At 04:46 AM 2/18/03 +0000, Harold Hallikainen wrote: >Speaking of UPSs and inverters, what's the current technology on the DC to >AC conversion? Are they using some high frequency PWM to simulate the 60 >Hz allowing for smaller magnetics? I built an inverter about 40 years ago >with a big 60 Hz transformer that was especially for that purpose >(included feedback windings to drive the switching transistors). Seeing >the low cost and small stuff available now, I wonder how work. The little Statpower inverters that I have looked at (300 VA and smaller) use a nice little 140 Vdc dc-dc converter followed by a H-bridge operating at 60 Hz. There is significant dead time in the 60 Hz transitions so as to create their "modified sine wave" output. This results in the peak and average voltages being similar to those obtained from a true sine wave source. They are inexpensive and reliable little units. I purchase the 300 VA units and tap into the 140V supply for a couple of products - its by far the cheapest 12V - 140V dc-dc converter that I could find. dwayne -- Dwayne Reid Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 19 years of Engineering Innovation (1984 - 2003) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu