Control pulse generator system - has programmable unijunction transistor followed by transistor amplifier, and RC timing circuit

摘要

The generator has a relaxation oscillator and is intended for two-pulse static converters with thyristors or triacs. It consists of a programmable unijunction transistor (PUT) operated by a trapezoidal DC voltage derived from an AC voltage and of an RC timing circuit with a discharge resistor used as base resistor. A voltage divider delivers a constant gate voltage determined by the supply DC voltage, and a transistor amplifier following the PUT. The relaxation oscillator (1) resistances of the charging resistor (12, 12') of the RC circuit (11, 12) and of the discharge resistor (13) serving as the PUT (10) base resistor are so low, that the transistor amplifier (2) is controlled by the PUT until the AC Voltage next zero crossing.