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Old 18th July 2009, 09:48 PM   #1
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Default Interest Check: 15A Unreg PSU

I decided to design a higher current (15A max) unregulated power supply for my BR100 amp. If enough people are interested, I'll do a group buy. The cost will depend on the number of boards ordered, but the most the boards will cost is $30 each (they're big at 7.85" x 3.45").

The diodes can be MUR1520 or any TO-220 diode with the same pin configuration. The reservoir capacitors can be 2-pin or 4-pin snap in with 10mm or 22.5mm lead spacing and up to 40mm diameter. There are also positions for 5mm, 7.5mm and 10mm film capacitors and snubbers, as well as bleeder resistors. There are 4 ground connections to make it easy to connect to either a center-tap or dual secondary transformer. I'll be using 2oz copper and the narrowest traces are 254 mils wide.

Suggestions on the design will be entertained as well.
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Old 18th July 2009, 10:05 PM   #2
PH104 is offline PH104  United States
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I'd buy a few boards.
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Old 21st July 2009, 11:49 AM   #3
AndrewT is offline AndrewT  Scotland
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How did you arrive at the 15A capability?
Is that Irms (=ac) or Ipeak or Itransient?
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Old 21st July 2009, 12:29 PM   #4
h_a is offline h_a  Europe
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Andrew, your answer is simply the tracewidth of the pcb-artwork.

For your pleasure,

http://circuitcalculator.com/wordpre...th-calculator/

Have fun, Hannes
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Old 21st July 2009, 02:56 PM   #5
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That is one of the calculators I used. According to one, the width and thickness was acceptable for 10 degrees rise over ambient, and the other for 12 degrees rise over ambient. I also exceeded the minimum recommended gap of 30 mils for a 35V difference.

I'm not sure what the difference between Ipeak and Itransient is. I understand transient, but by peak do you mean DC? If so, then that would be the one.
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Old 22nd July 2009, 08:22 AM   #6
AndrewT is offline AndrewT  Scotland
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It sounds like you are in the dark as much as me when trying to define the output current ability of a standard PSU.

Why don't you call it a +-20mF PSU with integrated rectifier and snubber?
What size of components has the PCB allowed for?

BTW,
the two Ground connections at the input end are not required.

The output end goes to the main Audio Ground. There is no other Ground connection to the PCB.
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Old 22nd July 2009, 11:12 AM   #7
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The component sizes are in the first post. I plan on using 4x 15mF caps in my implementation, but it'll support a lot more than that (+-112mF 35V, or +-78mF 50V with a quick check of what Digikey has).

As for ground, I was thinking one for connection to PE, one for connection to center-tap (if using such a transformer) and two outputs for connection to two amp modules. Would it be better to have the grounds connected at an off-board star?
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Old 22nd July 2009, 11:50 AM   #8
AndrewT is offline AndrewT  Scotland
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If you use a centre tapped transformer then connect the centre tap to the output end or between the caps not at the rectifier end.
If you use twin secondaries connect the zero volts at the output end to the main Audio ground.
You do not need the input Ground on the PCB. That simply copies what folk put in schematics, it is not how to wire up the real PSU.

4 * 10000uF = +-20mF
4 * 15000uF = +-30mF

which is quicker to type?
which is more informative?

I see it now, 40mm diameter.
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Old 22nd July 2009, 12:22 PM   #9
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Okay, I'll update the ground connections. Thanks for the help
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Old 22nd July 2009, 12:58 PM   #10
h_a is offline h_a  Europe
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Hi Redshift,

shift the snubbers close to the rectifiers, that's where they belong

You may also want to rethink the bypasses at all, bypassing (or decoupling) belongs onto the amp-board.

Have fun, Hannes

PS: by the way, maybe you want to think about thermals as well, otherwise be warned that pads in big copper planes are a pain to solder and need terrific temperatures usually.
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