Lower Voltage Methods Other Than Voltage Dividing

voltage

I have recently learned that voltage can be lowered using resistors to divide the voltage. This seems simple and easy. Before this I thought I had to use a voltage regulator or a zener diode to lower voltage. Is there any reason not to just use resistors? What is the benefit to these other methods? Other than the methods I listed, what other ways are there to lower voltage?

Best Answer

There are probably as many ways to do it as there are engineers. The common themes are:

  • Zener:
    • Few components
    • (Mostly) Immune to input variations
    • Not efficient at all but acceptable for low-power applications (you're powering the load through a resistor)
    • Used in analog or digital applications to provide a specific voltage for power or to provide a reference or to limit the "volume" (distorts grossly when it becomes active, but it does the job, sometimes this is used artistically to create a sound, like for electric guitar)
  • Divider:
    • Few components
    • Passes input variations because it's actually a ratio of the input
    • Easily influenced by the load (sometimes this influence is done on purpose)
    • Not efficient at all for power (you're still powering the load through a resistor)
    • Used a lot in analog applications to reduce the volume or to provide a reference between supply rails
  • Linear Regulator
    • Few (IC) or many (discrete) components
    • (Mostly) Immune to input variations
    • Efficiency depends on the difference between input and output voltage (less difference is more efficient, but some headroom is required; you're still powering the load through the equivalent of a resistor, which is internal to the regulator and automatically adjusted)
    • Used in analog or digital applications to provide a specific, sometimes variable, voltage for power
  • Switching Regulator
    • Many components
    • (Mostly) Immune to input variations
    • (Usually) Very efficient because it's either hard-on (low loss) or hard-off (no loss) with a very short transition time (high loss), the switching frequency is then filtered out to leave the average, which is fed back to a controller. (finally, we got away from the resistor!)
    • Used in digital applications to provide a specific, sometimes variable, voltage for power; not so much for analog because of the switching noise, though sometimes it might be forced into service with a ton of filtering

Note that a switcher is the only one that can also increase voltage; this is because it naturally has AC inside of it (the switching frequency) that can be passed through a transformer or at least an inductor.

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