Buck converter on MC34063 for mobile phone
You have to recharge your mobile phone battery on average once a week. If you read our reviews of mobile phones, then you may have already chosen an economical model that holds a charge for several weeks.
Over time, the properties of a mobile phone battery deteriorate, and you have to charge it more and more often. This is especially felt on old phones, which are a pity to throw away, but buying a new battery is impractical. In addition, the charge controller of older phones often breaks down and they only have to be charged using a frog.
One solution for such phones is to be powered by a high-capacity lead gel battery (for example, refurbished from UPS). Of course, a phone with such a battery is no longer mobile. It can lie on a shelf and be used as needed.
The converter's task is to lower the battery voltage (11-12 volts) to the voltage required to power the phone - 3.6 volts. The converter must have high efficiency in order to effectively use the energy stored in the battery. Linear stabilizers are undesirable here for the reason that part of the energy is converted into heat.
We present to your attention a pulse converter that has miniature dimensions (the board is 3x3 cm, and even smaller when using SMD components) and does not heat up at all.
The converter uses the well-known MC34063 chip. The parameters of the stabilizer can be easily calculated for the required values of output voltage and current. Therefore, on the basis of this converter it is easy to build, for example, a car charger for a phone or PDA.
The stabilizer circuit is a standard step-down (step-down) from the datasheet on the MC34063:
For convenience, we provide an online parameter calculator for this scheme. By setting the required voltage and current values, you can easily calculate the ratings of the parts.
| Online calculator MC34063 | |
| Here will be the result of the calculation | |
Please note that the higher the conversion frequency, the lower the inductor inductance and capacitor values required. Parameter I L is the value of the current for which the inductor must be designed, and L is the minimum value of its inductance (i.e. less is not possible, more is possible).
The printed circuit board can be, for example, as shown in the figure. It allows both the installation of calculated resistors to obtain a specific voltage, and the installation of a trimming resistor for adjustment. The capacitor at the converter input is in SMD version, installed on the side of the printed tracks. The output capacitor can be either SMD or lead-based. It is necessary that it be Low ESR, because... converter frequency is high. Please note that for SMD electrolytic capacitors, the stripe on the body indicates the positive terminal, not the negative terminal.
The assembled converter is connected with the output directly to the battery terminals of the mobile phone, and with the input - to the gel battery. Charging such a battery will last for a long time to operate the phone.
This circuit can also be used for other purposes, for example, to power LEDs, etc.
MC34063 Key Specifications
- Wide range of input voltages: from 3 V to 40 V;
- High output pulse current: up to 1.5 A;
- Adjustable output voltage;
- Converter frequency up to 100 kHz;
- Internal reference accuracy: 2%;
- Short circuit current limitation;
- Low consumption in sleep mode.
- Reference voltage source 1.25 V;
- Comparator comparing the reference voltage and the input signal from input 5;
- Pulse generator resetting RS trigger;
- Element AND combining signals from the comparator and generator;
- RS trigger eliminating high-frequency switching of output transistors;
- Driver transistor VT2, in the emitter follower circuit, to amplify the current;
- Output transistor VT1 provides current up to 1.5A.
MC34063 boost converter
For example, I used this chip to get 12 V power for the interface module from a laptop USB port (5 V), so the interface module worked when the laptop was running; it did not need its own uninterruptible power supply.It also makes sense to use the IC to power contactors, which need a higher voltage than other parts of the circuit.
Although the MC34063 has been produced for a long time, its ability to operate on 3 V allows it to be used in voltage stabilizers powered by lithium batteries.
Let's look at an example of a boost converter from the documentation. This circuit is designed for an input voltage of 12 V, an output voltage of 28 V at a current of 175 mA.
- C1 – 100 µF 25 V;
- C2 – 1500 pF;
- C3 – 330 µF 50 V;
- DA1 – MC34063A;
- L1 – 180 µH;
- R1 – 0.22 Ohm;
- R2 – 180 Ohm;
- R3 – 2.2 kOhm;
- R4 – 47 kOhm;
- VD1 – 1N5819.
Buck converter on MC34063
Reducing the voltage is much easier - there are a large number of compensating stabilizers that do not require inductors and require fewer external elements, but for a pulse converter there is work when the output voltage is several times less than the input voltage, or the conversion efficiency is simply important.The technical documentation provides an example of a circuit with an input voltage of 25 V and an output voltage of 5 V at a current of 500 mA.
- C1 – 100 µF 50 V;
- C2 – 1500 pF;
- C3 – 470 µF 10 V;
- DA1 – MC34063A;
- L1 – 220 µH;
- R1 – 0.33 Ohm;
- R2 – 1.3 kOhm;
- R3 – 3.9 kOhm;
- VD1 – 1N5819.
MC34063 inverting converter circuit
The third scheme is used less frequently than the first two, but is no less relevant. Accurate voltage measurements or amplification of audio signals often require bipolar power supply, and the MC34063 can help provide negative voltages.The documentation provides a circuit that allows you to convert a voltage of 4.5 .. 6.0 V into a negative voltage of -12 V with a current of 100 mA.
- C1 – 100 µF 10 V;
- C2 – 1500 pF;
- C3 – 1000 µF 16 V;
- DA1 – MC34063A;
- L1 – 88 µH;
- R1 – 0.24 Ohm;
- R2 – 8.2 kOhm;
- R3 – 953 Ohm;
- VD1 – 1N5819.
Analogues of the MC34063 chip
If MC34063 is intended for commercial applications and has an operating temperature range of 0 .. 70°C, then its full analogue MC33063 can operate in a commercial range of -40 .. 85°C.Several manufacturers produce MC34063, other chip manufacturers produce complete analogues: AP34063, KS34063. Even the domestic industry produced a complete analogue K1156EU5, and although it’s a big problem to buy this microcircuit now, you can find many diagrams of calculation methods specifically for the K1156EU5, which are applicable to the MC34063.
If you need to develop a new device and the MC34063 seems to fit perfectly, then you should pay attention to more modern analogues, for example: NCP3063.
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. 