Mobile phone charger. How to convert a cell phone charger to a different voltage Schematic diagram of a Chinese phone charger

In short, I was fucked up by my native charger for the Nokia phone with autumn, bitch, with a milipizdric connector:

It always goes away, falls out. Damn shorter.

Fortunately, the phone has a micro-USB connector that has already become a standard. Well, at least mine has. Yes, and do not kick for Nokia, I have a phone for communication. For entertainment tablet. (like fucked up). So, through this connector, the phone is perfectly charged if there is charging.

And then the other day they brought another, obsolete, its short age, the "original" Chinese Nokia charger. Employees take them down to me from time to time. I don’t know the fuck, I don’t fix them to anyone, well, except for this case, and then because for myself See because of the soldering iron on the table and a special reputation in our office. Well, not the point. She was with exactly the right microUSB connector:

I’ll say right away that the simplest thing would be to solder the cord to my native charger, but I didn’t look for simple ways. For the experience gained, though small, is very useful. By the way, you can still buy a new charger, but these are costs, travel time. I forget, I'm lazy.

I share my impressions, experience, well, a little humor does not hurt.

I gave myself a coffee so that I would not fall asleep while scrolling through Google for typical charging situations, experienced tips, repair cases. It gave little sense, because there are thousands of them, if not billions, like the Chinese. Although it gave a general idea of ​​​​charging circuitry and an understanding of cocky, or completely fucked up.

I covered the table with a rough draft, took out several suitable corpses, plugged the soldering iron into the socket, untwisted it for troubleshooting:

Charging with the right cord went around the world firmly. Nearly all semiconductor content burned out:

The second of the bins, xs from which, without a lace, looked perky, but did not work:

Just in case, I still had a working power supply, xs from what, but with quite competent circuitry, only change the swollen conder:

But I took pity on him and put him aside. In case of impossibility to fix that thread from the first two, I would take it.

Along the path of low resistance, the troubleshooting of the second charge showed a burned-out diode and a resistor, which the cunning Chinese, due to cheapening, use as fuses. I drink:

View from the other side. By the way, the circuitry is of a normal level, an order of magnitude better than the first charge:

It was decided to use the first one as a donor, the diode is normal, and the resistor has already burned out:

I found an analogue in the bins, which paid a little later:

ATTENTION! AHTUNG! WARNING!

I soldered the diode and the resistor, poked it into the socket, and the lit LED merrily turned green:

There is a contact.

"The resistor is weak," said the charge, and the sad gray smoke confirmed her words.

Okay, I said, and got into the bins in search of an analogue. Along the way, finding a varistor and a choke, which narrow-eyed people saved on. Resoldering:

New test, everything is ok (the photo did not turn out very well).

Most modern network chargers are assembled according to the simplest pulse circuit, on one high-voltage transistor (Fig. 1) according to the blocking generator circuit.

Unlike simpler circuits based on a 50 Hz step-down transformer, the transformer for pulse converters of the same power is much smaller in size, which means that the dimensions, weight and price of the entire converter are smaller. In addition, pulse converters are safer - if in a conventional converter, in the event of a failure of power elements, a high unstabilized (and sometimes even alternating) voltage from the secondary winding of the transformer gets into the load, then in case of any malfunction of the “pulse” (except for the failure of the reverse optocoupler connections - but it is usually very well protected) there will be no voltage at all at the output.

Rice. 1
A simple pulsed blocking oscillator circuit

A detailed description of the principle of operation (with pictures) and calculation of the circuit elements of a high-voltage pulse converter (transformer, capacitors, etc.) can be found, for example, in "TEA152x Efficient Low Power Voltage supply" at http://www. nxp.com/acrobat/applicationnotes/AN00055.pdf (in English).

The alternating mains voltage is rectified by the VD1 diode (although sometimes the generous Chinese put as many as four diodes in a bridge circuit), the current pulse when turned on is limited by the resistor R1. Here it is desirable to put a resistor with a power of 0.25 W - then, when overloaded, it will burn out, performing the function of a fuse.

The converter is assembled on a transistor VT1 according to the classic flyback circuit. Resistor R2 is needed to start generation when power is applied, it is optional in this circuit, but the converter works a little more stable with it. Generation is supported by the capacitor C1, included in the PIC circuit on the winding, the generation frequency depends on its capacitance and the parameters of the transformer. When the transistor is unlocked, the voltage at the lower terminals of the windings / and II is negative, at the upper ones it is positive, the positive half-wave through the capacitor C1 opens the transistor even more strongly, the voltage amplitude in the windings increases ... That is, the transistor opens like an avalanche. After some time, as the capacitor C1 charges, the base current begins to decrease, the transistor begins to close, the voltage at the top output of the winding II according to the circuit begins to decrease, through the capacitor C1 the base current decreases even more, and the transistor closes like an avalanche. Resistor R3 is needed to limit the base current during circuit overloads and surges in the AC mains.

At the same time, the amplitude of the self-induction EMF through the VD4 diode recharges the capacitor C3 - therefore, the converter is called a flyback. If you swap the terminals of the winding III and recharge the capacitor C3 during the forward stroke, then the load on the transistor will increase sharply during the forward stroke (it may even burn out due to too much current), and during the reverse stroke, the self-induction EMF will be unspent and will be allocated to collector junction of the transistor - that is, it can burn out from overvoltage. Therefore, in the manufacture of the device, it is necessary to strictly observe the phasing of all windings (if you confuse the terminals of winding II, the generator simply will not start, since the capacitor C1 will, on the contrary, disrupt generation and stabilize the circuit).

The output voltage of the device depends on the number of turns in the windings II and III and on the stabilization voltage of the Zener diode VD3. The output voltage is equal to the stabilization voltage only if the number of turns in the windings II and III is the same, otherwise it will be different. During the reverse stroke, the capacitor C2 is recharged through the diode VD2, as soon as it is charged to about -5 V, the zener diode will begin to pass current, the negative voltage at the base of the transistor VT1 will slightly reduce the amplitude of the pulses on the collector, and the output voltage will stabilize at a certain level. The stabilization accuracy of this circuit is not very high - the output voltage varies within 15 ... 25%, depending on the load current and the quality of the VD3 zener diode.
A diagram of a better (and more complex) converter is shown in rice. 2

Rice. 2
Electrical circuit more complex
converter

To rectify the input voltage, a diode bridge VD1 and a capacitor are used, the resistor must have a power of at least 0.5 W, otherwise, at the moment of switching on, when charging the capacitor C1, it may burn out. The capacitance of capacitor C1 in microfarads should be equal to the power of the device in watts.

The converter itself is assembled according to the already familiar scheme on the transistor VT1. The emitter circuit includes a current sensor on the resistor R4 - as soon as the current flowing through the transistor becomes so large that the voltage drop across the resistor exceeds 1.5 V (with the resistance indicated on the diagram - 75 mA), the transistor VT2 opens slightly through the VD3 diode and limits the base the current of the transistor VT1 so that its collector current does not exceed the above 75 mA. Despite its simplicity, such a protection scheme is quite effective, and the converter turns out to be almost eternal even with short circuits in the load.

To protect the transistor VT1 from self-induction EMF emissions, a smoothing circuit VD4-C5-R6 is added to the circuit. Diode VD4 must be high-frequency - ideally BYV26C, a little worse - UF4004-UF4007 or 1 N4936, 1 N4937. If there are no such diodes, it is better not to install a chain at all!

Capacitor C5 can be anything, however, it must withstand a voltage of 250 ... 350 V. Such a chain can be installed in all similar circuits (if it is not there), including in a circuit according to rice. 1- it will significantly reduce the heating of the body of the key transistor and significantly "prolong the life" of the entire converter.

Stabilization of the output voltage is carried out using the Zener diode DA1, standing at the output of the device, galvanic isolation is provided by the V01 optocoupler. The TL431 chip can be replaced with any low-power zener diode, the output voltage is equal to its stabilization voltage plus 1.5 V (voltage drop across the V01 optocoupler LED) ', a small resistance resistor R8 is added to protect the LED from overloads. As soon as the output voltage becomes slightly higher than the set value, a current will flow through the zener diode, the optocoupler LED will start to glow, its phototransistor will open slightly, the positive voltage from the capacitor C4 will slightly open the transistor VT2, which will reduce the amplitude of the collector current of the transistor VT1. The instability of the output voltage of this circuit is less than that of the previous one, and does not exceed 10 ... 20%, also, thanks to the capacitor C1, there is practically no background of 50 Hz at the output of the converter.

It is better to use an industrial transformer in these circuits, from any similar device. But you can wind it yourself - for an output power of 5 W (1 A, 5 V), the primary winding should contain approximately 300 turns of wire with a diameter of 0.15 mm, winding II - 30 turns of the same wire, winding III - 20 turns of wire with a diameter of 0 .65 mm. Winding III must be very well isolated from the first two, it is advisable to wind it in a separate section (if any). The core is standard for such transformers, with a dielectric gap of 0.1 mm. In extreme cases, you can use a ring with an outer diameter of approximately 20 mm.

This device was conceived for a long time and has been repeatedly tested, everything that is presented below is the author's development. Despite the very simple circuit, the device works very stably. The device itself is a charger for a mobile phone without the use of wires.

How does all this work?
On this site were published this device. The first version was not very effective, then other versions were invented. This option proved to be the most economical. The device allows you to charge the phone if the latter is at a distance of no more than 3 - 4 cm from the receiver. The basis of the first device is a highly efficient PWM controller that can generate rectangular pulses with a frequency of up to 1 MHz, but due to large losses, the idea turned out to be not very good, although this device allowed mobile devices to be charged at a distance of up to 50 cm from the receiver.
After some unsuccessful attempts to create such a device, a simplified blocking generator came to the rescue, which I successfully used in electroshock devices.

The main advantages of the device:
1) Low consumption
2) High efficiency (compared to counterparts)
3) Relatively large charging current
4) The ability to work from a reduced source (the first version worked from a voltage of 9-16 volts)
5) Simplicity and compactness

The transmitting part of the device consists of two main circuits. Each of them has a diameter of 10 cm, wound with a wire of 0.8 mm. The first circuit (L1) consists of 20 turns, the second of 35 turns of the same wire. The contours are stacked on top of each other and decorated with adhesive tape or insulating tape.

In advance, you need to number the leads of the coils, since they need to be phased. They phase like this - the beginning of the first coil is connected to the end of the second or vice versa, the main thing is to get one coil with a tap.

Next, we select the resistance (if you plan to start the device from a reduced source, then the resistor can be removed).
It is advisable to use a trimming resistor 0 ... 470 Ohm, the power of the resistor is not very important (0.25-2 watts).

How to setup? Just! we collect for a start the circuit of the receiver. We connect the power supply (any stabilized DC voltage source 4.5-9 volts). We adjust the resistor so that the quiescent current of the circuit does not exceed 150mA.
The maximum current consumption of the circuit is not more than 600mA, agree a little.
After selecting the optimal resistance, you can replace the variable with a constant resistor (0.25-1W). The resistance of the base limiter directly depends on the input voltage rating.

In my version, the transistor did not overheat, but just in case, install it on a small heat sink.
The device starts working from a voltage of 1 volt - another feature of this design, but it will not charge a mobile phone from such a voltage, instead it can be used as a converter to power low-power devices.

Transistor - literally any low-frequency transistor can be used, regardless of the structure. The circuit uses a KT818 transistor, it can be successfully replaced with 837, 816, 814 or 819, 805, 817, 815, only when using reverse conduction transistors, you should change the polarity of the power supply.

Receiver

The design of the receiver is outrageously simple - a circuit, a rectifier, a zener diode and a storage capacitor. The diode needs a pulse, preferably in the SMD version, since the entire circuit will be located in the mobile phone. In my case, a fairly powerful and common SS14 Schottky diode was used. Such a diode is capable of operating at frequencies up to 1 MHz, the current is up to 1A!

The capacitor is not critical, has a capacity of 47 to 220 microfarads (more of course is better, but there may not be enough space). Capacitor voltage from 10 to 25 volts.
Zener diode - any for a voltage of 5-6 volts (often found with a voltage of 5.6 volts, for example - BZX84C5V6).

The receiver circuit (L3) contains 15 turns of wire 0.3-0.7 mm, wound in a spiral on the outer or inner side of the back cover of the phone.

The circuit can be assembled on a compact board or placed in a convenient place using surface mounting, but it is advisable to fill the mounting with rubber glue or silicone.

Sony Ericsson K750 was used as an experimental phone, it is fully functional and was bought specifically for these experiments (purchased for spare parts for $ 5), then the handy Nokia N95 was already remade.
The device can charge a mobile phone fast enough, it all depends on the total power, in this case, a 1000mA battery is fully charged in 3 hours.

The current is transferred to the second circuit by the method of electromagnetic induction, in this case it is completely safe, since the frequency is lowered, there are no harmful effects on a person.

In order to install the receiving circuit, the mobile phone is disassembled. An industrial charger is connected to the charging socket and the polarity is found on the contacts of the socket. Next, the outputs of the receiver are connected to the corresponding outputs of the socket.

The contour can be attached to the back cover of the phone using epoxy, silicone (highly undesirable), super glue (use only when the contour is planned to be fixed on the outside of the cover).

List of radio elements

Designation	Type	Denomination	Quantity	Note	Shop	My notepad
VT1	bipolar transistor	KT818A	1	KT837, KT816, KT814		To notepad
VD1	zener diode	BZX84C5V6	1	5-6 Volts		To notepad
VD2	Schottky diode	SS14	1			To notepad
C1	electrolytic capacitor	10uF	1

Now all cell phone manufacturers have agreed and everything that is in stores is charged via a USB connector. This is very good, because chargers have become universal. In principle, a cell phone charger is not.

This is only a pulsed DC voltage source of 5V, and the actual charger, that is, the circuit that monitors the charge of the battery and ensures its charge, is located in the cell phone itself. But, the point is not this, but the fact that these “chargers” are now sold everywhere and are already so cheap that the issue of repair disappears somehow by itself.

For example, in a store, “charging” costs from 200 rubles, and on the well-known Aliexpress there are offers from 60 rubles (including delivery).

circuit diagram

A diagram of a typical Chinese charge, copied from the board, is shown in fig. 1. There may also be a variant with the rearrangement of the diodes VD1, VD3 and the zener diode VD4 to a negative circuit - Fig. 2.

And more "advanced" options may have rectifier bridges at the input and output. There may be differences in part numbers. By the way, the numbering on the diagrams is given arbitrarily. But this does not change the essence of the matter.

Rice. 1. A typical diagram of a Chinese network charger for a cell phone.

Despite the simplicity, this is still a good switching power supply, and even a stabilized one, which is quite suitable for powering something other than a cell phone charger.

Rice. 2. Scheme of a network charger for a cell phone with a changed position of the diode and zener diode.

The circuit is based on a high-voltage blocking oscillator, the generation pulse width of which is controlled by an optocoupler, the LED of which receives voltage from a secondary rectifier. The optocoupler lowers the bias voltage based on the key transistor VT1, which is set by resistors R1 and R2.

The load of the transistor VT1 is the primary winding of the transformer T1. Secondary, lowering, is winding 2, from which the output voltage is removed. There is also winding 3, it also serves to create positive feedback for generation, and as a source of negative voltage, which is made on the diode VD2 and capacitor C3.

This negative voltage source is needed to reduce the voltage at the base of the transistor VT1 when the optocoupler U1 opens. The stabilization element that determines the output voltage is the Zener diode VD4.

Its stabilization voltage is such that, in combination with the direct voltage of the IR LED of the optocoupler U1, it gives exactly the necessary 5V that is required. As soon as the voltage on C4 exceeds 5V, the VD4 zener diode opens and current flows through it to the optocoupler LED.

And so, the operation of the device does not raise questions. But what if I need not 5V, but, for example, 9V or even 12V? This question arose along with the desire to organize a network power supply for a multimeter. As you know, popular in amateur radio circles, multimeters are powered by Krona, a compact 9V battery.

And in "field" conditions, this is quite convenient, but in home or laboratory I would like to be powered from the mains. According to the scheme, “charging” from a cell phone is in principle suitable, it has a transformer, and the secondary circuit does not come into contact with the mains. The problem is only in the supply voltage - "charging" gives out 5V, and the multimeter needs 9V.

In fact, the problem with increasing the output voltage is solved very simply. It is only necessary to replace the VD4 zener diode. To get a voltage suitable for powering a multimeter, you need to put a zener diode on a standard voltage of 7.5V or 8.2V. In this case, the output voltage will be, in the first case, about 8.6V, and in the second about 9.3V, which, both, is quite suitable for a multimeter. A zener diode, for example, 1N4737 (this is 7.5V) or 1N4738 (this is 8.2V).

However, another low-power zener diode for this voltage is also possible.

Tests have shown that the multimeter performs well when powered by this power supply. In addition, an old pocket radio powered by Krona was also tried, it worked, only interference from the power supply slightly interfered. The voltage in 9V is not limited at all.

Rice. 3. Voltage adjustment unit for reworking a Chinese charger.

Do you want 12V? - No problem! We put the zener diode on 11V, for example, 1N4741. Only you need to replace the capacitor C4 with a higher voltage one, at least 16V. You can get even more stress. If you remove the zener diode at all, there will be a constant voltage of about 20V, but it will not be stabilized.

It is even possible to make a regulated power supply by replacing the zener diode with a regulated zener diode such as the TL431 (Figure 3). The output voltage can be adjusted, in this case, by a variable resistor R4.

Karavkin V. RK-2017-05.