Had a 78 go off like that yesterday somebody cunningly disguised the bypass cap fault by fitting the wrong type... S -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of David VanHorn Sent: 14 March 2007 06:20 To: Microcontroller discussion list - Public. Subject: Re: [EE] 0V...50V/40A low noise power supply On 3/14/07, Vasile Surducan wrote: > > I'm interested how is solved the weight problem for such supplies. > I guess one of the schematic choice is based on one or more switching > supplies connected in parallel followed by a low drop linear > regulator. Both the switching and the regulator should be > synchronised. Spread spectrum modulation of the switchers? I came up with that technique back in '91, tried to interest the boss in patenting it, but he said "It's not what we do"... :( That by itself dosen't really lower the noise, but it spreads out the energy so that it's less of a problem at any specific frequency. I had a fun incident about a year ago, with a switching supply at a VHF repeater. It happened to have some significant energy at 600 kHz, which is the split between transmit and receive at this repeater. When the VHF transmit energy mixed with the switcher noise in diodes somewhere, we got two noise products radiated, one was on the recieve frequency. Awful.. But linears aren't immune to oscillating, I've seen the 78XX series oscillate at about a watt, near 2 MHz, due to failed bypass caps. -- 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