Techniques For Implementing A Positive And Negative Output Voltage For Industrial And Medical Equipment

by Rich Nowakowski, Texas Instruments, Dallas, Texas, How2Power Today, Oct 25 2012

Focus:
Many analog circuits in industrial and medical applications require both positive and negative supply voltages to operate. A discrete switching regulator is often used to derive both positive and negative output voltages, but implementing an inverting buck-boost topology with a coupled inductor can be burdensome. However, recent advancements in dc-dc modules allow straightforward implementation of a split-rail power solution. This article surveys several discrete and module-based negative-output and split-rail, positive-and-negative output solutions for powering split-rail amplifiers, analog sensors, data converters, and audio amplifiers. Design options discussed here for generating a negative supply voltage from an existing positive supply include the inverting charge pump, the buck-boost voltage inverter, and the negative-output power module. Design options for generating split-rail, positive-and-negative outputs include the transformer-coupled split-rail design, the isolated Fly-buck, and a power modules + LDOs configuration. Key factors such as complexity, component count, relative cost, and performance are explored. Tools are also referenced to learn more about implementing the solutions. The power solutions presented here are based on Texas Instruments’ power ICs. However, in some cases, similar designs may be implemented using ICs from other vendors.

What you’ll learn:

• How to generate negative supply voltage from existing positive supply voltages using an inverting charge pump, a buck-boost voltage inverter, or a negative-output power module
• How to generate split-rail, positive-and-negative supply voltages using a transformer-coupled split-rail design, an isolated Fly-buck, or a power modules + LDOs configuration

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