Re: 9VAC from 5VDC?

On 9/14/2013 12:43 AM, john/lori wrote:
> Jim Brain wrote:
>>
>> That's fine, but I do think I can provide a pretty nice sine wave 
>> approximation to the transformer.  Either way, my sticking point is 
>> the transformer selection.  Any links to a suitable offering?
>>
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>>
>
> The advantage of doing the DC > AC after bumping up the voltage
> is that you can run the voltage converter at a much higher
> frequency and use a much smaller transformer.
> Also voltage drops will be a smaller percentage (if you're
> doing eg PWM)
I understand, but at some point, I'm just designing a PSU.  I see lots 
of 5VDC @ 60W or 80W PSUs online for cheap, and anyone can buy one.  
That takes care of one voltage, if I the circuit can make the other.  
And the PSUs are CE and UL-listed, or at least some are, and they are 
switchers, so they can be plugged into anything 90V to 260V.

>
> How'd you get 5 Amps ?
9VAC RMS @ 1VA = 12.73V Peak @ 1A.

Creating that from a single side PSU will require ~25VDC @ 1A

That's 25W

That's 5A @ 5V

If I do as Bil suggests, and use a center tapped Xformer, then the 
voltage need only be 12.5V @ 1A for each half cycle, or 12.5W which is 2.5A

Maybe it's 2.5A regardless, but AC is not my strong suit.

Jim


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