Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!rutgers!sri-spam!ames!ptsfa!ihnp4!cbosgd!cwruecmp!neoucom!wtm From: wtm@neoucom.UUCP (Bill Mayhew) Newsgroups: sci.electronics Subject: Re: high voltage Power Supplies Message-ID: <628@neoucom.UUCP> Date: Sat, 18-Jul-87 23:43:23 EDT Article-I.D.: neoucom.628 Posted: Sat Jul 18 23:43:23 1987 Date-Received: Thu, 23-Jul-87 03:45:07 EDT References: <1811@ttrdc.UUCP> <100500016@datacube> Organization: Northeastern Ohio Universities College of Medicine Lines: 36 Summary: Switchers aren't as bad as you think OK, I'll conceede that if you want to perform linear regulation at tube type voltages, a tube for the pass element is a good idea. If you accidentaly short the output cathode to ground, you've a few seconds to rectify (*a pun *) your mistake, rather than the microseconds you'd get before you send a transistor off to stick in the ceiling. A 6L6 is an easy to get tube that makes a good pass element. A pentode is would be a good idea to isolate your 0A2, 0D2, or whatever reference you use. There are some VR circuits in the old RCA receiving tube catalogs and probably old ARRL ham radio books. As far as switchers go, they aren't too bad if you design carefully so that it can operate in the MHz region, rather than KHz. Any noise wouldn't be audible. With a switcher, you can use something like a .1 uF fancy "audio grade" capacitor to get all the filtering you need. It's getting downright difficult to get decent n hundred uF capacitors* that are required for 60 (120) Hz operation. 60 Hz magnetics weigh a lot. Of course, building RF switchers calls for very careful design, and care at bypassing leads, etc. I think I'd put a linear VR circuit after the switcher for extra insurance. * at least, not at tube voltages! We have RF switchers in medical equipment that amplifies uV signals and don't have any noise trouble. Using an RF power supply is required so that ~5 cm. air gap can separate the primary and secondary of the *air core* power transformer. This baloney is necesary for "patient safety".-- although our patients are lab rats. Bill Mayhew Division of Basic Medical Sciences Northeastern Ohio Universities College of Medicine Rootstown (what a name), OH 44272-9989 USA phone: 216-325-2511 (wtm@neoucom.UUCP ...!cbatt!neoucom!wtm)