That's pretty clever! I didn't think they were using 60 Hz transformers! On the front end inverter... We licensed a 75 watt DC to DC converter module from Cuesta Systems, one of the early manufacturers of UPSs for personal computers. This DC to DC converter took 12V in and output about 150VDC (or could be set up as a voltage doubler to do 300VDC). In our product, we connected this across the high voltage DC capacitor (or capacitors if there was a voltage doubler 120/240VAC input) of a 75 watt switcher. This powered our product when AC was lost. We also used the +5 and -12V outputs of the switcher to charge the Gel Cell battery, shutting down the charger when the inverter input current went up, indicating the loss of AC. A couple weekends ago I helped a 12 year old that I help with his projects wire one of those inverters up so he could play video games in the car on long trips. He'd already wired up a color LCD to it (he finds a lot of stuff dumpster diving). So, hearing about the inverter below brought back some memories... Harold ---------- Dwayne Reid writes: 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 ________________________________________________________________ Sign Up for Juno Platinum Internet Access Today Only $9.95 per month! Visit www.juno.com -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu