Silicon-controlled rectifier D-C to D-C power converters

The operation of a d-c chopper circuit using a silicon-controlled rectifier (SCR) is analyzed. A description is given of a saturating reactor (SR) and capacitor which is used to extend the conducting interval of the controlled rectifier and then turn it off. Some useful variations of the basic circuit also are presented. Emphasis is placed upon the waveforms produced, and typical oscillograms are shown. The specific circuits analyzed employ a variable repetition frequency to control load voltage, but the modifications necessary for operation at a fixed frequency with variable “on” time are also mentioned.