On the Internet there are a lot of high voltage supplies schematics
powered from 12V, 24V or 30V. To bring something new, I developed a high voltage power supply
operated directly from the mains that works with the rectified line voltage, ie 325V dc.
The advantage of this supply is especially the relatively large output short current
about 50mA and power to hundreds of watts. Supply is current limited and can operate continuously
in short circuit, and therefore can be useful for power Tesla coil
(Power compares to a small neon transformer), various amateur gas
and air lasers, and many other more or less dangerous devices.
It is a simple self-oscillating switching power supply (SMPS). As a switching element
used here is a BJT transistor designed for line deflection (called HOT), which has allowed
voltage UCE 1500V. Suitable are for example BU2520AF, BU508AF, BU2525AF, BU2527AF, BU2532AF and some 2SC series transistors.
Component values are not critical and drawer parts can be used.
The electrolyte may have a smaller capacity. 470R resistor and 220n capacitor determine the
output current. Reducing their values rise the current and vice versa. I do not recommend
to go under 330R and 100n. Current depends on the air gap transformer cores, but I
recommend you to leave it in its original condition, or only slightly increased by one more piece of
paper on each side. Output voltage is directly proportional to the voltage of zener diode,
can be increased by reducing the number of turns of auxiliary winding from 7 to 6, in the extreme case 5 turns.
22n capacitor determines the operating frequency and its value should be adjusted to
most current (brightest arc). You can use any fast
diode least 60V and 1A instead od BA159. With a spike absorbing element 2n2 and 47R I recommend not to experiment,
otherwise the transistor can be destroyed by voltage spikes. Transistor type should be
without built-in resistor between B and E. If this resistor is built in, you have to find either
other transistor, or change the resistance of 22k/4W to 100k/10W. Zener diode must be rated
at least 1.3W. This supply,
when properly selected values of components and air gaps in the core, can give
hundreds of watts, just all depends on what survives and the secondary diode inside the transformer.
Mentioned transformer is obviously HV transformer from TV or monitor that
has a built-in diode or cascade. Older transformers without diodes can
of course, use an external diode. Transformer intended to operate with multiplier is not well suited, it has lower secondary voltage.
When using an older transformer will be used only secondary, primary is rewound. For newer transformer having windings embedded in any one
part of the wound only the auxiliary winding (about 7z) on the exposed portion of the core and as
main primary winding uses the original primary. In any case, it is
necessary to keep the polarity of the windings marked in the schematic diagram below.
When you first turn on power put 100-200W incadescent bulb into series. In bad wiring this may not
prevent the destruction of the transistor, but the possible destruction won't be such an explosive manner
and also rescued more parts :). After a successful test of short-proof (and idiot-proof)
the light bulb can be omitted.
