[Elecraft] Regulated PS load step overshoot

[Howard Hoyt]

Hi all,

On Jan 21, Ted, KN1CBR posted regarding a suspected supply transient 
problem damaging his K2.  This post encouraged me to check the response 
of different power supplies to a load step from high to low load.  This 
is a situation where the internal regulator in the supply can 
potentially overshoot due to one or a combination of several factors: 
poor regulator design, DC lead inductance, DC lead resistance and others.

The results of these load step tests are now posted on our site:
https://proaudioeng.com/products/pae-kx33-low-rfi-ac-power-supply/
Select the 'Test Results' tab.

In general most name-brand supplies have minimal overshoot and decent 
regulation, but some very inexpensive switching regulators have terrible 
performance.  I would never suggest running expensive electronics on a 
cheap unquantified switching power supply...or linear supply for that 
matter.  A common failure mode for linear regulators when overloaded or 
overheated is shorting of the pass device.  Without a crowbar circuit 
installed this will of course put full unregulated voltage at the output 
terminals.  Conversely, failure of a power device in a switching 
regulator will cause the output to drop to zero.

Cheers & 73,

Howie - WA4PSC