Download "4# Устройство и принцип работы блоков питания ЖК ТВ. Зачем нужен PFC (ККМ)? Виды PFC."

"videoThumbnail 4# Устройство и принцип работы блоков питания ЖК ТВ. Зачем нужен PFC (ККМ)? Виды PFC.

#25. Транзисторы. Практика. Структура. Схемы включения. Режимы работы.

#25. Транзисторы. Практика. Структура. Схемы включения. Режимы работы.

Channel: HamRadio Tag

#10 Конденсатор. Практика. Параллельное включение в цепях питания.

#10 Конденсатор. Практика. Параллельное включение в цепях питания.

Channel: HamRadio Tag

Замена коннектора клавиатуры. Как это было 7 лет назад.

Замена коннектора клавиатуры. Как это было 7 лет назад.

Channel: HamRadio Tag

Ремонт ноутбука

ремонт видеокарты

ремонт компьютера

ремонт планшета

ремонт сотового

урок по пайке

ремонт электроники

пайка BGA

Прожарка

разгон

ремонт техники

обучение ремонту

сервисный центр

замена чипа

laptop

ремонт своими руками

00:00:02

videos dedicated to the power supply and

00:00:05

in this part we will analyze in detail

00:00:08

the principle of operation of power factor correctors,

00:00:13

the Russian abbreviation is KKM, the

00:00:16

English abbreviation is

00:00:19

fc, we will figure out what these blocks are needed for,

00:00:24

what happens if such a block diagram is

00:00:28

technically absent from the power supply in

00:00:31

which cases, a corrector is used and

00:00:34

why they are needed, what types they

00:00:37

are and, accordingly, what

00:00:40

advantages they bring and what disadvantages they have, it should be

00:00:44

noted that currently

00:00:49

most power supplies have power factor correctors if their

00:00:51

power exceeds about 50

00:00:55

watts, naturally in low-power units, such as for

00:00:58

example here in such units

00:01:01

whose power does not exceed 50 watts, as a rule, a

00:01:05

power factor corrector is not

00:01:07

installed

00:01:09

because this is an additional circuit

00:01:13

and, accordingly, firstly, the

00:01:15

dimensions of the entire device increase in

00:01:18

cost and sometimes it even becomes

00:01:22

economically inexpedient to run them

00:01:25

because the price of such a unit

00:01:29

will be significantly higher but in let's say well-

00:01:33

designed power supplies with a

00:01:34

power of 50 or more, take at least the

00:01:39

same power adapters for laptops, that is,

00:01:41

if it is an original adapter, then

00:01:45

as a rule such a corrector

00:01:46

is installed in it, despite the fact that this

00:01:49

leads to an increase in dimensions and an

00:01:52

increase in weight, but nevertheless such a

00:01:54

corrector is installed if, for example, the

00:01:56

power supply adapter is fake, then as a

00:01:59

rule

00:02:00

it saves on the corrector and it is

00:02:03

not in the circuit. What are the advantages of the

00:02:06

presence of such a corrector? I

00:02:08

will try to tell and explain in this

00:02:11

video and, accordingly, we will

00:02:13

analyze the circuit design of this block

00:02:16

because in In this unit

00:02:18

we also have a power factor corrector. If

00:02:22

we look a little into the past,

00:02:24

initially almost all power supplies

00:02:27

were built using a transformer circuit;

00:02:30

transformers have good efficiency; they do not

00:02:33

distort the signal shape in the supply network,

00:02:36

but they have very significant dimensions

00:02:40

and weight, so transformer

00:02:42

power supplies were gradually replaced switching

00:02:45

power supplies are of this type and in such

00:02:49

power supplies the input circuit, that is, the

00:02:52

input rectifier, is built according to a

00:02:55

standard, that is, classical circuit,

00:02:57

that is, we have a diode bridge at the input

00:03:00

and behind the diode bridge we

00:03:03

place a smoothing electrolytic

00:03:05

capacitor, that is, like in this

00:03:07

case we have an alternating voltage

00:03:08

supplied to the diode bridge from the output of the

00:03:11

diode bridge, a

00:03:12

pulsating voltage is supplied to a

00:03:14

smoothing capacitor where

00:03:17

it turns from pulsating to

00:03:19

constant in the same way, and here the diode

00:03:22

bridge voltage is directly

00:03:24

supplied to a

00:03:26

smoothing electrolytic

00:03:28

capacitor

00:03:29

when there were not very many such blocks,

00:03:32

then in principle they didn’t create any special problems,

00:03:35

but when the

00:03:37

lion’s share of power supplies became

00:03:39

pulsed and when the input

00:03:42

rectifier was built exactly according to this

00:03:44

circuit, that is, we have a diode bridge

00:03:45

from which the

00:03:47

pulsating voltage immediately goes

00:03:49

to the smoothing capacitor, and

00:03:53

problems began to appear, and the essence of the

00:03:55

problem is the fact that such a

00:03:58

rectifier with capacitive filtering

00:04:01

consumes current from the network not according to a

00:04:05

sinusoidal law, but in

00:04:07

current pulses, and such

00:04:10

AC rectifiers with capacitive filtering

00:04:12

can consume currents from the network, the

00:04:15

pulse value of which can be

00:04:18

several times higher than the

00:04:20

rated current of the entire power supply in In

00:04:23

general, this leads to the fact that the current from our

00:04:27

supply network

00:04:29

is consumed unevenly and in pulses, and

00:04:32

this leads to some problems

00:04:35

that we will not consider now,

00:04:38

so to make it more clear, let's

00:04:40

draw a few graphs from which

00:04:43

we will understand the essence of the problem itself. To begin with,

00:04:47

I will draw the rectifier itself based on

00:04:51

diode bridge and

00:04:53

electrolytic capacitor, we

00:04:56

have some voltage that we

00:04:59

apply to the power supply, let it be 220

00:05:01

volts with a variable frequency of 50 hertz and

00:05:05

we apply this voltage to the diode bridge from the

00:05:10

output of the diode bridge, we

00:05:13

remove the voltage and let us

00:05:16

parallel help from drawing graphs of

00:05:19

what we have where

00:05:21

this will be observed, respectively, plus the

00:05:24

diode bridge, this is the minus of this output on

00:05:27

how we apply alternating voltage,

00:05:29

I will now draw

00:05:31

one period of the sinusoidal voltage,

00:05:34

that is, the voltage that we

00:05:36

apply to the input of the diode bridge,

00:05:40

it will look like this, that

00:05:44

is, this is a regular sinusoid with a frequency of 50

00:05:47

hertz amplitude our value will be

00:05:50

equal to 300 10 volts,

00:05:54

then after the diode bridge we

00:05:59

no longer get a sinusoidal voltage, but a

00:06:02

rectified voltage, that is, these

00:06:05

will be the same half waves but they

00:06:08

will be of the same polarity and then

00:06:12

the graph will take us like this, that

00:06:17

is, this is the half wave as it was it

00:06:19

remains negative, it just

00:06:23

moves to the area of positive

00:06:25

values, we see that the

00:06:29

pulsation frequency has immediately increased, that is,

00:06:32

if the input voltage was 50

00:06:35

hertz, then the

00:06:36

pulsating voltage will already be

00:06:38

100 hertz, but the

00:06:41

pulse converter itself

00:06:45

cannot be powered with a pulsating voltage because that it is designed to work

00:06:48

with a

00:06:49

constant voltage, so a

00:06:53

smoothing electrolytic capacitor is connected to the output of the diode bridge,

00:06:58

respectively, in this way,

00:07:01

let’s assume that at this moment in time

00:07:03

we

00:07:04

have applied voltage to this circuit and thus

00:07:09

the capacitor will be charged to the amplitude

00:07:11

value, that is, to this value

00:07:13

it is we will have an amplitude of 310 volts and

00:07:18

at this moment in time on

00:07:20

the capacitor we will have a voltage

00:07:23

equal to 310 volts since for now we have nothing connected to

00:07:27

the rectifier,

00:07:28

that is, we just

00:07:31

charged the capacitor and its terminals seem to

00:07:35

hang in the air, so the voltage

00:07:37

on the capacitor will be constant and it

00:07:39

will persist until the next half

00:07:42

wave and will be exactly the same in subsequent

00:07:45

periods of time, but we connect a switching power supply to our

00:07:48

real capacitor,

00:07:52

which is essentially a load for

00:07:55

our rectifier, that is, we can

00:07:57

draw it in this way, let’s

00:08:01

assume we have a power supply,

00:08:04

which in general is a load for

00:08:07

our rectifier, if the power

00:08:10

consumed by the power supply is small, then

00:08:13

during this period of time when

00:08:16

our

00:08:17

mains voltage decreases, the

00:08:21

voltage at the output of our filter

00:08:23

will be maintained by the

00:08:25

capacitor itself, but if the power

00:08:30

consumed from such a rectifier will be

00:08:33

equal to a certain value, then during this

00:08:35

time that we have between half-waves from a

00:08:38

sine wave, the capacitor will have time to discharge

00:08:41

to a certain value, that is, it will be

00:08:44

linearly discharged around this point

00:08:46

and it will be discharged exactly

00:08:50

until the next

00:08:52

half-wave voltage is the next half-wave will

00:08:55

not exceed the discharge voltage of the

00:08:58

capacitor, as soon as the voltage of

00:09:00

the half-wave exceeds the voltage on the

00:09:04

capacitor, the capacitor begins

00:09:06

to recharge again at the amplitude

00:09:09

value and

00:09:11

this whole thing is repeated from half-wave to half-wave,

00:09:16

so we see from the graph

00:09:20

that our current consumption

00:09:23

will be concentrated in a very short

00:09:27

periods of time, the greater

00:09:30

the power consumed by such a

00:09:33

rectifier, the correspondingly faster

00:09:35

the capacitor will discharge, that is, the

00:09:38

voltage on it will drop more and

00:09:40

the longer this time will be during

00:09:43

which this capacitor will

00:09:46

again be charged to an amplitude

00:09:49

value of 310 volts, but they try

00:09:53

make sure that the ripples of this

00:09:56

voltage are as minimal as possible

00:09:58

because personal ripples

00:10:00

negatively affect the operation of the unit itself;

00:10:03

therefore, choose a

00:10:05

capacitor capacitance of a fairly large value in

00:10:07

actually working power supplies; the

00:10:09

voltage drop between half-waves is

00:10:12

not very large, and this tells us

00:10:15

that the time during which

00:10:18

the capacitor will be charged will be very

00:10:20

little, well, let's give it as an example, if we

00:10:23

took then

00:10:25

the capacitor will be charged

00:10:28

during this period of time and,

00:10:31

accordingly, this floor outside

00:10:34

during this

00:10:36

period of time the current pulses that

00:10:39

will be consumed from the network they will be

00:10:42

have a pronounced appearance of

00:10:45

peaks like this, that is, the current from the network will be

00:10:48

consumed in very short periods

00:10:50

of time, this interval is when the current

00:10:53

charges the capacitor, it determines the angle of

00:10:55

passage of the rectifier current, this angle

00:10:59

or it is also called the

00:11:01

load power factor depends on and the pedal with the

00:11:05

source itself, that is, on our

00:11:07

supply network, it also depends on the

00:11:09

size and capacitance of the filter

00:11:11

capacitor and on the size of the load, that

00:11:15

is, these values will affect the angle of

00:11:17

passage of the

00:11:19

rectifier current with a low load of the

00:11:21

power supply, the value of this angle can

00:11:24

be several degrees, if

00:11:26

the load is more powerful, then

00:11:29

this angle a can be about 20-30

00:11:33

degrees, but in any case it is much

00:11:36

less than the entire period and thus,

00:11:39

even with high currents in the load, our current

00:11:43

is not

00:11:44

continuous; it has the form of pulses of

00:11:47

relatively large amplitude and

00:11:50

contains many higher harmonics; this is a

00:11:54

simple circuit solution that is, a

00:11:56

diode bridge and a filtering

00:11:58

electrolytic capacitor, it

00:12:00

leads to the fact that the current from our network is

00:12:03

consumed in pulses, plus

00:12:06

this is aggravated by the fact that at the same time

00:12:10

we can have a very

00:12:13

large number of such

00:12:15

units connected to the network and they will all consume

00:12:19

current pulses in one and the same moment

00:12:20

in time, that is, in fact, all these

00:12:23

current pulses will be summed up

00:12:25

because they will occur in the

00:12:29

same period of time and in general

00:12:31

the situation will be even worse. Such pulsed

00:12:35

current consumption can lead to

00:12:38

heating of the wires, that is, losses in The

00:12:41

power line itself also

00:12:44

distorts the shape of the supply voltage,

00:12:48

which can lead to a skew false to the

00:12:52

appearance of some voltage on the

00:12:54

neutral wire, and this also leads

00:12:57

to cutting off the tops of our

00:12:59

sinusoidal voltage. Why does this

00:13:01

happen? Let's figure it out now, let's

00:13:04

assume that we have some kind of

00:13:07

step-down transformer and the

00:13:10

secondary output winding of this

00:13:13

transformer is, in general, the output of 220

00:13:16

volts of our

00:13:19

power line, but I’ll draw here one

00:13:22

winding, in fact, here there is a three-phase

00:13:24

power supply, but for forgiveness, I’ll just

00:13:27

draw that we have some kind of source

00:13:30

that produces an

00:13:33

alternating voltage of 220 volts with a frequency of

00:13:36

50 hertz,

00:13:38

respectively, and

00:13:39

we are this voltage due to the

00:13:44

power line, this is our

00:13:49

power line, we bring

00:13:53

their consumers to our consumer, in this

00:13:56

case, let us have

00:13:59

these power supplies that

00:14:02

lead to pulsed

00:14:04

current consumption in the network, let's

00:14:08

look at what can happen with this

00:14:11

supply voltage

00:14:12

if a lot of these from the power supplies are

00:14:15

turned on and they

00:14:17

consume pulse currents, the initial

00:14:19

voltage that we have at the output of

00:14:22

the transformer will have a

00:14:24

normal form, that is, this is a regular

00:14:28

sinusoid amplitude value, I

00:14:31

will have 310 volts effective 220 and

00:14:36

it will not be distorted, that is, this is

00:14:40

essentially our reference voltage, our

00:14:43

power line is not ideal and

00:14:46

in fact it is an ordinary

00:14:49

wire, an ordinary wire has some kind of

00:14:51

ohmic resistance, that is, we can

00:14:53

say that the line in front of the power transmission

00:14:58

has some kind of resistive resistance,

00:15:00

so I I’ll draw here two

00:15:03

resistors like this and what we will have in

00:15:07

the end, we already found out from the previous picture

00:15:09

that our current consumption

00:15:13

occurs in pulses like these, so

00:15:16

let’s take these pulses accordingly and

00:15:19

draw

00:15:21

this, we will have the current that

00:15:26

our power supplies consume

00:15:29

in the end due to the fact that we have an

00:15:32

impulse to consume current on these

00:15:35

resistors, essentially the voltage on our

00:15:38

power line will drop and

00:15:43

since here is essentially a resistive

00:15:46

load, the

00:15:47

shape of this voltage, that is, the drop in

00:15:50

this voltage will repeat the shape of

00:15:53

our sensible pulses, that is, Essentially, the

00:15:57

voltage drop on the

00:15:59

power line will

00:16:03

look like this, that is, we see that the

00:16:05

voltage drop is far from sinusoidal

00:16:09

and as a result, the resulting voltage

00:16:12

that will come to our power supply will

00:16:14

essentially be this reference voltage minus this

00:16:17

voltage, which

00:16:20

is voltage drop on the

00:16:23

power line and

00:16:25

but this is natural, everything is done on different scales,

00:16:28

but in the end we get that

00:16:32

the sinusoid will have such a smooth

00:16:35

top and will be, as it were, cut off, that is,

00:16:39

instead of a sinusoid we will get such that the

00:16:43

tops are cut off precisely due to the fact

00:16:46

that we are dealing with pulsed

00:16:49

current consumption described by current pulses that

00:16:52

cause strong distortions of the

00:16:55

mains voltage and

00:16:57

additional losses; at the same time, a

00:16:59

wide range of

00:17:02

harmonic components are also generated that can

00:17:04

create

00:17:06

problems for our equipment;

00:17:09

when interference occurs during the operation of a switching power supply,

00:17:11

which is associated

00:17:15

with high-frequency

00:17:17

switching, then we have this interference

00:17:20

are filtered by an output filter in the input

00:17:24

fe if we talked in detail in the

00:17:26

first part of our video, but the pulse

00:17:30

currents that we have when operating a

00:17:33

conventional rectification circuit

00:17:37

cannot be suppressed by such a filter because,

00:17:40

firstly, we have them at a fairly low frequency, and

00:17:44

secondly, all these currents are turn out to be

00:17:46

present throughout the entire

00:17:48

power line and essentially create

00:17:50

electromagnetic fields that

00:17:53

can quite strongly influence the inputs of

00:17:56

some sensitive amplifiers, that

00:17:59

is, the input of the amplifier is subject to interference

00:18:01

created precisely by the current pulses that

00:18:04

exist in our power lines

00:18:07

and

00:18:08

then this interference intensifies and introduces

00:18:11

distortion into

00:18:13

our useful signal, secondly, as I have already

00:18:17

shown, current pulses affect the

00:18:20

shape; essentially the peak of the sinusoid is cut off and

00:18:24

distortion occurs, it is the shape of the

00:18:26

supply voltage that

00:18:29

additional harmonics appear in the supply

00:18:31

voltage and this can affect the operation of

00:18:34

some circuits that are sensitive to the

00:18:37

shape of the input supply voltage, in

00:18:41

order to eliminate the pulse on

00:18:42

current consumption from the supply network and

00:18:46

the problems that cause it, a

00:18:50

special series of devices were created which are

00:18:52

called power factor correctors,

00:18:56

since the main reason for the low

00:18:59

power factor and the circulation of

00:19:02

high currents created by switching

00:19:04

power supplies is precisely the

00:19:07

pulsation of the input filter charge current

00:19:09

that to solve this problem,

00:19:12

additional elements are introduced that

00:19:14

increase the angle of passage of the

00:19:17

rectifier current, there are several

00:19:20

options for solving this problem, the

00:19:23

first option is the use of passive

00:19:26

or active power factor correction, the

00:19:28

second option is

00:19:31

passive or active filtering of

00:19:34

harmonics that appear in the

00:19:38

mains voltage, and the third option is

00:19:41

reduction requirements for the form of the

00:19:45

supply voltage itself, that is, in essence, this is the

00:19:48

adoption of the

00:19:50

voltage in the system, as a norm, the

00:19:54

most widely

00:19:55

used

00:19:57

schemes are passive or active high-

00:20:00

frequency correction. Now we will briefly

00:20:03

look at how passive correction works for us

00:20:06

and how active

00:20:09

correction works. Let's look in more detail

00:20:12

passive power factor correction

00:20:14

comes down to the use of

00:20:16

inductance in the input circuit, that is, the

00:20:19

so-called inductive filter.

00:20:22

If we again draw a diagram of our

00:20:26

power supply, here it is a diode bridge, the

00:20:29

input voltage that we supply to the

00:20:32

diode bridge and

00:20:34

if we

00:20:38

connect a filter capacitor to the diode bridge not

00:20:41

directly, but through a choke, then in essence, by doing

00:20:44

so, we

00:20:45

will carry out

00:20:47

passive power factor correction,

00:20:50

that is, in this way, our circuit

00:20:53

will take this form, if the

00:20:57

value of this inductance is

00:20:59

large enough, then this choke will supply

00:21:02

enough energy to maintain the

00:21:03

rectifier in a conducting state

00:21:07

practically in during the entire

00:21:09

half-cycle and reduces harmonic

00:21:12

distortion arising due to excess

00:21:14

current through you will accept in practice

00:21:17

passive power factor correction

00:21:20

reduces harmonic currents and significantly

00:21:23

increases the power factor, but such a

00:21:26

scheme does not solve the problem completely if

00:21:29

we draw the

00:21:30

same graph on which we draw the

00:21:35

sinusoidal voltage and also the

00:21:39

current consumed from the network, then if without

00:21:44

the use of a choke the current had a clearly

00:21:48

pronounced peak character, then with

00:21:50

the use of a choke these peaks

00:21:53

will seem to be more spread out, that is,

00:21:55

in fact, this is how we will flow somehow like this,

00:21:58

it will not repeat

00:22:00

completely sinusoidal shape, but the

00:22:02

period of current flow will be significantly

00:22:05

longer than without this inductor; such a

00:22:10

circuit provides lower

00:22:12

distortions compared to if this

00:22:15

inductor were not there at all, but it has a

00:22:18

higher reactive

00:22:21

power consumption at the network frequency, that is, in this

00:22:24

way there is a transition from the

00:22:26

power factor to the entire spectrum of

00:22:28

harmonics to the power factor at the

00:22:32

frequency of the fundamental harmonic, that is, at

00:22:34

our supply network frequency, a passive

00:22:38

corrector or inductor has

00:22:41

quite large dimensions and is appropriate in

00:22:44

low-power devices where

00:22:47

the price of the device is not critical and its

00:22:51

dimensions and weight are not important; the first sufficiently

00:22:53

powerful power supplies which began to

00:22:56

appear were just equipped with a passive

00:22:59

power factor corrector, that

00:23:01

is, we see this is a rather

00:23:03

massive choke that is just

00:23:05

included in the gap between the diode bridge

00:23:09

and the

00:23:10

smoothing electrolytic

00:23:12

capacitors.

00:23:13

Such a circuit naturally does not solve the

00:23:16

problem of pulsed current consumption one hundred percent,

00:23:19

but still it better than

00:23:22

without a choke at all,

00:23:25

now let's look at active

00:23:27

power factor correction with

00:23:29

active high-frequency power factor correction, the

00:23:33

load in such circuits behaves

00:23:36

like an active resistance, while

00:23:39

its power factor is close to unity

00:23:41

and the magnitude of the

00:23:43

generated harmonics is very small, let's

00:23:47

compare the shape of the input current with conventional

00:23:50

rectification and when using active

00:23:53

power factor correction, the

00:23:55

input voltage has a

00:23:57

sinusoidal form, that is, it is a regular

00:24:00

sinusoidal voltage with a frequency of 50

00:24:02

hertz and then we have

00:24:04

a diagram that illustrates the

00:24:06

current consumption from the supply network and

00:24:10

also

00:24:11

shows the voltage that we will have

00:24:13

on the smoothing electrolytic

00:24:16

capacitor,

00:24:17

that is like the picture that

00:24:20

I drew for you, we see that we have a

00:24:22

pulse for current consumption at this

00:24:25

moment in time, our capacitor

00:24:27

is recharged and then it is gradually

00:24:30

released to the load, then again there is a

00:24:34

pulse current consumption during

00:24:36

which the capacitor is charged and 5 until the

00:24:40

next half-cycle goes smooth

00:24:42

discharge with

00:24:45

active power factor correction; the

00:24:48

current consumed from the network is

00:24:51

no longer pulsed in nature; its shape

00:24:55

resembles a sinusoid, that is, the input current

00:24:57

when using active

00:25:00

power factor correction is in shape and phase

00:25:04

. coincides with the shape of the input voltage

00:25:07

and thus the top is consumed from the network

00:25:12

not in pulses but according to a sinusoidal

00:25:15

law and this does not cause any

00:25:18

distortions or surges in the supply network and the

00:25:21

output voltage will be very

00:25:24

close to constant when using

00:25:28

active power factor correctors,

00:25:30

pulsed ones are used the conversion

00:25:33

provides all the advantages of

00:25:36

pulse converters; it is

00:25:38

small in size and weight;

00:25:40

the circuit design of the highest-frequency

00:25:43

power factor collector can

00:25:45

be different; it can be a

00:25:48

step-up or step-down

00:25:51

converter; the

00:25:53

most widely used at the

00:25:55

moment is the so-called bus

00:25:57

converter, that is, these are step-up

00:26:00

converters and they allow to get the

00:26:06

face cosine value as close to unity as possible, which is what

00:26:08

such converters also achieve by

00:26:11

increasing the voltage on the electrolytic

00:26:15

capacitor, thereby reducing the current in the

00:26:18

high-voltage part, that is, the

00:26:21

heating of the primary winding of the transformer is reduced

00:26:24

and the static losses on the

00:26:28

switches in the high-voltage side are reduced, since

00:26:32

with increased voltage on the

00:26:34

capacitor, commutation will

00:26:37

occur with a higher voltage but a

00:26:40

lower current is accepted. The figure

00:26:42

shows a classic circuit of

00:26:44

power factor correctors.

00:26:46

Power factor correctors of this

00:26:48

type can be divided into two classes

00:26:51

depending on the operating mode of the

00:26:54

inductor, the first class is with intermittent

00:26:58

operation and the second class is with a

00:27:00

continuous mode of operation, the intermittent

00:27:03

mode of operation is mainly used in

00:27:05

circuits with a power of up to 300 watts due to the

00:27:08

presence of large currents that flow

00:27:11

through high-voltage switches in

00:27:14

power accent correctors, and this mode is good because

00:27:17

there are no losses on reverse

00:27:20

recovery of the buffer diode;

00:27:22

continuous mode is used in

00:27:24

circuits with with a power of up to several kilowatts, but

00:27:28

in this case, diodes with a

00:27:31

short recovery time should be used. When choosing a

00:27:35

transistor for operation in such circuits,

00:27:37

it is necessary to select instances that

00:27:40

are characterized by a short

00:27:42

switching time. Before we look at

00:27:45

the circuitry of the blocks themselves, let’s all

00:27:48

remember a little about the principle of constructing

00:27:50

boost converters here. In

00:27:52

the picture we have a

00:27:55

block diagram of a step-up

00:27:57

converter.

00:27:58

This type of converter

00:28:00

essentially refers to a reverse run

00:28:03

converter, that is, a

00:28:05

converter when the energy

00:28:07

stored in the inductor

00:28:09

is given to the load during the reverse

00:28:12

stroke, that is, when our key transistor is

00:28:14

closed, when our key opens, that

00:28:18

is 1 picture, the current through the

00:28:21

inductor increases linearly with the

00:28:26

diode, the rectifier diode is closed at

00:28:29

the moment when our switches open,

00:28:32

respectively, the voltage on the

00:28:34

inductor is summed up with the

00:28:37

supply voltage, and when it

00:28:40

exceeds the value of the

00:28:42

voltage on the capacitor, the diode

00:28:45

opens and the inductor

00:28:48

gives off its energy to the load and

00:28:51

in parallel charges the capacitor; the

00:28:54

voltage level at which the

00:28:56

diode is unlocked is called the

00:28:59

reverse voltage; on the reverse stroke, the coil

00:29:01

gives the stored energy to the load and to the

00:29:05

capacitor; at the same time, the current in the coil

00:29:08

decreases; then this cycle is repeated,

00:29:11

that is, the switch closes again

00:29:13

energy is accumulated the switches are opened

00:29:16

the energy is given to the load this is the

00:29:19

type of step-up

00:29:21

voltage converter that works

00:29:24

after we have looked at the principle of the

00:29:27

step-up converter let's

00:29:30

smoothly move on to the

00:29:33

power factor corrector circuit aka Pepsi the

00:29:36

input part remains

00:29:38

unchanged, that is, we have a diode at the input

00:29:41

bridge diagonal of the bridge we supply an

00:29:44

alternating voltage of 220 volts from the output of the

00:29:48

diode bridge, we get a

00:29:51

pulsating voltage, but then we do

00:29:54

not apply this pulsating voltage to the

00:29:56

capacitor, but to the step-up

00:29:59

converter, we remember that our step-up

00:30:02

converter consists of an

00:30:04

inductor, which

00:30:07

is essentially a choke as well from the

00:30:10

switching element I will draw that

00:30:12

here we have a field-effect transistor

00:30:16

diodes

00:30:18

connected in this way, that

00:30:22

is, in fact, we have the same

00:30:24

structure of a

00:30:25

conventional step-up converter and the

00:30:28

whole thing is loaded on v2 living

00:30:32

electrolytic capacitor

00:30:35

here directly, I will not connect yet

00:30:39

I’ll draw a rectangle like this, the

00:30:42

purpose of which we

00:30:45

’ll talk about a little later,

00:30:48

the main task we have is such that the

00:30:51

current consumed from the network is

00:30:54

not consumed pulsed, but the form of current consumption

00:30:58

is close to the voltage form,

00:31:01

in fact, if our input voltage is

00:31:04

sinusoidal, then the form the consumed

00:31:06

current from the network must also have a

00:31:09

sinusoidal form; in order to

00:31:12

ensure such current consumption, a

00:31:15

special node is needed that will

00:31:19

appropriately supply

00:31:21

pulses to our key transistor. I

00:31:25

will write that this is a

00:31:27

formation node and this

00:31:30

formation node must generate pulses

00:31:33

in accordance with some control

00:31:36

voltages. Let me remind you that and at the output of the

00:31:39

diode bridge itself we will have a

00:31:42

pulsating voltage, that is,

00:31:44

these are the semi-waves, their amplitude

00:31:47

will be 310 volts and in fact we need to

00:31:51

bring the current consumption to exactly the

00:31:55

same form, that

00:31:57

is, we should have one of the control voltages

00:32:00

for the formation unit

00:32:03

rectified voltage, but directly,

00:32:06

naturally, 310 volts should not be supplied here,

00:32:09

therefore, as a rule, they simply install a

00:32:13

voltage divider that,

00:32:16

accordingly,

00:32:17

reduces the amplitude of the voltage, but

00:32:20

the shape of the voltage itself remains the

00:32:24

same, that is, from the point of division of

00:32:28

this divider, the signal is sent to the

00:32:32

formation node is one of the

00:32:34

control signals and the voltage here

00:32:37

will have this form; in

00:32:40

amplitude it will be less than 310, but in

00:32:43

shape it will be exactly the same as the

00:32:45

rectified voltage at this point, that

00:32:48

is, it will be a pulsating voltage,

00:32:52

which means we are tied to the shape of the input

00:32:57

voltage that is, we

00:33:01

already have one condition and 2 conditions we need to

00:33:04

monitor the current consumed from

00:33:07

the network, respectively, we will track the

00:33:10

current consumed from the network due to

00:33:13

this element, which we essentially have as a

00:33:16

current sensor, that is, the current flowing

00:33:20

through the inductance will pass

00:33:22

through the sensor current and thus

00:33:25

monitored by the formation node itself,

00:33:28

that is, these are the two main

00:33:31

signals that are necessary in order to

00:33:34

implement the Pepsi circuit; the first

00:33:37

signal is generated from the input

00:33:40

rectified voltage; the second signal is

00:33:42

generated from the current sensor if we

00:33:46

draw a

00:33:49

larger graph of such a stretched

00:33:53

half-wave we will have a half-wave,

00:33:58

essentially one of the half-waves of the rectified

00:34:01

voltage,

00:34:03

then we need to form

00:34:06

pulses on the watering gate in such a

00:34:09

way that when our transistor

00:34:12

opens, that is, the opening

00:34:14

voltage level appears through the

00:34:17

inductor, we will have a current flow,

00:34:19

accordingly this current will be perceived by us

00:34:22

current sensor and when the

00:34:24

instantaneous value of the current sensor is

00:34:26

equal in level to the level of the

00:34:29

rectified voltage after the divider,

00:34:32

then the switch should close, that is, in

00:34:35

this way the

00:34:36

circuit will work for us, for example, we have a

00:34:39

transistor open, the current through the

00:34:41

coil

00:34:43

increases when we have a current with the current sensor

00:34:48

will be equal to the level of the rectified

00:34:52

voltage, our transistor must

00:34:54

close, the result will decrease

00:34:57

when a zero current value comes from the current sensor,

00:35:01

that is, when the current in

00:35:04

the coil is equal to zero,

00:35:06

the transistor must open again, the current

00:35:09

will again gradually increase again

00:35:13

when the intersection with

00:35:15

envelope of the rectified voltage, our

00:35:19

transistor must close, the current through

00:35:21

the coil will again gradually decrease and

00:35:25

this will be constantly repeated

00:35:28

a large number of times throughout

00:35:32

this entire period,

00:35:35

the voltage as soon as the instantaneous

00:35:38

value from the current sensor is

00:35:39

compared with the

00:35:41

rectified voltage,

00:35:43

our transistor closes as only the

00:35:46

current value has reached zero,

00:35:50

our transistor opens, this

00:35:52

corresponds to operation in the

00:35:54

power factor corrector in intermittent

00:35:57

mode, that is, our current drops to zero

00:36:00

and in the same way the whole thing will be

00:36:03

repeated for us and thus

00:36:07

the voltage that needs to be

00:36:09

applied to the gate this transistor,

00:36:13

that is, at this moment in time, our key

00:36:16

opens as soon as the current has reached

00:36:19

its maximum,

00:36:21

our key has closed, that is, we have the

00:36:23

first pulse, this is the

00:36:26

next moment in time,

00:36:28

our key opens again, it will close, and

00:36:32

accordingly, at peak 2, the pulse

00:36:35

will be this 3rd pulse

00:36:38

will be a little wider and thus

00:36:44

we build for the

00:36:46

remaining

00:36:49

pulses this is the

00:36:54

kind of pulse we

00:36:56

get that fits into one

00:36:59

half-cycle, naturally the

00:37:01

switching frequency of this transistor

00:37:03

will be much higher than in the figure, this is

00:37:06

just to

00:37:07

illustrate, that is, the moment when

00:37:10

here we have the beginning of a sinusoid, our

00:37:13

key will open for a very

00:37:16

short period of time, and as

00:37:18

soon as we approach the peak of this

00:37:22

half-wave, our key will be open for the

00:37:24

maximum time, precisely according to this

00:37:28

law, and pulses should be generated in

00:37:31

this converter, but if we

00:37:34

carefully let's see, in this form

00:37:37

we do not have stabilization of the output

00:37:39

voltage; in order for us to have

00:37:42

stabilization of the output voltage, an

00:37:44

additional divider is introduced;

00:37:47

this divider is connected

00:37:50

directly to our output

00:37:53

voltage, that is, essentially to a

00:37:55

capacitor, and the

00:37:57

signal from this voltage divider

00:38:02

must be compared with

00:38:04

some reference voltage,

00:38:08

this is the so-called comparison device;

00:38:12

essentially, this comparison device

00:38:15

is an operational

00:38:17

amplifier that generates an

00:38:20

error signal, and

00:38:22

this error signal should

00:38:25

also influence the

00:38:28

shape of the voltage that our

00:38:32

generation device generates; this signal

00:38:35

that comes from the

00:38:37

rectifier does not go directly to the

00:38:41

formation device is fed to the

00:38:46

voltage multiplier, here these two signals

00:38:50

are multiplied and the resulting

00:38:52

signal is sent to the

00:38:56

formation device, so the

00:39:00

pulse width is affected not only by the

00:39:03

input

00:39:05

rectified voltage, but also by the

00:39:08

output voltage, depending on

00:39:11

what load

00:39:13

the voltage will be connected here on this, the dividers

00:39:16

will also change and our

00:39:18

error signal will change, and the error signal, in

00:39:22

turn, will influence the

00:39:25

generation device itself

00:39:27

precisely according to this principle,

00:39:28

and

00:39:29

it hangs around, firstly, the

00:39:32

consumed input current changes

00:39:35

to almost a sinusoidal form, and

00:39:38

secondly, we have stabilization of the

00:39:41

output voltage on the capacitor

00:39:44

feedback on the output voltage in

00:39:48

this case is negative

00:39:51

therefore increasing the output voltage

00:39:54

at the output of this circuit will lead to a

00:39:58

decrease in the error signal if the output

00:40:01

voltage increases then the error signal

00:40:04

decreases and therefore the

00:40:07

value at the output decreases multiply ilya as

00:40:10

a result of this the pulse width of the

00:40:13

color key arriving at the gate

00:40:16

will decrease and, accordingly, the

00:40:19

average value of the current

00:40:21

through the inductance will decrease, which in turn

00:40:24

will lead to a decrease in voltage, that is,

00:40:27

in essence, this is how stabilization will work in the

00:40:29

opposite case, when the

00:40:32

output voltage decreases, the

00:40:34

opposite processes occur and as

00:40:37

a result of this

00:40:39

our error signal will increase

00:40:42

and the pulse width will increase,

00:40:45

which will lead to an increase in the current through

00:40:48

the coil and, accordingly, to an increase in the

00:40:51

voltage value on the capacitor.

00:40:54

This is the way to ensure

00:40:57

stabilization of the output voltage in the

00:40:59

power factor corrector circuit

00:41:02

both when the voltage in the network changes

00:41:05

and when the load changes.

00:41:07

we have it connected to the output of this

00:41:11

converter, since these

00:41:14

converters operate at a fairly

00:41:16

high frequency, which is usually tens of

00:41:19

kilohertz, then, accordingly, a

00:41:22

huge number of

00:41:25

such switching pulses fit into one half-period; the

00:41:28

average current will have this

00:41:31

form, that is, it will not in the form of such

00:41:35

peaks, and due to the very fast

00:41:38

switching of our switch, the average current

00:41:41

will be almost

00:41:43

sinusoidal, that is, it

00:41:46

will practically coincide in shape and phase with the

00:41:49

rectified voltage, which means

00:41:52

that the current consumed from the network will be

00:41:56

identical in shape and phase with the

00:41:59

network voltage, which is what we need in general it is

00:42:02

necessary

Description:

Набор в группу обучения основам электроники и ремонта. https://vk.com/hamradio1986 Стоимость обучения 1500 руб

Preparing download options

Popular

HD video

Only sound

All

* — If the video is playing in a new tab, go to it, then right-click on the video and select "Save video as..."

** — Link intended for online playback in specialized players

Questions about downloading video

How can I download "4# Устройство и принцип работы блоков питания ЖК ТВ. Зачем нужен PFC (ККМ)? Виды PFC." video?

http://unidownloader.com/ website is the best way to download a video or a separate audio track if you want to do without installing programs and extensions.
The UDL Helper extension is a convenient button that is seamlessly integrated into YouTube, Instagram and OK.ru sites for fast content download.
UDL Client program (for Windows) is the most powerful solution that supports more than 900 websites, social networks and video hosting sites, as well as any video quality that is available in the source.
UDL Lite is a really convenient way to access a website from your mobile device. With its help, you can easily download videos directly to your smartphone.

Which format of "4# Устройство и принцип работы блоков питания ЖК ТВ. Зачем нужен PFC (ККМ)? Виды PFC." video should I choose?

The best quality formats are FullHD (1080p), 2K (1440p), 4K (2160p) and 8K (4320p). The higher the resolution of your screen, the higher the video quality should be. However, there are other factors to consider: download speed, amount of free space, and device performance during playback.

Why does my computer freeze when loading a "4# Устройство и принцип работы блоков питания ЖК ТВ. Зачем нужен PFC (ККМ)? Виды PFC." video?

The browser/computer should not freeze completely! If this happens, please report it with a link to the video. Sometimes videos cannot be downloaded directly in a suitable format, so we have added the ability to convert the file to the desired format. In some cases, this process may actively use computer resources.

How can I download "4# Устройство и принцип работы блоков питания ЖК ТВ. Зачем нужен PFC (ККМ)? Виды PFC." video to my phone?

You can download a video to your smartphone using the website or the PWA application UDL Lite. It is also possible to send a download link via QR code using the UDL Helper extension.

How can I download an audio track (music) to MP3 "4# Устройство и принцип работы блоков питания ЖК ТВ. Зачем нужен PFC (ККМ)? Виды PFC."?

The most convenient way is to use the UDL Client program, which supports converting video to MP3 format. In some cases, MP3 can also be downloaded through the UDL Helper extension.

How can I save a frame from a video "4# Устройство и принцип работы блоков питания ЖК ТВ. Зачем нужен PFC (ККМ)? Виды PFC."?

This feature is available in the UDL Helper extension. Make sure that "Show the video snapshot button" is checked in the settings. A camera icon should appear in the lower right corner of the player to the left of the "Settings" icon. When you click on it, the current frame from the video will be saved to your computer in JPEG format.

What's the price of all this stuff?

It costs nothing. Our services are absolutely free for all users. There are no PRO subscriptions, no restrictions on the number or maximum length of downloaded videos.