Any experience designing 555 switched mode power supplies?

[frequencycentral]

I've got a few ideas for little tube amps which I want to power using methods other than a big (and dangerous) PT. You may have seen them:

This one uses 5672 submini pentodes and a MAX1044 for the B+. The maximum rating for the 5672 is 90 volts.
http://www.diystompboxes.com/smfforum/index.php?topic=73222.0

This one uses a 12AU7, and I'm about to start messing with 6111 submini using a similar topology. I'm using the MAX1044 for the B+ here too, but these tubes can handle a much higher voltage than the 5672.
http://www.diystompboxes.com/smfforum/index.php?topic=73317.0

So I'm thinking maybe that I should try a 555 switched mode power supply. I found one here, used in a similar application, which the designer says is not quite 100% safe:
http://www.jjs.at/electronic/class_a_subminiature.html

So any help, advice, links etc so I can build a safe 555 switched mode PS? Thanks in advance.

[dwan]

I guess you've already found this, although it seems made to output low voltages.

[R.G.]

Using a 555 for a switched mode power supply is how we (= us EE power supply designers, at the time) used to do things before there were custom chips for this. It requires a lot of circuitry to get the functions you really need, even though it can be made to work.

I didn't feel like doing the amount of google searching that it will need, but somewhere there is an 8-pin DIP package flyback-mode power controller that will do your up-verting and do a good job of it with only a switching transformer and an external MOSFET, perhaps not even that.

Voltage multipliers, as you'll need to run a diode-capacitor multiplier off a 555 with no transformer, get into real practicality problems when you have to deliver any significant current. It can be done, but you have to do a lot of really touchy design work and spend money on lots of components.

Try a search on "flyback switching controller" on google. You'll probably find something from Fairchild, TI, ST, or ON Semi. It will require winding a small flyback transformer, but this is fun.

OK, if you're a power supply designer, it's fun. To normal people it's somewhere between boring and torture.  

[Ice-9]

I came across an 8 pin chip that is used in flyback psu's to get high voltages. The chip i was looking at is the UA3843, When i was tinkering with this idea i came across a schematic and datasheet. The schematic i found was able to deliver 300v and used minimal components, a mosfet being used in there. I'm sure from memory this was called a 'TOPSwitch flyback'. I just cant recall where i found this info.

[R.G.]

The uA38xx series is one of the ones I was thinking of. The only thing to be cautious about is that some of these will not start and run from a 9V supply if that matters to you. They have undervoltage lockouts, so read the datasheet carefully.