200-450V variable power supply (with 15V input). The circuit is suitable for powering nixie tubes or charging capacitors.
This is a working device, but since there is always room for improvement, it is tagged as "work in progress".
The circuit is basically a "mashup" of a boost converter described on ladyada.net/library/diyboostcalc.html and example circuits described in the 555 datasheet.
The .T3001-file is a Target3001 project file containing schematic and routed two layer PCB layout.
The Gerber.zip contains all necessary files for PCB production (if you want to order a PCB from a manufacturer)
The output from the boost converter is unregulated, so if you want to use the circuit for anything else than charging a capacitor bank, you should add an electrolytic capacitor in parallel with the output.
Warning: Some capacitors are capable of storing lethal amounts of energy for a very long time (several hours/days). Be very carful if you plan on using this as a charging circuit.
The device can be powered by a 5-15V power supply.
Component list: D1: UF4007 diode
D2: 1N4002 diode
R1: 2,2k resistor
R2: 22 k resistor
R3: 1 k trimpot
T1: IRF840 MOSFET
L1: 170 uH inductor
C1 4,7 nF capacitor
C2: 10 nF capacitor
C3: 47 uF electrolytic capacitor
IC2: 555 timer
The design is rather generic. If you want to experiment, you can (In addition to substituting the inductor) replace C1 to modify the frequency range. R1/R2/R3 controls frequency and duty cycle.
Update (18. May 2012): I have been using this circuit for charging a 450V/6000uF capacitor bank. To minimize the charging time, I removed diode D2. This increases the duty cycle of the 555. In a charger scenario, the initial current will most likely fry D1, and then the mosfet if you don't add a high wattage current limiting resistor on the output( I used a 47 ohm / 5W resistor). It is also a good idea to add a heatsink to the mosfet.