their web sites.
As for the schematics, this is a result of poor website configuration. The schematics are supposed to be password protected. Crest goofed. Very few companies make this sort of information available for free, especially on a brand new product.
If you're looking for anything under a few hundred watts, the controller chips are the way to go. If you feel that you need more power (into the KW range) then you'll have to use a descrete controller instead of a chip. The crest schematic is helpful in this area.
If you're looking for a general understanding of how Class-D amps work, I have a functional diagram of a full-wave (similar to bridged) Class-D amp on the web that might help. It's at 'http://www.games.accs.com/ER/wizards/thoth/class-D.gif'. WARNING: I'm not an EE, and haven't built a Class-D amp. The diagram is based on my understanding of Class-D amp circiuts I've seen, and could be wrong.
Tripath (www.tripath.com) has some interesting designs too, with PCB layouts and lots of information. The conception is different, but it will work fine for you. They are able to sell and send to you even a single unity of an IC, if you want.