-12v supply from +12v

Question

Part of my circuit needs -12v. What would be the simplest way to get this, considering I have a +12v supply already available in the circuit? I need ~500ma

I searched for -12v regulators on Mouser, but many of these needed a negative voltage input.

Ideally looking for an IC that can handle this.

Answer 1

There are a number of ways to get a negative, below ground supply.

• Easiest: If the source is AC, uses a full-wave bridge connected opposite to that of the positive supply.
• If DC only is available, use an inverter that may use
  • a charge pump for low currents or
  • an inductor or transformer for higher currents.

The Texas Instruments TPS54620 is a step-down (buck) converter, which can be configured to provide a voltage below ground, e.g. this circuit from Digikey.

An Analog Devices LT8331 could supply 80 mA at - 12 VDC.

An inverting charge-pump such as the Microchip TC1044S can 20 mA, if that meet your needs.

It is even possible to use the 555 timer/oscillator to get -12 VDC, though regulation would not be good.

Answer 2

You can leverage the fact that the Buck-Boost Topology is inherently inverting - these are a few examples of Reference Designs that do just that:

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PMP7330 - Positive 12V to -12V (0.1A) buck-boost converter (Schematic) (Test Results)

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PMP7207 - Generic TPS40200 Inverting Buck Boost Reference Design (Schematic) (Test Results)

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PMP2224 - Buck-boost (-12V @ 0.5A) for the TPS5430 (Schematic) (Test Results)

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• You can find for more Reference Designs here: Reference Design Library
• You can learn more about the Buck-Boost topology here: Topology Tutorial: What is an Inverting Buck Boost?