The generator voltage pulses on a single mosfet transistor
This generator can work both in pulse, and in a resonant mode. In the first case, it creates high voltage pulses and high-power pulse magnetic field, orders of magnitude more than that which could be obtained in a resonant mode and equal to the required capacity. The second generator operates with resonance of the second kind, which has a number of interesting properties, aspects of which have only begun to be studied. It can work with almost any inductance from classical and bifilar coils to coaxial cables.
This generator can be received if to include a mosfet transistor according to the diagram in the following figure. Her work is pretty simple. With a chain R1ZD1 in this scheme specifies the offset on the gate of the transistor VT1, and the positive feedback that is responsible for output parameters is formed by a ferrite ring L1 in the form of blocking pulses. The generator does not operate in quite the normal blocking: if instead of mosfet-transistor connected to the IGBT, then any offset and adjust other parameters of the scheme, it will not work, although the circuit design difference between them is almost there. Chain R2C2 is used for negative feedback, which is responsible for the stability of the generator and its temperature regime (figure a). To the generator terminals XS1 and XS2 connected inductive load (figures b and c), characteristics of which depends on the pulse length and amplitude.
The dependence was quite simple: the more inductance and internal capacitance of the transistor, the greater the pulse duration, and the longer line (length of wire or coaxial cable), the higher the output amplitude of the generator. Its value is limited only by the maximum voltage of the transistor VT1, and in the case of coaxial cable is its length. Thus, in pulse mode, this generator can unleash the potential of a long line.
If parallel inductive load, connect a capacitor, then, selecting its capacity, the generator can output for a mode of resonance of the second kind. In this case, the amplitude of the output pulses will be smaller and depend on the quality of the oscillatory circuit, and their duration is determined from the resonance conditions.
As a current transformer L1 to take two ferrite rings K10x6x4 permeability 10000-2000 HM, you put them together, and wound them insulated copper wire diameter 0.1-0.3 mm. Coils wound in a single layer to fill. The ring remains in the lumen into which is threaded a conductor extending from the positive supply to the XS2. By the way, the rings may be of other sizes, but the smaller they are, the less and the recovery time domain, which has a positive effect on the output parameters of the generator.
For a list of other elements of the scheme:
As a replacement VT1 can offer IRFP460 or IRFPG50, but the output parameters of the generator will be a little worse. In addition, these transistors do not have protection on entrance, so between the gate and the source will need to connect the suppressor 1.5KE18CA. When choosing VT1 should be based on such conditions: the maximum voltage must be as high as possible, feed-through capacity and recovery time of transition — as less as possible. Also, between the gate and source of the desirable built-in protection. The transistor must be installed on a small heatsink.
Setup generator is reduced to the proper phasing of the current transformer L1. For this, the generator terminals XS1 and XS2 connected resistor 100 Ohm and the oscilloscope and the circuit is fed 15V voltage. On the oscilloscope should appear impulses. If not, then the conclusions of L1 should be reversed.
Different types of load
The type of load depend on how the output and input parameters of the generator. So, if the inductance of the load and the length of the line will be small, at the same supply voltage, input mosoti will be great. With this inductance should avoid large stresses. If the inductance is large, the voltage of the generator can be increased. And if the long coax, it may be the maximum — 40V.
The following graphic depicts the waveforms at the drain of transistor VT1 (left) and on the findings of a braid of the coaxial cable (right), at generator switching scheme C. cable Length in this case was 100m. This option can be used for excitation of magnetic materials or fields of static charge. With voltage in 35V, power consumption of the generator in this case is only a few watts and a pulse duration of less than 1mks.
Coaxial cable a small length (about 10-15m) allows you to obtain short pulses of about 100 NS, but to achieve large output amplitudes will have to increase voltage, which would entail an increase in total power consumption. More optimal, for this generator, it is a longer wire.
The following figure gives more high-voltage version of the generator and the oscilloscope at the output of the secondary winding. Here the load applied miniature high-voltage transformer TV1. It consists of two primary windings that need to be connected in series, and a secondary high voltage, which can be connected to various devices such as a discharger. Change of supply voltage from 11 to 22V can be adjusted the output voltage of the secondary winding from 3 to 15 kW, the power consumption in the whole range does not exceed 2W. By the way, if XS1 and XS4 connect a capacitor 2200-6800 pF, the terminals of the secondary windings will be a pure sine wave. However in this case the maximum voltage is better to be reduced to 15V.
The generator outputs can also be connected inductors, transformers and some non-standard inductor, for example, bifilar coil. Their parameters will depend on the output characteristics of the generator: amplitude, pulse width and frequency.