Very often, car enthusiasts use their vehicle as a motor home, going camping or fishing for several days. Of course, in such conditions there is a shortage of urban amenities such as a kettle, laptop, camera, refrigerator and other electrical appliances that are powered from a 220V network. Of course, you can “power” it directly from the car’s electrical network, but this will require a bunch of different adapters for each individual device, and you can’t charge a laptop or video camera using this method. You can try to buy special electrical appliances that operate from a cigarette lighter, but this is a waste of money, since you cannot use such modernized devices at home.
The best option is inexpensive and compact 12/220V car inverters, which are also called converters. The principle of their operation is extremely simple. Using a current generator, the devices convert the DC voltage of the battery (12V for passenger cars and 24V for trucks) into alternating voltage, which is 220V at a frequency of 50 Hz. This is the voltage used to operate common household devices plugged into an outlet in your home.
To choose an inverter and not harm the machine, just use a few recommendations and familiarize yourself with the following characteristics.
Inverter power
When purchasing an inverter, you first need to pay attention to the power of the device. To do this, determine what power you plan to use the devices with. The fact is that you need to buy a converter whose power will be slightly greater than that of electrical appliances. You can find this information in the technical data sheet of the inverter. If you find a marking of 300%, this will mean that the power of the device is 3 times greater than that of a kettle or laptop. In fact, 30-50% will be enough. Thus, if you use a video camera with a power of 500 W, then you need to buy an inverter for 650-750 W.
Healthy! The more powerful the inverter, the more different devices you can connect to it.
However, it is worth considering that a car’s generator cannot always produce the required current. For example, for a VAZ 2110, a 12/220V 2000W car inverter may not be suitable, since in this case the generator power will not be enough and the car will start idling, actively powered by the battery. In this case, the inverter will operate at 175A, and the car's generator can only provide 80A, and then only at 5000 rpm, which is fraught with expensive fuel consumption. Agree, it is not advisable to buy such a converter, so first it is better to evaluate the capabilities of the car so as not to drain its battery.
It is also worth considering that most often the inverter outputs much less watts than stated in the device data sheet. For example, a 300-watt converter, in fact, can only provide 190-200 volts. A 600-watt device will also most likely produce no more than 200-215 volts. But the 12/220V 2000W car inverter will not deceive you. Therefore, it is better to check the output voltage of the device using a voltmeter.
Important! If you decide to connect the inverter directly from the battery, make sure that the inverter is turned off. If you start the car while the inverter is on, this may cause the on-board system to fail.
It is difficult to say what power is optimal for using an inverter, since it directly depends on the characteristics of your car and the power of the devices. And if you are looking for a converter for a truck or large vehicle, do not forget that in this case you will already need a 24/220 V car inverter.
Current consumption
Different inverter models may or may not draw current when they are turned off. If there is constant consumption, you must turn off the device manually by removing the terminals or pressing the corresponding “Off” button.
Pulse shape
Another important parameter when choosing an inverter is its pulse shape, which the device produces after conversion. In almost all inexpensive Chinese-made models, the outstanding signal is modified. This is important, since a fan, laptop, pump and any other device equipped with transformer power supplies can simply burn out from such a current.
Therefore, if you plan to use such “serious” equipment, it is better to buy a 12/220V pure sine car inverter. This must be indicated in the passport of such a converter. This voltage is much more stable and will not damage expensive equipment, however, such units also cost a lot, from 4,500 rubles, while a regular unit can be purchased for 1,500 rubles.
Temperature protection
When buying a converter, almost every motorist wants to use it both in the cold season and in the hot summer. Therefore, if this parameter is also important for you, be sure to check this point with the seller, or better yet, read the instructions and characteristics of the device. Most often, manufacturers indicate a range from -5 to +40 degrees, but there are also more resistant models or, conversely, inverters that do not tolerate temperature changes well.
In addition, a high-quality inverter will definitely be equipped with a system that protects against:
- incorrect connection of electrical appliances;
- non-compliance with polarity;
- short circuits;
- input voltage too low or high;
- overheating;
- output overloads.
Automotive inverter manufacturers
Today, the market offers a fairly wide selection of automotive inverters of varying power and cost. The most popular models today are:
- AcmePower 12/220V 1000W. Externally, the device does not cause any complaints; the manufacturer paid a lot of attention to the design, as well as to the filling itself. The device is connected directly to the battery - this can be a disadvantage. And if we talk about the advantages, then of course it is its price, which today is about 9,300 rubles. It is also worth noting that the unit is equipped with protection against overheating, high or low input voltage, and much more.
- Ritmix RPI-6010 Charger. The converter, which costs about 4,500 rubles, is distinguished by its power and excellent characteristics. At the same time, it can serve devices operating from the network or from USB. Essentially, it is a 3-in-one device that is both a converter, a car battery charger, and a backup power source. In this case, the inverter switches to different modes very quickly (no more than 4 seconds).
- MeanWell 12/220V 1500W. Such a unit costs a little more than 2,000 rubles, and it is sold immediately with the connections that you will need to connect it to the battery. In addition, the kit includes a cable for the cigarette lighter. Many users do not recommend using the device at full power when connected to a car's cigarette lighter. The advantage of such an inverter, in addition to its cost, is its compactness.
The cost of devices depends on their power, so a 12/220V in 1500W car inverter will cost an order of magnitude higher than a 300-watt inverter. But at the same time, the price will also be affected by the shape of the impulse, which we talked about earlier. To choose the optimal device and not overpay for extra energy, evaluate which electrical appliances are vital for you.
In custody
It is not recommended to use an inverter constantly, especially if we are talking about a fairly powerful device. In this case, you risk significantly shortening the life of the car battery. If possible, try to use the cigarette lighter, but if you want to sit at your laptop while fishing, then rarely using the converter will allow you to feel comfortable even in the thicket.
A car voltage inverter can sometimes be incredibly useful, but most of the products in stores are either poor in quality or not satisfactory in terms of power, and are not cheap. But the inverter circuit consists of the simplest parts, so we offer instructions for assembling a voltage converter with your own hands.
Inverter housing
The first thing to consider is the electricity conversion losses released in the form of heat on the circuit switches. On average, this value is 2-5% of the rated power of the device, but this figure tends to increase due to improper selection or aging of components.
Heat removal from semiconductor elements is of key importance: transistors are very sensitive to overheating and this is expressed in the rapid degradation of the latter and, probably, their complete failure. For this reason, the base for the case should be a heat sink - an aluminum radiator.
For radiator profiles, a regular “comb” with a width of 80-120 mm and a length of about 300-400 mm is suitable. The field-effect transistor screens are attached to the flat part of the profile with screws - metal spots on their rear surface. But this is not all simple: there should be no electrical contact between the screens of all transistors in the circuit, so the radiator and fastenings are insulated with mica films and cardboard washers, while a thermal interface is applied to both sides of the dielectric spacer with metal-containing paste.
We determine the load and purchase components
It is extremely important to understand why an inverter is not just a voltage transformer, and also why there is such a diverse range of such devices. First of all, remember that by connecting a transformer to a DC source, you will not get anything at the output: the current in the battery does not change polarity, accordingly, the phenomenon of electromagnetic induction in the transformer is absent as such.
The first part of the inverter circuit is an input multivibrator that simulates network oscillations to perform the transformation. It is usually assembled on two bipolar transistors capable of driving power switches (for example, IRFZ44, IRF1010NPBF or more powerful - IRF1404ZPBF), for which the most important parameter is the maximum permissible current. It can reach several hundred amps, but in general you just need to multiply the current by the battery voltage to get an approximate number of watts of power output without taking into account losses.
A simple converter based on a multivibrator and power field switches IRFZ44
The operating frequency of the multivibrator is not constant; calculating and stabilizing it is a waste of time. Instead, the current at the output of the transformer is converted back to DC using a diode bridge. Such an inverter can be suitable for powering purely active loads - incandescent lamps or electric heaters, stoves.
Based on the obtained base, you can assemble other circuits that differ in the frequency and purity of the output signal. It is easier to select components for the high-voltage part of the circuit: the currents here are not so high, in some cases the output multivibrator and filter assembly can be replaced with a pair of microcircuits with appropriate wiring. Electrolytic capacitors should be used for the load network, and mica capacitors for circuits with low signal levels.
Option of a converter with a frequency generator based on K561TM2 microcircuits in the primary circuit
It is also worth noting that to increase the final power it is not at all necessary to purchase more powerful and heat-resistant components of the primary multivibrator. The problem can be solved by increasing the number of converter circuits connected in parallel, but each of them will require its own transformer.
Option with parallel connection of circuits
The struggle for a sine wave - we analyze typical circuits
Voltage inverters are used everywhere today, both by motorists who want to use household appliances away from home, and by residents of autonomous homes powered by solar energy. And in general, we can say that the complexity of the converter device directly determines the width of the range of current collectors that can be connected to it.
Unfortunately, pure “sine” is present only in the main electrical network; it is very, very difficult to achieve conversion of direct current into it. But in most cases this is not required. To connect electric motors (from drills to coffee grinders), a pulsating current with a frequency of 50 to 100 hertz without smoothing is sufficient.
ESL, LED lamps and all kinds of current generators (power supplies, chargers) are more critical to the choice of frequency, since their operating circuit is based on 50 Hz. In such cases, microcircuits called a pulse generator should be included in the secondary vibrator. They can switch a small load directly, or act as a “conductor” for a series of power switches in the inverter output circuit.
But even such a cunning plan will not work if you plan to use an inverter to provide stable power to networks with a mass of heterogeneous consumers, including asynchronous electrical machines. Here, pure “sine” is very important and only frequency converters with digital signal control can implement this.
Transformer: we’ll select it or do it ourselves
To assemble the inverter, we only need one circuit element that transforms low voltage into high voltage. You can use transformers from power supplies of personal computers and old UPSs; their windings are designed to transform 12/24-250 V and back, all that remains is to correctly determine the conclusions.
Still, it’s better to wind the transformer with your own hands, since ferrite rings make it possible to do it yourself and with any parameters. Ferrite has excellent electromagnetic conductivity, which means that transformation losses will be minimal even if the wire is wound manually and not tightly. In addition, you can easily calculate the required number of turns and wire thickness using calculators available on the Internet.
Before winding, the core ring needs to be prepared - remove the sharp edges with a file and wrap tightly with an insulator - fiberglass impregnated with epoxy glue. Next comes the winding of the primary winding from thick copper wire of the calculated cross-section. After dialing the required number of turns, they must be evenly distributed over the surface of the ring at equal intervals. The winding terminals are connected according to the diagram and insulated with heat shrink.
The primary winding is covered with two layers of Mylar insulating tape, then a high-voltage secondary winding and another layer of insulation are wound. An important point is that the secondary must be wound in the opposite direction, otherwise the transformer will not work. Finally, a semiconductor thermal fuse must be soldered into the gap to one of the taps, the current and response temperature of which are determined by the parameters of the secondary winding wire (the fuse body must be tightly wound to the transformer). The transformer is wrapped on top with two layers of vinyl insulation without an adhesive base, the end is secured with a tie or cyanoacrylate glue.
Installation of radio elements
All that remains is to assemble the device. Since there are not so many components in the circuit, they can be placed not on a printed circuit board, but mounted mounted to a radiator, that is, to the device body. We solder the pin legs with a single-core copper wire of a sufficiently large cross-section, then the connection point is strengthened with 5-7 turns of thin transformer wire and a small amount of POS-61 solder. After the connection has cooled, it is insulated with a thin heat-shrink tube.
High-power circuits with complex secondary circuitry may require a printed circuit board with transistors lined up on the edge for loose attachment to the heatsink. Fiberglass with a foil thickness of at least 50 microns is suitable for making a signet; if the coating is thinner, reinforce the low-voltage circuits with jumpers made of copper wire.
Today it’s easy to make a printed circuit board at home - the Sprint-Layout program allows you to draw clipping stencils for circuits of any complexity, including double-sided boards. The resulting image is printed by a laser printer on high-quality photo paper. Then the stencil is applied to cleaned and degreased copper, ironed, and the paper is washed away with water. The technology is called “laser ironing” (LIT) and is described on the Internet in sufficient detail.
You can etch away copper residues with ferric chloride, electrolyte, or even table salt; there are plenty of ways. After etching, the baked-on toner needs to be washed off, drill mounting holes with a 1 mm drill and go over all the tracks with a soldering iron (submerged arc) to tin the copper of the contact pads and improve the conductivity of the channels.
Many radio amateurs are also car enthusiasts and love to relax with friends in nature, but they don’t want to give up the benefits of civilization at all. Therefore, they assemble a 12 220 voltage converter with their own hands, the circuit of which is shown in the figures below. In this article I will tell and show various designs of inverters that are used to obtain 220 Volt mains voltage from a car battery.
The device is built on a push-pull inverter with two powerful field-effect transistors. Any N-channel field-effect transistors with a current of 40 Amps or more are suitable for this design; I used inexpensive transistors IRFZ44/46/48, but if you need more power at the output, better use more powerful field-effect transistors.
We wind the transformer on a ferrite ring or an E50 armored core, or you can use any other one. The primary winding should be wound with a two-core wire with a cross-section of 0.8 mm - 15 turns. If you use an armored core with two sections on the frame, the primary winding is wound in one of the sections, and the secondary winding consists of 110-120 turns of copper wire 0.3-0.4 mm. At the output of the transformer we obtain an alternating voltage in the range of 190-260 Volts, rectangular pulses.
The 12 220 voltage converter whose circuit has been described can power various loads, power of which is no more than 100 watts
Output pulse shape - Rectangular
A transformer in a circuit with two primary windings of 7 Volts (each arm) and a mains winding of 220 Volts. Almost any transformers from uninterruptible power supplies are suitable, but with a power of 300 watts or more. The diameter of the primary winding wire is 2.5 mm.
Transistors IRFZ44, if missing, can be easily replaced with IRFZ40,46,48 and even more powerful ones - IRF3205, IRL3705. The transistors in the TIP41 (KT819) multivibrator circuit can be replaced with domestic KT805, KT815, KT817, etc.
Attention, the circuit does not have protection at the output and input from short circuit or overload, the keys will overheat or burn out.
Two versions of the printed circuit board design and a photo of the finished converter can be downloaded from the link above.
This converter is quite powerful and can be used to power a soldering iron, grinder, microwave oven and other devices. But do not forget that its operating frequency is not 50 Hertz.
The primary winding of the transformer is wound with 7 cores at once, with a wire with a diameter of 0.6 mm and contains 10 turns with a tap from the middle stretched across the entire ferrite ring. After winding, we insulate the winding and begin to wind the step-up winding, with the same wire, but already 80 turns.
It is advisable to install power transistors on heat sinks. If you assemble the converter circuit correctly, it should work immediately and does not require any configuration.
As with the previous design, the heart of the circuit is the TL494.
This is a ready-made push-pull pulse converter device; its complete domestic analogue is 1114EU4. High-efficiency rectifier diodes and a C-filter are used at the output of the circuit.
In the converter I used a ferrite W-shaped core from the TPI TV transformer. All the original windings were unwound, because I re-wound the secondary winding 84 turns with 0.6 wire in enamel insulation, then a layer of insulation and move on to the primary winding: 4 turns oblique from 8 0.6 wires, after winding the windings were ringed and divided in half, we got 2 windings of 4 turns in 4 wires, the beginning of one was connected to the end of the other, so we made a tap from the middle, and finally wound the feedback winding with five turns of PEL 0.3 wire.
The 12 220 voltage converter circuit that we examined includes a choke. You can make it yourself by winding it on a ferrite ring from a computer power supply with a diameter of 10 mm and 20 turns of PEL 2 wire.
There is also a drawing of a printed circuit board for a 12,220 volt voltage converter circuit:
And a few photos of the resulting 12-220 Volt converter:
Again, I liked the TL494 paired with mosfets (This is such a modern type of field-effect transistors), this time I borrowed the transformer from an old computer power supply. When laying out the board, I took into account its conclusions, so be careful when choosing your placement option.
To make the case, I used a 0.25L soda can, which I had successfully snatched up after a flight from Vladivostok, cut off the top ring with a sharp knife and cut out the middle of it, and glued a circle of fiberglass with holes for a switch and connector into it using epoxy.
To give the jar rigidity, I cut a strip the width of our body from a plastic bottle, coated it with epoxy glue and placed it in the jar. After the glue had dried, the jar became quite rigid and had insulated walls; the bottom of the jar was left clean for better thermal contact with the radiator of the transistors.
To complete the assembly, I soldered the wires to the cover and secured it with hot glue; this will allow, if the need arises, to disassemble the voltage converter by simply heating the cover with a hairdryer.
The design of the converter is designed to convert 12 volt voltage from the battery into 220 volt alternating voltage with a frequency of 50 Hz. The idea for the scheme was borrowed from November 1989.
The amateur radio design contains a master oscillator designed for a frequency of 100 Hz on the K561TM2 trigger, a frequency divider by 2 on the same chip, but on the second trigger, and a power amplifier using transistors loaded by a transformer.
Taking into account the output power of the voltage converter, transistors should be installed on radiators with a large cooling area.
The transformer can be rewound from an old network transformer TS-180. The mains winding can be used as a secondary winding, and then windings Ia and Ib are wound.
A voltage converter assembled from working components does not require adjustment, with the exception of the selection of capacitor C7 with a connected load.
If you need a printed circuit board drawing made in , click on the PCB drawing.
Signals from the PIC16F628A microcontroller through 470 Ohm resistances control the power transistors, forcing them to open one by one. The half-windings of a transformer with a power of 500-1000 VA are connected to the source circuits of field-effect transistors. There should be 10 volts on its secondary windings. If we take a wire with a cross-section of 3 mm2, then the output power will be about 500 W.
The whole design is very compact, so you can use a breadboard without etching the tracks. You can catch the archive with the microcontroller firmware at the green link just above
The 12-220 converter circuit is made on a generator that creates symmetrical pulses that follow out of phase and an output block implemented on field switches, the load of which is connected to a step-up transformer. Using elements DD1.1 and DD1.2, a multivibrator is assembled according to the classical scheme, generating pulses with a repetition frequency of 100 Hz.
To form symmetrical pulses traveling in antiphase, the circuit uses a D-trigger of the CD4013 microcircuit. It divides by two all impulses entering its input. If we have a signal going to the input with a frequency of 100 Hz, then the output of the trigger will be only 50 Hz.
Since field-effect transistors have an insulated gate, the active resistance between their channel and the gate tends to an infinitely large value. To protect the trigger outputs from overload, the circuit has two buffer elements DD1.3 and DD1.4, through which the pulses travel to the field-effect transistors.
A step-up transformer is included in the drain circuits of the transistors. To protect against self-induction, high-power zener diodes are connected to the drains. RF interference suppression is carried out by a filter on R4, C3.
The winding of the inductor L1 is made by hand on a ferrite ring with a diameter of 28 mm. It is wound with PEL-2 0.6 mm wire in one layer. The most common network transformer is 220 volts, but with a power of at least 100 W and having two secondary windings of 9 V each.
To increase the efficiency of the voltage converter and prevent severe overheating, field-effect transistors with low resistance are used in the output stage of the inverter circuit.
On DD1.1 – DD1.3, C1, R1, a rectangular pulse generator with a pulse repetition rate of 200 Hz is made. Then the pulses arrive at a frequency divider built on elements DD2.1 - DD2.2. Therefore, at the output of the divider 6, the output of DD2.1, the frequency is reduced to 100Hz, and already at the 8th output of DD2.2. it is 50 Hz.
The signal from pin 8 of DD1 and pin 6 of DD2 goes to diodes VD1 and VD2. To fully open the field-effect transistors, it is necessary to increase the amplitude of the signal that passes from the diodes VD1 and VD2; for this, VT1 and VT2 are used in the voltage converter circuit. The field-effect output transistors are controlled through VT3 and VT4. If no errors were made during the assembly of the inverter, then it starts working immediately after power is applied. The only thing that is recommended to do is to select the value of resistance R1 so that the output is the usual 50 Hz. VT5 and VT6. When output Q1 (or Q2) goes low, transistors VT1 and VT3 (or VT2 and VT4) open, and the gate capacitances begin to discharge, and transistors VT5 and VT6 close.
The converter itself is assembled according to the classic push-pull circuit.
If the voltage at the output of the converter exceeds the set value, the voltage at resistor R12 will be higher than 2.5 V, and therefore the current through the DA3 stabilizer will increase sharply and a high-level signal will appear at the FV input of the DA1 chip.
Its outputs Q1 and Q2 will switch to the zero state and field-effect transistors VT5 and VT6 will close, causing a decrease in the output voltage.
A current protection unit based on relay K1 has also been added to the voltage converter circuit. If the current flowing through the winding is higher than the set value, the contacts of the reed switch K1.1 will operate. The FC input of the DA1 chip will be high and its outputs will go low, causing transistors VT5 and VT6 to close and a sharp decrease in current consumption.
After this, DA1 will remain in a locked state. To start the converter, a voltage drop at the input IN DA1 will be required, which can be achieved either by turning off the power or by short-circuiting capacitance C1. To do this, you can introduce a non-latching button into the circuit, the contacts of which are soldered parallel to the capacitor.
Since the output voltage is a square wave, capacitor C8 is designed to smooth it. The HL1 LED is necessary to indicate the presence of output voltage.
The T1 transformer is made from TS-180; it can be found in the power supplies of old CRT televisions. All its secondary windings are removed, and the network voltage of 220 V is left. It serves as the output winding of the converter. Half-windings 1.1 and I.2 are made from PEV-2 wire 1.8, 35 turns each. The beginning of one winding is connected to the end of the other.
The relay is homemade. Its winding consists of 1-2 turns of insulated wire, rated for current up to 20...30 A. The wire is wound on the reed switch body with making contacts.
By selecting resistor R3, you can set the required frequency of the output voltage, and resistor R12 - the amplitude from 215...220 V.
Voltage for motorists, since in a car it may very often be necessary to obtain mains voltage. This converter can be used to power soldering irons, incandescent lamps, coffee makers and other devices that are powered by a 220 Volt network. The converter can also power active loads - a TV or DVD player, but it is worth noting that this is quite dangerous, since the operating frequency of the converter is quite different from the network 50 Hertz. But, as you know, these devices are equipped with switching power supplies, where the mains voltage is rectified by diodes. These diodes can rectify high frequency current, but I must note that not all pulse units can have such diodes, so it’s better not to risk it. Such a DC-AC voltage converter can be assembled in a couple of hours if you have the necessary components on hand. A scaled-down diagram is shown in the figure:
Transformer is the power component of such a converter. It is wound on a ring of ferrite, which was removed from a Chinese power supply unit for halogen lamps (power 60 watts).
The primary winding of the transformer was wound with 7 wires. To wind both windings, a wire with a diameter of 0.5-0.6 mm was used. The primary winding consists of 10 turns tapped from the middle, i.e. two equal halves of 5 turns each. The windings are stretched across the entire ring. After winding, it is advisable to insulate the windings and wind them with a step-up winding.
The secondary winding consists of 80 turns (the same wire was used as for winding the primary winding). The transistors were installed on heat sinks, but do not forget to insulate them using special gaskets and washers. This is done only when both transistors have a common heat sink.
The choke can be removed and the power connected directly. It consists of 7-10 turns of 1mm wire. The inductor can be wound on a ring made of powdered iron (such rings can easily be found in computer power supplies). The inverter circuit does not require preliminary adjustment and works immediately.
The operation is quite stable, thanks to the additional driver, the chip does not heat up. The transistors heat up within normal limits, but I advise you to choose a larger heat sink for them.
The installation is carried out in a housing from , which plays the role of a heat sink for field keys.
Buying a ready-made device will not be a problem– in auto stores you can find (pulse voltage converters) of various powers and prices.
However, the price of such a medium-power device (300-500 W) is several thousand rubles, and the reliability of many Chinese inverters is quite controversial. Making a simple converter with your own hands is not only a way to significantly save money, but also an opportunity to improve your knowledge in electronics. In case of failure, repairing a homemade circuit will be much easier.
Simple pulse converter
The circuit of this device is very simple, and most parts can be removed from an unnecessary computer power supply. Of course, it also has a noticeable drawback - the 220 volt voltage obtained at the output of the transformer is far from sinusoidal in shape and has a frequency significantly higher than the accepted 50 Hz. Electric motors or sensitive electronics must not be connected directly to it.
In order to be able to connect equipment containing switching power supplies (for example, a laptop power supply) to this inverter, an interesting solution was used - A rectifier with smoothing capacitors is installed at the output of the transformer. True, the connected adapter can only work in one position of the socket, when the polarity of the output voltage coincides with the direction of the rectifier built into the adapter. Simple consumers such as incandescent lamps or a soldering iron can be connected directly to the output of transformer TR1.
The basis of the above circuit is the TL494 PWM controller, the most common in such devices. The operating frequency of the converter is set by resistor R1 and capacitor C2; their values can be taken slightly different from those indicated without noticeable changes in the operation of the circuit.
For greater efficiency, the converter circuit includes two arms on power field-effect transistors Q1 and Q2. These transistors should be placed on aluminum radiators; if you intend to use a common radiator, install the transistors through insulating spacers. Instead of the IRFZ44 indicated in the diagram, you can use IRFZ46 or IRFZ48 that are similar in parameters.
The output choke is wound on a ferrite ring from the choke, also removed from the computer power supply. The primary winding is wound with a wire with a diameter of 0.6 mm and has 10 turns with a tap from the middle. A secondary winding containing 80 turns is wound on top of it. You can also take an output transformer from a broken uninterruptible power supply.
Read also: Review of wood-burning electric generators
Instead of high-frequency diodes D1 and D2, you can take diodes of types FR107, FR207.
Since the circuit is very simple, once turned on and installed correctly, it will start working immediately and will not require any configuration. 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.
Ready-made inverter of such power would cost about three to four thousand rubles.This scheme is made with domestic components and is quite old, but this does not make it any less effective. Its main advantage is the output of full alternating current with a voltage of 220 volts and a frequency of 50 Hz.
Here the oscillation generator is made on the K561TM2 microcircuit, which is a dual D-trigger. It is a complete analogue of the foreign CD4013 microcircuit and can be replaced with it without changes in the circuit.
The converter also has two power arms based on KT827A bipolar transistors. Their main drawback compared to modern field ones is their higher resistance in the open state, which is why they heat up more for the same switched power.
Since the inverter operates at low frequency, the transformer must have a powerful steel core. The author of the diagram suggests using the common Soviet network transformer TS-180.
Like other inverters based on simple PWM circuits, this converter has an output voltage waveform quite different from the sinusoidal one, but this is somewhat smoothed out by the large inductance of the transformer windings and the output capacitor C7. Also, because of this, the transformer may emit a noticeable hum during operation - this is not a sign of a circuit malfunction.
Simple transistor inverter
This converter works on the same principle as the circuits listed above, but the square-wave generator (multivibrator) in it is built on bipolar transistors.
The peculiarity of this circuit is that it remains operational even on a heavily discharged battery: the input voltage range is 3.5...18 volts. But, since it does not have any stabilization of the output voltage, when the battery is discharged, the load voltage will simultaneously drop proportionally.
Since this circuit is also low-frequency, a transformer will be required similar to that used in the inverter based on K561TM2.
Improvements to inverter circuits
The devices presented in the article are extremely simple and have a number of functions. cannot compare with factory analogues. To improve their characteristics, you can resort to simple modifications, which will also allow you to better understand the principles of operation of pulse converters.
Read also: Let's make an electric generator with our own hands
Increased power output
All described devices operate on the same principle: through a key element (arm output transistor), the primary winding of the transformer is connected to the power input 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.
Therefore, the current flowing through the output transistor is equal to the load current multiplied by the inverse turns ratio (transformation ratio). It is the maximum current that the transistor can pass through itself that determines the maximum power of the converter.
There are two ways to increase the power of the inverter: either use a more powerful transistor, or use parallel connection of several less powerful transistors in one arm. For a homemade converter, the second method is preferable, since it not only allows you to use cheaper parts, but also preserves the functionality of the converter if one of the transistors fails. In the absence of built-in overload protection, such a solution will significantly increase the reliability of a homemade device. The heating of the transistors will also decrease when they operate at the same load.
Using the last diagram as an example, it will look like this:
Automatic shutdown when battery is low
The absence of a device in the converter circuit that automatically turns it off when the supply voltage drops critically, can seriously let you down, if you leave such an inverter connected to the car battery. Supplementing a homemade inverter with automatic control will be extremely useful.
The simplest automatic load switch can be made from a car relay:
As you know, each relay has a certain voltage at which its contacts close. By selecting the resistance of resistor R1 (it will be about 10% of the resistance of the relay winding) you adjust the moment when the relay opens its contacts and stops supplying current to the inverter.
EXAMPLE: Let's take a relay with an operating voltage (U p) 9 volts and winding resistance (R o) 330 ohm. So that it works at a voltage above 11 volts (U min), a resistor with resistance must be connected in series with the windingR n, calculated from the condition of equalityU r /R o =(U min —U p)/R n. In our case, we will need a 73 ohm resistor, the nearest standard value is 68 ohms.Of course, this device is extremely primitive and is more of a workout for the mind. For more stable operation, it needs to be supplemented with a simple control circuit that maintains the shutdown threshold much more accurately:
Read also: We are talking about 10 kW voltage stabilizers for the home
The response threshold is adjusted by selecting resistor R3.
We invite you to watch a video on the topic
Inverter fault detection
The listed simple circuits have the two most common faults - either there is no voltage at the transformer output, or it is too low.
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