Re: SMPS, control loop?


"Clifford Heath" <no.spam@xxxxxxxxxx> wrote in message
news:4459845a$0$9697$afc38c87@xxxxxxxxxxxxxxxxxxxxxxx
Genome wrote:
Ahhhh, that means you would want to look at the most excellent

Most excellent indeed - I'm slowly working through it. But my
question - which you're also welcome to attempt - is why has
no-one apparently built an audio amp which *is* just an audio
SMPS straight off the AC power line?

I think that the main difficulty is that you need a bi-directional power
converter such that power can be transferred from input to output and also
returned from output to input. That sort of thing is done in non-isolated
converters but with a transformer in the way leakage inductance makes life
really difficult.

In a buck configuration you end up with the output inductor trying to drive
the transformer leakage inductance and that results in huge voltage spikes
across the switching devices.

On paper it looks possible, you have to implement some form of active
bidirectional synchronous rectification on the secondary side. In practice
you end up with energy recovery problems that might make the end result
difficult to achieve or overly complex.

Search for ampliverter in Google. There is a section in the DIY Audio Forum
where someone has a go at implementing one of these things.

There is a Unitrode application note somewhere that does something at low
powers for generating the ring voltage on telephone lines which uses a
flyback configuration.

DNA


.

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