Lm3886 in BTL mode with 4ohms load and Smps.

[asbjbo]

Hey Blue,

I was already thinking in that direction.but didn't dare to make that statement here. Logically when 4 Ohms is connected in BTL mode then each half bridge sees it as a 2 Ohms which makes Wattage 2X and the same is the same thing happens at the other half bridge. so the total power is 4X.

Correct if my simple logic is wrong.

Yes, but only if the output stage can deliver the necessary current and the power supply can support that. In practice, you will rarely see 4X, perhaps something more like 3X.

Another way to think about it is in terms of voltage swing. You get twice the voltage swing across the load when bridged, and since P = U I, and I = U / R, then P = U^2 / R. So if the voltage swing doubles, the power delivered to the load quadruples. But the current also doubles, and it needs to go through both ends of the bridge, so each amp needs to support twice the current for the same voltage, which is equivalent to dropping the load impedance by half.

 

[Aucosticraft]

Yes, but only if the output stage can deliver the necessary current and the power supply can support that. In practice, you will rarely see 4X, perhaps something more like 3X.

Another way to think about it is in terms of voltage swing. You get twice the voltage swing across the load when bridged, and since P = U I, and I = U / R, then P = U^2 / R. So if the voltage swing doubles, the power delivered to the load quadruples. But the current also doubles, and it needs to go through both ends of the bridge, so each amp needs to support twice the current for the same voltage, which is equivalent to dropping the load impedance by half.

yes, I agree, I mean the ideal BTL amp & ideal Supply. ( just for understanding of concept).

 

[abraxalito]

Yes, but not what the answer really had to do with the question, then.

You've lost me here.

Somehow it doesn't come as a surprise to me that you would compare yourself to the heathen god of dreams Morpheus.

Actually to me it does come as a little surprising that you'd infer that I'm making any comparisons. But I'm getting the picture

Ah, no, you are talking Matrix. That is interesting, because I would be Neo in that comparison? The hero that needs your guidance? Sorry, neither the hero, nor the person who needs your guidance are roles I assume.

Yet you seemed content to assume the role of rebellious child in another recent thread in discussion with me. What is it that makes that role more attractive to you than the hero or the hero's student?

So when you ask questions, its just posturing? You really are not at all curious about the answer? That is how I take your words above 'nor the person who needs your guidance' in case you're wondering why. To further elucidate, Neo did not need Morpheus guidance, it was not a necessity. Rather he availed himself of the opportunity that presented itself. But that's really taking the words I quoted way too far as I inferred nothing more than what was in the words themselves - that enlightenment is not something that I can give you, you have to realise it for yourself. That is, assuming that you truly seek it - given your words above I see now that I might well have been wrong in taking your use of the term at face value.

If the efficiency is not important, why did you bring it up in post #41?

That's a debating technique that I recognise easily - the 'straw man'. Where did I say that efficiency is 'not important' ?

 

[pacificblue]

A lot of wishful thinking and a lot of hot air.