How to deal with fluctuating input voltage?

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Discussion Overview

The discussion revolves around the challenges of regulating fluctuating input voltage from a 12V power supply in a car engine application. Participants explore various methods of voltage regulation suitable for handling input variations between 10V and 14V, focusing on both theoretical and practical solutions.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant suggests the need for power supply regulation due to the fluctuating voltage from a vehicle, proposing a Zener diode but noting its limitations for the required output voltage.
  • Another participant recommends using a voltage regulator that operates at a lower input voltage, such as 5V, to manage the varying input voltages.
  • A third participant introduces the concept of a buck-boost converter as a potential solution, highlighting its efficiency compared to a resistor and Zener diode setup.
  • One participant expresses uncertainty about using a specific circuit for regulation, questioning its complexity and suitability for their project.
  • A later reply clarifies that the suggested linear regulator can only step down voltage and emphasizes the need for a more complex circuit to achieve both step-up and step-down regulation.

Areas of Agreement / Disagreement

Participants present multiple competing views on the best approach to voltage regulation, with no consensus reached on a single solution. The discussion reflects varying levels of familiarity with different types of voltage regulation circuits.

Contextual Notes

Some participants express concerns about efficiency and complexity, while others focus on the specific requirements of the project. There are unresolved questions regarding the current consumption and the exact configuration needed for the regulator circuits.

Who May Find This Useful

This discussion may be useful for individuals working on automotive electronics, particularly those interested in voltage regulation techniques for variable power supplies.

naiht
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I am doing a tacho-meter of a single 12V power supply, it is meant for a car engine.
However in real life the power supply from an real vehicle fluctuates between 10-14V.

In this situation it is clear that some form of power supply regulation is needed.

I am currently considering a Zener diode (zener regulation); but if so the breakdown voltage (or the zener value) has to be lower than 10V, which does not meet the 12V supply requirement.

Are there any more suitable power supply regulation that can deal with the fluctuation?
Say, make 10V to 12V and make 14V to 12V?

Hope you understand my questions!
Thanks all!
 
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What you want to do is run off a voltage less than what your lower limit is going to be... say 5V and then get a voltage regulator to handle getting you the 5Vs from your varying range of input voltages.

Just do a google search for voltage regulator and find one that fits your needs.
 
I appreciate your replies!

Dmytry, if efficiency is not concerned, will this one http://ecelab.com/circuit-regulator-opamp.htm work?
I am not really familiar with converters and the circuit looks complicated with those RLC...

I am trying to do comparisons to find the most suitable way for my project :)
 
Oh and one more thing, the regulator's circuits have +ve & -ve terminal, while I only need a single +12V voltage supply... How should I connect the regulator?
 
naiht said:
I appreciate your replies!

Dmytry, if efficiency is not concerned, will this one http://ecelab.com/circuit-regulator-opamp.htm work?
I am not really familiar with converters and the circuit looks complicated with those RLC...

I am trying to do comparisons to find the most suitable way for my project :)
The circuit you linked can only step down the voltage I'm afraid. It's a linear regulator, dropping the voltage on the transistor.
What is the current consumption?
For the regulation that can step it up as well as down, you absolutely need complicated-looking circuit with energy storing elements (capacitors, inductances). It is not necessarily complicated to build through.
One example.
http://cache.national.com/rd/PAhtml/PADC_NSC0102.html

edit: another example specifically for your situation:
http://www.maxim-ic.com/app-notes/index.mvp/id/411
 
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