Starting from a 30 volt power supply this high voltage converter circuit can deliver a voltage between 0 to 3 kV (version 1) or from 0 to 10 kV (version 2).
IC 4011 gates N1 … N3 are connected as astable multivibrator that commands the Darlington T1/T2 with an rectangular impulse of 20 kHz.
The transistors cannot be brought to saturation because of the low current that goes through them which will result in a very short block period. The rapid blocking of the transistors will produse an impulse of almost 300 V in the transformer’s T1 primary winding. This voltage is multiplied by the numbers of turns from the secondary winding.
For the first version it uses a monophased rectification. The second one uses a cascade rectifier from an old TV set and it delivers a 3 times higher voltage.
Version 1 and 2 of the voltage converter
IC2 LF355 regulates the output voltage by comparing the P1’s voltage with that from the common point of the voltage divider R6/R8 or R7/R8. If the output outreaches the established voltage level, IC2 will reduce the supply voltage from the output through T3.
The most important part of the high voltage converter is the transformer. You may use a variety of cores E, E+I or ferrite with 30 mm diameter. The core must not have any air gap and a value for Al of 2000 nH is pretty good. The primary winding consists of 25 turns of 0.7 … 1 mm enamelled copper and the secondary winding consists of 500 turns of 0.2 … 0.3 mm conductor. Both of the windings must have very good insulation from each other.
Regarding this high voltage converter, please remember:
Each circuit consumes avout 50 mA without the load and 350 mA with a 2 … 3 W load. T2 and T3 transistors need good heatsinks.
Components list of the high voltage converter
R1 = 4.7K
R2 = R5 = 1K
R3 = 330
R4 = 2.7K
R6 = 60M
R7 = 300M
P1 = 500K
C1 = 10n
C2 = C4 = C5 = 100n
C3 = 1000µF
C6 = 10n / 3kV
C7 …. C12 = from tv module TVK 32
D1 = Zener 11V
D2 = D3 = BY127
D4 …. D9 = from tv module TVK 32
T1 = 2N3055
T2 = BF259
T3 = BU208
Tr1 = read the article
IC1 = 4011
IC2 = LF355