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To connect household appliances to the on-board electrical system of a car, an inverter is required that can increase the voltage from 12 V to 220 V. They are available in sufficient quantities 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 their own hands. We will analyze two simple schemes.
Converters and their types
There are three types of 12-220 V converters. The first one is 12 V from 220 V. Such inverters are popular with motorists: you can connect standard devices through them – 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, pools or bathrooms. In order not to risk, the standard voltage of 220 V is reduced to 12 using the 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, when installing a gas boiler, it is strongly advised to power it through such a converter – its electronics are very sensitive to the quality of the power supply, and replacing the control board costs about half the boiler.
Pulse converter 12-220V to 300 W
This circuit is simple, parts are available, most of them can be taken from a computer power supply or bought at any electronics store. The advantage of the circuit is the 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 requiring power supply cannot be connected to this converter. Not particularly sensitive devices can be connected directly to the output – incandescent lamps, an iron, a soldering iron, charging from a phone, etc.
The presented circuit in normal mode produces 1,5 A or pulls a load of 300 W, to a maximum of 2,5 A, but in this mode, transistors will noticeably heat up.
The circuit was built on the popular PWM controller TLT494. Field-effect transistors Q1 Q2 must be placed on radiators, preferably separate ones. When installing on a single radiator, lay an insulating gasket under the transistors. Instead of those indicated on the IRFZ244 diagram, you can use IRFZ46 or RFZ48 that are similar in characteristics.
The frequency in this 12 V to 220 V converter is set by resistor R1 and capacitor C2. The ratings may differ slightly from those indicated in the diagram. If you have an old non-working power supply for a computer, and it has a working output transformer, you can put it in the circuit. If the transformer is inoperative, remove the ferrite ring from it and wind the windings with a copper wire with a diameter of 0,6 mm. First, the primary winding is wound – 10 turns with a lead from the middle, then, on top – 80 turns of the secondary.
As already mentioned, such a 12-220 V voltage converter can only work with a load that is insensitive to power quality. In order to be able to connect more demanding devices, a rectifier is installed at the output, at the output of which the voltage is close to normal (diagram below).
The diagram shows high-frequency diodes of the HER307 type, but they can be replaced with the FR207 or FR107 series. Capacities are desirable to choose the specified value.
Inverter chip
This 12-220 V voltage converter is assembled on the basis of a specialized KR1211EU1 microcircuit. This is a pulse generator that is taken from outputs 6 and 4. The pulses are antiphase, there is a small time gap 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 field-effect transistors of increased power – IRL2505 (VT1 and VT2). They have a very low open output channel resistance – about 0,008 ohms, which is comparable to the resistance of a mechanical key. Permissible direct current – up to 104 A, pulse – up to 360 A. Such characteristics really allow you to get 220 V at a load of up to 400 W. It is necessary to install transistors on radiators (with a power of up to 200 W, it is possible without them).
The pulse frequency depends on the parameters of the resistor R1 and the capacitor C1, a capacitor C6 is installed at the output to suppress high-frequency emissions.
It is better to take the transformer ready. In the circuit, it turns on the other way around – 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 Zener diode D814V indicated in the circuit can be replaced by any one that produces 8-10 V. For example, KS 182, KS 191, KS 210.
- If there are no 4 uF capacitors C5 and C50 of the K35-1000 type, you can take four 5000 uF or 4700 uF capacitors and connect them in parallel,
- Instead of an imported capacitor C3 220m, you can put a domestic one of any type at 100-500 microfarads 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 the circuits for connecting a transformer, transistors and connecting to a 12 V source, it is necessary to use large-section wires – the current here can reach high values (with a power of 400 W up to 40 A).
Pure sine inverter output
Converter circuits are complicated 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 a similar converter from ready-made boards. How – see the video. The next video shows how to assemble a 220 volt converter with pure sine. Only the input voltage is not 12 V, but 24 V. And this video just tells how you can change the input voltage, but get the required 220 V at the output.