Options for the power supply of the Chizhevsky chandelier. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Electronics in medicine

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In the February issue of the magazine, the editorial staff turned to readers with a request to send their own versions of circuit solutions for the Chizhevsky Chandelier power supply. The author of the published article was one of the first to respond to this request, offering several options for such blocks. And among them is a power supply using an industrial television voltage multiplier. By the way, A. Mikhailovsky from St. Petersburg used the same option in his design - he told the editors about this.

It is known that the constant voltage of negative polarity on the "chandelier" should be at least 25 kV, but in practice at home it is desirable to supply a voltage of about 30 kV to the "chandelier". Based on these figures, the proposed power supplies were developed.

The diagram of the first version of the power supply is shown in fig. 1. The mains voltage supplied through the XP1 plug and the SA1 switch is supplied to a bridge rectifier made on VD1-VD4 diodes. The rectified voltage is filtered by capacitor C1. As a result, there is a constant voltage of about 300 V on this capacitor, which is used to power a relaxation oscillator made up of elements R3, C2, VS1, VS2.

Generator load - winding I of transformer T1. From its winding II, pulses with an amplitude of approximately 5 kV and a repetition rate of 800 Hz are fed to a voltage multiplier assembled on diodes VD5-VD10 and capacitors C3-C8. The constant voltage of about 30 kV obtained at the output of the multiplier is fed through the current-limiting resistor R4 to the "chandelier".

Fig.1 (click to enlarge)

Table 1

Neon lamp HL1 - power supply indicator. Resistor R1 limits the inrush currents that are inevitable when charging capacitor C1. Fuses FU1 and FU2 are triggered when the elements of the rectifier or high-voltage voltage multiplier fail.

Transformer T1 - a converted horizontal transformer from a black and white TV. Its high-voltage winding II is left, the rest are removed and winding I is wound instead of them - 24 turns of PEV wire with a diameter of 0,5 ... 0,8 mm. For this option, almost any horizontal transformer is suitable, since the data of their secondary windings differ slightly (for some of them they are shown in Table 1). In addition, the output voltage of the unit, if necessary, can be increased by adding another multiplication stage. The bottom output of the winding II according to the diagram is its beginning, the output is located closer to the magnetic circuit.

Dinistors VS1, VS2 - KN102 series or outdated D228. Based on the information given in table. 2, include in series as many dinistors as a total turn-on voltage of about 200 V can provide. Capacitors C3-C8 - PSO, KOB or others with a capacity of at least 100 pF for a rated voltage of at least 10 kV; C1, C2 - for a voltage of at least 400 V. Instead of the diodes VD1-VD4 indicated in the diagram, they can be D237B, D237V, KD105B, KD105V.

When mounting the high-voltage part of the unit, it is desirable to provide for the multiplier to be filled with a compound with a high resistivity, for example, paraffin. In this regard, it seems promising to use a ready-made multiplier

Table 2

UN 8,5 / 25-1,2, used in color TVs. True, on a TV it is designed to receive a positive voltage supplied to the kinescope anode, but we need a negative voltage to power the "chandelier".

Ris.2

To "turn" the multiplier, it is enough to make one more conclusion in it - D (Fig. 2) by carefully drilling and sawing off the compound to provide access to the desired point of the internal mounting of the multiplier. To do this, the multiplier is positioned so that you have an inverted designation of the type and conclusions (the slot for mounting the multiplier on the board will be on the right), then the arrangement of the elements in the compound will correspond to their location on the given circuit diagram. Two horizontal protrusions along the edges of the multiplier are the locations of the capacitors, and the point D of interest to us is located at the left edge of the upper protrusion.

If only a modified multiplier is used, its output voltage will not exceed 25 kV. Therefore, one more stage will have to be added to the multiplier on the VD7 diode and capacitor C5.

The ratings of capacitors C3 and C4 (types K15-U1, K15-4, K15-13, K73-13) correspond to those in the multiplier.

Fig.3 (click to enlarge)

A diagram of another version of the power supply is shown in fig. 3. The relaxation generator in it is made on the elements R1, VD1, C1, HL1, VS1. It works with positive half-cycles of the mains voltage, when the capacitor C1 is charged to the turn-on voltage of the analog of the dinistor on the neon lamp HL1 and the trinistor VS1. The VD2 diode dampens the self-induction pulses of the primary winding of the step-up transformer T1 and allows you to increase the output voltage of the power supply. With three multiplication stages shown in the diagram, the output voltage reaches 26 kV. A neon lamp is not only an element of an analogue of a dinistor, but also a signaling device for connecting the unit to the network.

The high-voltage transformer is self-made, it is wound on a segment of a rod with a diameter of 8 and a length of 60 mm from M400NN ferrite. First, the primary winding is wound - 30 turns of PELSHO 0,38 wire, and then the secondary - 5500 turns of PELSHO 0,05 or larger diameter. Between the windings and every 800 ... 1000 turns of the secondary winding, an insulation layer is laid from a conventional PVC insulating tape.

In any of the described blocks, it is possible to introduce a discrete (and, if desired, smooth) multi-stage adjustment of the output voltage by switching the analogues of dinistors connected in a series circuit (Fig. 3,6) or dinistors (Fig. 3, c). In the first variant, two stages of regulation are provided, in the second - up to ten (when using KN102A dinistors with a switching voltage of 20V).

As a high-voltage wire connecting the power supply to the "chandelier", the author used a television antenna cable of the Republic of Kazakhstan with a diameter of 8 mm with the outer insulation and shielding braid removed. AT

Author: V. Utin, Shchelkovo, Moscow Region; Publication: N. Bolshakov, rf.atnn.ru

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