Do-it-yourself converter circuits 12 220 power per 1000 watts. High voltage and more. Inverter Circuit Improvements

When it is necessary to create mains voltage in a car, special converters 12-220 are usually used. On sale there are inexpensive standard inverters with a cost of about 20-30 dollars. However, the maximum power of such devices is at best about 300 watts. In some cases, this power is not enough.

You can get power for a powerful amplifier through small transformations. It is enough just to replace the secondary winding on a standard inverter. After that, you can get any value of the input voltage. For example, an inverter power of 400 watts will increase to 600 watts.

To increase power at home, experts recommend using a simple method. You will need to replace powerful bipolar keys with IRF 3205.

For work, an inverter was taken, to which it is permissible to connect 4 pairs of output transistors. Therefore, the device, after necessary work, will be able to deliver power of about 1300 watts. If you buy a ready-made inverter with such parameters, then its cost will increase to 100-130 dollars.

It is worth noting that the traditional push-pull circuit of the device does not contain protection against overheating, short circuit and output overloads.

The generator is based on the TL 494 microchip, which has an additional driver. It is necessary to replace low-power bipolar transistors with domestic analogues (KT 3107).

In order not to use powerful switches for power supply, the inverter is equipped with a remote control circuit.

In the driving part of the device, special SCHOTTKI diodes of type 4148 are used (domestic KD 522 is also suitable). The transistor in the remote control circuit is replaced with KT 3102.

After that, you can move on to the most critical part of the project - the transformer. This element is wound on a pair of glued 3000 NM rings. The size of each of them: 45x28x8. For a tighter fixation, the rings can be wrapped with tape.

Then the rings are wrapped on top with fiberglass (its cost in the store is no more than $ 1). It is perfectly acceptable to replace this material with fabric electrical tape.

Fiberglass is cut into small strips about 2 cm wide and no more than 50 cm long. The material for work has high heat resistance, and thanks to the thin base, the insulation looks neat.

For the primary winding, 2x5 turns of wire are needed, that is, 10 turns with a tap from the middle. The work is carried out with a wire with a diameter of 0.7-0.8 mm, and 12 wires go to each arm. More clearly, the process is presented in the following photographs.

The tourniquet is stretched, and 5 turns are evenly wound on both shoulders, stretching them all over the ring. The windings must be the same.

The resulting elements have four outputs. The beginning of the first winding must be soldered to the end of the second. The place of the solder will happen to be a tap for a power voltage of 12 V.

At the next stage of work, the ring must be insulated with fiberglass and covered with a secondary winding.

The secondary winding increases the output voltage. Therefore, when carrying out work, you must be as careful as possible and observe all precautions. It is worth remembering that high voltage is dangerous. Installation of the device is carried out only with the power off.

The winding of the rings is carried out using a pair of parallel strands of wire 0.7-0.8 mm. The number of turns is about 80 pieces. The wire is evenly distributed throughout the ring. At the final stage, additional insulation of the product with fiberglass is carried out.

When the assembly of the inverter is completed, you can start testing it. The device is connected to the battery, for starters, a 12 V battery from an uninterruptible power supply is suitable. In this case, the “plus” of power will go to the circuit through a 100-watt halogen lamp. It is worth paying attention that this lamp should not glow before and during work.

After that, you can proceed to check the field keys for heat generation. With a properly assembled circuit, it should be almost zero. If there is no input load, and the transistors are overheating, then you need to look for a non-working component in the device.

If the testing was successful, then you can install transistors on one common heat sink. To do this, use special insulating gaskets.

Schematic diagram in *.lay format is in the archive file and will be available after downloading.

12-220 Volt inverters are necessary to power the equipment if it is not possible to supply a household network. The peculiarity of the device is that it can be used to convert a DC voltage of 12 V to AC 220 V. Just a few decades ago, this seemed almost unthinkable, but today, when there is a huge element base, it will not be difficult to make such a converter.

Inverter power

You can use the car inverter 12-220 while traveling. Any household appliances will be able to work even in the field. That's just the maximum allowable load is small - a few hundred watts. The most powerful devices allow you to connect a load with a power of 2-3 kW, but the battery will quickly sit down. Types of loads by current consumption:

1. Reactive - partially consumes the energy received from the power source.
2. Active - energy is consumed to the maximum.

If you know exactly what load you will connect to the inverter, then it will not be difficult to calculate the maximum power. Let's say you plan to connect a load with a maximum power of 300 watts to the device. The power of the inverter itself should be about 25% more - such a margin is enough. Therefore, to fully meet the needs, an inverter with a power of 375 watts is needed. But you won't find one for sale. Therefore, you need to choose a device with a power of 400 W - the closest in value.

Where can these devices be used?

The simplest type of voltage inverter 12-220 volts are uninterruptible power supplies used in computer technology. But they have one big drawback - low power, the battery does not last long. And if a device is used in everyday life in tandem with a mini-power plant (even a wind turbine), then stable power is provided. Usually inverters can be found in such designs:

1. Security alarms.
2. Heating boilers.
3. pumping stations.
4. Computer servers and other systems.

In other words, they are used where it is necessary to constantly have a 220-volt supply network. Household voltage stabilizers are nothing more than inverters. Only in them is the alternating voltage converted to direct, stabilized, after which it again rises to 220 volts. Moreover, with the help of electric semiconductor switches and a PWM modulator, it is possible to achieve an almost perfect sinusoid.

Design features

Inverters 12-220 Volts are used quite widely. Ordinary motorists use them as a power source for long trips. You can simply turn on an electric razor, hair dryer, TV, even boil a kettle. True, the battery will quickly land. Therefore, it is better to use devices to power essential appliances and lighting.

The simplest homemade 12-220 V inverters can be made from several power transistors and a multivibrator. Operation of the device can occur even in severe frost. But for the heat, it is necessary to provide additional cooling, otherwise the transistors will fail. It is enough to install a simple cooler from a personal computer on a cooling radiator for semiconductor power transistors.

The simplest homemade inverter

Almost all inverters that are commercially available operate using high frequency current. Classical circuits, which were made on the basis of transformers, are completely forgotten, they were replaced by impulse structures.

On the basis of one K561TM2 chip, consisting of two D-flip-flops, you can make the simplest master path for the inverter. The circuit consists of a master oscillator, the role of which is performed by DD1, as well as a frequency divider made on a DD1.2 trigger.

Power transistors such as KT827 or KT819 are used to convert voltage. Very good results are shown by field-effect transistors of the IRFZ44 type. With the help of a master oscillator, a sinusoid is generated, which is necessary for the normal operation of the structure.

Features of the inverter

To obtain a circuit of 50 Hz, it is necessary to use a secondary winding and electrolytic capacitors connected in parallel with it and a load element. When no load is connected to the output, the circuit does not work. As soon as you connect any consumer, the inverter will start converting the voltage of 12 to 220 volts.

The output sine wave is far from ideal. This is a huge disadvantage of such a scheme. To produce an increase in power, it is necessary to use more expensive and efficient types of transistors. Pay attention to the electrolytic capacitor that is connected to the output. It must be rated for a minimum voltage of 250 V. It would be better if this value is higher than 300 V.

Devices based on modern element base

Such circuits can be used to power household appliances, fluorescent lamps, etc. In the design, power transistors of the KT819GM ​​type are mounted on a radiator with a large area to improve cooling. The circuit contains a master oscillator on the KR121EU1 logic element, by analogy, as in the case discussed above, and the IRL2505 field-effect transistors work well.

The choice for the KR12116U1 chip was not accidental - it has a two-channel adjustment of power switches. Therefore, for simple designs she fits perfectly. The frequency that the master oscillator will produce depends on the passive elements used in the circuit. With the help of a signal from the generator, the semiconductors are opened and locked.

When the channels in the transistors are open, then the resistance in it is only 0.008 ohms - this is very small. Therefore, low power transistors can be used. For example, if a transformer with a power of 100 W is installed at the output, a current of about 104 A will flow through the transistors in normal mode. In pulse mode, the peak value can be 350-360 Amperes.

Ready-made boards for assembling inverters

On sale you can find ready-made modules. They are boards on which are installed:

1. Transformer.
2. Semiconductor power switches.
3. Radiator.
4. passive elements.
5. Residual current devices, fuses.

Such an inverter 12 to 220 will give a pure sine at the output, since it is manufactured on a modern The cost of finished blocks is rather big. The most low-powered one will cost no less than 300-350 rubles, and even then this is the wholesale price. The higher the power of the device, the greater its cost.

But before using such devices, you need to find a suitable case. The board must be mounted in such a way that the internal space is well cooled. It is advisable to make additional forced cooling using a cooler from a personal computer. The 12-220 inverter, the diagram of which is shown above, must also be mounted in a reliable housing. The main thing is not to accidentally touch the high-voltage terminals.

Bespereboynik second life!

If you have an “extra” uninterruptible power supply that has completely run out of battery, you can still revive it. To do this, you need to make small changes:

1. Remove old battery.
2. Solder new wires to connect to the 12 volt battery.
3. At the edges of the wires, install terminals for connection to the car battery. If the device will be used in the car, you can make power from the cigarette lighter. But it is undesirable to do this - the high power of the device causes excessive heating of the wires.

To connect to an uninterruptible power supply household appliances, you need to make sockets. The easiest way is to make a transfer from an old surge protector and a piece of wire with a plug, which will include all the equipment.

Design features based on an uninterruptible power supply

With a good battery with a capacity of 55 A / h, such a design can maintain a normal temperature in an incubator for 100 eggs for up to a day, for example. Any farmer knows how terrible hypothermia is for incubators. True, the power of such a device is small, the air conditioner or refrigerator will not be able to work normally.

One drawback of this design is that the standard circuit will not be able to fully charge the car battery. Therefore, when the battery is completely dead, it is necessary to put it on charge from a normal device that delivers a current of more than 5-6 amperes.

Homemade powerful inverter

To make a 12v 220 3000W inverter with your own hands, you will need knowledge of the basics of electrical engineering, installation skills. You will have to make several specific elements. One of them is a pulse transformer. With its help, the voltage is increased from 12 to 220 volts. You also need to acquire a few expensive items. They are listed below:

1. PWM modulator. Required for the operation of semiconductor switches. With its help, the frequency of operation of the entire circuit is set. It should be noted that the switching frequency of power switches is several tens of thousands of times per second.
2. Semiconductor transistors, working as power switches, allow not only amplifying the signal, but also switching. They open and close, and when paired with a PWM modulator, they create an almost pure sine wave.
3. Aluminum radiators with a large surface area. The higher the power of the device, the larger the radiator area is required.
4. Foil material on which all elements are mounted. If desired, of course, you can perform a hinged installation, but it will take up too much space. Such a home-made 12-220 do-it-yourself inverter can be made in a few minutes, but it will not be safe to use it if you do not take action.
5. Passive elements - resistors, capacitors.
6. Connecting wires.

During the manufacture of the device, several electromagnetic relays may also be required for switching. By the way, it can be decided that instead of power switches it is permissible to use simple electromagnetic relays. There is only one thing - the switching speed is very high (40-60 thousand operations per second). Therefore, electromechanical devices do not cope with this task.

Ready inverters

If you don’t want to make a 12v 220 3000W inverter with your own hands, you can purchase a finished product in a beautiful case, with a lot of connectors for connecting devices. But the price hurts too much. The cheapest, whose power barely reaches 50 watts, you can buy for 800-1000 rubles. And its maximum is enough to charge a laptop battery or power several LED lighting lamps. An electric hair dryer or curling iron can no longer be connected to such a device.

More powerful devices (over 2000 W) have a corresponding price. The cheapest inverter 12-220 V will cost 3000-5000 rubles. But it all depends on the manufacturer. High-quality, multifunctional devices manufactured by well-known companies can cost over 20,000 rubles. That is why people who are more or less versed in electrical engineering prefer to make a 12-220 inverter with their own hands. Fortunately, the elements for manufacturing can be found in the simplest power supply for a personal computer.

You can literally from improvised materials. Even blocks from a simple uninterruptible power supply can be taken as a basis - it is, in fact, a double converter - first, the voltage is reduced to 12 V to ensure battery charging.

And then the voltage is increased to 220 V, the current is converted from direct to alternating. Such devices can be used to power household equipment outside the home - drills, grinders, televisions, etc. It is not difficult to make such a device on your own, and its cost will be less than that of similar devices that are sold in stores.

The principle of operation of the inverter

The second name of the converter is the inverter. In fact, it is with pulse-width modulation type. Power is supplied from a 12 volt DC source (in this case, from a battery). At the output of the device, pulses appear, in which the duty cycle changes. Depends on the ratio of time during which there is or is no voltage. With a duty cycle equal to one, the maximum current value is output. As the duty cycle decreases, the current decreases.

The voltage at any time at the output is 220 V. Even the simplest 12V to 220V converter can operate in a wide frequency range - 50 kHz ... 5 MHz. It all depends on the specific scheme and the elements used in it. The voltage frequency is very high, it will be fatal for powering household equipment. To reduce it to the standard 50 Hz, it is necessary to use specially designed transformers. The PWM modulator allows you to create an alternating voltage from a constant voltage with the required frequency.

Feedback system

If the PWM modulator has no load, the duty cycle is at a minimum level, the voltage value is 220 V. As soon as the load is connected to the device, the current will increase sharply and the voltage will drop, it will be less than 220 V. If you decide to make a voltage converter from 12 to 220 volt with your own hands, then be sure to consider the presence feedback. It allows you to compare the output voltage with a reference value.

If there is a difference in voltages, then a signal is sent to the generator, which allows you to increase the duty cycle of the pulses. With this system, it is possible to achieve maximum output power and a more stable voltage. As soon as the load is turned off, the voltage again jumps above 220 V - the feedback system fixes this and reduces the duty cycle value of the pulses. And so on until the tension is equalized.

Dealing with a dead battery

When the duty cycle and the value of the output current change, the load on the power source increases. This leads to its discharge and a decrease in voltage. And if a feedback system is used, it increases the duty cycle of the signals as much as possible, sometimes up to a maximum - one. Do-it-yourself 12/220 volt voltage converters without feedback react very strongly to dead batteries. During operation, the value of the output voltage is necessarily reduced.

If you plan to connect equipment such as angle grinders, electric lamps, boilers or kettles, then a decrease in voltage will not affect their operation. But in the event that the converter is needed to connect television equipment, laptops, computers, servers, amplifiers, feedback is simply necessary. It allows you to compensate for all power surges, which will ensure stable operation of devices.

Schema selection

To make a 12/220 V voltage converter with your own hands, you need to select a specific circuit. And be sure to consider the power of the devices that you plan to connect to it. Estimate approximately what load will be powered by the inverter. Be sure to add another 25% to the received power in reserve, it will not be superfluous. Based on the data obtained, you can choose a specific scheme. And of course one of important points- This

Assess your financial capabilities if you plan to purchase all components. And you will need a lot of expensive items. Fortunately, almost all of them are found in modern technology - in uninterruptible power supplies, power supplies for computers and laptops. By the way, a standard UPS can be used as a voltage converter, even no modifications are needed. Connect a more powerful battery to it and that's it. But you have to charge the battery additional source power supply - the standard one will not be able to generate the desired current value.

Elements of the converter circuit

The standard inverter design for converting 12 V DC to 220 AC consists of the following elements that can be found in any modern technology:

1. The PWM modulator is a microcontroller of a special design.
2. Ferrite rings for the manufacture of high-frequency transformers.
3. Power field effect transistors IGBT.
4. electrolytic capacitors.
5. Constant resistances of various power.
6. Chokes for filtering current.

In the event that you are not confident in your own abilities, you can independently assemble the converter according to the multivibrator circuit. The transformer for such a device is suitable from a UPS or a power supply for transistor TVs. Such a device has one drawback - impressive dimensions. But it turns out to be much easier to set up than complex structures that work with high-frequency current.

Operation of inverters

If you decide to make a 12/220 voltage converter with your own hands according to a simple scheme, then its power may be low. But it is quite enough to power household equipment. But if the power is above 120 W, then the current consumption increases to 10 amperes at least. Therefore, when used in a car, it cannot be plugged into the cigarette lighter socket - all the wires will melt and the fuses will fail.

Therefore, car inverters with a power of more than 120 W must be connected to the battery using an additional fuse and relay. Be sure to lay the wire from the battery to the installation site of the car inverter. To turn on the converter, you can use a key switch or a button paired with an electromagnetic relay - it allows you to remove high current from the controls.

Inverter 12V / 220V is a necessary thing on the farm. Sometimes it’s just necessary: ​​the network, for example, is gone, and the phone is discharged and there is meat in the refrigerator. Demand determines supply: for ready-made models of 1 kW or more, from which you can power any electrical appliances, you will have to pay somewhere from $ 150. Possibly over $300. However, making a do-it-yourself voltage converter in our time is accessible to anyone who knows how to solder: assembling it from a ready-made set of components will cost three to four times cheaper + a little work and metal from improvised trash. If there is for car batteries (batteries), you can generally meet 300-500 rubles. And if you also have basic amateur radio skills, then, having rummaged through the stash, it is quite possible to make a 12V DC / 220V AC 50Hz inverter for 500-1200 W for nothing. Consider the possible options.

Options: global

A 12-220 V voltage converter to power a load of up to 1000 W or more can generally be made independently in the following ways (in order of increasing costs):

1. Place a finished block in a case with a heat sink from Avito, Ebay or AliExpress. Searched for "inverter 220" or "inverter 12/220"; you can immediately add the required power. Will cost approx. half the price of the same factory. Electrical skills are not required, but - see below;
2. Assemble the same from the set: printed circuit board + “scatter” component. It is purchased there, but diy is added to the request, which means for self-assembly. Price still approx. 1.5 times lower. You need basic skills in radio electronics: use a multimeter, knowledge of the wiring (pinouts) of the outputs of active elements or the ability to search for them, the rules for including polar components (diodes, electrolytic capacitors) and the ability to determine what current of what section the wires are needed for;
3. Adapt a computer uninterruptible power supply (UPS, UPS) for the inverter. A serviceable used UPS without a standard battery can be found for 300-500 rubles. No skills are needed - the auto battery is simply connected to the UPS. But you will have to charge it separately, also see below;
4. Choose a conversion method, a diagram (see below) according to your needs and the availability of parts, calculate and assemble completely on your own. Perhaps for nothing, but in addition to basic electronic skills, you will need the ability to use some special measuring instruments(also see below) and perform simple engineering calculations.

From the finished module

Assembly methods according to paragraphs. 1 and 2 are actually not that simple. Cases of ready-made factory inverters serve at the same time as heat sinks for powerful transistor switches inside. If we take a "semi-finished product" or "placer", then there will be no case for them: at the current cost of electronics, manual labor and non-ferrous metals, the difference in prices is explained precisely by the absence of the second and, possibly, the third. That is, you will have to make a radiator for powerful keys yourself or look for a ready-made aluminum one. Its thickness at the place where the keys are installed should be from 4 mm, and the area for each key should be from 50 square meters. see per kW of output power; with airflow from a computer fan-cooler for 12 V 110-130 mA - from 30 sq. cm*kw*key.

For example, in a set (module) there are 2 keys (they can be seen, they stick out of the board, see on the left in the figure); modules with keys on the radiator (on the right in the figure) are more expensive and are designed for a certain, as a rule, not very high power. There is no cooler, the power needed is 1.5 kW. So, you need a radiator from 150 sq. see In addition to it, installation kits for keys: insulating heat-conducting gaskets and accessories for mounting screws - insulating cups and washers. If the module has thermal protection (some other wick will stick out between the keys - a thermal sensor), then a little thermal paste to stick it to the radiator. Wires - of course, see below.

From UPS (UPS)

An inverter 12V DC/220 V AC 50 Hz, to which you can connect any devices within the allowable power, is made from a computer UPS quite simply: regular wires to “your” battery are replaced with long ones with clips for the car battery terminals. The cross section of the wires is calculated based on the allowable current density of 20-25 A / sq. mm, see also below. But because of a non-standard battery, problems may arise - with it, but it is more expensive and more necessary than a converter.

The UPS also uses lead-acid batteries. Today, this is the only widely available secondary chemical power supply capable of regularly delivering high currents (extra currents) without being completely “killed” in 10-15 charge-discharge cycles. In aviation, silver-zinc batteries are used, which are even more powerful, but they are terribly expensive, they are not widely used, and their resource is negligible by household standards - approx. 150 cycles.

The discharge of acid batteries is clearly monitored by the voltage on the bank, and the UPS controller will not allow the "foreign" battery to be discharged beyond measure. But in regular UPS batteries, the electrolyte is gel, and in car batteries it is liquid. The charge regimes in both cases are significantly different: such currents cannot be passed through the gel as through a liquid, and in a liquid electrolyte with a too low charge current, the ion mobility will be low and not all of them will return to their places in the electrodes. As a result, the UPS will chronically undercharge the auto battery, it will soon become sulphated and become completely unusable. Therefore, a battery charger is needed in the kit for the inverter on the UPS. You can make it yourself, but that's another topic.

Battery and power

The suitability of the converter for a particular purpose also depends on the battery. The step-up voltage inverter does not take energy for consumers from the "dark matter" of the Universe, black holes, the holy spirit, or from somewhere else just like that. Only - from the battery. And from it he will take the power given to consumers, divided by the efficiency of the converter itself.

If you see a branded inverter “6800W” or more on the case, believe your eyes. Modern electronics makes it possible to place even more powerful devices in the volume of a cigarette pack. But, let's say we need a load power of 1000 W, and we have a regular 12 V 60 A / h car battery at our disposal. The typical inverter efficiency is 0.8. So, from the battery, he will take approx. 100 A. For such a current, wires with a cross section of 5 square meters are also needed. mm (see above), but this is not the main thing here.

Motorists know: the starter drove for 20 minutes - buy a new battery. True, in new machines there are time limits for its operation, so perhaps they don’t know. And not everyone knows for sure that the starter of a passenger car, having untwisted, takes a current of approx. 75 A (within 0.1-0.2 s at startup - up to 600 A). The simplest calculation - and it turns out that if there is no automation in the inverter that limits the discharge of the battery, then ours will sit down completely in 15 minutes. So choose or design your converter taking into account the capabilities of the available battery.

Note: this implies a huge advantage of 12/220 V converters based on computer UPSs - their controller will not allow the battery to completely drain.

The resource of acid batteries does not noticeably decrease if they are discharged with a 2-hour current (12 A for 60 A / h, 24 A for 120 A / h and 42 A for 210 A / h). Taking into account the conversion efficiency, this gives the permissible continuous load power in approx. 120W, 230W and 400W resp. For 10 min. load (for example, for powering a power tool), it can be increased by a factor of 2.5, but after that the ABA must rest for at least 20 minutes.

In general, the result is not entirely bad. From a conventional household power tool, only a grinder can take 1000-1300 watts. The rest, as a rule, cost up to 400 W, and screwdrivers up to 250 W. The refrigerator from the battery 12 V 60 A / h through the inverter will work for 1.5-5 hours; enough to take the necessary action. Therefore, it makes sense to make a 1 kW converter for a 60 A / h battery.

What will be the output?

In order to reduce the weight and size of the device, voltage converters, with rare exceptions (see below), operate at elevated frequencies from hundreds of Hz to units and tens of kHz. No consumer will accept a current of this frequency, and the loss of its energy in ordinary wiring will be huge. Therefore, inverters 12-200 are built for the output voltage next. types:

• Constant rectified 220 V (220V AC). Suitable for powering phone chargers, most power supplies (IP) tablets, incandescent lamps, fluorescent housekeepers and LED. For power from 150-250 W, they are perfect for hand power tools: the power it consumes DC decreases slightly, and the torque increases. Not suitable for switching power supplies (UPS) of TVs, computers, laptops, microwave ovens, etc. with a power of more than 40-50 W: in such there must be a so-called. starting node, for normal operation of which the mains voltage must periodically pass through zero. Unsuitable and dangerous for devices with power transformers on iron and AC motors: stationary power tools, refrigerators, air conditioners, most Hi-Fi audio, food processors, some vacuum cleaners, coffee makers, coffee grinders and microwaves (for the latter - due to the presence of a rotation motor table).
• Modified sine wave (see below) - suitable for all consumers, except for Hi-Fi audio with a UPS, other devices with a UPS from 40-50 W (see above) and often local security systems, home weather stations, etc. with sensitive analog sensors.
• Pure sinusoidal - suitable without restrictions, except for power, for any consumer of electricity.

Sine or pseudosine?

In order to increase efficiency, voltage conversion is carried out not only at higher frequencies, but also with multipolar pulses. However, it is impossible to power many consumer devices with a sequence of bipolar rectangular pulses (the so-called meander): large surges at the meander fronts with at least a little reactive load will lead to large energy losses and can cause a consumer malfunction. However, it is also impossible to design a converter for a sinusoidal current - the efficiency will not exceed approx. 0.6.

A quiet but significant revolution in this industry occurred when microcircuits were developed specifically for voltage inverters, forming the so-called. modified sinusoid (on the left in the figure), although it would be more correct to call it pseudo-, meta-, quasi-, etc. sinusoid. The current form of the modified sinusoid is stepped, and the pulse fronts are tightened (meander fronts are often not visible on the screen of a cathode-ray oscilloscope). Thanks to this, consumers with iron-based transformers or noticeable reactivity (asynchronous electric motors) “understand” the pseudosine wave “as real” and work as if nothing had happened; Hi-Fi audio with a network transformer on iron can be powered by a modified sine wave. In addition, a modified sinusoid may be sufficient simple ways smooth to “almost real”, the differences from the clean one on the oscilloscope are barely noticeable; "Pure sine" type converters are not much more expensive than conventional ones, on the right in fig.

However, it is undesirable to start devices with capricious analog nodes and UPS from a modified sinusoid. The latter is highly undesirable. The fact is that the average area of ​​the modified sinusoid is not a pure zero voltage. The UPS startup node from the modified sine wave does not work clearly and the entire UPS may not exit the startup mode to the working one. The user sees this at first as ugly glitches, and then smoke comes out of the device, as in a joke. Therefore, the devices in the UPS must be powered by Pure Sine inverters.

We make the inverter ourselves

So, while it is clear that it is best to make an inverter for an output of 220 V 50 Hz, although we will also remember about the AC output. In the first case, you will need a frequency meter to control the frequency: the norms for fluctuations in the frequency of the power supply network are 48-53 Hz. AC electric motors are especially sensitive to its deviations: when the frequency of the supply voltage reaches the tolerance limits, they heat up and “leave” the rated speed. The latter is very dangerous for refrigerators and air conditioners; they can permanently fail due to depressurization. But there is no need to buy, rent or beg for a time an accurate and multifunctional electronic frequency meter - we do not need its accuracy. Either an electromechanical resonant frequency meter (pos. 1 in the figure), or a pointer of any system, pos. 2:

Both are inexpensive, sold on the Internet, and in big cities in electrical special stores. An old resonant frequency meter can be found on the iron market, and one or the other, after setting up the inverter, is very suitable for controlling the mains frequency in the house - the meter does not respond to connecting them to the network.

50 Hz from computer

In most cases, 220 V 50 Hz power is required for not very powerful consumers, up to 250-350 watts. Then the basis of the 12/220 V 50 Hz converter can be a UPS from an old computer - unless, of course, this one is lying around in the trash or someone is selling it cheaply. The power delivered to the load will be approx. 0.7 of the nominal UPS. For example, if “250W” appears on its case, then devices up to 150-170 W can be connected fearlessly. Need more - you must first check on the load of incandescent lamps. Withstood 2 hours - it is able to give such power for a long time. How to make a 12V DC/220V AC 50Hz inverter from a computer power supply, see the video below.

Video: a simple 12-220 converter from a computer PSU

Keys

Let's say there is no computer UPS or more power is needed. Then importance acquires a choice of key elements: they must switch high currents with the lowest switching losses, be reliable and affordable. In this regard, bipolar transistors and thyristors in this field of application are surely becoming a thing of the past.

The second revolution in the inverter business is associated with the emergence of powerful field-effect transistors (“field workers”), the so-called. vertical structure. However, they turned the whole technique of power supply of low-power devices upside down: it is becoming increasingly difficult to find a transformer on iron in the “home appliances”.

The best of the high power field converters for voltage converters - insulated gate and induced channel (MOSFET), e.g. IFR3205, on the left in the figure:

Due to the negligible switching power, the efficiency of an inverter with a DC output on such transistors can reach 0.95, and with an AC output of 50 Hz 0.85-0.87. MOSFET analogues with built-in channel, e.g. IFRZ44, give lower efficiency, but are much cheaper. A pair of one or the other allows you to bring the power to the load up to approx. 600W; both can be paralleled without problems (on the right in the figure), which makes it possible to build inverters for power up to 3 kW.

Note: the switching loss power of switches with a built-in channel when operating on a significantly reactive load (for example, an asynchronous electric motor) can reach 1.5 W per switch. Keys with an induced channel are free from this shortcoming.

TL494

The third element that made it possible to bring voltage converters to their current state is the specialized TL494 microcircuit and its analogues. All of them are a pulse-width modulation (PWM) controller that generates a modified sine wave signal at the outputs. The outputs are bipolar, which allows you to control pairs of keys. The reference conversion frequency is set by one RC circuit, the parameters of which can be changed over a wide range.

When the permanence is enough

The range of 220 V DC current consumers is limited, but they just need an autonomous power supply not only in emergency situations. For example, when working with a power tool on the road or in the far corner of your own site. Or is it always present, say, at the emergency lighting of the entrance to the house, hallway, corridor, adjoining territory from solar battery, during the day recharging the battery. The third typical case is charging the phone on the go from the cigarette lighter. Here, the output power is needed very little, so that the inverter can be made with only 1 transistor according to the relaxation oscillator circuit, see next. video clip.

Video: single transistor boost converter

Already to power 2-3 LED bulbs, more power is needed. The efficiency of blocking generators when trying to "squeeze" it drops sharply, and you have to switch to circuits with separate timing elements or full internal inductive feedback, they are the most economical and contain the least number of components. In the first case, for switching one key, the self-induction EMF of one of the transformer windings is used together with a timing circuit. In the second, the step-up transformer itself is the frequency-setting element due to its own time constant; its value is determined mainly by the phenomenon of self-induction. Therefore, those and other inverters are sometimes called self-induction converters. Their efficiency, as a rule, is not higher than 0.6-0.65, but, firstly, the circuit is simple and does not require adjustment. Second, the output voltage is trapezoidal rather than square wave; "Demanding" consumers "understand" it as a modified sine wave. The disadvantage is that field keys in such converters are practically inapplicable, because often fail from voltage surges on the primary winding during switching.

An example of a circuit with external timing elements is given in pos. 1 fig.:

The author of the design failed to squeeze more than 11 watts out of it, but apparently he confused ferrite with carbonyl iron. In any case, the armored (cup) magnetic circuit in his own photo (see the figure on the right) is by no means ferrite. It looks more like an old carbonyl one, oxidized on the outside from time to time, see fig. on right. It is better to wind the transformer for this inverter on a ferrite ring with a ferrite cross-sectional area of ​​​​0.7-1.2 square meters. see. The primary winding should then contain 7 turns of wire with a copper diameter of 0.6-0.8 mm, and the secondary 57-58 turns of wire 0.3-0.32 mm. This is under straightening with doubling, see below. Under the "clean" 220 V - 230-235 turns of wire 0.2-0.25. In this case, this inverter, when replacing KT814 with KT818, will give power up to 25-30 W, which is enough for 3-4 LED lamps. When replacing KT814 with KT626, the load power will be approx. 15 W, but the efficiency will increase. In both cases, the key radiator is from 50 sq. cm.

At pos. 2 shows a diagram of an "antediluvian" converter 12-220 with separate feedback windings. It's not that archaic. First, the output voltage under load is a trapezoid with rounded fractures without spikes. It's even better than the modified sine wave. Secondly, this converter can be made without any alterations in the circuit for power up to 300-350 W and a frequency of 50 Hz, then a rectifier is not needed, you just need to put VT1 and VT2 on radiators from 250 sq. see each. Thirdly, it saves the battery: when overloaded, the conversion frequency drops, the output power decreases, and if you load it even more, the generation fails. That is, no automation is required to avoid overdischarging the battery.

The calculation procedure for this inverter is given in the scan in Fig.:

The key quantities in it are the conversion frequency and the working induction in the magnetic circuit. The conversion frequency is selected based on the material of the available core and the required power:

Type Magnetic core	Induction / conversion frequency
	Up to 50 W	50-100W	100-200W	200-350W
"Power" iron from power transformers with a thickness of 0.35-0.6 mm	0.5T/(50-1000)Hz	0.55T/(50-400)Hz	0.6T/(50-150)Hz	0.7T/(50-60)Hz
"Sound" iron from output transformers UMZCH with a thickness of 0.2-0.25 mm	0.4 T/(1000-3000)Hz	0.35T/(1000-2000)Hz	-	-
"Signal" iron from signal transformers with a thickness of 0.06-0.15 mm (not permalloy!)	0.3T/(2000-8000)Hz	0.25T/(2000-5000)Hz	-	-
Ferrite	0.15 T/(5-30) kHz	0.15 T/(5-30) kHz	0.15 T/(5-30) kHz	0.15 T/(5-30) kHz

Such an "omnivorous" ferrite is explained by the fact that its hysteresis loop is rectangular and the working induction is equal to the saturation induction. The decrease in comparison with typical calculated values ​​of induction in steel magnetic cores is caused by a sharp increase in switching losses of non-sinusoidal currents as it increases. Therefore, no more than 100-120 watts can be removed from the core of the power transformer of an old 270-watt “coffin” TV in this 50 Hz converter. But - on lack of fish and cancer fish.

Note: if there is a steel magnetic circuit with a deliberately oversized cross section, do not squeeze power out of it! Let it be better that the induction be less - the efficiency of the converter will increase, and the shape of the output voltage will improve.

straightening

It is better to rectify the output voltage of these inverters according to the scheme with parallel voltage doubling (pos. 3 in the figure with diagrams): the components for it will be cheaper, and the power losses on the non-sinusoidal current will be less than in the bridge. Capacitors must be taken "power", designed for high reactive power (with the designations PE or W). If you put "sound" without these letters, they can just explode.

50 Hz? It's very simple!

A simple 50 Hz inverter (pos. 4 of the figure above with diagrams) is an interesting design. Some types of typical power transformers have their own time constant close to 10 ms, i.e. half period 50 Hz. By correcting it with time-setting resistors, which will simultaneously limit the control current of the keys, you can immediately get a smoothed 50 Hz meander at the output without complex formation schemes. Transformers TP, CCI, TN for 50-120 W are suitable, but not all. You may need to change the resistor values ​​and / or connect 1-22 nF capacitors in parallel with them. If the conversion frequency is still far from 50 Hz, it is useless to disassemble and rewind the transformer: the magnetic core glued with ferromagnetic glue will fluff up, and the transformer parameters will deteriorate sharply.

This inverter is a country weekend converter. He will not land the car battery for the same reasons as the previous one. But it will be enough to light the house with a veranda LED lamps and a TV or a vibratory pump in the well. The conversion frequency of a well-established inverter when the load current changes from 0 to the maximum does not go beyond the technical standard for power supply networks.

The windings of the original transformer are bred as follows. In typical power transformers, there is an even number of secondary windings for 12 or 6 V. Two of them are “delayed”, and the rest are soldered in parallel into groups of an equal number of windings in each. Next, the groups are connected in series so that 2 half-windings of 12 V each are obtained, this will be a low-voltage (primary) winding with a midpoint. Of the remaining low-voltage windings, one is connected in series with a 220 V network, this will be a step-up winding. An additive to it is needed, because. the voltage drop on the keys of bipolar composite transistors, together with its losses in the transformer, can reach 2.5-3 V, and the output voltage will be underestimated. Additional winding will bring it to normal.

DC from chip

The efficiency of the described converters does not exceed 0.8, and the frequency, depending on the load current, noticeably floats. The maximum load power is less than 400 W, so it's time to think about modern circuit solutions.

A diagram of a simple converter 12 V DC / 220 V DC for 500-600 W is shown in the figure:

Its main purpose is to power hand-held power tools. Such a load is not demanding on the quality of the input voltage, so the keys are taken cheaper; IFRZ46, 48 are also suitable. The transformer is wound on a ferrite with a cross section of 2-2.5 square meters. cm; a power transformer core from a computer UPS is suitable. Primary winding - 2x5 turns of a bundle of 5-6 winding wires with a copper diameter of 0.7-0.8 mm (see below); secondary - 80 turns of the same wire. Establishment is not required, but there is no control over the discharge of the battery, so during operation you need to attach a multimeter to its terminals and do not forget to look at it (the same applies to all other home-made voltage inverters). If the voltage drops to 10.8 V (1.8 V per can) - stop, turn off! It dropped to 1.75 V per cell (10.5 V for the entire battery) - this is already sulfation!

How to wind a transformer on a ring

The quality characteristics of the inverter, in particular, its efficiency, are quite strongly affected by the stray field of its transformer. The fundamental solution for its reduction has long been known: the primary winding, which “pumps” the magnetic circuit with energy, is placed close to it; secondary above it in descending order of their power. But technology is such a thing that sometimes theoretical principles in specific designs have to be turned inside out. One of Murphy's laws says approx. so: if the piece of iron, well, it still doesn’t want to work as it should, try to do the opposite in it. This fully applies to a high-frequency transformer based on a ferrite annular magnetic core with windings made of relatively thick rigid wire. The voltage converter transformer is wound on a ferrite ring as follows:

• The magnetic circuit is isolated and, using a winding shuttle, a secondary step-up winding is wound on it, laying the turns as tightly as possible, pos. 1 in the figure:

• Tightly fit the "secondary" with adhesive tape, pos 2.
• Prepare 2 identical wire harnesses for the primary winding: wind the number of turns of half of the low-voltage winding with a thin unusable wire, remove it, measure the length, cut off the required number of winding wire segments with a margin and assemble them into bundles.
• Additionally, the secondary winding is isolated until a relatively flat surface is obtained.
• They wind the “primary” with 2 bundles at once, arranging the wires of the bundles with a tape and evenly distributing the turns over the core, pos. 3.
• The ends of the bundles are called and the beginning of one is connected to the end of the other, this will be the middle point of the winding.

Note: on electric circuit diagrams the beginning of the windings, if it matters, are indicated by a dot.

50 Hz smooth

A modified sine wave from a PWM controller is not the only way to get 50 Hz at the inverter output, suitable for connecting any household electricity consumers, and even that would not hurt to “smooth” it. The simplest of them is the good old iron transformer, it “strokes” well due to its electrical inertia. True, finding a magnetic circuit for more than 500 W is becoming increasingly difficult. Such an isolation transformer is switched on to the low-voltage output of the inverter, and a load is connected to its step-up winding. By the way, most computer UPSs are built according to this scheme, so they are quite suitable for this purpose. If you wind the transformer yourself, then it is calculated similarly to the power one, but with a trace. features:

• The initially determined value of the working induction is divided by 1.1 and is used in all further calculations. So it is necessary to take into account the so-called. form factor of non-sinusoidal voltage Kf; for a sinusoid, Kf \u003d 1.
• The step-up winding is first calculated as a 220 V mains winding for a given power (or determined by the parameters of the magnetic circuit and the value of the working induction). Then the found number of its turns is multiplied by 1.08 for powers up to 150 W, by 1.05 for powers of 150-400 W and by 1.02 for powers of 400-1300 W.
• Half of the low-voltage winding is calculated as secondary for a voltage of 14.5 V for bipolar switches or with a built-in channel and for 13.2 V for switches with an induced channel.

Examples of circuit solutions for converters 12-200 V 50 Hz with an isolating transformer are shown in the figure:

On the one on the left, the keys are controlled by the master oscillator on the so-called. "soft" multivibrator, it already generates a square wave in littered fronts and smoothed breaks, so additional measures smoothing is not required. The frequency instability of a soft multivibrator is higher than usual, so a potentiometer P is needed to adjust it. With the keys on the KT827, you can remove power up to 200 W (radiators - from 200 sq. cm without airflow). Keys on KP904 from old trash or IRFZ44 allow you to increase it to 350 W; single on IRF3205 up to 600 W, and paired on them up to 1000 W.

The inverter 12-220 V 50 Hz with a master generator on the TL494 (on the right in the figure) keeps the frequency iron in all imaginable unimaginable operating conditions. For more efficient smoothing of the pseudosinusoid, the so-called phenomenon is used. indifferent resonance, in which the phase ratios of currents and voltages in the oscillatory circuit become the same as in acute resonance, but their amplitudes do not noticeably increase. Technically, this is solved simply: a smoothing capacitor is connected to the step-up winding, the capacitance value of which is selected according to the best form of current (not voltage!) Under load. To control the current shape, a 0.1-0.5 Ohm resistor is included in the load circuit for a power of 0.03-0.1 of the nominal, to which an oscilloscope with a closed input is connected. The smoothing capacitance does not reduce the efficiency of the inverter, but should be used to adjust computer programs oscilloscope low-frequency simulation is impossible, because the input of the sound card that they use is not designed for an amplitude of 220x1.4 = 310 V! The keys and powers are the same as before. case.

A more advanced converter circuit 12-200 V 50 Hz is shown in Fig.:

It uses complex composite keys. To improve the quality of the output voltage, it uses the fact that the emitter of planar epitaxial bipolar transistors is doped much more strongly than the base and collector. When TL494 applies a closing potential, for example, to the VT3 base, its collector current will stop, but due to the absorption of the emitter space charge, it will slow down the blocking of T1 and the voltage surges from the self-induction EMF Tr will be absorbed by the circuits L1 and R11C5; they will “tilt” the fronts more. The output power of the inverter is determined by the overall power Tr, but not more than 600 W, because it is impossible to use paired powerful switches in this circuit - the spread in the gate charge of MOSFET transistors is quite significant and the switching of the keys will be fuzzy, which may even worsen the shape of the output voltage.

Inductor L1 is 5-6 turns of wire with a diameter of 2.4 mm or more over copper, wound on a piece of a ferrite rod with a diameter of 8-10 m and a length of 30-40 mm in increments of 3.5-4 mm. The magnetic circuit of the throttle must not be closed! Establishing a circuit is a rather painstaking task and requires considerable experience: you need to select L1, R11 and C5 according to the best shape of the output current under load, as in the previous one. case. On the other hand, Hi-Fi, powered by this converter, remains "Hi-Fi" to the most demanding ears.

Is it possible without a transformer?

Already a winding wire for a powerful 50 Hz transformer will cost a pretty penny. More or less magnetic circuits are available from “coffin” transformers up to 270 W overall, but in an inverter you cannot squeeze out more than 120-150 W from this, and the efficiency will be 0.7 at best, because. "Coffin" magnetic circuits are wound from a thick tape, in which eddy current losses are large at non-sinusoidal voltage on the windings. It is generally problematic to find an SL magnetic circuit from a thin tape capable of delivering more than 350 W at an induction of 0.7 T, it will cost a lot, and the entire converter will turn out to be huge and unbearable. UPS transformers are not designed for frequent continuous operation - they heat up and their magnetic circuits in inverters degrade pretty soon - the magnetic properties deteriorate greatly, the converter power drops. Is there a way out?

Yes, and such a solution is often used in proprietary converters. This is an electric bridge from keys on high-voltage power field-effect transistors with a breakdown voltage of 400 V and a drain current of more than 5 A. Suitable from the primary circuits of computer UPSs, and from old trash - KP904, etc.

The bridge is powered by a constant 220 V DC from a simple 12-220 inverter with rectification. The arms of the bridge open in pairs crosswise alternately, and the current in the load included in the diagonal of the bridge changes direction; control circuits of all keys are galvanically isolated. In industrial constructions, the keys are controlled from special ICs with optocoupler decoupling, but in amateur conditions, both can be replaced with an additional low-power inverter 12 V DC - 12 V 50 Hz, running on a small iron transformer, see fig. The magnetic circuit for it can be taken from a Chinese market low-power power transformer. Due to its electrical inertia, the quality of the output voltage is even better than the modified sine wave.

Very often there are situations when it is necessary to connect electronic device or the device in a place where there is no mains voltage of 220 volts. The easiest is to use rechargeable batteries, but their voltage is usually 12 volts. In order to convert 12 volts to 220 volts, inverters are used, another name is converters. So, an inverter is an electronic device that converts a low voltage DC into a variable value of 220 V.

The options for using the inverter are varied:

• Application to provide power supply, in case of an accident in the 220 volt network. Such a conversion system is installed in country house or industrial facilities.
• For the organization of complete autonomy from the power grid.
• During long journeys by car, bus, boat, plane.

The main difference between the devices used will be the power that can be connected as a load and electronic design.

Inverters differ in the construction scheme. The first devices were of a mechanical type until they were replaced by semiconductors, and modern ones have already become digital. According to the classification, the following main construction schemes are distinguished:

And also divided into single-phase and three-phase. By type of output voltage are:

• with a rectangular shape;
• with a stepped shape;
• with sinusoidal shape.

For devices that do not require a correct sine waveform, converters with a rectangular, trapezoidal, triangular output voltage can be used. The main advantage of such converters is their low price.

For equipment that requires reliable power, it is necessary to use inverters with the correct form of a sine wave. Such equipment is much more expensive, but their stability is higher.

Selecting a voltage converter

When choosing, first of all, you need to pay attention to power. The total power is calculated based on the load that is planned to be connected to the device, about 25-30 percent is added to the obtained value. This allows you to work in comfortable conditions, without overloading the equipment. An inverter with a power of up to 5000 W is usually used, but to provide almost all household needs, even 15,000 watts may not be enough. Portable device uses 200-800 watts. In addition to the rated power, there is the concept of peak power. This is the value that the inverter can withstand for a short time without adversely affecting its operation.

It is important to understand that the load power when a number of devices are turned on differs from the nominal one. These are devices such as a pump, refrigerator, washing machine, powerful vacuum cleaner. All of them consume peak power when turned on. At the same time, the TV, computer, lamp and tape recorder do not exceed the nominal value during operation. It should also be noted that power can be measured both in volt-amperes (VA) and watts (W). The relationship between these units of measurement is described by the expression 1W=1.6VA.

So, first of all, when choosing, we determine for what type of devices the current converter from 12 to 220 volts will be used. When operating indoors, we consider the possibility of installing batteries. They must connect parallel to each other, this will ensure the possibility of continuous operation in case of malfunctions in the industrial electrical network. For example, for an autonomous heating system.

Then we pay attention to the shape of the output signal. A pure sine wave indicates how often the voltage is applied and how smoothly it changes. This characteristic is very important for systems with active power - these are all devices using electric motors, compressors.

We pay attention to the options at will, it can be the implementation of automatic switching on and off, the function charger, over voltage protection, over temperature protection, etc.

How to make a voltage converter with your own hands

As an example, consider the conversion of an inverter from 12 to 220-3000W. With your own hands, with a little technical training, it will not be difficult to implement it. Several ways can be used to resolve this issue.

Fabrication using radio-electric circuits

An electronic part is assembled on a printed circuit board, then a case is made, on which everything is attached. The principle of operation of such converters is usually the same. A pulse-width modulation (PWM) controller is used to set the frequency and amplitude. The power part is assembled from powerful transistors mounted on radiators.

Consider an example using an oscillator whose output is used for timing. A specialized chip kr1211eu1 is used as a generator. As output transistors operating in the key mode, you can use 2SK2554 or analogues BUZ111SL, BUK9608-55, IRL2505. The advantage of such field-effect transistors is the low resistance of the open channel RDS (on), which allows the use of small-area radiators.

The chain r1, c1 sets the frequency of the generator, and r2, c2 is designed to start it. In this circuit, you can use any step-up transformer with secondary windings for 12 volts of the required power. Chip power carried out through a stabilizer, the output voltage of which is achieved due to the strong nonlinearity of the current-voltage characteristics of electronic components, consisting of r3, vd1, c3 with a stabilization voltage of 7-10 volts. Capacitor c6 is designed to reduce the effect of high-frequency noise.

Any type of load can be connected to such a device, the power of which will not exceed 2.6 kW. Thus, having understood the operation of the circuit, you can not only assemble it, but also carry out repairs if necessary.

One more point needs to be noted: self assembly you need to pay attention to the wires connected to the power source from the inverter. The more powerful the device is, the larger the cross section of the wire should be. The main characteristic that helps to calculate the cross section of the wire is the maximum permissible continuous load (by current). This is the value of the current that the wire can pass through itself for a long time without heating. In our case, for 3 kW, it is recommended to use a wire with a cross section of 2.5 squares. Choose copper as the material.

Uninterruptible power supply application

They are different in power, so there should not be any problems with the selection. This is a complete inverter. For example, this type of device can be used in a car by connecting a car battery to the regular place of the battery.

Using ready-made nodes and blocks

In electronics stores, you can find kits that allow you to get a finished device. The kit usually includes a factory printed circuit board, the necessary radio components, heatsinks, assembly instructions and settings. The finished 12 220 volt inverter will have to be placed in the case after assembly. The case must be selected based not only on aesthetic considerations, but also on the part of the correct organization of cooling of active parts.

Thus, it is possible to independently manufacture voltage converters from 12 to 220 V., performed correctly, will work no worse than industrial manufacturing options.