HV Nixie DC-DC Switching Power Supply

  • Michail Papadimitriou
  • 56537
    Views
  • moderate
  • Tested

Nixie tubes need about ~180Vdc to light up and thus on most devices, a DC-DC converter is needed. Here we designed a simple DC-DC switching regulator capable of powering most of Nixie tubes. The board accepts 12Vdc input and gives an output of 150-250Vdc.

Description

The module is based on the MAX1771 Step-Up DC-DC Controller. The controller works up to 300kHz switching frequency and that allows the usage of miniature surface mount components. In the default configuration, it accepts an input voltage from 2V to Vout and outputs 12V, but in this module, the output voltage is selected using the onboard potentiometer and it’s in the range 150-250Vdc. The maximum output current is 50mA @ 180Vdc.

The MAX1771 is driving an external N-channel MOSFET (IRF740) and with the help of the inductor and a fast diode, high voltage is produced.

MOSFET has to be low RDSon, the diode has to be fast Mttr, typically < 50nS, and capacitors have to be low ESR type to have good efficiency.

Precautions must be taken as this power supply uses high voltages. Build it only if you know what you are dealing with. Don’t touch any of the parts while in use.
Pay attention on the placement of C1 tantalum capacitor, as the bar indicates the anode (positive lead)

Schematic

Parts List

Part Value LCSC.com#
R1 1.5M – 0805 SMD C118025
R3 10k 0805  C269724
R4 5k trimmer SMD C132878
Rs 0.05 Ohm – 0805 SMD C149662
C1 100uF Tantalium SMD C444810
C2-C3 100nF – 0805 SMD C116832
C4 4.7uF / 250V SMD C88702
C5 100nF / 250V SMD 1210 C76688
IC MAX1771 SO-8 C407903
L1 100uH / 2.2 A C429814
Q1 IRF740 D2PAK C467558
D2 ES2F-E3 C145321
X1-X2 screw terminal Pitch 3.5mm C474892

Oscilloscope Measurements

Yellow is the MOSFET Gate voltage and Green the output high voltage (~180Vdc). We see that the transistor switches with a low frequency of 146Hz and with a peak gate voltage of 12.8V
zoom in to the above short pulses reveals 3x pulses with 48.7Khz frequency to the gate of MOSFET. Also, the peak to peak ripple on output is 6V
further zoom to the output ripple reveals some short ringing and the peak ripple voltage.



Efficiency

The module’s efficiency is calculated for two outputs currents (50mA and 25mA) at 180Vdc voltage output and 12V input. In the first case, the Pout = 8.1W while the Pin=10.96W, so efficiency is calculated at 47.75%. In the second case, the Pout = 4.1W while the Pin=5.52W, so efficiency is calculated at 74.54%. We see that for lower currents efficiency is greater than for the maximum current of 50mA.

Photos

If you would like to receive a PCB, we can ship you one for 6$ (worldwide shipping) click here to contact us

MAX1771 Datasheet

MAX1771

PCB

Comments

  • Francois

    Hi, what is the nominal and or maximal output current @ 180V ?
    And you say that i can be powered from 2, to 16.5V. Is it really 2v or 12V ?
    Thank you !

    5 years ago
    • It can be powered from 12V to 16.5V. This is fixed in paragraph.

      2 years ago
  • ZF

    Poor Layout

    4 years ago
    • Dustin Williams

      where is your design ZF

      4 years ago
    • Design is completely updated. Thanks

      6 months ago
  • Julian Lützen

    I think it’s better to have more clearance to GND at the HV Output at the bottom side of your PCB. It seems there is a distance of less 1mm to GND. I would let end of the GND polygon about 1cm before the HV Connector and connect the HV-GND Pin with a single strip to the polygon. It feels a bit safer this way.

    5 months ago
    • Thanks for your input. I agree with you and i will take this into consideration for the next version. If you are familiar with EAGLE, you can do this fix and share with us?

      5 months ago

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