GB1107365A - Improvements relating to electrical sawtooth waveform generators - Google Patents

Abstract

1,107,365. Sawtooth circuits. ASSOCIATED ELECTRICAL INDUSTRIES Ltd. 27 Oct., 1964 [22 Nov., 1963], No. 46257/63. Heading H3P. [Also in Division H2] A sawtooth generator comprises a capacitor C1 charged from a D.C. source and discharged via a rectifier D2 during alternate half-cycles of an alternating voltage, a further rectifier D1 being arranged to clamp the potential across the capacitor during the discharging half-cycle. A further alternating voltage fed via transformer T2 and phase-displaced relative to that fed via T1 may be included to allow the duration of the linear sweep of the sawtooth to be greater than one half-cycle of the alternating input. The sweep duration is adjustable by relative variation of resistors R1, R3 or of the voltages at A and C. The charging current via R2 may be linearized by a known bootstrap circuit (Fig. 3, not shown). Fig. 6 (not shown) relates to six circuits of the type shown in Fig. 4 arranged to generate a six-phase sawtooth wave suitable for triggering the six main rectifiers of a three-phase grid-controlled rectifier system. Strobing circuits may be interposed between the sawtooth circuits and the rectifiers so that the firing angle of all rectifiers may be simultaneously adjustable.