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Guest bryan_v

help about inverters

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Guest bryan_v

i'm really confused if i can connect the inverter circuit found on your power projects to the UPS power supply because i want the output of my UPS project to be 220Vac. What should i do?

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If you want 220 instead of 110, you can use a voltage doubler circuit after the transformer to achieve this. This is just diodes and capacitors. Mixos has posted a diagram somewhere on this site with a schematic for voltage multipliers.

...or just use a different transformer that will give you the 220. This is all based on the ratio of turns between primary and secondary.

MP

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Guest bryan_v

Thanks a lot. It really helped me. My pre-design is tomorrow, so really thanks a lot....

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It is true as Ante has pointed out that the current goes down as the voltage goes up. However, if you have a sufficient amount of current to begin with, dividing will be no problem. The end user must make this calculation in the design. I would never do this as a bench power supply where you might come across current hungry circuits, but it is certainly feasible as a trick to bump up the voltage in a device that has sufficient current to absorb the loss. I would not go as far as to say that you will not have much useable current, though. This is dependent upon what you are putting into it. Which is directly dependent upon the VA rating of the transformer on this particular project.

MP

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What you would be saying is that if there is sufficient current, the voltage would have to be high. The amount of current is dependent solely on the capacitors. The voltages of the multiplier are what they are. When you load the multiplier, it takes more sections to get the volatge. In other words the load causes a drop in voltage somewhere. This is a my hunch. It's about the load contributing to an unideal situation.

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No. That is not what I am saying. Let me explain this in a different way. If the transformer is capable of putting out 120VAC at 10A (remember, we are talking about a step up transformer) then with a voltage doubler added to it, he would have 220VAC at 5A, which might still be sufficient for his design. On the other hand, if he has 120VAC at 1 A and he needs 1 A, then he is not going to be able to use a voltage doubler as it would then reduce his current to 500 mA.
These are not actual voltages nor are they a suggestion. They are simply numbers which are easy to relate. But I think that this example will put forth the idea.

MP

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What you are referring to is that the power in equals the power out. This is true. I constructed a voltage multiplier with some results. I replaced both of the bottom capacitors with larger ones. The load was connected final capacitor to ground. It turns out that you have to decouple to measure the ripple. The two larger capacitors worked fine. The ripple of one capacitor goes through to the other capacitor to the output. These are the DC sections with rippple. The two smaller capacitors pass the other signal but have trouble keeping charged. This results in a reduced peak voltage on the larger capacitors. But they stay charged and the ripple is reduced.

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