Upcoming Trade Shows CHINA HI-TECH FAIR 2008 Location: Shenzhen Convention and Exhibition Center Date: 12-17 October 2008 Booth Number: 2C52 Contact : Mr. Gordon Chen
Switching Power Supply: Junction-Path Shorts(4 of 4)
On the Web
To date, I have found no information on this subject on the web.
References
I learned about current surges through back-biased junctions the hard way (personal perspective above). The only reference I've seen related to these techniques is a 1970-era General Electric transistor manual that gives the ground rule that resistance should be placed in two of the three leads of every transistor. There is a literature on pulse overstress testing and rating of semiconductors that also may contain relevant information.
Switching Power Supply: Junction-Path Shorts(3 of 4)
Personal Anecdote
The first power supply I ever designed for production was a transistor series regulator. Out of the first 100 fielded, 18 failed within three months. The problem was a path through semiconductor junctions that depended on back-biased junctions for impedance.
In an all-parts change, a 10 ohm resistor was added into the collector of a transistor to break up the path. With several thousand units in the field for the ten year life of the product, there was never another failure.
Switching Power Supply: Junction-Path Shorts(1 of 4)
Problem
Small signal semiconductors and integrated circuits fail due to paths between power sources or power sources and ground that have insufficient resistance or inductance, or rely on back-biased semiconductor junctions to limit current.
Power Supply Output Filter Design - Overshoot(4 of 4)
Personal Anecdote
During the 1970's, a major semiconductor vendor released a widely distributed application note on the design a switching-mode power supply. As I recall, it was for a 5V, 12A, forward converter. Their recommended output filter resulted in a 15V overshoot on the 5V output when the 12A load was removed. No overvoltage protection was shown. This degree of overshoot would destroy most logic circuits for which the supply was intended, or worse, severely degrade their reliability without destroying them.
Power Supply Blog 
