> I use switchers for all my 48V to 5V or 12V converters for years now. Works like a dream. I have been afraid of switchers because I thought they would cost a lot more than good ol' 78xx linear regulators. What is the price premium for a switcher including all those inductors over a plain linear regulator? Obviously the switcher is more efficient, and some people goota have that efficiency. My stuff is all going in 1500 watt ovens, so efficiency is not an issue, just cost and reliability. --Lawrence "D. Schouten" Sent by: pic microcontroller discussion list 08/26/02 03:47 PM Please respond to pic microcontroller discussion list To: PICLIST@MITVMA.MIT.EDU cc: Subject: Re: [EE]: Crowbar protection > I haven't had to use a pre-regulator before my regulator in anything but a > precision benchtop power supply. I wonder if there is a cheap automotive > 5V regulator that will handle 48V DC input voltage without complaining? You could use a TL783 from TI. This regulator handles an input/output differential voltage of up to 125VDC. However, it would cost you an additional two resistors too since it is an adjustable regulator. But still, stepping linearly down from 48V to 5V would at least require a small output current to keep dissipation reasonable. I use switchers for all my 48V to 5V or 12V converters for years now. Works like a dream. Daniel... > > Russell McMahon > Sent by: pic microcontroller discussion list > 08/25/02 07:28 AM > Please respond to pic microcontroller discussion list > > > To: PICLIST@MITVMA.MIT.EDU > cc: > Subject: Re: [EE]: Crowbar protection > > > > Since the failure in shorted mode is so rare, my detective instincts > lead > me to suspect something else - > > Someone else noted the need for reverse voltage protection diodes. These > are > covered in the data sheet. The need arises when the input voltage falls > much > more rapidly than the output and the output cap discharges "backwards" > into > the regulator. This can occur if the input is shorted suddenly OR if the > output load is small relative to the output cap provided while the input > can > discharge rapidly when turned off - either because there is little or n > input cap or because some other load rapidly discharges the input cap. > > In these cases and others the LM293x family are specifically designed to > survive. Their forte is automotive situations replete with alternators, > car > batteries, inductive loads and numerous somewhat silly people wielding > jumper leads and reverse connected batteries. I strongly recommend this > regulator family. (Standard disclaimer, no shares in NatSemi or other > financial etc interest yada yada). > > You said 7805 - hopefully NOT a 78L05 - the TO92 miniature version. These > do > die for reasons that I have never bothered to determine - not using them > is > easier. The TO220 version costs less usually and the TO220 dissipates more > power when unheatsunk than the TO92 pkg. > > > RM > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics