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Old 25th January 2013, 02:08 AM   #11
xyz9915 is offline xyz9915  Pakistan
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Join Date: Apr 2007
Originally Posted by nigelwright7557 View Post
I am not convinced it is a wide range mains input SMPS.

1/ It clearly says 220VAC on the circuit diagram.

2/ The 12 volt regulator needs at least 18 volts to function. So if it is 18 volts at 110VAC then at 240VAC it will be 39 volts which is out of spec for the regulator.
The 12v transformer power separately from 230vac to maintain voltage at regulator (not shown in the schematic)
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Old 25th January 2013, 02:10 AM   #12
xyz9915 is offline xyz9915  Pakistan
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Originally Posted by sreten View Post

The only sensible reason that would happen is if it has two modes.

Its not a problem if its normal operation.

rgds, sreten.
I want this circuit to work with a wide range of voltage (100v to 240v)
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Old 27th January 2013, 03:34 AM   #13
xyz9915 is offline xyz9915  Pakistan
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Join Date: Apr 2007
The Problem has been solved by replacing 0.1uF capacitor with 10uF capacitor at Pin9 (Compensation) of SG3525. Now the smps works from 100vac to 240vac.

Thanks to Everyone
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Old 27th January 2013, 01:31 PM   #14
dmills is offline dmills  United Kingdom
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Location: High Wycombe
That circuit is clearly not a univeral input supply, and I am somewhat surprised that it works at all at very low input voltage.

The canonical way to do universal input (And at 900W it is not a bad idea anyway) is to start with a power factor correction stage (a boost converter) to produce somewhere around 400V on the storage caps irrespective of the applied input voltage, then follow that with the standard isolated switcher curcuit. Note that PFC voltage control loops can get a bit tricky when the load is audio....

This is all non isolated power electronics so rapidly gets behond the proper scope of these forums.

73 Dan.
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Old 28th January 2013, 01:23 PM   #15
xyz9915 is offline xyz9915  Pakistan
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Although the smps works satisfactorily but can someone explain how a big capacitor fixed the problem because a big capacitor capacitor at Pin9 (Compensation) is not usual.
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