This is a multipart series on how to design an efficient and modern high voltage nixie power supply, from the idea to shipping it to customers worldwide.
- Part 1: Idea
- Part 2: Design & Simulation
- Part 3: Making a prototype
- Part 4: More prototypes!
- Part 5: Sending for Assembly
- Part 6: Efficiency
- Part 7: Production Run
- Part 8: Selling & Conclusion
The idea to build a good power high voltage DC/DC converter simply comes from my own need for it. Anything dealing with power management that comes from dodgy Chinese source is a potential for disaster. There has been some dramatic incident in the 3D printing community for instance. Add to this the high voltage element and I honestly would not leave for one second a nixie clock that is powered by these modules unattended.
Luckily for me, no drama happened: the power supply just crapped out without warning.
So how to build a quality power supply capable of boosting up to 170V?
First and foremost let’s not reinvent the wheel. I like to think that there has to be a solution for this problem that is supported by a big semiconductor company. In the case of nixies though, not so much! If you study old designs, they’re all powered by mains and a big old transformer. A solution that is not hobby friendly.
That being said, there is at least one modern application that needs high voltage DC/DC transformation: capacitor chargers. They are typically the main source of power for photography using flash.
So after doing some more research, I found two key components that would fit the bill:
The power transformer
There are surprisingly not a whole lot of “stock” transformers out there, most of them are ordered custom made. However I dug up some interesting beauties from Coilcraft doing research:
I quickly found out that to generate high voltage, all semiconducators companies use a flyback transformer. No one uses a typical boost converter. The boost ratio is too great to have something safe and stable.
A transformer with 3/24V input used to generate 300V? Surely it can do 12 to 170V easily then right?
The switching regulator
Coilcraft mentions LT3750 / LT3751 which are capacitor chargers, not switching regulators. They work on the same principle but have a few goodies like telling you when the capacitor is fully charged so that you can stop pumping high voltage.
Digging around though I came across the LT3757, a real switching regulator which includes a reference design for… a high voltage power supply!
The idea is all there, we are in business!
- LT3757 Boost, Flyback, SEPIC and Inverting Controller by Analog Devices
- Flyback Transformers for Linear Technology LT3750 / LT3751 by Coilcraft