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Hey now! In defence (sort of) of cheap chinese crap, start taking a close look at your "good" inverters and other power electronics you buy at the store and pay good money for.
Around half are chinese made, of the remaining half most of them will be from tiawan, indonesia, the phillippines, or some unhread of country. And the one or two you could buy that are american made will probibly have a factory recall in the first year or so due to a manufacturing flaw.
Sad, but take a good look at all the brand names out there and where their product is actualy made or who its made by and where their stuff comes from.
You may just be surprized and a little disapointed in your beliefs. I know I was when I started doing research on where things come from.
Since you are building your own here is some things to help you out.
Its a edited down reprint of something I wrote for another thread simmilar to yours. It could be useful information.
Points of recomendation:
1: I would seriously consider runnng a 5 to 10 uf PFC capacitor on the output side. This will round off the square wave and give you a more accurate voltage reading. It wont be exact but it will be closer.
2: When the switching devices turn off they will get a large voltage spike that needs to be handled some how. That magnetic field energy in the transformer has to go some place durring that off time between each half of the driver circuit cycles or it just builds up voltage where you least want it! Namely at the switching devices themselves.
3: A lower voltage AC capacitor of perhaps 1 - 3 uf per running amp in series with a 10 ohm or so resistor connected across the ends of the primary will greatly help protect the Mosfets.
The PFC capacitor will take some of that spike and help recycle it back into the system creating a LC tank effect and greatly reducing the idle current as well. But still, the primary is going to get a spike that could be fairly high when there is no actual load on the output.
I am just guessing at the capacitor and resistor values do to the fact I do not know what VA rating and core saturation values your transformer may have. But I do know you are still far better off with them than without. reguardless of if they are sized exactly correct or not.
I have built enough homemade "DR. frankenstien" inverters to know these added components will greatly help in the overall duribility and running efficiency. It is still a crude unregulated design but it does have potential. And I would shoot for a 15% over line voltage number at no load. You are not going to get away from the voltage sag with load increase on this type of circuit.
I would not be the least bit surprized to see it drop to 15% under voltage or more at is maximum rated capacity too!