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### Topic: How does Voltage Regulator work? (Read 284 times)previous topic - next topic

#### electronicman122

##### Jan 18, 2021, 10:29 pm
Hello everyone,

I was hoping someone could give me a very basic breakdown of how a Voltage Regulator works?  I found this article - Voltage Regulator Explanation but its a little complex for me. Anyone have an easy explanation for a rookie that doesnt know much about other components?

Any help would be great. I am looking to repair my power supply and kinda need to know how these work!

#### DVDdoug

#1
##### Jan 18, 2021, 10:39 pmLast Edit: Jan 18, 2021, 11:35 pm by DVDdoug
The key is feedback - negative feedback = corrective feedback.   It's the same concept when you drive straight down a road...  If you start drifting slightly-right, you correct by turning slightly left.

But with electronics the variations are very-very small and the corrections are very-very fast so the output voltage holds very constant (depending on the design).

Most op-amp circuits also use negative feedback.

P.S.
You can actually make a voltage regulator from an op-amp (or any amplifier).   Let's say you have an amplifier with a gain of 5 and you feed-in a "reference" voltage of 1V.   You'll get 5V out as long as you have a little more than 5V available and as long as you don't exceed the current limits of the amplifier.

...And current limits are the main reason you don't see op-amps used as voltage regulators.   You'd also have to supply your own voltage reference so it's better & easier to use a specialized voltage regulator chip.

#### hammy

#2
##### Jan 18, 2021, 10:42 pmLast Edit: Jan 18, 2021, 10:47 pm by hammy
A linear regulator such as a 7805 has a transistor between its input and output .
The regulator has an internal reference voltage . This voltage is compared to the output voltage - if the output is low the transistor is turned more "on"' ; if it's too high it is turned more "off" .
So the transistor drops the input voltage across its self, in much the way a variable resistor would , to keep the output voltage constant.

https://components101.com/articles/what-is-voltage-regulator-and-how-does-it-work

There are other types of regulator, such as switching types that rapidly turn the transistor on/off so the " average "output voltage after smoothing is  controlled.

#### slipstick

#3
##### Jan 18, 2021, 11:32 pm
There are many different types of regulator. If you want to repair a power supply the first thing you need to know is what type it is using. If you provide some detail of the thing you're trying to repair we might be able to help.

Steve

#### Paul__B

#4
##### Jan 19, 2021, 01:27 pm
I am looking to repair my power supply and kinda need to know how these work!
Now that is an ambitious project!

#### Grumpy_Mike

#5
##### Jan 19, 2021, 07:34 pm
Quote
I am looking to repair my power supply
Yes they are almost impossible to mend because for you to get any sort of operation it has to all work. You will need at least to have a Variac, a variable transformer that provides isolation and allows you to wind up the voltage so you don't start off at full voltage.

#### wvmarle

#6
##### Jan 20, 2021, 05:15 pm
The only time I tried to (and succeeded!) in actually fixing a power supply was by replacing a burnt chip and failed electrolytic cap. Probably the cap went first... Desoldered the parts from the PCB, replaced with new ones, and it all worked again.

Completely replacing a power supply with a new one is a whole different level! I'd even not bother making my own linear regulator. It's so much easier (and cheaper, and more reliable) to just buy a ready-made one.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

#### michalpuk

#7
##### Jan 20, 2021, 10:41 pm
On my website there is article about zener diode https://911electronic.com/zener-diode/
On there you can check characteristics and I think you should read more about the zener effect in case of regulators

#### Grumpy_Mike

#8
##### Jan 21, 2021, 07:08 amLast Edit: Jan 21, 2021, 07:11 am by Grumpy_Mike
Quote
and I think you should read more about the zener effect in case of regulators
And when you do you will find out that they are useless these days for making a regulated power supply. That power supply example has no capacitors on it making it great for generating noise. The layout of this page suggests you are trying to teach this stuff. And please don't post links that take you away from the forum, leave that option unchecked.

#### johnerrington

#9
##### Jan 21, 2021, 07:57 am
You may find my tutorial on linear power supplies useful. Starts from basics.
I'm trying to help. If I find your question interesting I'll give you karma. If you find my input useful please give me karma (I need it)

#### Paul__B

#10
##### Jan 21, 2021, 09:46 am
And please don't post links that take you away from the forum, leave that option unchecked.