READ-ONLY Memory (ROM) Trigger Generator for Phase-Controlled Cycloconverters

A trigger generator has been developed that employs READ-ONLY memories (ROM's) and operates with a new approach to the problem of controlling the firing delay angle of cycloconverter SCR's. The circuit centers around a ROM which is addressed by two counters, one of which is cycled in synchronism with the cycloconverter source voltage and the other in synchronism with the cycloconverter output voltage. Then, for every address state, the memory directly specifies which SCR gates are to be triggered. This approach eliminates many analog circuits and results in a smaller, lower cost package that is geared toward high volume use and low maintenance. Also presented is a method for substantially reducing the memory requirements for the case of a 3ϕ-3ϕ4 cycloconverter.