The little component right here is a FULLBRIDGE RECTIFIER which converts the AC mains voltage we get from our outlets into a rather bumpy DC voltage. This might sound unspectacular but if we add a capacitor to the rectifier's output we get a smooth DC voltage that is basically required for most of the mains voltage rectification because it is cheap, rigid and efficient enough for this task.

That means it was time for the first efficiency tests/comparisons which I performed by adding a capacitor bank to the rectifier's output as well as a constant load and then drawing varying constant current with it while measuring how much input power that required. Of course to get accurate values for the output side, I also utilized my multimeter to precisely measure the current and my oscilloscope to get the RMS voltage value.

After that was done I replaced the active rectifier with a normal full bridge rectifier and basically repeated this test in order to find out that the average efficiency was bumped up around 2 to 4% with the active version, not bad. But of course next I wanted to replace all the diodes to increase the efficiency even more.

To do that I soldered the TEA2208 IC to a breakout board and afterwards to a perfboard to which I then added the 4 MOSFETs and some capacitors pretty much like the typical applications schematic recommended me to do. The result didn't look half bad but I was still very nervous while doing the first test with lowered mains voltage.

But as you can see on the oscilloscope this active rectifier also seems to work just fine, at least with resistive loads. Because while trying to charge up the capacitor bank for the power test, there appeared to be some sort of short circuit problem with the rectifier. Not sure if my design with the low cost high resistance MOSFETs is the problem or whether the topology and IC can generally not handle capacitive loads because the datasheet also states that a boost type power factor circuit must follow the application which more or less prevents current surges from capacitors.

The circuit does however work just fine with like I said resistive loads. But due to obvious safety concerns I really didn't wanted to include it in the next mains voltage power supply test in which I basically measure the efficiency of a common switched mode power supply before and after implementing an active rectifier.

The only thing that held me back once again was a familiar sentence in the TEA2206 datasheet that states that it is intended for applications followed by a PFC. And since such a power factor circuit got mentioned twice now let me tell you that it basically prevents that mains current only gets drawn near the peak of the AC mains voltage instead it distributes the current draw evenly across the whole sinusoidal voltage.

But if we got a low voltage high current system without transformation then a better rectifier is definitely recommended as we proved in test 1 of this video. In conclusion the old school full bridge rectifier is definitely good enough for most of the mains voltage rectification because it is cheap, rigid and efficient enough for this task.

With that being said I hope you learned something new through this video and now understand the advantages and disadvantages of active rectifiers. If so consider supporting me through Patreon. Don't forget to like, share, subscribe and hit the notification bell. Stay creative and I will see you next time.

WEBVTTKind: captionsLanguage: enThis little component right here is a FULLBRIDGE RECTIFIER which converts the AC mainsvoltage we get from our outlets into a ratherbumpy DC voltage.This might sound unspectacular but if we adda capacitor to the rectifiers output we geta smooth DC voltage that is basically requiredfor every modern power supply to work.So yes full bridge rectifiers are a big dealand make our modern electronics world possiblebut that doesn't mean they are perfect though.They in fact come with a noticeable voltagedrop which multiplied with the flowing currentequals a power loss that the rectifier dissipatesin the form of heat.Needless to say we want to keep this powerloss as small as possible to increase efficiencyand that is why I was super excited to findthis active rectifier board on the internetwhich apparently replaces the old school diodesof a full bridge rectifier with MOSFETs inorder to decrease the voltage drop and thuspower losses.So in this video we will not only put thispre-made active rectifier board to the testbut also try to create our own DIY versionin order to find out whether they are thefuture of rectification or whether we shouldstick with the old school solution.Let's get started!This video is sponsored by Altium!Now you might already be familiar with theAltium Designer for creating schematics andPCBs since I mentioned it once or twice before.But today I want to tell you about Altium365 which is already integrated into the designersoftware and lets you easily share your designsnot only with your colleagues but basicallythe entire world.This way you can get feedback easily and speedup your design process.So why not give it a try for free by clickingthe link in the description.First off we need to understand how a traditionalfull bridge rectifier functions.As you can see in this schematic it only consistsof 4 diodes positioned in a particular arrangementwhich I personally like to draw like thisbecause this way it is easier to understand.And let's imagine we got a resistive loadon the output across which we later shouldget the bumpy DC voltage we saw before andon the input we got the mains AC voltage.So how exactly do we go from this to thisis the question.Well, the answer lies in the behaviour ofa diode which lets current flow in only onedirection and not the other.That means that when AC mains voltage is inthe positive region we got a voltage potentialhere which lets current flow this way.And when the AC mains voltage is in the negativeregion we got the opposite voltage potentialhere which this time let's current flow thisway.So in both cases a current flow through theload was possible and what is remarkable isthat the current direction was always thesame which basically means we folded overone half wave off the AC voltage and thuscreated DC.Pretty straightforward if you ask me but thebad news is that every diode comes with acertain voltage drop which causes the powerloss I talked about at the beginning.The active rectifier idea wants to changethat by replacing the Diodes with MOSFET switchesthat come with super low resistances and thusshould decrease the power losses.Only problem is that MOSFETs are not exactlydiodes even though they come with a body diodethat also only allows one current path direction.But using the body diode is not the goal sinceits voltage drop is also rather high.No; we want to apply a DC voltage to the MOSFETsgate in order to properly to turn it on.So for a full bridge rectifier we would needsome kind of circuitry that detects when theAC voltage is either positive or negativeand depending on that only turns on the 2MOSFETs diagonally to one another to mimicthe functionality of a full bridge rectifier.Good timing is also key here because if justone additional MOSFET is on at any point webasically got a short circuit.And that is exactly why I was rather happythat I didn't have to design such a circuitmyself because I found the TEA2206 and TEA2208IC on the internet.They are active bridge rectifier controllersand can do what I just described by utilizingtheir build in comparators and MOSFET drivers.So according to their typical applicationschematic there is not much I have to addto the ICs to create an active rectifier,just some MOSFETs and Capacitors.And in case you are wondering the 2206 oneonly replaces the lower side diodes with MOSFETswhile the 2208 one replaces them all whichbegs the question why I even got the 2206version if it only does half the job of loweringthe power losses.Well, the reason that I got my hands on adevelopment board around it which I can useto get my feet wet since it should be fullyfunctional, right?To safely try it out I utilized my small autotransformerto decrease the mains voltage to 25V AC RMSwhich I directly hooked up to the active rectifier.And as you can see on the oscilloscope itdoes seem to work just fine, awesome.That means it was time for the first efficiencytests/comparisons which I performed by addinga capacitor bank to the rectifiers outputas well as a constant load and then drawingvarying constant current with it while measuringhow much input power that required.Of course to get accurate values for the outputside, I also utilized my multimeter to preciselymeasure the current and my oscilloscope toget the RMS voltage value.After that was done I replaced the activerectifier with a normal full bridge rectifierand basically repeated this test in orderto find out that the average efficiency wasbumped up around 2 to 4% with the active version,not bad.But of course next I wanted to replace allthe diodes to increase the efficiency evenmore.To do that I soldered the TEA2208 IC to abreakout board and afterwards to a perfboardto which I then added the 4 MOSFETs and somecapacitors pretty much like the typical applicationschematic recommended me to do.The result didn't look half bad but I wasstill very nervous while doing the first testwith lowered mains voltage.But as you can see on the oscilloscope thisactive rectifier also seems to work just fine,at least with resistive loads.Because while trying to charge up the capacitorbank for the power test, there appeared tobe some sort of short circuit problem withthe rectifier.Not sure if my design with the low cost highresistance MOSFETs is the problem or whetherthe topology and IC can generally not handlecapacitive loads because the datasheet alsostates that a boost type power factor circuitmust follow the application which more orless prevents current surges from capacitors.The circuit does however work just fine withlike I said restive loads.But due to obvious safety concerns I reallydidn't wanted to include it in the next mainsvoltage power supply test in which I basicallymeasure the efficiency of a common switchedmode power supply before and after implementingan active rectifier.The only thing that held me back once againwas a familiar sentence in the TEA2206 datasheetthat states that it is intended for applicationsfollowed by a PFC.And since such a power factor circuit gotmentioned twice now let me tell you that itbasically prevents that mains current onlygets drawn near the peak of the AC mains voltage.Instead it distributes the current draw evenlyacross the whole sinusoidal voltage, but moreabout that topic in another video.The only problem was that pretty much allof my power supplies didn't come with thisfeature except of course one that I need tocharge my newest laptop.And I decided to not sacrifice it for thisvideo which is why I pushed my luck and triedit with this a bit nicer power supply thatnot only comes with less sharp current surgesbut also some filters on its input.So after doing the usual power measurementtest with it, I desoldered its original fullbridge rectifier and simply replaced it withthe leads of the active rectifier board.And luckily nothing exploded after the powerup and everything worked perfectly fine sothat I could do all the measurements.Now the final results tell us that the activerectifier is once again more efficient butthis time only with a difference of around0.2 to a maximum of 0.9%.The reason is that due to the higher mainsvoltage level of 230V that gets transformeddown, there is only a small current flowingthrough the rectifier which does not createthat big of a power loss and thus is not thatimportant for the efficiency.But if we got a low voltage high current systemwithout transformation then a better rectifieris definitely recommended as we proved intest 1 of this video.So in conclusion the old school full bridgerectifier is definitely good enough for mostof the mains voltage rectification becauseit is cheap, rigid and efficient enough forthis task.With that being said I hope you learned somethingnew through this video and now understandthe advantages and disadvantages of activerectifiers.If so consider supporting me through Patreon.Don't forget to like,share, subscribe andhit the notification bell.Stay creative and I will see you next time.