2K25 Power Supply 4
By Vaughn P. McDowell
This Web site is under construction
Previously I built a
regulated 2K25 power supply that was totally switch mode: heater, reflector , and resonator using 12VDC input
power. Although it works very well it is noisy as expected requiring careful filtering. I wanted a second regulated klystron power
supply that wasn't as noisy as the switching transient type. Another technique not involving switching transients for power regulation
wastes power by dissipating power in the regulator. I resisted going this direction several times. I have several horizontal output
vacuum tubes that could be used for power dissipating regulators but I decided to think about this some more.
I have several IGBTs
in my parts bin that could handle the voltage OK but are designed for switching mode operation; in the past I have always used them
in the switching mode but not in analog mode. I decided to try it out; I was surprised how well it works
First of all I decided to check out the old schematics given in the Radiation Lab MIT series books. One of these is "Klystrons
and Microwave Triodes" MIT Rad Ser 7 ;pg 524 Fig. 18.18 which is reproduced below
Resonator voltage control
Next in my parts bin I found an unused still in the box Stancor transformer that I got from an auction (data sheet in the box):
I decided to try designing a solid state version of the above vacuum tube schematic above. The vacuum tubes were replaced with
1200 V IGBTs and obtained the remaining components from my parts bin. The finished device worked very well after tinkering with it
some; see schematic below:
C1-3 parts bin (removed from computer PS) 440uF 200V
C4-6 parts bin (removed from computer PS) 50uF 200V
R1-6 carbon film 470K 1/2W
This Web page is under construction; the home and other type buttons has not been added yet; I am still in the process of laying out my Web site
As an after thought A 300 volt switch should be used for this circuit such that when the power switch is first applied only
heater and repeller power is applied to the klystron. After warming up then the 300volt switch would be flipped to apply resonator
power afterward.
The finished prototype: Front View
The finished prototype: Rear View
Note the heat sink size. With the 2K25 it gets very warm but not hot; probably could use a larger sink and /or fan.