Reasonably easy. Look up a 3842 you need two chokes in the 500uh to 1mh (something on and ETD25 core size) the values are not important. You can make a SEPIC converter very wide input voltage good stable output voltage no isolation. Feed the 3842 from the output via a diode and use a 1mA bleed from the supply side to start it. -----------L---------C-----------D-+----- +ve op | | 3842 FET D L S | ----------------------------------------- -ve op It's the power section only but I use this basic circuit from 18V to 300V dc input at powers up to about 50W it works as step up or step down and it also works with almost any values. Look up 3842 and set up similar to the flyback example but changing the power circuit to the above (crapppy ascii) and it will work. Use something like a 1u/160v poly or a class x as the coupling cap and a 150nS diode (at least 200v). Rgds Steve -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of Mike Hagen Sent: 15 January 2006 19:49 To: Microcontroller discussion list - Public. Subject: Re: [OT] DC-DC Voltage Converter - How to start 40-60 WATTS ----- Original Message ----- From: "Mike Hagen" To: "Microcontroller discussion list - Public." Sent: Sunday, January 15, 2006 11:45 AM Subject: Re: [OT] DC-DC Voltage Converter - How to start > Yes, I agree with Denny. > > Try a switching supply for 110-220. They make DC out of the AC in and > then > convert it down. > Try finding a 40-60 one that outputs 15 Volts (or 12 and trim it up)? The > 110V mode usually goes down near 90-95 V? > You can even take the metal cover off and bypass the full wave rectifier > (to > save voltage drop) or tweek the output voltage. Jameco has a lot to look > it? > > Mike, WA6ISP > > ----- Original Message ----- > From: "Denny Esterline" > To: "Microcontroller discussion list - Public." > Sent: Sunday, January 15, 2006 11:09 AM > Subject: Re: [OT] DC-DC Voltage Converter - How to start > > >>> Here asking for some help in the design of a DC to DC Converter. >>> I have a solar panel with 96 to 100 VDC @ 1.1Ah without load, break >>> point at 97 VDC and down to 60 VDC @ 0.9 Ah with load. >>> >>> The idea is to make a DC-DC converter from an input of 97 to 60 VDC to >>> an output of 14 VDC more or less at 3Ah, this output will be used to >>> charge a battery system. >>> >>> Can be possible to do this converter without any inductive device? >> >> Not effectively, but if the question is "is it possible to build a DC-DC >> converter without inductors" the answer is yes. Switched capacitor >> converters are commonly used for small boost converters (think MAX232). I >> guess it would be _possible_ to reverse the general process, that is >> charge >> several capacitors in series and discharge them in parallel. But I've >> never >> seen a switched capacitor converter rated for more than a few milliamps. >> So >> yes, it's _possible_, but I can't recommend it. >> >> >> Here's an off the wall idea- what about a regular switch mode wall wart / >> power brick? The one running my LCD monitor as I type this is rated as 4 >> A >> @ >> 12V output, 90-240V AC input. Granted that's an AC input but the way >> these >> things work is they rectify and filter the input voltage before it goes >> to >> the switching stage. If you just tapped the output of your panel to the >> internal HV DC rail... >> 60V with full load is a little low, but it's worth a try >> >> -Denny >> >> -- >> http://www.piclist.com PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> > > -- > http://www.piclist.com PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > > -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist