In what areas is a 12-220 V voltage inverter used?
With stable use of the battery, its charge level gradually decreases. The converter stabilizes the voltage if there is no electricity.
A 12-220 V inverter, made by yourself, will allow you to improve engineering structures in any room. The power value of devices that convert current is selected according to the total values of the operated loads. Power consumption processes can be reactive or active. Reactive loads do not fully consume the amount of energy received, causing the apparent power value to be greater than its active value.
Pure sine wave inverters are used when connecting an element whose total power is 3 kW. Significant fuel savings are ensured by the use of voltage converters and mini-power plants.
The following consumers are connected to the inverter design:
- alarm system;
- boiler;
- pumping apparatus;
- computer system.
Simplified version of the voltage converter
Figure 2 shows a simplified version of the generator, which operates similarly to the one described above. The generator, using a small-sized electrolytic capacitor, operates at a supply voltage of 0.9 to 1.6 V.
The average current consumed by the device does not exceed 3 mA at a pulse repetition rate of about 2 Hz. The brightness of the generated flashes of light is slightly lower than in the previous scheme.
Rice. 2. Circuit of a simple low-voltage voltage converter using two transistors from 0.9V to 2V.
Electrician in the house
Author: admin, April 12, 2013
DIY 12/220 voltage converter
Currently, quite a lot of 12/220 V voltage converters are produced, designed for fairly high powers.
But if you need a simple 12/220 voltage converter for your dacha or garage for lighting (TV, drill, pump), then you can make it yourself. The proposed scheme differs favorably from similar ones by the presence of a low battery alarm. This is very important if you use a car battery to power the circuit. Although it is better to take another battery, or buy a new battery for the car and use the old one for the converter. The circuit uses a minimum of parts, but the device copes with its function quite well. Such devices that convert direct voltage into alternating voltage are also called inverters.
12/220 V voltage converter circuit
The diagram indicates:
- FU1 - 10A fuse.
- R1 - resistor MLT-0.5, 150 Ohm.
- R2 - variable resistor SP-1, 22 kOhm.
- R3 - trimming resistor SP3-16, 1 MOhm
- R4 - resistor MLT-0.125, 330 Ohm.
- R5, R7, R8 - resistors MLT-0.125, 2 kOhm.
- R6 - resistor MLT-0.125 1.5 kOhm.
- VD1 - zener diode KS 191A.
- C1 - capacitor K53-1, 50 µF x 50 V.
- C2, C3 - capacitors KM-5, 0.1 µF.
- C4, C5 - capacitors KM-5, 510 pF.
- VT1 is a unijunction transistor KT 117A.
- VT2, VT3 - KT 827A transistors.
- L1 - LED AL 307A.
- DD1 - K561TM2 chip.
- T1 - transformer.
Description of the circuit operation
The generator, assembled on transistor VT1, generates oscillations with a frequency of 100 Hz, the frequency can be adjusted by trimming resistor R3. Trigger DD1.2 divides the frequency in half and at outputs 12 and 13 of the trigger, pulses of opposite amplitude with a frequency of 50 Hz are formed. The pulses alternately open transistors VT2 and VT3, which are connected according to the circuit of a push-pull power amplifier. The load of transistors VT1, VT2 is windings 1 and 2 of step-up transformer T1, on the secondary winding 3 of which an alternating voltage of 220V, 50 Hz is generated.
The stabilizer made on VD1, R1 and smoothing capacitor C1 serve to power the microcircuit and generator and eliminate the influence of the operation of key transistors VT1, VT2 on the operation of the circuit, and capacitors C5, C4 reduce the time of the transition process (help these transistors switch faster). Trigger DD1 turns on the signal LED L1 when the battery voltage drops to a predetermined value, which is set by variable resistor R2.
Setting up the circuit
- Disconnect “+” from the connection of windings 1 and 2.
- Check the frequency at the bases of transistors VT2 and VT3 using an oscilloscope, adjust, if necessary, with resistor R3 to 50Hz.
- Reduce the power supply voltage to 10-11V. Achieve constant lighting of LED L1 using variable resistor R2.
- Connect “+” back to the connection point of windings 1 and 2.
- Check the operation of the device on a fully charged battery.
Circuit details
Transistors VT2, VT3 KT 827 can be taken with any letter index, but preferably with the highest base current transfer coefficient.
Zener diode VD1 can be replaced with any other with a stabilization voltage of 8-9V.
The transformer can be made on the basis of the PLM 27-40-58 magnetic circuit. Wind primary windings 1 and 2 with PBD-2 (PSD-2) wire, 15 turns each. Wind the secondary winding 3 with PEV-2 wire, 0.64 mm - 704 turns.
Install capacitor C2 directly at the terminals of microcircuit DD1.
If you do not have the required value of resistors and capacitors, you can make up the required one from several parts, as described in this article.
A printed circuit board can be made using the technology described in this article.
Converter parameters 12/220
This voltage converter was tested with a load of 100 W. The current consumption of the converter is no more than 10A, the current consumption without load is no more than 1A. The converter can withstand the starting currents of an electric pump and electric drill. The maximum output voltage drop is 10 V.
To power equipment that requires a sinusoidal signal, a capacitor can be installed at the output to smooth out the squareness of the pulses; its capacitance must be selected to achieve the best result; the selection can begin with a capacitance of 1 μF. The capacitor must be designed for a voltage of at least 400V.
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Battery and power
The suitability of the converter for a particular purpose also depends on the battery. A boost voltage inverter does not take energy for consumers from the “dark matter” of the Universe, black holes, the holy spirit, or anywhere else just like that. Only from the battery. And from it he will take the power supplied to consumers, divided by the efficiency of the converter itself.
Car enthusiasts know: if you run the starter for 20 minutes, buy a new battery. True, new machines have time limiters for its operation, so perhaps they don’t know. And certainly not everyone knows that the starter of a car, once spun up, takes a current of approx. 75 A (within 0.1-0.2 s at startup - up to 600 A). The simplest calculation - and it turns out that if the inverter does not have automatic equipment that limits the battery discharge, then ours will run out completely in 15 minutes. So choose or design your converter taking into account the capabilities of the existing battery.
The service life of acid batteries does not noticeably decrease if they are discharged with a 2-hour current (12 A for 60 A/h, 24 A for 120 A/h and 42 A for 210 A/h). Taking into account the conversion efficiency, this gives a permissible long-term load power of approx. 120 W, 230 W and 400 W respectively. For 10 min. load (for example, to power a power tool), it can be increased by 2.5 times, but after this the ABC must rest for at least 20 minutes.
Overall, the result is not entirely bad. Of the ordinary household power tools, only the grinder can take 1000-1300 W. The rest, as a rule, cost up to 400 W, and screwdrivers up to 250 W. A refrigerator from a 12 V 60 A/h battery will work through an inverter for 1.5-5 hours; quite enough to take the necessary measures. Therefore, making a 1 kW converter for a 60 A/h battery makes sense.
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 solid 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.
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 vice versa; 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.
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.
How things are now
Modern element base makes it possible today to simplify the above-described design to a minimum.
Chip KR1211EU1
- To do this, you will first have to replace the bulky generator with a special microcircuit of the KR1211EU1 brand. Please note that this microcircuit is domestically produced; you will not find foreign analogues.
- Instead of power switches, it is best to use IRL2505 transistors; they are powerful and are used in car electrical circuits. By the way, their resistance is 0.008 Ohm, which is not comparable to mechanical contacts.
