High Voltage DC-DC Converter on NE555

Switching DC-DC converters are designed for both increasing and decreasing 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 capable of obtaining a very significant potential difference of hundreds of volts from a relatively low voltage (5-12 volts). In this article, we will consider the assembly of just such a converter, the output voltage of which can be adjusted within 60-250 volts.

Converter circuit

It is based on the common NE555 integral timer. Q1 in 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 put BC547, BC337, KT315, 2SC828. The L1 inductor should have an inductance of 100 μH, however, if this is not at hand, you can put chokes in the range of 50-150 μH, this will not affect the operation of the circuit. It is easy to make a choke yourself - wind 50-100 turns of copper wire on a ferrite ring. Diode D1 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 advisable to put a small-capacity film capacitor in parallel with it for high-quality filtering of high-frequency interference at the output of the converter. VR1 is a trimming resistor that adjusts the output voltage. The minimum supply voltage for the circuit is 5 volts, the most optimal is 9-12 volts.

Manufacturing process

The circuit is assembled on a printed circuit board with dimensions of 65x25 mm, a file with a picture of the board is attached to the article. You can take a textolite larger than the drawing itself, so that there is room at the edges for fixing the board in the case. Several photos of the manufacturing process:

After etching, the board must be tinned and checked for a short circuit. Because there is a high voltage on the board, there should be no metal burrs between the tracks, otherwise 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 trimmer, 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.

First launch and setup

Before starting, be sure to check the correct installation, ring the tracks. Set the trimmer to the minimum position (the slider must be on the side of the resistor R4). After that, you can apply voltage to the board by connecting an ammeter in series with it. At idle, the current consumption of the circuit should not exceed 50 mA. If it is within the normal range, you can gently turn the trimmer to control the output voltage. If everything is fine, connect a load to the high-voltage output, for example, a 10-20 kOhm resistor, and test the operation of the circuit again, already under load.

The maximum current that such a converter can provide is approximately 10-15 mA. It can be used, for example, as part of lamp technology to power the anodes of lamps, or to light gas-discharge or luminescent indicators. The main application is a miniature stun gun, because the output voltage of 250 volts is palpable to humans. Happy build!