Inverter converter 12 to 220 circuit. High voltage and more. Operating principle of the inverter

When it is necessary to create mains voltage in a car, special 12-220 converters are usually used. There are inexpensive standard inverters on sale for about 20-30 dollars. However, the maximum power of such devices is, at best, about 300 watts. In some cases, this power may not be 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 this, you can get any value of the input voltage. For example, the power of a 400 Watt inverter will increase to 600 Watts.

To increase power at home, experts recommend using a simple method. It will be necessary to replace the high-power bipolar switches with IRF 3205.

An inverter is used for operation, to which it is possible to connect 4 pairs of output transistors. Therefore, the device, after carrying out the necessary work, will be able to produce a power of about 1300 watts. If you buy a ready-made inverter with such parameters, 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 a 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 to supply power, the inverter is equipped with a remote control circuit.

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

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

Then the rings are wrapped on top with fiberglass (the cost in the store is no more than $1). It is quite 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 you need 2x5 turns of wire, 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 are used for each arm. The process is presented more clearly in the following photographs.

The tourniquet is stretched, and 5 turns are evenly wound on both arms, stretching them across the entire 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 solder location will 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 need to be as careful as possible and follow all safety precautions. It is worth remembering that high voltage is dangerous. Installation of the device is carried out only with the power turned off.

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

When the inverter assembly is completed, you can begin testing it. The device is connected to a battery; for starters, a battery with a voltage of 12 V from an uninterruptible power supply will do. 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 be lit before or during work.

After this, you can proceed to checking the field keys for heat generation. With a correctly assembled circuit, it should be practically zero. If there is no input load, and the transistors overheat, then you need to look for a non-working component in the device.

If the testing is successful, you can install the transistors on one common heat sink. For this purpose, special insulating gaskets are used.

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

To connect household devices to the car’s on-board electrical system, you need an inverter that can increase the voltage from 12 V to 220 V. There are sufficient quantities of them on store shelves, but their price is not encouraging. For those who are a little familiar with electrical engineering, it is possible to assemble a 12-220 volt voltage converter with your own hands. We will analyze two simple schemes.

Converters and their types

There are three types of 12-220 V converters. The first is from 12 V to 220 V. Such inverters are popular among motorists: through them you can connect standard devices - TVs, vacuum cleaners, etc. Reverse conversion - from 220 V to 12 - is required infrequently, usually in rooms with severe operating conditions (high humidity) to ensure electrical safety. For example, in steam rooms, swimming pools or baths. In order not to take risks, the standard voltage of 220 V is reduced to 12, using appropriate equipment.

The third option is, rather, a stabilizer based on two converters. First, the standard 220 V is converted to 12 V, then back to 220 V. This double conversion allows you to have an ideal sine wave at the output. Such devices are necessary for the normal operation of most electronically controlled household appliances. In any case, during installation it is strongly recommended to power it through just such a converter - its electronics are very sensitive to the quality of power, and replacing the control board costs about half the boiler.

Pulse converter 12-220V 300 W

This circuit is simple, the parts are available, most of them can be removed from a computer power supply or purchased at any radio store. The advantage of the circuit is its ease of implementation, the disadvantage is the non-ideal sine wave at the output and the frequency is higher than the standard 50 Hz. That is, devices that require power supply cannot be connected to this converter. You can directly connect not particularly sensitive devices to the output - incandescent lamps, iron, soldering iron, phone charger, etc.

The presented circuit in normal mode produces 1.5 A or pulls a load of 300 W, at a maximum of 2.5 A, but in this mode the transistors will noticeably heat up.

The circuit was built on the popular TLT494 PWM controller. Field-effect transistors Q1 Q2 should be placed on radiators, preferably separate ones. When installing on one radiator, place an insulating gasket under the transistors. Instead of the IRFZ244 indicated in the diagram, you can use IRFZ46 or RFZ48, which are similar in characteristics.

The frequency in this 12 V to 220 V converter is set by resistor R1 and capacitor C2. The values may differ slightly from those shown in the diagram. If you have an old non-working UPS for your computer, and it contains a working output transformer, you can put it in the circuit. If the transformer is not working, remove the ferrite ring from it and wind the windings with copper wire with a diameter of 0.6 mm. First, the primary winding is wound - 10 turns with the output from the middle, then, on top - 80 turns of the secondary.

As already said, such a 12-220 V voltage converter can only work with a load that is insensitive to power quality. To be able to connect more demanding devices, a rectifier is installed at the output, the output voltage of which is close to normal (diagram below).

The circuit shows high-frequency diodes of the HER307 type, but they can be replaced with the FR207 or FR107 series. It is advisable to select containers of the specified size.

Inverter on a chip

This 12-220 V voltage converter is assembled on the basis of a specialized KR1211EU1 microcircuit. This is a generator of pulses, which are removed from outputs 6 and 4. The pulses are antiphase, with a short time interval between them - to prevent the simultaneous opening of both keys. The microcircuit is powered by a voltage of 9.5 V, which is set by a parametric stabilizer on a D814V zener diode.

Also in the circuit there are two high-power field-effect transistors - IRL2505 (VT1 and VT2). They have a very low open resistance of the output channel - about 0.008 Ohms, which is comparable to the resistance of a mechanical key. Permissible direct current is up to 104 A, pulsed current is up to 360 A. Such characteristics actually make it possible to obtain 220 V with a load of up to 400 W. Transistors must be installed on radiators (with a power of up to 200 W it is possible without them).

The pulse frequency depends on the parameters of resistor R1 and capacitor C1; capacitor C6 is installed at the output to suppress high-frequency surges.

It is better to take a ready-made transformer. In the circuit, it is turned on in reverse - the low-voltage secondary winding serves as the primary, and the voltage is removed from the high-voltage secondary.

Possible replacements in the element base:

The D814V zener diode indicated in the circuit can be replaced with any one that produces 8-10 V. For example, KS 182, KS 191, KS 210.
If there are no capacitors C4 and C5 of type K50-35 at 1000 μF, you can take four 5000 μF or 4700 μF and connect them in parallel,
Instead of an imported capacitor C3 220m, you can supply a domestic one of any type with a capacity of 100-500 µF and a voltage of at least 10 V.
Transformer - any with a power from 10 W to 1000 W, but its power must be at least twice the planned load.

When installing circuits connecting a transformer, transistors and connecting to a 12 V source, it is necessary to use large cross-section wires - the current here can reach high values (with a power of 400 W up to 40 A).

Inverter with pure sine wave output

The circuits of daytime converters are complex even for experienced radio amateurs, so making them yourself is not at all easy. An example of the simplest circuit is below.

In this case, it is easier to assemble such a converter from ready-made boards. How - watch the video.

The next video shows how to assemble a 220 volt converter with pure sine wave. Only the input voltage is not 12 V, but 24 V.

And this video just tells you how you can change the input voltage, but still get the required 220 V at the output.

12-220 Volt inverters are needed to power 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 direct voltage of 12 V into an alternating voltage of 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 a 12-220 car inverter while traveling. Any household appliance can work even in field conditions. But the maximum permissible 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 run out. Types of loads by current consumption:

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

If you know exactly what load you will connect to the inverter, then calculating the maximum power will not be difficult. 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 reserve is quite enough. Therefore, to fully meet the needs, you need an inverter with a power of 375 W. But you won't find one like this on 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 12-220 Volt voltage inverter is an uninterruptible power supply used in computer technology. But they have one big drawback - low power, the battery does not last long. And if the device is used in everyday life in conjunction with a mini-power plant (even a wind-powered one), then stable power is guaranteed. Typically, inverters can be found in the following designs:

Security alarms.
Heating boilers.
Pumping stations.
Computer servers and other systems.

In other words, they are used where a constant supply of 220 Volts is required. Household voltage stabilizers are nothing more than inverters. Only in them is the alternating voltage converted to constant, stabilized, after which it rises again to 220 Volts. Moreover, with the help of electrical semiconductor switches and a PWM modulator, it is possible to achieve an almost ideal sinusoid.

Features of the design

Inverters 12-220 Volts are used quite widely. Ordinary motorists use them as a power source on long trips. You can simply turn on an electric razor, hair dryer, TV, even boil a kettle. True, the battery will drain quickly. 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. The device can be operated even in severe frost. But for hot weather it is necessary to provide additional cooling, otherwise the transistors will fail. A simple cooler from a personal computer just needs to be installed on a radiator for cooling semiconductor power transistors.

The simplest homemade inverter

Almost all commercially available inverters operate using high frequency current. Classic circuits, which were made on the basis of transformers, are completely forgotten, they were replaced by pulse designs.

Based on one K561TM2 microcircuit, consisting of two D-flip-flops, it is possible to make the simplest master path for an inverter. The circuit consists of a master oscillator, the role of which is played by DD1, as well as a frequency divider made on the trigger DD1.2.

Power transistors like KT827 or KT819 are used for voltage conversion. Field effect transistors of the IRFZ44 type show very good results. With the help of a master generator, a sinusoid is generated, which is necessary for the normal operation of the structure.

Features of the inverter

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

The output sinusoid is far from ideal. This is a huge drawback of such a scheme. To produce an increase in power, it is necessary to use more expensive and efficient types of transistors. Note the electrolytic capacitor that is connected to the output. It should be designed for a minimum voltage of 250 V. It will be better if this value is higher than 300 V.

Devices based on modern components

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 based on the KR121EU1 logical element, by analogy as in the case discussed above, and field-effect transistors IRL2505 also work well.

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

When the channels in the transistors are open, their resistance is only 0.008 Ohm - this is very little. Therefore, transistors with low power 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

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

Transformer.
Semiconductor power switches.
Radiator.
Passive elements.
Residual current devices, fuses.

Such an inverter 12 to 220 will produce a pure sine wave at the output, since it is manufactured at a modern facility. The cost of ready-made blocks is quite high. The lowest-power one will cost no less than 300-350 rubles, and that’s the wholesale price. The higher the power of the device, the higher its cost.

But before using such devices, you need to find a suitable housing. The board must be mounted in such a way that the internal space is well cooled. It is advisable to do 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.

A second life for uninterruptible power supply!

If you have an “extra” uninterruptible power supply whose battery is completely dead, you can still revive it. To do this you will need to make some small changes:

Remove the old battery.
Solder new wires to connect to the 12 Volt battery.
At the edges of the wires, install terminals for connecting to the car battery. If the device will be used in a car, it can be powered 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 household appliances to an uninterruptible power supply, you need to make sockets. The easiest way is to make a carrier from an old surge protector and a piece of wire with a plug, which will include all the equipment.

Design features based on uninterruptible power supply

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

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

Homemade powerful inverter

To make a 12 V 220 3000 W inverter with your own hands, you will need knowledge of the basics of electrical engineering and 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 several expensive elements. They are listed below:

PWM modulator. Necessary for the operation of semiconductor switches. With its help, the operating frequency 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.
Semiconductor transistors operating as power switches allow not only amplification of the signal, but also switching. They open and close, and when paired with a PWM modulator, they create an almost pure sine wave.
Aluminum radiators with large surface area. The higher the power of the device, the larger the radiator area required.
Foil material on which all elements are mounted. If desired, of course, you can perform wall-mounted installation, but it will take up too much space. You can make such a homemade 12-220 inverter with your own hands in a few minutes, but it will be unsafe to use if you do not take measures.
Passive elements - resistors, capacitors.
Connecting wires.

When manufacturing a device, several electromagnetic relays may also be required for switching. By the way, you can decide 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 cannot cope with this task.

Ready-made inverters

If you do not want to make a 12 V 220 3000 W 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 is too high. You can buy the cheapest one, whose power barely reaches 50 W, for 800-1000 rubles. And it will be 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 12-220 V inverter will cost 3000-5000 rubles. But it all depends on the manufacturer. High-quality, multifunctional devices produced 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 of a personal computer.

I have never seen an inverter circuit simpler than this one. To repeat, you will need a minimum of parts - no more than 10 pieces. To obtain an output voltage of 220 volts, we need one 1.5 volt AA battery.

Inverters are needed where it is not possible to connect to a 220 volt network. Inverters are divided into two types: some have a sinusoidal output voltage with a frequency of 50 Hz and are suitable for powering almost any load. Other modified ones have a high output frequency, about 500-10000 Hz and not always a sinusoidal waveform.
Inverters with a sine wave frequency of 50 Hz are expensive, since a large transformer or simulation electronics unit is needed to generate a 50 Hz sinusoidal pulse.
The simplest inverter that we will make belongs to the second group. And it is suitable for powering various switching power supplies, such as a phone charger, an energy-saving light bulb - fluorescent or LED.

Required Components

Transformer 220V – 6V. You can tear it out of an old tape recorder, receiver, etc. or buy here -
AA battery case - 1 -
Switch - 1 -
Printed circuit board - 1 -
BC547 transistor (domestic analogue of KT3102, KT315) - 1 -
BD140 Transistor with radiator (domestic analogue of KT814, KT816) – 1 -
Capacitor 0.1 µF – 1-
30 kOhm resistor - 1 -
Tools:
Soldering iron, if you don’t have it, take it here -

Scheme

Let's start getting acquainted with the inverter with a diagram. This is an ordinary multivibrator based on a composite transistor. The result is a generator at the output of which there is a step-up transformer.
Let's put together a diagram. The board is prototyping, with a large number of holes. We insert the parts and solder them with jumpers according to the diagram.

Checking work

If all components of the circuit are in good working order, and the circuit is assembled without errors, then the inverter starts working immediately and does not need adjustment.

We connect an energy-saving lamp to the inverter output. Insert the battery and close the switch. The light came on.

Of course, its brightness is lower than when powered from the mains, but the fact that it operates from a 1.5 volt element is a breakthrough!
Naturally, as everywhere else, the law of conservation of energy applies here. Based on this, it follows that the current in the battery circuit will be several times higher than in the light bulb circuit. In general, the battery must be alkaline, then there is a chance that it will work a little longer.

When installing and working with the inverter, be especially careful, the voltage of 220 volts is dangerous to life. And, believe me, a 1.5 volt battery is enough to give a person a fatal electric shock, and even cause cardiac arrest. As you know, to do this it is enough to pass about 100 mA through a person, which this inverter is quite capable of.

To connect an electrical device to your home network, one surge protector or uninterruptible power supply unit is enough. These devices will protect equipment from power surges. But what to do if there is a strong voltage drop in the network, or if the power network requires the use of higher or lower voltage. For such situations, you can assemble a homemade electrical current converter from 12V to 220V. To do this, you need to understand the basic principles of operation of this device.

A converter is a device that can increase or decrease the voltage of an electrical circuit. This way you can change the circuit voltage from 220V to 380V, and vice versa. Let's consider the principle of constructing a converter from 12V to 220V.

These devices can be divided into several classes/types, depending on their functional purpose:

Rectifiers. They work on the principle of converting alternating current to direct current.
Inverters. They work in reverse order, converting direct current into alternating current.
Frequency converters. They change the frequency characteristics of the current in the circuit.
Voltage converters. Change the voltage up or down. Among them are:
- Switching power supplies.
- Uninterruptible power supplies (UPS).
- Voltage transformers.

Also, all devices are divided into two groups - according to the control principle:

Managed.
Uncontrollable.

Common Schemes

To convert voltage from one level to another, pulse converters with installed inductive energy storage devices are used. Based on this, three types of conversion schemes are distinguished:

Inverting.
Raising.
Downgrades.

All of the following circuits use electrical components:

Main switching component.
Power supply.
A filter capacitor that is connected in parallel with the load resistance.
Inductive energy storage (choke, inductor).
Diode for blocking.

Combining these elements in a certain sequence allows you to build any of the above schemes.

Simple pulse converter

The most basic converter can be assembled from unnecessary parts from an old computer system unit. A significant drawback of this circuit is that the 220V output voltage is far from ideal in its sine wave shape and has a frequency exceeding the standard 50 Hz. It is not recommended to connect sensitive electronics to such a device.

This scheme uses an interesting technical solution. To connect equipment with switching power supplies (for example, a laptop) to the converter, rectifiers with smoothing capacitors are used at the output of the device. The only negative is that the adapter will only work if the polarity of the output voltage of the socket matches the voltage of the rectifier built into the adapter.

For simple energy consumers, the connection can be made directly to the output of transformer TR1. Let's consider the main components of this scheme:

Resistor R1 and capacitor C2 - set the operating frequency of the converter.
PWM controller TL494. The basis of the whole scheme.
Power field effect transistors Q1 and Q2 are used for greater efficiency. Placed on aluminum radiators.
IRFZ44 transistors can be replaced with IRFZ46 or IRFZ48 with similar characteristics.
Diodes D1 and D2 can also be replaced with FR107, FR207.

If the circuit involves the use of one common radiator, it is necessary to install transistors through insulating spacers. According to the scheme, the output choke is wound onto a ferrite ring from the choke, which is also removed from the computer power supply. The primary winding is made of 0.6 mm wire. It should have 10 turns with a tap from the middle. A secondary winding consisting of 80 turns is wound on top of it. The output transformer can also be removed from an unnecessary UPS.

The scheme is very simple. When assembled correctly, it starts working immediately and does not require fine tuning. It will be able to supply a current of up to 2.5 A to the load, but the optimal operating mode will be a current of no more than 1.5 A - and this is more than 300 W of power.

INTERESTING: In a store, a similar converter costs around 3-4 thousand rubles.

Converter circuit with AC output

This scheme is also known to radio amateurs of the USSR. However, this does not make it ineffective. On the contrary, it has proven itself very well, and its main advantage is the receipt of stable alternating current with a voltage of 220V and a frequency of 50 Hz.

The K561TM2 microcircuit, which is a dual-type D-trigger, acts as an oscillation generator. This element can be replaced with a foreign analogue CD4013.

The converter itself has two power arms, built on KT827A bipolar transistors. They have one significant drawback compared to new field-effect transistors - these components become very hot when open, which is due to high resistance values. The converter operates at low frequency, so a powerful steel core is used in the transformer.

This circuit uses an old TC-180 network transformer. It, like other inverters based on simple PWM circuits, produces a significantly different sinusoidal voltage waveform. However, this drawback is slightly mitigated by the high inductance of the transformer windings and the output capacitor C7.

IMPORTANT: Sometimes the transformer may produce a noticeable hum during operation. This indicates a problem with the circuit.

Simple transistor inverter

This scheme is not very different from those presented above. The main difference is the use of a rectangular pulse generator built on bipolar transistors.

The main advantage of this circuit is the ability of the converter to remain operational even with a very low battery. In this case, the input voltage range can be from 3.5 to 18V. But there are also disadvantages of such an inverter. Since the circuit does not have any stabilizer at the output, voltage drops are possible, for example, when the battery is discharged. Since this circuit is also low-frequency, a transformer is selected for it, similar to that installed in the inverter based on the K561TM2 microcircuit.

Improvements to inverter circuits

The above diagrams cannot be compared with factory products. They are simple and poorly functional. To improve their characteristics, you can resort to fairly simple modifications that increase the performance of the device.

ATTENTION: Any electrical and electronic installation is carried out with the power source disconnected. Before checking the circuit, test all inputs and outputs with a multimeter - this will avoid unpleasant consequences.

Increased power output

The circuits discussed above are based on the same principle - the primary winding of the transformer is connected through a key component (arm output transistor). It is connected to the input of the power source for a time specified by the frequency and duty cycle of the master oscillator. In this case, magnetic field pulses are generated, exciting common-mode pulses in the secondary winding of the transformer with a voltage equal to the voltage in the primary winding multiplied by the ratio of the number of turns in the windings.

Accordingly, current passes through the output transistor. In this case, it is equal to the load current multiplied by the inverse ratio of turns (transformation ratio). It turns out that the maximum current that a transistor can pass through itself sets the maximum power of the converter.

Two methods are used to increase output power:

Installing a more powerful transistor.
Using parallel connection of several low-power transistors in one arm.

For a homemade converter, it is preferable to use the second method, since it allows you to maintain the functionality of the device if one of the transistors fails. In addition, such transistors cost less money.

In the absence of internal overload protection, this method significantly increases the survivability of the converter. It also reduces the overall heating of internal components when operating at the same load.

Automatic shutdown when battery is low

These schemes have one significant drawback. They do not provide a component that can automatically turn off the converter in the event of a critical voltage drop. But solving this problem is quite simple. It is enough to install a regular car relay as a circuit breaker.

The relay has its own critical voltage at which its contacts close. By selecting the resistance of resistor R1, which will be approximately 10% of the resistance of the relay winding, the moment of contact breaking is adjusted. This option is demonstrated in the diagram.

This option is quite primitive. To stabilize the operation, the converter is supplemented with a simple control circuit that maintains the shutdown threshold much better and more accurately. The response threshold setting in this case is calculated by selecting resistor R3.

Inverter fault detection

The circuits described above often have two specific defects:

No voltage at the transformer output.
Low voltage at the transformer output.

Let's look at ways to diagnose these faults:

Failure of all arms of the converter or failure of the PWM generator. You can check the breakdown using a diode. A working PWM will show ripple on the diode when it is connected to the gates of the transistors. It is also worth checking the integrity of the transformer winding “for an open” in the presence of a control signal.
A strong drop in voltage is the main sign that one power arm has stopped working. Finding a breakdown is not difficult. A failed transistor will have a cold heatsink. To repair, you will need to replace the inverter key.

Conclusion

Making a converter at home is not difficult. The main thing is to follow the sequence of connections and select the components correctly. It is best to assemble a converter with built-in protection mechanisms that will protect the device when the battery voltage drops.