Timing generator for use with multi-phase control rectifier systems

Abstract

A timing generator for use with multi-phase controlled rectifier systems is disclosed in which a ramp signal is produced in phase synchronization with the power source and compared with the value of a command signal. The command signal is indicative of the desired SCR ignition angle. A sequencing circuit, having a finite number of output states is cyclically stepped from one state to the next by a comparator. The sequencing circuit couples a source of SCR-gating pulses to the appropriate SCR in accordance with its state and with a predetermined pattern of SCR ignitions which characterize the multi-phase source. One aspect of the invention provides the multiplexing of the comparator output whereby the command signal is offset by 60.degree. (electrical) after each comparator transition to set up conditions for the next transition. A further aspect of the invention provides for the generation of an alternate ramp, 180.degree. (electrical) out of phase with the foregoing ramp, and selectively applied to the comparator during periods in which the first ramp is discontinuous. The interrelationship of the 60.degree. interval associated with the command signal offset, and the 180.degree. relationship between the two ramps is advantageously utilized in the repeated offsetting of the command signal.