Hi Peter and guys.

What is the most difficult part with PWM type of DC-AC with transformer
converter design? Either regular PWM or some sort of magic sine waves.
(minimal efforts to receive optimal output sine wave with minimal
distortions)

Negative feedback in addition thru say some opto couple to make sure that
output AC signal is sine and required voltage and frequency.

Probably main problem is to drive high current into primary windings
but with on/off type control it will actually save you on heatsink
and will increase? converter efficience as well.

Anybody was successfull with doing this type of design with PIC ?
(different than class B)

WBR Dmitry.


"Peter L. Peres" wrote:
>
> On Sun, 16 Feb 2003, Olin Lathrop wrote:
>
> *>> When PWM is used normally there is no tap, and either a half bridge or a
> *>> full bridge drive is used. Switches are cheaper than transformers. There
> *>> are some designs with tapped transformers but the core space is used
> *>> inefficiently like that.
> *>
> *>I agree this sort of scheme can be very effective, but is less forgiving
> *>and more tricky to get right.  I've seen professional power supply
> *>engineers take months to get something like this just right.  They
> *>eventually did and it was a successful product, but it might not be the
> *>best path for a one-off home built unit.  A lot of things get simpler once
> *>you buy into the big fat 60Hz power transformer, although the unit cost
> *>will be higher.  I figured this wasn't so important if you are only
> *>building one unit.
>
> That is what I had in mind when I said the 'easy' way is the class B
> amplifier type driver.
>
> *>> Class B is rated 70% efficient (at 5% or 10% distortion - I do not
> *>> remember).
> *>
> *>The maximum theoretical efficiency for a sine output from a class B output
> *>stage is 1/sqrt(2) = 71%.  This assumes that the output is a pure sine
> *>wave (no distortion) with the peaks driven exactly to the power supply
>
> The distortion I had in mind was crossover distortion. Which can disable
> carrier current communication (don't ask how I know this).
>
> Otherwise I agree with you. The 'rounded square wave' could be a solution
> since he only needs to drive his controller and the air circulation
> blower. Maybe it would be enough.
>
> Peter
>
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