A car voltage inverter can sometimes be incredibly useful, but most of the products in stores either suffer from poor quality or are unsatisfactory 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 power supply 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 leads 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.
We present a push-pull pulse converter assembled on the TL494 PWM controller. This makes the circuit quite simple and easy to repeat for many radio amateurs. At the output there are highly efficient rectifier diodes that double the voltage. You can also use a voltage converter without diodes - getting an alternating voltage. For example, for electronic ballasts (when powered by LDS), constant voltage and switching polarity are not relevant, since the ballast circuit has a diode bridge at the input. The schematic diagram is shown in the figure - click to enlarge.
The 12-220 V converter uses a ready-made high-frequency step-down transformer from the computer's AT or ATX power supply, but in our converter it will become a step-up transformer. Typically, these transformers differ only in size, and the location of the pins is identical. A non-working PC power supply can be found at any computer repair shop.
Operation of the circuit. Resistor R1 sets the width of the output pulses, R2 (together with C1) sets the operating frequency. We reduce the resistance R1 - we increase the frequency. We increase the capacitance C1 - we reduce the frequency. We use powerful MOS field effect transistors in the voltage converter, which are characterized by shorter response times and simpler control circuits. IRFZ44N, IRFZ46N, IRFZ48N work equally well here.
A radiator is not needed, since prolonged operation does not cause noticeable heating of the transistors. And if you still want to put them on a radiator, do not short-circuit the flanges of the transistor housings through the radiator! Use insulating gaskets and bushing washers from a computer power supply. However, for the first start, a radiator will not hurt; at least the transistors will not immediately burn out in the event of installation errors or a short circuit at the output.
A correctly assembled converter circuit does not require adjustment. It is advisable to use a non-metallic housing to prevent high voltage breakdown on the housing. Be careful when working with the circuit, as 220 V voltage is dangerous!
Discuss the article CONVERTER 12-220
When using low-power household appliances, there is often a need for a voltage converter from 12 to 220 volts. This could be a laptop, a charger for a mobile phone or tablet, or even a TV with LED elements.
In what cases is a voltage converter needed?
- Long-term failure of centralized power supply.
- Emergency power supply for gas boiler electronics.
- Lack of 220 volt household network (remote garden plot, garage cooperative).
- Automobile.
- Tourist parking (if possible, take a 12 volt battery with you).
In all these cases, it is enough to have a charged battery, and you will be able to fully use the network electrical equipment.
note
Important! The power consumption of the device should not exceed several hundred watts. More powerful devices will quickly drain the battery used as a donor.
To be fair, we note that for use in a car there are power supplies and chargers that are connected to the 12 volt on-board network. They are made in the form of a connector connected to the cigarette lighter socket.
However, if you have several gadgets, you will have to splurge on buying the same number of chargers. And having one converter from 12 to 220, you will ensure complete connection versatility.
There is a wide range of ready-made converters available for sale. Power varies from 150 W to several kilowatts. Of course, for each consumer power it is necessary to select the appropriate battery.
It is also necessary to carefully read the technical specifications - often, for advertising purposes, manufacturers indicate on the packaging the peak power that the converter can withstand for just a few seconds. Operating power is typically 25% - 30% lower.
Types of converters 12 to 220 volts
To make the right choice, familiarize yourself with the main types of voltage converters presented on the electrical goods market:
According to the output voltage waveform
The devices are divided into pure sine and modified sine. The difference in signal shape can be seen in the illustration.
The fact is that inverters work differently than alternators. A direct current of a certain magnitude is supplied to the input of the device.
First, it is converted into a pulsed one (to ensure the operation of a step-up transformer), then a sinusoidal curve is formed from the resulting pulsating current, which is familiar to most consumers of 220 volt alternating voltage.
I decided to dedicate a separate article to the manufacture of a DC AC step-up voltage converter for 220V. This, of course, is remotely related to the topic of LED spotlights and lamps, but such a mobile power source is widely used at home and in the car.
- 1. Assembly options
- 2. Voltage converter design
- 3. Sine wave
- 4. Example of converter filling
- 5. Assembly from UPS
- 6. Assembly from ready-made blocks
- 7. Radio constructors
- 8. Circuits of powerful converters
Assembly options
There are 3 optimal ways to make a 12 to 220 inverter with your own hands:
- assembly from ready-made blocks or radio constructors;
- manufacturing from an uninterruptible power supply;
- use of amateur radio circuits.
From the Chinese you can find good radio constructors and ready-made blocks for assembling DC to AC 220V converters. In terms of price, this method will be the most expensive, but it requires the least amount of time.
The second method is to upgrade an uninterruptible power supply (UPS), which without a battery is sold in large quantities on Avito and costs from 100 to 300 rubles.
The most difficult option is assembly from scratch; you can’t do it without amateur radio experience. We will have to make printed circuit boards, select components, a lot of work.
Voltage converter design
Let's consider the design of a conventional step-up voltage converter from 12 to 220. The operating principle for all modern inverters will be the same. The high-frequency PWM controller sets the operating mode, frequency and amplitude. The power part is made of powerful transistors, the heat from which is transferred to the device body.
A fuse is installed at the input to protect the car battery from short circuits. A thermal sensor is attached next to the transistors, which monitors their heating. If the 12v-220v inverter overheats, an active cooling system consisting of one or more fans is turned on. In budget models, the fan can work constantly, and not just under high load.
Power transistors at the output
Sine wave
The signal shape at the output of a car inverter is generated by a high-frequency generator. A sine wave can be of two types:
- modified sine wave;
- pure sine wave, pure sine wave.
Not every electrical device can work with a modified sine wave, which has a rectangular shape. Some components change their operating mode, they can heat up and start to get dirty. You can get something similar if you dim an LED lamp whose brightness is not adjustable. The crackling and flashing starts.
Expensive DC AC step-up voltage converters 12V-220V have a pure sine wave output. They cost much more, but electrical appliances work great with it.
Example of converter filling
Assembly from UPS
In order not to invent anything and not to buy ready-made modules, you can try a computer uninterruptible power supply, abbreviated as UPS. They are designed for 300-600W. I have an Ippon with 6 sockets, 2 monitors, 1 system unit, 1 TV, 3 surveillance cameras, a video surveillance management system are connected. I periodically switch it to operating mode by disconnecting the 220 from the network so that the battery is discharged, otherwise the service life will be greatly reduced.
Electrician colleagues connected a regular car acid battery to an uninterruptible power supply, it worked perfectly for 6 hours continuously, and they watched football in the country. The UPS usually has a built-in gel battery diagnostic system that detects its low capacity. How it will react to the automobile is unknown, although the main difference is gel instead of acid.
UPS filling
The only problem is that the UPS may not like surges in the car network when the engine is running. For a real radio amateur, this problem is solved. Can only be used with the engine turned off.
Mostly UPSs are designed for short-term operation when 220V in the outlet disappears. For long-term continuous operation, it is highly advisable to install active cooling. Ventilation is useful for a stationary option and for a car inverter.
Like all devices, it will behave unpredictably when starting the engine with a connected load. The car's starter draws a lot of volts, at best it will go into protection as if the battery fails. At worst, there will be surges in the 220V output, the sine wave will be distorted.
Assembly from ready-made blocks
To assemble a stationary or automotive 12v 220v inverter with your own hands, you can use ready-made blocks that are sold on eBay or from the Chinese. This will save time on board manufacturing, soldering and final setup. It is enough to add a housing and wires with crocodiles to them.
You can also purchase a radio kit, which is equipped with all radio components; all that remains is to solder it.
Approximate price for autumn 2016:
- 300W – 400rub;
- 500W – 700rub;
- 1000W – 1500rub;
- 2000W – 1700rub;
- 3000W - 2500 rub.
To search on Aliexpress, enter the query “inverter 220 diy” in the search line. The abbreviation "DIY" stands for "do-it-yourself assembly."
500W board, output for 160, 220, 380 volts
Radio constructors
A radio kit costs less than a ready-made board. The most complex elements may already be on the board. Once assembled, it requires virtually no setup, which requires an oscilloscope. The range of radio component parameters and ratings are well chosen. Sometimes they put spare parts in a bag, in case you tear off the leg due to inexperience.
Power converter circuits
A powerful inverter is mainly used to connect construction power tools during the construction of a summer house or hacienda. A low-power 500-watt voltage converter differs from a powerful 5,000-10,000-watt converter in the number of transformers and power transistors at the output. Therefore, the manufacturing complexity and price are almost the same; transistors are inexpensive. The power is optimally 3000 W, you can connect a drill, grinder and other tools.
I will show several inverter circuits from 12, 24, 36 to 220V. It is not recommended to install these in a passenger car; you can accidentally damage the electrics. The circuit design of DC AC converters 12 to 220 is simple, a master oscillator and a power section. The generator is made on the popular TL494 or analogues.
A large number of booster circuits from 12v to 220v for DIY production can be found at the link
http://cxema.my1.ru/publ/istochniki_pitanija/preobrazovateli_naprjazhenija/101-4
In total there are about 140 circuits, half of them are boost converters from 12, 24 to 220V. Powers from 50 to 5000 W.
After assembly, you will need to adjust the entire circuit using an oscilloscope; it is advisable to have experience working with high-voltage circuits.
To assemble a powerful 2500 Watt inverter you will need 16 transistors and 4 suitable transformers. The cost of the product will be considerable, comparable to the cost of a similar radio designer. The advantage of such costs will be a pure sine output.
I bought myself a car six months ago. I will not describe all the modernizations made to improve it, I will focus on only one. This is a 12-220V inverter for powering consumer electronics from the vehicle's on-board network.
Of course, you could buy it in a store for $25-30, but I was confused by their power. To power even a laptop, the 0.5-1 ampere current that most car inverters produce is clearly not enough.
Choosing a circuit diagram.
By nature, I am a lazy person, so I decided not to “reinvent the wheel”, but to search the Internet for similar designs and adapt the circuit of one of them for my own. Time was very pressing, so simplicity and the absence of expensive spare parts were the priority.
On one of the forums, a simple circuit was chosen using the common PWM controller TL494. The disadvantage of this circuit is that it produces a rectangular voltage of 220 V at the output, but for pulsed power circuits this is not critical.
Selection of parts.
The circuit was chosen because almost all the parts could be taken from a computer power supply. For me this was very critical, because the nearest specialized store is more than 150 km away.
Output capacitors, resistors, and the microcircuit itself were removed from a pair of faulty power supplies of 250 and 350 W.
The difficulty arose only with high-frequency diodes for converting the voltage at the output of the step-up transformer, but here old supplies saved me. The characteristics of the KD2999V suited me quite well.
Assembly of the finished device.
I had to assemble the device within a couple of hours after work, because a long trip was planned.
Since time was very limited, I simply did not look for additional materials and tools. I used only what was at hand. Again, due to speed, I did not use the printed circuit board samples provided on the forums. In 30 minutes, we designed our own printed circuit board on a piece of paper, and its design was transferred to the PCB.
Using a scalpel, one of the foil layers was removed. On the remaining layer, deep grooves were drawn along the applied lines. Using curved tweezers, it turned out to be the most convenient, the grooves were deepened to the non-conducting layer. At the places where the parts were installed using an awl, it was not included in the photo; holes were made.
I started the assembly by installing a transformer, I used a step-down one of the blocks, I simply turned it over and instead of lowering the voltage from 400 V to 12 V, it raised it from 12 V to 268 V. By replacing resistors R3 and capacitor C1, it was possible to reduce the output voltage to 220 V, but further experiments showed that this should not be done.
After the transformer, in order of decreasing size, I installed the remaining spare parts.
It was decided to install field-effect transistors on elongated inputs so that they are easier to attach to the cooling radiator.
The end result is this device:
All that remains is the finishing touch - attaching the radiator. There are 4 holes visible on the board, although there are only 3 self-tapping screws; it was just during the assembly process that it was decided to slightly change the position of the radiator for a better appearance. After final assembly this is what we got:
Tests.
There was no time to specifically test the device; it was simply connected to the battery from an uninterruptible power supply. A load in the form of a 30 W light bulb was connected to the output. After it caught fire, the device was simply thrown into my backpack, and I went on a business trip for 2 weeks.
In 2 weeks, the device never failed. Various devices were powered from it. When measured with a multimeter, the maximum current obtained reached 2.7 A.