EEVblog #504 - UPS Tutorial & Teardown

hi welcome to teardown Tuesday yes I'm at the whiteboard we're not going to jump in to the teardown thought I'd just do a little bit of white border fundamental theory today and then we jump in to the teardown and see if we can see a similar arrangement to what we get in the basic topology of in this case uninterruptible power supplies or UPS you've no doubt heard of them you're probably using one at home to backup power your PC for example when the mains power fails then the battery inside the UPS takes over and supplies power for five or ten minutes or maybe even longer so that you can continue to use your machine or at least it gracefully can gracefully shut down and save your work for example so the power just fails boom it doesn't just shut off you lose everything so very common device the UPS there's actually three types so basically three different topologies as a few more but these are the three basic types which we'll have a look at there's the offline standby type probably the most popular you'll find in the really cheap ones as line-interactive which is the one we'll take a look at today in the teardown and there's the full online slash double conversion type which is the more expensive and more reliable types for the more robust application so if we take a look at the basic offline standby one you're probably familiar with how they work we've got AC mains coming in here AC mains going out that's it and inside we've got ourselves a AC to DC rectifier here yes it's just a traditional bridge rectifier or whatever and that goes into a charger which then charges the battery and then the battery goes into a switcher aura which is usually a h-bridge arrangement but doesn't have to be but it basically a switcher driving the primary of a transformer and the secondary of the transformer produces is sine or square wave out and then they've got a basic switch in here which can usually this thing by meaning offline it means that the the charger and battery out of it is usually offline so it's switched out and your a/c is switched directly through to your output like that so only when it detects that the main input mains power has failed does it rapidly switch over so I haven't shown any switch in here but it rapidly R starts up the inverter in here you step up conversion here and generates your sinusoidal or square wave output voltage and it you get usually you know it can take you from you know tens of milliseconds or 100 milliseconds or something to sort of switch over and start up so the device that you're actually pairing has to be able to handle that little sort of you know drop out or Brown out as it switches over to the battery back up now that is the cheapest and most common one now skip this line interactive one for a second and we'll jump straight down here to the on line / double conversion type you'll see why it's called double conversion in a second now the difference between these two basic types is that this is the off line type as I said the it usually the output is powered directly from the input it's switched straight through so it's the battery backup part of it is off line but you guess that the on line type is where the battery is continuously powering the output here regardless of what the input is doing and that's why there's no switch going through them the AC input through to the AC output because it's or that power is always coming well not necessarily coming from the battery but actually coming from the DC rectifier down here and you'll notice that all of the you know all the common components are still there they are virtually identical we've got our AC rectifier down here we've got our battery charger we've got our battery we've got our switcher with our step-up transformer to generate either your sinusoidal or your square wave output but you'll notice that there is no switch connecting it can't bypass any of this stuff it's always working and what we're switching here instead of switching from input directly to output we're switching basically whether or not we want to power the output the battery or from the rectifier circuit down here and that's one of the big differences what are the main reasons you want to do it is for isolation for example you notice that there's no directly direct electrical connection from the output to the input ie it's galvanically isolated so if you if you're the device you're powering needs to be electrically isolated from the input then an online or double conversion switcher is the way to go but as you can see here there's no isolation even though we're going to transformer in there you'll notice that it's all common like that from the input to the output and the other main reason why you want to use the online one compared to the offline is that if you've got a real noisy mains and it's always dropping there's always brownouts and dropouts and all sorts of stuff you don't want this thing to be continually switching back and forth between the input and the input and the battery for example you're much better off on those new in those noisy and troublesome environments to go for and online conversion where it's just always running from the DC here and that's why it's called double conversion because we're converting AC into DC and then it's permanently the output here is permanently running from that DC connection is not switching through the AC and then switching between AC and DC of sources effectively it's always powered from that DC source and that's why they call it the double conversion because you're converting once and then you're converting again yes this one does it up here too but there is the option to switch through with no conversion at all hence the name double conversion but one of the disadvantages of this double conversion type is that when you notice that this switch down here is switching the relatively low voltage battery for example 48 volt battery might be typical they might be using 12 volts for example then lower voltage Ohm's law still must apply right that means for the same amount of output power delivered to the load you've got much higher switching currents in here so I've shown this as a you know mechanical switcher relay and the topology doesn't exactly need to be like that but it it basically means you've got very switching parents in here that you have to switch from the battery up here if you're got say for example a typical tener mains now let were you only need attentive relay in there that's it not a problem but down here you need much much higher current so the switching can be an issue down here and also this rectifier down here has to deliver the full load all the time because you notice when it's a not powered from the battery it's got to deliver all that power from that Paul little rectifier down in here where as here the rectifier is only only needs to be sized enough designed well enough to deliver enough power to charge the battery which might be much much less than the output load is capable of so that's why these things are more expensive and more difficult to design they're going to run hotter things like that because the circuitry inside is got to deliver that full load and then you've got losses in there and the switch has always got to be operated and delivering the output load whereas up here your switcher or output load might only need to be sized and designed for operation for 10 minutes 30 minutes for example with this thing it's got to work all day everyday 24/7 so this thing needs a lot more cooling and much better design system so that's why it's typically art more expensive to design and on line ups so that brings us to the third type which we're actually going to look at in the teardown today is what's called a line-interactive UPS and it's essentially exactly the same as the offline standby type it's a bit of a compromise between these two in that let's say you've got you know a and mains input here which sort of you know brown and browns out or drops out you know a couple of times a day you don't want the thing always switching over to battery so instead of it switching over to battery what they include in here you'll notice it's virtually identical except for the fact that in this path here was the AC s switch through there's actually what's called an autotransformer in there with various little taps with some other switching relays in here that can or it doesn't have to be a relay it can be an electronic switch as well then it switches between the different taps on the transformer so let's say your mains input not only 240 volts it drops down to 220 or 210 then bingo what they might do is then switch to this tap here which then the output voltage is going to be boosted up a bit so you're still going to get your 240 volts out it can compensate for small variations you know 10 or 20% variations in your mains input if you're the device your parent cannot handle that them and then likewise if the mains input here goes up goes above what you load you know it really wouldn't like to have then it can switch in this tap here you can switch over to here and then you'll notice that the output is going to be somewhere below because it's a different tap somewhere below that mains input falling so it can accommodate both higher and lower input voltages without having to switch over to the battery backup system so that's what a line-interactive UPS does sort of a compromise between those and that's what we're going to take a look at now oops I forgot to include that little line in there perineal AC rectifier there but when we take a look at our teardown now which you're going to do in a second we expect to see all these basic components in here we expect to see a big-ass auto transformer it's going to be big-ass because it's delivering all of the full output power load before you know 2400 watts or whatever through to the output so that's got to be a big beast then we're going to have our rectifier we're going to have our charging circuitry we're going to have our battery bank in the case of this one I know it's at 48 volts then we're going to have our switcher most likely h-bridge configuration we won't know until we turn it until we actually take it apart of the h-bridge configuration is going to have four large MOSFETs in there driving at the primary side of the step-up transformer which could possibly be integrated into the main auto transformer here with another tap we'll see when we open the thing and and that's pretty much it we expect to see some big-ass relays to switch the taps awesome electronic components to actually switch those instead most likely we're going to see our relays in this thing and that's what we expect to find will we only one way to find out taken apart and here's what we're tearing down to they please excuse the fact that I've got this thing on the floor it is a massively heavy beast it weighs more than a brick dunny and I'm sure it's built like one as well what it is is an APC they're a top brand in the UPS business so we expect top quality it's a smart UPS model 2200 XL as you can see a rack mount unit designed for our server backups and things like that three unit high rack and yes I scored this one from the Australian Defence Force auction that I scored a whole bunch of other stuff as you've seen in a previous video and this is just a front fascia panel here that just pops off to reveal the control panel here and the internal art battery pack I do have a second rack mount unit which just contains an extra two sets of batteries as well and you'll see the other connector on the other side so this one can have three sets of batteries hooked up to it it's a model number is su a 2200 RM XL to be precise and you can see on the control panel here why it's a line-interactive UPS we've got two LEDs here one to show that look what happens when like to show you indicate that the mains voltage has gone over voltage and then needs to correct and pull it back down so it needs to switch in that extra tap there and then likewise down here if the mains voltage is sagging it needs to pull it up and correct it like that so obviously it's switching in the taps on the auto transformer there and there's charge level and various other stuff bad battery and whether or not I think that led is for a riot comes on when it's are powered from the battery and there's some test functionality as well it's got a anderson connector on here by looks of it for the battery bank and that just swings around and we can pour I've undone the screws on this we can pull the sucker out it needs a bit of percussive maintenance I think hey yeah there we go there we go we got it better percussive maintenance and the battery weighs an absolute ton more than a brick dummy as I said and that will pop out but the thing is even with that is still very heavy so obviously there's a huge monster auto transformer in here so we expect to find that you can see it comes in two models we got the lower one here the 22 hundred watt one does come in a 3000 watt one which are maximum input current at 15 amps and that's what will an output rate in our 2700 watts this is nineteen eighty watts so almost 2,000 watts output pal you see it does have a 15 amp mains input jack there what i've got a USB interface we've got a serial port and a p oh that's emergency our power off and there's the X and there's the other anderson connector the second one which goes off to the battery pack the external one which i've got to this I believe is some an option slot there's nothing underneath that's I'm not sure what's actually installed in this thing I haven't done you know actually being able to power up and communicate to it or haven't even tried but there's all the output connectors big whopping 15 amp 1 + 8 10 amp outputs as well or wide in parallel of course so of course you can't draw 10 hours from each one you're limited to that 2700 Watts total so that's all those outputs are more for convenience sake all right got my cordless drill this time to white help out there's a few screws on this thing so let's crack it open and as I said what do we expect to find well pretty much exactly what we saw on the white board there we expect to find a big ass auto transformer of course that'll be the bulk of the weight in this thing it'll be absolutely massive and we expect to find a rectifier that'll be pretty beefy to handle all the charge current for these batteries I'm not sure what it actually charges that but I'd expect that to be pretty darn beefy as well has to be especially when it's out charging external battery packs will most likely find a huge h-bridge an inverter in there we'll find some massive wiring for the batteries and all that sort of stuff in the H bridge because there's so much power involved I expect the not to use a single MOSFET for each branch there there's probably multiple ones in parallel that would be my guess anyway so we'll give it a go all right let's lift the lid on this thing and see what we get no it's nothing else holding it down tada oh look at that we have two transformers we'll get a better look at this beast I'll set the camera up our vertical above it but yeah that looks very nice at first glance ah beauty now first of all that was a bit of a surprise we've got two separate transformers here I expected one huge transformer but I guess I don't know for technical or manufacturing or performance reasons they decide to go with two separate ones but if you'll notice that there's a huge cable over here I love the fact that they've actually clamped that down there with a crimp Logan they've screwed it down you'll notice that there's no connection from basically this is the this is the primary of the transformer well I depends on which way you're talking about your terminology if it's powered from the batteries then this is the primary then this becomes the secondary so we'll just call it the battery side of the transformer you'll notice that there's a huge bridge joining those two but there's no tap coming off that into the main circuitry so really it's effectively just one winding there so they're using this as one big transformer so it's not a center tapped winding on that so they're definitely using a H bridge to do it and if you have a look down in here today you will be able to see that here's where the wiring that comes off and once again huge big I crimp terminals screwed into what looks like the hits and well it is the heatsink for the power MOSFETs the switching MOSFETs down in there which we'll have a closer look I'll get the macro lens out see if we can get some part numbers in there but they're also using that to carry the current down there as well and you'll notice that there's one two three four so I that looks to be correct it looks to be a H bridge because that's the most typical configuration so it looks like we're going to have four sets of power MOSFETs here each on their own thing each other a little heatsink a slash current conductor there and you'll notice that so these two there's one over here so this top one is the black wire which goes over the transformer or one side of the transformer the other side of the transformer goes to this part of the bridge and then the battery will be connected to these two interwebs and that H bridge arrangement switches the battery and then alternates the supply onto the transformer and we can see that H bridge configuration on this Dave CAD drawing here please excuse the kurudi of the model didn't have time to build up the scale or to paint it what we've got is that for MOSFETs here and you can see why it's called a H bridge because it looks like a haitch if you take out that line there and take out that line there it looks like a CH with the transformer in the center taps there and we've got our 48 volt battery across here and we've got two P channel MOSFET off the top or as we'll see in this case down here we're going to have multiple ones in that parallel but it's exactly the same thing they just are getting higher power dissipation better power dissipation there so um basically I went going to H bridge in detail but basically you can switch pairs like that which then you can alternate the polarity on that u transformer there so that's how you can switch it but then if you just switch them off and on and had just a simple square wave output which the cheaper UPS's do because when you turn on a mosfet you know they've got very low on resistance so that when you are you know if you just do a square wave output then these things turn on hard and there's not a huge amount of power dissipation in these MOSFETs or they try to you know there's things with gate capacitance and everything else but and driving conditions we won't go into any of that detail but because we're getting a sine wave out of this thing we're going to have to dissipate more power in the MOSFETs which is probably why they've gone for the arrangement with you know this huge huge big heatsink and it looks like they've got four parallel MOSFETs on there as well but you can clearly see that's the configuration we've got we've got our transformer hooked on to our two of the taps effectively on that h bridge the centre taps there and then we've got our battery hooked on to these other two down here if we follow the wires we'll find that they actually these two plates here go down to the battery pack find it rather interesting that they've got a quite a hefty amount of capacitance there across the battery terminals not sure why they're doing that there are fifteen hundred microfarads at seventy five volts I can't get in there to see the brand at the moment it looks like there's three of those in parallel and of course not an ideal location being stuck between these two heat sinks which are likely going to get quite hot but as I said only because this is not a full-on line ups this thing is not used or running 24 hours a day so this is going to be dissipating you know nothing basically until you switch until the mains power fails then it switches on and then dries a transformer to power your load and it does appear that the battery the internal battery pack is just wired in parallel with these cables which go off to the anderson connector on the output so it looks like all the battery packs when you use the external ones just all wired in parallel basically and of course we've just got our positive and negative there there's no smart and you know there's no like that sense wire or anything like that but of course some maybe if they wanted to maybe they could be passing some sort of art sense data over the power as well I'm not sure I haven't gone into the details of how that works I find this rather interesting check it out they've got two fans here the biggest one here which is obviously blowing air directly over these large heat sinks here so I presume that that sucker only turns on when you're when it's actually up powering the load then they got a small little you know wimpy pissant one down here which might be running all the time or something like that just to get some airflow through the system and they've got an additional fan here which looks like it just yeah I can just put my finger through there and spin it so it looks like it's just a sucking some air over the battery compartment now as for the main board down here there's just one board it looks like it's all a combination of surface mount and through-hole just single sided so I'm not going to take this whole thing apart because I don't expect there to be anything on the bottom of this board of any note whatsoever looks like it's big enough sparse enough for all the SMD stuff to be on top and anything of interest is going to be on the top anyway so we've got our mains input over here securely are clamped down to the chassis down there with earth and I remember as I said because this is a line-interactive UPS it is not isolated so the transformer is an auto transformer so the output the mains output is not isolated from the mains input anyway if we have a look down here I should probably get a shot of that but you can see the flow through here we've got our input field here we've got some these five five relays wonder yet five realize there's our relays used for we're going to be switching some taps down here so here's the anyway if they flow through we've got some protecting we've got some common mode choke line filler in lots of Moorefield in it looks like we've got a current transformer down there and here's our output line so it comes straight through the input from the input straight through some filtering and some surge protection and stuff like that and then straight off to your output connectors over there and then we've got the switching of our auto transformer here so it looks like these couple of relays around here or these two are probably your high side and your low side auto transformer switch it I can't see any electronic switching these things are are what are they 20 amps so then 20 amp power relays mains are traded of course so there are definitely going to be able to do the job and they switch the taps on the auto transformer over here so it looks like we've only got one on the high side one on the low side so not particularly they're not catering for various US steps it's basically is it higher than a threshold yes switch on a transformer and then pull the output voltage lower and the same thing on the low side as well got our fan outputs there whoops also got a second current transformer down in there and that's all she wrote let's get some close-ups have a look at our input circuitry down in here we can see a mod directly on the input there and then we've got a classic common mode filter here common mode choke with some filtering moving along we've got a couple of extra inductors here and then we've got some more filtering large huge filter caps down here and then there's our current transformer there it is yeah it's even labeled CT CT one you can see that they've got a single wire going through a little transformer coil there so they can just get an isolated tap off that and they can measure the current coming from the mains input and they've got our sight and then we've got a bleeder resistor there by the looks of it then we've got ourselves another current transformer down in there that would be measuring the output current and of course I'd be tapping the output voltage as well as the input voltage of reading those so they can get the output power and the output voltage so yeah pretty obvious mains input here and then we've got our the other one over here is measuring the output and these cables here then bugger off to our output over here and as you can see yep they're all wired in parallel there so there's not there obviously got suddenly got a separate why they're going off to the 15 app jack and then all the 10 out Jack's are wired in parallel and we've got ourselves a little flow not a little a big ferrite and I probably say that this third relay here is the one that actually our switches the input are directly through to the output basically until look they've got this huge beefy well that's actually coming from this one here I mean huge beefy tracks in there I mean check that out join and then the output of course big beefy ones going over to here so I don't know of the exact type all adji they're actually using for the auto transformer and the power bypass but yeah these ones are also got beefy power tracks going through them as well so make up your own line trace it out if you want to and we've got more protection here another move there and another move over there so there's no shortage of protection in this thing as you'd expect because they actually claim it's part of the functionality of this UPS is to basically clean up your input mains waveform it you know it it filters it and it clamps it with some mods and then with the auto transformer configuration actually can slightly adjust and correct for the input voltage now there's one thing that I'm is starting to puzzle me I'm not quite sure about is that where is the rectifier and the charging circuitry in this thing saluté look we've got to isolation transformers down in here if we take a look at these you know there they are there but they're you know really small fry I mean you know not a huge amount of power at all expense especially for the battery pack so these are clearly not charging the battery packs but if you saw our topology on the whiteboard then that's what it expect I expected a really big another big transformer in here just and an some big rectification and filtering and everything else we got we've got some filtering happening over here but it's directly across the batteries rather than at the output of any rectifier so I don't see any power rectifier in here these are obviously just little low power isolation transformers to power all the circuitry underneath here so I mean I can take out the fan there but I don't think there's going to be anything I'm doing there at all so I'm rather rather puzzled by that they're obviously doing it some other some other way no no they've just got some control stuff under there no there's nothing so it's this thing is clearly not working like our classic topology we had on the white board up there there it is well there's a new perspective now I've had a little head scratch over this I rectify a thing and some people have probably screaming at me right now saying oh yeah it's obvious and ER it is obvious when you think about what they're actually doing here and it's a rather clever I think um this is my first thought of what they're doing and it's off why they've got a huge amount of capacitance in parallel with the battery here and no other I mean clearly there's no other you know a charger CA air power charger circuitry or rectifier so how are they doing it well they must be doing it by tapping off the output of the transformer so the transformer is not actually are switched here they're actually they're always feeding power back through the transformer back in the other direction back into and use in the H bridge itself to actually charge the batteries it's rather clever this is the only way that they can be getting away with it because we need a huge amount of power to charge these huge battery packs and the only power devices in here are the H bridge devices themselves actually I probably should have a look down here I might be jumping the gun but what I haven't shown here on my Dave Kerr drawing what I emitted because I thought it didn't matter is the substrate diode across each one of these and there's going to be one of those our substrate reverse bias diodes across each of these MOSFETs are we going to details of why but all MOSFETs are going to have these substrate diodes in there and when you have diodes like that in reverse bias you can feed power back in from this transformer and then you can actually have a huge amount you know large capacitance across here like this well across there and there you've got large amount of capacitance and that's what we've got we've got this cute three huge caps here and I think they're feeding power back in from the transformer through the reverse bias substrate diodes filtering that out and using that to charge the batteries that is incredibly clever I really like that now you may or may not be able to see that but what we've got is for international rectifier IRF b-47 one zero power MOSFETs in there there hundred volts 75 amp rating 14 millions on resistance and they're clearly parallel in four of those up and there's room for another four in there so obviously the 3,300 watt amp model would have fully populated power MOSFETs in there so they're getting away with four and they're tapped into holes directly on the heatsink or well it's not really a heatsink it's actually used as the main that current carrier as well quite neat and if you try and have a look down the heatsinks at the other ones you can see that they're exactly the same there'll be two with p-channel MOSFETs and two with matching end channel MOSFETs of course and I don't see anything else down in there there's no huge power diets or anything like that sharing the heatsink so there obviously there's just some caps down in there you can see those things down there and really there's nothing left for me to conclude except for the fact that they must be doing exactly what I said there and using the substrate diodes on here reverse biased - then charge up well into there and then they rectify that so it's effectively rectifying the AC coming from the output when you're plugging in the mains it's coming back from the transformer and they're just rectifying that and filtering that and then charging the battery from that there's probably some you know more smarts in there of course actually taking care of things but that's the basic topology that they're using that's very clever and if we get rid of that option slot which literally is an option our slot and that net just plugs in that rhythm cable just plugs in there it's not populated in my unit but you can get like I believe you can get like our Ethernet interfaces and various other art management modules and things to plug into and as you can see it looks like we've got a socket at micro there or maybe try and get a close-up of that looks like we've got a USB mic capable micro here - dead giveaway it's right next to the USB we've got an rs-232 you know probably a maximum serial driver in there and that's about all she wrote not a huge amount of control you know we're obviously going to have some analog to digital converter stuff around here to measure your voltage coming from your the current transformer and also measuring the mains input and output voltages as well to try and track that power and of course the battery management charging capability as well and for those who absolutely must know what the main processor is I peeled off the sticker there it's a Phillips 87 c-51 classic now it's curious about how that charging system works so what do you do when you want to find out info on how something works well look at what we have here on the back US Patent Number five million three hundred and two thousand eight hundred and fifty-eight let's look it up and bingo look what we have here sometimes you just get lucky now at best I expected maybe to find a snippet of information on how the charger system worked in the patent application and but we haven't look what we found here method and apparatus for providing battery charging in a backup power system it is exactly what and it turns out it's exactly what I thought was happy nor pretty you know pretty darn close to it so this is where I love Google patents that pops up just type in Google and the pattern number here's the pattern number and it's got all the images and the full text of the pattern and it's fantastic I'll link this in by the way so that you can have a look to your heart's content and here we go we have some images popped up here and they've got some prior art here what they're showing is that this is how a traditional UPS works with the what they call a static switch here the exactly the switch we showed on the whiteboard there then we've got a a transformer rectifier configuration converts AC to DC then we've got that battery charger surgery our battery now inverter h bridge and then our output transformer powering the output and that's the prior art but what they've got this pattern for by the looks of it I haven't read all the details of the pattern and what everything does but I've got the general overview of it and look what we have here it's the same as before you go to AC input here you've got your switch which goes through the output but there's no charger that we had before there isn't look there's no I rectifier here and there's no charging circuitry and that's exactly what we found when we open this thing it looked like there was no charge in circuitry effectively and there was no rectified power rectifier in there and power charger so what they've got is the original inverter the battery for deriving the output and what they're clearly doing is permanent connecting the output transformer instead of switching it between the input and this is permanently connected to the output and that back feeds power into the inverter here through those are body diodes of that MOSFET and then are charging the battery here and they've got to control a circuitry to power all that they're obviously monitoring the input and output currents and voltages and everything else but that's basically working exactly like I said if we take a look at this figure here they're actually showing some of the details are showing an ideal transformer here but they're obviously showing you know the winding inductance and stuff in there because that obviously has something to do with that this store in the energy in the winding inductance is in there to actually back power the charging circuitry of the battery and look they've drawn in the body diodes their substrate diodes on the MOSFETs there and that's exactly what they're doing now they're showing the AC input here and if you flick it over and we rotate it whoops there we go then they're what they're showing is that they are powering the well they are taking the line output voltage and then using the winding inductance to then supply power back through those diodes that I show any filter caps in here of course they're grossly simplified this in the pattern diagram it's not going to show anything they don't need to and but that back charges the battery and it is very clever as I figured and look they've got they're showing various configurations here and you'd have to look up the text and all the individual points are numbered so you'd have to read the text in depth if you wanted to figure out how this works because this is how patent applications work they obfuscate everything they just you know rewrite it they take a clear technical description from the engineer who designed this thing and they just that's what patent attorneys do these change it into gobbledygook but it's all eventually there in the text so they're showing both positive and negative configurations of which MOSFETs turn on and look this is showing clearly this diode then back charging through there etc etc so looks like they've got a charging waveform here perhaps you'd have to read the Associated text then they've got some clearly some muck control circuitry here here's the battery they've got some other yeah they've got a error amplifier here with a voltage reference control ADC all that sort of jazz so that's clearly the control it looks like they got some there we go energy buildup state that would be in the winding inductance and the discharge state and energy buildup state again and you can associate that with the text description of the system operation and there's a VAR for resistive discharge curves and all sorts of goodness in there so they're showing you exactly how it works but the detail is all down here in this descriptive text and here it is in the summary of the invention here the present invention eliminates the need for separate charger transformer and battery charger conveniently used in backup power systems by utilizing the main inverter to do the battery charging bingo eliminating the separate charger lowers costs reduces complexity and weight of the system and improves system reliability because as I said I expected there to be a fairly hefty charging transformer in there plus associated power circuitry as well but this does away with it fantastic the invention provides inherent power factor correction because without the need for any additional control circuitry the inverter charger draws a sinusoidal non distorted current from the power lines brilliant another side benefit is and here's a bit more detail the president invention utilizes the primary and secondary leakage reactances of the main power transformer in cooperation with the switching devices for the H bridge inverter the consequently the battery pack will back a bias diodes intrinsic anti parallel diodes conduct connected across each of the switching devices in the inverter bridge brilliant that's exactly what I thought but in the end like when I you know thought about it for five minutes it was obvious due to the lack of various components that you know this was exactly what they were doing there was no other way to do it and it also tells you the inverter may be operating in constant frequency inverted charge mode or a variable frequency mode as well yielding a higher charge current so there's no they can probably chop and choose under software control what method they want to use fantastic and this pattern isn't new either it's a dates back to 1991 it was granted in 1994 and it was done by a guy named Mark Douglas see faults good on you Doug and he worked for a company called best power technology I have no idea who they are or how they're associated with a PC I haven't checked but maybe they got acquired or maybe it's Doug's company who knows anyway one smart cookie invented this and presumably nobody in the UPS business has been able to implement this I don't know what you would call it you know reverse inverter battery charger technology or something like that nobody else has been able to implement it because they would presumably violate the APC patent on this thing or I'm sure there's people out there using they don't care and you know they're in another country and well it's you know it's a real difficult and expensive to sue them but anyway and it's has the patent expired I don't know what is it 20 or 25 years on a pattern or something but presumably a PC have been the only ones that have been able to incorporate this sir novel this novel technology I mean there could be you know prior art just because they grant the thing doesn't mean that it's you know enforceable and stuff like that if you can find prior art to beat it then you can easily well not easily still cost you a buttload of money to win any pattern you know infringement lawsuit that's for sure and that's a disadvantage of these patents you think you're protecting your design and well you're not because here's all the details in depth of how it all work so it doesn't stop anyone copying it it puts all the info out there so that anyone in the world can copy it but what it does do the patent is gives you a right to sue them very expensively if they do so there you go I hope you enjoyed that look at a - well a combined tutorial teardown a Tuesday I guess you could where I started off with some theory I thought uh you know some basic theory on how these things operate see how well a product when you take it apart matches the basic theory that you'd find in any textbook basic block diagram approach and usually you know it does but in this case it actually surprised us and it's a good example of how and why I like taking things apart because you often find surprises like this I hadn't heard of this technique before but it seems obvious with the hindsight maybe it is widely used in the industry I'm not sure but anyway that was a rather interesting I found something I didn't know I'm gonna have to read further about how all this works but it seems to be a very clever little technique and I bet there's a lot of people out there that didn't know about this either so there you go some benefits to tearing stuff down and investigating things I love it and if you liked the video please give it a big thumbs up on YouTube and if you want to discuss it jump on over to the Eevee blog forum catch you next time you you

Channel: EEVblog

Views: 273,195

Keywords: ups, Uninterruptible Power Supply, apc, patent, patent application, power supply, desing, tutorial, how to, transformer, online ups, offline ups, line interactive ups, how it works, pwm, battery charging

Id: Fj7e3WGUKO8

Length: 45min 49sec (2749 seconds)

Published: Tue Aug 06 2013