The behavior sounds like that of a clamper, which employs a diode, capacitor, and second voltage source to shift an AC source by a certain DC level, in this case about +20 volts. I suppose it's possible that the cap, diode and 5V output on the output side of the regulator are combining to clamp the input signal up 20V. I'm afraid I can't tell you how to fix this problem though. If this is what's going on, it might not be such a problem since I think you would still have 5VDC for the output. I could be wrong though. Daniel Imfeld ----- Original Message ----- From: "Jai Dhar" To: Sent: Saturday, February 08, 2003 8:45 PM Subject: [EE]: Rectifier Question > Hello all, > > For those of you who knew about my little I2C problem that I had, I have > officially given up on it until I receive my new sensors from Microchip - in > which case I will try again :-) Anyway, working on the other parts of my > project, I started on getting my MAX787 5V SMPS regulator working. It's a very > simple connection, so it seems, according to the data sheet on maxim's web > site (http://www.maxim-ic.com/quick_view2.cfm?qv_pk=1271). I am using their > EXACT circuit, and getting a nice solid +5V output. The problem is at the > input from the rectifier. Basically, I have a transformer that goes to a full > wave rectifier, and then the positive part of the rectifier is fed into the > input of the regulator. As soon as I connect the input of the regulator to the > output of the rectifier, the voltage at the input jumps up to ~45V. Without > the regulator connected, the voltage at the output of the rectifier holds at > ~25V. Checking the negative side, with no regulator connected, it gives a - > 25V - so it's symmetric, which it seems fine. But as soon as I connect the > regulator, when the positive swings up to 45, the negative becomes about -5. > How come the voltage swings like that? Is this normal? Is there anyway I can > control it? > > Thank you, > > Jai > > > > ---------------------------------------- > This mail sent through www.mywaterloo.ca > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.