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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 12th Apr 2018, 11:57 am   #1
Argus25
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Default IBM 5155 power supply

I have just completed a 21 page document on this switch-mode supply from the early 1980's. IBM did not publish data on it.

http://worldphaco.com/uploads/The_IB...WER_SUPPLY.pdf

It contains a range of different circuit innovations including surge limiters that use a PUT, current detectors with a current transformer, modulated base drive for the switching transistors with current feedback to improve efficiency.

One idea allows the use of a transformer with a 115V primary to be run from a 230V supply (for the 115/230V universal power input select circuit). It is a good method to synthesize what amounts to a low Z reference point that splits the incoming 230V mains in two. This idea would be suitable for running many small transformers in small 115V appliances from 230V without the need of a stepdown transformer and better than a series resistor or reactance as the method relatively independent of the load. It requires a bridge rectifier and two high value 200v electrolytic caps.
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Old 12th Apr 2018, 8:36 pm   #2
astral highway
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Default Re: IBM 5155 power supply

Quote:
Originally Posted by Argus25 View Post
I have just completed a 21 page document on this switch-mode supply from the early 1980's. IBM did not publish data on it.

http://worldphaco.com/uploads/The_IB...WER_SUPPLY.pdf

It contains a range of different circuit innovations including surge limiters that use a PUT, current detectors with a current transformer, modulated base drive for the switching transistors with current feedback to improve efficiency.
Hey Hugo,

That's another monumentally detailed piece of investigation, primary research and documentation. Thanks for making this contribution. I had never thought that viable, robust SMPS existed as early as this and it is high-powered and quite intricately thought out.

I looked at the overcurrent sense arrangements with particular interest. Really interesting to see the two conditions you describe:

*overcurrent AND

*final Vout, supply, > specified limits.

That's really ingenious. I also note the inrush limiting arrangement. I've never seen or heard of a programmable unijunction transistor before - really interesting to see an unfamiliar variant of a very useful circuit.

Cheers!
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