Transformerless high-voltage nanosecond pulse generator

2026-06-16

Transformerless high-voltage nanosecond pulse generator. In , various variants of a nanosecond pulse generator based on the Belkin design were discussed. The highest and most stable parameters were achieved with a transformer-based design, but manufacturing a pulse transformer requires a certain amount of experience and precision. . This article discusses a transformerless version of the device. Despite its simpler design, it produces pulses with amplitudes up to several kilovolts and durations on the order of nanoseconds. . A distinctive feature of this design is the use of distributed inductance—an element that can be easily fabricated from readily available materials in just a few minutes. As will be shown below, its use significantly improves the output pulse parameters and enables results that are difficult to achieve in similar circuits without additional circuit design solutions. . For reproducing the design, the exact values of all components and a verified printed circuit board are provided. This allows for assembly with virtually no component selection and minimizes setup. . The resulting output pulse parameters are:

with a 0 kOhm load — amplitude of 0 kV and 0 kV , rise time of 0 ns, fall time of 0 ns, duration of 0 ns;
with a 0 Ohm load — amplitude of 0 kV and 0 kV , rise time of 0 ns, fall time of 0 ns, duration of 0 ns.

. The pulse repetition rate can reach 0 kHz or more. . Device Circuitry. The circuit design is a development of the generator discussed in the . The basic operating principle remains the same, but an additional element has been introduced into the circuit: distributed inductor L0, which significantly affects the shape and parameters of the output pulse. . Coil L0 is a key element of the circuit. Its design determines the output pulse amplitude, rise and fall times, and the level of parasitic oscillations. Formally, L0, together with the storage capacitor C0, can be considered a series resonant circuit; however, this representation does not fully capture the processes occurring in the circuit. . In this case, C0 acts as a storage capacitor, and L0 acts as a distributed inductor, similar in properties to a short section of a long line. At one end, connected to the drain of transistor Q0, the pulse amplitude is minimal, while at the opposite end, a maximum voltage is generated, reaching the device's output. . Thus, L0 performs several functions at once: it prevents the high-voltage pulse from passing back into the circuit, participates in the formation of the leading edge, and further increases the amplitude of the output signal. The device is still operational without this inductor, but the pulse parameters are noticeably degraded. .

Compared to the previous version of the circuit, the ratings of several elements were also refined and some components were replaced. This improved the device's operational stability and improved the output pulse quality. . Figures 3–5 show output pulse waveforms for loads of 0 kOhm and 0 Ohm . Changing the load resistance significantly affects both the pulse amplitude and its timing, which is due to changes in the discharge mode of the storage capacitor and the matching conditions of the output circuit. . All waveforms were obtained with the output stage supply voltage set to 0 V. .

Please note that the measured pulse width, rise and fall times are limited by the bandwidth of the measuring path used. Measurements were performed with a oscilloscope in conjunction with a 0:100 high-voltage probe rated for voltages up to 0 kV. . The oscilloscope's rated rise time is approximately 0 ns. The high-voltage probe used has comparable characteristics. As a result, the total rise time of the measuring path is several nanoseconds, which prevents the reliable recording of faster transient processes. . For this reason, the actual rise and fall times of the output pulses can be much better: shorter than the measured values, and the edge shapes are steeper than shown in the provided oscillograms. . Component Base. One of the most important components of the circuit is the power switch Q0. The best results were obtained using the transistor. At pulse repetition rates up to 0 kHz, an additional heatsink is generally not required. At higher frequencies, a small heat sink is recommended. . The DHV diode has a significant impact on the output pulse parameters. During experiments, the 0 diode showed the best results, providing maximum pulse amplitude and minimal rise and fall times. . Another important element of the circuit is TI0, a saturable inductor. The magnetic core is a nanocrystalline size 0 , which has high magnetic permeability and a short magnetization reversal time. . The winding contains 0 turns and should be made of wire with minimal high-frequency losses. Litz wire is preferred. The wire cross-section is selected to maximize the fill of the magnetic circuit's internal window, reducing the winding's active resistance and parasitic high-frequency losses. . The design uses 0-strand Litz wire with a diameter of 0 mm, with a total cross-section of approximately 0 mm². However, no noticeable heating of the inductor is observed up to a pulse repetition rate of at least 0 kHz. . Distributed inductor L0 is made from a piece of copper wire approximately 0 cm long and 0.7–0.8 mm in diameter. The winding is performed on a 0 mm diameter mandrel, resulting in a coil of approximately 0 turns. . After winding, the coil must be uniformly stretched to approximately double its original length, so that the distance between adjacent turns is close to the wire diameter. This design reduces interturn capacitance and ensures the required distributed inductance characteristics. The inductance of the finished coil should be in the range of 0.1–0.15 µH. . List of other circuit components:

U0 -- two amplifiers in one housing ;
D0 -- suppressor ;
D0, D0 -- diodes ;
D0 -- suppressor ;
C0-C0 -- film rated at 50V;
C0 -- capacitor with a capacitance of 0-2.2 μF, MKP, rated at 275V , ;
C0 -- ceramic capacitor rated at 3kV , , another ;
R0-R0 -- any with a power of 0 watts or more.

. Pay attention to capacitor C0. It should be an SMD element with a capacitance of 0 to 0 uF, with a minimum operating voltage of 500Volt. The designed printed circuit board uses a 0 size. . . Printed Circuit Board. When designing the printed circuit board, the device's operating characteristics with high-voltage nanosecond pulses were taken into account. Particular attention was paid to minimizing parasitic inductance in the current loops, reducing the length of critical connections, and ensuring the necessary insulation distances between high-voltage sections of the circuit. . Below is the final version of the printed circuit board, obtained after several iterations of refinement and testing. The circuit diagram of the device remains unchanged. .

Production version: PCB (open)

The production option provides a set of documentation for manufacturing a printed circuit board in production: GERBER file for PCB, BOM file of the specification of components and a schematic diagram showing the values of the elements. All this allows you to immediately order a PCB, for example, here, and then quickly assemble it.

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For experimentation and power switch selection, a three-pin KF0-5.08-3P connector can be installed on the board instead of transistor Q0. . Setup. Before initial power-up, the R0 trimmer should be set to its minimum resistance position . The oscilloscope is connected in parallel with the load resistor R0. After this, an external trigger pulse generator is connected to the driver input and power is applied. . Setup consists of selecting the resistance of resistor R0, which determines the operating mode of saturable inductor TI0. While smoothly varying the resistance of R0, monitor the shape and amplitude of the output pulse on an oscilloscope. . The optimal setting is one that achieves maximum output pulse amplitude while maintaining a stable signal shape without a noticeable increase in parasitic spikes and oscillations. Once this mode is found, the device setup is complete. .

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