1000W & 1200W Inverter On The Cheap{.pdf

I have made an effort to improve upon the appearance of a couple of these pages, specifically the circuit

diagrams. The original magazine is long gone and these photocopied pages seem to have all sorts of odd

marks on them. You will find that this article is very descriptive and will certainly assist anyone who

wishes to design their own version of this system. This happens to be the first design I have seen, other

than my own, that features the use of power mosfets to maintain a low impedance on the output by

shorting the primary during the 'off time' of the power driver stages. the low impedance afforded by this

approach greatly improves efficiency when driving inductive loads and keeps the transformer's noise

levels down also. By the way - the transistors used in the 'Power house' unit, though good, are now

somewhat outdated. I would like to suggest that 'HRF3205' devices be used in place of the 'IRF540'.

The new devices have a current rating of 100A - as opposed to the 25A rating of the 'IRF540s'. This

means that fewer devices can now be used - say 6 devices can now replace the 14 that make each driver

side, and 2 devices can replace the 4 that form the switched 'shorting' stage. I have designed and built a

small number of inverters, but never made the effort to write them up in anything like the standard of

this article. You are welcome to see my present design, called 'MiniVert', it operates on 12V and delivers

600W at 230V and 50Hz. At present I am working on a design for a sinewave inverter, it employs a

bandgap technique using a wind w detector to follow a reference sinewave and drive power mosfets with

digital pulses to create a 230V sine wave. This has been a fairly successful, so far providing 200W into

all sorts of reactive loads without showing signs of trouble. Like my other designs, this one is able to

maintain a low output impedance by comparing the outgoing wave form with the reference and causing

appropriate timing changes to keep things sweet. There is a fair bit of work left to be done here - but I

will let you know how it goes.