How to make a wireless charger. Wireless charger for your phone. Wireless charging circuit

Since no one has yet invented an eternal source of energy, the batteries have to be recharged regularly cell phones and various digital gadgets from the mains. It is not always possible to do this in the usual way using a wire and socket. Some advanced companies have already begun producing models that can be charged simply by being on the wireless device site. Following their example, “homemade workers” do not stand on the sidelines, but try to improve even some push-button telephones.

New? No, the long-known “old”

To understand for a telephone, you need to remember Nikola Tesla and his method of transmitting energy over a distance. Using a device working according to the method, more than 100 years ago he was able to provide electric current to an entire state.

How is it used now? There is a built-in coil, which is the creator and transmitter magnetic field to the device's antenna. The receiving circuit is a coil laid in a flat spiral, located directly under the phone cover. Electromagnetic radiation occurs only after the receiver is placed in the transmitter field. The energy is then applied to the battery through capacitors and a rectifier.

First, let's talk about the disadvantages of using the device.

Could there be any negative aspects to such a wonderful invention? It turns out there are several of them:

it is unknown how high-frequency pulses affect human health;
low efficiency was noted when transferring energy in this way;
Full charging time increases by a couple of extra hours;
If, at every opportunity, without waiting for the battery to completely reset, you place your phone on a charger, the working capacity of the battery will quickly decrease;
if the diagram according to which the wireless charging is assembled with your own hands is not entirely correct or the wrong components are used, the battery may overheat, which is “not good.”

There is no information yet about other disadvantages.

Instructions for modifying the “push-button”

Is the charging cable input not working on your old phone? Now this is an easily solved problem! A little more than a meter of thin copper wire is taken and wound into a flat coil of 15 turns. To ensure that the spiral retains its shape, it is secured with superglue or double-sided tape, leaving a couple of centimeters of wire for soldering the contacts. One end of the coil is connected to the phone charging socket through pulse diode, the second - through a capacitor. Wireless charger, made with your own hands, is not a joke, but the use of the laws of physics.

To make a transmission circuit, 1.5 cm turns are laid around a circle with a diameter of 10 cm. The winding is fastened with electrical tape or tape, leaving both ends of the wire free. Thinner copper for the transmitter is wound 30 turns in one direction. The circuit is closed by a field-effect transistor and a capacitor. Wireless charging (with your own hands) is ready: if you put the phone with the receiver under the cover inside the transmitting ring with the screen facing up, the battery will begin to receive energy.

Universal wireless phone charger

Laptops and movie cameras, cameras and tablets - all these devices require constant power. Moreover, it is very inconvenient to store at home or carry with you a whole set of several different wires. To get rid of this inconvenience, some time ago several of the world's leading mobile communications manufacturers agreed to maintain a single standard in the use of chargers.

Gadgets that support this opportunity, are marked with the Qi logo. It is planned to equip cafes, libraries, and other public places with such technical equipment. IKEA is developing samples of furniture that will have wireless charging built into its working panel. With your own hands, you only need to put your phone or laptop in a designated place (at night or lunchtime), and the energy will begin to flow.

Will the smartphone and iPhone also have to be disassembled?

Wireless charging for Samsung is by far the most unusual, since it is a functional computer monitor that supports standard OS. Installing this device allows you not only to free the work surface from unnecessary wires for mobile phones, powering them from a distance: when you place the gadget on its platform, charging starts automatically, and a green LED lights up on the monitor that supports the universal Qi standard.

Not long ago, the inventors of Nikola Labs demonstrated one of the cases. This one is capable of accumulating uselessly wasted radiofrequency radiation Wi-Fi signals, converting it into energy. Thanks to this miracle case, the working time of your smartphone is extended by almost a third.

Today I decided to present to your attention two converter circuits that are wireless chargers for mobile phone. The basis of the charger is the induction method, we have a transmitting coil and a receiving coil. The first coil creates an electromagnetic field, the second generates a current, and most importantly, the device does not work on the principle of a transformer, there are no hearts here!

And so, the first converter circuit is made on the UC3845 timer, the microcircuit plays the role of a master oscillator. Powerful field-effect transistor amplifies the voltage and supplies it to the transmitting coil, thus generating alternating current in the winding high frequency, which creates an electromagnetic field around the circuit. Due to this, an alternating voltage is formed in the second coil; this voltage must first be rectified, then the noise must be smoothed out using a capacitor and supplemented with a zener diode to stabilize the voltage.

We select the zener diode based on the voltage that can charge the phone; for most phones the voltage rating is 5.5 volts.

Let's move on to the details of the scheme. The diode in the circuit must be ultra-fast; other types of diodes will not work! We select an 820 Ohm resistor with a power of at least 2 Watts, it will heat up and low-power diodes will simply burn out. The field-effect transistor can be replaced with a similar one; the power of this converter is quite large - up to 70 Watts and therefore the transistor must be mounted on a heat sink. The inductor can be excluded from the circuit; it is wound on a ferrite ring from an old power supply and contains 20 turns of wire, with a diameter of 0.8 - 1 mm. It serves to smooth out network interference. The transistor can be replaced with an IRFZ44, although it will work a little worse.

The printed circuit board is shown below.

Let's talk about contours. The transmitter circuit contains 20 turns, the inner diameter of the circuit is 10 cm, the circuit is wound with a wire with a diameter of 0.5 to 1.5 mm, when using a thick wire (diameter from 1 mm), the power of the transmitter field will increase, this will allow you to charge a mobile phone at a distance of up to 30 - 40 cm from the receiver. To increase the range, you can use large coils with a diameter of up to 1 meter. The receiver circuit contains 40 turns of wire with a diameter of 0.4 - 0.7 mm. See the receiver diagram below.

The second circuit (receiver circuit) can be used from the old one hard drive(disassemble the device and see where it stands), the coil provides the desired voltage and has a compact size, it can be adapted to the back of a mobile phone, it is advisable to use diodes for rectification in the SMD version, to save space, a capacitor with a voltage of 16 volts, a capacity of 220 up to 470 microfarads. We connect the power through the appropriate plug to the mobile phone, then turn on the transmitter (the transmitter is powered by a stabilized power source of 10-12 volts, current from 3 amperes), then you just need to place the mobile phone 10 - 50 cm from the transmitting coil.

The second circuit is assembled using reverse conduction transistors, the frequency is set by a multivibrator, then the signal is sent to transistor amplifier voltage, as a result of which an electric current of high frequency is formed in the circuit. Multivibrator transistors can be used KT315 or imported analogues C9014, C9018 or others. The remaining transistors of the KT819 type, in extreme cases, can be replaced with KT805; the last transistors need to be mounted on the heat sink. As noticed this scheme powered by two different voltages; any source can be used to power the multivibrator direct current with a voltage of 4 to 6 volts (you can use lithium - ion battery from a mobile phone), to power the transistor amplification stage you will need a voltage of 10 to 14 Volts with a current of at least 1.5 A.

This scheme is no worse than the first, so it’s up to you to choose which one to assemble! The resistors in the second circuit are all 0.5 Watt. To create this article, a previously produced one was donated... but I think it was worth it, although many will probably not understand me, but this is something new, because similar topics on the Internet have not been considered before, then an alternative solution, and charging your mobile phone will be faster than usual (depending on the distance of the coils). The maximum current transmission distance at the indicated ratings is 50 cm, then the current strength will drop sharply.

The phenomenon of electromagnetic induction was observed even before Faraday, but the great Michael was the first to find an explanation for it and tried to transmit electric force over a distance by induction. Currently, the transmission of electricity to short distances At higher frequencies, wireless communication is becoming more widespread; thus they are already charging car batteries conventional cars and even traction batteries for electric vehicles. As a result, do-it-yourself wireless charging is a request that is very popular among tinkerers. What fuels interest in the topic is that manufacturers of wireless chargers set their prices from the heart, and power receivers with wireless power supply are disproportionately expensive compared to their wired counterparts of the same type.

Wireless phone charging is very convenient: no need to fuss with wires and plugs, especially at night when your eyes are already sticking together. In addition, phones, smartphones and tablets are becoming thinner. In general, this is not bad, but the charge connector, which should pass a current of up to 2A, has become so flimsy that it can break due to awkward movement or fail, the contacts will slightly oxidize. And without wires - just put the device (gadget) on charge, and it charges.

In the induction boom, chargers for gadgets stand apart; the controversy surrounding them is extremely hot. Some consider wireless charging almost a product of hellish forces: they say, there is something built into it that zombifies the user into actively accepting certain religious, commercial or political trends, and at the same time ruins his health. Others, on the contrary, identify the electromagnetic field (EMF) of charging with the almost mystical power of Qi, which guarantees ascending reincarnation to the owner. The truth in this case lies not in the middle, but completely to the side, so the purpose of this article is to provide information about the following:

How, being, as they say, not in the know and not wanting to bother with all sorts of intricacies, when buying exactly choose wireless charging harmless and safe. The power of Qi is already a matter of pure faith. Its existence, like any other something else omnipresent, omniscient and omnipotent, cannot be proven or refuted by the arguments of reason.
The principle of operation and design of WPC standard chargers for gadgets.
How to properly charge the battery of a phone, smartphone, tablet.
Methods of transmitting electricity over a distance without wires.
Harmful factors and dangers associated with the use of wireless chargers.
Is it possible and how to convert an old mobile phone to the WPC standard?
How to assemble a wireless charger at home, suitable for any WPC standard gadgets and completely safe, costing no more than $10 for components.

How to choose harmless charging

Einstein once said: “If a scientist cannot explain to a five-year-old child what he does, then he is either mad or a charlatan.” The power of Qi is the power of Qi, but all our actual achievements are based on objective knowledge that does not depend on the subject. Let's say we brought an Amazonian savage to our home, there are others like that there. They took him to the TV and said: “If you plug this thing, a plug, here into the socket, and press here, then a picture will appear here, and sound will come from here.” If the savage does everything as told, the TV will turn on, the picture will appear, the sound will play, although the savage has no idea about electricity and electronics, and considers a thunderstorm to be an indigestion for his gods. So the kettle is full, as they say, maybe choose wireless charging for your gadget, which you can use without fear:

Make sure that the device has a WPC standard compliance icon (see below);
Please show the charging: in addition to the Power or I/O indicator, there should be a Charge indicator or indicated by the same icon as on the gadget;
please turn it on. Power should light up, but Charge should not;
We put the gadget on charge – Charge should light up, and the gadget’s display should show the charge;
We lift the gadget no more than 3 cm above the charging platform - Charge should go out and the display should show that charging has stopped.

This type of wireless charging can be safely used at home if it is located no closer than 1.5-2 m from places of long-term stay of people(bed, desk, favorite sofa in front of the TV). You can’t keep wireless charging turned on in a child’s room. incl. and described below, which can be constantly turned on on the nightstand by an adult’s bed.

What is WPC

WPC is an abbreviation for Wireless Power Consortium, the name of the company that first brought wireless charging to the market. WPC technology is nothing new, much less supernatural; The components of WPC charging and its operating principle are shown in Fig. The familiar iron transformer also operates on the transmission of electricity by induction. The peculiarity of WPC is that the operating frequency is increased to tens of kHz or even MHz; this allows you to separate the primary and secondary windings at some distance and do without a ferromagnetic core, because The energy flux density (PED) of EMF increases with frequency; Also, with increasing frequency, the technical ability to concentrate EMF in a limited area increases. But at the same time, the biological effect of EMF increases with frequency, which is why small and weak wireless charging can be more dangerous than an industrial induction heating installation.

Note: WPC is still an industry standard, in our opinion; it has not yet been formalized by international agreements. Therefore, the technical data of gadgets with WPC, especially from alternative manufacturers, may differ so that they are charged only from “their” charger. If you do wireless charging yourself, you need to give the design margin and the technological ability to modify the transmitter for a specific device, see below.

Devices designed for recharging using the WPC system are indicated by a special icon (item 1 in the figure). It means that the device has a receiving coil of 25 turns and an RF converter alternating current to permanent. A number of gadgets are available with or without WPC. Then the induction receiver is either “thrown” and located under the battery cover (pos. 2), or modular, pos. 3. In any case, a connector (item 4) or clamping contacts are provided for the WPC receiver, where it should be connected homemade receiver when finalizing a gadget for WPC. The polarity is determined by the multitester when wired charging is connected, because... Wireless charging contacts are paralleled with those of conventional charging.

Note: Under no circumstances should the WPC receiver be connected directly to the battery! In the best case, an expensive battery will soon fail, because... In the device it is charged in a special way, see below. And modern high-capacity lithium batteries can simply explode if charged directly to the terminals!

In some gadgets, the WPC receiver is hidden under a cover, the removal of which requires partial disassembly of the device, pos. 5. One way or another, if your model without WPC has a “twin” with wireless charging discovered by searching on the Internet, then yours will also have a cavity for the receiver: it would be too expensive to produce various parts of the case. This greatly simplifies the development of the gadget for WPC, but you need to make sure that this model Available in both versions.

About the charging mode

The battery in any gadget is charged under the control of a special controller, which first determines how discharged the battery is. If it is more than 75%, then an increased fast (forced) charge current is immediately supplied, equal to approximately the 3-hour discharge current, if Charger provides it. No - the charging takes the current that it can provide when the output voltage drops to 5 V. Therefore, many devices from USB ports take a long time to charge, because standard output USB power supply 5 V 350 mA.

The forced charge is designed to eliminate the polarization of the battery electrodes, which causes the so-called. hysteresis. The capacity of the “hysteresis” battery continuously decreases, and its resource turns out to be much less than declared. A fast charge with a current of less than 3 hours does not completely eliminate the hysteresis, and the battery soon runs out. As a result, charging for a smartphone or tablet must provide a charge current of more than 1.5 A, because in “smart” gadgets, batteries are 1800-4500 mAh, i.e. their 3-hour discharge current will be 0.9-1.5 A.

After the battery has been charged for approx. up to 25% capacity, the charging current gradually decreases to the value of a small forming (recharging) current until the battery is “pumped” for approx. by 75%. Forming the battery with a small current avoids electrodegradation of the electrolyte, which also reduces the battery life. The forming current is approx. current of 12-hour battery discharge.

Finally, when the battery is fully charged, the controller passes a very tiny current through it for the minimum required time to prevent chemical degradation of the electrolyte, and only then gives a signal about the end of the charge. Therefore, keeping a gadget with a working and properly designed controller on charge for more time is not at all harmful, on the contrary. The author has old phone Motorola W220. For the sake of experience, it is charged all the time, except when you need to leave the house with it. Over more than 10 years of use, the battery has not noticeably lost its capacity: the 4 days of “hibernation” and 4 hours of continuous conversation specified in the phone’s passport have not decreased. And other users of the same model had to change the completely depleted battery.

Induction or radiation?

Induction

The transfer of electrical power over a distance occurs through an electromagnetic field (EMF), in which a certain energy is stored. For inductive energy transfer, in addition to the transmitter, you also need a receiver, not necessarily electronic. It could be, for example, an aluminum pan, in the metal of which the EMF transmitter induces Foucault eddy currents that heat the dishes. The currents induced in the receiver create their own EMF, which interacts with the EMF of the transmitter. As a result, a common EMF is formed between the transmitter and the receiver, which transfers power from the first to the latter. Hence the first characteristic feature of inductive energy transfer is the influence of the receiver on the operating mode of the transmitter, the so-called. source response to load.

Note: EMF with the induction method of energy transfer is especially highly concentrated near the source-receiver system in the presence of ferromagnetic materials there. An example is an electrical transformer based on iron or, at higher frequencies, on a ferrite core.

It is advisable to transmit power by induction at lower frequencies, because High frequency EMF (HF) does not penetrate deep into conductors, this is the so-called. surface effect or skin effect, and with increasing frequency, energy losses due to radiation increase. The EMF energy flux density (EMF PPE) at low frequencies is low, because EMF energy in a given volume from a source of a certain intensity depends on frequency.

The first difference between power transmission by radiation and induction is that the EMF “breaks away”, “leaves” from the source, losing contact with it, i.e. is emitted. If, for example, you give an impulse with a combat laser into space, and then turn off or destroy the source, then the packet of EMF oscillations will rush and rush in world space until it hits an obstacle and is absorbed by it or dissipates in the propagation medium. The consequence is that when power is transmitted by radiation, there is no reaction from the source to the receiver. A second-order consequence is that the ability of EMF to spontaneously concentrate is also absent, because the radiation itself tends to “spread” to the sides; to assemble it in a given area, special design and technical measures are needed. Unlike the induction method, the presence of ferromagnets in the transmitter coverage area reduces the power transfer coefficient, because ferromagnets “pull” EMF towards themselves, which should get into the receiver.

The efficiency of energy transfer by EMF radiation depends on the frequency of its oscillations, because There is no on-demand field pumping by the transmitter. What is “downloaded” into the emitted packet will be there. It is possible to add energy to the consumer only by continuing the radiation. Another feature is that the material that most effectively absorbs the flow of EMF power is not a conductive material, but, on the contrary, absorbs EMF energy; these properties are used in microwave ovens. A long insulated conductor of a certain configuration (for example, twisted into a spiral), which in this case represents a receiving antenna, can also be an absorber of EMF energy.

Both

In order to meet the requirements of minimum weight and dimensions and the absence of foreign ferromagnets near the radio path of the gadget, WPC developers had to increase the operating frequency of the system; After all, tablets also have transceivers for working in a Wi-Fi environment. As a result, WPC gained the ability to work with both induction and radiation. This feature allows, in principle, to increase the range of WPC to several meters, which is what some amateurs use. Such enthusiasts, apparently, either do not know at all about the biological effects of EMFs, or deliberately ignore such information.

In this case, it is impossible to say “the problems of the Indians are the problems of the Indians”, because “Indians” may turn out to be strangers, ignorant and uninvolved people, for example, neighbors behind the wall or their own children. Before you start making wireless charging, you need to figure out under what circumstances it will be harmful or dangerous and how to avoid it.

However, a very definite intermediate conclusion can already be drawn - wireless charging must be selected upon purchase (see above) or done only by induction and spontaneously, without additional automation, switching without a receiver at the charging site to standby mode with the generator power reduced to a safe level. Of course, it’s completely convenient when the phone is lying around anywhere in the room and is still charging, but it’s healthy - you understand.

Note: There is no point in charging with a generator that turns off without a phone on charge. After all, then to charge the gadget you will have to turn it on, which reduces the convenience of wireless charging to almost nothing. Wireless charging must be done with a very sharp, as they say, acute, reaction of the generator to the receiver. There is also no point in integrating a mechanical or opto-sensor for the presence of a gadget into the charging; it can be triggered by something similar to it, but does not force the generator to reduce power.

Factors of harm and danger

The effect of EMF on living organisms also depends on the frequency of its oscillations. In general, it monotonically increases with frequency approx. up to 120-150 MHz, and then bursts and dips are observed. In one of them, visible light, we have adapted to live in the course of evolution; One of the others operates microwave ovens around 2900 MHz. But the microwave dip in EMF bioactivity is shallow, otherwise it will not be absorbed by the products, as long as it is technically possible and not very difficult to shield the oven from EMF radiation to the outside. Therefore, if you are planning to repair a microwave oven yourself, you need to know exactly how it works, how it works, what is possible, what is permissible to do and what is not allowed to prevent the microwave from siphoning out, and know how to determine at home whether the microwave is siphoning bake. But let's get back to the topic.

The EMF PPE also increases with frequency, so the norms for its level are tied to the PPE. In addition, individual sensitivity to PPE EMF varies within a very wide range, approx. 1000 times. In countries with frankly redneck labor and social legislation, permissible levels PES to monstrous values up to 1 (W*s)/sq. m. Approach in this case: were you warned when hiring? Do they pay for your additional medical insurance? Will they guarantee an increased pension for harmful activities after 10 (15, 20) years? The rest is Indian problems.

In PPE of this level, a person directly feels the effect of EMF: heaviness in the head, gentle warmth coming from the depths of the body. Gentle, but extremely dangerous: this is evidence of the beginning of plasmolysis of cells, which is why they can undergo malignant degeneration. “The device at half past six” is still the most terrible consequence of “picking up the bunny” PPE EMF.

In the USSR, the other extreme was in effect - 1 (μW*s)/sq. m, i.e. a million times less. The impact of such a PPE on the most sensitive subject will not affect either immediately or in the long term. Each citizen, or rather subject, of the “Council of Deputies” was actually the property of the state, but it also guaranteed his life, health and safety. At least formally.

For a market economy, such reinsurance will be unbearable, and in the current clogged airwaves, it is hardly technically feasible. Therefore, the generally accepted standard for the EMF PES level today is intermediate – 1 (mW*s)/sq. m. Such a PPE, which affects constantly and for a long time, will certainly give long-term consequences, but regular exposure to it for no more than a certain time per day is harmless and safe for the average person. Those who are overly sensitive are screened out by a medical examination during hiring, and the consequences of random deviations can already be compensated for without overtaxing social funds. Also, of course, a redneck approach, treating cancer in retirement instead of rest is not great pleasure, but at least within reason. Therefore, we will consider wireless charging potentially dangerous if it creates a PPE EMF of 1 (mW*s)/sq.m within a touch radius (approx. 0.5 m). m or more.

Safety calculation

Let's believe the advertising and buy a “super-duper” USB-powered charger (power consumption - 1.75 W), operating within a radius of 20 cm (0.2 m). The efficiency of a blogging generator (see below) of this power using a field-effect transistor is approx. 0.8; 1.4 W will go on air without a gadget lying on the site. The area of a sphere with a radius of 0.2 m is 0.0335 sq. m. PES on it will be 2.8/0.0335 = 41.8 (W*s)/sq. m(!). The PES value is inversely proportional to the square of the distance from the source. At what point in this case will it drop to the permissible 1 (mW*s)/sq. m? The calculation is simple: we take the square root of the ratio of the actual PES to the permissible one, and multiply the result by the initial radius of 0.2 m, i.e. divide by 5; we get... 20.4 m! This is what manufacturers' assurances of product safety are worth. Along with the power of Qi.

The above statement about the gadget on the site is not accidental. In this case, the charge at frequencies whose wavelengths are much greater than the gap between the emitter and the device will be inductive, if the receiver is suitable for it. The receiving coil of the gadget is uniquely suitable as an induction receiver. A gap of 3 cm (see above) will give a frequency of 10 GHz, which the generator is definitely not capable of producing; In reality the gap is even smaller. So the preliminary conclusion is confirmed: our charging should be only and only inductive. The EMF PES in the gap between the inductor and the device will then be many times greater, but this is no longer dangerous, because The EMF will naturally be drawn to the receiving coil, the diameter of which is approx. 5 cm. At a distance from it three times greater (more precisely, e times, e = 2.718281828...) the presence of EMF can only be detected by a sensitive detector, but calculations “on your fingers” cannot be done here; for the conclusion you need to use the means of mathematical physics .

Note: The fact that the WPC standard is not international makes it possible for manufacturers of wireless chargers to “go to extremes” based on safety assurances. You can refer to the safety standards of the country where production is taking place. Or the one where the company is registered, and there may be no regulation of PES at all; there are still such state entities left in some places.

About car chargers

From the calculation above it follows that wireless car chargers definitely dangerous: their range of action reaches 1 m. These marketers would be in such PPE for life... or at least until they feel the “device at half past six”... The justification given is the relative short duration of the impact and the need to protect an expensive gadget from damage due to the fact that it is dangling on a cord under the cigarette lighter. But wouldn’t it be smarter to simply extend the cord so that the gadget could be stored in the glove compartment or other convenient place? Driving a car with a phone in your hand is still risky, and in some places you can be fined for it.

If the gadget is without WPC

There are only 2 mandatory requirements for the WPC receiving coil: the number of turns is 25 and the wire diameter is designed for a current of 0.35 A, taking into account the skin effect at frequencies up to 30 MHz. Practically - from 0.35 mm for copper (without insulation). Thicker, when there is enough free space in the case, will only be better. Configuration – any according to location. Special care in manufacturing is not required (item 1 in the figure), but it is necessary that the ratio of the largest transverse dimension to the smallest does not exceed 1.5, otherwise the efficiency of the receiver will drop and the charge will be delayed.

If charging is done for an old plump phone or for a tablet without WPC, the coil is placed in the body of the gadget. A slight bend in place (item 2) will not affect the properties of the receiver. Suddenly there is not enough space inside (you still need to tuck the electronic components of the receiver somewhere), you will have to make a flat coil “like a branded one”, pos. 4. It is convenient to lay the wire in a flat spiral using tape placed on the substrate with the adhesive side up. To ensure that the Velcro does not wrap up and does not creep, it is fixed at the edges with strips of the same tape, applied with glue down. A round boss with a diameter of approx. is placed on the tape. 1 cm and lay turns around it, pressing the wire against the Velcro. When as many turns as necessary are laid, the boss is peeled off, the finished coil is dug to fix the turns with superglue or nitro varnish, pos. 3, and remove together with tape; its excess is trimmed off.

Doing exercises

Generators of homemade wireless charging and some of the factory ones are assembled according to the blocking generator circuit, or simply blocking, see figure:

We will do charging with a generator harmonic vibrations according to the antediluvian circuit with weak inductive coupling. It fell out of use in industrial equipment back in the 20s of the last century, as soon as three-point generators, inductive and capacitive, were invented, precisely because of the very acute reaction to the load, but that’s what we need! And other shortcomings of a generator with a weak coupling are either eliminated by modern element base and circuitry, or are not fatal. So, at the beginning of a forced charge, the power consumption reaches 25 W, so a separate power source is needed. But the average long-term charge of a tablet with a 3500 mAh battery constantly turned on every night does not exceed 8 W, and in a month such charging will “wind up” as much as 5.75 kW/h.

But first of all, let's deal with the transmitting coil, because... this circuit is also sensitive to the parameters and quality of the frequency-setting nodes. To set up the generator (safety is worth something, nothing can be done) you will also have to hastily make a receiving coil, see above. You can use charging for its intended purpose only when the generator is set up, but then it works more stable and safer for the gadget than charging while blocked. Therefore, you can use any gadget with this charger: it is designed for 2 amperes of charging current or more. But an old phone with a 450 mAh battery will take from it no more than what the controller “prescribes” due to the same acute reaction to the load.

Transfer coil

Drawings of generator coils with weak inductive coupling are shown in Fig. below.:

On the left – contour L2 (see below); on the right - coil feedback L3 (in the middle) and charge indicating circuit coil L1. They are etched on a plate made of 2-sided foil fiberglass laminate 100x100 mm, 1.5 mm thick, so-called. laser-iron technology LUT. There is nothing complicated about it, the idea and name are amateurish. LUT allows you to make printed circuit boards at home no worse than branded ones, signs with inscriptions, contour drawings, patterned panels, etc., see the video below:

Video: laser ironing technology

In addition to this, we can say that it is best to clean the blank for LUT with a regular school eraser. Then the scraps of copper are washed off with a cotton swab or a white, clean cotton rag, generously moistened with 96% alcohol or nitro solvent, and then, while the surface is wet, wiped dry with a microfiber cloth for cleaning glasses. The toner of any type is firmly placed on the surface prepared in this way. laser printer and even inkjet from a template on a suitable (holding, but not absorbing ink) base.

Note: do not be confused by the width of the tracks in the drawing (0.75 mm for the contour coil). The permissible current density in a film conductor on a substrate is several times greater than in a round wire, and the skin effect is weaker. Yes, the path is on printed circuit board 10 mm wide and 0.05 mm thick can easily hold a current of 20 A, and this is far from the limit. Double-width feedback coil tracks are needed because... During the setup process, you will need to resolder the tap on it. In general, LUT allows you to obtain tracks up to 0.15-0.2 mm wide.

Circuit design

The diagram of a wireless charger on a generator with inductive coupling is shown in Fig: on the left is the transmitter; receiver on the right. Its features, firstly, are the powerful active element VT3. It can only be an amplifying field-effect transistor. A generator based on a bipolar transistor will have low efficiency, and powerful field switches of the IRF, IRFZ, IRL series from computer power supplies or systems electronic ignition V active mode does not work.

The second is the auto bias circuit VD3 C3. For powerful amplifier field workers, the initial drain current can reach 100-200 mA or more. Without a blocking potential on the gate, it will be possible to configure the generator only for power or standby mode, but not for both, and the PES from the inductor within the contact radius will certainly exceed the permissible value. But it is also impossible to form an auto-bias by connecting a resistor to the source circuit, as in the cathode circuit in tube amplifiers: the generator will not reach full power, because As the source current increases, the displacement will also increase in absolute value. Therefore, the bias circuit is made nonlinear on the diodes: at low powers it increases in accordance with the source current, which ensures a soft start of the generator and its safety for any gadgets, and when the diodes enter saturation, the bias becomes close to fixed and allows the generator to “swing to its fullest.” The bias circuit is selected during the setup process from powerful rectifier diffusion RF diodes (PiN, KD213, KD2997 structure) and Schottky diodes (SMD structure) for a current of 6 A. The saturation voltage of the former in the current range of 0.7-5 A varies within 1- 1.4 V; second - 0.4-0.6 V.

Elements R1, VD1, VT1, VT2, C1, R2, VD2 and L1 make up the charge indication circuit. If the current transfer coefficient β VT1 is more than 80, then VT2 is excluded, and the R2 engine is connected to the VT1 base. Capacitor C3 must be film; Even better is the old paper one, because... It dissipates significant reactive power.

The receiver of this charger also has special features. The first is full-wave rectification of the received current, because harmonic vibrations. Application of this device This does not interfere with charging gadgets with built-in WPC, because... in them, the received current is also rectified by a diode bridge for better use of the inductor radiation. The second is that ceramic C5 is connected in parallel with the storage electrolytic capacitor C4. “Electrolytes” have a large self-inductance and a significant dielectric loss tangent tgδ, which reduces the charge efficiency at operating frequencies. Bypassing the “electrolyte” with “ceramics” reduces the charging time by approx. by 7%. For a tablet with a 3500 mAh battery, this will be approx. half an hour. Agree, sometimes it’s significant.

Finally, the VD8 diode. It protects the gadget’s charge controller if it is placed on an inductor connected to wired charging. You never know what comes to mind. Maybe someone will think that double charging will charge the device faster. The charge controller will still not allow more current into the battery than it should, but it may not be able to withstand such abuse. If such a situation is excluded, then VD8 is also excluded; then VD7 is needed for a voltage of 5.6 V. Its operating current is indicated with a large margin, because the maximum charge current never passes through it due to the acute reaction to the generator load. Practically - set any low-power junk device to the required voltage. He holds it - well, let him hold it. If it gets hot, we install something more powerful and more expensive; The charge controller also has its own overvoltage protection.

Note: without VD7, the rectified voltage will be the maximum permissible in WPC 7.2 V, which allows you to charge tricky “alternative” gadgets. It can be reduced by re-soldering the hot end L2 (see below) closer to the center of the coil, but no more than 6-7 turns.

Setting up

Setting up the generator begins with setting its quiescent current Iп without excitation. To do this, L3 is turned off, and gate VT3 is connected to the common wire (item 1 in the figure), i.e. form a zero offset. Next, selecting the VD3 chain, set Ip within the specified limits. If the drain current at zero bias is less than 50 mA, IP can be set to 15-20 mA, the generator will become more economical and safer. Suddenly the initial drain current is less than 40 mA, even better, then C3 and VD3 are not needed.

The next stage is phasing the windings. To do this, you will need a probe from the receiving coil (see above) with an incandescent light bulb connected to it, pos. 2. The generator circuit is restored, turned on, and a probe is placed on L2. The light should light up. No - swap pins L2 or L3. The coils need to be phased so that the hot (farthest from the center) end L3, pos. 3. At the same stage, measure and record the operating current consumption Ip, pos. 4.

Now you need to set the safe standby current of the generator Id; The emitted power in standby mode will drop in proportion to the square of the ratio of the operating current to the standby current. Id is set by resoldering the hot lead L3 in the positions indicated in pos. 5 limits closer to the minimum value. The return to power is checked by placing a probe on L2. The installation procedure is quite tedious. To avoid tightening it and soldering until the track peels off, proceed as follows. instructions:

L3 is reduced by half (pos. 6);
Id turned out to be small, or the probe does not show a return to power - we return half of the discarded turns, pos. 7;
Id is still large - we discard half of the remaining half of L3, pos. 8;
situation according to point 2 - we return half of the turns discarded according to point 3, but not half of all discarded, pos. 9;
if necessary, continue the setup, following the same algorithm.

Thus, using the iteration method, setting Id takes very little time.

All that remains is to configure the charge indication circuit. To do this, assemble a receiver loaded with a resistor of such a size that the charge current is less than the forming current, but greater than the content current, pos. 10. The R2 engine is placed in the lower position, the receiver is placed on L2. By rotating the engine, VD1 glows. They remove the receiver and see if VD1 goes out. No - the engine is turned back very smoothly and carefully until VD1 goes out.

Design

Further reduction of charging time and improvement of device safety parameters can be achieved by directing the flow of energy from the inductor upward; this technique is used in some branded wireless chargers. These can be recognized by the inductor surrounded by a ring, unless very smart alternativeists just stuck it on for sales.

In fact, the radiation direction is created by shielding the inductor from the rear side. To do this, the generator is placed in an open-top housing made of thin, no more than 0.25 mm, sheet metal. If the height of the housing is indifferent to aesthetics, the generator power source is also placed in it. In this case, it must be equipped with a power frequency transformer on hardware: interference from a closely located UPS will disrupt the generator settings.

Steel is needed for magnetic shielding in addition to electrical shielding, and its thin thickness is needed to prevent losses due to eddy currents. For the same purpose, frequent thin vertical slits are made in the sides of the body, and the bottom is perforated in a checkerboard pattern, see fig. The ideal option is the walls and bottom of the housing made of fine-mesh steel mesh. Cover – any radio-transparent plastic without filler: glass, acrylic, fiberglass, fluorine paste, PET, PE, polypropylene, polystyrene. An option is colorless transparent acrylic or nitro varnish in 4-5 layers, but not paint or enamel. External design can be anything. It is with this design that you can keep wireless charging for your phone, smartphone, or tablet constantly on on your bedside table. Although in today’s extremely littered ether, it is still better to stay away from any known sources of EMF.

Mobile devices have long become an integral part of the life of a modern person. But for them to work, you must constantly use the power supply to replenish the battery life. The cord often becomes a hindrance when using the gadget during charging. To effectively solve this problem, is it enough to find out how to make wireless charging with your own hands?

About the operation of the wireless charger

Wireless charging is not an innovation. They are created based on technology developed many years ago by engineer Nikola Tesla. The latter found a way to transmit energy over a distance. This was achieved thanks to magnetic induction. The discoverer of the technology was able to provide electricity to an entire state in this way.

In gadgets, the technique is used like this. The coil built into the charger plays the role of creator and conductor of the magnetic field, which is directed to the device’s antenna. The receiving circuit is a flat spiral coil located under the cover of the mobile phone. The emission of electromagnetic pulses is activated only after the receiver comes within the range of the transmitter. Through capacitors and a rectifier, the gadget’s battery is affected.

About the disadvantages of a wireless charging system

Experts have found that such a convenient device at first glance has some significant drawbacks. These include:

lack of data regarding the degree of negative impact of high-frequency pulses on the human body;
low level of energy transmission efficiency;
increasing the time to fully restore the battery charge by at least two hours;
the risk of reducing the working capacity of the battery arising from connection to the charger before the battery is completely zeroed;
If you assemble the device incorrectly or use unsuitable components for wireless charging, the battery may overheat, which can lead to rapid wear.

A simple technology for modifying a push-button mobile phone

To improve your mobile phone, you need to do a number of things: simple actions. After updating the gadget, problems such as failure of the charging socket, tangled wires, etc., will become insignificant.

To implement wireless charging, you will need a couple of meters of thin copper wire. The conductor must be wound into a coil. The optimal number of turns is 15 pcs. It is advisable to secure the spiral with glue or double-sided tape to maintain its shape. In this case, a few centimeters of wire are left for soldering the contacts. To connect to the charger socket, a pulse diode and a capacitor are used, attached to different ends.

In order to create a wireless charging transmission circuit, turns of 1.5 cm in size are formed. The diameter of the coil after twisting should be 10 cm. Both ends should be free. The rest of the structure is held together using electrical tape or adhesive tape.

Next, 30 turns of thinner copper conductor are wound for the transmitter. A transistor and a capacitor are used to close the circuit. By placing the device equipped under the receiver cover in the area of the transmitting ring with the display facing up, you can achieve wireless charging of the phone.

Features of universal charging

This universal device will become indispensable in any home. Today, almost every user has a whole arsenal of mobile technology: laptops, tablets, e-books, cameras. Using personal charging for each of them is extremely inconvenient and impractical.

Leading equipment manufacturers helped solve this problem. Some time ago they agreed to equip devices with chargers that have a single standard. Equipment that supports this function is marked with the Qi symbol. It is likely that similar technologies will soon appear in public institutions - restaurants, cafes, libraries, etc. It is worth noting that the largest “apple” brand was not included in the association of manufacturers. Later, the developers of this company released their own iQi Wireless Charger charger.

If you are interested in assembling a homemade charger, you should watch the video with the master class. Here the developers cut the USB cable into three parts, removing the middle part. The remaining fragments were used to attach the induction coil. To strengthen the field of influence, a magnet was placed on the power supply. This experiment showed that the coverage area here is 15 m.

Why might you need wireless charging?

We are all tired of piles of extension cords and wires that get tangled with each other, gather dust and get lost.

Extension cords fray and stop charging. Or the problem may be in the smartphone socket. One way or another, wireless charging can make life much easier.

True, it still cannot be called completely wireless. The device itself will still have to be connected to a source of electricity. But you can simply put the phone on the charger and go about your business with a clear conscience.

The cost of such devices may vary. There are more expensive and cheaper charging cables for phones that we are used to. However, some enthusiasts are trying to do wireless charging themselves. There may be several reasons for this. Perhaps someone prefers to make do with minimal funds. Or maybe the passion for creating something with your own hands plays a role here. We wrote about this above.

Today it is already difficult for us to imagine our life without mobile gadgets. This has led to a huge number of wires accumulating near household outlets, among which it is not so easy to find the necessary “charging”. In this case, a wireless charger will help solve the problem. The principle of its operation is very simple - just place the gadget on a special panel for it to charge. The accessory is based on the operating principle of an induction coil. This technology is called Qi. She has become very popular lately. In 2015, the globally popular brand began selling furniture that would have a wireless charging module built into it. Today, all flagship smartphone models support Qi. It is expected that transmitters, or, in other words, modules, will soon be found in airports, restaurants, cinemas, fast food outlets, and shopping centers, which will allow phones and tablets to be charged at any time. In fact, this will make life easier for users of mobile gadgets. We are entering a new era where it is not necessary to carry everything with us everywhere for all the devices we use.

Wireless chargers for gadgets with support for Qi technology

The wireless power standard is called Qi. In Russian the word is pronounced “Qi”. The standard bears this name in honor of the term of Eastern philosophy. It is developed by the Wireless Electromagnetic Power Consortium WPC. This organization unites global electronics manufacturers and sets itself an important task - to standardize the process of charging gadgets using the induction method.

In the near future, all devices will be able to be charged without connecting to the network. It's incredibly convenient. Each of us has at least once encountered a situation where... We have to urgently look for a way out. Soon, wireless charging modules will appear in all public places, as well as in every user’s home. At home, you can simply place the module in a convenient place, and it will never get lost, unlike wired “charging”. You just need to place the gadget on it and wait a bit until the battery capacity is replenished.

The operating principle of wireless “charging” is based on the properties of an induction coil to transmit electric current. In a school physics course, we were taught that when an induction coil is connected to a power source, a magnetic field arises in it, perpendicular to the turns of the coil. Thus, if you place two coils within the range of a magnetic field and at the same time connect one of them to a power source, then voltage will appear in the second coil. It is important to take into account the fact that the two induction coils should never touch each other. This simple principle is used in the operation of wireless chargers that support Qi technology.

There are two varieties of the Qi standard. The first involves charging at low power - 5 watts, and the second - at high power - 120 watts. High-power Qi is currently not produced by manufacturers due to objective factors. Using Qi at 120 watts, you can charge your laptop. Qi at 5 watts is used to replenish capacity and phones. It should be noted that tablets and smartphones require different amperages. A wireless phone charger produces a current of 1 ampere, and for tablet computer- 2 amperes. When choosing an accessory, be sure to pay attention to these characteristics.

Energy efficiency of the Qi standard

A modern wireless charger consists of two components. One of them is built directly into the gadget, which supports Qi and is called a wireless charging receiver. Essentially, it is a receiver that conducts electrical current to the battery. The second component is called the transmitter. If you mean buying a wireless “charging”, we are talking about a transmitter. They come in a variety of shapes and sizes. The most common types are round and rectangular transmitters.

To better understand how wireless charging works, you should consider that a magnetic field can transmit not only electric current, but also data about bytes and bits, which the developers of the Qi standard took into account. Interaction between the coils will occur only at the moment when the gadget with a built-in transmitter is close to the transmitter.

If the accessory for charging the gadget operates in the background, then the pulse sent every 0.4 seconds by the transmitter will not change the voltage in the coil built into the transmitter. We can conclude that a modern accessory can recognize in which mode to operate. As soon as a smartphone is nearby at a distance of a few centimeters, the voltage in the induction coil will drop sharply, and the device will go into active operation mode. As soon as the smartphone battery is charged, the corresponding signal will switch the charger to background mode. We can conclude that modern wireless accessories for replenishing battery capacity are energy efficient.

Is Qi technology safe?

Some users mistakenly believe that Qi wireless charging may be harmful to health. The fact is that magnetic radiation is not ionizing. In its effect on the body it is similar to a signal mobile communications, radio signal. In this case the signal mobile network, which comes from the tower, is stronger and has a continuous nature, while electromagnetic radiation disappears immediately after charging the smartphone battery.

The power of wireless chargers is 5 watts. It is not enough to have an effect on the human body. We can talk about a negative impact only if the power of such devices is 120 watts. But such models are not produced on an industrial scale. This explains the lack of wireless chargers for laptops. It is important to know that wireless battery charging technology has long been used in many models of electric shavers and electric toothbrushes, which once again proves its safety.

Which smartphones support wireless charging?

First of all, we want to note that not all gadgets today support the wireless charging function. Apple intentionally markets products that are not Qi compatible. In this case, we recommend purchasing a special case with a built-in induction coil.

Flagship devices generally always support Qi technology. These include the following popular models smartphones like Samsung Galaxy S6, Sony Xperia Z4v, Samsung Galaxy S6 Active, Google Nexus 6, Motorola Droid Turbo, Nokia Lumia 930, Samsung Galaxy S6 Edge. Already, dozens of models of the most different manufacturers can be charged using a wireless accessory, which provides maximum ease of use for users.

Is it possible to make wireless charging yourself?

Wireless chargers are quite expensive, considering that they are ordinary induction coil. The question arises: “How to make a module with your own hands?” In principle, if you have knowledge of basic physics and special equipment to measure the strength and power of electric current, this will not be a big problem. Fans of radio electronics are able to assemble not so simple devices, but we do not recommend ordinary users to carry out such experiments.

On the aliexpress.com website you can find separate wireless device receivers for some smartphone models, including the , Google Nexus line. It is quite easy to install it on your phone. Under the cover of the device there are two contacts, which provide a positive and negative pole. All you need to do is buy and connect the receiver, after which you can conduct a wireless charging test. This solution is optimal if you somehow got a wireless charger, for example, you were given a gift, and your gadget model does not yet support the Qi function.

Wireless battery charging technology is gaining increasing popularity in modern world. In the future, it will be possible to replenish the battery capacity in many public places. It is expected that stadiums, parks, restaurants, cinemas, and fast foods will be equipped with wireless chargers. When purchasing smartphones, we recommend paying attention to support for the Qi function, which is present in all flagship models 2015.