Hi Welcome to Fundamentals Friday This one's a follow on from the Cockro Walton Voltage multiplier we looked at a couple of weeks back and once again, it's a little useful circuit building block for all sorts of applications. We're going to choose one typical application today where it may be useful and that's in the case of a Uh microcontroller for example, or your circuit widget. whatever it is powered from, say, for argument sake, a little 3vt coin cell battery CR 2032 or a couple of Aa's or a couple of Aaa's or whatever 3vt Supply And let's say you're actually wanted to power something that needs a 5vt rail like one of those. Um LCDs A typical LCD module.

you can get 3.3 volt ones, but much more common and much cheaper to get and much more wider availability of 5V versions. So how do you actually hook that up? Well, there's a couple of ways to do it. we're going to look at one way, and the building block we're going to look at is called the Dixon Voltage Doubler, some sometimes called a Dixon multiplier, sometimes called a Dixon charge pump. all sorts of things or just a charge pump doesn't have to have the name Dixon in it and what it is.

It takes us back to the Circuit we looked at with the cockroft Walton multiplier and in uh, this case the uh Gren acre circuit that we looked at if we had a Transformer with a 3vt peak to- Peak input signal. it actually level shifted that up and gave us 6vs DC out. If you haven't seen that video, I'll link it in down below. It explains all this and we're going to use this basic circuit again.

Once again, a little rearrangement again and it will'll create our Dixon voltage doubler and we can do exactly the same thing. Because like in the case of this product here, we got our microcontroller. we don't want a Transformer We don't want all sorts of things. I mean there various options? You could you know up here you could.

if you wanted to double your voltage from 3 volts to 6 Vols You could use a 760 uh charge pump chip and That's a classic Jelly Bean building block part. It's a capacitor voltage double up voltage inverter. You can use it in various configurations, but it's you. know it might cost a dollar a chip or something like that and well, you know you want to keep your bill of materials cost low.

As you're doing a lot of projects for a oneoff might not be a problem. There's various ways uh to do it, but let's try and lower the cost here by doing it with dodes and Capac capacitors cuz you've already got likely diodes and capacitors in your bill of materials anyway. And well, in any case, even if you don't have the diodes, for example, they're incredibly cheap to add to your circuit. so we can replace a 760 voltage charge pump voltage doubler with a Dixon voltage doubler.

So how do we do that? Well, first of all, let's get rid of the Transformer We don't need a Transformer that's only useful for high voltage generation. We're not talking High voltage generation here. we're talking low voltage. And that's where this Dixon voltage doubler comes into play in.

A absolute perfect example is the case we got here. We want to double 3 volts into uh, roughly 5 volts to power our LCD. Ideally, you know you'd have six volts and then you could voltage regulate it down and all that sort of stuff, but we won't really go into that. now.

How do we do it? Well, a quick rearrangement. Take our classic uh, Gr Acre circuit there and erase that and put our diode in series like that and a capacitor down like that. But let's not have it go into ground, shall we? Let's have it. Another input here.

So we got two inputs coming in here like this. and what do we have in our design up here? Well, we've got 3vs DC and we've got a microcontroller. What can microcontrollers do? They can generate clock Pwm signals, so we can actually use the microcontroller to generate a clock signal. So what we're going to do here is we got two inputs like this and this one will actually put to 3 Vols DC So we'll tie that to our voltage level and then we will feed in a clock into this input down here and Magic happens.

which I'll explain in a minute we're going to get 6vs DC out and if you've seen the Cockro Walton Mage voltage multiplier video, you'll see how that works. We've effectively level shifted that up feeding in the clock which we were get in from the transformer in the other configuration and this circuit configuration is now a Dixon voltage doubler. We'll get 6vs DC out of that with nothing more than a single pin on our microcontroller generating a Pwm signal. Beauty Now, if you're paying attention when I swapped these components around here, it didn't actually do anything at all.

The circuit configuration is actually exactly the same as the Gren Akre voltage doubler except that we now, um, we don't have like an an AC signal Source from a Transformer or something like that. We've just got a a 3vt voltage source or our DC Source plus a clock, but it's exactly the same thing. Essentially, you can switch those around and then this is waveform up here. 3 Vols down there.

the um anode of the diodes down there. series diode there. it's exactly the same circuit. haven't changed anything.

So our Dixon voltage doubler is a bit of a con. It's actually a Greenre doubler. There really, essentially no difference. and the waveform and how it operates is exactly the same as before.

So let's have a look at the operation of this thing. now. once again, we're going to assume that we got ideal diodes. we'll get into the Practical uh consideration in there later.

but ideal di. Let's assume also that the circuit's reached a steady state and the capacitor is charged up and we've got no load on this thing. Okay, so this point number One here is Uh, 3 Vols DC Here it's charged up to 3 volts. Well, there's 3 volts across that capacitor there.

So when this um is low, when Waveform Two down here is low, then our point up here: number One is going to be 3 Vols above there. But when this waveform goes High there's already 3 volts across our capacitor. So then it's going to double up to 6 volts at that point and it can't flow back through the diode. It's going to prevent that.

So what do we end up with at this point? Number One: We end up with this shifted once again. waveform shifted like that. uh, above this bias reference voltage which happens to be our battery voltage or our supply voltage. It could be 3 Vols 5 Vol whatever your DC Supply voltage is.

and bingo it's shifted that waveform up like that. And this point here is the red waveform there like that. And of course we've just got our basic rectifier here with the diode and the cap which then Smooths that out to our fixed 6vs DC out Bingo We've doubled our voltage with just a single pin on our microcontroller or the clock could come from somewhere else in your circuit. Usually you're going to have it coming from a micro though, and that's all there is to it.

It's just a Gren acre doubler. but yeah, it's called a Dixon doubler. Whatever. And the reason these things are sometimes called charge pumps as well is because the capacitor charges up and then you're so it's already charged up.

and then you're pumping more into it. You're utilizing the charge that's already on the capacitor to boost that voltage up. and that's essentially what we're doing. We're essentially just level shifting again.

Once again, we're not actually doubling. You know, there's no double in here. This waveform here doesn't get twice as big as this one. It's just shifted it up like that and we're utilizing that DC reference level to do and the diode steering to do that.

But unlike our high voltage DC generation, these low voltage charge pumps or doublers usually have to drive at least some little load. You're driving like an LCD which might take you know, 1 or 2 milliamps or something like that. but for you know, a couple of milliamps, it's going to be good enough using typical, you know, fairly low, uh, value caps in here like 10 microfarads or something like that. Can easily probably do a couple of milliamps if you want in the order of hundreds of milliamps, Eh, You're not really going to get it from one of these uh, uh, capacitor charge pumps.

But of course you can do an awful lot with a milliamp. You can fly to the moon on a milliamp, or drive an LCD or drive an up amp or something like that. You could even regulate. use one of those low power low Dropout voltage Regulators If you wanted to regulate the output because when you start putting a load on here as we saw last time, even if it's a small load, you know a drawing, a milli or two, then you're going to start to see well, your let's draw in the blue waveform.

It's not going to look perfect like that anymore. Sorry about the red one going there. It's going to start drooping like this and then it'll kick it back up and it'll droop down again and it'll kick it back up. And you're going to get Ripple on this DC output here.

And sometimes that's not desirable if you're you know, paing, some analog stuff or something. but you might be able to say have a voltage regulator a 5vt voltage regulator in there. Once again, we're assuming ideal diodes. We're not actually going to get 6 Vols out of this thing when we build it up.

obviously because you know a DI had lost. you know3 Volts for a shock key or something like that. But um, you know the theory. Remains the Same You could have a low voltage uh Dropout in there you B these capacitors based on the discharge rate of your load and Bingo! You can get a nice, clean, regulated output for your little project.

Great! So sometimes that's a lot more simpler and cost effective than changing the battery solution for your product. Like for example: I use this in my little microw watch uh, project my scientific calculator watch right I powered it from a single 3v Cr23 32 coin cell battery I couldn't really put a a higher voltage battery in there. It just didn't suit the system design of the calculator watch. So it was much more beneficial to use one of these Dixon voltage doublers than it was to re-engineer Or you know, change my battery solution for this thing.

And at this stage you should be thinking aha, can we use that multistage configuration like we did on the cockro Walton multiplier Well, yes, of course we can. It's exactly the same circuit, it's just some of in a different usage um, configuration here. So we've added another stage here to this so we can multiply our 3vs DC up to 9vs DC Beauty How does it work Exactly the same configuration? Imagine this that is still our same circuit as before. Okay, but we've now got a 6V DC reference here point up here instead of a 3vt DC reference point here.

So we've just shifted that waveform up again I Won't go through all the details. It's exactly the same as I explained in the Cockro. Walton voltage multiplier video so that 3 volts Peak to Peak from our microcontroller here and it will be 3 VTS Peak to peak of course from a Seos microcontroller. Then it just shifts it from 6 up to 9.

So. 3 Here the green waveform is exactly the same. it's just shift shifted it up this point. This point here get shifted up again and then we got 9 volts and then we got our final rectifier on there output which gives us 9 Vol DC on the output.

But of course once we put a load on, it's going to Sag like that. But H there you go. Then we could certainly whack in our 5volt voltage regulator and have heaps of margin. You wouldn't even need a low Dropout type Beauty And in case you're wondering, yes, this is the new Teespring crowdfunded Trip 5 timer t-shirt if you missed out on it.

Ah well, I might run another one soon. we'll see. But top quality I Love it! And next up we have Dave looking trendy and smart in a nice little Teespring number. He looks equally at home in the dumpster as he does on the workbench.

And to the breadboard we go Deja Vu Folks, we've been here before, Nothing new at all. It's exactly what we looked at the other week, but we'll go through the motions again. Here it is Dave Cadra. We've got our 3v DC Supply which will come from our Uh bench Supply We've got 3 Vols DC coming from the function gen and yes, it's shifted up to 1.5 volts so it's not AC so it's 0 to 3 volts.

so it simulates our Um our this signal coming from our microcontroller and then we have our multistage double it. There's our first stage there and there's our second stage there. and we should get 9 volts out of here. And these are the Um channels on the Osilloscope Channel 1, Channel 2, Channel 3 Channel four and it's exactly the same as what we had last time as well.

On the scope screen, all four channels are ground reference down here on that bottom uh, graticule down there. 2 volts per division on all the channels there and we've got our Peak voltage of each of the channels. So let's have a look here on the circuit. Our point one here is actually there.

It is 6 volts. So we got our 3 volts input. By the way, our Square wave amplitude there is 3 Vols I Haven't shown the square wave actually coming in because it's exactly the same as that and it's 6 Vols and then the top of Point 2. Here notice that we've got our diode loss between there and there but with no load at the moment.

so it's it's very small and then the top of the next Point channel three up here 8.2 Vols and that's actually the Uh blue waveform up there. So 3 is the blue waveform sorry, 0.1 is the yellow waveform there 2 is the Uh green waveform there which is your DC value across there. and because that AC signal gets converted into DC that's our 6vt DC reference and then it gets pumped up again shifted up by the blue waveform there channel three up to well, in this case 8.1 Vols Peak and then our final DC output is the purple one there and Bingo! 8.1 volts. And what happens if I shift my 3vs signal here? Well, let's adjust our bench Supply There we go as we move it up and down all the waveforms.

or we just lost our trigger there of course once we get to that point, but uh, we can boost that up there and there you go. It just shifts that waveform up and down. So with precisely 3vt DC input and our 3vt uh, peak-to Peak Square wave which we can generate with a microcontroller, we can get a final output voltage here of 8 Vols There it is and this is using just Uh Bog standard 1n 914 or 4148 doodes, not even the shock key type. Now let's have a look what happens if we put a lousy little 10K load on this thing.

So our final output DC voltage of Uh 8 volts here divided by 10K assuming it stays at 8 volts of course, divided by 10K 800 microamp. So we're drawing less than a milliamp. Here we go, let's connect it up and being Go Look, you'll see it drop and you'll notice that I can probably boost all the channels up like that. You can notice the Ripple starting to appear on channel two there, which is our second point, which is our supposedly our DC reference in there.

It was a straight line before, but now you can see the Ripple in there due to the fact that we're drawing a 10K load. and by the way, I didn't put values on here. these are actually 0.47 microfarads. and let's drop that load by an order of magnitude from 10K down to 1K.

Here we go there, we go. Oh, look at that. So look, it's practically useless now. 3.2 volts.

Uh, top value of our final output. As you can see, it's absolutely useless when we try and power a 1K load there our 3 volts. we're still got our 3vt both of our 3vt signals going in, but it's just it doesn't work anymore More, it's useless and we'll bump that up to 2K and as you can see, significantly improved there. There we go and 3K 4K 5K and you can see the progression in that.

But of course we're not using shocky diodes here. In practice, you would almost always use a shocky diode in this configuration unless you had really low current and you really didn't care. Generally, you're not going to use your uh little uh Jelly Bean 1n 414s. You're going to use some sort of shocky, died they're you know, practically the same price.

Anyway, So let's assume that we just had the single stage configuration here like this. and here's our final output voltage: 4.62 volts at Uh, this is a 10K load half a microfarad, uh, caps on there. and by the way, switching frequency is 10 khz here. a typical Uh frequency that you might get out typical Pwm frequency you might get out of your microcontroller.

uh, for example. and we're only getting a DC output voltage of 4.62 volts there. but that's probably going to be good enough. Uh, only talking like, um, so you know, 4.62 volts divided by 10K So we're only talking half a milliamp.

Some LCDs can go uh, down that low, but uh, not all of them. But you know, potentially we could, actually, you know, almost power one of those little LCD modules because they are fairly tolerant of the supply voltage, would be able to power it with just a single stage circuit with even cra uh, you know, 4148 diodes in there and a low value of capacitance. So what happens if we replace this cap half a microfarad with say, 47 microfarads? Fairly big step up in value. Well, let's do that.

I'm going to rip that out there and I'm going to stick in a 470 microfarad cap. Aha, look at that. We're now jumped up to about 4.8 volts or thereabouts. So what's uh, our frequency going to do? Well, of course it's going to change the discharge, uh curve of this cap.

So um, of course this is still our 47 microfarads in here, but our second stage one up there. You'll be able to. You can just see the Ripple on there at the moment. but let's increase the uh frequency shall we? So here we go.

Oh well. Well, we can drop. Well, we can increase it of course. And of course we just get better.

You know there, you can't see any Ripple on there now. But if we lower that frequency down significantly. aha, look at that. You can start seeing 4 khz.

3. You can start seeing the Ripple appearing and the droop there if we go down to 1 KZ You know. Ah, pretty bad. so you don't want to be operating these things at 1 khz 10 khz.

Reasonably good rulle of thumb. Now what happens if we change all of these caps to 47 microfarads? Pretty beefy value. Bingo Here it is is this is with our 1K load and the amazing thing is that's still at 1 khz as you can see. so it is possible to use a value like that.

but uh, you a frequency like that. but you have to go um much higher in your capacitor values and that's with a 1K load. So um, our there we go. We're drawing 6 milliamps from this circuit.

just over 6 volts on our second stage output there. So 6 milliamps. This thing is taken with even 1 N4 148 diodes. But of course that is a two-stage one to get our 6vt.

So we're getting nothing near our 9 volts we expect. but eh, good enough. But even that single stage one 4.7 volts there is enough to drive like you know, four or five milliamps even at 1 khz. Not a problem.

And because there's no Ripple we're not going to actually see any Uh benefit there by going up in frequency. As you can see, Fre frequency is only going to matter once you start drooping. And if we take our frequency down 81 Herz look at that. because we're using such large value caps, our switch in frequency can actually be relatively low.

you know, in the order of 100 Hertz or so, and we're still going to get a good enough DC voltage out that we could use to power an LCD or something else. perhaps. especially if we decide to, uh, put an extra linear regulator after that. But of course, generally speaking, you know you're not going to be using Uh 47 mic caps in there.

for example, they're just more expensive. Um, you know, and they're larger. And you know you're going to use little ceramics that you've already got in the circuit typically. Uh, you know, if you're doing an SMD design, you might have one microfarad uh caps in there for example might be uh, very typical or something like that all the 470 NS Um, that I was using before 47 microfarads.

And as you can see, yeah, we couldn't get the several milliamps out of there, even at the higher frequency. So as you can see, it's all going to be a tradeoff here of the value of the capacitance versus your load versus your diode. The type of diode you got. the diode drops I won't go into putting shock keys in there as well.

If we put shock keys in there, we'll find that these waveforms will all be shifted up. We'll have low, lower diode losses and stuff like that, so you know, by all means, build this thing up and experiment with it and it's a great circuit to use. Next time you need a simple voltage doubler or to get you know, a higher, uh, value rail out of your project that's powered from a couple of batteries or something like that. You don't have to re-engineer your Battery Solution You can just use one of these doublers or in this case, a tripler.

Now let's look at a practical configuration of this. In this case, it's my Microw Watch Project Here it is. Here's the schematic for it. You can, uh, download it from my Microw watch uh, website if you really want to.

but it's a microcontroller. Well, here is the actual thing powered from a single uh CR 2032 battery here? Let's switch it on. It's in power saving mode at the moment. Haven't set the time or anything like that, but there you go.

It's the world's only do-it-yourself scientific calculator watch now. Uh, the interesting thing about this is that I've Well, there's two interesting things. One's one is that I've used two Dixon doublers here. Might look a bit unusual, but trust me.

I've got one for the LCD here that powers the 5V LCD It's not a 3.3 Vol one or 3vt one, so it needs 5. Vols So I've got a Dixon doubler in there and I've got another one for the lead backlight as well. I think it had like two leads in series. That's why I had to actually, uh, do that this particular module anyway.

So I've got two Dix and doublers in there. The configuration is basically exactly like this. Of course, we've got a fixed DC voltage here. in this case, 3 volts from the battery.

We've got our Uh 3v Square wave coming from our pick microcontroller in there. But in this case, of course we're only using a single stage doubler here, so ignore the rest of that. There we go. That's basically what we've got here now.

It might look a bit unusual in that. Well, why aren't these diodes here going to 3 volts like this? Why are they going to a pin on the microcontroller? Aha, that's actually a feature. It allows the microcontroller to actually switch the output off and on under software control. So if the output here instead of tying this to 3 Vols you tie it to a pin on the microcontroller when that's high.

3 Vols you apply your Pwm signal uh, well in there. then it switches your LCD voltage on or whatever it else you want to power. If you set that low and switch off your Pwm signal Bingo your output voltage goes down to zero and I can do that for both the LCD backlight and voltage on the LCD. And in this case, I've got uh shock here of course.

a standard bat 54 really? uh Jelly Bean um. stuff in there super cheap SM Standard SMD type I've got only at lousy 100n in there and I've got 10 microfarads there on the output I actually forget what value I'm switching it at I don't know, it's a, you know, 5 khz or something like that. 10 khz don't exactly remember. But so there you go.

There's a real world example of uh. two different reasons why you want to use it: the LCD and the backlight. Uh, of course because I was forced to use this LCD 53 20 mm and it had a certain type of backlight. It had to be a certain type I couldn't use anything else.

couldn't just, uh, substitute it for anything? So really, um, you know I had to do this. this. was my only choice apart from using like as I said before, like a 76o uh voltage uh doubler, uh, charge, pump, voltage doubler or something like that. Eh, it's more expensive.

So I just decided to go with the diode and capacitor solution piece of cake and then I added in the bonus feature of being able to switch off the LCD as you've seen, it goes into power down mode that actually disables the Uh voltage to the LCD so it doesn't uh, draw any current at all and this thing can actually get a reasonably long battery life cuz it's only powering the microcontroller. The LCD I can completely switch off and of course the backlight voltage I can switch that off and on. There it is. it's g into low power.

State It's only drawing. You know microamps instead of you know, a milliamp or two and you switch it on draws a couple of milliamps, operates for a few minutes, then Auto switches off. real world Practical example of a tricked up I guess uh Dixon Douer here with onoff capability. So there you go I Hope you enjoyed that.

Followup to the Cockro Walton Voltage multiplier. this is the Dixon doubler or Charge Pump Doubler Diod doubler, whatever you want to call it. It's an interesting little and useful little build-in block circuit. And remember, if you like uh fundamentals, Friday please give it a big thumbs up.

Jeel thumbs up. And if you want to discuss it, jump on over to the EV blog. Forum Catch you next time. Greetings: Professor Fan: Shall we play a game? How? I Nice game Gentlemen I Wouldn't trust this overgrown pile of microchips any further than I can throw it.