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.

The need to have a charger out of reach of outlets cannot be overemphasized.

Take the same international trains, the trip on which can last about a day or two. The leadership in the field of entertainment devices on the road is still held by mobile phones (aka smartphones, as you wish), as well as tablets, laptops and e-readers.

So, as for laptops, the amount of energy absorbed is practically irreplaceable on the road using AA batteries or AA (fingers) or AAA (little fingers) form factor batteries. As for e-books, their energy reserve is quite enough for a month of work; Of course, we are talking about e-books with E-Ink technology (electronic ink).

But mobile devices are simply designed to be charged on the road using batteries :)

I’ll tell you right away, so as not to bother, you can buy a cheap, cool portable charger to suit your taste right on the Internet!

So, a small digression into the theory about the capacity and survivability of batteries.

The capacity of an average smartphone is ~1500mAh at a voltage of 3.7V; total ~5.5W. Referring to Wikipedia, I will provide some data on size “AA”:

Carbon-zinc (salt) battery: 550-1100 mAh.
Alkaline, so-called alkaline battery: 1700-3000 mAh.
Lithium battery: 2500-3000 mAh.
Nickel-cadmium battery: 600-1000 mAh.
Nickel metal hydride battery: 1400-3000 mAh.
The indicated values ​​of the capacity of salt and alkaline cells are valid for discharge with low currents not exceeding tens of mA. When discharged with currents of hundreds of mA, the capacity of these elements decreases several times.

And when charging phones, hundreds of mA are consumed, which means that when charging a mobile phone battery, the capacity of the AA battery will drop to approximately 150-300mAh, which at a voltage of 1.5V will give a power of ~0.45W.

Further, the efficiency of pulse converters is on average 80%, so only ~0.35W will reach the phone. Now you can calculate approximately how many of these batteries are needed for one full charge of a smartphone: 5.5/0.35?16! Sixteen pieces! Let's take a more specific example: the battery capacity of my not-so-modern smartphone is 2150mAh. How many batteries are needed for a 100% charge? That's right, 23. So batteries are certainly widely available, but they are becoming obsolete.

Things are much better for rechargeable batteries that are similar to “fingers”, but slightly larger in size - 18650 cells, the average capacity of which varies within 2700mAh at a voltage of 3.7V. The average power of such batteries is respectively about 10W per unit. By the way, laptop batteries are made of these elements. It turns out that one such element is enough to fully charge almost any smartphone.

The advantages of using 18650 batteries are obvious:

One or two pieces for two to six charges is enough;
Rechargeable, i.e. reusable;
They don't take up much space.
The disadvantages are not so obvious, but they still exist:

Expensive;
To charge, you need a special charger.

So, we have decided on the type of energy source, all that remains is to decide on a device that will supply energy to the phone in a form convenient for it. All smartphones need 5V to charge. And the voltage of our source is less, so we need a boost converter. This time the Step-Up Inverting Switching Regulator MC34063A acts as such.

There is nothing wrong with this microcircuit. For calculations, you can, of course, use the datasheet, a bunch of formulas that are given there; or you can use this form, by entering the data into which, you will receive a list of all the required denominations plus a circuit that will change to step-up or step-down depending on whether the input voltage is greater than the output voltage or not.

Vin - input voltage;
Vout - output voltage;
Iout - output current;
Vripple is the ripple voltage;
Fmin - minimum frequency of the converter.

I used this form to calculate the denominations. All that remained was to buy the parts, etch the board and solder it.

The payment turned out like this:

Of course, in my photographs there is no inscription with the site address on the printed circuit board :) But I will be very pleased if you leave it :). This MC34063A mobile phone charging board can be downloaded from this link. As you can see, there is an LED on it to indicate the presence of output voltage.

Traditionally, the etching process is:

Upon completion of which we receive an almost finished board on a silver platter :)

We erase the toner, drill, admire the bare board with holes for the last time...

And carefully solder all the components into place. The result was like this:

Yes, it would be possible to add capacitors and a choke, but this is pointless, since the 18650 element will be even a little taller, so it will fit well into one case :)

I was counting on an input voltage of three volts. I received my five at the output, and the device produces the declared current of 200mA remarkably well.

And now it's time for the test. I turn on the converter, connect the phone via USB and enjoy the joyful glow of the charging indicator on the phone! Do you remember that I wrote that I added an LED to the circuit for indication? So, he made me doubt the veracity of the charging process.

When the phone is not connected, it simply lights up, thereby indicating that the output voltage is present, and when I put the phone on charge, the LED on the converter begins to flicker, which indicates that the output voltage is inconsistent.

It turned out that the AAA batteries that I used for testing ran low very quickly, since the smartphone requires a charging current of 500mA.

Therefore, it was decided to postpone the tests until a couple of new 18650 elements were purchased, and the circuit and board would be modified by adding a field-effect transistor, which would take on the main job of pumping energy, and it would be easier to make a heat sink.

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.

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