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Back almost 10 years ago I constructed a general purpose regulated power supply with adjustable voltage range from about 60 to 900 VDC. At that time I roughly measured its power out to be approximately 15 watts which was good enough for my purpose. At that time I needed several power supplies of this type in a hurry so I designed it based on what I had available in my parts box. I didn't have any 494 type switch mode controllers so I used what I had pleanty of: NE555 timers, TL 082 analog amps , IGBTs, UF1007s, and computer power supply transformers that were extracted from their circuit board. I had the idea if operating them backwards from how they were intended. Being in a hurry I wasn't concerned about IGBT short circuit protection because of their intended use. I built lots of these for general purpose use; since then they have been used in various projects that I intend to add to my Web pages. For this reason for completeness I have included this type power supply. If I decide to build more of these I plan to redesign then using 494s.

7 NOV02A P1"; see photos below. Its intended purpose was for CCPS or charging capacitor energy storage in the range of a few hundred to about 800 VDC. A power supply inhibit was included when it was desirable to minimizing the power loss that occurs when using large resistance values for the charging resistors; ie allow one to use low resistance values to up the PRF.

In 2005 I was running out of these power supplies and decided trace out the schematic to ensure accuracy and enhance some of its physical layout; the following photos include sketch drawings and finalized circuit board layout.

I never got a chance to take this rough sketch of the up dated schematic into a drawing; I have mixed feelings about doing this since I am having thoughts of designing a much superior one using a 494 SMPS controller chip.