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DC/DC Switching Power Supply with Post Linear Regulators – FAB1515 Rev.B Design

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FAB Modules, FAB1000 Power Modules
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I got my prototype boards for my FAB1515 (Rev.A) Power Supply Module. I built a prototype so I can finally evaluate and test it.  I know the V+ section and V- section works independently on the breadboard. But this PCB design combines the V+ and V- section (and also adds a 48V section) and I’m not sure how all of these DC/DC converters will interact with one another (since they will be all powered from the same 12V DC source).

After building the prototype, I hooked it up to my DIY Electronic Load, oscilloscope, and (2) bench meters. One of the bench meter monitors the Voltage output, and the other one monitors the current load.  The oscilloscope monitors the DC output and ripple, and the Electronic Load allows me to vary the current draw from a few milliamps to hundreds of milliamps.

Right away, I noticed some problem… the V+ section voltage reading was jumping all over (15.1xx to 15.2xx and higher ) and wouldn’t show a steady number on my voltmeter.  Based on experience, I know the cause of this is a too high ripple voltage.  Looking at the oscilloscope confirmed my fears… the ripple voltage was very high… too high… approaching 500mV. This is CRAP! The V- section was also exhibiting high ripple voltage, though not as high as the V+ section… but still, it was high, around 300mV.

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FAB1248 Testing – 12Volts to 48Volts DC/DC converter

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FAB1000 Power Modules
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I made some tests using the final component values for our FAB1248 DC/DC converter.

Using a 12Volts DC input, phantom power voltage output remained constant at 47.90Volts, up to 47.84Volts at various loads and current draw.

For example, at 57mA current load, voltage output measured is 47.87Volts, with 152mV ripple according to our oscilloscope. This translates to about 0.31% ripple!  Ripple frequency has a period of 6.07us, or 164.7khz.

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FAB1215 – Parts Sourcing Problem

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FAB Modules, FAB1000 Power Modules
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Mouser.com put a crinkle on my plans when I learned that one of the part I need for my FAB1215 is out of stock. There’s (22) pcs on order, but they won’t become available until May…. so all in all, it’s not looking good… Mouser may just stop carrying this part suddenly.  I emailed them asking about their future plans for this part, whether they’ll be continuing to carry it or not.

 

Sample FAB Setup – Power supply and other stuff

 

 

 

 

 

 

Here are some photos showing the FAB1215 Power Supply Module powering some FAB modules via a ribbon cable.

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48Volt DC Converter plugin to our FAB1215 Module

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FAB1000 Power Modules
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Here’s a photo of our FAB1215 Power Supply Module, outfitted with our DC-1248 (+48V converter module).

I finally got the chance to test the 48V power supply by hooking up our FAB2010 XLR Input Module, FAB2110 Input Transformer Module, and FAB3010 XLR Output Module, using them as a pass-through before going into an API 512C preamp.   But instead of turning on Phantom Power on the API preamp, I used the 48V source on our FAB module.

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