IE#44: How USB car charger works?

hello girls welcome to insula phonics so in today’s episode let’s take a look at how a car charger works now this was a very popular item back in the days when cars only have 12 volts accessory circuits and phones are usually Nokia that cannot be charged using USB charger but things are changing nowadays almost all brand new cars come with a built in USB charger but still people are using these kind of external charges for a lot of other purpose now chances are you still have one of these in your car but you don’t know how this thing works don’t worry in this video I will show you how exactly this thing works and I will grow a schematics of a tower completely reverse engineer this thing so speaking of which this particular challenge as you can see it’s made by a company called Jabra and they actually make a lot of Bluetooth audio accessories for now they don’t make a lot of these charges at all but they do have a very similar and I think it probably a very updated model of this USB charger by the way this particular model is discontinued and it is esz zero zero two and it is capable of up to 750 milliamp output current which clearly mentions that this thing is really old nowadays almost all smartphones users at least one amps of current for its proper operation for this proper charge and this can operate this entire thing can operate on both 12 volts and 24 volts DC and here that’s pretty much it it’s made by Jabra and to open it it’s really simple you just have to underscore unscrew this top portion right here and underneath here you will find a fuse that is a good thing and and the spring and there is a spring underneath on which the fuse is sitting so that is what creates this smooth kind of action with that that action is possible because of the fuse and let’s see what right thing this fuse has if I can focus on it it is it is 2 amps 250 volts use or two amps fuse for device is pretty fine no problem and to take it this thing further apart you have to take this metal ring that is just used to hold the entire thing where there is no screws or anything as you can see it’s it is already starting to come apart but using just some little folds you can take the entire thing off and inside it you can see pretty much very clearly that it has a very minimalistic components and as you can see this this is a spring and to which the fuse is connected and by the way these are not any way connected to get together oops there it goes and these two metal things are used for the negative contacts and this is also what keeps that this entire thing inside your child because it has this springy action it actually friction locks to the 12 volt socket so it does not fall apart very easily so it’s it’s have a multiple uses and also lets keep its you can see that only one of the two metal plates are actually connected to the ground the rest is just for the holding this thing down now let’s actually take the circular part okay that’s really simple because you know it’s just after all entire mobile USB charges like this one including this one is a buck converter you know there are you can actually make one by yourself with very low components but it the efficiency will be a matter because you know when you are actually making one you have to do a lot of calculations to get the maximum output from it maximum efficiency from it if you only care about the output and just ignore the efficiency you can make one release Li but let’s talk about this one and this one uses very common I see the mc34063 a this IC is actually really common for buck converters and because this IC is a multi-purpose as estrogen it’s not just a buck I see this is actually this IC can be used for buck and boost operation or even can be used for buck boost operation so it is a

multi it’s a versatile I see that peak and in here it is used it is wired as in a buck configuration but it can easily be rig rewired to form a boost converters which is you know really matter of only rearranging some of the components the entire other things will work and you cannot actually find the output voltage that’s only sure that’s going to be here so let’s take a look D at the bottom side there is no assembly components involved you can see the IC mc34063 a has two capacitors this one is probably across the positive terminal and okay let me actually reverse engineer this thing and I’ll be back once I reverse engineer this entire thing so okay guys I know how completely reverse engineered this Jabra USB charger and this is the result as you can see from the Psalter that it uses very simple components and it is really it was really easy to reverse engineer and all this does is really simple before moving on to the operation let me show you the data sheet which are on the flash off let me turn to show the IC here itself this is the IC that they’re using this is the 1.5 amps step up down inverting the switching regulator and this is the 4 0 6 3 I see that we are having right here and these are the features of this IC I’m not going to show you the entire thing if you want to read it you can pause this thing and this is the pin out for this okay and let me tell you that after downloading this datasheet I found that this circle right here is the is an exact replica of what you can find right here this is this check down configuration winding as per the datasheet and this is what exactly this circuit really is in fact all matters is just some component values are different that is the only thing that is changed here so let me tell you how this thing works even before that let me tell you how a buck converter in common works so let’s say you want to reduce the input voltage here in my case let me zoom down a little bit in my case let me show you that let me say you need to convert your steady 12 volts missing one yeah your steady 12 volts like that that’s the 12 volt you can now directly plug these 12 volts in to your form because your phone needs a much lower touch which is 5 volts for its operation and there are a couple of ways you can actually reduce the input voltage a simple method is by using a resistor dropper in series just like connecting a 12-volt battery to a resistor and then connect your phone to the other side low-voltage but the problem here is that you are wasting a lot of energy across the resistor as heat you know resistor can get really hot and you’re actually wasting a lot of energy and this thing is not a safe at all you are not you cannot guarantee that this thing works this is a really simplistic way it this can be achieved instead what we are actually doing is we are actually chopping down the steady DC volts that is right here we are actually chopping it down by chopping I mean we are actually pulse with more relating the steady state DC and because of that means take another and you can see the I was trying to throw this thing let me tell you that this this was the 12 volts state okay now let me tell you that this is for a one-minute of time okay so we are giving 12 volts at for a one minute time and it stays for 12 minutes so like one minute and now what I’m going to do is I’m going to chop this 12 volts at 50% duty cycle that means a 12 volt is divided into a lot of different pieces like this it resembles a square wave and this was also for one minute now even though the voltage of each individual square wave is 12 volts the entire

device was owned for half of the time let’s say you know this you can actually see that this is on this is off this is on this is off what that means is a device is on for say 30 seconds and device is off for the rest of 30 seconds so that is how this thing works because in a one minute operation time in the normal one weight operation time you are getting the full 12 volts continuously for one made but in this case we are getting the 12 volts only for 30 seconds not continuously but intermittently and for the remaining 30 seconds your device is off you know and because of that your device the power consumption the average power that your device receives will be low so by adjusting the duty cycle by duty cycle it means the own time the this is the own time we will say it’s as T on and this is the off time T off so the duty cycle means adjusting the duty cycle means adjusting the own time so higher duty cycle means a high on time and lower off time and a loaded signal means a high off time and lower so by adjusting the duty cycle you can get the record power you want so that is the easiest way to reduce the output voltage so by using some sort of mechanism to achieve this PWM chopping you can then control the amount of voltage that you can get at the output by suitably adjusting the power I mean the duty cycle so once that is achieved you need a set of other components you cannot just directly feed it square wave like this one to whatever load you are attaching you need some other components and that is where this extra components come to play and in this case this is the entirely you know simplest this is the simplest of all circle diagram for a buck converter in fact this entire circuit is only this thing and the entire operation happening here can be divided into three this here is happening at this point over here and this over here is what remain what is remaining over here so what happens is that this I see this MC 3 4 0 as switching thing that actually converts this stable 12 volts into a lot of you know square wave all just like that so that is the purpose of this M for MC 3 4 0 is e and that is why I am drawn it like that so it own and it makes this on and on and off kind of action so what happens is that that whole world gets on what it is Carly and because the inductor and capacitor is what smooths the square wave and forms a somewhat yeah if I draw it will be like kind of like that so it smoothes out it’s like you know filtering capacitor at the end of a rectifier so this diode is here is a freewheeling diode that is used to prevent the back EMF you know when the switch is open the in charge that is tolling the inductor will be huge and it needs somewhere to go otherwise it will damage the entire I see so once the switch is off the entire charge that is told in this inductor will flow through this diode so that it can operate in a stable manner and when the switch is closed the power can directly go from this side to through the inductor through the diode to the output so that is the basic operation and this is exactly happening at this point the input here let me show you that the input here is going through our point 1 ohms resistor that is that one over there so it it is used as I think that is used using as endure limiting resistor and then it comes to this hundred micro farad filtering capacitors capacitor and then it goes through a point three ohms resistor to the IC and these are pin number one seven and eight and the pin number one and the number

one is a collector they endure is an internal transistor inside let me show you that over here real quick so this is how the entire thing works here you know the pin number one is connected to this transistor which is then switched to the ground so your VCC is going through here going through here which is can turn on and off using this transistor and that’s how everything works so after that there is the four hundred and seventy Pico farad capacitor which is used to adjust the frequency of operation for this internal also later over here you can see the oscillator is connected to these friends in this capacitor and after that the output from this is going straight output is coming from pin 2 and goes straight to the circuit that we just see over here and this diode here is a 1 + 5 8 1 9 which is a fast recovery time Schottky diode one AM capacity and that diode is this one over here the inductor is predict standard value it is a 220 micro farad as per the datasheet and that is over here this one this output capacitor is that one over here this diode is just for the protection you know an additional protection for the output device and pin number 5 is actually a reference value because that adjust the switching frequency if you look closely turn off the light you can see they’re actually using two resistors oops is it let me find it real quick I know this video is getting really boring but still I love detecting anyways okay okay I got it there it is you can see these two resistors over here the R 2 and R 1 that is the resistors these two resistors are that one and those two are that and that’s pretty much it you can actually see that is used to that is used as the comparative comparing points so that it can adjust the switching frequency based on the voltage that is receiving at this point so yeah basically that’s it okay so now you know how we call charger works if you have any doubts and regarding anything that I said here I know I made a few mistakes by it because this is micro Henry no micro farad and there are some minor mistakes that I made so again if you have any doubts regarding any of this thing that I said that I mentioned like how this thing works or anything if you have any doubts please ask me in the comments below or I can you can mail me and right now since we are since I show you how it works I’m going to test it for you and since I don’t have a car battery you know the accessory socket I’m going to use what I’m have here in my lab it’s a 12-volt such whole world 1.5 1.5 amps for something I don’t know and I used mune to use a converter like that to attach it for it so hope T so let’s test this under load and see how this thing performs and I’m hoping that the green is the positive the green goes in inside that now there is no fuse connected in series with this thing so if anything blows up it blows up you can see that happening live if anything happens so I’m going to attach that today maybe I can connect that later for now and go to need the USB tester about four bits you can watch the video like it clicking the link that will come now at the top I so now I have turned on the power I’m going to attach the white to the ground and there it goes it booted and you can see the voltage is 5.38 now let’s test it by using a USB tester I’m going to attach that to here and it is now set to one amps of current and going to turn this thing on without shorting

anything is possible yep even though it is rated for 750 milliamps it is drawing 1 amps but you know a little bit of voltage drop is there it’s 4.5 volts it’s acceptable but thing is that it can handle one amps let me check in inductor real quick yep the ice is getting hot I think it is not going to solve all that let me see if we can survive the two M’s I’m going to switch it to two air modes and nope there goes just on two amps it doesn’t even stand a chance can barely see if I turn the light off we can barely see that the voltage is dropping to around three volts if I can show you that again no it even booted but I see it 1 amps of current the ice is getting really hot it’s oh it is really hot I cannot touch that but anyways the fact is that it works everything works fine so yeah if you have any doubts regarding anything that I said here just ask me in the comments below so that’s it that’s it that’s about how your car charger works thanks for watching see you in another video