Buck converter vs. linear voltage regulator - practical comparison - YouTube

Hi, these 3 devices are buck converters

and they make a great alternative to linear voltage regulators.

In this video I'll show you in practice why and when you should consider using buck converters.

Linear voltage regulators like this commonly used LM7805 are so cheap and so easy to use.

Just supply those 2 pins with 7-16V,

add a 10uF capacitor on the input,

another one on the output

and you get steady 5V.

As we all know, nothing is perfect, and so are linear voltage regulators.

They are quite inefficient, because they waste energy and produce a lot of heat.

How much heat you may ask?

Let's take an example.

If you want to feed your voltage regulator with 9V and draw 500mA on the output, you

will have to dissipate 2W of heat.

The temperature of your LM7805 will definitely go above 100 degrees C or 212 degrees F.

If you want to draw even more current, or increase the input voltage

you might need a big heat sink,

or use a buck converter.

Probably all computer power supplies utilize buck converter circuitry to maximize efficiency.

You can buy buck converters in different shapes, sizes and with different specifications.

Another name for a buck converter is voltage step down converter,

which describes it's purpose pretty well.

You feed those two pads with DC voltage

and you get constant lower voltage here.

The output voltage is adjusted by this potentiometer.

For example, you can set it to 5V and this little guy becomes

a very efficient 5V voltage regulator.

Let's compare in practice the already mentioned LM7805 linear voltage regulator

with this really small buck converter.

Both are given 12V on the input

and they provide 5V on the output.

The driver boards from these old hard drives consume approximately 450mA and they will

serve as my dummy load.

I will measure the power consumption and temperature of the linear voltage regulator

and the buck converter

under the same load 15 minutes after powering up.

Only 2 minutes later the LM7805 consumes about 420mA at 12V,

but as you can see the power consumption drops to 0 and then goes back to 420mA over and over again.

The LM7805 shuts down if the temperature goes too high.

It can operate properly up to 125 degrees C or 257 degrees F.

Then let's check the temperature.

As you can see it's well above the safe range, so the regulator shuts down

and turns on after cooling down a bit.

The linear voltage regulator draws 420mA at 12V, which gives us 5.04W.

Now let's check if the buck converter can finish the same test.

After exactly15 minutes the buck converter draws only 220mA at 12V, which is only 2.64W.

In this configuration the linear voltage regulator consumes over 90% more power

than the buck converter,

which is worth considering, especially when your device is battery powered.

Now, let's check the temperature.

As you can see, the buck converter stays at only 38 degrees C or 100 degrees F.

In this example the superiority of the buck converter is very clear,

but you can buy an LM7805 for about 30 cents,

while the cheapest buck converter will cost you about $2.5.

There is one more thing – because buck converters use coils, they may cause interference in

your circuits, so if you're building something sensitive, like a radio, for example, you

should grab a linear voltage regulator and live with all its drawbacks.

On the other hand, when you are designing a device in a small enclosure, where proper

airflow cannot be provided, a linear voltage regulator with a big and hot heat sink is

probably not a good idea.

Now you know the main advantages and disadvantages of buck converters

and linear voltage regulators.

If you have any questions or want to add something, feel free to write a comment below,

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Thanks for watching and see you next time.