# Design of Single input DC - Mutliple ouput DC circuit

I am trying to build a circuit to drive different loads with different ratings. The block diagram below outlines what I am intending to do. Briefly,

• Block A: a circuit splitting power into +/-15V DC to supply op-amps.
• Block B: a circuit the supplies 1A DC to a 3ohms load.
• Block C: a circuit supplying 9V DC to a micro-controller

For the input supply, I am thinking about an adapter: 120VAC in, 48VDC, 1.5A out. Current rating could be different, e.g. 2A.

Any hints on what might be the best implementation of each block, is greatly appreciated. I do not think a voltage divider is a good one for blocks B and C.

• One more comment. The whole circuit is driven only by the adapter, i.e. no benchtop voltage supplies Commented May 18, 2017 at 12:35
• You are spec'ing a 75W supply for a perhaps 5-6W design? You will need to add the load currents for each power branch for a good answer. Commented May 18, 2017 at 12:44
• What's stopping you from using 4 power adapters and a power bar? Commented May 18, 2017 at 12:58

If you could manage with slightly different voltages, then a reasonable choice might be a standard ATX computer power supply, which has:

• ±12 V for your opamps. (Note: current capacity of −12 V may be small; I can't find a reference for the required minimum capacity, though.)
• +3.3 V, which is a little bit high for your 1 A through 3 Ω, but you could add series resistance.
• +5 V for your microcontroller, unless it's 3.3V logic. 9 volts is not a standard logic voltage, so it is likely the input to a voltage regulator on your controller board which you can just skip.

The advantage of this is that it is a single commodity part, rather than a collection of multiple converters or a custom design. (You'll still have to make a breakout board/cable for the output that would ordinarily plug into a PC motherboard. I did this by starting with a short extension cable as a readily available pre-wired connector, and cutting out the wires I wanted to use.)