| 摘要 |
PURPOSE:To prevent radio frequency interference and bad influence exerted on an electric power supply system, by connecting a thyristor to an AC power supply terminal which is not a common electric power supply, and switching it stably and exactly. CONSTITUTION:A heater 11 serves as a temperature sensor, too. A zero crossing signal generator 13 generates an output of prescribed time width. A measuring current supplying part 14 supplies a measuring current to the heater 11 while this signal is generated. A comparator 16 compares set voltage ES of a voltage setting part 17 and voltage EM of a temperature detecting part 15, and generates an output pulse in case of EM<ES, and makes a thyristor 12 conduct. In this way, electric power of a waveform which is not changed substantially from that of an electric power supply is supplied as heater driving use. |
