Voltage Regulator for Li-ion battery power - NEWBIE QUESTION!

I have a pretty basic question about Voltage Regulators.

I am building a robot using LEGO Mindstorms; but need a more powerful power supply than 6x 1.5v AA batteries.

I want to use Li-Ion batteries; but they generally deliver 3.7v and LEGO requires 9v. Plus, as the batteries drain the voltage drops off.

The solution seems to be to use a Voltage Regulor such as this: https://uk.robotshop.com/products/dfrobot-dc-dc-multi-output-buck-converter-33v-5v9v12v

Would that work? I connect, say, 3x 3.7v batteries to it and despite the fluctuation in their voltage as they drain the device will deliver a constant 9v?

Also, is there a difference between a “Voltage Regulator” and a “Buck Converter”?

Many thanks in advance for any advice.

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Hi @benredstar and welcome to our forum.

Yes, there is a difference between a “Voltage Regulator” and a “Buck Converter,” though a buck converter can be a type of voltage regulator.

  • Voltage Regulator: This is a general term for a device or circuit that maintains a constant output voltage regardless of changes in the input voltage or load conditions. Voltage regulators can be linear or switching.
  • Buck Converter: This is a specific type of switching voltage regulator that steps down (reduces) the input voltage to a lower output voltage. It is also known as a step-down converter.

DFR1015 is a step-down converter, the input voltage should be larger than the output, and it works better with a voltage difference of 2V and above.

So in your case, since you want to connect in series 3 x 3.7V Li-Ion batteries, your input voltage is around 11V, and you would set output voltage to 9V, so it should work.

There could be a problem if your voltage drops down significantly. Also, there is a question on how will you charge these batteries?

Thanks so much for this informative reply. Do you mind if I ask some more questions?

What is the difference between a linear and switching voltage regulator?

What if I used this one: https://uk.robotshop.com/products/step-down-dc-dc-power-converter-25w

Does it have the same problem where in the input voltage must be ~2v greater than the output?

Thanks again.

/ben

You are welcome.

The main difference between linear and switching voltage regulators lies in how they manage the conversion of input voltage to output voltage and their efficiency levels. Here’s a quick overview:

  • Linear Voltage Regulator:

    • Operates by dissipating excess voltage as heat.
    • Provides a constant output voltage while drawing current from a higher-voltage input.
    • Simpler design and typically cheaper.
    • Offers low noise and fast response to changes in load or input voltage.
    • Less efficient, especially when the difference between input and output voltage is high, leading to more heat generation.
    • Suitable for low-power applications where minimal noise is crucial.
  • Switching Voltage Regulator:

    • Uses an inductor, capacitor, and other components to efficiently convert input power to desired output voltage.
    • Can step up, step down, or invert input voltage based on the design (buck, boost, buck-boost, etc.).
    • More complex and potentially costs more.
    • High efficiency because it minimizes power loss as heat, even with large differences between input and output voltages.
    • Can generate electromagnetic interference (EMI) due to switching operation.
    • Suitable for high-power applications or battery-powered devices where energy efficiency is critical.

Regarding this step down dc-dc power converter. I would say it is the same. Input voltage has to be greater than output. It does not mentions 2V difference explicitly but I guess it works on the same principle so there has to be some difference.

Thank you again for this advice. It’s really helpful and really appreciated.

/ben

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You are welcome.

For 9V output voltage from 3x3.7V batteries, you can use the adjustable version of LM2596.

1 Like