12-220V car inverter

About six months ago, bought a car. I will not describe all the upgrades made to improve it, I’ll dwell only on one thing. This is a 12-220V inverter for powering consumer electronics from the vehicle’s on-board network. Of course, it would be possible to purchase it at a store for $ 25-30, but their power was confusing. To even power a laptop with a current of 0.5-1 amps, which most car inverters supply, is clearly not enough. Choosing a circuit concept. By nature, I'm a lazy person, so I decided not to “reinvent the wheel”, but to search the Internet for similar constructions, and to adapt the scheme of one of them for my crafts. Time is very tight, so the priority was the simplicity and the lack of expensive parts.
 inverter circuit
In one of the forums, a simple circuit was chosen on the common PLM TL494 controller. 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 becausethat almost all the details could be taken from a computer power supply. For me it was very critical, because the nearest specialty store is more than 150 km away.
 for the device
Out of a pair of faulty power supplies of 250 and 350 W, the output capacitors were evaporated , resistors and the microcircuit itself. The difficulty arose only with high-frequency diodes for converting the voltage at the output of the step-up transformer, but here I was saved by old stocks. Characteristics KD2999V I was completely satisfied. Assembling the finished device. I had to assemble the device within a couple of hours after work, because the long trip was planned. Since time was very limited, I simply didn’t seek additional materials and tools. Used only what was at hand. Again, because of the speed, I did not use the printed circuit board samples on the forums. In 30 minutes, a custom printed circuit board was developed on a piece of paper, and its design was transferred to textolite. One of the foil layers was removed with a scalpel.On the remaining layer, deep grooves were drawn along the lines drawn. Using curved tweezers, it turned out to be the most convenient, the grooves were deepened to a non-conductive layer. According to the locations of installation of parts with the help of awls, it didn’t hit the photo, holes were made.
 fasten the elements
I started assembling with the installation of a transformer, lowering one of the blocks was used, he simply turned it over and instead of lowering the voltage from 400 V to 12 V, he raised it from 12 V to 268V. By replacing resistors R3 and capacitor C1, it was possible to reduce the output voltage to 220 V, but further experiments showed that this is not worth doing. After the transformer, in order of decreasing size, I installed the remaining parts.
the inverter is ready
 board bottom
Field effect transistors o decided to put on elongated inputs so that they are easier to attach to the cooling radiator.
 inverter bottom view
The result is such a device:
car inverter
There remains only the finishing touch - the mount of the radiator. There are 4 holes on the board, although the screw is only 3, it was just during the assembly process that it was decided to slightly change the position of the radiator for a better appearance. After the final assembly, we got the following: Tests. There was no special time to test the device, it was just connected to the battery from the uninterruptible power supply unit. The output was connected load in the form of a 30 watt light bulb. After it caught fire, the device was simply thrown into a backpack, and I went for 2 weeks on a business trip. For 2 weeks, the device never failed. Various devices were powered from it. When measured with a multimeter, the maximum received current reached 2.7 A.

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