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First of all, is there a name for thse kind of converters for easy searching?

There are some voltage adjustable DC to +-5-24V DC converters on eBay but they can't handle more than few hundred milliAmps. I need a +12V 1A output and -12V 0.5A output from a single 12V or 19V source.

Are there similar bipolar DC converters but for slightly higher currents or do they have to be made from several readily available components or even custom circuits?

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  • \$\begingroup\$ You can get Voltage inverters (I think that is what you mean) where you supply it with a positive voltage and it will output a negative voltage (such as input +5V, output will be -5V). Such ICs like the LMC7660 will do that. \$\endgroup\$
    – MCG
    Commented Jan 12, 2018 at 8:39
  • \$\begingroup\$ If you need more than a few hundred mA, it's better to boost the input voltage first, then create a virtual ground. That way, you have that virtual ground more stable in the center. \$\endgroup\$
    – Janka
    Commented Jan 12, 2018 at 8:40
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    \$\begingroup\$ You need to search harder there is this for example which makes this a shopping question. \$\endgroup\$
    – RoyC
    Commented Jan 12, 2018 at 9:23
  • \$\begingroup\$ Look for an inverting boost converter. \$\endgroup\$
    – Colin
    Commented Jan 12, 2018 at 9:40
  • \$\begingroup\$ "symmetric" might be a relevant keyword. \$\endgroup\$ Commented Jan 12, 2018 at 9:51

3 Answers 3

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What you're looking for is a split rail power supply. I've also seen these called a dual output supply, although that name also applies to supplies with 2 different positive voltage outputs.

A PC power supply is an easy option. Many have a 12v rail rated for around 500ma.

Another option is to use 2 isolated power supplies (hook them up like you would batteries).

I've seen some good options on ebay before as well:

Mean Well PD-2512

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  • \$\begingroup\$ Thanks for teaching the terminology, but just to let you know the ebay link is for an AC to DC converter, not DC to DC (Input: 85-264VAC @ 47-63Hz) \$\endgroup\$ Commented Jan 12, 2018 at 14:04
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Getting the +12v supply should be obvious from starting with an available +12v or +19v supply.

Obtaining the negative voltage is a bit more difficult, but here is a Linear Technology product lookup page that you can enter in the available input/output voltages and the required I out. Hitting the search button gets you a list of recommended inverting chips to perform the inversion. http://www.linear.com/products/inverting_regulators

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  • \$\begingroup\$ If there are ready inverting converter boards with the chips and everything already there that would be even better \$\endgroup\$ Commented Jan 12, 2018 at 9:45
  • \$\begingroup\$ Those may exist too, you might do a search starting with the recommended chip type and see if a complete module/board shows up. There may also be prototype built up boards available from Linear Tech with the specific chip type. Often these newer chips do not require much in the way of extra parts to make a working design. \$\endgroup\$
    – Nedd
    Commented Jan 12, 2018 at 9:50
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Making the pos 12VDC from 19VDC can be done easily with a buck converter .If you replace the output inductor with a with a 1:1 coupled coil with the same inductance and appropriate current rating then your buck will still work on one of the windings of this coupled coil .The required Neg 12VDC can be derived of the other winding with a simple peak detector consisting of a fast diode and a cap .This trick is nothing new.Old PC power supplies would have overwinds on powdered iron output chokes to make neg voltages.What is new is that coupled coils are easy to buy from manufacturers like Coilcraft so you do not have to wind a transformer .I have used this scheme countless times to make +/_ 15VDC from 24 or 48VDC .The buck converters that I have used over the decades are :Simple Switcher ,3842,S TRAP discrete.The neg output is not super accurate and the loading of the neg output has always been low compared to the pos output .Before the coupled coils were applied I used an extra coil which was still much simpler than an extra converter .It can be shown by math that a coupled coil is better than two coils .The coupled coil outperformed the two coil approach on the bench in terms of neg rail stability .

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