The DC/DC Converter part I’m planning to use with my FAB1215 module is out of stock, and even if it comes back in stock, the supply quantity is so low… Mouser doesn’t keep a big inventory of this part because they said demand is low. Soooo, I can’t depend on this part being available for my customers, so I decided to roll my own DC/DC converter for +/-15V output.

Making the 12VDC to +15V output was easy, and initial breadboard testing showed it can deliver up to 370mA and more (up to 500mA). But making the 12V to -15V Inverter was a bit more problematic. The best I can squeeze out of it is -150mA, and only at 58% efficiency.  The good news is I think that should be enough for 1 or 2 channels for a V- rail.  The V+ rail will need to power additional LEDs and Relays so I want the V+ to have a higher current rating anyway. So I think we’re good.

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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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Yesterday, we got the boards back from the PCB fab house. Today, I built the FAB1215 prototype and tested it.  Now, we have a power supply to power all our FAB modules. Yay!

This convenient power supply is powered by a simple 12VDC power adapter (wall wart). The one I’m using is rated 400mA and it’s the only one I can scrounge around… but I’d recommend a 1Amp power adapter so you have plenty of power to spare.

The +/-15Volts is generated by an off-the-shelf part, and the +48Volts for phantom power is generated by our DC-1248 Module (12VDC to 48VDC converter).

The FAB1215 has (1) DC jack to accept the 12Volts input, and (2) IDC headers that route +/-15Volts, and +48Volts so you can power (2) channels of your project.  The +/-15V is rated up to 190mA, and the 48Volts is rated up to 60mA  (this 60mA figure may change once I finalized on the component values and complete testing).  You simply hookup power using 10-pin ribbon cables to your FABs. It’s that easy.

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I’ve been testing the DC-1248 (12Volts to 48Volts Phantom Power) the past few days now, and I was able to further improve performance by reducing ripple down to 128mV, for a 47.7Volts output, fully loaded drawing at 57mA.  Efficiency is computed to be at 76% at this loading.

I reduced the ripple by adding another 0.1uf ceramic and 47uf electrolytic capacitor to the DC-1248 output terminals.  Since there is no more space on the DC-1248 board (measuring only 1″x1″), I added these parts to our FAB1215 PSU Module.  So here’s the new Rev.B design.

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I got my prototype boards for my DC-1248 (12Volts to 48Volts DC-DC Converter).  Quickly built a prototype, and nervously turning on the power, there was no smoke, fyring bacon sound, or anything getting hot.  Yey! So far so good… Measured the output voltage and it was 48.2 Volts. Nice.

I began loading the DC-DC converter and looking at it’s ripple waveform on my scope. Happy to say that performance improved significantly just by moving it from a breadboard into a properly designed PCB!  The board is a tiny 1″x1″ square, with (4) Millmax pins so you can easily plug-it in to our FAB1215 Power Supply Board.

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