HV Nixie DC-DC Switching Power Supply

Michail Papadimitriou
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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 12V_dc input and gives an output of 150-250V_dc.

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 V_out and outputs 12V, but in this module, the output voltage is selected using the onboard potentiometer and it’s in the range 150-250V_dc. The maximum output current is 50mA @ 180V_dc.

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 RDS_on, the diode has to be fast M_ttr, 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 180V_dcvoltage output and 12V input. In the first case, the P_out= 8.1W while the P_in=10.96W, so efficiency is calculated at 47.75%. In the second case, the P_out= 4.1W while the P_in=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

Downloads

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Comments

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7 months ago

Reply

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

Reply
- admin
  
  It can be powered from 12V to 16.5V. This is fixed in paragraph.
  2 years ago
  
  Reply
ZF

Poor Layout
4 years ago

Reply
- Dustin Williams
  
  where is your design ZF
  4 years ago
  
  Reply
- Mike
  
  Design is completely updated. Thanks
  7 months ago
  
  Reply
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.
7 months ago

Reply
- Mike
  
  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?
  7 months ago
  
  Reply
spvoile

Hello, I am not an expert in mosfets but I wanted to know if I can replace the IRF740ASTRLPBF with IRF740STRLPBF (same reference without the “A”). The datasheet is quite similar and I don’t know if the difference matters for this application…
3 weeks ago

Reply
- Mike
  
  Yes, you can use it, as the basic characteristics are the same.
  3 weeks ago
  
  Reply