Now, this is actually starting to look an awful lot like a resonant mode controller. It just makes sense. Walk, It's a basic generic resonant mode topology, but I think we're going to see that line up here. We've got ourselves our four diodes down here.

We've got ourselves four MOSFETs under here and down on their own heat sink down there. There are four Sixty are three sixties. So yeah, I'm pretty sure this is a resonant mode power supply and that makes a sense. Now we go into a full tutorial on resonant mode power supplies.

Workers? that'd be an hour video in its own right and it can be quite a complicated subject. If you you know, go into the deep dive into the maths of it. So what we had up here is our four: MOSFETs I'll show you data sheet for those in a minute because that's the tail and under here. We have our four diodes as well, and we've got some transformers here and a big-ass inductor like this.

so that with the four MOSFETs and the four diodes, that is a classic configuration for what's called a full bridge resonant converter. So we'll show you the topology in a minute. But the datasheet for these well pretty much prove it. And those MOSFETs that we saw under their surprise surprise look at this.

600 volts Cool! Maas I'm in a CFD seven for those playing along at home. SJ MOSFET in Finian's answer: Two resonant high-power topologies. Bingo, We got it. Um, the is Phineas latest our high voltage super Junction MOSFET technology with integrated fast body diode.

A couple Men in the Cool. My seventh is the ideal choice for resonant topologies in high power switch mode power supply applications such as Server Telecom, Evie charging stations, and all that sort of stuff. And you can go into the technical details about why this is the best in the business and stuff like that Anyway, yeah and they compare it to all their competitors, blah blah blah blah blah. But anyway, yet that's the job' that's used in here.

So yeah, this is a resonant mode controller and it makes complete sense because they're trying to put an 800 watt power supply in order to rack unit case here. So efficiency is very important. You can't piss away any power in your head sings because then thermally, you've just got to get all that out and the airflow and everything else. It's just, it's horrible.

So you want to make this thing as efficient as possible and that's what resonant mode converters to. They are higher our quiescent current supplies, but when they're actually switching at full power, they are actually more efficient. and I explained why I Found this application. Note from Infineon I'll link it in down below: Resonant LLC Converter operation and Design and it has a good generic application circuit here and I believe this is pretty much what we're saying here.

This is why it's a full bridge. now. you can actually get a half bridge a resonant our converter as well and they're very common which of course will only have if you aware of your for Britt you know your H bridge you can get a half bridge would only have the two MOSFETs and would only have the two output diodes. but in this case we do have physically four MOSFETs and four diodes on those heatsink.

So this is what's going on here. Now how a resonant mode controller works is that it's basically a switch in series with an LC tank circuit, a capacitor and inductor tank circuit here, and that forms. that's where the name comes from, hence resonance. It's resonant mode, so it actually switches on the resonant point of the L and the C here and then you've got a transformer which then couples that and that's where they get in their isolation from of course for each channel and then the output is just a regular full wave bridge like this.

but it's the switching in here at the resonant point of the LC tank circuit that reduces the switching losses in the converter and hence the heat dissipated during switching. and there you go. You can go into the here mass of it for though and it gets more complicated than that - that's the equivalent resonance circuit and the quality factor and blah blah blah. all that sort of stuff and then you can get into the regions and things like that and we were going to factors.

It gets quite complex. So the thing with a regular switch mode our topology that you used to with your Regulus in transistor is that it's switching it basically like digitally like high, low, high, low, high low like that and the switching losses can be quite high, particularly the higher frequency you go because you want to make it more efficient so you go to a higher frequency bit. At the higher frequency, you get greater switching losses with that sort of thing. whereas with a resonant mode converter like this, it actually changes the wave shape the switching wave shape so that there's effectively less losses.

Oh oh, try Dave Cut it. Oh and you can see the various are switching waveform. so if you want to go through step by step how it works, this application notice are pretty good and it just goes through and it explains each cycle, etc. etc.

And it shows some of the waveforms too. But let me try and explain something here. Please excuse the crudity of this model. I Certainly didn't have time to build it, the scale or to paint it now.

and this one on the left here is let's say the switching I'm simplifying this. Let's say this is a switching platform for your typical converter which is switching hard like this. Okay now this area in here and under Here these are you can consider those the power dissipation, the losses in your switching elements which are is heat that you have to get rid of right? So that's the efficiency of your converter, but a resonant mode controller is going to change instead of like a hard switching like I've exaggerated the slew on that by the way. Anyway, the resonant mode controller actually changes the wave shape so it's like this and I it's the switching loss is going to be smaller, but basically what that does is it reduces the amount of switching losses in here so it's smaller and you can get a dramatic difference in the switching losses in your converter from a just a regular switch mode topology whichever one you want to choose which is hard switching versus a resonant mode switching which is using the L and C to change the wave shape there and you just get basically area under the curve if you losses is less but as it's not some magic bullet, that's why not everyone uses switching mode converters because the losses will actually in low-power state like in effect.

quiescent power dissipation is going to be potentially higher for resonant mode stuff, so you know. but for large output power support lives like this in a small amount of space where you want to make them as efficient as possible. Resident modes a decent choice. And by the way, in this particular case, if you are actually using only half of the sinusoid the resonant LC sinusoid like this then it's what's called a quasi resonant converter and you might have heard that.

And the other thing with resonant mode controllers if you haven't already gathered, is that they're more expensive and more difficult to actually design and tweak and get right. So hence they're only used in like really top-shelf power suppliers like this one. and you know, like you can just have a look at like all of the all of the analysis required the equivalent revenue resonant circuit and this is just our first harmonic analysis I believe of it. that's you know, pretty much all you need to do, but you can go further down the rabbit hole as I said.

but yeah, actually getting just the tank circuit right and and the ratio, the turns, ratio of the transformer and the various inductors and various modes and things like that and the parasitics of the transformer and and in some cases the transformer over here is is gonna not be as like as well determined as our specific inductors over in the LC tank part and things like this and matching all this and getting it all right and figuring out all this sort of stuff look I mean this is just right, right? Yeah, we're getting really serious and modes of operation and getting alright. so it's pretty much vastly more difficult to actually design an engineer one of these than it is for your more traditional our PWM you know boost Bucky sepecat type converter that you're used to doing so yeah, you really only see these on like, really pretty much top shelf our power supplies. They've even got a flow chart Design step here. Killed one of the Q max values fine FX minimum is k max require it required Gained all this sort of stuff and like you choose your resident component values, it's just it's it's seriously like selecting the M value for example.

So you've got to understand the formula up here and figure out what your M values doing. Of course you can just like kludge it all and kinda sorta make it work, but that kinda defeats the point. So here you've got to know the ratio of the total primary inductance to the resonant inductance. so you've effectively got your resonance inductance here and the new primary inductance in your transformer.

You've got to match all that and all the parasitics involved in that, and it's complicated here. Any resonant mode switch mode design expressed, let us know in the comments down below if this is your day job designing that resonant mode controllers because yeah, a lot of effort went into doing this. Let's just put it that way. So here it is like this is for different values of M for example like M3 M6 for example and how this like it flattens out the peaks here so lower em values going to give you higher boost gain, narrower frequency range, more flexible regulation.

but if you want higher efficiency you've got to go for the higher M values. but then you get higher magnetizing inductance and I it's just yeah. I know So yeah, like knock yourself out. Oh I'm at resonant mode power supply desired voltage gain Verification: look at this as I said.

I'll link this down below present and then you finally once you've done all that, engineer and you calculate a resonant mode values and then bridge and rectifier a selection. R for example. this is why they used MOSFETs in here. there's basically two.

You really can't do this with bipolar transistors because their drive requirements are too much So really, you need a very specific in this case, highly optimized MOSFET one that's carefully tailored for this kind of a specific resonant mode operation. This is what they are designed these specific MOSFETs for and if you want to know the difference between a full bridge and a half bridge one, how and why, here you go: The Although a half bridge requires half the primary turns for the same voltage gain and magnetic luck swing, thus half the primary winding resistance, the primary copper losses are of course double compared to the full bridge because the squared RMS that pesky I squared R thing. the squared RMS current in half Ridge is four times. so it might be cheaper and simpler to design a half bridge resonant mode converter.

And as I said are, they're relatively common. But yeah, for the best performance in like a top-shelf product like this, you're going to want to implement the full bridge converter definitely. And here's where they talk about the output rectification as well as I said, you can actually do a full bridge rectifier for a common transformer like this, but then they're going. You've got to have like a center tapped transformer if you want to do that whereas this one is not sent a tap so you're probably larger transformer maybe there's some you know design extra design losses and things like that so you might be better off for the full bridge.

So there you go. There's a summary of the full wave output rectifier compared to the full bridge and this has got like essentially nothing to do with the resonant convertor side. that's over on the primary side, this is just the secondary side. so diode voltage radians got to be times 2 number of diodes.

but you can save cost on your number of diodes. The conduction losses are divided by 2 the number of secondary windings, but you've got to go up by 2. As I said, the resistance per winding goes up by 2 and the IMS current is a square times square root of 1/2 and transformer secretary copper losses times 2 blah blah blah blah blah So you know there's a big trade-off there. and by the way you'll see are these resonant mode controllers often like a half bridge type actually implemented in something like a backlight for TV backlight, our power supplies and things like that they're just trying to basically I get the losses down and these do a pretty good job at it.

So they actually give you a design example here. once again. I'll leave this down below and you can actually go through the steps of actually designing a resonant mode converter step by step, calculating the resume, component values, and all these to the staff. look we need like one mic For example, for the capacitance we need 11 mic Henry's for the inductance and all that sort of jazz, experimental waveforms and efficiency.

And here's actually measured waveforms and stuff like that. You can see typical waveforms here, and you check out the efficiencies here. You know, ninety Seven and a half percent. It's pretty schmick and it doesn't drop a huge amount with our input voltage of variation I mean even.

Worst case here, we're still looking at ninety four percent, but too shabby. They've even got a reference design there. And the schematics and the Bill of Materials and everything. great application.

Note: thumbs up By the way, I Forgot to mention that these are also called a resonant LLC converters. The reason that the chord LLC is because it's pretty obvious. Let's have a look down here. There's a capacitor that's the C and there's essentially two inductors here.

because that is like the transformer primary has to be by definition part, it's an inductor two. so it's part of the LLC tank. so you have to take that into consideration in your calculations and stuff like that, so they flip it. It's even though the C is first physically in the circuit, it's LLC anyway.

So if you see that term, they're talking about resonant mode converters and basically all it's doing is are taking your DC input here and it's converting that into a square wave which then gets pole shaped by this LC tank circuit. So instead of having nice hard fast switching currents, you have nice more gentle currents or hence hard switching versus smooth switching effectively. So LC circuits are just known as like smooth switches really. And another advantage of resonant mode converters convert compared to your typical what pulse width modulation ones which as you know can change the pulse width and actually free change frequency as well.

I'm sure I've done our videos on like their different modes of operation. you know they'll go into some pulse skipping mode and then they'll go. They'll switch down frequencies or up frequencies depending upon the output current and things like that they'll dynamically change and they're actually when you've got like really broadly changing switching frequencies like that, it's really hard to filter out those sort of frequencies. So in terms of you, my electromagnetic interference and your compliance firt sort of stuff, resonant modes are actually much better.

It's it's in the name. It resonates at one frequency, so you've got a really narrow range of frequencies that you have to filter out here, and it's just much easier to filter out to put in an EMC filter for your resident mode LLC controller. And that especially comes into play at large output currents of large airport powers because when you switch in huge amounts of current, if you're doing that over huge variable frequency range, you know you can really come and got to come. EMC testing time.

So yeah, resonant mode has definitely advantages there. So you can actually see these capacitors under here like this. and they've got the same ones up under here just can't see it at this angle. So they would be our series capacitance in our topology.

and maybe the inductor is actually this baby. but the part number of these two is identical. So we need an inductor plus a transformer. so I maybe they're reusing one side.

I'm not sure Now you might think that this one here, that's the resonant mode inductor. but I don't think so because it's not. These little piddly surface-mount job is here. So yeah, and it's location is further like is looks like it's on the isolate.

You know it's on this isolated side of the converter so that that really doesn't make sense. So that's probably just part of an output filter. I'd say but yeah I'd say yeah, it's coming in here. This is our full wave bridge.

These are our caps. Let's stick with me. and that way we've got an inductor, we've got a, then our isolation transformer. We've got our four output rectifier diodes down here.

and then there's as I said, there's another MOSFET under here. so I'm not quite sure what they're doing there. and then we've just got some output filtering. So yeah, I think that's how it works.

Sure, the power supply aficionados will all be coming in down below about what's going on here, but anyway, it looks to be some very of our resident mode controller exactly how they're doing it. I don't know we'd have to reverse engineer it and that will decry ripping the whole gutsy out. So I hope you found that brief overview of LLC or resonant mode converters useful. If you did, please give it a big thumbs up.

As always, you can discuss in the YouTube comments down below or over on the Eevblog forum or even in my library comment videos even though the the comment systems still not that terrific on library. But anyway. ah, get right up there on subs. Fantastic.

Anyway, catch you next time.