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How to use DC Voltage Regulators and Converters

Hello, how’re you going? My name’s Sam and I’m from Core Electronics and today we’re going to be taking a look at how to use DC Regulators and Converters.  They’re sort of the one and the same thing. Now what is DC first of all? Now if you’re not familiar with some of these terms like DC, which stands for direct current check out our Analogue Electronic Currents Crash Course tutorial first because it covers a lot of the basics of electronics like voltage, current, OHMS law and the basics of components. But today we’re going to be taking a look at a few different  types of converters and regulators and how you can use them in your project, how do they work?

Well, first of all a bit of a term clarification, you’ll hear a few terms come up in this tutorial that you might want to get a grasp on. First of all we’ve got ‘Load Regulation’, now this defines how much the output voltage changes with regard to the current being drawn from the output. So really, a regulator that has a really good load regulation means when it starts drawing more current it’s still going to deliver the same voltages, it’s not going to sag according to OHMS law.

Second of all we’ve got ‘line regulation’, this term defines how much the input voltage changes effects the output, so if, you know, you’re supplying a converter with say 5V and you’ve got 12, it’s a step-up converter and you’ve got 12V on the output.  Now if you get changes in the input voltages is that going to effect the output voltage? Or is it going to remain pretty constant and stable? And will it do that under load and things like that.

You’ve also got ‘dropout voltage’, now on a regulator such as a step-down regulator you’ve got what’s known as the dropout voltage and that is the voltage that it can be, the input voltage can be ah, above the output voltage. So it’s a bit confusing but say for example we’ve got a 5V regulator, now this is an L7805 5V Linear Regulator and the dropout voltage for it is a couple of volts above the output voltage. So if you have a 12V it’s going to output the 5V, um, but say the dropout voltage is 2V that means that your input voltage can be no lower than 7  because it’s the dropout voltage above the output voltage before you start running into issues. So now we’ve got that out of the way lets dive in to what are Regulators and how do they work!

02:17 Well, we’ve got two types of regulators, Linear regulators or switching regulators or switch mode regulators or converters. We’re using the term interchangeably here. Now these are just different methods for converting voltages and we’ll get into how they actually work in a minute. But it is important to note that they’re different products, you can’t just say that one is a linear regulator when it’s actually a switching regulator because they operate differently.

Now, a linear regulator uses a pretty simple circuit and it essentially dumps the extra voltage so say you’re converting 12V down to 5V, well a linear regulator usually will have an operational amplifier in it or loading components inside of here to drop that voltage down to the 5V. But a switching regulator actually has a PWM signal driving a really really fast electronic switch on and off, you know, thousands of times per second. Now this is really good because unlike a linear regulator there’s no components in there to introduce, well, little components, so very few components in there to draw a very slight load on the regulator which means the switch is either always on and there’s no ‘on’ resistance or it’s off and there’s you know, maximum resistance, no current can flow which means that unlike a linear regulator these are very very efficient power wise, a lot less you know, wastage and power losses during the conversion.

03:49 Now within regulators there is two, well three terms that you are going to hear thrown around.  You’ve got Buck, Boost and a combination of the two, Buck-Boost. These terms are simply whether it’s a step-down regulator or a step-up regulator and how the circuit works. A buck regulator is designed to drop the voltage, it’s a step-down regulator or converter.  So say you have a 12V input then that is going to give you say a 5V output or you know it’s a set 5V output you could supply 12V, 18V, 24V, whatever, it is a buck switching regulator.

Now if you have a boost switching regulator that means you’re stepping up the voltage so it might be a 12V output and you can give a variable input voltage between say 3V and 9V or what ever. Or a buck-boost regulator is one that can do both which is really cool. You give an input voltage and it can give you a wider range of output voltages both lower and higher than your input voltage which is really, really cool.

04:46 So we’ve got these two different types of regulators, now there’s also a third type of regulation that we haven’t covered which is Zener Diode. Now a Zener Diode is, acts like a regular diode, it acts like a valve except that it has a special property called Zener Voltage. Now what this does is normally when you would use a diode it is forwards-biased which means current flows in one direction and then the other direction it doesn’t allow current to flow. But with the Zener Diode you can actually reverse-bias it and once that voltage, the reverse voltage reaches a certain point, reaches the ‘Zener Voltage’, it will conduct as well which is really, really cool because you can use them to put a quick easy dirty regulator on a project just if you want to test something out.  So what you could do is you have a 12V, we’ve got a diagram in the tutorial, we’ve got a 12V supply and you might have a Zener Diode that has a Zener Voltage of 5.1V now you could put this so that it will never conduct, never always conduct, so you’re reverse-biasing it and then as soon as that voltage gets above 5.1V it’s going to dump that to ground and it gives you a nice fairly stable 5V output. But there are some issues with this, you get, you can get sags in your voltage, it’s not ideal, it’s a quick and dirty method. A good linear regulator or switching regulator is going to be what you want.

06:06 So now we’ve discussed some of the, I guess the trade offs. Switching regulators are more expensive but they’re much more energy efficient, a Linear regulator is less efficient but they’re a lot cheaper. Something to be aware of as well is that switching regulators, because they’re switching very rapidly on and off, you can actually get some of that noise into the power line. Now that’s fine if you’re using a digital circuit with plenty of filtering and all the rest and it’s quite safe. But they don’t recommend using switching regulators for audio circuits because you can actually hear that switching noise, that frequency is low enough that it can be heard by the human ear, if you’re using that in an audio circuit it can actually transfer into your audio signal which is not ideal, not ideal at all.

06:48 So, which one is better? Well, switching regulators are fantastic if you want efficiency, all about efficiency. For example these guys will often handle a mains signal and this is the primary method of getting a mains signal so 240V here in Australia, 120V in other places, down to say a 5V like you would find in a laptop charger or a cell phone charger. Because once you use a rectifier to get rid of the AC current you are just left with 240 V in DC you can then use a switch mode supply and even though there’s this huge gap, this huge change in voltages because these are so efficient there’s less heat to dissipate, there’s less energy being wasted. They’re a great choice for value, if you try to do that with a Linear regulator the bigger the gap in the voltages, so if you’re stepping down 240V to 5V with a linear regulator it would have to have a huge heat sink because it has to dissipate all of that extra voltage somehow and it’s energy wasted. They’re not efficient but they are cheap and fantastic for some projects.

07:52 So something else to be aware of is especially with linear regulators is the efficiency is going to change and what you’re going to want to look at is the efficiency curve. Now these Pololu Regulators are fantastic. Pololu make really high quality regulators, converters from step-up regulators, step-down regulators, adjustable regulators you can change the output voltage with a manual adjustment or with some kind of digital interface which is really cool. But it’s going to change depending on the relationship between output current and also the input and output voltages. So take a look at the, I’ve got here a 12V regulator. Now the efficiency curve for this guy shows that when it’s got a 9V input and it’s stepping that up to 12V so it’s less work for it to do. Which means there’s less energy wasted you can draw more current before the efficiency starts to drop, if you were to go, supply with 5V and step that up to 12V the efficiency drops especially as you start drawing more current and if you use it with 3.3V well, still do it, that’s not a problem, the efficiency gets considerably worse. So just something to keep in mind that if you’re using regulators in your project you don’t want to be stepping your voltage up then stepping it down again and you know, you get all of these energy losses in your circuit if you’re powering a circuit from say a battery you’re going to want to regulate everything from that supply if possible. So if you need a 9V supply and a 5V and 3.3V use seperate regulators. Don’t daisy chain them all because you’re going to get these huge energy losses. But it’s worth taking a look at the data sheet figuring out how exactly you can get the most bang for buck as far as the electrons whizzing around in your project.

So hopefully this has given you a pretty good, I guess, introduction to what Regulators and Converters are. It’s a bit of info about how they work, there’s a lot more technical detail to go in to but we won’t cover that now, that’s for another time. But you can easily use regulators and converters, they’re quite cheap. This 5V regulator, and as I said, connect anything above a 7V or 8V supply to it and it will regulate down to a nice clean rock solid 5V. We’ve got a sample schematic shown here so you can hook it up for a breadboard for a project. Get a couple of these and keep them on hand because you never know when you’ve got a 9V project and you just need that 5V for a digital system.

So that’s all for today guys, enjoy, happy making and we’d love to see some of the awesome projects you guys are making with Linear Regulators, Switching Regulators and other cool bits of gear, seeya :-)

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