30kV DC Power Supply (homemade/DIY) using flyback and multiplier/tripler

This is my DIY high voltage power supply. It puts out up to 30kV DC and expects to be fed by a source giving 0 - 24V DC. The input is through banana plug connectors. I usually feed it using my homemade 24V power supply but as shown below, I've also used a wall adapter and a laptop power supply. Also below is a video showing step-by-step how to make this high voltage power supply along with some demonstrations.

Completed DIY/homemade 30kV high voltage power supply.
Schematic for 30kV high voltage power supply.

As you'll see below, the particular flyback transformer and multiplier for this power supply may be hard to find. An alternative is to go with a flyback with built in diodes as I've done here. The voltage will likely be lower though.

One modification I made is to make the FOCUS HV output from the multiplier (in this case also called a tripler since it triples the voltage) available. With the 30kV output wire I could get at low as 4kV but I wanted lower. So by making the FOCUS HV output wire available as an alternative I was able to get the range 1.2kV to 4.6kV.

It uses a flyback transformer to step the input voltage up to around 10kV AC and then feeds this into a multiplier which brings it up to around 30kV DC. I've looked at the output on my scope and it's fairly flat.

The flyback transformer

My flyback transformer was purchased from an online source which seems to be gone from the web. I actually purchased two of them but burnt out the first one when I tested without the multiplier hooked up yet. I was lucky enough to get the flyback schematics along with the flybacks and on the schematics it gives the resistance across various parts of the flyback secondary. Using an ohm meter you can easily test whether the secondary of the flyback is any good. After I ruined my first flyback one of the segments of the secondary measured infinity (the wire was clearly broken). So it helps to have those schematics!

For the primary and feedback coils of the flyback I removed the wire that came with it and put on my own wires as detailed in the diagram above and as shown in the following photo. After wrapping the wires into place and taping them with black electrical tape, I then coated the result with a few layers of black liquid electrical tape for durability, gluing the whole thing.

Flyback before adding the coils.
Flyback transformer without the coils for the 
      DIY/homemade 30kV high voltage power supply.
New coils as per schematic.
Modified secondary/output coils on the flyback transformer 
      DIY/homemade 30kV high voltage power supply.

The multiplier

The multiplier was ordered from a local electronics store and is NTE 521 from NTE Electronics, Inc. It has two inputs (hot and GND) and two outputs (focus and the 30kV output). NTE supplies a thick book of all their semiconductor parts (available at any store that specializes in NTE parts) and the schematic for the multiplier was in the book.

Many of the NTE multipliers can be used. A lot of them differ in the FOCUS output but the high voltage output is not affected by that.

Some have a 680 ohm resistor at the high voltage output and some don't. This won't make much difference for this power supply since if you expect the possibility of high power sparks (large spark gap building up a lot of power before sparking) then it's recommended that you put around 250 kilohms of at least 2 watt resistors at the output anyway.

Some are 5 step multipliers and some are 6 step. That means that the 6 step ones can start with a lower voltage input to get the same high voltage output as a 5 step one. But keep in mind they all have the same maximum continuous output rating under no load, 30kV at 2mA, except for NTE 559, which is 28kV at 2mA. The actual continuous output rating depends on what you give it as input and the maximum continuous output rating is the value you should not go over.

The following table has all the ones that I know of and that don't have extra POT, CTL or other inputs.

NTE part no. 680 ohm resistor? No. of steps
500A N 6
521 N 6
522 Y 6
531 Y 6
532 Y 6
NTE part no. 680 ohm resistor? No. of steps
533 Y 5
534 N 5
537 Y 5
539 N 5
     

It is fairly easy to make your own multiplier if you can't find one. I do that here to give another of my power supplies both positive and negative output with respect to ground and here to give that same power supply a lower voltage output.

Construction and testing photos

Top/front view. The weird clear plastic extension on top is because my flyback and multiplier were taller than I orignally expected. The 30kV HV output is the red wire at the top left of the picture.
Completed DIY/homemade 30kV high voltage power supply - top view.
Front view showing the transistors and the heat sinks. The input is via the banana plug connectors on the right.
Completed DIY/homemade 30kV high voltage power supply - front view.
Top view showing the insides. The multiplier is the beige rectangle near the back and the black thing just below it is the flyback.
Interior of the DIY/homemade 30kV high voltage power supply.
Side view. The round black thing is the secondary of the flyback. The multiplier is to the left of it.
Interior of the DIY/homemade 30kV high voltage power supply side view.
View from the rear showing the transistors better.
Interior of the DIY/homemade 30kV high voltage power supply showing the transistor wiring.

Click here for full details of where I got the heat sinks and how I mounted the transistors to the heat sinks.

IMPORTANT: It's recommended that if you might have high power sparks then you should put around 250 kilohms of resistance with at least a 2 watt rating at the output to protect the power supply from the high current of the spark. A high power spark usually comes from a wide spark gap. I damaged transistor Q1 this way by forgetting to put this resistance. I usually put it on the ground return side since it may involve uninsulated connections. My video below talks about how I found and replaced this damaged transistor. If you're curious about what I was doing when I damaged this transistor see this youtube video of mine, Star Trek Enterprise Model with Ion Propulsion added. The damage actually happened after the video was made and I was playing around some more.

2 x 220 kilohm, 2 watt resistors = 240 kilohms, 2 watts of protection.
240 kilohms of resistance for current protection from sparking.
I attached a small round brass ball to the end of the HV output wire. Here the end of the output wire is sitting taped to a roll of masking tape to keep it off the floor. The red tube thing is a Fluke 80k-40 40kV high voltage probe which I can feed into my multimeter to measure the voltage.
Close-up measuring the output of the DIY/homemade 30kV high 
      voltage power supply using a Fluke 80k-40 40kV high voltage probe.
My multimeter is on the right. To the left of it is my 24V DC power supply. The output of the 24V power supply is feeding into the 30kV power supply which is on the left. On top of the 24V power supply is a Variac. In this picture I am measuring the output of the entire setup.
Measuring the output of the DIY/homemade 30kV high 
      voltage power supply using a Fluke 80k-40 40kV high voltage probe
      hooked up to an analog meter.
As I turn up the voltage using the Variac, the first reading I get from the 30kV power supply is this one, around 12kV. The meter is on the 30V scale and is showing 1.2V (12,000 volts / 1000 (due to the HV probe) / 10 (due to being on the 30V scale) = 1.2 volts). If I then turn the voltage down gradually I can actually get less voltage. I think I went as low as 4kV at one point. Then it just drops to 0.
Voltage on the analog meter when measuring the output of the 
      DIY/homemade 30kV high voltage power supply.
Here it is at the highest I was willing to turn it up, 28kV, for fear of damaging something.
Highest voltage I was willing to go to on the analog meter 
      when measuring the output of the DIY/homemade 30kV high voltage 
      power supply.
Showing the arrangement for using the 1.2-4.6kV FOCUS wire. Notice that both wires have brass balls attached to them since both have to be discharged after use.
Making use of the FOCUS from the voltage multiplier part of the
      DIY/homemade 30kV high voltage power supply.

WARNING: This power supply can produce harmful or lethal voltages and currents. Always discharge the power supply to ground after turning it off and before going near it. When making a corona, ion wind, sparking and/or arcing it produces ozone, which is harmful to your health, so use in a well ventilated area.

Feeding it 0 to 24 volts

As the above circuit diagram shows, this needs a 0 to 24 volt power source to feed it. I usually use my homemade 24V power supply but as the photos below show, I've also used a small wall adapter and a laptop power supply as well. The wall adapter has a switch for selecting the voltage, from 1.5V to 12V. The laptop power supply puts out only 20V and keeps it that way, even if I plug it into my Variac and try to control the voltage that way.

Homemade 24V power supply as 1st stage.
Using my homemade 24V power supply as the 1st stage for
      my high voltage generator.
Wall adapter as 1st stage.
Using a wall adapter as the 1st stage for the high voltage
      generator.
Laptop power supply as 1st stage.
Using a laptop power supply as the 1st stage for the high voltage
      generator.

Video - How to Make 30kV High Voltage Power Supply

Here's my video showing step-by-step how to make this power supply. I also demonstrate it flying a lifter/ionocraft both using my homemade 24V power supply as the first stage and using a laptop power supply instead, which more people have access too.

Video - Fixing my High Voltage Power Supply

While experimenting with ion propulsion added to a Star Trek Enterprise model I broke this power supply for the first time. I could have avoided it if I'd followed my own advice and put around 250 kilohms of resistors (2 watts) in series with the output, but I didn't and ended up damaging one of the transistors.

The following video shows my steps in finding and fixing the problem.

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