Nixie tube is an electronic device for displaying numerals or other information using glow discharge. A potential difference is applied between two electrodes in a glass tube containing low-pressure gas. The flow of electric current through the gas makes plasma. This phenomenon is called glow discharge. First introduced in 1955, the Nixie displays are legendary. The retro nixie displays had a single anode, multiple cathodes that are electrodes shaped like numerals 0-9 stacked on top of one another. Applying the power to one cathode will make that numeral glow. The tube is filled with a low-pressure gas that creates an orange glow discharge. These legendary displays, however, are no longer mass-produced, and they need high-voltage drivers.
There are still some places on the Internet where one can get these retro nixie displays. The high-voltage display drivers are, however, hard to find. The high-voltage driver consists of a DC-DC step-up converter which will step up the voltage level from around 5V to 100-230V.
About Step-up Converters
DC-DC step-up converters or boost converters generally consist of a diode, a power MOSFET, and two energy storage elements: an inductor and a capacitor.
When the switch is open initially, there is not much resistance, so high current flows through the inductor. The energy in the inductor is due to the magnetic fields. When the switch is closed, the impedance in the circuit increases and the current will be reduced. The magnetic field previously created will be reduced in energy to maintain the current towards the load. The polarity of the inductor will therefore be reversed and will create another voltage source in series with the input voltage supply. If the rate of switching is fast enough, the voltage will be higher than the input voltage, and this boosted voltage can be controlled by controlling the duty cycle of the switch.
Nixie display drivers also sometimes use flyback converter topology. It provides galvanic isolation between the input and the output with the help of a transformer.
About NCH6300HV HV Power Booster
NCH6300HV high voltage DC-DC power booster is a compact step-up DC-DC converter. It is the updated version of the popular NCH6100HV by Omnixie. As it is a switching converter, its efficiency is high, and heat generation is low. This converter supports input voltage from 3.7V-15V DC and converts it into an output voltage of 100V-230V DC (100mA max @170V). The output voltage is adjustable by a precise potentiometer onboard. The board can be powered by a Lithium battery or by connecting to a USB port as it supports an input voltage of as low as 3.7V. The module can be completely turned off by controlling the SHDN pin for better safety and maximum energy conservation. The board’s output voltage and safety features are perfect for driving the retro nixie displays, as well as other displays like VFD tubes, Magic eye, etc.
The module comes with the PCB terminals and pin headers. Two connectors are present, a 3-pin connector for input and a two-pin connector for the DC output. The pin pitch is 0.1″, therefore compatible with standard perforated boards and breadboards.
The product was successfully funded on Kickstarter on Dec 6th, 2020, and is now on sale at the Omnixie store.