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Registered Member #816
Joined: Sun Jun 03 2007, 07:29PM
Location:
Posts: 156
Looks to be from the early era of switch mode design, no reason to suggest why it would still not work though.
Was trying to figure out what the little circuit to the top was for with the 741 and 555, looks as if its job is just to light an LED when it detects ripple voltage, either to give a reassuring indication that it still working, or to perhaps warn if the ripple on the output exceeds a certain value when a load is applied. Does that sound reasonable to everyone else?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Yeah, that's the only function I can think of for it.
Indeed, this is a 1970s antique but no reason why it wouldn't still work. Using a PNP BJT as the switching device makes drive very easy, no high-side driver chips etc. needed.
Registered Member #2838
Joined: Fri Apr 30 2010, 07:55PM
Location: tehachapi, CA
Posts: 333
Thanks guys! It is the only variable low voltage PWM circuit that I could find online... I'm thinking about giving it a try since most of the components are so cheap.
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TL494 PWM supply help 0-50v 5A
