The controls for the motors for our winches have been using a big old, 60 hz. transformer, linear PS for over 15 years. It works fine. I'd like to switch over to an SMPS for the size and the universal input (about 85 VAC to 265 VAC). We use a microcontroller to turn on relays via NPN transistors. I'm looking at making everything 5 volts instead of the 24V/5V we currently use. The transistors, though, drop about .5 volts. I was hoping to use a ULN2003 to replace the individual transistors with a single chip. The ULN2003 (using Darlingtons) drops even more volts (about 1V for I=120 mA). So a 5 Volt PS won't quite cut it with the 5 volt relays I want to use.

I was hoping to find a vendor that could modify the AC/DC converter to deliver 6 volts instead of 5. I like the XP ECL15US05-P (20 W, 5 Volt). But for our quantities, about 400/year, they weren't interested. They suggested using the 9 volt model (and dropping the volts down a bit). That's a possibility.

I also tried Power Integrations. They have an Evaluation Board (Document RDR-839, Digi-Key PN 596-1530-ND) that I thought I could reproduce (with a bit different transformer and output components) to get my 6 volts. I was hoping they could send me some sample transformer cores and bobbins identical to what was used on the evaluation board. I haven't heard back from them since I mentioned we only use 400 pieces per year.

Any suggestions as to possible AC/DC SMPS vendors or another approach?