GB1260967A - Improvements in or relating to triggerable pulse generators - Google Patents

Abstract

1,260,967. Transistor pulse circuits. MARCONI CO. Ltd. 3 Sept., 1970 [15 Nov., 1969], No. 56041/69. Heading H3T. A triggerable pulse generator of the kind wherein a series sequence of electronic switches SW1 ... SWn requiring "priming" are connected via a "delay device" SR to a pulse forming network PN which is energized from a D.C. supply comprises, across each of the switches, a shunt circuit so dimensioned as to provide, for its associated switch, substantially the correct "priming" current. A load, e.g. a magnetron, is connected at U. "Priming" consists in allowing a small initial current to flow through the switches, which are thyristors, before the main current. In the prior art (Fig. 1, not shown) the delay device, which is a saturable reactor SR, alone was used, but this detracted from the energy available for the main pulse. In the invention, this energy is supplied by the shunt circuits. As shown, each such circuit comprises a capacitor C and resistors R1, which determine the amplitude of the priming current, and R3, which are selected to provide correct voltage distribution across the chain of thyristors. The first and last shunt circuits also include an inductor L preferably shunted by a resistor R2, which is selected to provide correct dynamic voltage sharing; in Fig. 3 (not shown), every shunt circuit has an L and R2. Any of the elements in the shunt circuits may be adjustable. L, C and R1 constitute damped series resonant circuits, whose time constants are chosen so that a quarter cycle of oscillation occurs in the time taken for SR to saturate. In Fig. 6 (not shown) each shunt circuit comprises a pulse forming network (PNI) consisting of an inductance with distributed capacitance in series with a resistor (R0) and shunted by a further resistor (R3). Dynamic voltage sharing is provided by the pulse forming networks and the R3S control the D.C. voltage distribution. Fig. 7 (not shown) is similar to Fig. 6 but a diode is connected across each series resistor (R0). In this case the time constant of each shunt circuit is made equal to the duration of the priming current plus the main pulse. At the end of the priming pulse the pulse forming networks (PNI) reverse polarity and assist the extraction of hole charge from the thyristors.