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Class D Switching Power Amplifiers and Power D/A conversion

Soft Start Necessary?
Soft Start Necessary?
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Old 25th December 2008, 09:28 PM   #1
dtaylo3 is offline dtaylo3  United States
diyAudio Member
Join Date: Nov 2004
Location: coloradao usa
Default Soft Start Necessary?

I am going to build a two-channel amp with Hypex 180 modules. I have the two amp modules, the power supply and a great toroid I got from DIYCable.

How necessary and beneficial is the soft start module?
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Old 26th December 2008, 07:49 AM   #2
Anthony C Smith is offline Anthony C Smith  United Kingdom
diyAudio Member
Join Date: Jun 2005
Location: Sunderland
its realy a matter of safety; using soft start allows you to scale the mains fuse correctly, instead of "chucking in a value that doesn't blow"
manufactured product in europe has to comply with EN61000-3-2 (the flicker factor) which limits inrush currents to stop lights flickering, obviously diy is exempt.
the simplest method of inrush suppression is to use an NTC thermisor in line with the torroid, or two in series if the resistance you want is not available in the current rating you need. 10R is a good starting value for the USA, limiting current to 12.5A.
watch out how you mount these though they run hot (thats how the restance drops)
this type of suppression has one drawback, line dropouts do not allow them to cool and the fuse can blow as the mains dips out for a second and comes back!
Anthony C Smith MAES MinstSCE
-I think rain is wet so who am I to Judge-
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Old 26th December 2008, 09:05 AM   #3
classdphile is offline classdphile  Antarctica
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Join Date: May 2008
You don't have to be concerned with line drop-outs not allowing them to cool, it is likely that they won't be hot to begin with.
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