Switching DC-DC converters are designed to both increase and decrease voltage. With their help, you can convert 5 volts with minimal losses, for example, to 12, or 24, or vice versa. There are also high-voltage DC-DC converters, they are able to obtain a very significant potential difference of hundreds of volts from a relatively low voltage (5-12 volts). In this article, we consider the assembly of just such a converter, the output voltage of which can be regulated within 60-250 volts.
Converter circuit
It is based on the common NE555 integrated timer. Q1 on the diagram is a field-effect transistor, you can use IRF630, IRF730, IRF740 or any others designed to work with voltages above 300 volts. Q2 is a low-power bipolar transistor, you can safely set BC547, BC337, KT315, 2SC828. The inductor L1 must have an inductance of 100 μH, however, if this is not at hand, you can put inductors in the range of 50-150 μH, this will not affect the operation of the circuit. It is easy to make a choke yourself - to wind 50-100 turns of copper wire on a ferrite ring. D1 diode according to the FR105 scheme, instead of it you can put UF4007 or any other high-speed diode for a voltage of at least 300 volts. Capacitor C4 must be high-voltage, at least 250 volts, as much as possible. The larger its capacity, the better. It is also desirable to put a film capacitor of small capacity in parallel with it for high-quality filtering of high-frequency interference at the output of the converter. VR1 is a tuning resistor with which the output voltage is regulated. The minimum supply voltage of the circuit is 5 volts, the most optimal is 9-12 volts.
Transducer Fabrication
The circuit is assembled on a printed circuit board measuring 65x25 mm, a file with a picture of the circuit board is attached to the article. You can take textolite larger than the picture itself, so that at the edges there is room for mounting the board in the case. A few photos of the manufacturing process:
After etching, the board must be tinned and checked for track closure. Because there is high voltage on the board, there should not be any metal burrs between the tracks, otherwise a breakdown is possible. First of all, small parts are soldered to the board - resistors, diode, capacitors. Then a microcircuit (it is better to install it in a socket), transistors, a tuning resistor, a choke. For the convenience of connecting wires to the board, I recommend installing screw terminal blocks; there are places for them on the board.
Download board:
[17.27 Kb] (downloads: 230)
First launch and setup
Before starting, you must definitely check the correct installation, ring the tracks. Set the trimming resistor to the minimum position (the slider should be on the side of the resistor R4). After that, you can apply voltage to the board by turning on the ammeter in series with it. At idle, the current consumption of the circuit should not exceed 50 mA. If it fits into the norm, you can gently rotate the tuning resistor, controlling the output voltage. If everything is normal, connect a load to the high-voltage output, for example, a 10-20 kOhm resistor and once again test the operation of the circuit, already under load.
The maximum current that such a converter can produce is approximately 10-15 mA. You can use it, for example, as part of a lamp technique for powering the anodes of lamps, or you can light up gas-discharge or luminescent indicators. The main application is a miniature stun gun, because the voltage of 250 volts at the output is palpable to humans. Have a nice build!
The operation of the converter is clearly demonstrated in the video:
