Some time ago I already published a review where I showed how to make a PWM stabilizer using KREN5. Then I mentioned one of the most common and probably the cheapest DC-DC converter controllers. Microcircuit MC34063.
Today I will try to complement the previous review.
In general, this microcircuit can be considered outdated, but nevertheless it enjoys well-deserved popularity. Mainly due to the low price. I still use them sometimes in my various crafts.
That’s actually why I decided to buy myself a hundred of these little things. They cost me 4 dollars, now from the same seller they cost 3.7 dollars per hundred, that’s only 3.7 cents apiece.
You can find them cheaper, but I ordered them as a kit with other parts (reviews of a charger for a lithium battery and a current stabilizer for a flashlight). There is also a fourth component, which I ordered there, but more on that another time.
Well, I’ve probably already bored you with the long introduction, so I’ll move on to the review.
Let me warn you right away, there will be a lot of photos.
It all came in bags, wrapped in bubble wrap. Such a bunch :) 
The microcircuits themselves are neatly packed in a bag with a latch, and a piece of paper with the name is pasted onto it. It was written by hand, but I don’t think there will be any problems recognizing the inscription. 
These microcircuits are produced by different manufacturers and are also labeled differently.
MC34063
KA34063
UCC34063
Etc.
As you can see, only the first letters change, the numbers remain unchanged, which is why it is usually called simply 34063.
I got the first ones, MC34063. 
The photo is next to the same mikruha, but from a different manufacturer.
The one under review stands out with clearer markings. 
I don’t know what else can be seen, so I’ll move on to the second part of the review, the educational one.
DC-DC converters are used in many places; now it is probably difficult to find an electronic device that does not have them.
There are three main conversion schemes, all of them are described in 34063, as well as in its application, and in one more.
All the described circuits do not have galvanic isolation. Also, if you look closely at all three circuits, you will notice that they are very similar and differ in the interchange of three components, the inductor, the diode and the power switch.
First, the most common one.
Step-down or step-down PWM converter.
It is used where it is necessary to reduce the voltage, and to do this with maximum efficiency.
The input voltage is always greater than the output voltage, usually at least 2-3 Volts; the greater the difference, the better (within reasonable limits).
In this case, the current at the input is less than at the output.
This circuit design is often used on motherboards, although the converters there are usually multi-phase and with synchronous rectification, but the essence remains the same, Step-Down.
In this circuit, the inductor accumulates energy when the key is open, and after the key is closed, the voltage across the inductor (due to self-induction) charges the output capacitor 
The next scheme is used a little less frequently than the first.
It can often be found in Power-banks, where a battery voltage of 3-4.2 Volts produces a stabilized 5 Volts.
Using such a circuit, you can get more than 5 Volts, but it must be taken into account that the greater the voltage difference, the harder it is for the converter to work.
There is also one not very pleasant feature of this solution: the output cannot be disabled “software”. Those. The battery is always connected to the output via a diode. Also, in the case of a short circuit, the current will be limited only by the internal resistance of the load and battery.
To protect against this, either fuses or an additional power switch are used.
Just like last time, when the power switch is open, energy is first accumulated in the inductor; after the key is closed, the current in the inductor changes its polarity and, summed with the battery voltage, goes to the output through the diode.
The output voltage of such a circuit cannot be lower than the input voltage minus the diode drop.
The current at the input is greater than at the output (sometimes significantly). 
The third scheme is used quite rarely, but it would be wrong not to consider it.
This circuit has an output voltage of opposite polarity than the input.
It's called an inverting converter.
In principle, this circuit can either increase or decrease the voltage relative to the input, but due to the peculiarities of the circuit design, it is often used only for voltages greater than or equal to the input.
The advantage of this circuit design is the ability to turn off the output voltage by closing the power switch. The first scheme can do this as well.
As in previous schemes, energy is accumulated in the inductor, and after closing the power switch it is supplied to the load through a reverse-connected diode. 
When I conceived this review, I didn’t know what would be better to choose as an example.
There were options to make a step-down converter for PoE or a step-up converter to power an LED, but somehow all this was uninteresting and completely boring.
But a few days ago a friend called and asked me to help him solve a problem.
It was necessary to obtain a stabilized output voltage regardless of whether the input was greater or less than the output.
Those. I needed a buck-boost converter.
The topology of these converters is called (Single-ended primary-inductor converter).
A couple more good documents on this topology. , .
The circuit of this type of converter is noticeably more complex and contains an additional capacitor and inductor. 
This is how I decided to do it
For example, I decided to make a converter capable of producing stabilized 12 Volts when the input fluctuates from 9 to 16 Volts. True, the power of the converter is small, since the built-in key of the microcircuit is used, but the solution is quite workable.
If you make the circuit more powerful, install an additional field-effect transistor, chokes for higher current, etc. then such a circuit can help solve the problem of powering a 3.5-inch hard drive in a car.
Also, such converters can help solve the problem of obtaining, which has already become popular, a voltage of 3.3 Volts from one lithium battery in the range of 3-4.2 Volts.
But first, let's turn the conditional diagram into a principle one. 
After that, we’ll turn it into a trace; we won’t sculpt everything on the circuit board. 
Well, next I will skip the steps described in one of my tutorials, where I showed how to make a printed circuit board.
The result was a small board, the dimensions of the board were 28x22.5, the thickness after sealing the parts was 8mm. 
I dug up all sorts of different parts around the house.
I had chokes in one of the reviews.
There are always resistors.
The capacitors were partially present and partially removed from various devices.
The 10 µF ceramic one was removed from an old hard drive (they are also found on monitor boards), the aluminum SMD one was taken from an old CD-ROM. 
I soldered the scarf and it turned out neat. I should have taken a photo on some matchbox, but I forgot. The dimensions of the board are approximately 2.5 times smaller than a matchbox. 
The board is closer, I tried to arrange the board more tightly, there is not a lot of free space.
A 0.25 Ohm resistor is formed into four 1 Ohm resistors in parallel on 2 levels. 
There are a lot of photos, so I put them under a spoiler
I checked in four ranges, but by chance it turned out to be in five, I didn’t resist this, but simply took another photo.
I didn’t have a 13K resistor, I had to solder it to 12, so the output voltage is somewhat underestimated.
But since I made the board simply to test the microcircuit (that is, this board itself no longer has any value for me) and write a review, I didn’t bother.
The load was an incandescent lamp, the load current was about 225mA
Input 9 Volts, output 11.45 
The input is 11 Volts, the output is 11.44. 
The input is 13 volts, the output is still the same 11.44 
The input is 15 Volts, the output is again 11.44. :) 
After that I thought about finishing it, but since the diagram indicated a range of up to 16 Volts, I decided to check at 16.
At the entrance 16.28, at the exit 11.44 
Since I got hold of a digital oscilloscope, I decided to take oscillograms.
I also hid them under the spoiler, since there are quite a lot of them
This is of course a toy, the power of the converter is ridiculous, although useful.
But I picked up a few more for a friend on Aliexpress.
Perhaps it will be useful for someone. 
When the developer of any device is faced with the question “How to get the required voltage?”, the answer is usually simple - a linear stabilizer. Their undoubted advantage is their low cost and minimal wiring. But besides these advantages, they have a drawback - strong heating. Linear stabilizers convert a lot of precious energy into heat. Therefore, the use of such stabilizers in battery-powered devices is not advisable. Are more economical DC-DC converters. That's what we'll talk about.
Back view:
Everything has already been said about the operating principles before me, so I won’t dwell on it. Let me just say that such converters come in Step-UP (step-up) and Step-Down (step-down) converters. Of course, I was interested in the latter. You can see what happened in the picture above. The converter circuits were carefully redrawn by me from the datasheet :-) Let's start with the Step-Down converter:
As you can see, nothing tricky. Resistors R3 and R2 form a divider from which the voltage is removed and supplied to the feedback leg of the microcircuit MC34063. Accordingly, by changing the values of these resistors, you can change the voltage at the output of the converter. Resistor R1 serves to protect the microcircuit from failure in the event of a short circuit. If you solder a jumper instead, the protection will be disabled and the circuit may emit a magic smoke on which all electronics operate. :-) The greater the resistance of this resistor, the less current the converter can deliver. With its resistance of 0.3 ohms, the current will not exceed half an ampere. By the way, all these resistors can be calculated by mine. I took the choke ready-made, but no one forbids me to wind it myself. The main thing is that it has the required current. The diode is also any Schottky and also for the required current. As a last resort, you can parallel two low-power diodes. The capacitor voltages are not indicated on the diagram; they must be selected based on the input and output voltage. It's better to take it with double reserve.
The Step-UP converter has minor differences in its circuit:
Requirements for parts are the same as for Step-Down. As for the quality of the resulting output voltage, it is quite stable and the ripples are, as they say, small. (I can’t say about ripples myself since I don’t have an oscilloscope yet). Questions, suggestions in the comments.
Let's consider a typical circuit of a boost DC/DC converter based on 34063 chips:
IC outputs:
- SWC(switch collector) - output transistor collector
- S.W.E.(switch emitter) - emitter of the output transistor
- Tc(timing capacitor) - input for connecting a timing capacitor
- GND- Earth
- CII(comparator inverting input) - inverting input of the comparator
- Vcc- nutrition
- Ipk— input of the maximum current limiting circuit
- DRC(driver collector) - output transistor driver collector (a bipolar transistor is also used as an output transistor driver)
Elements:
L 1— storage choke. This is, in general, an element of energy conversion.
C 1- timing capacitor, it determines the conversion frequency. The maximum conversion frequency for 34063 chips is about 100 kHz.
R2, R1— voltage divider for the comparator circuit. The non-inverting input of the comparator is supplied with a voltage of 1.25 V from the internal regulator, and the inverting input is supplied from a voltage divider. When the voltage from the divider becomes equal to the voltage from the internal regulator, the comparator switches the output transistor.
C 2, C 3— output and input filters, respectively. The output filter capacitance determines the amount of output voltage ripple. If during the calculations it turns out that a very large capacitance is required for a given ripple value, you can make the calculation for larger ripples, and then use an additional LC filter. Capacitance C 3 is usually taken at 100 ... 470 μF.
R sc- current-sensing resistor. It is needed for the current limiting circuit. Maximum output transistor current for MC34063 = 1.5A, for AP34063 = 1.6A. If the peak switching current exceeds these values, the microcircuit may burn out. If it is known for sure that the peak current does not even come close to the maximum values, then this resistor can not be installed.
R 3- a resistor that limits the current of the output transistor driver (maximum 100 mA). Usually 180, 200 Ohms are taken.
Calculation procedure:
- Select rated input and output voltages: V in, V out and maximum output current I out.
- 2) Select the minimum input voltage V in(min) and minimum operating frequency f min with selected V in And I out.
- Calculate the value (t on +t off) max according to the formula (t on +t off) max =1/f min, t on(max)- maximum time when the output transistor is open, toff(max)— maximum time when the output transistor is closed.
- Calculate ratio t on/t off according to the formula t on /t off =(V out +V F -V in(min))/(V in(min) -V sat), Where V F— voltage drop across the output filter, V sat- voltage drop across the output transistor (when it is in the fully open state) at a given current. V sat determined from the graphs given in the documentation for the microcircuit (or for the transistor, if the circuit has an external transistor). From the formula it is clear that the more V in, V out and the more they differ from each other, the less influence they have on the final result V F And V sat, so if you don’t need super-accurate calculations, then I would advise, already with V in(min)=6-7 V, feel free to take it V F=0, V sat= 1.2 V (regular, mediocre bipolar transistor) and don’t bother.
- Knowing t on/t off And (t on +t off) max solve the system of equations and find t on(max).
- Find the capacitance of the timing capacitor C 1 according to the formula: C 1 = 4.5*10 -5 *t on(max).
- Find the peak current through the output transistor: I PK(switch) =2*I out *(1+t on /t off). If it turns out to be greater than the maximum current of the output transistor (1.5 ... 1.6 A), then a converter with such parameters is impossible. It is necessary to either recalculate the circuit for a lower output current ( I out), or use a circuit with an external transistor.
- Calculate R sc according to the formula: R sc =0.3/I PK(switch).
- Calculate the minimum capacitance of the output filter capacitor:
- C 2 =I out *t on(max) /V ripple(p-p), Where V ripple(p-p)— maximum value of output voltage ripple. Different manufacturers recommend multiplying the resulting value by a factor from 1 to 9. The maximum capacity is taken from the standard values closest to the calculated one.
- Calculate the minimum inductance of the inductor:
L 1(min) =t on(max) *(V in(min) -V sat)/I PK(switch). If C 2 and L 1 are too large, you can try to increase the conversion frequency and repeat the calculation. The higher the conversion frequency, the lower the minimum capacitance of the output capacitor and the minimum inductance of the inductor.
- The divider resistances are calculated from the relation V out =1.25*(1+R 2 /R 1).
Online calculator for calculating the converter:
(for correct calculations, use a dot rather than a comma as the decimal point)
1) Initial data:
(if you do not know the values of V sat , V f , V ripple(p-p), then the calculation will be made for V sat =1.2 V, V f =0 V, V ripple(p-p) =50 mV)
Below is a diagram of a step-up DC-DC converter, built according to the boost topology, which, when a voltage of 5...13V is applied to the input, produces a stable voltage of 19V at the output. Thus, using this converter you can get 19V from any standard voltage: 5V, 9V, 12V. The converter is designed for a maximum output current of about 0.5 A, is small in size and very convenient.
A widely used microcircuit is used to control the converter.
A powerful n-channel MOSFET is used as a power switch, as the most economical solution in terms of efficiency. These transistors have minimal resistance in the open state and, as a result, minimal heating (minimum power dissipation).
Since the 34063 series microcircuits are not suitable for controlling field-effect transistors, it is better to use them in conjunction with special drivers (for example, with a half-bridge upper arm driver) - this will allow you to get steeper edges when opening and closing the power switch. However, in the absence of driver chips, you can use a “poor man’s alternative” instead: a bipolar PNP transistor with a diode and a resistor (in this case it is possible, since the field source is connected to a common wire). When the MOSFET is turned on, the gate is charged through the diode, the bipolar transistor is closed, and when the MOSFET is turned off, the bipolar transistor opens and the gate is discharged through it.
Scheme:
Details:
L1, L2 - inductors 35 μH and 1 μH, respectively. Coil L1 can be wound with a thick wire on a ring from the motherboard, just find a ring with a larger diameter, because the native inductances there are only a few microhenries and you may have to wind them in a couple of layers. We take the L2 coil (for the filter) ready from the motherboard.
C1 - input filter, electrolyte 330 uF/25V
C2 - timing capacitor, ceramic 100 pF
C3 - output filter, electrolyte 220 uF/25V
C4, R4 - snubber, nominal 2.7 nF, 10 Ohm, respectively. In many cases, you can do without it altogether. The values of the snubber elements are highly dependent on the specific wiring. The calculation is carried out experimentally, after the board has been manufactured.
C5 - filter for mikruhi power supply, ceramics 0.1 µF
http://site/datasheets/pdf-data/2019328/PHILIPS/2PA733.html
| This diagram is also often viewed: |
The MC34063 is a fairly common type of microcontroller for building both low-to-high and high-to-low voltage converters. The features of the microcircuit lie in its technical characteristics and performance indicators. The device can handle loads well with a switching current of up to 1.5 A, which indicates a wide range of its use in various pulse converters with high practical characteristics.
Description of the chip
Voltage stabilization and conversion- This is an important function that is used in many devices. These are all kinds of regulated power supplies, conversion circuits and high-quality built-in power supplies. Most consumer electronics are designed specifically on this MS, because it has high performance characteristics and switches a fairly large current without problems.
The MC34063 has a built-in oscillator, so to operate the device and start converting voltage to different levels, it is enough to provide an initial bias by connecting a 470pF capacitor. This controller is very popular among a large number of radio amateurs. The chip works well in many circuits. And having a simple topology and a simple technical device, you can easily understand the principle of its operation.
A typical connection circuit consists of the following components:
- 3 resistors;
- diode;
- 3 capacitors;
- inductance.
Considering the circuit for reducing voltage or stabilizing it, you can see that it is equipped with deep feedback and a fairly powerful output transistor, which passes voltage through itself in a direct current.
Switching circuit for voltage reduction and stabilization
It can be seen from the diagram that the current in the output transistor is limited by resistor R1, and the timing component for setting the required conversion frequency is capacitor C2. Inductance L1 accumulates energy when the transistor is open, and when it is closed, it is discharged through the diode to the output capacitor. The conversion coefficient depends on the ratio of the resistances of resistors R3 and R2.
The PWM stabilizer operates in pulse mode:
When a bipolar transistor turns on, the inductance gains energy, which then accumulates in the output capacitance. This cycle is repeated continuously, ensuring a stable output level. Provided that there is a voltage of 25V at the input of the microcircuit, at its output it will be 5V with a maximum output current of up to 500mA.
Voltage can be increased by changing the type of resistance ratio in the feedback circuit connected to the input. It is also used as a discharge diode during the action of the back EMF accumulated in the coil at the time of its charging with the transistor open.
Using this scheme in practice, it is possible to produce highly efficient buck converter. In this case, the microcircuit does not consume excess power, which is released when the voltage drops to 5 or 3.3 V. The diode is designed to provide reverse discharge of the inductance to the output capacitor.
Pulse reduction mode voltage allows you to significantly save battery power when connecting low-power devices. For example, when using a conventional parametric stabilizer, heating it during operation required at least 50% of the power. What then can we say if an output voltage of 3.3 V is required? Such a step-down source with a load of 1 W will consume all 4 W, which is important when developing high-quality and reliable devices.
As the practice of using MC34063 shows, the average power loss is reduced to at least 13%, which became the most important incentive for its practical implementation to power all low-voltage consumers. And taking into account the pulse-width control principle, the microcircuit will heat up insignificantly. Therefore, no radiators are required to cool it. The average efficiency of such a conversion circuit is at least 87%.
Voltage regulation at the output of the microcircuit is carried out due to a resistive divider. When it exceeds the nominal value by 1.25V, the comporator switches the trigger and closes the transistor. This description describes a voltage reduction circuit with an output level of 5V. To change it, increase or decrease it, you will need to change the parameters of the input divider.
An input resistor is used to limit the current of the switching switch. Calculated as the ratio of the input voltage to the resistance of resistor R1. To organize an adjustable voltage stabilizer, the middle point of a variable resistor is connected to pin 5 of the microcircuit. One output is to the common wire, and the second is to the power supply. The conversion system operates in a frequency band of 100 kHz; if the inductance changes, it can be changed. As the inductance decreases, the conversion frequency increases.
Other operating modes
In addition to the reduction and stabilization operating modes, boost modes are also quite often used. differs in that the inductance is not at the output. Current flows through it into the load when the key is closed, which, when unlocked, supplies a negative voltage to the lower terminal of the inductance.
The diode, in turn, provides inductance discharge to the load in one direction. Therefore, when the switch is open, 12 V from the power source and the maximum current are generated at the load, and when it is closed at the output capacitor, it rises to 28 V. The efficiency of the boost circuit is at least 83%. Circuit feature when operating in this mode, the output transistor switches on smoothly, which is ensured by limiting the base current through an additional resistor connected to pin 8 of the MS. The clock frequency of the converter is set by a small capacitor, mainly 470 pF, while it is 100 kHz.
The output voltage is determined by the following formula:
Uout=1.25*R3 *(R2+R3)
Using the above circuit for connecting the MC34063A microcircuit, you can make a step-up voltage converter powered from USB to 9, 12 or more volts, depending on the parameters of resistor R3. To carry out a detailed calculation of the characteristics of the device, you can use a special calculator. If R2 is 2.4k ohms and R3 is 15k ohms, then the circuit will convert 5V to 12V.
MC34063A voltage boost circuit with external transistor
The presented circuit uses a field-effect transistor. But there was a mistake in it. On a bipolar transistor, it is necessary to swap the C-E positions. Below is a diagram from the description. The external transistor is selected based on the switching current and output power.
Quite often, to power LED light sources, this particular microcircuit is used to build a step-down or step-up converter. High efficiency, low consumption and high stability of the output voltage are the main advantages of the circuit implementation. There are many LED driver circuits with different features.
As one of many examples of practical application, you can consider the following diagram below.
The scheme works as follows:
When a control signal is applied, the internal trigger of the MS is blocked and the transistor is closed. And the charging current of the field-effect transistor flows through the diode. When the control pulse is removed, the trigger goes into the second state and opens the transistor, which leads to the discharge of gate VT2. This connection of two transistors Provides quick on and off VT1, which reduces the likelihood of heating due to the almost complete absence of a variable component. To calculate the current flowing through the LEDs, you can use: I=1.25V/R2.
Charger for MC34063
The MC34063 controller is universal. In addition to power supplies, it can be used to design a charger for phones with an output voltage of 5V. Below is a diagram of the device implementation. Her principle of operation is explained as in the case of a regular downward conversion. The output battery charging current is up to 1A with a margin of 30%. To increase it, you need to use an external transistor, for example, KT817 or any other.