Hi guys! How are you? Here Edgar welcomes you all once again from YoReparo, welcome to a new video
thank you so much for joining us this morning, or I don't know what time you are watching this video
but we're uploading it early
well, we've reached the lesson #43
I guess, let me see if I'm right... it is, lesson #43
there are a few more lessons to go before we can finish this basic course
actually, I'm really glad that you're enjoying these videos, that you're learning with them
remember, this is a basic course for everyone who just started on this
so you can create bases
that you'll need once we get to repair these wretches
and in that way you will have the basic knowledge and can understand the theory about diagnostic lessons easily
so, for me, a pleasure that I can help you
and today we'll talk about Boost, on next lessons we'll talk about Buck
LDO and that stuff that we've heard before but we don't know what are they
believe me i used to get confused, even today i get confused sometimes, because they are really extensive topics
but we'll try to explain this to you the most easily way, so you can understand it and you can repair phones
so, we'll talk about the Boost circuit
in short, the Boost is a voltage booster
for example, it grabs a voltage, for example VCC_MAIN or VDD_MAIN, that
you should already know who are these because we already saw them on previous lessons
it grabs that voltage, about 3.8 or 4 volts
and it will boost it into another voltage, that's what it does
with the help of some circuit that's controlling the switching
it does this with the help of a coil, that's recharging, a diode that doesn't allow power to pass to the other side
a storage capacitor that's charging with that energy and when it discharges it pulls the voltage we want
the Boost, in theory what we'll draw here is the Boost circuit
the easiest way there is
so we can draw a Boost, first we need a battery
a battery, so let's say this battery has a voltage of 3.8 volts, this battery goes to
this coil over here
depending on the capacity of the coil, the capacity of the capacitor and all that
that's how it will boost the voltage
the engineers already did this, they put the circuits that we need, this is just to explain the concept
remember, we are in the basic course, we do not go to the extreme with the information, only the basics
ok then, it goes to this coil
here it has a diode, and here it has a capacitor
a parallel capacitor
to ground, and here let's imagine
in this case, we will make the Boost of what gives light to the screen
for those who don't know, the iPhone screen, for example of the iPhone 6
operates at about 16 volts
How do I get 16 volts if my battery has 3.8 volts?
those LEDs that you see that turn on
the screen, the ones that illuminate the display, works with 16 volts, but we have a 3.8 volt battery
here's when the Boost enters
So, let's imagine here I have a LED
this is a LED and it works with 16 volts, ok?
and we close the circuit, this over here is in parallel
now, here we'll put a switch
a switch
so, when this is off
here I have 3.8 volts
the voltage will flow over the coil, because it is a coiled wire
here I'll have 3.8 volts
passes through the diode, and here on the capacitor I'll have
3.8 volts, and on the positive side of the LED I'll have 3.8 volts
3.8 volts, and the voltage flows here and keeps powering
this is in "Off"
this is what it looks like without working, without the switch on
this switch will be used by a controller
it will be controlled by a circuit that will be sending pulses
by the pulses, it will be sending a voltage, and that's what will activate the switch
thousands and thousands of times per second, that's really fast
So, what's going on here?
This switch will open and close many times, causing a short in the coil
the coil will be charging everytime the switch closes, the coil recharges
and discharges, recharges and discharges and so
what it does is, it allows the current flow, when this closes, takes a spin through the coil
it charges, and when it's open it discharges
and everything is stored on this capacitor
we'll make it again so we don't get confused
Imagine this circuit is open, the switch is open
the current flows from here, passes through the coil, when this gets closed
what comes from here, this will charge the coil, once this is opened
when this switch is open, the coil discharges
and recharges this capacitor
remember, this parallel capacitor is charged by the battery discharge
and this is charging and discharging, charging and discharging
that switch is there pulsing thousands and thousands of times per second
what it does is, it charges the capacitor, it sends a voltage to the other side, and once I get here
16 volts, then the IC
the one responsible for the pulse
so, this is says "Here are the 16 volts, so that's where it stays"
In simple terms, this is what the Boost is
it is a voltage booster
Ok, it took
3.8 volts with the help of one circuit, one switch, one coil, one diode and one capacitor
it took the 3.8 volts and increased them to 16 volts
Now, let's go to the board on the schematic, I'll show you what a Boost looks like
Well, actually it's not precisely the Boost like that, but we'll see all the circuits that I mentioned
because we're looking at the backlight of the iPhone 6, so take a look
here we have our beloved Boost
or DC-DC converter Step-Up
Okay? because it will go up, Buck is Step Down, because it will go down, we'll get into that later
So, take a look what do I have here
this is the backlight circuit from iPhone 6, it is a very easy circuit to interpret
on this circuit, enters a voltage of 3.8 volts
because, this line is called VCC_MAIN, 3.8 volts, ok?
voltage flows here and will help power this circuit
but it also power a coil over here, passes here, passes through the diode
if this wants to go back, it can't
back to the drawing, why do they put a diode here and preferably a Schottky diode?
Why do they put it there? Let's go back to the drawing and imagine this is a Schottky diode
because, when it closes, a short-circuit occurs
this goes to ground, so the current over here says
"Let's go over there" and the current wants to flow that way, but here they find the diode barrier
that doesn't allow the accumulated current on the capacitor turns back and go to ground
So, they put a Schottky diode there, because that diode blocks the path really fast, so that
which allows that when it discharges it can pass, but when it closes and the current comes back
it blocks it
and it will open and close very fast
so, back to the schematic
then here we have
the capacitors, in this case on iPhone 6 we have 3 of them
hese capacitors are storing the energy discharged by the coil
then passes and generate a line called PP_LCM_BL_ANODE
this line means Power Positive
LCM means Liquid Crystal Module
in this case it would be liquid crystal screen
BL means Backlight and Anode, why anode?
Remember what LED strips have are diodes
they're LED diodes
So, a LED diode, what does it have? A pad called Anode
and another pad called Cathode
so this means
what comes from here, will power the Anode pad
ok, just like that
so, this is what is being discharged here
will power the Anode pad
in the schematic we have it exactly here, this goes to the display connector
and back there are the cathodes these are negatives, they are like a feedback of the current
it is turning back the negative, we can leave it to ground and is exactly the same
but, inside this circuit, inside of all of this, we have a line called SW
what this line does is, the function of this switch
this is the line in charge of switching the coil
so, if I do the lines
this has a voltage
powers the circuit
powers the circuit, powers the coil, passes
passes through the diode
charges the capacitors
here it goes to the line called OVP, is a protection against voltage
if there's something on this line, it protects itself and blocks the power supplier
and here it generate it
So here this circuit will control the coil and electrocute it
let's say that, internally, this goes like this
this goes like this, here it comes to ground, and this goes like this, and there we have the switch
so, what happens with this? This is the switch
this will be getting closed
thousands of times per second
this will charge and discharge the coil
this will charge the storage capacitors, and once the 16 volts have been stored, they will be send
so I can have light on my screen, this is something that happens super fast
super fast
So, this is a Boost, this is the Backlight driver, okay? A Boost
Now, we'll see on the board so you can see it and
you can know how it is from this, to the schematic, to the actual motherboard
so, it is very important that you know how does it work, because... it's pretty
it's pretty to know how does it works
now, if we go to this Circuit Emulator
imagine these are the lights of the screen
here I have my coil, Schottky diode, storage capacitor, and here's the switch
this will be pressing really fast
If I turn it on, how many do I have? 4 volts
but, see what happens if I turn it on
here it is turned on and look at the graph above, it already has 8 volts
and what's going on here?
the more voltage you have, the brighter the lights will be, here we have 11 volts.
and all of this is thanks to the pulsing that's charging the coil
it discharges and charges the capacitor
and sends the voltage to the LEDs
is the same
first is the drawing of the circuit, it would be this
then we go to the schematic, it would be exactly this, everything explained so you can understand
In a nutshell, Boost is a voltage booster
grabs a flowing current and it will raise it
Now, let's go to the motherboard so you know what we have seen before
so, in the microscope we will see
i'll grab the tweezers
and let's see, here we have this coil, in this case I've destroyed it
here I have a diode
the diode, here I have the circuit, but it has resin, that's why we can't see it clearly
and here are the 3 capacitors
this goes to this filter, and from the filter to the connector
Now, if we go to the ZXW
look, here we have the coil, the coil is being powered by who?
By VCC_MAIN, here it says it below, VCC_MAIN powers the coil
I'll remove these so you can see it better
so you can see it better, here the coil is charged, as we seen here
VCC_MAIN came
charged the circuit
and powered the coil
okay? Now if we go here
look what is going to happen
we are on VCC_MAIN
it powered the circuit and the coil
now what happens? Passes through the coil
and now this is called PP_WLED_LX, LX in this case is
the same line over here
this line over here PP_WLED_LX
so first, this powered here, passed here
and is the same line
then passes the diode, what do we have on the other side of the diode?
it goes to 3 capacitors
if we go to the schematic
it powered here, powered the circuit, powered the coil, passed here, passed through the diode
and here are the 3 capacitors, and generated a line called Anode
this line called Anode was generated here, and reached this filter
and from the filter reached the display connector
just like that
So this is Boost
a voltage booster, I've tried to explain it in the best way possible
in theory, the essence of it is this circuit that we saw before, it got too messed up but
I can't clean it... so
that would be everything for today's lesson, guys!
I hope that you've learned something, comment below what do you think
if you learned what a Boost is
we'll see it a lot in Apple devices, in places where we need to increase the voltage
So, always a pleasure
oh by the way, I want to remember you that our books are already on our page
go to out page yoreparoacademy
click on the menu
go to the section "YoRecomiendo", go to downloads and at the bottom, there are the books
so, download them, read them and let's keep learning
Take care, a hug for everyone and we'll see you on the next time. Bye!