# 9 V to 400 V DC-DC converter

I need to build a Geiger counter power supply circuit that will provide a 400 V DC output out of one of those 6LR61 9 V batteries. I thought about using a 555 timer to produce a square wave, feed it into a 1:45 transformer and then filter out the output, but I have no idea about what frequency and how many primary and secondary windings to use, and whether it would work at all.

update:

OK, thanks everyone for your effort but I guess I'll just go with a 555 inverter circuit like this (sorry for the watermarks), with custom transformer and a filter on the output.

• Try TI webench for inspiration. Jun 3, 2018 at 9:24
• Thanks for the idea, but webench didn't find anything. The ratio is probably too high. Jun 3, 2018 at 9:31
• How much current does the counter need? For very low current, a modest transformer step-up followed by a cascade might be suitable. For higher power a flyback is a good choice. With a 6LR61 you're not going to be able to get much power anyway. Jun 3, 2018 at 9:35
• The tube won't need much current, but the thing is that I don't posses the needed knowledge to calculate all the numbers, and I didn't find any close example of the power supply. Jun 3, 2018 at 9:42
• @Thatguy good literature available: en.wikipedia.org/wiki/Voltage_multiplier Jun 3, 2018 at 10:23

## 1 Answer

Here's a reputable one that runs from 5 volts and uses an inductor to get initial voltage magnification then a cockcroft-walton multiplier: -

Maxim article that gives more detail. Use a voltage regulator to drop the 9 volts to 5 volts and because you are using a battery I'd urge you to use a buck regulator to prolong battery life.

There is also this that runs from a 555 timer and uses an LT700 audio transformer: -

Full details here. But google really is your friend on this and you can find many images of circutis on-line.

• Can I ask a question ? Why they use 1N4148, its max reverse voltage is only 100 V ? Jun 3, 2018 at 15:35
• @LongPham Each diode (in the C_W multipler) only sees a fraction of the overall output voltage. Jun 3, 2018 at 18:25