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From: John Woodgate
Subject: Re: AC/DC Inverter
Date: Sat, 16 Nov 2002 07:49:37 +0000
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Sat, 16 Nov 2002 12:16:53 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Shane
wrote (in ) about 'AC/DC
Inverter', on Fri, 15 Nov 2002:
> It was
>suggested that I use a small black and white television they had
>kicking around you a load. It's rating is 75 watts. Now with the t.v
>rectifying internally maybe a squarewave would work. My main concern
>is the affects of the square wave on the t.v transformer. Would there
>be any adverse affects like the transformer heating up?
Does it actually have a mains transformer? If it does, yes, it will get
hotter than it should. But any TV (any d.c. power supply, in fact) is a
vicious load for an inverter. It will draw current in pulses of peak
value of 4 or more times the r.m.s value.
For 75 W, a power oscillator is perfectly feasible AND you could do it
easily in 8 months. If you give it a higher current capability than the
voltage and 75 W would indicate (like good hi-fi amplifiers have) it
would even run the TV. The only penalty is that the efficiency is not as
good as you would get with a far more complex switching ('Class D')
In fact, if you were to buy an OMP power amplifier module, you could
probably modify it to use the (rewound) mains transformer as the output
transformer and have something working is a week or two. You would just
need to add a low-power 50 Hz oscillator, rather than trying to make the
amplifier itself oscillate at 50 Hz (but you could also do that).
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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