GB792394A - Improvements in or relating to methods and circuits for initiating electric discharges - Google Patents

Abstract

792,394. Converting. SIEMENS SCHUCKERTWERKE AKT.-GES. April 16, 1956 [April 15, 1955; July 22, 1955; July 26, 1955], No. 11561/56. Class 38 (2). [Also in Group XL (c)] In an electric discharge vessel St, the discharges are initiated by application to the control electrode of a train of pulses obtained by differentiating the pulse train output of at least one semi-conductor triode acted upon by control alternating voltage of the same frequency as that applied to the main electrodes of the discharge vessel. The alternating voltage UTr added to a direct voltage Ur (Fig. 2a) is applied to the emitter-collector circuit of transistor T, between the emitter and base of which is connected direct voltage source Ge so that the emitter-collector current rapidly changes from zero to saturation and back again each cycle (Fig. 2b). These rapid changes of current in the primary winding of transformer W, produce voltage pulses (Fig. 2c) in the secondary winding which are applied to grid of valve St, biased by voltage Sp. The instants at which the pulses occur may be varied by altering the value of voltage Ur or the phase of the A.C. supply. In a modification the added alternating and direct voltages are applied between the base and emitter of a transistor, the current through the pulse transformer connected in series with a source of direct voltage between the collector and emitter being controlled by a second transistor which operates between zero current and saturation, Fig. 3 (not shown). The second transistor may alternatively be connected in the input to the first transistor to control the baseemitter current and thereby the collector current of the first transistor, Fig. 5 (not shown). In the modification of Fig. 6 the sum of alternating and direct voltages is applied to the base of transistor Ti through a current 'limiting transistor Te. The rectangular voltage is derived through capacitor Cd from the terminals of a resistor Rd connected in series with a D.C. source Ga, across the collector and emitter of transistor Ti. The collector Ic jumps rapidly between relatively low and high values corresponding to points A and B on the Ic, Uc characteristics shown in Fig. 7. The family of curves show the characteristics for different values of base current Ib, line AB, determined by the value of Rd being followed as Ib changes. Both points A, B lie below the permissible loss hyperbola Nc. The input voltage may be limited by the arrangement of resistor Rb and rectifiers HG. The ignition voltages may be amplified and supplied to the control grids. through a further transformer.