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Old 12th February 2012, 05:04 AM   #1
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Default Power supply protection circuit against main supply ?

I have no idea what this is called, but i found such description :
Quote:
Quoted from : Understanding, finding, & eliminating Ground Loops by Bill Whitlock
Power-line voltage normally consists of a broad spectrum of harmonics and noise in addition to the pure 60 Hz sine wave. The noise is created by power supplies in electronic equipment, fluorescent lights, light dimmers, and intermittent or sparking loads such as switches, relays, or brush type motors (blenders, vacuum cleaners, etc.). The drawing at right shows how sudden changes in load current caused by an ordinary phase-control light dimmer generate high-frequency power line noise. At high frequencies, a building's power wiring behaves like a system of mis-terminated transmission lines gone berserk, reflecting high frequency energy back and forth throughout the building’s wiring until it is eventually absorbed or radiated
Due to few days ago the main supply burst my DIY amplifier when I switch off my toilet bulb.... Previously it was only creating noise, but few days ago it fry one of my amplifier component
I'm curently searching for power supply circuit that comprise/incorporated protection/stabilisation for main supply "madness"described above.
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Old 12th February 2012, 05:13 AM   #2
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Its called a Mains EMI Filter. Sometimes if the mains line is very bad, a surge protection is also added to prevent the large voltage spikes from entering the amp.

Last edited by b1o2r3i4s5; 12th February 2012 at 05:17 AM.
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Old 12th February 2012, 05:29 AM   #3
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If i'm not wrong, EMI is disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. Of course my situation will produce some, but i don't think that is what I describe, and EMI is insufficient to blow my fuse and component in fraction of micro second...

is there any way to protect against it ? just don't like my amplifier destroy innocently....

Last edited by guitar89; 12th February 2012 at 05:31 AM.
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Old 12th February 2012, 05:47 AM   #4
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In your case, i think its a voltage surge created when switching mains devices so you may want to try adding a surge protector circuitry, it is usually done with a varistor.
Surge protector - Wikipedia, the free encyclopedia

This is likely to happen if you live in rural areas and the mains supply isn't very good.
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Old 12th February 2012, 05:57 AM   #5
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Use 265Vac varistors after main fuse, and assure it can handle for schortcircuit, a current bigger than main fuse.

If main supply have spikes, more than 265Vac, the varistor will act like an shortcircuit, blowing main fuse.

Better to burn a main fuse, instead an amplifier.
I think you have SMPS power supply of your diy amp.

If is normal trafo, is possible to give him too much supply, at normal main voltage (overvolt), and when main voltage raises a bit, is enough for the amp to fail...

Last edited by DjLeco; 12th February 2012 at 06:16 AM.
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Old 12th February 2012, 07:36 AM   #6
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well... it is using toroid trafo, power supply doesn't fail. The should able to withstand little bit of overvolt you mention. The amplifier also fails in a special way, that only one half of is destructed, another half didn't blow its fuse and components.

Is there any simple implementation of circuit ? If it is high frequency energy, is a zener/regulator & inductor enough to block/limit it ? would like to know what will those 2 component and varisotr installe at power supply will effect the audio quality ?
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Old 12th February 2012, 07:45 AM   #7
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this type of surge protection seems what i'm thinking : Series Mode (SM) surge suppressors
which consist of several of capacitor & inductor & resistor. But seems the cost is high, but i'm thinking to make it only for those spike of I had mention, not lightning thunder, so would reduce the cost alot I guess. Have no idea how to incorporate in circuits... hope someone would point out me how to do so.
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Old 12th February 2012, 11:24 AM   #8
AndrewT is online now AndrewT  Scotland
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Could the fast edge (rise time) of the transient, be causing the amplifier to become unstable and oscillate?

That would certainly blow fuses.
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Old 12th February 2012, 11:55 AM   #9
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hm.... not sure about it, but sure happen fast enough. Never happen before though.... I think of incorporating varistors in main circuit and secondary circuit, as well as incorporating filter which consist of caps, inductor, resistor. This should give a good stable supply of electricity under most condition, since it suppress spike and ripple, at the same time limiting surge by varistor.

After some reading, I found that the varistor is quite similar to zener diode.
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Old 12th February 2012, 12:22 PM   #10
AndrewT is online now AndrewT  Scotland
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suppress interference at source.
That way you attenuate both the radio waves and the electric current waves.
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